ASME Conference Presenter Attendance Policy and Archival Proceedings

2017;():V002T00A001. doi:10.1115/IMECE2017-NS2.

This online compilation of papers from the ASME 2017 International Mechanical Engineering Congress and Exposition (IMECE2017) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Advanced Machining and Finishing

2017;():V002T02A001. doi:10.1115/IMECE2017-70021.

The machining of complicated surface is a hot spot in manufacturing industry in nowadays. The complicated surfaces should be machined with five-axis machine tools because of its geometric characteristics. In this paper, the characteristic of workpiece surface called open and close angle of surface is defined. The transition area from open angle to close angle will cause the twist and singularity of the surface. The twist mainly affects the principle errors of surface. And the singularity will cause the mutation of rotation axis movement and make an influence on the contour errors. To test the influence of the open and close angle on the contour error, a workpiece with special surface characteristics is designed. With the theoretical, simulational and experimental analyses, the influence law from the open and close angle is found out. The conclusion can be helpful for the tool trajectory planning.

Topics: Errors
Commentary by Dr. Valentin Fuster
2017;():V002T02A002. doi:10.1115/IMECE2017-70098.

Metal Matrix Composites (MMCs) based on Aluminum Alloys 2024, 6061 and 7075 reinforced with Graphene was fabricated using powder metallurgy process followed by hot extrusion process. The extruded samples were used for conducting the turning experiments to evaluate the machinability of the developed composites. Turning experiments were conducted in ACE Micromatic made CNC lathe as per the Design of Experiments (DOE) designed using L18 Taguchi’s mixed orthogonal array. Uncoated and DLC coated carbide inserts, along with three levels of cutting speeds, feed rates and depths of cut were considered for the turning experiments. During the experiments the cutting force generated was recorded “online” and subsequent to the experimentation the surface roughness generated on the work piece and the surface hardness for every trial were recorded. The influence of the cutting tool material and other cutting parameters on the machinability of composites was analyzed using ANOVA. The microstructural observation on the surface of the machined specimen reveals the detachment of reinforcement materials from the composite and their impact of the surface quality.

Commentary by Dr. Valentin Fuster
2017;():V002T02A003. doi:10.1115/IMECE2017-70115.

Particle-reinforced metal matrix composites (pMMC) such as silicon carbide particle reinforced aluminum alloys (SiCp/Al) require special cutting tools due to the high hardness and abrasive properties of the ceramic particles. Diamond coated cutting tools are ideal for machining this type of pMMC. Previous research studies focus on the machinability of pMMCs with low ceramic content. The aim of this research is to determine the optimal cutting parameters for machining SiCp/Al material containing high silicon carbide particle reinforcement (>25%). Material removal rate (MRR) was used to determine the optimal cutting parameters with the tool wear and surface roughness as constraints. Cutting speed, feed rate, and depth of cut were used as design parameters for the design of experiment. High burr formation and cutting forces were observed during the experiments. Experimental milling tests are conducted using CVD diamond coated end mills and non-diamond tungsten carbide end mills. It was found that low tool rotation speeds, feed rates and depths of cut are necessary to achieve smoother surface finishes of Ra < 1 μm. A high MRR to low tool wear and surface roughness ratio was obtainable at a tool rotation speed of 6500 r/min, feed rate of 762 mm/min, and depth of cut of 3 mm. Results showed that a smooth surface roughness of the workpiece material was achieved with non-diamond tungsten carbide end mills, however, this was at the expense of extreme tool wear and high burr formation. An endurance test was run to test for complete tool failure.

Commentary by Dr. Valentin Fuster
2017;():V002T02A004. doi:10.1115/IMECE2017-70119.

Dynamic deformation of thin-walled structure during side milling is investigated in present paper. The component is modeled as a cantilever plate while the milling force is modeled as a moving excitation for the component. Classical plate theory is employed to construct the component motion equations. Modal superposition method is employed to solve the equation to obtain the dynamic deformation. At last, experiments and simulation are implemented, results of digital simulation and experiments are compared and they matched well with each other, which demonstrates the validation of the method for computing dynamic deformation in this paper. Moreover, analyzed results in this paper are also compared with FEM results which were obtained by other investigators and shows better accuracy.

Commentary by Dr. Valentin Fuster
2017;():V002T02A005. doi:10.1115/IMECE2017-70689.

