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### Applied Mechanics

2010;():1-10. doi:10.1115/ESDA2010-24007.

In the present paper, fundamental frequency optimization of symmetrically angle-ply laminated composite plates is studied using the combination of Elitist-Genetic algorithm (EGA) and finite strip method (FSM). The design variables are the number of layers, the fiber orientation angles, edge conditions and plate length/width ratios. The classical laminated plate theory (CLPT) is used to calculate the natural frequencies of laminated rectangular plates. To improve the speed of the optimization process, the elitist strategy is used in the Genetic algorithm. In the E-GA, the fittest individuals in the generation survive and are automatically reinserted in the next generation, right before the next selection process takes place and the fitness function is computed with a semi-analytical finite strip model developed originally on the basis of full energy method. In addition, from the computational economy point of view, combination of E-GA and FSM provides a much higher convergence and reduced the CPU time. To check the validity, the obtained results are also compared with some other stacking sequences.

Commentary by Dr. Valentin Fuster
2010;():11-15. doi:10.1115/ESDA2010-24021.

The strain rate intensity factor in the theory of rigid perfectly plastic isotropic materials is the coefficient of the principal singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. This coefficient can be used to predict the evolution of material properties in a narrow layer in the vicinity of surfaces where the friction stress is high. Usually, conventional evolution equations are not compatible with the plasticity equations near maximum friction surfaces. It is therefore of interest to extend the theories based on the strain rate intensity factor to more general models than the rigid perfectly plastic isotropic solids. The present paper deals with plane strain deformation of rigid plastic anisotropic material. It is shown by means of a simple analytic solution that the velocity field is singular in the vicinity of maximum friction surfaces. Thus the strain rate intensity factor can be introduced for such materials. An effect of plastic anisotropy on its value is demonstrated. In addition, it is shown that rigid plastic solutions for anisotropic materials can exhibit various types of singularity in the vicinity of maximum friction surfaces, in contrast to isotropic materials where one type only is possible. Nevertheless, in most cases the type of singularity is same for isotropic and anisotropic materials.

Topics: Anisotropy
Commentary by Dr. Valentin Fuster
2010;():17-22. doi:10.1115/ESDA2010-24100.

The paper describes a 2-DOF parallel kinematic machine designed to achieve precise solar tracking. The mechanism has been developed keeping in mind that solar concentration technology requires a precise alignment of photovoltaic modules and sun radiation, with error allowance much lower than those ensured by traditional sun trackers. The paper describes the kinematic structure and discusses its forward and inverse kinematic, providing the tools to design a system that satisfies the requirements for dexterity and workspace.

Commentary by Dr. Valentin Fuster
2010;():23-27. doi:10.1115/ESDA2010-24101.

The present work deals with the vibrational characteristics of a Y-shaped tube conveying flowing fluid. The tube is considered to be composed of 3-stright tube segments mathed at the intermediate junction. The governing equation of straight tube conveying fluid is used with each of the three segments. This work introduce the clamped-pinned and clamped free boundary conditions. The coupled effects of the type of boundary conditions, angle between the two Y-segments, fluid velocity and length ratio of segments on the dynamics of the tube are studied. It seen that the Y-tube loses its stability at flow velocity higher than that for straight tube of the same characteristics.

Topics: Fluids
Commentary by Dr. Valentin Fuster
2010;():29-38. doi:10.1115/ESDA2010-24106.

In the present study, the shear correction factors are obtained for annular sector plates using Differential Quadrature (DQ) Method. Based on the three-dimensional elasticity theory, the governing equations of motion for an annular sector plate are obtained. These equations together with the boundary conditions are discretized by employing DQ method. Following DQ procedure an eigenvalue problem is obtained that represents the natural frequencies and mode shapes of the plate. This procedure is also investigated for the analysis of the annular sector plates based on FSDT. The frequency of the first asymmetric mode of thickness direction for various shear correction factors are compared with the results of the three-dimensional elasticity theory. Therefore, the appropriate shear correction factor can be found. Some shear correction factors are obtained for various boundary conditions. It is shown that the value of the shear correction factor depends on the plate geometry and the boundary conditions.

Commentary by Dr. Valentin Fuster
2010;():39-44. doi:10.1115/ESDA2010-24138.

An accurate approximate closed-form solution is presented for bending of thin skew plates with clamped edges subjected to uniform loading using the extended Kantorovich method (EKM). Successive application of EKM together with the idea of weighted residual technique (Galerkin method) converts the governing forth-order partial differential equation (PDE) to two separate ordinary differential equations (ODE) in terms of oblique coordinates system. The obtained ODE systems are then solved iteratively with very fast convergence. In every iteration step, exact closed-form solutions are obtained for two ODE systems. It is shown that some parameters such as angle of skew plate have an important effect on results. It is shown that the method provides sufficiently accurate results not only for deflections but also for stress components. Comparison of the deflection and stresses at various points of the plates show very good agreement with results of other analytical and numerical analyses. Also, it has been shown that for skew angle less than 30° this method provides more accurate results and when the skew angle becomes greater than 30°, results gradually begin to deviate from those reported using other methods or by finite element softwares.

Commentary by Dr. Valentin Fuster
2010;():45-52. doi:10.1115/ESDA2010-24139.

The electroelastic response of functionally graded piezoelectric cantilever beams which includes the effect of body force is presented in this paper. The material properties such as elastic compliance, piezoelectric and dielectric impermeability are assumed to be graded with different indices in the thickness direction according to exponential distributions. Systems of fourth order inhomogeneous partial differential equations (PDEs) which are satisfied by the stress and induction functions and involve the body force terms are derived. Spectral forms for electrical and mechanical variables in the x-axis are employed to convert the partial differential governing equations and the associated boundary conditions into sets of ordinary differential equations, and the resulting equations are solved in a closed form manner. Subsequently, in numerical studies, the effects of the material property graded indices are examined upon the electroelastic response of FGP cantilever beams under pure body force loadings.

Commentary by Dr. Valentin Fuster
2010;():53-59. doi:10.1115/ESDA2010-24188.

A design method for achieving minimum sound radiation from a beam is presented. The strategy is to form a series of cylindrical dimples on the beam surface in order to make one or more vibration modes of this dimpled beam have the same shape as the weak modes. Consequently, the dimpled beam behaves as a weak radiator when one or more vibration modes are excited. Instead of minimizing the radiated sound power at a specific frequency or in a bandwidth, the objective is to maximize the modal assurance coefficient (MAC) which quantifies resemblance between the vibration mode of a dimpled beam and a weak mode. To perform this strategy, two key issues are addressed in this paper. The first is to determine the so-called weak mode of a beam. And the second is how to determine the required dimple size and the dimple location on this beam so that the dimpled beam may have vibration modes resembled to the weak modes. A methodology to do so based on the finite element method and the mode assurance criteria is proposed. Results show that the radiation efficiency of the dimpled beam after optimization using MAC as the objective is generally lower than the uniform beam. However, the effectiveness of this strategy depends on how close in shape between the vibration mode of the dimpled beam and the designated weak mode.

Commentary by Dr. Valentin Fuster
2010;():61-68. doi:10.1115/ESDA2010-24190.

Quasi-static (∼10−3 s−1 ) and high strain rate (∼850 s−1 ) compression behavior of an E-glass/polyester composite was determined in the through-thickness and in-plane directions. In both directions, modulus and failure strength increased with increasing strain rate. Higher strain rate sensitivity for both elastic modulus and failure strength was observed in the inplane direction. A numerical model was developed to investigate the compressive deformation and fracture of an E-glass/polyester composite. Excellent agreement was demonstrated for the case of high strain rate loading. Also, the fracture geometries were successfully predicted with the numerical model.

Commentary by Dr. Valentin Fuster
2010;():69-72. doi:10.1115/ESDA2010-24202.

Finite element analysis has been used widely in automotive industry to evaluate design alternatives. Especially when there is no prototype part for rig testing; CAE (Computer Aided Engineering) is the only tool to evaluate design whether it meets customer usage profile for the vehicles entire life. Antiroll bar bracket is used in heavy truck suspension which is mounted on the top of front axle & beneath the leaf spring squeezed with U bolts. Bracket has two attachment points for external loadings; antiroll bar & shock absorber. Modeling techniques used in finite element for stress analysis include assembly loads in addition to the external loads. Material & contact nonlinearities have been used for stress estimation. Alternative design is used to decrease stress level; and therefore increase fatigue life of the bracket. Rig testing has been used to determine fatigue life of bracket. Results for finite element & rig testing have been presented.

Topics: Fatigue life , Trucks
Commentary by Dr. Valentin Fuster
2010;():73-80. doi:10.1115/ESDA2010-24206.

Topics: Pressure , Flanges
Commentary by Dr. Valentin Fuster
2010;():81-89. doi:10.1115/ESDA2010-24219.

This paper investigates the dispersion of the torsional wave propagation in the finitely pre-strained bi-material compounded cylinder. This investigation is made within the framework of the piecewise homogenous body model with the use of the three dimensional linear theory of the elastic waves in initially stressed bodies. The mechanical relations of the materials of the components of the cylinder are described by the harmonic potential. The numerical results on the influence of the initial strains on the wave propagation velocity are presented and discussed. It is established in particularly that the initial stretching of the cylinders causes to increase the torsional wave propagation velocity.

Commentary by Dr. Valentin Fuster
2010;():91-98. doi:10.1115/ESDA2010-24230.

This paper investigates some particularities related with the influence of the magnitude of the initial twisting of the axisymmetric wave propagation in the initially twisted circular bi-material compounded cylinder. The investigation is carried out within the scope of the piecewise homogeneous body model with the use of the three-dimensional linearized theory of elastic wave propagation in an initially stressed body. The mathematical formulation of the problem is presented and the corresponding solution method is proposed and developed. The numerical results are further presented and discussed. In particular, the mechanism of the arising of the new type modes caused by the initial twisting of the circular compounded cylinders is established.

Commentary by Dr. Valentin Fuster
2010;():99-106. doi:10.1115/ESDA2010-24257.

The investigated cantilever beam is characterized by a constant rectangular cross-section and is subjected to a concentrated vertical constant load at the free end. The same beam is made by an elastic non-linear asymmetric Ludwick type material with different behavior in tension and compression. Namely the constitutive law of the proposed material is characterized by two different elastic moduli and two different strain exponential coefficients. The aim of this study is to describe the deformation of the beam neutral surface and particularly the horizontal and vertical displacements of the free end cross-section. The analysis of large deflection is based on the Euler-Bernoulli bending beam theory, for which cross-sections, after the deformation, remain plain and perpendicular to the neutral surface; furthermore their shape and area do not change. On the stress viewpoint, the shear stress effect and the axial force effect are considered negligible in comparison with the bending effect. The mechanical model deduced from the identified hypotheses includes two kind of non-linearity: the first due to the material and the latter due to large deformations. The mathematical problem associated with the mechanical model, i.e. to compute the bending deformations, consists in solving a non-linear algebraic system and a non-liner second order ordinary differential equation. Thus a numerical algorithm is developed and some examples of specific results are shown in this paper. Precisely, the proposed problem is a generalization of similar cases in literature, consequently numerical comparisons are performed with these previous works, i.e. assuming linear elastic materials or assuming symmetric Ludwick type material with same behavior in tension and compression like aluminum alloy and annealed copper. After verifying a proper agreeing with the literature, in order to investigate the effect of the different material behavior on the horizontal and vertical displacements of the free end cross-section, numerical results are obtained for different values of elastic moduli and strain exponential coefficients. The arising conclusions are coherent with the assumed hypotheses and with similar works in literature.

Commentary by Dr. Valentin Fuster
2010;():107-115. doi:10.1115/ESDA2010-24340.

This paper describes a study of three-dimensional free vibration analysis of thick circular and annular functionally graded (FG) plates resting on Pasternak foundation. The formulation is based on the linear, small strain and exact elasticity theory. Plates with different boundary conditions are considered and the material properties of the FG plate are assumed to vary continuously through the thickness according to power law. The kinematic and the potential energy of the plate-foundation system are formulated and the polynomial-Ritz method is used to solve the eigenvalue problem. Convergence and comparison studies are done to demonstrate the correctness and accuracy of the present method. With respect to geometric parameters, elastic coefficients of foundation and different boundary conditions some new results are reported which maybe used as a benchmark solution for future researches.

Commentary by Dr. Valentin Fuster
2010;():117-126. doi:10.1115/ESDA2010-24395.

In this paper, the stress analysis of moderately thick functionally graded (FG) sector plate is developed for studying the singularities in vicinity of the vertex. Based on the first-order shear deformation plate theory, the governing partial differential equations are obtained. Using an analytical method and defining some new functions, the stretching and bending equilibrium equations are decoupled. Also, introducing a function, called boundary layer function, the three bending equations are converted into two decoupled equations called edge-zone and interior equations. These equations are solved analytically for the sector plate with the simply supported radial edges and arbitrary boundary condition along the circular edge. The singularities of shear force and moment resultants are discussed for both salient and re-entrant sectorial plates. Also, the effects of power of the FGM, thickness to length ratio on the stress singularities of the FG sector plates are investigated.

