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Design Engineering

2006;():1-6. doi:10.1115/IMECE2006-13273.

This paper presents a new sliding mode adaptive controller for MEMS z-axis gyroscope. The proposed adaptive sliding mode control algorithm can on-line estimate the component of the angular velocity vector, which is orthogonal to the plane of oscillation of the gyroscope (the z-axis) and the linear damping and stiffness model coefficients. The stability of the closed-loop system can be guaranteed with the proposed control strategy. The numerical simulation for MEMS Gyroscope is investigated to verify the effectiveness of the proposed adaptive sliding mode control scheme. It is shown that the proposed adaptive sliding mode control scheme offers several advantages such as on-line estimation of gyroscope parameters including angular rate and large robustness to parameter variations and external disturbance.

Commentary by Dr. Valentin Fuster
2006;():7-11. doi:10.1115/IMECE2006-13931.

The quality factor of MEMS-based microresonators is often limited due to damping of the resonator structure and the surrounding air. A possible avenue to enhance the quality factor is to incorporate a negative damping feedback to reduce the damping of the resonator for those vibration modes of interest. This method is particularly easy to implement for piezoelectric based microresonators, because piezoelectric materials can serve as a sensor and an actuator simultaneously. This paper first demonstrates the concept on a silicon cantilever with a PZT thin-film actuator and a laser Doppler vibrometer as an external sensing element. Then the paper describes a design of PZT thin-film actuator consisting of a diaphragm suspension and multiple electrodes. Some of the electrodes serve as the sensors and others as actuators to reduce resonator damping. This design can potentially be used for microresonators without using external sensing elements.

Commentary by Dr. Valentin Fuster
2006;():13-20. doi:10.1115/IMECE2006-14141.

Separation of biologically active molecules (BAMs) is a problem for the pharmaceutical and biotechnology industries. Current technologies addressing this problem require too many techniques, toxic additives, and time to filter the desired materials. As a result, a new technology is needed. The objective of this work is to contribute to the development of a device that can separate 0.5 nm to 500 nm sized BAMs. A diaphragm valve is proposed that can control a gap created by two parallel flat surfaces. Position control is achieved by means of a piezoelectric actuator and a capacitive sensor. Modularity was also part of design considerations to address issues of eventual biocompatibility breakdown. Preliminary experiments indicate that gap separation can be controlled to increments of 0.2 nm.

Commentary by Dr. Valentin Fuster
2006;():21-26. doi:10.1115/IMECE2006-14175.

The Piezo-driven actuator is widely used as one critical part in the micromanipulation system for routine reproductive experiments such as Intracytoplasmic Sperm Injection (ICSI). The actuator can induce the fast mechanical motion on the pipette tip, which greatly facilitates the microinjection processes. It is of rather importance to choose the appropriate system parameters applied to the actuator. In our paper, we propose a mechanical model of the Piezo-driven actuator. We analyze the longitudinal micro-dynamic characteristics of Piezo-driven pipettes. The transient response of the pipette tip is obtained by numerical methods. We also study the effects of the excitation signals on the dynamics of the tip. The related experimental validation is conducted for our simulation results.

Commentary by Dr. Valentin Fuster
2006;():27-32. doi:10.1115/IMECE2006-14404.

We propose a mechanical model for a capsule containing a piezoelectric actuator. The interfacial interaction between the capsule and a surface is assumed to be viscous. Nonlinearity in the interfacial force such as shear thickening is assumed to be present. When periodic excitations are applied to the piezoelectric actuator, the capsule is shown to propel itself. The self-propulsion is confirmed through an experimental setup.

Topics: Propulsion
Commentary by Dr. Valentin Fuster
2006;():33-39. doi:10.1115/IMECE2006-14528.

In micromachined gyroscopes, the vibrating masses are generally coupled by one of two means. The most common means is mechanical, meaning a spring or equivalent structure links the two masses. Alternatively, the coupling is produced electrostatically, where the displacement of the masses causes the gap of a capacitive structure to vary. In this paper, a new approach called electronic coupling is employed. The tuning structure and circuit are presented. Simulation results are discussed.

Commentary by Dr. Valentin Fuster
2006;():41-46. doi:10.1115/IMECE2006-14625.

A novel optically powered microactuator is developed via the integration of a thin film piezoelectric microactuator with a micro-solar cell on the same chip. The integrated microactuator has an overall area of 2×2 mm2 and is less than 0.25 mm in thickness. The paper presents the details of fabrication and preliminary experimental results confirming the optical actuation. The solar cell is fabricated by doping a n-type dopant in a p-type silicon wafer. The thin film piezoelectric microactuator is fabricated alongside the solar cell via the solgel method. The microactuator prototypes are tested for optical actuation under low light intensities in the range 0.1-1.26 W/m2 , and corresponding center point displacements of the actuators and the photovoltages output by the solar cells are measured. An unpoled microactuator prototype produced a maximum displacement of 31 nm corresponding to an input light intensity 1.26 W/m2 .

Commentary by Dr. Valentin Fuster
2006;():47-55. doi:10.1115/IMECE2006-14746.

Attractive forces present at the micro and nano scales are a hindrance to error-free manipulation of micro-scale objects using manipulator devices as they cause the micro-scale objects to become adhered to the end-effector of the manipulator. This paper presents a dynamic model for controlled release of a polystyrene microsphere adhered to the end-effector of a compliant micromanipulator due to Van Der Waal's forces applying the principle of the inertial release technique. The inertial release is effected through step input actuation forces of the manipulator. Various actuation parameters such as the velocity and rise time for successful inertial release of adhered microspheres are investigated.

Commentary by Dr. Valentin Fuster
2006;():57-63. doi:10.1115/IMECE2006-15191.

This paper presents the design and proposed fabrication of an electromagnetic (EM) micro-actuator capable of independent force output in two orthogonal axes of motion. This actuator enables independently controlled in- and out-of-plane motion when coupled with a suitable flexure. An electromagnetic force model is presented. Simulation results indicate that the actuator can output several mNewtons per square millimeter of footprint in two orthogonal axes with electrical bandwidth greater than 1 MHz. In addition, we show that the micro-actuator may be designed to eliminate parasitic force and torque by tuning the coil geometry. A bench-level prototype nanopositioner has been designed and built with centimeter-scale prototype actuator coils and magnets. Predicted static displacement matches the measured values to within 5%. Efforts to further miniaturize the device are described, including a four-mask micro-fabrication process that is to be used to fabricate two-axis actuators for a six-axis nanopositioner. Parts of these processes have been used to create prototype micro-coils that sustain current densities greater than 1000 A/mm2 .

Topics: Microactuators
Commentary by Dr. Valentin Fuster
2006;():65-66. doi:10.1115/IMECE2006-15438.

Micro-cantilevers have recently evolved into a key sensor technology. Many of these sensors are deployed in fluid streams, for example, in rapid sensing of trace quantities of chemical or biological species in gaseous or aqueous environments[1,2], or in high resolution, high bandwidth anemometry [3]. Their design needs to consider microcantilever bending caused by the flow. This work presents detailed experimental data on the flowinduced bending of micro-cantilevers, and a simple theoretical model for quantitatively predicting such behavior.

Commentary by Dr. Valentin Fuster
2006;():67-68. doi:10.1115/IMECE2006-15479.

The Atomic Force Microscope (AFM) has become an indispensable tool in biology because it permits the probing of nanomechanical properties under physiological (liquid environments) conditions. AFM has been used in liquid environments to image, manipulate and probe atoms, living cells, bacteria, viruses, subcellular structures such as microtubules, individual proteins and DNA. Probably the most popular method used for AFM in liquids is the tapping mode wherein a resonant microcantilever is scanned over a sample. Yet very little is known about the dynamics of microcantilevers in liquid environments while interacting with nanostructures. This problem is especially challenging because viscous hydrodynamics couples strongly with cantilever motions, and the contribution from the electric double layer forces, which is not significant in air, must be taken into account. Previous attempts in the analysis and simulation of tapping mode in liquid modeled the tip-sample interaction forces using either a Lennard-Jones potential [1, 2], an exponentially growing force of small duration of the cantilever oscillation cycle [3] without any contact mechanics, or an unrealistic discontinuous interaction force [4]. Moreover, in all these papers the microcantilever was modeled by a point (lumped) mass, and the hydrodynamic effects were not derived rationally from basic hydrodynamic theory. Instead, a low quality factor (Q factor) and an added fluid mass were simply assumed [1–4]. A direct method to systematically deal with the AFM microcantilever using continuous beam theory in liquids governed by the unsteady Stokes equations and experiencing intermittent contact with the sample is not available in the literature.

Commentary by Dr. Valentin Fuster
2006;():69-73. doi:10.1115/IMECE2006-15482.

We consider the response of a continuously deformable mirror with discrete MEMS actuators. The mirror itself is described with a geometrically exact shell model incorporating both flexural and extensional strains, while the MEMS actuators are represented as discrete elements subject to a time-dependent voltage. A reduced-order model is developed through a Galerkin reduction and the resulting equations are subjected to the method of multiple scales. The response of the system is then analyzed to uncover the ability of the system follow desired mirror profiles.

Commentary by Dr. Valentin Fuster
2006;():75-81. doi:10.1115/IMECE2006-13087.

The cylindrical transmission with balls is a new type of mechanical transmission, that allows movement transmission between two coaxial shafts [1]. In the first part of this paper presents the geometric and kinematics study of the elements of cylindrical -sinusoidal transmissions with balls, determining in this way the transmission ratios. In the second part of this paper presents the geometric and kinematics study of the elements of differential cylindrical transmission with balls, determining in this way the transmission ratios. An advantage of this transmission, as compared to other mechanical transmissions, is given by the possibility to obtain more transmission ratios. In case all cylinders of simple cylindrical transmission are moving elements a differential transmission it obtained. Another advantage is given by the possibility of obtaining complex transmissions by series and/or parallel arrangement of cylindrical transmission simple units.

Commentary by Dr. Valentin Fuster
2006;():83-88. doi:10.1115/IMECE2006-13161.

The Mahalanobis Taguchi System is a diagnosis and forecasting method for multivariate data. Mahalanobis distance is a measure based on correlations between the variables and different patterns that can be identified and analyzed with respect to a base or reference group. The Mahalanobis-Taguchi System is of interest because of its reported accuracy in forecasting small, correlated data sets. This is the type of data that is encountered with consumer vehicle ratings. MTS enables a reduction in dimensionality and the ability to develop a scale based on MD values. MTS identifies a set of useful variables from the complete data set with equivalent correlation and considerably less time and data. This paper presents the application of the Mahalanobis-Taguchi System and its application to identify a reduced set of useful variables in multidimensional systems.

Commentary by Dr. Valentin Fuster
2006;():89-98. doi:10.1115/IMECE2006-13330.

This paper summarizes results of a large research program intended to develop a draft rear underride guard specification for heavy vehicles. Results of a series of laboratory and full-scale crash tests performed at the Transport Canada Research Center were used in the development of these specifications. A total of eleven full-scale crash tests was carried out to evaluate the effectiveness of different underride guards. The first ten of these tests were performed on a simulated trailer attached guard. Four different underride guard designs were used in these ten full-scale crash tests. Three different vehicle models traveling at 48, 56 and 65 km/h speeds were used to impact underride guards head on. Results of the first ten crash tests show that the currently used US FMVSS 223 standard is far from adequate in preventing the occurrance of rear underride. Based on findings obtained from these crash tests, an improved guard design was developed and tested using a 16-meter trailer. This final crash test verified the effectiveness of improved guard design in reducing the undesirable effects of rear underride crashes. Based on the results, a draft heavy vehicle rear underride guard specification was developed.

Topics: Vehicles
Commentary by Dr. Valentin Fuster
2006;():99-107. doi:10.1115/IMECE2006-13365.

In this paper two finite element analysis (FEA) quarter-vehicle models (QVMs) are constructed using developed nonlinear 3-and 4-groove tread FEA radial-ply truck tire models. In addition to the FEA models, a rigid ring QVM is developed to observe the dynamic response of the rigid ring tire model under the effect of the sprung mass vertical motions. The rigid ring tire model was created in the authors' previous studies. In the rigid ring QVM, the suspension characteristics are similar to that used in the FEA QVMs. Simulations are conducted using explicit FEA simulation software, PAM-SHOCK. The FEA tire model predictions of contact patch area, static vertical stiffness, first mode of free vertical vibration, and yaw oscillation frequency response are compared with measurements and found to be in good agreement. After the successful validation tasks, the FEA QVMs is subjected to a durability test on a 74 cm-long and 8.6 cm-deep water drainage ditch to observe the dynamic tire responses. Meanwhile, measurements are conducted using a tractor-semitrailer. The vertical acceleration of the front axle that moves vertically together with front tires is measured and compared with the results from the QVMs. The predicted vertical accelerations from the QVMs exhibit similar results in magnitude and trend to each other. However, the measured peak values are lower than those observed from the QVMs due to a dynamic coupling effect from roll and pitch motions. Reasonable agreement between predicted and measured vertical acceleration is observed at higher speeds because the dynamic coupling effect is less significant on the front axle of the tractor-semitrailer at higher speeds. In order to compare the dynamic tire responses of the QVMs with measured values, special test equipment similar to the QVM is required to obtain the actual dynamic tire responses in the same quarter-vehicle environment.

Commentary by Dr. Valentin Fuster
2006;():109-115. doi:10.1115/IMECE2006-13387.

In this paper a new theoretical model to estimate the transmitted force in a snow-chain safety device is presented. Starting with a detailed analysis of the significant external forces acting on the system, the mathematical model is developed using some basic concepts of the contact mechanics theory. A MATLAB® code was developed in order to perform numerical simulations and experimental tests were carried out to validate the model. The results obtained show that for certain conditions of the driving surface and the tire's tread the force transmitted along the chain can be several times the longitudinal traction force applied to the tire itself. The importance of the interaction between the blocks on the tire and the chain segments is discussed. Some conclusions and recommendations are made in order to improve the design process of this kind of devices.

Topics: Force , Chain , Tires
Commentary by Dr. Valentin Fuster
2006;():117-126. doi:10.1115/IMECE2006-13578.

This paper presents a detailed 4×4 off-road vehicle modelling method, based on a multi-physics approach. A full drivetrain system including all aspects of rotational inertial dynamics, friction, damping and stiffness properties is integrated with a fourteen-degrees-of-freedom vehicle model including body dynamics, kinematics, suspension and wheel dynamics as well as the terramechanical phenomena between tyres and soft soils. The interaction between all these modules is implemented in the MATLAB/SIMULINK/SimDriveline environment. The concepts of modularity, flexibility, and user-friendliness were emphasized during model development. The model is developed in order to provide design engineers with the capability to investigate effects of component selection and to develop control systems and automatic optimization processes for off-road 4×4 vehicles. While the modelling approach can be used for a wide variety of operating conditions, the present work focuses on the analysis of the contribution of different aspects on the off-road traction of 4×4 vehicles.

Commentary by Dr. Valentin Fuster
2006;():127-135. doi:10.1115/IMECE2006-13704.

Hydraulic assist power system (HAPS) is a low-cost system that converts vehicle kinetic energy during vehicle deceleration or braking into hydraulic energy and then uses it to assist vehicle propulsion. Unlike conventional hybrid electrical vehicles (HEV) or hydraulic hybrid vehicles (HHV), where a separate motor/generator or motor/pump set is required, the present concept uses the existing hydraulic pump of the transmission unit as the motor/pump set directly. This leads to reduced size, lower weight and less cost. Typical applications of HAPS include energy recovery, engine restart, and hill-holding, etc.

Commentary by Dr. Valentin Fuster
2006;():137-146. doi:10.1115/IMECE2006-13961.

The static and dynamic properties of pitch-interconnected hydro-pneumatic vehicle suspensions are derived using a generalized analytical model. The suspensions incorporate two compact struts with integrated gas chambers and damping valves within each unit. The struts provide superior flexibility in realizing fluidic couplings, while offering large effective working area. The proposed suspension configurations consist of hydraulic, pneumatic or hybrid fluidic couplings between the front and rear suspension struts. The coupling effects due to different interconnected suspensions are established through the mathematical formulations. A generalized model of the hydro-pneumatic suspensions is developed that could be applied for either the roll or pitch plane of the vehicle, permitting analyses of suspension forces in a very simple manner. The 7-DOF pitch plane model of a heavy vehicle is analyzed to derive the relative vertical and pitch properties of different suspension configurations, in terms of suspension rates, pitch stiffness, bounce and pitch mode damping properties. The results suggest that the use of fluidic interconnections could yield considerable design flexibility and reduced coupling between the bounce and pitch stiffness properties, while the hydraulic and hybrid fluidic couplings offer added flexibility in tuning the bounce and pitch damping characteristics. The influence of load distribution on the bounce and pitch stiffness properties is also explored.

Commentary by Dr. Valentin Fuster
2006;():147-154. doi:10.1115/IMECE2006-13968.