This work reports on an empirical study to account for the effects of the drilling parameters of cutting speed: V, m/s (max at the outer periphery), tool feed (f, mm/rev)), and drill diameter (D, mm) on the generated thrust (T, N) and torque (M, N.m). A total of 50 drilling tests were conducted on a vertical machining center based on design of experiment (DOE) test matrix using JMP-SAS/STAT® software. The test matrix employed 2 different aluminum alloys: one wrought (6061-T6) and another cast (A356-T6) with both tempered to the T6 condition. Two classical chisel drills of different diameters (10mm and 12.7mm) were used. Drilling parameter variables employed varied from very mild to very aggressive combinations including 5 values of spindle speeds (796, 1592, 3183, 6366, and 9868 rpm) and 5 values of drilling feeds (0.04, 0.08, 0.16, 0.32, 0.64 mm/rev). Drilling forces and torques were recorded using a 4-component dynamometer (Kistler model 9123) at sampling rate of 200 Hz. At full drill engagement, cutting torque and thrust status were identified for each drilling test case.

By fitting to the measured drilling forces, power law equations with parametric variables D, f, and V are developed. Initial values of the model’s power coefficients were initially identified using Matlab® using a least square optimization function with target to minimize the difference between the predicting model and the experimental data. These values were fed as initially-guessed values to the nonlinear modeling Gauss method in JMP-SAS/STAT® with 50 observations for each set of experiments. For both torque and thrust and for both aluminum alloys employed, the model’s coefficient values were identified setting the convergence criteria to 10−15 with total of 60 iterations. For both thrust and torque, it was found that the power coefficients for feed and cutting speed are statistically significant (better than p-values < 0.05) with values of about 0.7 and −0.1, respectively.

Commentary by Dr. Valentin Fuster
2017;():V002T02A006. doi:10.1115/IMECE2017-70846.

The geometric error is an important indicator for the product performance in the Wire Electric Discharge Machining (WEDM) process, however, few studies have focused on the geometric error caused by thermal deformation, which can reach as high as 6.5% when machining thin-wall components. In this paper, some complex thermal deformation phenomena were found and analyzed in wire electric discharge machining different materials under different conditions (such as different thickness, various process parameters). Based on a large number of experiment, the reasons for these thermal deformation were figured out by studying the effect of various process parameters on thermal deformation and mechanical properties of thin-wall components, and the results revealed that the water pressure and pulse duration are two most significant factor influencing the thermal deformation. It’s concluded that a long pulse duration for rough cut and a short pulse duration for trim cut under low water pressure is recommended to decrease the geometric error caused by thermal deformation.

Commentary by Dr. Valentin Fuster
2017;():V002T02A007. doi:10.1115/IMECE2017-71147.

Electrochemical micromachining process is one among the successful micromachining technique, which uses the electrochemical energy and is recognized for machining difficult-to-cut materials. One such material is Nimonic 75 alloy, which is used to make gas turbine components. In this study, an effort has been made to machine micro-hole profiles in Nimonic 75 with a thickness of 500 μm using two different electrolytes. A combination of sodium bromide, hydrofluoric acid and ethylene glycol has been chosen as the first electrolyte, while the second is a combination of sodium chloride and sodium nitrate. Solid tungsten carbide of diameter 500 μm is used as the tool in each case. For layout of experiments, Taguchi orthogonal array was chosen with following input parameters namely voltage, micro-tool feed rate and duty cycle. Performance characteristics such as material removal rate, overcut and conicity have been assessed for each electrolyte. Experimental results have shown that the first electrolyte yields lower values of overcut (OC) and conicity, whereas the second electrolyte gives higher material removal rate (MRR). Further, the optimal combinations of process parameters have been found by implementing the TOPSIS procedure and the results were found to be in good agreement with the experimental outcomes.

Commentary by Dr. Valentin Fuster
2017;():V002T02A008. doi:10.1115/IMECE2017-71238.