Commentary by Dr. Valentin Fuster
2010;():127-134. doi:10.1115/ESDA2010-24452.

The Oberst Beam Method is widely used for the measurement of the mechanical properties of damping materials. This method is a classical method based on a multilayer cantilever beam which consists of a base beam and one or two layers of other materials. The base beam is almost always made of a lightly damped material such as steel and aluminum. If the Oberst Beam Method (OBM) is to be used, it is essential to establish a very accurate measurement methodology. In this respect, the response and the excitation sensors in the Oberst test rig are generally non-contact type. Although the drawbacks of contacting type of transducers are eliminated by this way, there are other critical issues when OBM is used. It is therefore essential to be aware of the parameters that might adversely affect the measured data and also to avoid them as much as possible. Consequently, all the parameters affecting the result need to be optimized in order to obtain the material properties with high accuracy. Although the OBM is referenced in some standards and widely used in scientific studies, detailed information in the literature on how to perform a successful Oberst Beam experiment is very limited. This is the main subject this paper aims to address. In this paper, after setting up the Oberst test rig the effects of various parameters on measured data using an Oberst test rig are examined in an attempt to improve the accuracy of the estimated material properties. Then repeatability measurements are performed and the main parameters affecting the quality of the measured data are identified. After that, extensive tests are performed so as to determine the effect of the amplitude of the excitation force, adverse effects of electromagnetic excitation and the effects of length of the test specimen. Furthermore, it is found that the small differences between individual samples may also affect the results significantly. Finally, some suggestions are given to the potential users of the OBM so as to avoid undesirable effects of certain parameters during such measurements.

Topics: Damping
Commentary by Dr. Valentin Fuster
2010;():135-145. doi:10.1115/ESDA2010-24575.

This study concentrates on the simulation of elastic and thermoelastic wave propagation in two-dimensional thermoelastic regions based on the classical and generalized coupled thermoelasticity. A finite element scheme is employed to obtain the field variables directly in the space and time domains. The FE method is based on the virtual displacement and the Galerkin technique, which is directly applied to the governing equations. The Newmark algorithm is used to solve the FE problem in time domain. Solving 2D coupled thermoelasticity equations leads to obtain the distribution of temperature, displacement and stresses through the domain. The problem is solved for two different type of boundary conditions (BCs), and the behavior of temperature, displacement and stress waves according to these BCs and based on the classical and generalized coupled thermoelasticity theories are shown and compared with each other. Several characteristics of the thermoelastic waves in two-dimensional domains are discussed according to this analysis.

Commentary by Dr. Valentin Fuster
2010;():147-152. doi:10.1115/ESDA2010-24576.

Rotors show very rich dynamical behavior especially when friction is involved. Due to the interaction of nonconservative, dissipative and gyroscopic forces a very interesting stability behavior can be observed. Instability of the rotor can yield severe problems, for example in the context of brakes and clutches it causes squeal, in the process of paper calendering the duration of the rollers is decreased substantially. This paper deals with the problem of how to design a rotor such that it is robust against friction induced vibrations using structural optimization. The problem is addressed using discrete and continuous models for disk brake squeal. It is shown that a proper design of the brake rotor can passively suppress squeal without introduction of additional damping into the system. Many of the qualitative results carry over to other problems of friction induced vibrations in rotors.

Commentary by Dr. Valentin Fuster
2010;():153-161. doi:10.1115/ESDA2010-24587.

This paper analytically investigates the effect of fiber arrangements on stress distribution around a pin joint in a laminated composite. It is assumed that all fibers lie in one direction while loaded by a force po at infinity. According to the shear lag model, equilibrium equations are derived for two types of fiber arrangements. In the first model, a square arrangement is selected for the fibers, while in the second; a hexagonal arrangement is used to deduce the equilibrium equations. Upon proper use of boundary and boundness conditions, stress and displacement fields are derived within the laminate and their peak values are determined on the compressive side of the pin periphery. The effect of pin diameter on stress concentration around the pin is well examined. The presence of the pin on shear stress distribution in the laminate is also examined for various pin diameters. According to the results, a square arrangement of fibers results in smaller values of stress concentrations around the pin, as compared to those of a hexagonal arrangement. The pin position and its diameter shows to have noticeable effect on both normal and shear stresses developed within the laminate, as well as pin surrounding.

Commentary by Dr. Valentin Fuster
2010;():163-170. doi:10.1115/ESDA2010-24594.

In the present article, the buckling analysis of thin functionally graded rectangular plates resting on elastic foundation is presented. According to the classical plate theory, (Kirchhoff plate theory) and using the principle of minimum total potential energy, the equilibrium equations are obtained for a functionally graded rectangular plate. It is assumed that the plate is rested on elastic foundation, Winkler and Pasternak elastic foundations, and is subjected to in-plane loads. Since the plate is made of functionally graded materials (FGMs), there is a coupling between the equations. In order to remove the existing coupling, a new analytical method is introduced where the coupled equations are converted to decoupled equations. Therefore, it is possible to solve the stability equations analytically for special cases of boundary conditions. It is assumed that the plate is simply supported along two opposite edges in x direction and has arbitrary boundary conditions along the other edges (Levy boundary conditions). Finally, the critical buckling loads for a functionally graded plate with different boundary conditions, some aspect ratios and thickness to side ratios, various power of FGM and foundation parameter are presented in tables and figures. It is concluded that increasing the power of FGM decreases the critical buckling load and the load carrying capacity of plate increases where the plate is rested on Pasternak in comparison with the Winkler type.

Commentary by Dr. Valentin Fuster
2010;():171-181. doi:10.1115/ESDA2010-24680.

Depleting oil reserves in shallow water are opening the avenues of new ventures in deep sea conditions. India is no exception; deep sea explorations are highly recommended and exercised. As part of the design process, there are requirements of structural strength based on criteria referring to failure modes, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. 3D Nonlinear dynamic analysis of riser is obtained in the time domain using finite element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability analysis of riser. It is based on a bi-linear relationship to model fatigue crack growth and incorporates a failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modeling, especially on fatigue crack growth parameters, is undertaken with the aid of recently published data in support of the bi-linear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo Simulation. The bi-linear S-N curve and crack growth models are found to lead to higher fatigue life estimation. Sensitivity behavior pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimization of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

Commentary by Dr. Valentin Fuster
2010;():183-192. doi:10.1115/ESDA2010-24685.

In this paper, the buckling analysis of conical shell under transverse pressure or axial compression is studied using the Differential Quadrature Method (DQM) for various boundary conditions. Based on the Donnell theory of shell, the equilibrium equations are obtained using Hamilton’s principle. The adjacent equilibrium criterion is employed to defining the stability equations of conical shell subjected to lateral pressure and axial compression. Then the stability equations are solved numerically using DQM and employing the concept of extra degrees of freedom. The acquired results in special cases are compared with the results in literature for the accuracy evaluation of the method and a good agreement can be seen. The non-dimensional critical buckling loads are tabulated for different vertex angles, some thickness-radius ratios and various combinations of boundary conditions. Also, the effects of the vertex angle, boundary conditions, length-radius ratio and thickness-length ratio on the buckling behavior of the conical shell are investigated in details.

Topics: Buckling , Shells
Commentary by Dr. Valentin Fuster
2010;():193-200. doi:10.1115/ESDA2010-24705.

The buckling delamination problem for the rectangular plate made from composite (orthotropic) material is studied. It is supposed that the plate has a rectangular edge-crack and edge-surfaces of that have an initial infinitesimal imperfection. The development of this initial imperfection with an external compressive loading acting along the crack is studied in the framework of the three-dimensional geometrically nonlinear field equations of the elasticity theory of anisotropic bodies. For the determination of the values of the critical force the initial imperfection criterion is used. The corresponding boundary-value problems are solved by employing the boundary form perturbation techniques and the FEM. The influence of the material or geometrical parameters of the plate on the values of critical force is discussed.

Commentary by Dr. Valentin Fuster
2010;():201-205. doi:10.1115/ESDA2010-24713.

Optimal revenue of oil and gas fields is of interest due to high price and limited amount of these sources of energy. In this way, smart well technology provides a numerous range of benefits and for these great advantageous is widely used in oil/gas industry. This technology involves down-hole measurement and control of well bore and reservoir flow. One of the most important down-hole control subsystems in a smart well is pressure and temperature sensing system which can help the reservoir being modeled accurately. The purpose of this paper is to design and analysis a new sensory package for a desired oil well. A brief review of the advantages of fiber optic sensing technology in smart well control system is performed. Having studied several possibilities of installation systems for sensors, a new arrangement and casing for temperature/pressure sensor is developed here. Effect of pressure and temperature on stress distribution in the casing has been investigated and a suitable casing is obtained.

Commentary by Dr. Valentin Fuster
2010;():207-217. doi:10.1115/ESDA2010-24720.

In this paper the main goal is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic field, and by a finite element software. the connections are simulated to complete and verify simple modeling of analytical and numerical analysis of the behavior of vertical and slant bolted endplate connections due to increase in temperature. The results that are obtained from performance of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature will be compared.

Topics: Temperature
Commentary by Dr. Valentin Fuster
2010;():219-226. doi:10.1115/ESDA2010-24739.

Honeycomb cellular structures, due to their light weight and high energy absorbing, have been used extensively as energy absorbers or cushions to resist external loads. In this paper, the mean crushing stress and the wavelength of the folding mode, as two important parameters in the study of metal square honeycomb crushing under quasi-static loading have been investigated theoretically and experimentally. Firstly, by considering the true cylindrical curvature effects and the flow stress in the folding mode of the honeycomb material, the Wierzbicki’s model in the study of metal hexagonal honeycomb crushing under quasi-static loading is modified. This modification is performed by rewriting the internal energy terms and the external work in the energy method through the basic element folding by considering the true cylindrical curvature effects and the flow stress of the honeycomb material. Comparison of the results obtained by this modified model and Wierzbicki’s model with the experimental data shows better prediction by the model presented in this paper. Subsequently, this modified model has been extended to the study of metal square honeycombs crushing under quasi-static loading and the mean crushing stress and the wavelength of the folding mode of these structures have been predicted. This analytical model predicts the mean crushing stress of the metal square honeycomb as a function of both the geometrical parameters and its material, while the predicted wavelength of the folding mode is just a function of the geometrical parameters. Finally, the experimental tests have been performed to verify the preciseness of this theoretical model.

Topics: Metals
Commentary by Dr. Valentin Fuster
2010;():227-232. doi:10.1115/ESDA2010-24759.

Often a designer has the problem to apply a suitable system of geometrical and dimensional tolerances to an assembly. The right solution is not unique, in fact it depends on the chosen parameters. If the tolerances have to be optimized, some important parameters have to be taken into account, e.g. the efficiency of each prescription, or if this last is reachable, or it can be verified and how much the realization costs. The authors opinion is that a statistical approach based on the Monte Carlo Method is very useful when the tolerances chains are complex. This paper shows an application of this method in order to verify the functional alignment between two assemblies and a critical analysis of the uncertainty in phase both of the component design and test. This study has been developed thanks to the strict requirements imposed by ESA (European Space Agency) on the components that Thales Alenia Space has to realize within the LISA Pathfinder experiment. The very critical aspect of this work is to reciprocally align two cylindrical elements of two different assemblies. The specifications require 100 μm as maximum linear displacement and 300 μrad as maximum angular displacement. Moreover this prescriptions have to be verified also when the two elements are independently moving. To be able to reach such strict accuracy level the components have been assembled in an ISO 100 class cleanroom and the work space was a 3D Coordinate-Measuring Machine (CMM). The cylindrical elements have a 10 mm diameter, so the value of the measurement uncertainty associated with the alignment check is fundamental. Starting from the different uncertainty sources, the measurability and verifiability of the alignment have been considered and evaluated. The overall uncertainty has been assessed by numerical simulations which have taken into account the dimensional, geometrical and form tolerances as well as the instrumental uncertainty of the 3D CMM. This estimation has been positively validated by a session of repeated measurements. Numerical simulations have also allowed performing a sensitivity analysis, in order to give information about which sources more contribute to the overall uncertainty.

Commentary by Dr. Valentin Fuster
2010;():233-241. doi:10.1115/ESDA2010-24782.