This paper presents the development of an algorithm to estimate the tractive force of an off-road vehicle with uncertainties in the tire stiffness and in the soil moisture content. The algorithm compares the average ground pressure with the critical ground pressure to decide if the tire can be approximated as a rigid wheel, or if it should be modeled as a flexible wheel, and involves using previously developed vehicle and stochastic soil models, and computing along the way the vehicle sinkage, resistance force, tractive force and drawbar pull. The soil modeling focuses on the efficient treatment of poorly known parameters, such as the soil moisture content, and on the impact of these uncertainties on relationships critical in defining the mobility of an off-road vehicle, such as the pressure-sinkage and the shear stress-shear displacement relations. The uncertainties in the tire stiffness and in the soil properties are propagated through the model, and the uncertainty in the output of the vehicle model is analyzed. Such simulations can provide the basis for the study of ride performance, handling, and mobility of the vehicle in off-road conditions. The vehicle model used has seven degrees of freedom. Each of the four suspension systems comprises of a nonlinear spring and a linear viscous damper. The analysis of the dynamic response of the vehicle is performed for two scenarios: a light cargo, and a heavy cargo.

Commentary by Dr. Valentin Fuster
2006;():155-161. doi:10.1115/IMECE2006-13971.

A seven-post test rig is an experimental device that allows the simulation/recreation of driving conditions (e.g., racing track conditions) in the controlled environment of the laboratory. In general, the vehicle models used for tuning the real vehicle are very simplified. This may lead to differences between the results obtained using the computer model and the actual vehicle behavior as measured when mounted on the seven post test rig. This paper presents an effort to create a virtual seven post model to analyze the difference between the actual laboratory tests and the virtual model with the simplified vehicle models. A simplified full-car model is mounted on the virtual seven post rig with the ideal road input and the ideal parameters. Data from the simulation is meant to be compared with the actual experimental data from the rig to provide insight into tuning the suspension of the vehicle to optimize the tire force generation and vehicle handling. Moreover, a virtual seven post rig will allow researchers to run simulations of tuned vehicles or develop control policies for suspension system prior to performing the tests on the actual rig. The virtual rig will actually save development time and eliminate dangerous scenarios, and reduce the possibility of damaging the rig.

Commentary by Dr. Valentin Fuster
2006;():163-175. doi:10.1115/IMECE2006-14059.

A continuously variable transmission (CVT) is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. The present research focuses on developing models to understand the influence of clearance on the dynamic performance of a chain CVT drive. Clearances may arise in such a CVT during the assembly process or during extensive continual operation of the system, which further leads to wear and failure of the system. A detailed planar multibody model of a chain CVT is developed in order to accurately capture the dynamics characterized by the discrete structure of the chain, which causes polygonal excitations in the system. A suitable model for clearance between the chain links is embedded into this multibody model of the chain CVT. Friction between the chain link and the pulley sheaves is modeled using continuous Coulomb approximation theory. The mathematical models, the computational scheme, and the results corresponding to different loading scenarios are discussed. The results discuss the influence of clearance parameters on the dynamic performance, the axial force requirements, and the torque transmitting capacity of a chain CVT drive.

Commentary by Dr. Valentin Fuster
2006;():177-183. doi:10.1115/IMECE2006-14146.

Mining injury statistics show that a significant number of back, neck, and head injuries are linked to exposure from vehicle vibration. Use of a suspension seat is a common way to isolate the vehicle operator from the adverse effects of vibration exposure. Thus, researchers at the National Institute for Occupational Safety and Health1 - Pittsburgh Research Laboratory (NIOSH - PRL) performed laboratory studies on four passive and two semi-active seat suspension designs. These are typical of seat suspensions commonly found on large off-road heavy surface mining, construction and agricultural vehicles as either replacement or original equipment manufacturer (OEM) systems. One included a pneumatic (air bladder) spring mechanism. The fifth and sixth suspensions were a NIOSH magnetorheological (MR) semi-active damper design based on the pneumatic (air bladder) and one of the coil spring suspensions above. These suspensions were modified with a commercially available MR damper substituted for the OEM damper. These six seat suspension systems were tested and analyzed, for vertical vibration only, using the ISO 5007 Standard [1]. This paper describes the laboratory vibration tests using a MTS® shaker table and discusses the results obtained for the different suspension designs and highlights the rheonetic technology studied. Implications of the seat suspension designs relative to their capabilities for isolating vehicle operators from vibration exposure are discussed. Results for suspensions 1 through 3 showed frequencies of isolation from 2.1 to 3.0 Hz using the 40-kg (88-lb) mass and from 1.65 Hz to 1.8 Hz using the 80-kg (176-lb) mass. Suspension #4, in tests with only the 80-kg (176-lb) mass, showed an isolation frequency of 3.7 Hz. With the MR damper added to seat suspension #4, the peak transmissibility was lowered from 1.3 to 0.95 and showed a corresponding downward shift in frequency from 2.25 Hz to 1.4 Hz. In fact, the results for suspension #5 (the MR damper added to seat suspension #4), using test #3 conditions of the programmed control algorithm, showed isolation (attenuation of transmitted vibration) throughout the test frequency range from 1.0 to 6.0 Hz.

Topics: Testing , Vibration
Commentary by Dr. Valentin Fuster
2006;():185-193. doi:10.1115/IMECE2006-14751.

An existing full car dynamic model (HVOSM.VD2) was expanded previously to enable simulation of electric, hybrid electric, and fuel cell vehicles with integrated vehicle stability systems. A prototype range extending series hybrid electric vehicle was constructed with independent front wheel drives. A hybrid vehicle stability assist (VSA) algorithm was developed to perform proportional control of yaw rate through left/right distribution of front motor torques while simultaneously blending anti-lock braking and traction control with electric drive within hybrid system power limits. The new model, Hybrid Electric Vehicle Dynamic Environment, Virtual (HEVDEV), was validated and used to simulate the Hybrid VSA safety system in the prototype. Skid pad testing was performed to validate HEVDEV simulations of steady state turning behavior. Further simulations using proportional control of differential front wheel torque predicted stable Hybrid VSA performance during step-steer and braking-in-a-turn dynamic maneuvers within hybrid drive-train power limitations. This study focuses on system transient behavior during step steer inputs using more power intensive PID control algorithms, several front to rear weight distributions, and recent trends in HEV and Fuel Cell component specifications. Conclusions are made about component specifications for successful Hybrid VSA systems in future Plug-In hybrid electric (PHEV) and Fuel Cell (FCV) Vehicles.

Commentary by Dr. Valentin Fuster
2006;():195-204. doi:10.1115/IMECE2006-14804.

Simulation tools have been widely used to complement experimentation for suspension design in the automotive industry not only for reducing the development time, but also to allow the optimization of the vehicle performance. Both a test method and a simulation tool are presented for the analysis of Noise-Vibration-Harshness (NVH) performances of road vehicles suspension systems. A single suspension (corner) has been positioned on a rotating drum (2.6 m diameter) installed in the Laboratory for the Safety of Transport of the Politecnico di Milano. The suspension system is excited as the wheel passes over different cleats fixed to the working surface of the drum. The forces and the moments acting at the suspension-chassis joints are measured up to 250 Hz by means of five six-axis load cells. A mathematical representation that can accurately reflect tyre dynamic behaviour while passing over different cleats is fundamental for evaluating the suspension system quality (NVH) and for developing new suspension design and control strategies. Since the phenomenon is highly non-linear, it is rather difficult to predict the actual performance by using a physical model. However universal "black-box" models can be successfully used in the identification and control of non-linear systems. The paper deals with the simulation of the tyre/suspension dynamics by using Recurrent Neural Networks (RNN). RNN are derived from the Multi Layer Feed-forward Neural Networks (MLFNN), by adding feedback connections between output and input layers. The Neural Network (NN) has been trained with the experimental data obtained in the laboratory. The results obtained from the NN demonstrate very good agreement with the experimental results over a wide range of operation conditions. The NN model can be effectively applied as a part of vehicle system model to accurately predict elastic bushings and tyre dynamics behaviour.

Commentary by Dr. Valentin Fuster
2006;():205-210. doi:10.1115/IMECE2006-14863.

A regression-based energy method is developed for estimating the overall interior noise (dBA) and Articulation Index (AI) in the automobile passenger-compartment for engine operation at idle, 2500 rpm, and wide-open-throttle speeds. The method is developed for use in the early vehicle design stage for evaluating the effect of different vehicle and powertrain architecture designs on engine noise performance. Regression analyses from a database of standard vehicle chassis dynamometer tests are used to estimate the effect of vehicle and powertrain architectures on the acoustic energy response and resulting interior noise. Comparisons of the estimated versus measured dBA and AI responses show reasonable agreement for different powertrain types. However, the inclusion of only limited architecture details somewhat underestimates the actual response for certain engines and operating conditions.

Commentary by Dr. Valentin Fuster
2006;():211-217. doi:10.1115/IMECE2006-14913.

In recent decades, many types of hybrid vehicles have been developed to compensate for the limited sources of oil and gas production. Gasoline-electric hybrid technology shows a significant improvement in fuel efficiency for small and medium-sized passenger vehicles. However, that hybrid type is not economically beneficial for larger vehicles due to large, harmful and expensive battery packs. Hydraulic hybrid technology has been found effective for heavy duty vehicle because of its high power density. Other advantages of hydraulic hybrid are the lower cost and environmental friendliness over the electric batteries. The potential achievement in fuel efficiency has been proved in several studies and experiments by different schools, institutes and laboratories. The only problems preventing this hydraulic hybrid technology going to the market are noise and vibration involving with the hydraulic system. This study focuses on using magnetorheological (MR) technology to reduce the noise and vibration transmissibility from the hydraulic system to the vehicle body. MR technology has been well-known with automotive applications such as engine mounts, vehicle's main suspension system. In order to study the nature of the problem, structure of a hydraulic hybrid vehicle in series design is analyzed. The operational characteristics of the powertrain are carefully studied, and the vibration data is formulated. This research shows that not only MR elements play an important role in vibration suppression, but also the geometrical configurations of the mounting systems affect the efficiency in noise and vibration isolation. To this end, simulation results are also used to determine the most effective control method for the MR mounts.

Commentary by Dr. Valentin Fuster
2006;():219-228. doi:10.1115/IMECE2006-15436.

This paper presents a new method for efficiently and accurately modeling the elasto-kinematic behaviors of torsion beam suspension systems and of other similar classes of mechanical systems, and a design method utilizing the models. The torsion beam is represented as a linkage of lumped mass joined by nonlinear springs, bending and torsion, whose stiffness are identified via off-line computational experiments using nonlinear finite element simulations. A number of such computer experiments are conducted off-line for representative dimensions of torsion beams, and the results are stored in surrogate response models. During design iterations, these surrogate response models are utilized to automatically construct a lumped-compliance linkage model of a torsion beam and integrate it into a multi-body suspension system model that can be simulated using commercial software. Comparison with a nonlinear finite element analysis demonstrates much improved accuracy of the proposed model over commercial flexible multi-body simulation software, with comparable computational speed. Finally, an example is presented on the multi-objective optimization of the cross section of the torsion beam using the developed surrogate response models.

Topics: Torsion , Linkages , Design
Commentary by Dr. Valentin Fuster
2006;():229-238. doi:10.1115/IMECE2006-15437.

With a growing demand for improved fuel efficiency and reduced emissions, lightweight vehicles have gained strong attention in current automotive industry. This paper discusses the development of a brake system for a lightweight vehicle that has significant weight variations. A conventional brake system was first designed and its performance was assessed. In order to improve the brake efficiency and prevent wheel lockup under all loading cases, antilock brake system (ABS) is proposed in which a wheel slip controller based on sliding mode control and a solenoid valve actuator is modeled. In the wheel slip controller, Extended Kalman Filter (EKF) was used to monitor the brake forces and a pulse width modulation (PWM) technique was applied to control the solenoid valve. The overall brake performance was evaluated through simulation of 8 DOF nonlinear vehicle model. The proposed brake system showed significant improvement in brake efficiency.

Topics: Vehicles , Brakes
Commentary by Dr. Valentin Fuster
2006;():239-247. doi:10.1115/IMECE2006-15439.

Rollover and jack-knifing of articulated heavy trucks are serious threats for motorists. Active safety technologies have been demonstrated to have potential to reduce or prevent the occurrence of these types of accidents. The vehicle dynamic control (VDC) system utilizes differential braking to affect vehicle response and has been shown to be quite effective in controlling vehicle yaw response. A VDC system that improves the yaw and lateral motions of an articulated vehicle has been developed. For this purpose, an optimal yaw-moment control law has been designed and the optimal values of the controller gains have been determined. The results of the numerical computer simulation show that very good performance of the proposed control system could be achieved.

Topics: Stability , Vehicles
Commentary by Dr. Valentin Fuster
2006;():249-254. doi:10.1115/IMECE2006-15661.

Lightweight, compact hydrogen storage has been one of the major bottlenecks in developing fuel cell systems applicable to powering ground vehicles. In this study, preliminary experimental examinations have been performed to evaluate vibratory densification of nanometer-scale powder particles, which directly affects the volume and weight of storage systems based on complex hydrides such as NaAlH4 . Since NaAlH4 is is reactive with moisture and oxygen, and thus not possible to test in air, γ-alumina (gamma-aluminum oxide) with a similar average particle size (~50 nm) is applied as a surrogate material in this preliminary investigation. An apparatus including a tube test section to quantify the densification of a column of powder was developed for this study. Comprehensive testing has been carried out to identify the optimal vibration conditions achieving the highest densities. The study investigates the effectiveness of 1-dimensional and 2-dimensional vibration, as well as the impact of frequency patterns (constant frequency and frequency sweeping). Offering fundamental understanding of nano-powder densification using shakers, this experimental investigation provides guidelines for further study of vibration-based hydride powder densification.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2006;():255-265. doi:10.1115/IMECE2006-15786.

A key source of safety and infrastructure issues for operations of longer combination vehicles (LCVs) is off-tracking, which has been used to refer to the general phenomenon that the rear wheels of a truck do not follow the track of the front wheels and wander off the travel lane. In this paper, we examine the effectiveness of command-steering in reducing off-tracking during a 90-degree turn at low and high speeds in an articulated system with a tractor and three full trailers. In command steering, rear front axles of the trailers are steered proportionately to the articulation angle between the tractor and trailing units. We then consider several control strategies to minimize off-tracking and rearward amplification of this system. A minimum rearward amplification ratio (RWA), as a surrogate for minimum off tracking, has been used as the control criterion for medium to high speeds to arrive at an optimal Linear Quadratic Regulator (LQR) controller. As for low speeds, the maximum radial offset between the tractor and trailer 3 is minimized in the design of the controller. Robustness of the optimal controller with respect to tyre-parameter perturbations is then examined. Based on the simulation results, we find that, active command steering is very effective in reducing off tracking at low- as well as high-speed 90-degree turns. To achieve acceptable levels of RWA and off tracking, at least two of the three trailers must be actively command-steered. Among the three two-trailer-steering possibilities, actively steering trailers 1 and 2 is most cost-effective and results in the lowest RWA for medium- to high- speeds (at which RWA is important), and off-tracking is practically eliminated for all speed regimes considered.

Commentary by Dr. Valentin Fuster
2006;():267-270. doi:10.1115/IMECE2006-16132.

Application of the multiple delayed resonators in suppressing tonal vibration of a coach body is studied in this paper. The excitation arose from the random nature of the rail corrugation is modeled by harmonic and random inputs. Using a standard power spectral density (PSD), the rail surface roughness is generated by application of the Monte Carlo simulation in random space. In order to have a comparison, a tuned mass damper (TMD) system is also designed. The performances of these two controller systems i.e. TMD and DR are investigated for variety of excitations.

Commentary by Dr. Valentin Fuster
2006;():271-278. doi:10.1115/IMECE2006-16209.

The article presents the results of a large-scale design space exploration for two vehicles part of the Future Tactical Truck System (FTTS) family. A multi-objective optimization tool is presented, that allows designers to make appropriate trade-offs amongst different vehicle characteristics, on the basis of simulations run varying vehicle parameters over a broad range of values. Several powertrain architectures were taken into consideration for the Maneuver Sustainment Vehicle (MSV) and Utility Vehicle (UV). The architecture alternatives include the number of axles in the vehicle (2 or 3), the number of electric motors per axle (1 or 2), the type of internal combustion engine, the type and quantity of devices for energy storage (batteries, electrochemical capacitors or both together). A control strategy for energy management was developed to provide efficiency and performance. The control parameters are tunable and have been included into the design space exploration.

Topics: Design , Vehicles , Trucks
Commentary by Dr. Valentin Fuster
2006;():279-289. doi:10.1115/IMECE2006-13701.

Many experts agree that effective management of system reliability and reliability validation during product development is a key to achieve superior time to market and life cycle quality. However, reliability performance prediction is a common problem faced by all product developers and it is usually a difficult task. A related problem is to determine the reliability performance of a remanufactured product. Clearly, the remanufacturer would like to know the expected reliability of their product before entering it into service, but unlike an original manufacturer, they will typically have much less information available to them. In this paper, a general framework for reliability prediction in a remanufacturing environment is proposed. A case study of a remanufactured engine cylinder head that has had a fatigue crack repaired by a welding process will be presented in order to illustrate the process. The approach combines the use of Failure Modes and Effects Analysis (FMEA), Experimental Model Building, Monte Carlo Simulation and Linear Elastic Fracture Mechanics (LEFM) to generate a reliability estimate. The FMEA and physical modeling will be used to generate a model that relates the welding process control parameters to the fatigue performance of the test specimens. Monte Carlo Simulation techniques and LEFM will build on the above model to relate the process control parameters to the reliability performance. The paper concludes by discussing the utility of such a model and approach, and presents the future research agenda.