The manufacturing of hard and refractory materials such as ceramics, glass or carbide poses particular challenges on tools and machines. The Sauer Limited a company of the DMG Mori Corporation has developed ultrasonic tool holders working in a frequency range from 15 to 60 kHz. The ultrasonic vibrations are superimposing the tool movement in the tool axis especially for the application on special materials. This technique causes a structural weakening in the contact area and facilitates the machining. For these special materials, a force reduction, mainly in drilling into carbide with diamond tools, of up to 30 percent is possible. This made the authors try to expand the application range of this method. To achieve evaluable results, the authors decided to start working with existing processes. This also makes it easier to understand the mechanism of the positive influence of the ultrasonic assistance. It is difficult to compare a grinding process of hard and brittle materials to the drilling of steel as these two operations are different in many ways. In the first case of investigation, the authors use tools with geometrically undefined edges, where as in the second case, the edges are geometrically defined. To get valid results of the tests, it has then been decided to investigate drilling. This manufacturing method anticipates the best results. The main target of the investigation is to reduce the cutting force. It is measured with a force measurement platform underneath the workpiece. Concerning the direction of the ultrasonic assistance, the authors expect lower cutting forces, longer endurance of the tool, a reduction of the burr height and a better surface quality in the drilling process. To verify the frequencies and the amplitudes, an FFT-analysis is performed. This analysis shows the increase of the damping. This raise depends on the infeed rate of the tool and thus reduces the amplitude of the cutting force.

Commentary by Dr. Valentin Fuster
2017;():V002T02A009. doi:10.1115/IMECE2017-71256.

The RPM-Synchronous Grinding process offers new possibilities to generate defined macro- and micro-geometries on workpieces. With present technology, various macroscopic non-circular geometries must be grinded subsequently in an oscillating process where the X-axis is coupled with the rotary workpiece-spindle axis. Such workpieces can be machined in an ordinary plunge grinding process by implementing the approach of RPM-Synchronous Non-Circular Grinding. Therefore, the workpiece and the grinding wheel rotational rates are in a fixed ratio. A non-circular grinding wheel is used to transfer its geometry onto the workpiece. The authors use a unique machine tool for basic research and control concept development for RPM-Synchronous Grinding (RSG). The machine was especially designed for this RSG technology. Highest revolution rates on the workpiece spindle are mandatory for its success. The grinding approach is performed in a two-step process. For roughing, a highly porous vitrified bonded grinding wheel with medium grain size is used. It ensures high specific material removal rates for producing the non-circular geometry on the workpiece efficiently. A control algorithm adapts this process step, which uses acquired data from a piezoelectric three-component force sensor fixed at the tailstock-side of the grinding machine. For finishing, a grinding wheel with fine grain size is suited. This process step is tuned by a digital process adaption strategy. Roughing and finishing are performed consecutively among the same clamping of the workpiece with two locally separated grinding spindles.

With the presented control and adaption concepts for RPM-Synchronous Grinding, a significant increase in surface quality on the workpiece is attained. The minimization of grinding wheel wear results concurrently. Especially the automotive industry shows big interest in RPM-Synchronous Non-Circular Grinding. This emerging trend in finishing machining opens up various fields of application.

Topics: Grinding
Commentary by Dr. Valentin Fuster
2017;():V002T02A010. doi:10.1115/IMECE2017-71408.

Cocquilhat’s first documented (1851) how heat in a tool shortens the life of the tool. Research since his time has generally concluded that the tool gives up a relatively higher percentage of it’s “cold hardness and toughness” as compared to the work stock. This paper looks at the previously unstudied advantages/disadvantages which may be gained by pre-heating the work stock to a relatively modest temperature, thereby preferentially shifting the ratio/percentages back toward the tool. A widely-used body centered cubic (BCC) steel and a widely-used face centered cubic (FCC) aluminum were chosen to test common commercially machined crystalline structures. The materials were heat treated and/or aged to provide various levels of hardness within the crystalline structures. The selection of two cutting speeds, two levels of cut and three tool rake angles completed the factor level combinations chosen for the study. Parts were preheated immediately prior to the machining operations with an additional resistance heater mounted in the work holder to maintain the temperatures during the trial run. Tensile specimens of all the samples were undertaken to establish the cold working flow stress values of the materials tested. Machining was conducted in a specially modified Cincinnati Horizontal Milling machine using an improved Videographic Quick Stop Device (VQSD) to capture the geometry of the cutting formation simultaneously with the forces in the X, Y and Z-axes using a standard Kistler force plate dynamometer. Utilizing the VQSD greatly increases the number of replicates available for statistical analysis by the metal cutting researcher. This allows for comprehensive multivariate analysis of the data with high confidence (> 95%) in the obtained results. Forces and geometry were collected and analyzed. Wear was measured on the face of each tool using surface profilometers and white light microscopy. The specific horsepower (HPs), also known as the specific cutting energy, normal force (N), and wear rate data indicated there is a definite advantage to be had in pre-heating the workpiece by even a modest amount. In fact, the temperature was a significant prime factor (p-value <= 0.0001, Fstat > 5 with 95% certainty) in all factor level combinations. It was often ranked as the primary number one factor or the number two ranked factor. Many interactions with the temperature were also significant. This, combined with improved tool cooling methods, should result in all tools living a longer time while undergoing less chatter and/or deflection.