The protection of structures under impact loading often necessitates the need for energy absorbers; devices designed to absorb the impact energy in a controlled manner and hence, protect the structure under consideration. Thin-walled tubes are widely used as energy absorbers in various vehicles and moving parts. The objective of the present study is to investigate the energy absorption characteristic of tubes with corrugations in different geometries, in lateral direction. In order to produce corrugations, an innovative solution is introduced. Corrugations can be very easily generated on the surface of cylindrical aluminum tubes by stamping method. Corrugations with different wavelengths and amplitudes can be produced by this method. Experimental tests are conducted to study the effect of changing corrugation geometry (type and amplitude). Quasi-static tests are carried out whose results for lateral compression show that tubes with corrugation have a higher mean crushing force and this force is directly proportional to number of corrugations and their amplitude. Moreover, it is observed that corrugated tubes can absorb approximately four times more energy than tubes without corrugations, in the same size and weight. Finally, considering the experimental tests, corrugated tubes are shown to be more effective in lateral direction as an energy absorber, and they also exhibit desirable force-deflection responses which are important in the design of energy absorbing devices.

Commentary by Dr. Valentin Fuster
2010;():243-251. doi:10.1115/ESDA2010-24807.

The buckling delamination around the band cracks contained with the simply supported all edge-surface rectangular sandwich thick plate is investigated. It is assumed that the sandwich plate is composed of two face layers and a core layer. Face and core layers are made of different materials and it is assumed that there are two same cracks at the interfaces between the layers. Material of each layer is isotropic and homogeneous. For the solution procedure it is supposed that the surfaces of the cracks have insignificant initial imperfections. The development of this initial imperfection with an external compressive loading acting along the cracks is studied in the framework of the three dimensional geometrically nonlinear field equations of the elasticity theory and the piece-wise homogeneous body model. For the determination of the values of the critical force the initial imperfection criterion i.e. the case where the imperfection starts to increase and grows indefinitely, is used. The corresponding boundary value problems are solved by employing the boundary form perturbation techniques and the three dimensional FEM. The numerical results on the critical force are presented and analyzed. The influences of the material and geometrical parameters on these critical values are discussed.

Commentary by Dr. Valentin Fuster
2010;():253-262. doi:10.1115/ESDA2010-24814.

This article presents a perturbation approach for the bifurcation analysis of MDoF vibration systems with gyroscopic and circulatory contributions, as they naturally arise from problems involving moving continua and sliding friction. Based on modal data of the underlying linear system, a multiple scales technique is utilized in order to find equations for the nonlinear amplitudes of the critical mode. The presented method is suited for an algorithmic implementation using commercial software and does not involve costly time-integration. As an engineering example, the bifurcation behaviour of a MDoF disk brake model is investigated. Sub- and supercritical Hopf-bifurcations are found and stationary nonlinear amplitudes are presented depending on operating parameters of the brake as well as of tribological parameters of the contact.

Topics: Bifurcation , Brakes
Commentary by Dr. Valentin Fuster
2010;():263-269. doi:10.1115/ESDA2010-24841.

In the presented article we propose a mathematical model for nonlinear response of the polycristalline ferroelectrics, an efficient numerical algorithm for its parameters identification, and finally we deal with the ways of their using in practice. Piezoelectrics and ferroelectrics constitute an important class of materials known owing theirs wide application as sensors and actuators in a large number of devices and components. The control, description, and understanding of piezoelectrics and ferroelectrics behavior present thus an important and difficult undertaking from both the practical and theoretical point of view. The piezoelectric hysteresis is an important property of piezoelectric and ferroelectric materials caused by different physical processes that take place in ferroelectric materials, e.g. domain-wall pinning, defect ordering, etc. Most often hysteresis is undesired in high-precision sensor, actuator and capacitor applications. But leaving out of framework the origin and mechanisms of the piezoelectric hysteresis the necessity of devices rational design forces to develop the specialized CAE systems to be able to simulate and optimize an efficiency of the ferroelectric-based devices, considering both useful and undesirable phenomena. So, finite-element modeling of sensor and actuator devices requires knowledge of the supplementary constitutive relations that are valid at broad range of electric fields, including the cases of irreversible polarization or depolarization process. There are several approaches to deriving the governing relationships, particularly, orientation Jiles–Atherton model, where governing relationships are formulated by increments between some intrinsic and target parameters. At low mathematical complexity this model is based on the transparent physical meanings, allowing to describe the work of electric field rotating the domains, and energy destructing the fixed domain walls. The proposed model represents a nonlinear ordinary differential equation relative to polarization and driving by electric field. Together with incremental theory this model allows to describe the real behavior of the physical object and to determine all needed field features at list for quasistatic process. As many models describing a nonlinear behavior of whole class of polycristalline materials our model depends on the five intrinsic parameters which have a different physical nature, and have influence on the nonlinear hysteretic response of material. Settings of model imply an unambiguous determination of such parameters. Identification of these parameters is a coefficient inverse problem, and for its resolving we have used the experimentally obtained hysteretic loops. At numerical implementation the set of these five parameters minimize a discrepancy functional square depended on experimentally observed and calculated points of hysteretic loop. Due to complexity of the minimized functional behavior on the space of identified parameters the minimization procedure was realized by means of Genetic Algorithm Toolbox MATLAB. The developed numerical method for hysteresis differential operator parameters identification has shown the good efficiency, robustness, and speedy convergence. These parameters then have used for static and modal analysis by finite element package ACELAN that utilizes an incremental theory for describing of irreversible polarization process. Finally we demonstrate some calculation results for non-uniformly polarized piezoceramic elements.

Commentary by Dr. Valentin Fuster
2010;():271-278. doi:10.1115/ESDA2010-24861.

In this study, free in-plane and out-of-plane bending vibrations of frame structures have been analyzed together with torsional vibration. Axial extension, rotational inertia and shear effects have also been considered. The frame structure has been constructed as having two beams with doubly symmetric cross-sections and connected at any angle to each other. These types of frames frequently appear on ships as bridge wings which are probably the most problematic members experiencing severe vibration. Internal damping has been incorporated into the analyses by using a complex modulus of elasticity. Natural frequencies have been obtained analytically by solving simultaneous linear equations of complex coefficients. A finite element analysis has also been conducted to verify the analytical results. Furthermore, an experimental modal analysis has been carried out and the results have been compared with theoretical ones in tables for various connection angles and damping factors. The agreement among results has been found to be good.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2010;():279-285. doi:10.1115/ESDA2010-24875.

A theoretical approach, in order to define the structural behaviour of riveted joints, is presented. The closed form solutions lead to the definition of a Rivet Element useful to FE models of multi-riveted structures. The objective is an accurate evaluation of the local stiffness of riveted joints in FE analysis, which is fundamental to perform a reliable simulation of multi-joint structures and, consequently, a good estimate of loads acting on connections; this makes it possible to introduce new general criteria allowing, for example, to predict fatigue behaviour. On the other hand, a low number of degrees of freedom is needed when several connections are present in a complex structure. The goal is to reach a reliable model of the rivet region which can be used as the basis to develop a Rivet Element in FE analysis. The proposed Rivet Element combines the precision in the simulation with a very limited number degrees of freedom in the finite element model of a complex structure having several rivets. In the present paper the structural behavior of two simple riveted specimens is investigated experimentally and numerically using a new Rivet Element. A comparison with a joint model performed with very refined non-linear 3D models of rivet and with experimental data is performed and a good agreement is shown.

Commentary by Dr. Valentin Fuster
2010;():287-294. doi:10.1115/ESDA2010-24906.

The vibration of FG plate embedded with PZT5 rectangular patches on the top and/or the bottom surface(s) as actuators/sensors is investigated. Based on the classical laminated plate theory, the governing differential equations of motion are derived under a variable electric charge. The equation of motion for PZT5 patch is obtained and solved. The effect of feedback gain and FGM volume fraction exponent on the plate frequency and its deflection are studied. It is noticed that increasing the feedback gain leads to the reduction of frequency and displacement. Moreover, by increasing the value of the FGM volume fraction exponent the resonant frequency decreases.

Commentary by Dr. Valentin Fuster
2010;():295-298. doi:10.1115/ESDA2010-24972.

Fatigue strength is one of the most important mechanical properties. Durability and reliability of car parts are often defined by their fatigue strength, since most of them are loaded with dynamic, repeating or variable loads and the main type of failure is metal fatigue. Various surface hardening methods have a huge impact on fatigue strength of structural materials. The choice of surface processing method is determined by properties and microstructure of a material, as well as the purpose and working conditions of part’s material. Very often the optimum processing is a combination of several methods, which enables to obtain the required properties (high fatigue strength, wear, etc.). The impact of several combined surfaces processing on the fatigue strength of carbon steel samples is investigated in the work. The surface was hardened using different processing combinations: by hardening with high frequency electricity currents, rolling by rollers, heating and cooling under different temperatures. Experimentally it is proved that thermal treatment of plastically deformed carbon steel significantly increases fatigue strength. Experiments showed that after surface hardening with the given regimes, the microstructure and residual stresses are formed in such way that fatigue crack begins to grow under the hardened sample surface.

Commentary by Dr. Valentin Fuster
2010;():299-306. doi:10.1115/ESDA2010-25003.

Rapid development of transportation industries worldwide, including railways and the never ending demand to shorten travel time during trade, leisure, etc. have caused planning and implementation of high-speed railways in many countries. Variety of such systems including magnetic levitation (maglev) has been introduced to the industry. Contrary to traditional railway vehicles, there is no direct contact between maglev vehicle and its guideway. These vehicles travel along magnetic fields that are established between the vehicle and its guideway. Therefore, these vehicles can travel at very high speeds. The replacement of mechanical components by electronics components overcomes restrictions of conventional railway. Manned maglev vehicles have recorded speed of travel equal to 581km/hr . This has practically paved the way to manufacture super high-speed trains. Currently, there are ElectroMagnetic Suspension (EMS) and ElectroDynamic Suspension (EDS) systems available to the industry. There are also varieties of vehicles that are manufactured based on these two types of systems. Mechanical engineering plays vital roles in design and analysis of suspension systems and corresponding vehicles. In this research, different types of maglev suspension systems and vehicles are studies. It is the purpose of this research to design a model for magnetic suspension system and a model for maglev vehicle. Static and dynamic live loads due to the maglev vehicle are investigated and mathematical model of maglev loading is presented. The proposed model for maglev vehicle is thoroughly analyzed for its static and dynamic loading. This study is focused on the dynamics of maglev vehicle. Modeling vehicle/guideway interactions and then explain the response characteristics of the maglev system for a five-car vehicle traveling on a single-span guideway, with emphasis on vehicle/guideway coupling effects are accomplished. Design of maglev vehicle with finite element method is also considered. Results justify practicality of the proposed suspension system and vehicle for Tehran-Mashhad maglev project.

Commentary by Dr. Valentin Fuster
2010;():307-315. doi:10.1115/ESDA2010-25021.

This paper investigates the dynamic stability of a finite Timoshenko beam spinning along its longitudinal axis and subjected to a moving mass-spring-damper (MSD) unit traveling in the axial direction. The mass of the moving MSD unit makes contact with the beam all the time during traveling. Due to the moving MSD unit, the beam is acted upon by a periodic, parametric excitation. In this work, the equations of motion of the beam are first discretized by the Galerkin method. The discretized equations of motion are then partially uncoupled by the modal analysis procedure suitable for gyroscopic systems. Finally the method of multiple scales is used to obtain the stability boundaries of the beam. Numerical results show that if the displacement of the MSD unit is equal to only one of the two transverse displacements of the beam, very large unstable regions may appear at main resonances.

Commentary by Dr. Valentin Fuster
2010;():317-322. doi:10.1115/ESDA2010-25030.

Shot peening (SP) is a mechanical surface treatment commonly performed to improve the fatigue behavior through creation of compressive residual stresses close to surface and work hardening of the surface material. Notwithstanding wide application of shot peening in the industrial environment, the determination of optimal peening condition for Ti alloys is still more an art than a science, taking into account that there is not a well established method to choose the process parameters in order to enhance the fatigue behavior. In this paper a comprehensive numerical and experimental study is presented aimed at finding the optimized peening conditions based on characterization of surface layer of material after multiple impacts. The numerical simulations provide a quantitative description of shot peening effects in terms of residual stress field and thickness of work-hardened surface layer. Comparison with numerical results, obtained by means of X-ray diffraction (XRD), shows a very good correspondence. Finally the results of experimental bending fatigue tests, performed on shot peened specimens by means of Rumul Cracktronics machine, confirm that shot peening significantly increases the fatigue strength of the considered Titanium alloy.

Commentary by Dr. Valentin Fuster
2010;():323-328. doi:10.1115/ESDA2010-25087.

The automatic vibration monitoring methods of gears and gearboxes due to their extensive applications in industry are improving. Hence, their vibration signal and its derived features, has been an interesting topic for researchers in this field. On the other hand, optimizing the number of vibration signal features used in the detection and diagnosis process is crucial for increasing the fault detection speed of automatic condition monitoring systems. In this paper, a system based on multiple layer perceptron artificial neural networks (MLP ANNs) is designed to diagnose different types of fault in a gearbox. Using a feature selection method, the system is optimized through eliminating unimportant features of vibration signals. This method is based on a simple and fast sensitivity evaluation process, which results in a considerable estimation, despite its simplicity. Consequently, the system’s speed increases, while the classification error decreases or remains constant in some other cases. An experimental test rig data set is used to verify the effectiveness and accuracy of the mentioned method. Four different types of data which are generated through the test rig setup are: no fault condition, 5% fault (5% eroded tooth) gear, 20% eroded tooth gear and the broken tooth gear. The results verify that eliminating some input features of gear vibration signal, using this method, will increase the accuracy and detection speed of gear fault diagnosis methods. The improved systems with fewer input features and higher precision, facilitates the development of online automatic condition monitoring systems.