Commentary by Dr. Valentin Fuster
2006;():291-295. doi:10.1115/IMECE2006-14164.

In recent years, the demand for making a car comfortable is increasing and as a factor which governs the comfort of a car, improvement in the driving-stability is attempted. Although body rigidity, tire characteristic, aerodynamics, etc. are raised as factors affecting the design results, it is known experientially that the influence of a suspension is especially great. Therefore, the design of a suspension system becomes important for making a comfortable car. Generally, the design processes of a complicated system can be finished through three major stages, the concept design, the basic design, and the detailed design. For example, at the stage of detailed design, the design engineers have the CAD data for the manufacture, and at the same time they can develop very accurate computer simulation model from the CAD data to help them to make decision for special design factors. The basic concept of every CAE tool is to generate the analytical model by a series of discrete elements set instead of the physical parts. As a result, it becomes very difficult for the engineers to find the physical mechanism of the complicated behavior of their design from the results of numerical analysis. For the concept design processes, it is very important for the design engineers to understand the basic principle of their basic design plans and to compare with the different concepts to know which one has the highest potential to achieve the design aims. However the engineers have to accomplish these processes by only their experience. In this study, the authors proposed a new method to identify the important information which links to the basic principle of the physical behavior by using CAE technology. This method can help the engineers to grasp the basic physical characteristic that governs the first-order behavior.

Commentary by Dr. Valentin Fuster
2006;():297-305. doi:10.1115/IMECE2006-14238.

A new geometry of a cylindrical worm gear drive is proposed for: (i) reduction of sensitivity of the drive to errors of alignment, and (ii) observation of a favorable bearing contact. The basic ideas of new geometry are as follows: (i) the worm-gear is generated by a hob that is oversized in comparison with the worm of the drive and has a parabolic profile in normal section; (ii) the tooth surface of the worm of the drive is a conventional one. Due to deviation of the hob thread surface, the bearing contact of the worm and the worm-gear is localized. Reduction of sensitivity to misalignment and improved conditions of meshing are confirmed by application of TCA (Tooth Contact Analysis). Formation of bearing contact has been investigated by finite element method applied in 3D for more than one pair of contacting teeth. Developed ideas may be applied for various types of cylindrical worm gear drives.

Topics: Worm gears , Bearings , Design
Commentary by Dr. Valentin Fuster
2006;():307-313. doi:10.1115/IMECE2006-14989.

In the past decades, firms have increased automated assembly operation to improve productivity and reduce human errors; however, manual assembling is still a necessary operation for complex and large-scaled systems that require high reliability. Furthermore, since customers demand more variety in systems, firms increasingly assemble variants of a system in a single assembly line. In this mixed model assembling operation, there are higher chances of assembly errors due to interchanging of geometrically similar parts between system variants. Design for Assembly (DFA) is a design guideline that assists engineers to design systems that are easier to assemble; however, DFA does not provide any guideline for simultaneously designing variants of system being assembled in mixed model operation. Furthermore, incentive schemes for assembly operators that may influence both assembly productivity and errors have not been the scope of DFA research. In this research, the authors conducted assembling experiments with students to investigate how non-geometric part information and incentive schemes affect the assembly productivity and quality in mixed model assembling operation.

Topics: Design
Commentary by Dr. Valentin Fuster
2006;():315-324. doi:10.1115/IMECE2006-15009.

At the end of a conceptual design phase, engineers choose a single (or a small set of) system concept from a large number of concept variants. In most cases, there is not enough design information to quantitatively evaluate how a final system developed from each concept would perform and cost. Thus engineers need to first perceptually evaluate and select a concept, and then design a system. On the other hand, if engineers know analytical relationships between system and part requirements, they can specify target values of part requirements such that a system achieves its target requirements. Furthermore, if engineers know how much it will cost to control part requirements within tolerances, they can minimize the cost of a system by optimizing tolerances of part requirements. This paper proposes and illustrates an approach to select a system concept when engineers know the relationship between system and part requirements, and how much it will cost to control part requirements within tolerances. Engineers choose a concept that minimizes cost.

Commentary by Dr. Valentin Fuster
2006;():325-336. doi:10.1115/IMECE2006-15059.

In order to achieve mass customization, companies focus on the effective usage of the Modules-of-the-shelf (MOTS) as opposed to purely relying on developing Product Specific Modules (PSM). Hence, there is a need to develop a proper methodology to evaluate the "develop PSM vs. use MOTS" decisions. This decision holds greater significance for the modular architecture, as increase in the PSM leads to decrease in the degree of the modularization of the product architecture. The compatibility issue of the MOTS and PSM has been explicitly defined in the present paper. While making the abovementioned decision, information pertaining to suppliers providing the components/modules is critical. In this study, in addition to the common criteria like cost and performance, we have also included risk assessment of the suppliers while selecting them for providing the modules. This leads to the development of a multi-objective design optimization formulation to determine the amount of MOTS and PSM in the product. To cope with the vagueness inherent in the various decision parameters, a fuzzy goal programming based approach has been applied. The design problem of a TV receiver circuit has been taken from the literature to show the efficacy of the proposed methodology.

Commentary by Dr. Valentin Fuster
2006;():337-349. doi:10.1115/IMECE2006-15397.

In today's scenario, many product development projects run the risk of being over budget and/or run past the scheduled deadlines. A major part of this can be attributed to the lack of effective and realistic product planning. We use the thesis that consideration of appropriate suppliers at the right time in a product development project can reduce wastes like waiting for parts to become available, unnecessary design iterations, design defects and poor design, and mitigate risks related to technology and enterprise capability. In the present paper, we present a methodology for effective supplier involvement in a product development project by blending the Design Structure Matrix (DSM) and the PERT/CPM techniques and considering supplier lead times and component interfaces of a given product architecture. We discuss the various options of supplier consolidation, postponement or early involvement of suppliers, and their effects on the product development project cost and schedule. We will demonstrate the working of the proposed methodology using a case example.

Commentary by Dr. Valentin Fuster
2006;():351-359. doi:10.1115/IMECE2006-16110.

Consideration of a mechanism for high-speed application inevitably poses certain kinematic design requirements that can be cast as a function generation synthesis problem involving the entire motion cycle of the mechanism. This paper addresses such application of RSSR four bar mechanisms for high-speed application. It employs a perturbational kinematic analysis of the mechanism to obtain approximate equations relating the follower and input angular displacements. The follower angular motion is derived, approximately, as a linear combination of two simple harmonic functions, in terms of the first and second harmonics of the crank angle. Albeit the exact mathematical description relating the input and output links exists it is not conducive to a kinematic design for dynamic performance. In contrast the approximate equations derived in this paper enable function generation of RSSR four bar mechanisms in which the higher harmonics of the input link are minimized. This utility of the approximate equations are demonstrated through several mechanism design examples.

Commentary by Dr. Valentin Fuster
2006;():361-369. doi:10.1115/IMECE2006-13216.

Hypoid gears are widely used in rear drive and 4WD vehicle axles. Investigation of their sensitivity to misalignments is one of the most important aspects of their design and optimization procedures. Because of unavoidable mounting deflections under working load, the values for mounting distances and angle deviate from the designed (desired) values (due to elastic deformation of differential housing and gear shafts). As a result the performance characteristics will be changed. This study provides a calculation procedure to design "optimized vehicle differential housing side elastic coefficients" that maintains primary performance characteristics during load variations (caused by both the road and engines). The calculation is based on third order contact surface parameters for combined mismatched tooth surfaces. Calculations will be done in four separate groups to maintain four primary groups of performance characteristics, including: i) the amount of transmission error ii) contact pattern shape (by controlling bias angle) iii) backlash and iv) contact pattern size; in all mentioned cases theoretical contact pattern position during differential housing deflections is kept unchanged. Moreover, an experimental analysis was performed on a hypoid gear pair, the results of which were in close relation to theoretical results of sensitivity of contact pattern location. The method used in this study gives insight to effects of differential housing and gear shaft deflections (as misalignments) on hypoid gear performance. Considering this information in differential housing and gear shaft design will provide more correlations between hypoid gear pair and their housing and shafts in order to optimize performance characteristics under actual load.

Commentary by Dr. Valentin Fuster
2006;():371-379. doi:10.1115/IMECE2006-13256.

A computer simulation was conducted to investigate the effectiveness of profile modification for reducing dynamic loads in high-contact-ratio gears with different tooth spacing errors. The simulation examined varying amplitudes of spacing error and differences in the span of teeth over which the error occurs. The modification considered included both linear and parabolic tip relief. The dynamic analysis was performed using a revised version of a NASA gear dynamics code, modified to take into consideration the tooth spacing errors in the dynamic analysis. The findings of this study can be used to design robust tooth profile modification for improving dynamic performance of high-contact-ratio gear sets with different tooth spacing errors.

Commentary by Dr. Valentin Fuster
2006;():381-390. doi:10.1115/IMECE2006-13295.

In this paper, the analytical conditions for global transversality and tangency of a 2-D nonlinear dynamical system are derived. Further, a periodically forced, damped Duffing oscillator with a separatrix is investigated as an application example. The corresponding analytical conditions for the global transversality and tangency to the separatrix are obtained and the global and tangential flows are illustrated to verify the analytical conditions. The illustrations show that the analytical and numerical predictions of the global transversality and tangency exactly are agreed very well. The analytical conditions are obtained from the new theory rather than the Melnikov method. The new conditions for the global transversality and tangency are more accurate and independent of the small parameters. Therefore, chaotic flows based on the global transversality will be further investigated, and the corresponding results will be presented in a sequel.

Commentary by Dr. Valentin Fuster
2006;():391-399. doi:10.1115/IMECE2006-13322.

A novel mathematical model for analyzing the dynamic property of the liquid motion is developed. The work in this paper assesses and further develops the mathematical model formulated especially for analyzing the liquid motion in horizontal cylindrical tanks. The present research talks about the liquid sloshing and the cyclic forces produced as a result of it. These forces which are cyclic in nature degrade the structure of a tank vehicle transporting liquid cargo. The validation of the proposed model is performed by an effective Eulerian fixed grid technique, which implements the Volume of Fluid (VOF) model. Finally this paper presents a comparison for various results obtained by implementing both the models. Such a comparison is very important, as it will validate the effectiveness of the proposed model to be considered for integrating it with structural and fatigue analysis.

Topics: Sloshing
Commentary by Dr. Valentin Fuster
2006;():401-408. doi:10.1115/IMECE2006-13323.

This research intends to investigate the nonlinear behavior of a rotating system with a cracked shaft mounted with a disc. Effects of the geometric nonlinearity, the masses of the shaft and disc and the viscoelastic supports of the rotating system on the motion of the system are studied. The characteristics of the system, such as bifurcations, periodic, quasiperiodic and chaotic behavior are evaluated. Effects of crack depth and rotating speed on the nonlinear behavior of the system are also investigated.

Commentary by Dr. Valentin Fuster
2006;():409-415. doi:10.1115/IMECE2006-13324.

This paper focuses on the availability of reliable and widely recognized standards for measuring the tyre/pavement noise by determining the existence for a common or certified standard for measuring the asphalt rubber road noise and the possibilities of establishing a common standard or making enhancement to the current standard for accurately measuring the noise. A noise measurement study is conducted using one of many methodologies recognized internationally on both conventional and asphalt rubber road. The noise measurement study is based on the Statistical Pass-by method which is described in detail in the International Standards Organization ISO 11819-1. Certain modifications have been made in order to suit the local environmental condition during the measurement. The most significant modification from the ISO 11819-1 is the distance of the microphone location that is used in the noise measurement from the center of the test road. The ISO 11819-1 stated the microphone position as 7.5m distance from the test road. However, in North America, 15m distance is commonly used. The proportions between noise source dimensions and microphone distance are affected in such a way as to reduce the potential difference between LAmax (maximum sound pressure level) and LAE (Single-event sound exposure level) [2]. Simulations can be done to find out the influence of the microphone distance to the accuracy and reliability of the test measurement readouts besides the advantages and the disadvantages on using both microphone distances from the test road. To further prove the reliability of the study, the results are then analyzed and compared to the predicted noise level using the Traffic Noise Model (TNM) developed by the Federal Highway Administration (FHWA). The FHWA's TNM that computes highway traffic noise is constructed based on the large amount of vehicle noise-emissions database and has been made comparisons to at least five other different model results or real noise measurement study to verify the accuracy of the model.

Topics: Acoustics , Rubber , Asphalt , Roads
Commentary by Dr. Valentin Fuster
2006;():417-423. doi:10.1115/IMECE2006-13325.

Asphalt Rubber Concrete (ARC) pavement has shown an excellent performance of noise reduction in terns of reducing the power of air pumping, absorbing sound power, depressing carcass vibration and changing sound reflection geometry. This research is to investigate the traffic noise reduction performance of a segment of test highway with ARC pavement in Saskatchewan, Canada. Before and after the highway section was repaved, a series of traffic noise level measurements combining with traffic flow monitoring are conducted in order to compare the sound performance of ARC and conventional pavements. A relationship between the noise level and corresponding traffic flow conditions of ARC pavement is established. The energetic averaging method is employed to study the relationship between traffic noise level and traffic flow condition. The two noise levels of 24-hour's time averaged and Statistical Pass-By noise levels indicated that the ARC pavement has a better sound performance over that of conventional pavement in terms of traffic noise reduction. The traffic noise reduction applicability of ARC pavement under various traffic flow conditions is also performed in this research.

Commentary by Dr. Valentin Fuster
2006;():425-431. doi:10.1115/IMECE2006-13326.

Wave propagation in porous medium saturated by immiscible fluids has received significant interests from the researchers in searching for comprehensively understanding the behavior of underground motion such as seismic wave propagation and artificial vibration in oil or gas reservoirs. In this research, the wave field of a porous medium saturated by two immiscible fluids is investigated. The elastic domain considered is excited by multiple cylindrical energy sources. The wave field of the whole domain with the excitation of several fast compressible waves in low frequency range is considered. Polar coordinates are utilized for the need of describing the multi-energy sources, so that the propagating waves can be expressed with the utilization of Hankel function. A moving-coordinate method is employed to study the coupling of multiple waves. The combined effects from several sources on the wave propagation are investigated and comparison with that of a single phase fluid is also addressed. With the employment of the methodology established, the wave field at any desired domain considered can be quantitatively determined in terms of wave propagation, frequencies and amplitudes of the source waves. To demonstrate the implementation of the model developed in this research, a numerical simulation is provided. The results of this research contribute to the comprehension of liquids and solid interaction under the excitation of waves, such as seismic, electromagnetic and other artificial vibrations.

Commentary by Dr. Valentin Fuster
2006;():433-439. doi:10.1115/IMECE2006-13327.

Traffic noise prediction techniques are important tools for assessing the effects of noise mitigation. A number of noise prediction models are available for predicting noise levels at a receptor point. Traditionally, these noise predictions are limited to road side areas, where the effects of building and other infrastructure act as a barrier impediment to noise propagation are not considered. This paper describes the application of simulation and modeling of a simplified traffic noise prediction method based on the U.S. FWHA highway and existing traffic noise prediction models. The simplification has been achieved mainly by using the assumption that traffic flow speeds of various vehicle classes are correlated and similar in magnitude Also, an assumption is made that ground attenuation depends not only on the type of ground cover but also on a horizontal distance between the source and the receiver. Finally, the research intends to numerically evaluate the tire-pavement noise of the road with Asphalt Rubber (AR) pavement to minimize the traffic noise generated by the pavement. The application of simulation and modeling by packaged software will be introduced for utilizing the results, planning purposes and preliminary prediction of the traffic noise level on the AR pavement road section in Saskatchewan. This traffic noise prediction model will be simple to use by any end users, particularly environmental planners, acoustic engineers, and non-specialists.

Commentary by Dr. Valentin Fuster
2006;():441-450. doi:10.1115/IMECE2006-13377.

The sandwich structures in aerospace industry experience high noise transmissions since they are often stiff and light, and have low damping. Optimization studies of sandwich structures for noise transmission are relatively fewer. Most optimization studies in composite sandwich community seek for high stiffness with minimal weight. Advanced sandwiches must meet not only stiffness to weight ratio demands, but also have improved acoustic transmission performance. This paper presents recent advances in optimization of sandwich structures for minimum sound transmission. The finite element models of sandwich beams and plates are presented in this paper. The acoustic radiation of the structure is computed by using the Rayleigh integral. Sensitivity plays an important role in optimization studies. Analytical expressions of sensitivity can improve computational efficiency dramatically and accuracy at the same time. The explicit sensitivity functions of power and natural frequencies with respect to design parameters are derived in this work. In the optimization studies, we have considered structural parameters that can influence the transverse propagation of sound from the sandwich to the acoustic medium. These parameters include core topology and coupling stiffiness between in- and out-of-plane strains. We also study the optimization of the structure with respect to the structural boundary conditions to minimize the sound transmission. Numerical examples of single tone and broadband applications are presented in the paper. The results show that significant reduction of sound transmission across sandwich structures can be obtained. Finally, it should be noted that the novel optimized sandwich structures can meet not only stiffness to weight ratio demands, but also have significantly improved acoustic performance.