Commentary by Dr. Valentin Fuster
2010;():329-334. doi:10.1115/ESDA2010-25089.

An active diagnostics method intended for identification of technical condition of pipelines and other components of nuclear facilities is considered. This method is based on detection of structural anomalies in components by observing changes in static and dynamic behavior of component structure which are registered during special tests. Static behavior is analyzed as response to time-independent mechanical or temperature loading. Dynamic behavior can be analyzed through studying fields of vibration displacements, velocities and accelerations when sinusoidal mechanical oscillations are generated. Structural anomalies can be presented as deviations of stiffness, geometry and inertial parameters from their nominal (design) values. Impact of these deviations on structural response may be bigger in spatial scale than anomaly dimensions. Therefore there is a theoretical possibility to detect structural anomaly in the areas which are inaccessible for direct observing by registration of structure response parameters in observable areas. The paper describes the theoretically basis and results of the experimental and numerical studies on detection of a hidden crack-like anomaly in pipe components. Experimental study of dynamic and static response is carried out by coherent optical methods, and numerical analysis — by finite element method. Theoretical and experimental data have a good agreement and allow to reveal anomaly position and to estimate roughly its dimensions. Application of the method to welded joint in pipe specimen which corresponds to real nuclear facility pipeline is under investigation now.

Commentary by Dr. Valentin Fuster
2010;():335-344. doi:10.1115/ESDA2010-25113.

In this paper, the effect of three main parameters: a) welding speed, b) cooling rate of fluid flow through the main pipe; and c) number of welding passes, have been studied to obtain an effective method to reduce the burn-through risk during the in-service welding of AISI-316 pipe branch connection to perform hot-tapping. In addition, important patents regarding the new methods of hot-tapping have been reviewed. To carry out numerical simulation, a 3D Finite Element (FE) based thermo-mechanical model has been developed. Using this model, thermo-mechanical stresses and temperature distribution along the main-pipe wall-thickness have been obtained with maximum and minimum allowable welding speeds; and with two high and low level of steam flow rate through the main pipe. The Von-Mises yield criterion using the temperature dependent yield stress has been used to check the main pipe failure during the welding process. The results show that current techniques, including API recommendations, which only rely on the observation of the main-pipe inner wall temperature, does not take into account the effect of mechanical or thermal stresses due to the inline pressure or other working parameters which have significant role in burn-through. In addition, the results show that the increase of welding speed reduces the risk of burn-through but it increases the risk of hot cracking. On the other hand, decreasing the steam flow rate has the opposite effect. It has also been shown that using smaller electrode size is the most effective way to decrease burn-through risk.

Topics: Welding , Bifurcation
Commentary by Dr. Valentin Fuster
2010;():345-350. doi:10.1115/ESDA2010-25193.

In this paper a new approach is applied to investigate the effects of piezoelectric materials on the damping properties of laminated composite beams. The active control is obtained by using an actuator and a sensor piezoelectric layer acting in a closed loop. The formulation is based on the first order shear deformation theory (FSDT). There are purely mechanical models in the literature, but only at a finite element level. Generally the electric quantities are condensed from an electromechanical finite element model. Here, an analytical study is performed to get equivalent beam equations that are of elastic type. The model is applicable. Analytical solutions are developed for simply supported composite beams with piezoelectric layers. A constant velocity feedback control algorithm is used to actively control the dynamic response of the structure through a closed loop control. Numerical results of vibration suppression effect for various locations and thickness of the piezoelectric layers, lay-up sequence, and control parameters are presented.

Commentary by Dr. Valentin Fuster
2010;():351-358. doi:10.1115/ESDA2010-25213.

This paper presents a method for the calculation of the stresses around three non-intersecting identical circular holes in a row, in a thin and infinite isotropic plate subjected to in-plane longitudinal, transverse or biaxial tension at infinity. The calculation of the stresses around any of the three holes is obtained in terms of the stresses that would exist around and at the center of the contour of a third would-be hole in the plate, initially, containing two holes. The results from the present method are compared to finite element as well as to published results in the literature. It is seen that the method yields satisfactory results at key points around the contour of the holes.

Commentary by Dr. Valentin Fuster
2010;():359-364. doi:10.1115/ESDA2010-25218.

Topics: Stress , Design
Commentary by Dr. Valentin Fuster
2010;():365-373. doi:10.1115/ESDA2010-25246.

The human hand works in a perfect accord with the brain for an efficient exploration of physical world and objects perception according to man’s purposes. During the haptic sensing, the fingertip slides on a surface activating the receptors located under the skin allowing the brain to identify objects and information about their properties. In fact, in order to create the contact, the hand must exercise a force causing the fingertip to deform, generating a stress-state that contains the information on the object in contact. The information concerning the object surface is represented by the vibrations induced by the friction between the skin and the rubbed object in contact. The mechanoreceptors have the key role of transducing the stress state into an electrical impulse conveyed to the brain. Nevertheless, the vibration spectra induced by the finger/surface rubbing and the consequent activation of the mechanoreceptors on the skin were rarely investigated. A clear understanding of the mechanisms of the tactile sense is basilar for manifold applications, like the development of artificial tactile sensors for intelligent prostheses or robotic assistants, and for the ergonomics. In this context, it is fundamental to realize appropriate dynamic analysis of the signals that characterize the characteristics of the contact. In other words, it is necessary to investigate the vibration spectrum measured on the finger, in order to identify the frequency range of measured spectra (that should correspond to the expected one given by the mechanoreceptors activation frequency range [2–500 Hertz]). An experimental set-up is developed to recover the contact global dynamics by detecting the contact force and the induced vibrations; the bench test has been designed to guarantee the measurements reproducibility and, at cause of the low amplitude of the vibrations of interest, to perform measurements without introducing external noise. In particular, in this paper, the interest will be focused on the changes shown in vibration spectra with respect to variations of the scanning velocity and surface roughness characteristics.

Commentary by Dr. Valentin Fuster
2010;():375-384. doi:10.1115/ESDA2010-25247.

The aim of this work is to present the results from a non linear finite element analysis in large transformations of the contact interface between two deformable bodies when sliding initiates and the roughness is introduced at the contact surfaces. The two-dimensional in-plane dynamic model consists of two different isotropic elastic media separated by an interface governed by Coulomb friction law, and subject to remotely applied normal and shear tractions (pre-stress phase). Once the ratio between the local values of tangential and normal stresses reaches the limit value, the sliding initiates and local ruptures are activated (nucleation phase). The propagation of the ruptures over the interface and the wave propagation inside the solids are analyzed. The interactions between the waves propagating into the two solids (P waves, shear waves, surface waves) give raise to different types of ruptures. They can be classified depending on their velocity front (sub-Rayleigh, sub-shear, super-shear) or on their interface states (pulse-like, crack-like). A sinusoidal roughness is introduced at the contact surfaces and the analysis is performed for different values of the roughness parameters. Depending on the relative dimension between the roughness wavelength and the width of the wave fronts, two different behaviour can be observed: i) a coupling between the wave propagating into the two bodies; ii) a decoupling of the wave propagation inside the two materials, characterized by an independent wave propagation. First the wave propagation is analyzed when a single rupture is originated in pre-sliding conditions; successively, the wave generation during sliding initiation is addressed.

Commentary by Dr. Valentin Fuster
2010;():385-391. doi:10.1115/ESDA2010-25248.

In this study, axial compression behavior of grooved thin-walled steel cylinders is investigated using experimental and numerical methods. Circumferential grooves are generated by means of a special forming tools and the effect of interval between the grooves and their total number on the load-displacement curve, energy absorption-displacement curves and initial buckling load are investigated. It is revealed that having circumferential grooves on the tubes can decrease the initial peak load in load-displacement curve and also increase the amount of absorbed energy. Then explicit Finite Element Model of aforementioned grooved tubes under axial loading are generated using ANSYS software and solved utilizing LSDYNA solver. Result of the FE models (containing the amount of absorbed energy, the peak load and the load-displacement curve during axial compression) are validated by comparing them with those of experimental test. The outcome of comparisons confirms the FE model to be in a good agreement with experimental results.

Commentary by Dr. Valentin Fuster
2010;():393-402. doi:10.1115/ESDA2010-25249.

The main goal of this research is to analyze the effect of drilling mud and WOB on instability threshold of drill string. To this end, the kinetic and potential energy of an element of drill string for axial and lateral vibration is written in an integral form. The effect of geometrical shortening is considered in potential energy. The effect of drilling mud is modeled by the Paidoussis model. The works done by external forces are calculated. The finite element method is employed to discretize the system. The effects of stabilizers are modeled by dropping the nodes coincided with them. Flutter instability analysis is employed to analyze drill string’s instability threshold. By this procedure, the instability threshold of drill string is obtained for different WOB and drilling mud flow. Also, the effects of stabilizers numbers and arrangements are also illustrated. These results may be used for choosing the safe domain of drilling process.

Commentary by Dr. Valentin Fuster
2010;():403-410. doi:10.1115/ESDA2010-25430.

Spatial steady-state harmonic vibrations of a layered anisotropic plate excited by the distributed sources are considered. The work is based on the classical methods of the integral Fourier transforms and integral representations of the Green’s functions. In Fourier transform domain, the displacement vector is represented in terms of the Green’s matrix transform and the transform of the surface load vector. The two-dimensional inverse Fourier transform of the displacement vector is computed by reducing double integral to the iterated one with integrating along a contour, which deviates from the real axis while bypassing the real poles, and with subsequent integrating along the wave propagation angle. Three numerical algorithms of computing related iterated integrals are presented. The features of the application of these algorithms for the near- and far-field zones of the source are discussed. All of presented methods are compared for the numerical examples of vibrations on the surface of 24-layer symmetrical composite.

Commentary by Dr. Valentin Fuster
2010;():411-419. doi:10.1115/ESDA2010-25450.

Highly idealised models of friction-induced vibration have been motivated by an attempt to capture what is essential to the phenomenon. This approach has resulted in a few simple mechanisms that are thought to capture common routes to instability. This paper aims to determine how well these perform as approximations to a more complex system, and whether the essential ingredients needed for a minimal model can be identified. We take a reduced-order model that exemplifies ‘mode-coupling’ and explore the extent to which it can approximate predictions based on an experimentally identified test-system. For the particular test system under study, two-mode ‘mode-coupling’ is rarely a good approximation and three modes are usually required to model a limited frequency range. We then compare predictions with results from an extensive program of sliding contact tests on a pin-on-disc rig in order to identify which ingredients are needed to explain observed squeal events. The results suggest that several minimal models would be needed to describe all observed squeal initiations, but the ‘negative-damping’ route to instability, which requires a velocity-dependent friction law, convincingly accounts for one cluster.

Topics: Friction , Vibration
Commentary by Dr. Valentin Fuster

### Heat Transfer

2010;():421-425. doi:10.1115/ESDA2010-24018.

This work experimentally studies the thermal performance of plate-fin vapor chamber heat sinks using infrared thermography. The effects of the fin width, the fin height and the Reynolds number on the thermal performance are considered. The results show that generated heat is transferred more uniformly to the base plate by a vapor chamber heat sink than by a similar aluminum heat sink. Therefore, the maximum temperature is effectively reduced. The overall thermal resistance of the vapor chamber heat sink declines as the Reynolds number increases, but the strength of the effect falls. The effect of the fin dimensions on the thermal performance is stronger at a lower Reynolds number.

Topics: Vapors , Heat sinks
Commentary by Dr. Valentin Fuster
2010;():427-431. doi:10.1115/ESDA2010-24070.

Steady state and two-dimensional natural convection heat transfer flow around a horizontal and isothermal cylinder with a longitudinal fin attached to it that is located between two tilt and very low conductive plates is studied experimentally by using a Mach-Zehnder interferometer. Effects of the plates slope angel (θ) on heat transfer from the tube is investigated for Rayleigh number ranging from 1000 to 15500. Experiments are done for a fin attached cylinder placed between two low conductive plates. Two different diameter tubes with diameters of D=10 and 20mm are utilized for broad Rayleigh number range. Results specify that, heat transfer experience differs for special Rayleigh numbers. For Rayleigh numbers ranging less than 5500, rate of heat transfer amount from the cylinder surface is less than that of a lone cylinder and it’s the result of no slip boundary condition on the fin surface. For this range of Rayleigh number by the use of plates, heat transfer from the cylinder surface decreases slightly and plates leaning does not alter heat transfer speed from the cylinder surface. For Rayleigh number ranging from 5500 to 15500, heat transfer rate from the cylinder surface is lower than the heat transfer rate from the surface of an individual cylinder. Though, by adding placing the low conductive plates as plates to experimental model, heat transfer system differs and chimney effect between fin and the plates increases the heat transfer from the cylinder surface. By increasing the plates slope angel from 0° to 20°, the chimney effect between plates and fin weakens and heat transfer rate from the tube surface is going to the amount of heat transfer rate from a fin attached cylinder which is not placed between plates.