Commentary by Dr. Valentin Fuster
2006;():451-459. doi:10.1115/IMECE2006-13630.

This paper presents a hybrid parallelizable algorithm for the computer-aided modeling of the dynamic behavior of multibody open tree systems. The method is based on cutting certain system interbody joints at branched bodies so that a system of largely independent multibody subchains is formed. These subchains interact with one another through associated unknown constraint forces fc at the cut joints. The increased parallelism is obtainable through cutting joints and the explicit determination of associated constraint forces combined with a sequential O(n) procedure. Consequently, the sequential O(n) procedure is carried out within each subchain to form and solve the equations of motion, while parallel strategies are performed between the subchains to form and solve constraint equations concurrently. Two extreme cutting procedures are further discussed to conduct a comparison of computational efficiency. One case is to cut the joints at branched bodies so that the longest lengths of subchains are obtained and the other is to cut the joints at branched bodies so that the shortest lengths of subchains are formed. The algorithm can easily accommodate the available number of processors while maintaining high efficiency. The algorithm will also be implemented on both parallel homogeneous computing (PHC) systems and network-distributed heterogeneous computing (DHC) environment. The implementation of the algorithm in a DHC environment will permit engineers and researchers to conduct distributed simulation of dynamic behaviors of large and complex multibody systems on ubiquitous network-distributed PC workstations in their workplace. In short, the exploration of the parallelizable algorithm for a multibody tree system will provide a deep understanding of the relationship between computational load balancing and optimal joint locations to be cut. The computational efficiency of the algorithm can be increased further.

Commentary by Dr. Valentin Fuster
2006;():461-467. doi:10.1115/IMECE2006-13640.

Now, ultrasonic cleaning has been widely used in industry, however its applications in our lives are very few. It is theoretically possible that ultrasonic cleaning could be applied in civil. The author studies a kind of portable ultrasonic cleaning machine which is suitable for various fields. In consideration of the portable ultrasonic cleaning machine characteristics such as small, convenient, high frequency and high intensity focus, the author presents a model of compound acoustic horn which is composed of a conic horn of varying section and a horn of uniform section. Because this compound acoustic horn which has complicated shape is not traditional horn, and it is difficult to analyze it with traditional method. This situation is able to influence on the design of the acoustic horn, especially the confirmation of the vibration node, even the whole system matching. So in this paper the finite-element method (FEM) is used to analyze the dynamic performance of the compound acoustic horn. By the finite-element analysis, the natural frequency and the natural vibration mode of the compound acoustic horn are ascertained, furthermore, from the graph results we can find the stress and the displacement in the end of the acoustic horn are the biggest, but the displacement in the Flange is about zero. So the reliability performance and the reasonable design of the compound acoustic horn are proved in theory. In addition, the tests indicate the result of the finite-element analysis tallies with that of actual use after processing the compound acoustic horn.

Commentary by Dr. Valentin Fuster
2006;():469-476. doi:10.1115/IMECE2006-13744.

The constitutive relationships of the rubber materials that act as the main spring of a hydraulic mount are nonlinear. In addition to material induced nonlinearity, further nonlinearities may be introduced by mount geometry, turbulent fluid behavior, boundary conditions, temperature, decoupler action, and hysteretic behavior. While all influence the behavior of the system only certain aspects are realistically considered using the lumped parameter approach employed in this research. The nonlinearities that are readily modeled by the lumped parameter approach constitute the geometry and constitutive relationship induced nonlinearity, including hysteretic behavior, noting that these properties all make an appearance in the load-deflection relationship for the mount and may be readily determined via experiment or flnite element analysis. In this paper we will shoe that under certain conditions, the nonlinearities involved in the hydraulic engine mounts can show a chaotic response.

Commentary by Dr. Valentin Fuster
2006;():477-481. doi:10.1115/IMECE2006-13748.

In this paper, a hydrodynamically coupled flexible disk rotating in a thin housing is mathematically modeled and an attempt is made to explain the jump instability phenomenon that occurs when the disk rotation speed is varied slightly. The disk is assumed to have an initial warped profile due to slight imperfections in the manufacturing process. After non-dimensionalization of the participating variables, a hybrid formulation is carried out. Radial flows above and below the disk are taken into consideration. The deflection and pressure equations form a coupled system, and a solution is attempted using the shooting method. The deflections obtained are plotted to obtain the deflected disk profile and appropriate conclusions are drawn.

Topics: Warping , Disks
Commentary by Dr. Valentin Fuster
2006;():483-489. doi:10.1115/IMECE2006-13775.

Truncated conical shell is an important structure that has been widely applied in many engineering fields. The present paper studies the internal dynamic properties of a truncated rotary conical shell with considerations of intercoupling the high and low order modals by utilizing Harmonic Balance Method. To disclosure the detailed intercoupling characteristics of high order modal and low order modal of the system, a truncated shallow shell is studied and the internal response properties of the system is investigated by using the Multiple Scale Method. Abundant dynamic characteristics are found in the research of this paper. It is found in the research of the paper that the high-order modals of rotating conical shells have significant effects to the amplitude and frequency of the shells.

Topics: Resonance , Shells
Commentary by Dr. Valentin Fuster
2006;():491-501. doi:10.1115/IMECE2006-13804.

In this paper, the methodology is presented through investigation of a periodically, forced linear oscillator with dry friction, resting on a traveling surface varying with time. The switching conditions for stick motions in non-smooth dynamical systems are obtained. From defined generic mappings, the corresponding criteria for the stick motions are presented through the force product conditions. The analytical prediction of the onset and vanishing of the stick motions is illustrated. Finally, numerical simulations of stick motions are carried out to verify the analytical prediction. The achieved force criteria can be applied to the other dynamical systems with nonlinear friction forces possessing a CO - discontinuity.

Topics: Friction , Motion
Commentary by Dr. Valentin Fuster
2006;():503-512. doi:10.1115/IMECE2006-13818.

Periodic motions in a hysteretically damped, semi-active suspension system are investigated. The Magneto-Rheological damping varying with relative velocity is modeled through a piecewise-linear model. The theory for discontinuous dynamical systems is employed to determine the grazing motions in such a system, and the mapping technique is used to develop the mapping structures of periodic motions. The periodic motions are predicted analytically and verified numerically. The stability and bifurcation analyses of such periodic motions are performed, and the parameters for all possible motions are developed. This model is applicable for the semi-active suspension system with the Magneto-Rheological damper in automobiles. The further investigation on the Magneto-Rheological damping with full nonlinearity should be completed.

Commentary by Dr. Valentin Fuster
2006;():513-518. doi:10.1115/IMECE2006-13826.

The finite element absolute nodal coordinate formulation (ANCF) leads to beam and plate models that relax the assumption of the classical Euler-bernoulli and Timoshenko beam and Mindlin plate theories. In these more general models, the cross section is allowed to deform and it is no longer treated as a rigid surface. The coupling between the bending and cross section deformations leads to the new ANCF-coupled deformation modes that are examined in this study. While these coupled deformation can be source of numerical and convergence problems when thin and stiff beam models are considered, the inclusion of the effect of these modes in the dynamic model is necessary in the case of very flexible structures. In order to examine the effect of these coupled deformation modes in this investigation, three different large deformation dynamic beam models are discussed. Two of these models, which differ in the way the beam elastic forces are calculated in the absolute nodal coordinate formulation, allow for systematically eliminating the coupled deformation modes, while the third allows for including these modes. The first of these models is based on a general continuum mechanics approach that leads to a model that includes the ANCF-coupled deformation modes; while the second and third methods that can be used to eliminate the coupled deformation modes are based on the elastic line approach and the Hellinger-Reissner principle. It is shown in this study that the inclusion of the ANCF-coupled deformation modes introduces geometric stiffening effects that can not be captured using other finite element models.

Topics: Deformation
Commentary by Dr. Valentin Fuster
2006;():519-530. doi:10.1115/IMECE2006-13827.

In this paper, the stability and bifurcation of periodic motions in periodically forced oscillator with multiple discontinuities is investigated. The generic mappings are introduced for the analytical prediction of periodic motions. Owing to the multiple discontinuous boundaries, the mapping structures for periodic motions are very complicated, which causes more difficulty to obtain periodic motions in such a dynamical system. The analytical prediction of complex periodic motions is carried out and verified numerically, and the corresponding stability and bifurcation analysis are performed. Due to page limitation, grazing and stick motions and chaos in this system will be investigated further.

Topics: Motion
Commentary by Dr. Valentin Fuster
2006;():531-536. doi:10.1115/IMECE2006-14099.

The vibration characteristics of the vocal folds are investigated using a finite element model which incorporates the in-homogeneity and anisotropy of the materials and the irregularity of the geometry. The model employs the cover and body theory to build the structure of the vocal folds and implements measured viscoelastic properties of the mucosa and the transverse isotropic elastic properties of the muscles. It has the potential to simulate some vocal-fold disorders and determine the change in characteristics. To determine the oscillation characteristics of the folds, the eigenfrequency and eigenmodes of the finite element model are determined using the ABAQUS software. The model results compare well with some experiments performed on a silicon vocal fold. It is anticipated that the model will help to identify voice disorders such as vocal-fold paralysis and vocal-fold nodules.

Commentary by Dr. Valentin Fuster
2006;():537-544. doi:10.1115/IMECE2006-14241.

A typical problem encountered when studying turbo-machineries is studied: contact between a rotor and his stator. The contact is supposed to be permanent and frictionless; both rotor and stator are linked to the carter in an elastic and dissipative way. Under these modelling assumptions, nonlinear vibrations appear through the geometry of the problem when the system is excited by an out-of-balance within the rotor. Equations are written in the rotating frame in order to simplify the resultant frequency content of the dynamic quantities followed along the excitationnal frequency range. The stability and bifurcation analysis of a particular equilibrium is carried on. This first stage exhibits two Hopf bifurcation points. The associated periodic solutions are constructed and followed, using a shooting method. A specific bifurcation diagram is then established, where the incommensurate period of the solution is shown.

Topics: Rotors , Stators
Commentary by Dr. Valentin Fuster
2006;():545-549. doi:10.1115/IMECE2006-14391.

Recent research has demonstrated that natural frequencies associated with some circumferential modes inn fluid filled tanks may be close to the frequency of earthquake excitation. This can lead to a resonance phenomenon, and consequently failure of the tanks. In this paper, we perform natural frequency analysis of fluid-filled tanks, using finite element analysis. The problem is solved for different geometries and water levels of tanks. Results are provided for circular, cylindrical tanks and cylindrical tanks with coaxial walls and a fluid annulus. Combinations of parameters most likely to cause resonance are presented.

Topics: Resonance
Commentary by Dr. Valentin Fuster
2006;():551-560. doi:10.1115/IMECE2006-14434.

In this research, we develop a general methodology for the vibration control of nonlinear rotating beam. The dynamic model of a rotating Euler-Bernoulli beam integrated with piezoelectric actuator is formulated. An integral sliding mode control design is proposed for the vibration suppression of the system with nonlinear coupling effects between the hub rotation and the beam transverse vibration. The sliding surface is constructed using part of the system states, and the rotating hub dynamics is treated as the internal dynamics of the system under the condition that the states of the zero dynamics are bounded. The robust stability of the proposed controller is also guaranteed. A series of simulation studies demonstrate that the proposed control method can effectively suppress the beam vibrations induced by the hub rotation and the external disturbance.

Commentary by Dr. Valentin Fuster
2006;():561-570. doi:10.1115/IMECE2006-14533.

D'Alembert's principle is manipulated in the presence of nonholonomic constraints to derive the principle of virtual power in nonholonomic form, and Lagrange's equations for nonholonomic systems. The Lagrangian equations had been expressed previously for conservative systems, derived by variational methods. The D'Alembert derivation confirms the roles of constrained and unconstrained Lagrangians directly by the presence of constrained and unconstrained velocities in D'Alembert's principle. The constrained form of nonconservative generalized forces is also determined for both particles and rigid bodies. An example is a rolling disk.

Commentary by Dr. Valentin Fuster
2006;():571-577. doi:10.1115/IMECE2006-14756.

The history of the challenge of friction modeling is briefly reviewed. Then this paper focuses on the modeling and simulation study of the friction related dynamics in the Simulink® environment, because Matlab®/Simulink® are popular engineering software tools for both industry and academia. Matlab® and Simulink® are the proprietary products of MathWorks, Inc. In this paper, the static friction models are studied through Simulink® by applying fixed and variable step sizes. The comparison shows that the static Karnopp model is not only numerically tractable but also can be inclusive of the fundamental friction characteristics of both stick slip and correct friction predictions. Finally this paper presents an improved Karnopp model for clutch modeling with the use of Simulink®, and the simulation shows that this model is computationally tractable with smooth dynamics.

Commentary by Dr. Valentin Fuster
2006;():579-590. doi:10.1115/IMECE2006-14799.

This paper investigates the experimental dynamics of a beam structure that supports an attached rigid body and that can impact a comparatively compliant base structure. The problem area is motivated by impact phenomena that are observed in certain structures internal to nuclear reactors. The assembly is subjected to base excitation at specified frequency and acceleration, and the resulting displacement and velocity time histories are recorded and used to obtain spectra, phase diagrams, and Poincaré sections. The measurements validate simulation results obtained by using a constraint and modal mapping method based on the two sets of modes when the structure is in-contact, and when it is not-in-contact. Generalized coordinates are mapped across the impact discontinuities in the modal representation. The forced response simulation predicts the test specimen's response over a range of excitation frequencies. The specimens are fabricated as single integral structures from acrylnitrile butadene styrene plastic through rapid prototyping technology in order to eliminate the undesirable dissipation and flexibility arising from joints and connections. The experimental system can exhibit complex response characteristics, and the influences on complexity of deadband clearance and of asymmetry in the point of impact are examined in the experiments.

Commentary by Dr. Valentin Fuster
2006;():591-606. doi:10.1115/IMECE2006-14811.

This paper presents a comprehensive model to capture the dynamics of a motorcycle system in order to evaluate the quality of vibration isolation. The two main structural components in the motorcycle assembly - the frame and the swing-arm - are modeled using reduced order finite element models; the power-train assembly is modeled as a six degree-of-freedom (DOF) rigid body connected to the frame through the engine mounts and to the swing-arm through a shaft assembly. The engine mounts are modeled as tri-axial spring-damper systems. Models of the front-end assembly as well as front and rear tires are also included in the overall model. The complete vehicle model is used to solve the engine mount optimization problem so as to minimize the total force transmitted to the frame while meeting packaging and other side constraints. The mount system parameters - stiffness, position and orientation vectors - are used as design variables for the optimization problem. The imposed loads include forces and moments due to engine imbalance as well as loads transmitted due to irregularities in the road surface through the tire patch.

Commentary by Dr. Valentin Fuster
2006;():607-622. doi:10.1115/IMECE2006-14821.

This paper presents Response Surface Methodology (RSM) modeling techniques to solve the engine mount optimization problem for motorcycle applications. A theoretical model that represents the structural dynamics of the engine mount system in motorcycles is first used to build the RSM model. The RSM model is then used to solve the engine mount optimization problem to enhance vibration isolation. This leads to a substantial reduction in computational effort and simplifies the governing model, yielding an input-output relationship between the variables of interest. Design of Experiments (DOE) techniques are used to build the RSM model from the theoretical model. Full factorial and fractional factorial formulations are used to construct the governing experiments. Normal probability plots are used to determine the statistical significance of the resulting coefficients. The statistically significant variables are then used to build the response surface. The design variables for the engine mount optimization problem include mount stiffness, position and orientation vectors. The influence of the orientation variables is highly non-linear and is difficult to model by using a response surface consisting of lower order terms only. Two separate algorithms are proposed to overcome this problem and the results from the RSM models are compared to those from the theoretical model.

Commentary by Dr. Valentin Fuster
2006;():623-630. doi:10.1115/IMECE2006-14842.

Conventional method of measuring the mechanical properties of rotating machinery is to couple sensors on the machine through a slip ring, which is a non-trivial, expensive, lengthy and manpower intensive process. An alternative to this is to use a contactless RF slip ring which has no physical wear and hence no maintenance. But application of contactless RF slip ring is possible only if these services are low powered and sensor signals can be multiplexed. With the advance in low powered MEMS sensors, contactless slip ring system can be used. But providing power to these sensors is an issue. One approach would be to harness power from the untapped surrounding energy which could be used to recharge and/or replace battery powered connections. One method to accomplish this is to use piezoelectric materials (PZT) to capture energy lost due to vibration and rotation of the test equipment. This captured energy can then be used to provide uninterrupted power to the appropriate sensors. Focusing our attention on blades, rotating structures will be modeled as cantilever beam. Piezoelectric bimorph attached to the rotating cantilever beam will provide an estimate for the available power that can be used for harvesting.

Commentary by Dr. Valentin Fuster
2006;():631-640. doi:10.1115/IMECE2006-14853.

The free and forced vibration of a moving medium is examined in an application where distributed friction guiding is used to control lateral position passively. Sub-ambient pressure features formed in the guides intentionally modify the naturally occurring self-pressurized air bearing and increase the contact force between the medium and the guide's surface. These features increase friction to a level beyond that achievable based on the nominal wrap pressure. The moving medium is modeled as a beam that is transported over frictional regions and that is subjected to prescribed boundary disturbances arising from runout of a cartridge or pack. For axial transport at a speed that is high compared to the vibration velocity, Coulomb friction between the guides and the moving medium can be well-approximated by a derived expression for equivalent viscous damping. The equation of motion is developed for the cases of a single cylindrical guide, and of a multiplicity of guides having arbitrary placement. The level of equivalent damping for each mode decreases with transport speed, and critical speeds exist where each vibration mode transitions between the overdamped and underdamped regimes. Parameter studies in the contact pressure, transport speed, and guide geometry identify preferred design configurations for maximizing dissipation in particular modes and for attenuating high frequency response.

Topics: Friction , Vibration
Commentary by Dr. Valentin Fuster
2006;():641-654. doi:10.1115/IMECE2006-14891.

An indispensable part of the off-road construction equipment industry, the front-end-loader (FEL) is a classic example of a working machine, having complex—often nonlinear—interaction between its hydraulic, mechanical, and electrical subsystems [1]. Current state-of-the-art in dynamic simulation of these machines employs full-scale vehicle models and an event-based operator model to quantify the overall system performance, efficiency, and operability. Quantifying these machine parameters is further complicated by the variability in the machine's working environment and task profile. It is recognized that full-scale simulations may offer the most insight into the machine performance and system efficiency; however, even simplified models can yield useful information for structural design, rapid prototyping, and local optimization. This paper explores developing a sub-scale dynamic model for the boom and bucket manipulator system on a FEL that will adequately characterize the system response for the purposes of design and optimization. The equations of motion for the multi- rigid body model of the manipulator system are derived using Kane's method. State equations governing the hydraulic flow to the cylinders and reaction forces on the bucket are employed to model the manipulator system's interaction with the machine and work-pile, respectively. Output from the dynamic simulation is correlated and compared to data gathered during field test operation of the machine.

Topics: Stress , Design , Cycles , Wheels
Commentary by Dr. Valentin Fuster
2006;():655-672. doi:10.1115/IMECE2006-14978.

This paper studies sensitivity of compound planetary gear natural frequencies and vibration modes to system parameters. Based on a lumped parameter model of general compound planetary gears and their distinctive modal properties [1], the eigensensitivities to inertias and stiffnesses are calculated and expressed in compact formulae. Analysis reveals that eigenvalue sensitivities to stiffness parameters are directly proportional to modal strain energies, and eigenvalue sensitivities to inertia parameters are proportional to modal kinetic energies. Furthermore, the eigenvalue sensitivities to model parameters are determined by inspection of the modal strain and kinetic energy distributions. This provides an effective way to identify those parameters with the greatest impact on tuning certain natural frequencies. The present results, combined with the modal properties of general compound planetary gears, show that rotational modes are independent of translational bearing/shaft stiffnesses and masses of carriers/central gears, translational modes are independent of torsional bearing/shaft stiffnesses and moment of inertias of carriers/central gears, and planet modes are independent of all system parameters of other planet sets, the shaft/bearing stiffness parameters of carriers/rings, and the mass/moment of inertia parameters of carriers/central gears.

Commentary by Dr. Valentin Fuster
2006;():673-678. doi:10.1115/IMECE2006-15238.

The main purpose of this study is to offer a comprehensive off-tuning analysis of a semi-active tuned vibration absorber. A base-excited, single-degree-of-freedom structure with a tuned vibration absorber (TVA) model is adapted as the baseline model for our analysis. Moreover, a non-model based groundhook control (displacement based on-off control or "On-off DBG") is used to control the damping in the TVA. In order to study the effect of off-tuning, numerical models of the damping controlled TVA along with its equivalent passive TVA were developed. Using these models, the optimal tuning parameters of both TVA models were obtained based on minimization of peak transmissibility. The two optimally tuned models were then "off-tuned" by varying the primary structure's mass, stiffness, and damping. Using the peak transmissibility reduction criteria, the dynamic performances of the off-tuned TVAs were evaluated. The results indicate that the peak transmissibility of the semi-active TVA is about 20% lower than that of passive, implying that the semi-active TVA is more effective in reducing vibration levels. The results further indicate that the semi-active TVA is more robust to changes in primary structure mass and stiffness. In summary, the offtuning analyses of the semi-active TVA revealed the practical benefits of using it over the passive counterpart to structures subjected to changes in system parameters.

Commentary by Dr. Valentin Fuster
2006;():679-685. doi:10.1115/IMECE2006-15688.

An analytical technique for identification of the location of an unknown vertical exciting force on the surface of ground using sensors fusion is presented. The analysis is based on the dynamic responses of points on the surface of an elastic half-space medium subjected to a vertical, harmonic and concentrated force on the surface. The medium is assumed to be an elastic, isotropic and homogeneous half-space. The problem is analytically formulated by employing double Fourier transforms, and the solution is obtained in the form of integral expressions in terms of Rayleigh functions. Numerical techniques are utilized for the computation of integrals presented by the inverse transforms. Non-dimensional values for the in-phase and quadrature components of the displacements for any position on the surface of the unloaded half-space in terms of frequency and position of the exciting force are presented for a Poisson's ratio of 0.25.

Commentary by Dr. Valentin Fuster
2006;():687-695. doi:10.1115/IMECE2006-15734.

The forced nonlinear dynamics of a pre-buckled thermally loaded annular plate are investigated. The plate is modeled using the von Kármán plate theory and the heat equation. The heat, which is generated by the difference between the uniformly distributed temperatures at the inner and outer boundaries, is assumed to symmetrically flow in the radial direction. The amount of heat affects the natural frequencies, which may give rise to different internal resonance conditions. The method of multiple scales is used to examine the system axisymmetric responses when it is driven by an external multi-frequency excitation. The plate responses could be very complex exhibiting Hopf and cyclic-fold bifurcations, quasi-periodicity, chaos, and multiplicity of attractors.

Commentary by Dr. Valentin Fuster
2006;():697-705. doi:10.1115/IMECE2006-13495.

In identifying machines and structures, one sometimes encounters cases in which the system should be regarded as a nonlinear continuous system. The governing equations of motion of a nonlinear continuous system are described by a set of nonlinear partial differential equations and boundary conditions. Determining both of them simultaneously is a quite difficult task. Thus, one has to discretize the governing equations of motion, and reduce the order of the equations as much as possible. In analysis of nonlinear vibratory systems, it is known that one can reduce the order of the system by using the nonlinear normal modes preserving the effect of the nonlinearity accurately. The nonlinear normal modes are description of motion by nonlinear functions of the coordinates for analysis. In identification it is expected that an accurate mathematical model with minimum degree of freedom can be determined if one can express the response as nonlinear functions of the coordinates for identification. Based on this idea, this paper proposes an identification technique which uses nonlinear principal component analysis by a neural network. Applicability of the proposed technique is confirmed by numerical simulation.

Commentary by Dr. Valentin Fuster
2006;():707-715. doi:10.1115/IMECE2006-13647.

To enhance transport safety and reliability of ropeway systems, it is essential to reduce the swing of the carriers that results from wind, etc. As a means to lessen the swing of the carriers, we will propose damping equipment that uses two balls as the movable mass. We will also discuss the method for adjusting the design parameters for this equipment. Based on a simulation, we will determine the effect of this equipment. In addition, we will refer to the results of a model test to verify the effect of this damping equipment.

Topics: Damping
Commentary by Dr. Valentin Fuster
2006;():717-724. doi:10.1115/IMECE2006-14320.

In recent years the automotive industry has been working towards intelligent suspension systems that adapt to various road conditions to provide a superior ride and improved road handling. So called semi-active devices, in particular smart fluid dampers, are a viable method of implementing such a system. Despite the fact that magnetorheological (MR) dampers have been used in a number of commercially produced vehicles to date, there is little published information on the control of such devices. Building upon a successful modelling approach developed initially for electrorheological (ER) dampers at the University of Sheffield, a computational model was developed and implemented to simulate the behavior of an MR damper. A proportional force feedback control methodology was adopted and applied to the model with the intention of linearizing the output response. The smart fluid damper is therefore forced to behave in a manner equivalent to a linear damper, with the advantage of having a controllable viscous damping coefficient. Whereas previous research has almost exclusively concentrated upon the controller gain and its influence on the range of linearization which is possible to achieve, this investigation focuses on the time response of the MR fluid and its profound impact on the ability of the control method to linearize the output. Results will be presented which show that the fluid time response introduces a high frequency oscillation into the force/velocity output responses. Simultaneously, at higher excitation frequencies non-linear output responses will be demonstrated. As the fluid time response increases, the oscillations seen at low frequencies reduce but conversely the non-linear output of even moderate excitation frequencies becomes apparent. This result shows the need for a compromise between a larger range of controllability with the introduction of noise at low frequencies, or a smaller, yet noise-free range of controllability. This result may have significance when considered in the wider context of smart fluid applications. The instability and long-term degradation of smart fluids alongside other smart fluid phenomena such as 'in-use fluid thickening' indicate that the fluid time response is apt to change as the fluid is used. With a control system which has been demonstrated to be sensitive to fluid time response this change would of course be detrimental. The authors hope to highlight fluid time response as an important consideration in the design of smart fluid control systems.

Topics: Fluids
Commentary by Dr. Valentin Fuster
2006;():725-735. doi:10.1115/IMECE2006-14379.

A method is presented for decomposing wave motion into its principle components. The basic idea is a generalization of proper orthogonal decomposition. The method involves the representation of real oscillatory signals as complex phasors. The relationship between complex modes and wave motion is explored. From an ensemble of complex signals, a complex correlation matrix is formed, and its complex eigensolution is the basis of the decomposition (like a complex singular value decomposition). The complex eigenvectors contain standing and traveling characteristics. A traveling index is proposed to quantify the relative degree of traveling and standing in a waveform. A method of dissecting a wave mode into its traveling and standing parts is also proposed. From the complex modes and modal coordinates, frequencies, wavelengths, and characteristic wave speeds can be obtained. The method is applied to traveling and standing-wave examples.

Topics: Motion , Waves
Commentary by Dr. Valentin Fuster
2006;():737-749. doi:10.1115/IMECE2006-14443.

Over the past decade, many studies have been carried out to investigate one of the unique phenomena in granular materials: vibration-induced segregation in granular mixture, i.e., under vertical vibration, larger granules rise to the top even without density difference with other granules. However, the mechanisms behind this phenomenon are not yet completely understood. In this study, the discrete element method (DEM) is used for the numerical analysis of the granular segregation in a vertically vibrating container. We systematically investigate the rising time of an intruder inside the granular mixture as a function of the granular size, density, depth, and the vibrating frequency and amplitude. Our studies show that the segregation phenomenon is caused by a variety of mechanisms within different vibration regimes. Under weak vibration, segregation is driven by the geometrical effect and inertia. Under moderate vibration, segregation can be enhanced dramatically with the occurrence of convection. Under strong vibration where the granular material becomes fluidized, the buoyancy or sinkage of granules prevails and segregation may be suppressed.

Commentary by Dr. Valentin Fuster
2006;():751-760. doi:10.1115/IMECE2006-14552.

This article reports on the experimental verification of an anti-resonance effect obtained by parametric stiffness excitation. From theoretical studies it is known that parametric excitation at non-resonant parametric resonances can improve the damping behavior of a mechanical system and even stabilize an otherwise unstable system. To demonstrate this effect, a test setup was designed, based on a two-mass vibration system, gliding on an air track. Parametric stiffness excitation (PSE) was realized by a mechanical device that creates a time-periodic stiffness by modulating the tension in an elastic rubber band. With this device it was possible to demonstrate the improved damping behavior of the system when the PSE device is operating at or near the first parametric combination resonance of difference type. Also, a simple electro-magnetic device was used to create self-exciting forces. It could be shown for the first time that it is indeed possible to stabilize the unstable system by introducing parametric stiffness excitation.

Commentary by Dr. Valentin Fuster
2006;():761-769. doi:10.1115/IMECE2006-14702.

This paper is intended to point out the relationship among current time domain modal analysis methods by employing the generalized eigenvalue decomposition. Various well-known time domain modal analysis algorithms are reviewed. Ibrahim Time Domain (ITD), Least Square Complex Exponent (LSCE) and Eigensystem Realization Algorithm (ERA) methods are chosen to do the comparison. Reformulation to these original forms show these three methods can all be attributed to a generalized eigenvalue problem with different matrix pairs. With this general format, we can see that Single-Input Multi-Output (SIMO) methods can easily be extended to Multi-Input Multi-Output (MIMO) case by taking advantage of the generalized Hankel matrix or generalized Toeplitz matrix.

Topics: Eigenvalues
Commentary by Dr. Valentin Fuster
2006;():771-778. doi:10.1115/IMECE2006-14983.

Accurate prediction of nonlinear response of a homogenous, buckled plate with clamped boundary conditions is essential in designing aircraft structures for long life and extreme combined loading. It is well known that the dynamic response becomes highly nonlinear for large response amplitudes of a buckled plate with clamped boundary condition. In this paper, a rectangular plate is experimentally studied for its nonlinear dynamic response. The results obtained are compared for the two buckling modes. Further, the numerical observations are conducted to differentiate the effect of amplitude of excitation on the nonlinear response, specifically characterizing the parametric regimes (amplitude and frequency) to differentiate between the small amplitude linear response and large amplitude snap-through response. It is desired to understand the parametric boundary separating these two qualitatively different response characteristics for its obvious impact on the fatigue life of the structure.

Commentary by Dr. Valentin Fuster
2006;():779-788. doi:10.1115/IMECE2006-15069.

In this paper, a component-based parametric reduced-order modeling (PROM) technique for vibration analysis of complex structures is presented, and applications to both structural design optimization and uncertainty analysis are shown. In structural design optimization, design parameters are allowed to vary in the feasible design space. In probabilistic analysis, selected model parameters are assumed to have predefined probability distributions. For both cases, each realization corresponding to a specific set of parameter values could be evaluated accurately based on the exact modes for the system with those parametric values. However, as the number of realizations increases, this approach becomes prohibitively expensive, especially for largescale finite element models. Recently, a PROM method that employs a fixed projection basis was introduced to avoid the eigenanalysis for each variation while retaining good accuracy. The fixed basis is comprised of a combination of selected mode sets of the full model calculated at only a few sampling points in the parameter space. However, the preparation for the basis may still be cumbersome, and the simulation cost and the model size increase rapidly as the number of parameters increases. In this work, a component-based approach is taken to improve the efficiency and effectiveness of the PROM technique. In particular, a component mode synthesis method is employed so that the parameter changes are captured at the substructure level and the analysis procedure is accelerated. Numerical results are presented for two example problems, a design optimization of a pickup truck and a probabilistic analysis of a simple L-shaped plate. It is shown that the new component-based approach significantly improves the efficiency of the PROM technique.

Commentary by Dr. Valentin Fuster
2006;():789-798. doi:10.1115/IMECE2006-15359.

To analyze the steady state response of structural dynamical systems with multi-field response (example, Timoshenko shearable rod) given complex-valued databases (finite element simulations of complexified equations of motion), we have developed a Complex Proper Orthogonal Decomposition (CPOD) transform. Like the regular multi-field POD, the development of the C-POD is based on the primitive space and frequency auto-correlation operations. These data fusion operations give rise to complex Hermitian operators whose solution determines the C-POD transform. The eigen-values of the complex Hermitian operators are strictly positive and it is shown that they represent the energy fractions of the auto-correlation energy contained in the POD modes. The POD modes have both amplitudes and shapes that are complex-valued scalar functions. The C-POD transform is verified by applying it to characterize the finite element simulations of the steady state dynamics of planar beams and arches. It turns out that the real part of the shape of a POD mode coincides with the shape of the linear POD; whereas its amplitude is a localized function of frequency at a critical frequency which is identical to a natural frequency.

Commentary by Dr. Valentin Fuster
2006;():799-807. doi:10.1115/IMECE2006-15441.

It is possible to cast a set of dynamic performance requirements of a mechanism as a set of kinematic requirements and perform design at the kinematic synthesis stage. Inadvertently, this process leads to the sythesis of mechanism for function generation in which the output motion is a simple harmonic function of the input angular position. A perturbation technique is used to find approximate simple harmonic functions relating output link angular motion to the input angle. A higher order analysis is performed to obtain more accurate estimate functions relating input and output motions. Several RSSP sythesis cases are exemplified. Error analysis for the range of parameter space is performed showing favorable performance of the mechanisms, accuracy of the approximate equations as well as error estimations.

Commentary by Dr. Valentin Fuster
2006;():809-817. doi:10.1115/IMECE2006-15497.