Commentary by Dr. Valentin Fuster
2010;():433-442. doi:10.1115/ESDA2010-24077.

A numerical study is performed to investigate the performance of an innovative thermal system to improve the heat transfer in horizontal annulus. With attached four porous blocks on the inner cylinder, steady laminar mixed convection is presented for the fully developed region of horizontal concentric annuli. Results are presented for a range of the values of the Grashoff number, the Darcy number and the conductivity ratio between the porous medium and the fluid. Results are presented in the form of contours plots of the streamlines and for the temperature isotherms, and in terms of the overall heat transfer coefficients and friction factor. The average Nusselt number increases significantly with an increase of the conductivity ratio and the Grashoff number. With the use of the four porous blocks, the friction factor is consequently increased compared with the situation without porous blocks. The decrease of the Darcy number leads to an increase of the friction factor. If the fully fluid case is taken as a reference, the use of porous blocks is justified only when the ratio of the average Nusselt number to the friction factor is enhanced. The enhancement occurs for the Darcy number higher than 10−3 and for the higher conductivity ratio.

Commentary by Dr. Valentin Fuster
2010;():443-451. doi:10.1115/ESDA2010-24115.

In this work, the effects of jet geometry and the arrangement of film holes on the target plate on the impinging heat transfer are experimentally investigated in detail. A liquid crystal thermograph technology is employed in this study. The aspect ratios (AR) of elliptical jet with five different values, 4, 2, 1, 0.5, and 0.25, jet Reynolds number ranging from 2000 to 4000, and jet-to-target spacing ranging from 1.5 to 4.5 are considered to investigate impingement heat transfer performance. In addition, three arrangements of film hole on the target plates, named side-, middle- and staggered-types, are tested, respectively. The experimental results show that the Nu increases with the increase of jet Reynolds number. Better heat transfer is noted for the cases with smaller jet-to-plate spacing. For the effect of the arrangement of pores on the target surface, the heat transfer on middle-type plate is more significant than the other two for smaller jet-to-plate spacing. As for the effect of aspect ratio, results indicate that the optimal heat transfer performance is found with circular jet of AR = 1.

Commentary by Dr. Valentin Fuster
2010;():453-462. doi:10.1115/ESDA2010-24124.

Open refrigerated display cabinets (ORDCs) suffer alterations of their thermal behaviour and of its performance due to variations of ambient air conditions (air temperature, relative humidity and velocity magnitude and orientation). Some factors interfere and affect the re-circulated air curtain behaviour and thus the equipment’s overall thermal performance. Examples of these factors are the location of air conditioning system discharge grilles, air mass flows originated by pressure differences due to openings to surroundings, and ambient air flow instabilities due to consumers’ passage nearby the frontal opening of the display cabinet, among others. This work performs a three-dimensional (3D) Computational Fluid Dynamics (CFD) modelling of air flow and heat transfer in an ORDC. The influence of ambient air velocity orientation in performance of the re-circulated air curtain is evaluated. A CFD parametric study is developed considering the ambient air orientation parallel, oblique and perpendicular to the frontal opening plane of the equipment. The 3D effects of ambient air velocity orientation are determined through the analysis of air temperature and velocity inside the equipment as well as along and across the air curtain. The longitudinal air flow oscillations and length extremity effects are analyzed, having a considerable influence in the overall thermal performance of the equipment. Experimental tests following EN-ISO Standard 23953 were conducted for climatic class n.er 3 (Tamb = 25 °C, φamb = 60%) in order to characterize the phenomena near inlets, outlets and physical borders. Moreover, experimental data is used to prescribe boundary conditions as well as to validate numerical predictions of temperature and velocity distributions.

Commentary by Dr. Valentin Fuster
2010;():463-468. doi:10.1115/ESDA2010-24144.

Steady state two-dimensional free convection heat transfer in a partitioned cavity with adiabatic horizontal and isothermally vertical walls and an adiabatic partition has been investigated experimentally. The experiments have been carried out using a Mach-Zehnder interferometer. The effects of the angel of the adiabatic partition and Rayleigh number on the heat transfer from the heated wall are investigated. Experiments are performed for the values of Rayleigh number based on the cavity side length in the range between 1.5×105 to 4.5×105 and various angle of the partition with respect to horizon from 0° to 90°. The results indicate that at each angle of the adiabatic partition, by increasing the Rayleigh number, the average Nusselt number and heat transfer increase and at each Rayleigh number, the maximum and the minimum heat transfer occur at θ=45° and θ=90°, respectively. A correlation based on the experimental data for the average Nusselt number of the heated wall as a function of Rayleigh number and the angel of the adiabatic partition is presented in the aforementioned ranges.

Commentary by Dr. Valentin Fuster
2010;():469-476. doi:10.1115/ESDA2010-24154.

A numerical analysis is performed to study the characteristics of heat transfer from a block heat source module at different angles in two-dimensional cabinets. Great efforts are carried out to conduct the effects of thermal interaction between the air steams inside and outside the cabinet on the conjugate conduction–natural convection phenomena. Moreover, the enhancement of cooling performance of the heat source module through the construction of air vents on cabinet wall is rigorously examined. The computation domain covers the cabinet and the surrounding area, and the temperature and velocity fields of the cabinet and surrounding area are solved simultaneously. Results show that the thermal interaction between the airs inside and outside the cabinet, the module angle and vent position can significantly affect the transfer characteristics. Comparing the results for cases with and without the consideration of thermal interaction between the air streams, the difference in hot spot temperature of module can be up to 26% for Pr = 0.7, Kbf = Kpf = Kwf = 100, 105 ≦ Ra ≦ 107 and φ = 0°, 90°, 270°. The maximum reduction in hot spot temperature is about 41% when two air vents are constructed on cabinet wall. The variation of module angle results in the maximum difference of the hot spot temperature is 15% for closed cabinet, and 10% for ventilated cabinet.

Topics: Heat
Commentary by Dr. Valentin Fuster
2010;():477-486. doi:10.1115/ESDA2010-24196.

The generated heats of high-power LED illumination will increase the LEDs’ working temperatures which may degrading the illumination efficiency and lifetimes of LED devices. In this study, the liquid cooling of directly immersed LEDs in different ambient of air or liquids is investigated by the experimental measurement methodology. For LEDs which are operated in series, the generated heats are dissipated into and stored in ambient fluids, then, the casing of lamp (usually acted as a heat sink structure) further conduct these heats and dissipate it into atmospheric air finally. In the experiments, different powers are sequentially input into the LEDs and different fluids, including air, silicone oil, and FC-40, respectively, are filled to cool the LEDs which are directly immersed in these fluids. Temperatures are measured by thermocouples and the IR thermal imager, respectively. Fluid-to-air thermal resistances and fluid temperatures are estimated by a proposed resistance equation. The calculated temperatures are within 10% of error as compared to experimental results. This resistance model is a very good way to quickly examine the fluid-to-air resistances if we want to design the liquid-cooled package of LED illumination.

Commentary by Dr. Valentin Fuster
2010;():487-496. doi:10.1115/ESDA2010-24197.

A freezing chuck with thermoelectric coolers and coolant channels is investigated. Measurement for freezing/thawing processes and analysis of heat transfer enhancements are conducted. Three channel configurations are designed and investigated by numerical simulations and experimental measurements, respectively, to compare the temperature distributions and heat transfer enhancements. Regarding to experiments, inlet temperatures and flow rates of coolants are altered, and transient and steady surface temperatures on the top-plate are measured for these three channel designs. In numerical analysis, convective fluid flows and heat transfers are solved to find temperature, velocity, and pressure fields inside the channel and surface temperatures of top-plate of the freezing chuck by a software package. Comparisons between experimental measurements and numerical simulations are made. Effects of flow rates, inlet coolant temperatures, and channel designs, upon the steady and transient state of temperature distributions and heat transfer enhancements are discussed and conclusions are addressed.

Topics: Freezing
Commentary by Dr. Valentin Fuster
2010;():497-503. doi:10.1115/ESDA2010-24218.

In this paper, the steady/unsteady heat conduction in the longitudinal fins with variable cross sectional area under the periodic thermal conditions is examined. Three different one-dimensional fins are considered and solved numerically by implicit finite difference method. In the hyperbolic equation the heat wave propagates with the finite speed hence the sharp discontinuities appear at the temperature distributions. In the explicit solution oscillations appear at discontinuity point which is greatly improved at the implicit method. In the present study temperature distributions are obtained for non-Fourier fins with different profiles. The effects of frequency of temperature oscillation, relaxation time and fin cross sectional area are studied on the temperature and location of the discontinuity of temperature. In order to validate the obtained results of the present study, these results have been compared to those of numerical solutions of the non-Fourier fin with constant cross sectional area. This comparison confirms the correctness of the current results.

Commentary by Dr. Valentin Fuster
2010;():505-510. doi:10.1115/ESDA2010-24240.

In the present work heat transfer characteristics and flow structure in turbulent flow through a rectangular channel containing built-in triangular winglet-type vortex generators have been analyzed by means of solutions of the Navier-Stokes and energy equations using finite volume method. The geometrical configuration is representative of single element of plain-plate heat exchangers. Each winglet-pair induces longitudinal vortices behind it. Shear stress transport (SST) model is used in this study. The underlying physical phenomena have been described and the effects of Reynolds number and angle of attack, on the heat transfer, pressure drop and thermal performance have been presented.

Commentary by Dr. Valentin Fuster
2010;():511-517. doi:10.1115/ESDA2010-24269.

In this study, a computer program is developed to calculate characteristics of a Chevron type gasketed plate heat exchanger (CTGPHEX) such as: the number of plates, the effective surface area and total pressure drops. The main reason to prefer the use of CTGPHEXs to other various types of heat exchangers is that the heat transfer efficiency is much higher in comparison. Working conditions such as the flow rates and inlet and outlet temperature of both flow sides and plate design parameters are used as an input in the program. The Logarithmic Mean Temperature Method and the different correlations for convective heat transfer coefficient and Fanning factor that are found in the literature are applied to calculate the minimum necessary effective heat transfer area, the number of plate and pressure drops due to friction for both fluid sides of fulfill the desired heat transfer rate. This Turkish / English language optioned user friendly computer program is targeted to be used in domestic companies to design and select CTGPHEXs for any desired working conditions.

Commentary by Dr. Valentin Fuster
2010;():519-524. doi:10.1115/ESDA2010-24353.

An experimental study has been carried out to investigate heat transfer characteristics on internal surfaces of a V-shaped plate exposed to a slot jet impingement of air. A square-edged nozzle is mounted parallel with V-shaped plate axis and jet flow impinges on the bottom of the V-shaped plate. The study is focused on Rayleigh number 159000, angle of V-shaped plate ranging from 22.5 to 45 degree, low Reynolds numbers ranging from 29.05 to 60.41, and slot-to-(V-shaped plate) spacing from 17 to 21 of the slot width. A Mach-Zehnder interferometer is used for measurement of local Nusselt number on the V-shaped plate. It is observed that the local Nusselt number and average Nusselt number decrease with increasing the jet spacing and increase with increasing the Reynolds number. Also the local Nusselt number and average nusselt number increase with rising the angle of V-shaped plate.

Commentary by Dr. Valentin Fuster
2010;():525-533. doi:10.1115/ESDA2010-24362.

In this study obtaining a uniform heat flux over a target surface was investigated by means of using characteristics of jet impingement heat transfer. Conjugate Gradients Method (CGM) was utilized to minimize the objective function defined on the basis of the squared differences between the target heat flux and the calculated ones. Design variables were taken to be jets’ Reynolds numbers, separation distance between the exit plane of the jets and the target plate, as well as inter-jet spacing. Air single phase jets were used in this study. The problem was solved for the cases of 4 and 6 jets. Temperature difference between the jet exit and the target plate is 100°C, and a steady state condition was assumed. The Finite Volume Method and an unstructured mesh were used for direct solution of the jet impingement heat transfer problem for a laminar jets impingement to a flat plate with constant temperature.

Commentary by Dr. Valentin Fuster
2010;():535-540. doi:10.1115/ESDA2010-24402.