This work is concerned with a method to generate pure traveling vibration waves in finite structures. Using progressing deformations, i.e. waves, is not common when dealing with forced vibration since structures are naturally vibrating in their, naturally occurring, normal modes. Indeed, natural vibration modes can be referred to standing waves. Since a structure does not lend itself to a traveling wave vibration, the generation of traveling waves in a structure becomes a challenging task. The boundary conditions or external forces must be carefully tuned in an iterative process that necessitates measurement and identification of the traveling and standing wave components. In this work, a method to generate and measure traveling waves is presented for one and two-dimensional structures. Both analytical and experimental results are provided here. A traveling wave is a disturbance that propagates away from its source carrying energy along its path. In finite structures, a wave hitting a boundary experiences an impedance change that gives rise to a partial reflection, thus distorting its original form. For a pure traveling wave to occur, the boundary of the structure must be set to match the impedance of the structure, and thus to absorb the disturbance while preventing any reflected wave from the boundaries. Impedance matching can be accomplished by passive or active means. Active impedance matching is obtained by generating a vibrating wave at one end (a source) and 'pumps' it on the other, active absorbing end, often addressed as a sink. Indeed, active impedance matching sometimes referred as the "active sink" method. Special methods must be used to extract the description of the vibrating wave characteristics from the measured vibration efficiently, and possibly in real-time (for control purposes). A parametric method is employed in this work to describe and analyze the wave vibration from measurements. In reality, the theoretical knowledge of how to excite a vibrating traveling wave is not sufficiently accurate to produce traveling waves. Minute manufacturing imperfections, small structural and actuator asymmetry may cause large deviations from pure traveling waves state. It is shown that a tuning process that relies on the measurements but combined with a physical model, should serve as the basis of the practical implementation. Several experiments on a string-like structure are described stressing the physical implications as well as the refined experimental procedure. The actuation techniques, wave identification methods and the tuning procedure of a vibrating traveling wave are described in some detail for the experimental work.

Topics: Waves
Commentary by Dr. Valentin Fuster
2006;():819-825. doi:10.1115/IMECE2006-15499.

A beam is clamped at one of its ends and is subjected to a shear force at its other end which causes deformation in the principal plane with stiffest resistance to bending. Above a critical value of load, bifurcation occurs, the beam twists and experiences out-of-plane deformation which tends to transfer bending to the plane of weakest resistance. Here, attention is focused on an experimental study of dynamic lateral torsional buckling. The load is exerted, by a tip mass whose inertia provides the load-levels that lead to buckling. Specifically, in the experiment, a beam is attached to the shaft of a motor at one of its ends and a large mass is attached to its other end. Rotation of the motor causes deflection of the beam in its principal plane of stiffest bending resistance. By increasing the excitation frequency and/or amplitude of oscillation of the motor's shaft, the shear force applied by the mass on the beam's end exceeds a critical value which causes dynamic lateral torsional buckling of the beam. Buckling has been observed at several operating points with different spatial and temporal motions. The deformations in the post-buckled regime are large and often complex, for this reason non-standard experimental techniques need to be employed. Only with these techniques, comparison with numerical and analytical models can take place. This work focuses on experimental investigations using several sensing elements, a laser vibration sensor, a fast video camera and a shaft encoder whose signals have be processed simultaneously to provide sufficient information about the 3D dynamics. The paper describes the experimental system, the data and signal processing methods for the non-stationary system and the unique dynamical behavior the system under dynamic buckling conditions.

Commentary by Dr. Valentin Fuster
2006;():827-836. doi:10.1115/IMECE2006-15762.

This paper introduces research leading to a computer-aided design tool in which engineering designers can test various concepts in an environment equipped to automatically model the dynamics and then optimize the specified components to best meet the specifications of the design problem. The input to the system is a graph of components where the components' design variables are to be determined by a subsequent optimization process. Design goals are often as clearly defined as possible prior to any design effort, which suggests that the objective function can be automatically generated if a system dynamics model is available and the transformation from the system model to objective function can be automated. In this research, automated objective function derivation is demonstrated through automated bond graph modeling and model transformation according to the goals defined by designers. A component (or sub-system) repository is being developed to store not only the component dynamics models, but also various information including typical component design constraints and physical constitutive laws. The paper discusses a systematic approach to automatically prepare a mechatronic design problem for optimization, which can decode and encode proper genotypes of intended design variables, which account for the existing of design constraints and physical constitutive laws. An example of a weighing machine design is used to showcase the approach.

Commentary by Dr. Valentin Fuster
2006;():837-845. doi:10.1115/IMECE2006-16344.

A hybrid approach to active vibration control is described in this paper. It combines elements of both wave and mode approaches to active control and is an attempt to improve on the performance of these approaches individually. In the proposed hybrid approach, wave control is first applied at one or more points in the structure. It is designed on the basis of the local behavior of the structure and is intended to absorb vibrational energy, especially at higher frequencies. Then modal control is applied, being designed on the basis of the modified global equations of motion of the structure-plus-wave-controller. These are now normally non-self-adjoint. Because the higher order modes are relatively well damped, hybrid control improves the model accuracy and the robustness of the system and gives better broadband vibration attenuation performance. Hybrid wave/mode active vibration control is described with specific reference to the control of bending vibrations in a Timoshenko beam. The particular case considered is that of collocated, point force/sensor feedback wave control combined with modal control designed using pole placement. Numerical results are presented.

Commentary by Dr. Valentin Fuster
2006;():847-848. doi:10.1115/IMECE2006-13958.

Composite laminates are used in structural applications such as aircraft wings and tail structures. Drilling holes and making cutouts in these laminates are unavoidable for practical reasons. As a result, stress concentration is introduced near the hole or cutout, and the load-bearing capacity of the structure is reduced. In addition, composite laminates used in aerospace applications are subjected to considerable fatigue loading due to service conditions. In composite laminates, fatigue causes reduction in stiffness and strength. The objective of the present work is to study the combined effect of stress concentration and fatigue on the composite laminate. Since composite laminate displays significant variation in material and strength properties, the stress distribution in the laminate is stochastic in nature. It is more appropriate to analyze the notched composite laminates using a stochastic approach and to design the laminate based on a reliability-based design approach. In the present work, such an approach is developed and the combined effect of stress concentration and fatigue on the reliability of the laminate is investigated.

Commentary by Dr. Valentin Fuster
2006;():849-864. doi:10.1115/IMECE2006-14013.

The problem of the "Free Transverse Vibrations of Orthotropic Composite Mindlin Plates or Panels with a Non-Centrally Bonded Symmetric Lap Joint (or Symmetric Doubler Joint)" is theoretically analyzed and solved with some numerical results. The "Bonded Joint" system is composed of two dissimilar, orthotropic plate "adherends" non-centrally bonded and connected by a dissimilar, orthotropic "doubler" plate through a very thin and elastic adhesive layer. The "adherends" and the single "doubler" are taken into account as the "Mindlin Plates" with the transverse shear deformations and the transverse and the rotary moments of inertia. The adhesive layer is considered as a linearly elastic continuum with the transverse normal and shear stresses. The damping effects are neglected. The dynamic equations of the plate "adherends", the "doubler" plate and the adhesive layer in combination with the stress resultant-displacement expressions, after some algebraic manipulations, are finally reduced to a set of the "Governing System of the First Order Ordinary Differential Equations" in matrix form in terms of the "state vectors" of the problem. The aforementioned set of the "Governing Equations" is integrated by means of the "Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)". Several mode shapes with their corresponding natural frequencies are presented for the "hard" and the "soft" adhesive cases. It was found that there are significant differences in mode shapes and natural frequencies corresponding to the "hard" and the "soft" adhesive cases. Additionally, some parametric studies such as the effects of the "Bonded Joint Length Ratio" and the "Bonded Joint Position Ratio" on the natural frequencies are included in this first study.

Commentary by Dr. Valentin Fuster
2006;():865-874. doi:10.1115/IMECE2006-14512.

In this paper, elastic moduli of both the base metal and weld zone are estimated for aluminum welds by combined experimental/numerical approaches based on vibration testing, static testing and Finite Element (FE) methods. The general approach used is to indirectly determine the elastic properties by combining either experimental modal vibration analysis data or static 3-point bend test data with the corresponding finite element analytical model. Two types of welded joints, A1 6061 arc welded and A1 6111 spot friction welded (SFW) lap joints were considered. Modal vibration characteristics obtained from the experiments were compared with the corresponding FE model results at the macromechanical level, and the weld zone modulus was indirectly determined so as to give the best agreement between predicted and measured modal frequencies. The results indicate a modulus reduction of 15 % to 45 % for the weld zone depending on whether it is two sided or one side arc welded sample, and whether only the first mode or several modes are used, but results are inconclusive for the SFW samples due to uncertainty about modeling of weld zone material and/or geometric properties.

Commentary by Dr. Valentin Fuster
2006;():875-876. doi:10.1115/IMECE2006-14976.

The strength prediction of composites with stress concentrations is concerned with material response in small highly stressed volumes. Direct evaluation of material strength in such areas is difficult to achieve in practice. On the other hand, the ability of such small regions to sustain loads exceeding the average strength measured on uniformly loaded coupons, e.g. ASTM standard for axial strength testing in unidirectional composites, is the foundation of the long standing Whitney-Nuismer point and average stress failure criteria. These criteria postulate that the failure of a composite with stress concentrations occurs when a finite size volume near the stress concentration is loaded at or above the average strength measured on standard test coupons without stress concentrators. The size of this volume constitutes an additional material property. While proving accurate and efficient for capturing the notch size effect on strength within a given laminate family, these dimensions have not found clear physical interpretation and appear not to represent a fundamental material property. The present paper reports results for a Weibull-based integral approach for composite laminates with open holes. The emphasis is on evaluation of the limits of the applicability of the traditional Weibull integral based fiber-direction strength scaling.

Commentary by Dr. Valentin Fuster
2006;():877-878. doi:10.1115/IMECE2006-14987.

One of the more formidable problems in composite research is the study of delamination and other failure modes in the vicinity of a circular hole in a laminate, e.g., a circular cut-out in a structure. In this problem, the singularity varies around the periphery of the hole as well as through the thickness of the laminate. Under tensile loading, the early failure modes in this problem consist of transverse cracks in various layers, so that delamination occurs only after other damage is precipitated, followed by fiber breakage leading to failure. A literature review of past work clearly shows that mechanical testing with simultaneous AE monitoring is a fruitful technique to study damage accumulation in composite systems. The acoustic-ultrasonic (AU) testing combines the high sensitivity of ultrasonics to internal damage and the method of acoustic emission technique to characterize elastic waves. As damage accumulates in the specimen along the wave path, the net internal damping increases and changes the wave parameters such as velocity, peak amplitude, duration, etc. accordingly. Additionally, a range of experimental results over the last decade has further shown that the mechanical deformation and electric resistance of carbon fiber reinforced polymers are coupled, so that the material is inherently a sensor of its own damage state. The monitoring of electric resistance and capacitance changes, linked to the modifications of the conduction paths in the composite, allows the detection of damage growth. It seems logical that a natural extension of these different approaches is the determination of damage mode, e.g., fiber breakage, matrix cracking or delamination, and damage size and position, based on combined measurements from these techniques. These multiple techniques will serve a two-fold purpose, namely, enable comparison as well as complement each other in case of incomplete damage mapping from one set of sensors For this study, we will consider carbon fiber-reinforced toughened bismaleimide, (IM7/5250-4) quasi-isotropic laminate coupons 12" long, 4" wide with hole at the center under tension. Figure 1 shows the damage which occurs around a 0.75" hole in a [45/0/-45/90]s graphite epoxy laminate obtained by radiography after unloading the test specimen from an applied stress of 50 Ksi. The failure stress for this laminate was 56.4 Ksi. Damage in the form of ply cracks in the 90, 45, and -45 plies and delamination around hole edges is clearly evident. The radiograph taken after unloading from a 50 Ksi stress level clearly shows the location and extent of damage, but contains no specific information about the sequence and the timing of damage events. Figure 2 shows stress-strain curves obtained from strain gages mounted at various distances away from the hole edge along with the far-field value. The stress-strain curves provide useful information regarding the initiation as well as the growth of the damage, as evidenced by jump in strain levels and onset of nonlinearity. Damage initiation is first picked up by the strain gage which is mounted closest to the hole edge at a stress level of 21 Ksi. Subsequently, other strain gages begin to sense damage growth as the applied stress level increases. The strain gage data provides useful information regarding initiation, growth and severity of damage, but it is difficult to assign specific damage modes and their location to the measurements. This example clearly demonstrates the needs, with the associated benefits, of the multiple sensor approach. In this work, three different hole sizes (0.25", 0.5" and 0.75") will be investigated. In addition to inherent resistivity measurements, we will also make strain measurements using gages coupled with simultaneous monitoring of AE events and attenuation of elastic waves using piezoelectric transducers and acceleration sensors. This example problem will enable us to examine the combined effects of cut-outs, matrix cracking, delamination and fiber breakage on the ability of various NDE techniques to assess damage. Integrating several nondestructive evaluation (NDE) techniques could provide a solution for real-time health monitoring.

Commentary by Dr. Valentin Fuster
2006;():879-883. doi:10.1115/IMECE2006-15488.

Adhesive joints are increasingly being utilized in joining primary structural components made of fiber reinforced polymer composites (FRP). While adhesively bonded joints transfer loads by means of shear stresses the eccentricity of the load path found in such joints results in the lateral deformation of the joint assembly and the creation of bending moments at the end portions of the adhesive layer. In the case of the single-strap joint, the magnitude of such bending moments can render the joint structurally inefficient. That said, in many practical situations, the single-strap joint leads to be the only feasible joint configuration; therefore, the understanding of its characteristics is of paramount importance. A detailed analytical investigation of the deformations of single-strap joints was carried out to better understand the dependence of edge moments on various parameters influencing the joint capacity and performance. Accurate expressions were also developed for evaluating the magnitude of the bending moment and shear forces at the ends on the adhesive layer. A complete solution is provided that can accurately predict the magnitude of the edge forces in both balanced and unbalanced single-strap joints. The edge forces obtained from the solution can be used as boundary conditions for the complete analysis of shear and peel stresses in the adhesive layer. The analytical expressions of the bending moment and shear forces can also be used to determine the upper and lower bounds of the magnitudes of the edge forces. These limits show that the efficiency of a single-strap joint can be easily made comparable to that of the commonly used single-lap joint. It will also be shown that on the other hand, a carelessly designed single-strap joint can be nothing more than a so-called "built-in stress concentration". The integrity of the analytical expressions was also verified by geometrically nonlinear finite element analysis. The results obtained from the proposed solution showed better agreement to the finite element results than those obtained from the currently available solutions cited in the literature.

Commentary by Dr. Valentin Fuster
2006;():885-890. doi:10.1115/IMECE2006-15490.

Due to their low manufacturing cost, low stress concentration and ease of maintenance, adhesively bonded joints are now one of the most commonly and widely used joining systems in various industrial applications. As the use of composites gains popularity in oil and gas industry, the use of such joints for joining composite pipes is also gaining demand. The design and analysis methodologies applied to these joints under different loading conditions are however non-standard and rather controversial. The inherently complicated equations governing the behaviour of these joints have also impeded their use among the design engineers. As stated, however, as the use of composite pipes gains more popularity in oil and gas industry, the need for standardization of the methodology used for designing such joints becomes more essential. This paper discusses the details of 2D axis-symmetric and full-3D finite element models developed using the ABAQUS commercially available FEM software [1] for modeling and characterizing a series of adhesively bonded tubular joints used in isotropic and orthotropic pipes. The parametric script module of ABAQUS was used to systematically investigate the influence of several design parameters (such as the adhesive thickness, joint length, joint diameter, pipe material, and loading conditions), which govern the performance of such joints. The influence of various parameters specific to composite pipes (including the effect of laminate stacking sequence) was also investigated. Generated from the investigations was a set of useful design curves that provide the relationships among the parameters governing the behaviour of the joints. An important feature of the approach is its ability to establish the most optimized and effective joint length. The integrity of the optimization procedure was evaluated by comparing the response of the joints designed based on the developed design curves with those analyzed in detail by the finite element method (FEM).

Commentary by Dr. Valentin Fuster
2006;():891-893. doi:10.1115/IMECE2006-13184.

Using the design factors is a traditional method in solid mechanics design. This method is still also the base of some design standards in the world [1,2].In this paper, a modification has been performed to traditional Von Misses stress check method for the calculation of sub sea pipeline free spanning. The DNV OS F101 which is a well known standard for sub sea pipelines has been used for calibration [3]. A spread sheet type program for free span calculation has been developed for "Force Model" which facilitates the evaluation of the free span length based on the latest DNV proposed method as well as traditional Von Misses stress check. The method statement is the calculation of maximum allowable sub sea pipeline free span, by DNV proposed method and consequently evaluation of allowable stress to result the same free span length in Von Misses traditional method. The design factors which are the Stress Factors (SF) will be calculated by the ratio of existing equivalent Von Misses stress to yield strength of the pipeline material (fy) .

Topics: Design , Pipelines , Seas
Commentary by Dr. Valentin Fuster
2006;():895-903. doi:10.1115/IMECE2006-13239.

Snap-fit integral attachments are used widely for joining plastic parts. The proliferated use of integral attachment in the form of snap-fit features in designs is due to the ability to mould such parts of great complexity at little cost. The exceptional diversity of part geometry and integral snap-fit features has made it seem that design possibilities may be unlimited. Thus, attempts at optimization might be intractable. A design of experiments (DOE) approach coupled with three-dimensional, geometrical non-linear finite element analysis (FEA) was used to calculate the insertion and retention responses on such parts for various geometrical parameters like length, width and angles. A statistical technique was employed to formulate empirical relationships among the geometrical dimensions, to investigate the effect of these parameters on the design as well as to obtain optimal insertion and retention forces or strains. Design equations obtained from this methodology were verified within the DOE domain and it was observed that the predicted responses were ranged within 30% of the FEA results. During this investigation, it was observed that geometrical features of a block, which exert force on the snap-fit features, have a considerable effect on the results. Therefore, the effects of the block parameters on the various responses were also studied. An attempt was also made to understand the effect of the block parameters such as corner radius and thickness on the design formula, which depicts the geometrical parameters of the snap-fit part as a function of insertion and retention forces. It is expected that the results help to find optimal design parameters in order to enhance the performance of such snap-fit features.

Commentary by Dr. Valentin Fuster
2006;():905-910. doi:10.1115/IMECE2006-13424.

Fatigue prediction of a three-dimensional mechanical component under dynamic load is critical for mechanical design. In this paper, computer simulation of three-dimensional dynamic stress followed by fatigue calculation was performed on a spur-gear pair using finite element modeling. Starting from gear pair geometry and operating conditions, the time histories of the dynamic loads and multi-axial stresses for a complete working cycle of a gear tooth were computed, and then post processed to produce fatigue strength information. Along with certain material properties obtained from experiments, this computer simulated fatigue design provides a useful tool for predicting fatigue failure of mechanical components.

Commentary by Dr. Valentin Fuster
2006;():911-918. doi:10.1115/IMECE2006-13429.

Warpage is one of the most common defects of a plastic product in the polymer injection molding process. It is attributed to the differential shrinkage after the part is ejected from the die cavity due to the nonlinear material property of the polymer, improper design of the cooling system, geometry of the part and the related process parameters. In this paper, the warpage formation of a plastic part, Step Pad of polypropylene copolymer, in the cooling stage of the polymer injection molding process was simulated by finite element analysis (FEA). A three-dimensional FEA model, taking into account the nonlinear material (polypropylene copolymer) properties, with a thermal-structural sequential coupled approach of higher computing efficiency was developed. The effects of mold closed time and layout of cooling system on the dimension and shape of the part were investigated. Industrial experiments for the different mold closed times (25s, 30s, 35s, 40s, 45s, 50s, and 55s) were conducted. The simulation results were compared with the experimental results. The approach is effective in predicting warpage in the polymer injection molding processes.

Commentary by Dr. Valentin Fuster
2006;():919-929. doi:10.1115/IMECE2006-13454.

Concepts of equivalent adhesive-layer and Theory of Duality of Damage (TDD) are presented. Basic idea of the TDD is to assume that material damaged consists of two parts, i.e., Relative Non-Damaged Part (RNDP) and Complete Damaged Part (CDP). The mechanical behaviors of the material damaged can be simulated simultaneously by both mechanical behaviors of the RNDP and the CDP. The RNDP can be simulated by linear-elasticity and non-linear elasticity, respectively. The CDP can be approximately determined in engineering significant. Observed stress-strain relation of the equivalent adhesive layer of a steel/steel butt joint is measured. Evolution equation of damage of the equivalent adhesive-layer is established, and increment equation of stress-strain including effect of damage is given. The observed stress-strain relation is predicted through four damage parameters, i.e., plastic strain trajectory, plastic strain energy density, total strain trajectory, and total strain energy density. As a result, it is shown that the stress-strain curves predicted are of consistence with the observed stress-strain curve. The result predicted using total strain trajectory is better than others. It should be pointed out that the method presented in this paper could be applied to a variety of damaged structures not only to the equivalent adhesive-layer.

Commentary by Dr. Valentin Fuster
2006;():931-937. doi:10.1115/IMECE2006-13641.

This paper deals with a two-dimensional stress analysis of adhesive butt joints filled with elastic circular fillers in an adhesive subjected to an external tensile load. Similar adherends and an adhesive bond are replaced with finite strips in the analyses. Stress distributions in adhesive joints are analyzed exactly using the two-dimensional theory of elasticity. The effects of stiffness and number of fillers on the interfaces stress distributions and around the fillers with higher Young's modulus are shown in the numerical computations. It was seen that as an amount of number of fillers increased, the strength of joints was able to be more improved than that of the joints without a filler. For verification, experiments were carried out to measure the strains. The analytical results are in fairly good agreements with the experimental ones. In addition, for verification of the interface stress distribution, the analytical results are also compared with those obtained from the two-dimensional and three-dimensional FEM calculations. Fairly good agreements are seen between the analytical and the two-dimensional FEM results. However, the result from the present analysis is different from that of the three-dimensional FEM.

Commentary by Dr. Valentin Fuster
2006;():939-944. doi:10.1115/IMECE2006-13682.

3D parametric design functionality of modern CAD systems offers the possibility to create some higher level standards for components or systems. Instead of picking out several of the many variants of a certain product class and declaring them standard, a family of variants is created which can be adapted to different requirements by adjusting a few parameters. The standard is represented by design rules especially by the relations between the dependent and the lead parameters. The challenging work is to create these relations, called the parameter model.

Commentary by Dr. Valentin Fuster
2006;():945-950. doi:10.1115/IMECE2006-13836.

The reduction in axial tension was investigated in bolted joints, which comprise two hot-rolled steel plates and a carbon steel tube sandwiched between the plates. After tightening the bolts, vibration tests were carried in the following two cases. In the first case, flat-faced steel tubes without having any serrations on both ends of the tube were used, and the effect of wave profiles of the external load was investigated. These wave profiles are those of random waves, quasi-random waves that are obtained by only eliminating random waves with small amplitudes, and 7-step programmed waves generated from random waves. In each test, the maximum and the minimum amplitudes are the same. In the other case, the effect of the convex height of the serrations, which are cut on the end face of a tube, was investigated. In addition to the flat faces, the end faces of the tubes were serrated with three different heights for the purpose of comparison. In this case, the vibrations were applied only by means of sinusoidal waves. The effect of the wave profile on the external load is as follows. During the period of low cyclic loading, the bolt axial tension was reduced in the following order: the reduction was the minimum for the 7-step programmed waves, followed by the quasi-random waves, and was maximum for the random waves. As the number of cycles increases, the scattering range of bolt axial tensions corresponding to three types of waves becomes smaller. Furthermore, a comparison of this result with a fatigue test on mild steels indicates that the vibrating wave affects the reduction in axial tension, this is evident from the wave profiles and frequency. With regard to the convex height of the serration, after 106 cycles, the data shows that the lower the convex height, smaller is the reduction in the axial tension. The value of relative micro-slippage of the contact surfaces between the carbon steel tube and the steel plates is small at the sharp serrations. Therefore, the reduction in the axial tension is assumed to be mainly due to the cumulative effect of the plastic deformations.

Commentary by Dr. Valentin Fuster
2006;():951-960. doi:10.1115/IMECE2006-13983.

The initial damage and fracture zone are determined by the approach of coupling analysis of fracture mechanics and damage mechanics. An optimum fiber content of 0.2% in the asphalt concrete is proposed in comparison of the results obtained from composite theory with that obtained from the splitting tests. Crack growth with number of load cycles and fiber mass fraction of asphalt concrete pavement in which an initial surface crack of 4 cm length is included under cyclic temperature loading (-15°C) is simulated using damage mechanics theorem. By computing fatigue life, a new type of fiber-reinforced asphalt concrete pavement is developed.

Commentary by Dr. Valentin Fuster
2006;():961-966. doi:10.1115/IMECE2006-14232.

Scarf adhesive joints used in practice. However, the stress distributions and the joints strengths have not yet been fully elucidate. Important issues are how to determine the scarf angle in adherend and how to determine the adhesive properties. In this study, the stress distributions in scarf adhesive joints under static tensile loadings are analyzed using three-dimensional finite-element calculations. In the FEM calculations, the effects of Young's modulus of the adhesive, adhesive thickness, scarf angle of the adherend on the stress distributions at the adhesive interfaces are examined. The maximum principal stresses were calculated at every element at the interfaces. As the results, it is found that the maximum value of the maximum principal stress occurs at the edge of the adhesive interfaces (z=0, 1/s=1). It is also observed that the maximum value of the stress is the smallest, when the scarf angle is 60 degree. In addition, the joint strength is estimated using the interface stress. For the verification of the FEM calculations, the experiments were carried out to measure the strengths and the strains in the joints under static tensile loadings using strain gauges. Fairly good agreements are observed between the numerical and the measured results concerning the joint strength and the strains.

Commentary by Dr. Valentin Fuster
2006;():967-975. doi:10.1115/IMECE2006-14250.

The contact gasket stress distributions of rectangular box-shape flange connections with compressed joint sheet gaskets subjected to internal pressure were analyzed taking account hysteresis of the gaskets using finite element method (FEM). Leakage tests were also conducted using actual rectangular box-shape flange connections with compressed joint sheet gaskets under internal pressure. By using the contact gasket stress distributions and the results of the leakage tests, the new gasket constants were calculated. The difference in the new gasket constants between the values obtained from the present study and those by the PVRC procedure was substantial. In addition, a method to determine the initial clamping bolt force (bolt preload) for a given tightness parameter was demonstrated.

Commentary by Dr. Valentin Fuster
2006;():977-985. doi:10.1115/IMECE2006-14402.

Long span, unsupported, continuous steel band saw blades are commonly used for cutting in a number of industries worldwide. A model of the stresses generated in the blade under several loading scenarios are developed and used to evaluate the potential for fatigue failure with different support pulley and blade designs. Torsional blade stability is modeled and used to determine the critical in-plane cutting force above which the blade will twist. The effects of blade thickness and tension on stability are examined. Results indicate that stability can be improved with increasing thickness and tension at the expense of fatigue life. For spans greater than 1.5m, blade tensions required for stability are not practical, and suggest that a blade guide is necessary to achieve required cutting forces.

Commentary by Dr. Valentin Fuster
2006;():987-1000. doi:10.1115/IMECE2006-14416.

A new power impact tool design has been developed and tested using advanced engineering polymers to replace traditional metal components. The new polymer-metal impact mechanism generates less noise, lower vibrations, and potentially reduces biomechanical injuries. Power tools are known to cause several medical ailments including Hand-Arm Vibration Syndrome (HAV), Raynaud's phenomenon, and Vibration White Finger unless the daily exposure and/or dosage is limited. To evaluate the effects of a polymer-metal impact mechanism on tool performance, a non-linear model describing the equations of motion and resulting output forces were developed. In addition, a number of experiments with a high frequency Instron test machine and prototype tools were performed to validate the model and compare performance of conventional power tools to the new polymer based design. The results show that although adding a polymer does reduce noise and vibration, the reduction in impact force is relatively small and statistically insignificant. Various polymer materials and shapes were evaluated and results show that for durability and performance, the optimum appears to be a plug inserted in a cavity in either the piston or the cutting tool, thus creating a state of confined compression on the polymer. The polymer used in this research was Minlon® (mineral reinforced Nylon66), and durability was improved when the polymer inserts were cycled with compressive loads before use in the power tool.

Commentary by Dr. Valentin Fuster
2006;():1001-1005. doi:10.1115/IMECE2006-14788.

For suspension components, bench testing for strength is mostly accomplished at component level. However, replicating loading and boundary conditions at the component level in order to simulate the suspension system environment may be difficult. Because of this, the component's bench test failure mode may not be similar to its real life failure mode in vehicle environment. A suspension system level bench test eliminates most of the discrepancies between simulated component level and real life vehicle level environments resulting in higher quality bench tests yielding realistic test results. Here, a suspension level bench test to estimate the strength of its trailing arm link is presented. A suspension system level nonlinear finite element model was built and analyzed using ABAQUS software. The strength loading was applied at the wheel end. The analysis results along with the hardware test correlations are presented. The reasons why a system level test is superior to a component level one are also highlighted.

Commentary by Dr. Valentin Fuster
2006;():1007-1012. doi:10.1115/IMECE2006-15008.

Asymmetric gear teeth are used to improve the performance of gears by increasing the load capacity or by reducing vibrations. Recently these types of gears have found application in MEMS devices where the use of gears is on the rise. In this research a probabilistic computer program, in conjunction with a commercially available finite element program, is developed and the reliability of the asymmetric gear tooth is studied. Specifically, the probability of failure of the asymmetric gear is extracted for various parameters. The parameters considered included pressure angle, tooth height, and contact ratio. The efficacy of using asymmetric gear tooth is shown in this study.

Commentary by Dr. Valentin Fuster
2006;():1013-1020. doi:10.1115/IMECE2006-15122.

It is proposed to use ceramic high temperature heat exchanger as a sulfuric acid decomposer for hydrogen production within the sulfur iodine thermo-chemical cycle. The decomposer is manufactured using fused ceramic layers that allow creation of channels with dimensions below one millimeter. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer, stresses and chemical reactions in the decomposer. Fluid, thermal and chemical reaction analyses are performed using FLUENT software. Temperature distribution in the solid is imported to ANSYS software and used together with pressure as the load for stress analysis. Results of this research can be used as a basis for investigation optimal design of the decomposer that can provide maximum chemical decomposition performance while maintaining stresses within design limits.

Commentary by Dr. Valentin Fuster
2006;():1021-1028. doi:10.1115/IMECE2006-15675.

Electronic components within a projectile are subjected to severe loads over extremely short duration. Failure of these components is likely to have negative implications to the projectile or mission. While experimental data can be helpful in understanding the failure phenomena, collecting such data is usually difficult. There are also limitations on the reliability of sensors under these circumstances. Finite element modeling (FEM) can offer a means to better understand the behavior of these components. It can also be used to design better techniques to mitigate the shocks these components are subjected to. A model of a typical projectile and the gun barrel is presented. The projectile is modified to include a payload of a one-pound mass that represents a typical electronic package, which is supported by a plate. The model, which is subjected to a realistic launch pressure-time history, includes the effects of friction between the gun barrel inner surface and the projectile. The effect of the flexibility of the gun barrel on the vibrations of the electronic package is also considered. This paper proposes using a composite plate, with carbon fibers embedded in an epoxy matrix, to reduce the shocks transmitted to the payload. A parametric study of the effects of varying the thickness of the supporting plate and the fiber volume fraction on accelerations and stresses is included.

Commentary by Dr. Valentin Fuster
2006;():1029-1038. doi:10.1115/IMECE2006-15685.

Gun-fired projectiles are subjected to severe loads over extremely short duration. There is a need to better understand the effects of these loads on components within a projectile. While experimental data can be helpful in understanding projectile launch phenomena, collecting such data is usually difficult. There are also limitations on the reliability of sensors under these circumstances. Finite element modeling (FEM) can be used to model the projectile launch event. Currently, engineers usually use large number of elements to accurately model the projectile launch event, which results in an extremely long computational time. FEM results in these cases are always subject to questions regarding accuracy of the results and proof of mesh stability This paper presents an expert system that can reduce computational time needed to perform FEM of gun-fired projectiles. The proposed approach can result in reducing computational time while ensuring that accuracy of results is not affected. Recommendations of the expert system are reached through two stages. In the first stage, an equivalent projectile with simple geometry is created to reduce the complexity of the model. In the second stage, parameters controlling mesh density of the equivalent projectile are used as variables in an optimization scheme with the objective of reducing computational time. Accuracy of the acceleration results from an optimized model with respect to a model with an extremely fine mesh is used as an inequality constraint within the optimization search. A projectile model meshed with aspect ratios obtained from the optimization search produces good agreement with the finite element results of the original densely-meshed projectile model while significantly reducing computational time. It is anticipated that this approach can make it easier to conduct parametric analysis or optimization studies for projectile design.

Commentary by Dr. Valentin Fuster
2006;():1039-1051. doi:10.1115/IMECE2006-15959.

This paper investigates the kinetic and static frictional torque components in threaded fasteners during the initial fastener tightening, subsequent torque audit, as well as during the loosening of previously tightened bolts. In less critical applications, the peak kinetic torque value is often used for predicting the bolt preload. The peak value of the tightening torque and its frictional components are mainly determined by the kinetic friction coefficients between the engaged threads and between the rotating nut (or head) and the joint surface. During subsequent quality inspection of the joint after its initial assembly, an audit residual torque value (in the tightening direction) is often used for predicting the residual fastener tension and joint clamp load, as well as for predicting the stability of the clamp load. In contrast with the peak kinetic torque, the audit torque and its thread and under head/nut frictional components are mainly determined by the static friction coefficients. In some cases, the careful application of a breakaway torque in the loosening direction (loosening torque) may be used as a measure for the residual clamp load; similar to the quality audit torque, the loosening torque is determined by the static friction coefficients of the bolted system. An experimental procedure and test set up are proposed to investigate the effect underhead contact radius, thread pitch, surface coating, and fastener head versus nut side tightening on the static and kinetic frictional torque components.

Topics: Torque , Fasteners
Commentary by Dr. Valentin Fuster
2006;():1053-1062. doi:10.1115/IMECE2006-15977.