The present paper analyses the second law of thermodynamics in a fully developed forced convection in the horizontal helical coiled tube under constant wall temperature. The influence of non-dimensional parameters such as Reynolds number (Re), coil-to-tube ratio (δ) and coil pitch (λ) are inspected on the entropy generation. According to the literature, the coil pitch has a minor effect on the entropy generation compared with Re and δ. Using a CFD tool is a common classical method to find the optimal Reynolds Number and coil-to-tube ratio (δ) based on the entropy generation minimization principal. This approach requires lots of time and resources while the innovative implementation of an Artificial Neural Network (ANN) reduces the simulation time considerably. The data pool generated by the CFD tool is used to train the ANN. As less data is needed to train the ANN in comparison to classical CFD based method, the performance of ANN-CFD optimization approach enhances. As entropy generation minimization principal is applied during the optimization, Nusselt number and friction factor are required to evaluate the entropy generation; these parameters are obtained through a numerical simulation and then are used to train the ANN. The ANN can predict these parameters as a function of different Re numbers and coil-to-tube ratios during optimization. Several different architectures of ANNs were evaluated and parametric studies were performed to optimize network design for the best prediction of the variables. The results obtained from the ANN are compared with the available experimental data to show the network reasonable accuracy.

Commentary by Dr. Valentin Fuster
2010;():541-549. doi:10.1115/ESDA2010-24416.

The problem of natural convection radiation with the presence of participating fluid in a tilted square cavity has been investigated numerically. Two vertical walls are at uniform different temperatures while the others are adiabatic. The working fluid is taken as grey, absorbing, emitting and non-scattering. The finite volume method is used to solve the dimensionless governing equations and SIMPLE algorithm is applied for pressure velocity coupling. The radiative heat flux gradient is estimated by finding radiative intensities from the radiative transfer equation (RTE). A very recent method, called the QL method, is utilized to solve RTE. In this study the effects of the inclination angle, Rayleigh number and optical thickness on the heat transfer and flow characteristics are studied. A great accuracy in the results was observed in the prediction of flow contours and average radiative and convective Nusselt numbers at walls.

Commentary by Dr. Valentin Fuster
2010;():551-560. doi:10.1115/ESDA2010-24441.

The daytime running light (DRL) is a special lamp; they can be automatically switched on when the engine is started, and hence substantially increase the visibility of motor vehicles. Comparing to traditional light sources in DRL, LED offers many advantages such as its high lighting efficacy, low power consumption, quick response time, and long lifetime, However, the application of high brightness LED on DRL still faces severe thermal challenge in removing the unavoidable dissipation heat, which directly influences the radiation efficiency, emitted light quality, and lifetime of LED. Therefore, this investigation focuses on the thermal management for LED Daytime Running Lamp through an integrated effort of CFD simulation, CNC mockup fabrication, and experimental verification. At first, a comprehensive CFD simulation is executed to check the heat-removing performance of several thermal modules for identifying the efficient thermal design. Thereafter, this LED module integrated with a Zinc-Al alloy casing is fabricated via the die-casting and carried out the thermal performance measurements for experimentally validating the numerical outcomes. As a result, after taking the contact resistance and radiation into account, the comparison between numerical and experimental results indicates an acceptable deviation percentage within 5%. Also, experimental result shows that the LED junction temperature is located within the range of 50∼51°C for the case of a 2.34-Watt power input and a 35°C environmental temperature. Moreover, for a 10-Watt power input, the numerical calculation predicts that LED junction temperature is 88.6°C, which is still well below the safety limit (120°C). In conclusion, the accomplishment of this research offers a rigorous and systematic design scheme for the thermal management of the LED DRL. This design scheme has successfully produced an efficient thermal module to control the LED chip temperature below safety limit.

Commentary by Dr. Valentin Fuster
2010;():561-566. doi:10.1115/ESDA2010-24466.

The objective of this work is to analyze and to model the turbulent flames in the context of coherent flame model. We present a detailed description of equations and the flamelet regimes in turbulent premixed flame. A surface density models proposed here represents a good issue for numerical simulation. Extension of coherent flame model and homogenous stilled reactor model is proposed to consider the dynamics behavior of flame and pollutants formation. From the results of this work it is concluded that the coherent flame model allows surpassing difficulties of the turbulent reactive flow modeling. Calculations based on a semi-global kinetic scheme and flamelet formulation combined with a well stirred reactor analysis of the burnt gases are used and provided reasonably accurate values of CO and NO formation. Also, we have observed that CO is formed near the reaction zone (front flame) but emission of CO2 , H2 O and NO are formed in the hot gases.

Commentary by Dr. Valentin Fuster
2010;():567-572. doi:10.1115/ESDA2010-24467.

In this paper the Sequential Function Specification Method is used to estimate the transient heat flux imposed on the rake face of the cutting tool during the cutting operation. The cutting tool is modeled as a three dimensional object. The capabilities of the geometric modeling, mesh generation as well as solver of the commercial software ANSYS is utilized in order to reduce the time expended for modeling and direct heat conduction solution. This way the inverse heat conduction algorithm employs ANSYS as a subprogram through the ANSYS Parametric Design Language (APDL). The stability as well as accuracy of the heat flux estimation is investigated using familiar triangular as well as step heat flux test cases. The effect of noise level, the number of temperature sensors as well as their locations are investigated in order to arrive at an optimal experimental procedure. Finally, a typical temperature data during the working condition are used to recover the heat flux at the cutting tool surface.

Topics: Heat , Cutting tools
Commentary by Dr. Valentin Fuster
2010;():573-582. doi:10.1115/ESDA2010-24476.

A cross-corrugated portable forced-convection solar air heater has been designed, fabricated, and developed. A wavelike bottom plate has been positioned crosswise to the air flow while rectangular baffles have been attached to the flat-plate absorber. The relative corrugation height, (e/Dh ) ranges between 0.24 and 0.4, and relative baffles distance (l/L) varies between 0.21 and 0.48. The air flow rate in the heater duct has been varied in the range of 0.001 kgs−1 to 0.01kgs−1 (Reynolds number ranges from 350 to 3500), while other thermal specifications such as inlet, outlet, and plate temperatures have varied due to weather changes. Results of this study have been compared with those related to smooth ducts and other literatures, and the maximum enhancement in Nusselt number is observed to be approximately five times of that of the smooth duct under similar flow conditions. Finally, thermal efficiency of the device for different case studies has been determined and compared with other researches.

Commentary by Dr. Valentin Fuster
2010;():583-590. doi:10.1115/ESDA2010-24485.

In this paper, a new designed internal heat exchanger (suction-liquid line heat exchanger) for R134a automotive air conditioning system is proposed, and is studied experimentally. The approval is done by calorimeter test apparatus, which provides conditions close to real automotive A/C system operation. In this design, the high-pressure liquid passes through central channel and the low-pressure vapor flows in several parallel channels in the opposite direction. The results show that in all conditions, internal heat exchanger adoption will increase the condenser real capacity. Therefore, smaller condensers can be used to reach the same capacities. Using the designed internal heat exchanger will decrease the needed mass flow rate. In a constant mass flow rate, internal heat exchanger adoption will increase evaporator capacity. In all concluded tests, the compressor power consumption was decreasing by internal heat exchanger adoption; it was intensifying at higher air temperature passing through the condenser. Using this internal heat exchanger will decrease compressor power consumption up to 6%, and will increase mostly the coefficient of performance. The condenser higher air temperature will increase the coefficient of performance and its improvement with internal heat exchanger. In this case the coefficient of performance can increase up to 8.4%, and will enhance subcooled degree at expansion valve inlet up to 12.8°C.

Commentary by Dr. Valentin Fuster
2010;():591-599. doi:10.1115/ESDA2010-24493.

Carbon black has been widely used in industry, especially in rubber and plastic production. The present study is concerned with measuring and simulating the carbon black formation process in Propane-air and Acetylene-Air diffusion flames. The carbon black concentrations in the furnace have been measured by means of a soot pump and gravimetric method. The flue gas analysis is also done by means of Testo XL-350 Gas Analyzer. The numerical predictions are carried out with the CFD code, Fluent. The chemical reaction formulation relates the production of the carbon black to the incomplete combustion and pyrolysis of propane and Acetylene as both the main gas and the feedstock. The effects of feedstock mass flow rate, the position of feedstock injection, the feedstock material and the shape of the furnace on carbon black are studied. The results show the effect of temperature on soot and carbon black formation in which as the temperature increases the soot and carbon black mass fraction is also increased. The results also show that as the feedstock mass flow rate increases the formation of the carbon black is increased up to point where the mass flow rate of feed stock is three times greater than the mass flow rate of the main gas and after that the carbon black production rate starts decreasing because of the decreasing of temperature due to cold fuel injection to the furnace. The position of feedstock injection affects the mixing process of air and fuel, and complete mixing causes the temperature to be increased. The injection of feedstock in the pre-combustion zone influences the maximum of the flame temperature. As the hydrocarbon initially pyrolyzes to acetylene and afterwards acetylene breaks into soot and carbon black in the present study acetylene is used as feedstock, the results show huge increasing of soot and carbon black mass fraction in the products. The results also show that predictions and the experimental measurements are in good agreement.

Commentary by Dr. Valentin Fuster
2010;():601-606. doi:10.1115/ESDA2010-24544.

In this paper, we present a numerical study of the flow characteristics and heat transfer mechanism of a non-Newtonian fluid in an annular space between two coaxial rotating cylinders taking into account the effect of viscous dissipation. The Carreau stress-strain relation was adopted to model the rheological fluid behavior. The problem is studied when the heated inner cylinder rotates around the common axis with constant angular velocity and the cooled outer cylinder is at the rest. The horizontal endplates are assumed adiabatic. In-house code which is based on a Galerkin mixed finite element is developed to obtain numerical solutions of the complete governing equations and associated boundary conditions and is validated with the results reported in the literature. It is found that five parameters can describe the problem under consideration, the Reynolds number (Re), the Grashof number (Gr), the index of structure (n), Weissenberg number (We) and the Eckert number (Ec). The velocity, temperature and stream function distributions and the local Nusselt number variations are drawn for different dimensionless groups.

Commentary by Dr. Valentin Fuster
2010;():607-614. doi:10.1115/ESDA2010-24570.

The 3D cross flow between parallel corrugated plates with perpendicular directions of corrugation is numerically modeled as a laminar, incompressible, steady flow. The present work tries to investigate the thermally developing characteristics of the flow in this type of geometry, in the case of constant temperature on walls. The main emphasis is on introducing correlations for saturation efficiency and simply modeling the evaporation process within evaporative coolers with such geometries. The applied numerical method is the Chorin’s artificial incompressibility method and finite difference discretization is used to model the Navier-Stokes and energy equations in a structured mesh. The results show that saturation efficiency decreases with increase in Reynolds number. This also depends on the depth of evaporative media along the flow direction. Increasing the number of waves along the flow direction, results higher saturation efficiencies and also more pressure drop. For a specific saturation efficiency, the overall pressure drop decreases at higher amplitude to wavelength ratios. Also the overall pressure drop grows as the depth of the domain increases. The same trend is observed for experimental data of commercial evaporative pads.

Commentary by Dr. Valentin Fuster
2010;():615-625. doi:10.1115/ESDA2010-24651.

The discrete ordinates method (DOM) for the solution of radiative heat transfer problems have received significant attention and development owing to their good compromise between accuracy, flexibility and moderate computational requirement. However, the DOM suffers from the ray effects related to the discretization of the angular distribution of the radiation intensity. The modified discrete ordinate method (MDOM) proved to significantly mitigate ray effects originated from discontinuities or abrupt changes of the wall temperature. This article presents blocked-off region treatment of irregular geometries using a modified discrete ordinates method in Cartesian coordinates. The Cartesian based 2D algorithm can be used to solve radiative heat transfer in irregular geometries by dividing the region into active and inactive regions. It is easier and convenient way of handling 2D irregular geometries than to write an algorithm in curvilinear coordinates. It is capable of handling participating (absorbing, emitting and isotropic or anisotropic scattering) or non participating gray media enclosed by gray diffuse walls. Both radiative and non-radiative equilibrium situations are considered. The walls of the enclosures can have either heat flux or temperature boundary conditions. Cases with curved and obstacle and radiation shield are considered. Some test problems are considered and results are validated with the available results in the literature. Results are found to be accurate for all kinds of situations.

Commentary by Dr. Valentin Fuster
2010;():627-631. doi:10.1115/ESDA2010-24661.

A numerical study has been earned out to investigate the fluid flow structure and convective heat transfer due to a circular jet impinging on a rotating disk. The temperature distribution and convection heat transfer coefficient on the disk are calculated. Flow is considered to be steady, incompressible and turbulent. k-ε RNG model is used to model the turbulent flow. Two new criteria are introduced and used to evaluate the performance of cooling process which are maximum temperature difference on the disk and the average temperature of the disk. The first parameter shows the uniformity of temperature distribution in the disk and the second shows the effect of both thermo physical properties of the disk material and cooling process. In order to verify the numerical approach, results have been compared with the experimental data which shows a good agreement.

Commentary by Dr. Valentin Fuster
2010;():633-642. doi:10.1115/ESDA2010-24687.

A blocked-off region concept is implemented with the modified discrete ordinates method (MDOM) to solve combined conductive and radiative heat transport problems in irregular geometries. The media analyzed are absorbing, emitting and isotropically or anisotropically scattering. The walls have temperature or flux boundary conditions. The finite-volume method is used to solve the energy equation and the modified discrete ordinates method is employed to solve the radiative transfer equation. The SDOM and MDOM are compared in all cases, and the accuracy of the results is assessed by comparing the results with those obtained by other researchers. The results confirm the capability of the MDOM to minimize the anomalies due to ray effects in combined mode heat transfer problems.

Commentary by Dr. Valentin Fuster
2010;():643-651. doi:10.1115/ESDA2010-24712.

In this study, a computer program is developed to design and compare gasketed plate heat exchangers with double pipe heat exchangers. The computer program is coded in MATLAB. The user interface of the program is prepared in MATLAB Guide. The program uses hot and cold fluid properties as input data and calculates the characteristics of gasketed plate heat exchangers and double pipe heat exchangers designed for the given conditions. The outputs for gasketed plate heat exchanger design include number of plates, effective area, total heat transfer coefficient, pressure losses, pumping power and cost, whereas, the outputs for double pipe heat exchanger selection are: pump power, total number of hairpins, effective area, pressure drop, total heat transfer coefficient and cost. Correlations selected from literature are used in the program for the analysis. Water is selected as the working fluid to be able to make the comparison. The program compares the heat exchangers based on cost, effective area, and pumping power. The computer program is also used to understand and compare operational behaviors of these two heat exchangers under different operating conditions.

Commentary by Dr. Valentin Fuster
2010;():653-661. doi:10.1115/ESDA2010-24760.

In thermoacoustic devices, an acoustic wave interacts with internal solid structures such as thermoacoustic stacks (regenerators), to either produce acoustic power due to an imposed temperature gradient, or to produce a heat pumping effect by an acoustic excitation. A cold and hot heat exchangers are usually placed on either side of these internal solid structures to enable heat communication between the thermoacoustic devices and their surroundings. Heat exchangers of various geometries have been extensively studied in steady flows and results are available from a collection of published articles and handbooks. However, there is still a lack of data for heat exchangers in an oscillatory flow, because the interaction of oscillatory flow with the solid boundary is governed by complicated fluid flow and heat transfer processes that are not fully understood. This work is a step towards a better understanding of the heat transfer mechanisms in the acoustically induced oscillatory flow within thermoacoustic systems, in particular obtaining the quantitative description of the heat transfer between heat exchangers and the stack. The assembly of a stack and heat exchangers is replaced by a simplified “stack-less” pair of heat exchangers, in order to focus on the generic heat transfer processes rather than the intricacies of practical thermoacoustic systems. The fins of the hot and cold heat exchangers are kept at constant temperatures by virtue of resistive heating and water cooling, respectively. Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) are used to obtain the temperature and velocity fields around the fins. The heat flux between the heat exchanger fins and the fluid is analyzed phase-by-phase. The time dependent local heat transfer coefficient is obtained from the temperature gradient in the thermal boundary layer. The measurements are conducted at various levels of acoustic excitation in order to study the correlation between the non-dimensional heat transfer coefficient Nu and the Reynolds number. The effect of the flow behaviour at the end of the plates on the temperature field in the region is also studied. It is hoped that this work could lead to a better understanding of heat transfer on short plates in the acoustically induced oscillatory flows.

Commentary by Dr. Valentin Fuster
2010;():663-670. doi:10.1115/ESDA2010-24820.

An innovative Counter-Flow Sand Heat Exchanger (CFS-HX) is proposed, which makes use of very small solid particles as intermediate medium to perform heat transfer between two gas flows at different temperature. The potential of the CFS-HX was already demonstrated by the authors, both theoretically and experimentally. In this work, a parametric study has been employed in order to explore the capabilities of the proposed heat exchanger. A 1D model (validated by experiments) has been extensively used to perform sensitivity analyses with respect to the major design parameters, i.e.: specific heats, gas and sand densities, particle diameter, prescribed efficiency. Pipe length to obtain a prescribed heat exchanger efficiency has been calculated for a large number of configurations and results have been compared with a baseline case. The proposed computations show that a high efficient heat exchange can be obtained with relatively short pipes and with negligible pressure drop.

Commentary by Dr. Valentin Fuster
2010;():671-677. doi:10.1115/ESDA2010-24892.

In this study we develop P roper O rthogonal D ecomposition (POD) models for combined steady and transitional (quasi-periodic) convective air flows in a grooved channel with periodic boundary conditions. The grooved channel is appropriately mounted with constant heat flux sources. The constructed POD models for the flow and temperature fields are used in order to predict the off-design flow conditions. Considering the grooved channel geometry (with the height of the heat source H = 2.3 cm and the distance between the heat sources L = 3.0 cm), we form a database using a combination of three distinct databases. Thus we could compare the ability of a POD model applied to the combined database consisting of various flow regimes. The first database consists of steady flow fields with varying Reynolds number up to Re = 230. The second and third databases include instantaneous snapshots of a periodic flow field at Re = 300 and snapshots of a quasi-periodic (chaotic) flow field at Re = 1000 respectively. Then, the combined database is used to perform the POD analysis and extract the POD modes. The modes of the flow and temperature fields are used for off-design reconstructions. The performance of POD model for off-design conditions is evaluated. The mode coefficients are interpolated by kriging to predict off-design conditions. We show that POD model can be used as a useful tool to predict the flow and heat transfer at off-design conditions and to solve inverse design problems in thermo-fluids.

Commentary by Dr. Valentin Fuster
2010;():679-686. doi:10.1115/ESDA2010-24961.

The paper presents the theoretical and experimental aspects concerning the droplet evaporation processes from the liquid jet, sprayed in an air vapour mixture. From the particularities of the transfer phenomena involved in the droplet evaporation, the lifetime evolution of this, as a function of liquid temperature, its dimension and the surroundings humidity, is displayed. The surroundings consist in a semi-open room in which we may control the entry of the fresh air. Based on these theoretical approaches the test bench was developed. The aspects regarding the experimental tests are mentioned as the jet development followed by the evaporation quality. The experimental diagrams concerning the chart of temperature and humidity inside and near the two-phase jet are shown. The practical values of the measured parameters allow us to use the jet device with a warm liquid in the extinguish system. The tests were realised with various liquid temperature for the gaseous hydrocarbon flame. From the experiment it was observed that the liquid phase in contact with the flame evaporates instantaneously forming the superheated vapour. Consequently, the vapour huge volume generated on this way will decrease the oxygen concentration in the mixture, which may fall it under the ignition limit. On the other hand, the surrounding temperature reduces due to the heat absorption during the liquid evaporation. These two phenomena, which act on the flame, rise the extinguish efficiency of the two-phase jet.

Commentary by Dr. Valentin Fuster
2010;():687-693. doi:10.1115/ESDA2010-25042.

The energy crisis in the last two decades has turned the attention of scientific and engineering communities to redesigned and developed heat-fluid interaction systems. All of the details in analyses are reconsidered to reduce energy consumption. The present work examines the effects of temperature and velocity jump conditions on heat transfer, fluid flow over a single rotating disk. The flow due to rotating disks is of great interest in thermal engineering as it appears in many industrial and engineering applications such as gas turbine engines and micropumps. The related equation of flow, which is nonlinear and coupled, and heat transfer governing equations are reduced to ordinary differential equations by applying the so-called classical approach which was first introduced by Von Karman. Instead of this approach, a pure numerical one, the recently developed popular semi numerical analytical technique differential transform method (DTM), with Benton transformation, is employed to solve the reduced governing equations under the assumptions of velocity-slip and temperature jump conditions on the disk surface. The solution is valid for continuum and slip-flow regime which has a Knudsen number smaller than 0.1. The results attained for various physical cases are interpreted by using non-dimensional parameters related to flow and temperature fields. Velocity and temperature profiles are presented graphically. The effect of various parameters such as the Knudsen Number (Kn), Reynolds Number (Re) and Nusselt Numbers (Nu) are examined. The observed physical consequences are the velocity slip and temperature jump at the wall becoming strongly dependant on the Knudsen number. It is also observed that the temperature jump and velocity jump conditions have nonlinear effects on slip; these effects are investigated with great details and presented graphically.

Commentary by Dr. Valentin Fuster
2010;():695-702. doi:10.1115/ESDA2010-25080.

Busbar technology is more and more used to realize connections within power supply systems in answer to the need of compactness. The integrated problem on heat conduction and radiation-convective heat exchange describes the temperature regime in current conductors and current carrying busbars of power electrical apparatus such as circuit breakers or high breaking capacity fuses. Beside steady-state conditions, the transient thermal regime of busbar has an important influence upon whole power supply system from thermal behaviour point of view. Hence, a 3D thermal analysis of a power system including fuse, low voltage circuit breaker and busbars connections, using a specific software package based on Finite Element Method, has been done. From 3D thermal modelling and simulations, the thermal transient impedance for the busbar has been computed. This allows a better correlation between protection characteristics of the fuse and circuit breaker and busbar design.

Commentary by Dr. Valentin Fuster
2010;():703-710. doi:10.1115/ESDA2010-25173.

Temperature variation phenomena observed inside the metallurgical tundish in the continuous casting is principally due to several factors, high temperature of the ladle metal jet, important thermal losses, heat transfer between molten steel and tundish walls and more still, in contact with the slag layer at bath surface and if necessary cooling or warming in refining composition operations. A numerical simulation using the CFD code “Fluent” is realised. Investigation of heat transfer—which has a great importance in the natural convection and the inclusions floating at slag surface—, is proposed. Results are presented for three arrangements of the tundish, where the interest and role of the control devices is improved.

Commentary by Dr. Valentin Fuster
2010;():711-718. doi:10.1115/ESDA2010-25192.

This paper aims to numerically investigate the effects of adding nanoparticles on the entropy generation of water-Al2 O3 nanofluid flows through a circular pipe under constant wall temperature also constant heat flux thermal boundary conditions in laminar regime. Approved formulations of mixtures are used for density and specific heat of the nanofluids. Nanofluid model proposed by Koo and Kleinstreuer [1] based on experimental data of Das et al. [2] is employed for conductivity of the nanofluids and an experimental correlation presented by Rea et al. [3] is used to model the viscosity of the nanofluid. The problem has been simulated numerically using a CFD finite-volume code and results are validated with the available experimental data. It is found that for the case of constant heat flux boundary condition, adding nanoparticles decreases the entropy generation and improves the thermal performance of water-Al2 O3 flow. Moreover optimum Reynolds number to minimize the ratio of nanofluid entropy generation number to water is obtained for this case. For the case of wall constant temperature boundary condition, adding nanoparticles to water leads to heat flux increase, therefore the entropy generation number remains approximately constant.

Commentary by Dr. Valentin Fuster
2010;():719-731. doi:10.1115/ESDA2010-25235.

A nanofluid is defined as the suspension of nanoparticles in a base liquid. Studies in the last decade have shown that significant amount of thermal conductivity and heat transfer enhancement can be obtained by using nanofluids. In the first part of this study, classical forced convection heat transfer correlations developed for pure fluids are used to predict the experimental values of heat transfer enhancement of nanofluids. It is seen that the experimental values of heat transfer enhancement exceed the enhancement predictions of the classical correlations. On the other hand, a recent correlation based on the thermal dispersion phenomenon created by the random motion of nanoparticles predicts the experimental data well. In the second part of the study, in order to further examine the validity of the thermal dispersion approach, a numerical analysis of forced convection heat transfer of Al2 O3 /water nanofluid inside a circular tube in the laminar flow regime is performed by utilizing single phase assumption. A thermal dispersion model is applied to the problem and variation of thermal conductivity with temperature and variation of thermal dispersion with local axial velocity are taken into account. The agreement of the numerical results with experimental data might be considered as an indication of the validity of the approach.

Commentary by Dr. Valentin Fuster
2010;():733-742. doi:10.1115/ESDA2010-25237.

The need for maximizing the performance of micro-mechanical systems and electronic components has resulted in a trend of minimization. Minimized sizes and dimensions have come along with a complex heat transfer and fluid problem within these devices and components. For a variety of fields in which these devices are used, such as; biomedicine, micro fabrication, and optics, fluid flow and heat transfer at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making some extensions to the conventional theories by including the scaling effects that become important for microscale. Studies performed in the last decade have shown that, some of the effects that are thought to become significant for a microscale gas flow are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, the temperature variable thermal conductivity and viscosity may become important in microscale gas flow due to the high temperature gradients that may exist in the fluid. Therefore, effects of variable thermal conductivity and viscosity in microscale gas flow and convection heat transfer are investigated in this study. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in a micro gap between parallel plates is numerically analyzed. In the analyses, scaling effects such as rarefaction, viscous dissipation, and axial conduction are taken into account in addition to the temperature variable thermal conductivity and viscosity.