This study provides an experimental and theoretical investigation of the effect of hole clearance and thread fit on the self-loosening of tightened threaded fasteners that are subjected to a cyclic transverse service load. An experimental procedure and test set up are developed in order to collect real-time data on the rate of clamp load loss per cycle as well as the loosening rotation of the bolt head. Three levels of hole clearance are investigated; namely, 3%, 6%, and 10% of the bolt nominal diameter. For the commonly used 2A thread fit for a selected bolt size, three classes of the nut thread fit are considered; namely, 1B, 2B, and 3B. A simplified mathematical model is used for the analytical investigation of the effect of the hole clearance and thread fit on threaded fasteners self-loosening. The experimental and theoretical results are presented and discussed.

Commentary by Dr. Valentin Fuster
2006;():1063-1072. doi:10.1115/IMECE2006-16002.

In this paper, a nonlinear combined stress model is established for a typical bolted joint for the purpose of studying its behavior under a separating service load. The combined effect of axial and torsional stresses in the tightened threaded fastener is considered. A new approach for the analysis of the clamping force loss is proposed under different pre-tightening with different thread friction coefficient and different separating loading. The_nonlinear model is established based on the elasto-perfectly plasticity in order to describe the fastener behavior over the yielding of its material, and to determine the relationship between the axial bolt force and elongation under tightening and the separating loading with specific twist angle, and to predict the clamp force loss due to the permanent set in the fastener after the separating force has been removed. The nonlinear relationship between the bolt axial force and the bolt elongation depends on the initial twist angle and the tightening preload. Finally, the effects_of the fastener pre-tightening, the initial twist angle and the bolt and joint members' elastic properties on the amount of clamp load loss are investigated.

Commentary by Dr. Valentin Fuster
2006;():1073-1080. doi:10.1115/IMECE2006-16150.

In this paper, the evolution equations of the bearing and thread friction coefficients are proposed based on mechanical behavior of the bolted joint assembly. The formulation of the torque-tension relationship during tightening and loosening is experimentally validated. The study shows excellent correlation between the proposed model and the experimental results for the breakaway torque values in both the tightening and loosening directions. Evaluation of the torque-angle control of the tightening process is made, and a modified torque-angle control approach is proposed. The effect of friction coefficients on the error in the clamping force prediction is analyzed.

Topics: Torque , Fasteners
Commentary by Dr. Valentin Fuster
2006;():1081-1091. doi:10.1115/IMECE2006-16185.

This study provides an experimental and theoretical investigation of the effect of the bearing friction coefficient and the thread friction on the self-loosening of threaded fasteners that are subjected to cyclic transverse service loads. Coating and lubrication affect the thread and the underhead friction of the fastener, which affects the loosening rate when it is subjected to transverse loads. A mathematical model was developed to evaluate the self-loosening behavior in threaded fasteners when subjected to cyclic transverse loads. An experimental procedure and test set up are designed in order to collect real-time data on the rate of preload loss per cycle as well as the rotational angle of the bolt head during its gradual loosening. The values of the coefficients of friction under the bolt head and between the threads were changed in the mathematical model to monitor their effect on the loosening rate. Experimentally, the friction coefficients are modified by changing the coating or the lubrication applied to the fasteners. One coating and one solid film lubricant are used, namely, phosphate and oil coating and Olefin and Molydisulfide lubricated bolts. The theoretical and experimental results are presented and discussed.

Commentary by Dr. Valentin Fuster

Computers and Information in Engineering

2006;():1095-1104. doi:10.1115/IMECE2006-13160.

For mechanical transmissions, CAD systems provide flexibility and tools that can be used to perform analysis on components and to measure their performance even before they are manufactured. This paper represents an analytical study on a novel type of worm-face gear drive in which the worm is of duplex ZK-type. Such a gear set has two teeth flanks with different pitches, that facilitate stepless compensation of the tooth flank backlash or wear by means of the simple readjustment of the worm shaft. It can be used in applications that require an exact and even transmission of rotary movements or exact maintenance of a specific defined position, beside a high gear ratio in a compact space, high-load and shock capability, and reduced operating noise. The study was limited to mathematical modeling and numerical simulation of a gear set generation process using a novel 3D CAD simulation method. The method, suitable for the manufacturing process simulation of any type of gears provides a virtual 3D visual output with the ability to validate, within the precision limits of the CAD software, the accuracy of the calculation results. Some numerical examples showing 3D CAD teeth generation simulation of a duplex worm-face gear drive are presented. Numerical results relating to the analysis of virtually generated gear-set components are also provided in order to illustrate the developed theory.

Commentary by Dr. Valentin Fuster
2006;():1105-1112. doi:10.1115/IMECE2006-13471.

The Thin Plate Splines (TPS) theory is modified and employed in the reconstruction of 2D 1/2 unfolded micro-topographical surfaces. The modified TPS allows the reconstruction of MEMS structures based on sampled digital elevation model (DEM). The developed algorithms are implemented in MATLAB and applied to restore bad samples, enhance surface reconstruction, and compensate for surface irregularities for micromachining purposes. In addition, the restored surface reveals the scale components of the real surface (roughness, waviness and form). The irregularity of meso, micro and nano surfaces is then characterized into slope, curvature, strike, dip, azimuth and energy surfaces. It is concluded that the simplicity, differentiability of TPS and roughness components relaxation make the proposed theory advantageous on reconstruction and characterization of micro surfaces for a variety of applications.

Commentary by Dr. Valentin Fuster
2006;():1113-1119. doi:10.1115/IMECE2006-13642.

Product data management (PDM) systems have been successfully applied to maintain product-related information as well as to integrate different applications for design, process and manufacturing throughout the product life cycle. However, the issues on how to use the PDM system to enable design automation have not been adequately addressed. This paper proposed a framework to enable product design automation by employing the web-based PDM system and the Computer-aided Design (CAD) platform. The components of the framework include a feature-based parametric template module, 3D and 2D auto-generation modules, a web-based PDM system, and the data communication protocol between PDM and CAD platform. The features and relations for product families can be defined with the parametric module. 3D and 2D modules help to auto generate the solid and 2D drawings based on the features and relations of the product. The web-based PDM system provides the easy access for designer to create or edit or store the product feature information, and manage the workflow process. The illustrating example demonstrates the feasibility and effectiveness of this proposed framework for design automation.

Commentary by Dr. Valentin Fuster
2006;():1121-1129. doi:10.1115/IMECE2006-13820.

This paper presents a study on physically based modeling and simulation of soft tissue deformation, with the goal of producing realistic, real-time effects during the simulation. We consider soft tissue deformation as a solid mechanics problem with a linear elastic constitutive law. A point collocation based meshfree method is employed to solve the governing equations. To achieve real-time performance, an octree data structure is used to organize the support sets and the nodes to expedite the computation in the meshfree method. The developed system brings together the surface representation for visualization and meshfree modeling for physically based animation to set up a virtual reality environment for soft tissue surgery simulation.

Commentary by Dr. Valentin Fuster
2006;():1131-1139. doi:10.1115/IMECE2006-14315.

As the demand on productivity in the manufacturing industry increases, it's important with tools that shorten the time from concept to production. Visualization has become a popular tool for fast and easy verification regarding many aspects of products in the design phase. In this paper an algorithm is developed to calculate and visualize the total volume in space a part or assembly creates when it is affected by displacement or motion. The algorithm is general and works on all kinds of problem where there is variation or motion involved. The data used to create the total volume is either collected from simulation data or from real measurement data. This paper includes an introduction and background to the problem and a deep explanation of the suggested algorithm. Finally the algorithm is used to visualize the motion envelope of a car engine based on real measurement data. The data and engine is collected from a well known car manufacturer. The result shows that the suggested method for visualization is useful in early phases for design, packaging and tolerance analysis.

Commentary by Dr. Valentin Fuster
2006;():1141-1148. doi:10.1115/IMECE2006-14332.

This paper is mainly concerned with the simulation of a four-stroke SI engine processes. To this effect a numerical approach has been followed and this has resulted in the development of a software by the name GANESH. It is an acronym that stands for G raphical A nd N umerical E ngine S oftware H ub. The results are obtained by solving appropriate process governing equations and presented in the form of animated graphs and data. The software is developed using Visual C++ and OpenGL. The proposed approach for analysis involves step-by-step procedure in developing various models. For a four-stroke spark ignition engine, ideal Otto cycle provides the foundation. Assuming fuel-air mixture as working fluid modifies the analysis bringing fuel into account. This allows fuel vaporisation effect as well as instantaneous adiabatic combustion. Intake and exhaust stroke is modeled in a simplified manner. As a next step the progressive combustion analysis has been carried out. To determine burning rate three empirical models are considered in the analysis. The intake and exhaust stroke analysis are modelled by taking into consideration gas exchange process. Detailed gas exchange analysis tries to determine exact mass of the working fluid at the start of the compression stroke. The heat transfer between the working fluid and cylinder surface is by forced convection which is taken care of by empirical correlations. Empirical relations available in the literature are used to determine the loss due to friction. Thus all processes involved in a four-stroke SI engine are simulated and the user friendly software can be used with ease and it will be particularly useful for getting results which will reduce the development time.

Commentary by Dr. Valentin Fuster
2006;():1149-1157. doi:10.1115/IMECE2006-14333.

Most of the companies still use the old or traditional practice for generating the NC code for machining as opposed to automated NC code generation, because they either lack the CAD/CAM technology or suffer from a gap between CAD/CAM (or CAM) and CNC machining. That leads to a missing link between the design department and the manufacturing department (or shop floor). The primary objective of this work is to create an integrated manufacturing environment in which a part would be designed using a standard available CAD system. The design is saved in a CAD file has standard format (STEP, ISO 10303). Feature extraction system is developed and used to extract out machining or manufacturing features. Artificial Intelligence (AI) and knowledge-based systems are developed based on 'Agent Technology'. The agents are programmed to accomplish various activities such as selecting machine types, cutting tools and cutting parameters to machine specific geometries or features. Then, feature data is saved in a in a STEP-NC (ISO14649) file, which can be transmitted between various locations and CAX systems. They are used for information retrieval, data exchange, and decision-making support. So, product data and information is available to shop floor and machine tool in addition to CAD/CAM systems.

Topics: Manufacturing , Design
Commentary by Dr. Valentin Fuster
2006;():1159-1163. doi:10.1115/IMECE2006-14362.

The implementation of a virtual engineering system at John Zink Company, LLC is starting to change the engineering and development processes for industrial combustion equipment. This system is based on the virtual engineering software called VE-Suite being developed at the Virtual Reality Applications Center (VRAC) of Iowa State University. The goal of the John Zink virtual engineering system is to provide a virtual platform where product design, system engineering, computer simulation, and pilot plant test converge in a virtual space to allow engineers to make sound engineering decisions. Using the virtual engineering system, design engineers are able to inspect the layout of individual components and the system integration through an immersive stereo 3D visualization interface. This visualization tool allows the engineer not only to review the integration of subsystems, but also to review the entire plant layout and to identify areas where the design can be improved. One added benefit is to significantly speed up the design review process and improve the turn around time and efficiency of the review process. Computational Fluid Dynamics (CFD) is used extensively at John Zink to evaluate, improve, and optimize various combustion equipment designs and new product development. Historically, design and product development engineers relied on CFD experts to interpret simulation results. With the implementation of the virtual engineering system, engineers at John Zink are able to assess the performance of their designs using the CFD simulation results from a first person perspective. The virtual engineering environment provided in VE-Suite greatly enhances the value of CFD simulation and allows engineers to gain much needed process insights in order to make sound engineering decisions in the product design, engineering, and development processes. Engineers at John Zink are now focusing on taking the virtual engineering system to the next level: to allow for real-time changes in product design coupled with high-speed computer simulation along with test data to optimize product designs and engineering. It is envisioned that, when fully implemented, the virtual engineering system will be integrated into the overall engineering process at John Zink to deliver products of the highest quality to its customers and significantly shorten the development cycle time for a new generation of highly efficient and environmentally friendly combustion products.

Topics: Combustion
Commentary by Dr. Valentin Fuster
2006;():1165-1173. doi:10.1115/IMECE2006-14459.

Currently, mechanical design of aero engine structural components is defined by dimensioning of Design Parameters (DP's) to meet Functional Requirements (FR's). FR's are typically loads, geometrical interfaces and other boundary conditions. Parameters from downstream processes are seldom actually seen as DP's. This paper proposes that downstream process parameters are treated as DP's which calls for engineering methods that can define and evaluate these extended set of DP's. Using the proposed approach manufacturing process alternatives can be used as DP's in early stages of product development. Both the capability to quantitatively assess impact of varying manufacturing DP's, and the availability of these design methods are needed to succeed as an early phase design method. One bottleneck is the preparation time to define and generate these advanced simulation models. This paper presents how these manufacturing process simulations can be made available by automating the weld simulation preparation stages of the engineering work. The approach is based on a modular approach where the methods are defined with knowledge based engineering techniques-operating close to the CAD system. Each method can be reused and used independently of each other and adopted to new geometries. A key advantage is the extended applicability to new products, which comes with a new set of DP's. On a local level the lead time to generate such manufacturing simulation models is reduced with more than 99% allowing manufacturing process alternatives to be used as DP's in early stages of product development.

Commentary by Dr. Valentin Fuster
2006;():1175-1183. doi:10.1115/IMECE2006-14483.

In this study, product information models of two different companies both developing advanced mechatronic products are described, compared, and implemented in demonstrators. This has been done in order to investigate to what extent currently available PLM systems can manage this integration. The study shows that requirements for mechatronic product data are rather similar in the two companies. Differences involve the amount of product data generated in a development project, but there are also other differences related to development traditions. The contribution of the study is an evaluation of how integrated information models for mechatronic development can be managed in PLM systems. It is concluded that this can be done, however this requires a modified approach to software engineering.

Commentary by Dr. Valentin Fuster
2006;():1185-1195. doi:10.1115/IMECE2006-14531.

Miniaturization, high reliability and low manufacturing costs require close spatial integration of mechanics and electronics. New production technologies such as MID (Molded Interconnect Devices), with which spatial electronic circuit carriers can be manufactured, offer intriguing possibilities. However, these production technologies already determine the product concepts. The product and the production system development must be interrelated. This development will be shown through the example of a miniature robot. The miniature robot is supposed to be manufactured in large quantity. It is to act as an experimental object for swarm intelligence and multi-agent applications of computer science, as well as using the Technology MID. A new methodology is necessary for the design of systems with MID. This paper describes first a procedural model for the integrated design of 3-D molded interconnect devices. And then it presents the specification techniques for the constant cross-domain description of such systems, from the principal solution to prototypes. The procedure and the application of the specification techniques are shown through the example of the housing of an autonomous miniature robot.

Topics: Robots , Design , Circuits
Commentary by Dr. Valentin Fuster
2006;():1197-1210. doi:10.1115/IMECE2006-14535.

An important element of successful engineering design is the effective management of resources to support design decisions. Design decisions can be thought of as having two phases—a formulation phase and a solution phase. As part of the formulation phase, engineers must decide which models to use in support of design decisions. Although more accurate models typically lead to better decisions, they also cost more. The question therefore is: Which model provides the best cost-benefit trade-off? In this paper, we focus in particular on the situation in which the systematic error in the models can be bounded by an interval. Based on principles of information economics, the interval-based model error results in bounds on the expected economic value of using a particular model in support of a certain design decision. The decision maker can then select the model that provides the best overall value, considering both the expected benefits resulting from the decision and the cost of the decision-making process. The approach is illustrated with the design of an I-beam structure.

Commentary by Dr. Valentin Fuster
2006;():1211-1218. doi:10.1115/IMECE2006-15323.

The ASME Y14.41-2003 standard for Digital Product Definition Data Practices provides for representation of design data as an entirely digital package. One central requirement of the standard is storage of all design content, especially annotations, directly in the 3D model. Companies maintaining a library of models and drawings in their chosen CAD system will benefit from being able to quickly and reliably transfer drawing annotations into 3D models. This paper describes the design and development of a prototype conversion tool that will be capable of automatically converting existing drawing annotations into ASME Y14.41-2003 compliant 3D model annotations. The paper covers the mathematical formulation used for transfer of annotations from the drawing to the 3D model and the abstract software development model for the base classes and conversion algorithm. The paper presents examples for how the conversion tool was implemented within a commercial CAD system.

Commentary by Dr. Valentin Fuster
2006;():1219-1225. doi:10.1115/IMECE2006-15844.

Recently online prediction of plate deformations in modern systems have been considered by many researchers, common standard methods are highly time consuming and powerful processors are needed for online computation of deformations. Artificial neural networks have capability to develop complex, nonlinear functional relationships between input and output patterns based on limited data. A good trained network could predict output data very fast with acceptable accuracy. This paper describes the application of an artificial neural network to identify deformation pattern of a four-side clamped plate under external loads. In this paper the distributed loads are approximated by a set of concentrated loads. An artificial neural network is designed to predict plate deformation pattern under external forces. Results indicate a well trained artificial neural network reveals an extremely fast convergence and a high degree of accuracy in the process of predicting deformation pattern of plates. Additionally this paper represents application of neural network in inverse problem. This part illustrates the capability of neural networks in identification of plate external loads based on plate deformations. Load identification has many applications in identification of real loads in machineries for design and development.

Commentary by Dr. Valentin Fuster

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