Commentary by Dr. Valentin Fuster
2010;():743-748. doi:10.1115/ESDA2010-25336.

This paper reports a compact nanostructure based heat sink. The system has an inlet and an outlet valve similar to a conventional heat sink. From the inlet valve, pressurized deionized-water is propelled into a rectangular channel (of dimensions 24mm×59mm×8mm). This rectangular channel houses a nanostructured plate, on which ∼600 nm long copper nanorod arrays with an average nanorod diameter of 150 nm are integrated to copper thin film coated on silicon wafer surface. Forced convective heat transfer characteristics of the nanostructured plate are investigated using the experimental setup and compared to the results from a flat plate of copper thin film deposited on silicon substrate. Nanorod arrays act as fins over the plate which enhances the heat transfer from the plate. Excess heat generating small devices are mimicked through a small heat generator placed below the nanostructured plate. Constant heat flux is provided through the heat generator. Thermocouples placed on the heater surface are utilized to gather the surface temperature data. Constant pressure drop across the heat sink and constant heat flux values are varied in order to obtain the correlation between heat removal rate and input power. Volumetric flow rate was measured as a function of the constant pressure drop. In this study, it was proved that nanostructured surfaces have the potential to be a useful in cooling of small and excessive heat generating devices such as MEMS (Micro Electro Mechanical Systems) and microprocessors.

Commentary by Dr. Valentin Fuster
2010;():749-756. doi:10.1115/ESDA2010-25363.

Ice formation on airplane wing profile is a very dangerous condition because of the change in the profile aerodynamic, so it’s necessary to avoid ice formation on the wings. The hardest condition ice formation are at altitudes between 10.000 and 15.000 ft and at temperature between 0° C and −15° C, because they are particularly suitable for ice formation. In this paper an anti-icing system based on hot air impinging jets on internal wing surface is analyzed in order to check the efficiency of the system. A numerical model is given in order to evaluate the thermal and fluid dynamic behaviors of the impinging jet inside the wing panel. A wing profile with an angle of attack of 4.50° is taken into account with a free stream temperature of 258 K. A piccolo tube with a diameter of 1.00 inch and air temperature of 523 K and at variable distance from the wall of the wing profile, is considered for anti-icing system. A structured mesh is used in the discretization of the computational domain for the two-dimensional and three-dimensional case. A steady state solution with k-ε RNG turbulent model has been found. Numerical simulations of a two and a three dimensional model of an aircraft wing has been carried out taking into account the external convective exchange by means of an average coefficient on the external surface and thermo-fluid dynamic field inside the wing due to the anti-icing system. The analysis is performed by means of the FLUENT code in order to find the optimal geometrical configuration to avoid the ice formation on the external wing surface. Results are presented in terms of temperature fields and wall temperature and air velocity profiles along the wing surfaces.

Commentary by Dr. Valentin Fuster
2010;():757-764. doi:10.1115/ESDA2010-25374.

In this study, the cooling performance of a flash pumped laser using Nd:YAG was investigated. The examined system is used to cool down the laser head of a range finder device where heat is produced. Three dimensional CFD model for the examined system was generated and the results were verified by using experimental study. The transient approach and k-epsilon turbulence model were used during the computational analysis. It was realized that the result were in good consistency. At the end of the verification, it is found that the use of extended surfaces on the heat sink does not enhance the heat transfer from the surface in 3 minutes during transient phase because of low thermal diffusivity of titanium material and the undesired high temperature values were seen. Then the cooling system was modified. As a result more reliable cooling system is developed. The enlargement of the liquid flow channels increases the heat transfer and reduces the heat sink temperatures with addition of negligible pressure drop.

Topics: Cooling , Lasers
Commentary by Dr. Valentin Fuster
2010;():765-773. doi:10.1115/ESDA2010-25432.

Heat transfer in small scale media is a phenomenon that has been increasingly scrutinized in the past few decades. Refrigerant flow in microscale tubes and channels is a promising solution to be used in future refrigeration technology. Experimental studies are significant for the rating of the heat transfer and pressure drop in a given channel, and are important tools for optimizing applicable designs. An overview of the previous studies in this area has shown that most of the research does not focus on the low mass flow rates encountered in household refrigeration systems. In the current study, heat transfer in a copper tube with 1.65 mm inner diameter with two-phase R134a flow is experimentally investigated under low mass flow rate conditions. In the set-up constructed, instead of constant wall heat flux, which is the boundary condition mainly used in the microscale heat transfer studies in literature, constant wall temperature approach is applied. The experimental procedure is designed to focus on the temperatures and the flow rates observed during evaporation in a typical household refrigeration cycle. Since the flow is in the two-phase region, experiments for different quality values of R134a are conducted by pre-heating the refrigerant at different saturation temperatures and pressures. In microscale flow, a major problem is the increase in pressure drop compared to conventionally-sized channels, and the two-phase flow regime contributes to this increase. Therefore, in addition to the heat transfer, the pressure drop of the refrigerant along the tube is also measured. Thus, for various quality values, the pressure drop and the heat transfer for the refrigerant flow are examined. The experimental data obtained will be useful information for the two-phase flow modeling and the model verification.

Commentary by Dr. Valentin Fuster

### Science, Engineering and Education

2010;():775-780. doi:10.1115/ESDA2010-24057.

To be successful in one’s profession, an engineer operating in the contemporary globalized world needs to be adequately equipped with suitable management skills. They include talent to plan, implement and manage engineering projects in diverse and pluralistic teams, ability to communicate at different levels, perseverance in the face of failures and crisis, creativeness to improvise innovative solutions, maintenance of physical and mental health, ability to invent and implement eco-friendly engineering solutions, and smartness to work within stipulated time-frames, etc. Large residential student communities prepare suitable context for engineering students to nurture their general management skills, if carefully planned. In the current paper, we present some innovative models and appropriate methods to convert large residential student communities into an arena where students can train themselves in general management skills. It also presents some results of two years of implementation of such methods in a men’s hostel, which accommodates youngsters between 17–19 years of age in their first year of undergraduate engineering study.

Commentary by Dr. Valentin Fuster
2010;():781-791. doi:10.1115/ESDA2010-24143.

An investigation has been carried out to examine the level of engineering ethics for senior engineering graduating students. The ethical response to some educational and engineering dilemmas for the graduating students has been collected with a questionnaire designed for this purpose. Dilemmas included educational ones that students see every day in their educational life and professional situations that they are to face upon graduation. Educational dilemmas included many situations such as: their behavior at the university, their selection of the engineering discipline, exam time behavior and honesty with colleagues and instructors. Professional dilemmas included their behavior with their colleagues, behavior with their manager, with customers, with deadlines, with free and paid consultations, with life long learning, with efforts-salary relation and with indirect bribery. Students’ response with respect to all dilemmas and on projection to the professional standards are presented and analyzed. It has been shown that exposing students to such dilemmas could be a useful learning tool for engineering ethics.

Commentary by Dr. Valentin Fuster
2010;():793-801. doi:10.1115/ESDA2010-24213.

In this paper is described the main ideas of national project “KEGA 3/7131/09 – Laboratory of production system program control”. This project is focused to build of virtual laboratory and supplemental e-learning documents for several studying subject at our institute. This project being solved in the Institute of Production Systems and Applied Mechanics, Faculty of Materials Science and Technology – STU in years 2009–2011 includes an opportunity to acquire and improve abilities and skills the employers expect technical university graduates to have. The project target is to create a virtual laboratory of programmable control systems and a suitable teaching system supporting creation and improvement of key and occupational competences, abilities and skills of students in technical fields of study promoting at the same time their preparation for practice and lifelong education.

Commentary by Dr. Valentin Fuster
2010;():803-809. doi:10.1115/ESDA2010-24494.

Nowadays, the Web is a common tool for students searching information about the subjects taught in the different university courses. Although this is a good tool for the first rapid knowledge, a more deep study is usually demanded. After many years of teaching one course about ceramic and composite materials, the authors, used the Bologna reformulation of the mechanical engineering course to introduce new teaching methodologies based on continuous evaluation. One of the main innovations is one practical work that comprises the study of a recent ceramic scientific article, using all the actual available tools, elaboration of a scientific report, present the work and participate in a debate. With this innovative teaching method the enrolment of the students was enhanced with a better knowledge about the ceramics subject and the skills related with the CDIO competences.

Commentary by Dr. Valentin Fuster
2010;():811-814. doi:10.1115/ESDA2010-24502.

Some of celebrated geometers whom are acknowledged as to be the pioneers of scientific revolution have worked on acoustics and modeling of vibration of structures. They made great contributions on both the physical understanding and the mathematical modeling of these phenomena. The historical stream of physical understanding of sound propagation, foundations of the mathematical background of vibration mechanics and the instruments that reinforced the conceived theory of acoustics led to the advanced concept of modern vibro-acoustic engineering. A historical investigation is made on the early engineering approaches on vibro-acoustic engineering problems to comprehend the evolution of acoustic engineering and its place in modern era.

Topics: Acoustics
Commentary by Dr. Valentin Fuster
2010;():815-822. doi:10.1115/ESDA2010-24727.

The paper presents the results of the responses of a concrete trough of a new lightweight rail track system (LR55) to full scale non destructive tasting. The system which is made from three main components; low profile steel rail, elastomeric pad and prestressed concrete trough is developed for light rail transits in cities streets, which can significantly help in improving the traffic flow, reducing the traffic congestion and thus providing opportunities for minimising serious environmental problems such as level of noise, vibration and air pollutions and in this regards it can be considered as environmentally friendly means of transport. A mathematical model was developed where the LR55 track system was treated as multilayer beams on elastic foundations, and the model was then validate experimentally through a series of non-destructive tests on full scale model subjected to a full scale service load specified by the current BS codes of practises.

Commentary by Dr. Valentin Fuster
2010;():823-829. doi:10.1115/ESDA2010-24827.

A device that levitates a steel ball beneath an electromagnet is used for educational purposes at the United States Military Academy, West Point, New York. Students in the course “Mechatronics” engage in a set of laboratory exercises with the device to reinforce classroom learning. Mechatronics is a senior-level course that introduces the interdisciplinary design of smart systems. Students in the electrical engineering and mechanical engineering programs take the course together, and the material is taught by a team of instructors from both academic departments. The Magnetic Levitation experiments are the primary means of teaching the classical analog control portion of the course. Other aspects of the course involve interfacing microcontrollers with sensors and actuators, and digital control. The magnetic levitation device fits easily on a two-person workbench and requires a power supply and oscilloscope. An infra-red emitter / detector pair is used to sense ball position for a feedback compensator. Students first learn classical control theory in a co-requisite course, “Dynamic Modeling and Control.” Modeling principles are introduced in the context of the magnetic levitation system as an unstable plant to be controlled. The system can be simulated by models ranging from simply linear to more complex to teach the trade-off between model fidelity and model development effort. The students derive the nonlinear governing equations and then linearize the equations and develop the transfer function of the plant. Students design a compensator and simulate the resulting stabilized system with Matlab and Simulink software. Students build their compensator on a solderless project board to levitate the steel ball. A proven lead-type compensator using two resistors and a capacitor is readily provided to students that struggle with their own compensator design so that all teams may enjoy the fruit of a successful experiment. As a laboratory aid, the magnetic levitation system allows for basic and advanced approaches to both theoretical study and practical investigation of a nonlinear, unstable system control. The comparison of measured results to predicted behavior leads to insight about how the physical system is modeled by mathematics. Students write a case study describing the system in detail including characterization of the sensors and actuators. Instructors report that the hands-on nature motivates students to excel. Surveyed students cite the hands-on activities as relevant applications that help develop deeper understanding and greater appreciation for the concepts learned in the classroom. The students are motivated to learn by the fascination of defying gravity.

Commentary by Dr. Valentin Fuster
2010;():831-840. doi:10.1115/ESDA2010-24883.

The pattern of Portuguese Industry is typically composed by small and medium sized enterprises. In many cases, the dimension of these companies unable a general innovation culture for their products, with their own human resources. In these cases, innovation can successfully be achieved through suitable cooperation models and technological transfer between Universities and/or its Research and Development (R&D) Interface Organizations. This paper describes a successful model of cooperation between a hybrid private/public Institute, INEGI, with more than 60 Industrial Associates and National and International Industrial Companies. It is also shown the advantage of having industrial R&D Projects running inside the Faculty and the benefits obtained with the involvement of students in these projects. Examples are presented with paradigmatic projects, with high industrial impact, leading to effective competitive growth, both on Portuguese and International companies. The intervention areas of these projects cover a large variety of multidisciplinary topics, from renewable energies, processes and mechanical systems development, composite structures, rapid prototyping and advanced technologies, industrial management, to the creation of technological spin-offs.

Commentary by Dr. Valentin Fuster