Topics: Machining , Alloys
Commentary by Dr. Valentin Fuster
2017;():V002T02A011. doi:10.1115/IMECE2017-72317.

Carbon fiber reinforced plastic (CFRP) composite is one of the most sought after material owing to its superior physical and mechanical properties such as high-durability and high strength-to-weight ratio. CFRP composites are often used by stacking up with titanium (Ti) to form multi-layered material stacks for applications involving extreme mechanical loads. However, machining of CFRP/Ti multi-stacks is quite complex and challenging task since both materials are difficult-to-machine materials and show completely different machinability properties. The challenge is further escalated when there is a need to machine CFRP/Ti stacks at micron level. Several problems arise during the machining process due to the non-homogeneous structure, anisotropic and abrasive properties of composite. Traditional methods of micromachining the CFRP/Ti stacks results in several issues including high cutting force and torque and high tool wear, composite delamination, large groove depth in composite, and poor surface quality. Ultrasonic machining (USM) process has been successfully used to machine titanium, CFRP and CFRP/Ti stack at macro scale. Micro Ultrasonic machining is a downsized version of macro ultrasonic machining process that is developed to machine hard and brittle materials. This research explores the possibility of using Micro USM process to conduct micromachining of CFRP/Ti multi stacks. The effect of various process parameters including abrasive grit size, tool material and type on the material removal process is studied. The study found that micro ultrasonic machining process is capable of successfully micromachining CFRP/Ti stacks with zero CFRP delamination, minimal variation in CFRP and Ti hole sizes and longer tool life. Further, a three-dimensional finite element simulation study is performed on micro ultrasonic machining of CFRP/Ti stacks. The simulation results revealed that the workpiece is not subject to any significant normal stresses during the machining process, while variations in shear stresses is seen on the inside surfaces of the machined cavities.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Applications of High Energy Laser Beams in Surface Processing and Machining

2017;():V002T02A012. doi:10.1115/IMECE2017-70176.

Heat dissipation is considered as a challenging task in the manufacturing field. The main objective of this study is to design a new pressure wheel assembly of a laser weld system to maximize heat dissipation in order to endorse a better performance of the wheel and help achieve a long lasting cycle of life. In this study transient thermal and structural analysis of the pressure wheel is conducted by using ANSYS workbench. The work will examine the effects of geometrical parameters on the thermal performance of pressure wheel assembly during a period of time. Different design models and numerical simulations are performed in investigating the effects of geometrical holes and ventilated discs on the disk on the thermal performance, which include the shape, size, and distribution of pillar posts. The analysis will support the design process in monitoring different models in terms of performance, heat loss and manufacturing cost.

A comparison is made for three different designs and the best design is selected. The calculated results estimated in a period of time of 50 seconds show that the temperature drops with the 3rd design from T = 500 K to 453 K. Also under giving limitations the design with enhanced heat transfer has a better heat dissipation and the temperature decreases to T = 399 K. The present work will help improve the performance of pressure wheel in the welding industry by providing computational results for successive design testing and data validation.

Commentary by Dr. Valentin Fuster
2017;():V002T02A013. doi:10.1115/IMECE2017-70625.

In recent years, a number of research efforts have been devoted to understand the mechanisms and develop accurate simulation models for laser ablation of solid materials. However, uncertainty quantification (UQ) for laser ablation of solid materials, when the sources of uncertainty are inherently stochastic (e.g., material and optical properties of target materials at elevated temperatures), is not sufficiently understood or addressed, despite having critical impact on guiding experimental efforts and advanced manufacturing. In this paper, we consider the problem of UQ for pulsed laser ablation of aluminum. In particular, a generalized polynomial chaos (PC) method is used to incorporate constitutive parameter uncertainties within the representation of laser heat conduction phenomena, where the parameter uncertainties are either presumed from the mathematical modeling approximation for the laser heat conduction model and/or from the laser source. Moreover, numerical simulation studies for laser ablation of aluminum, with nanosecond Nd:YAG 266nm pulsed laser, that demonstrate the proposed generalized PC predictions are also presented. Finally, a sensitivity study is used to identify those parameters that provide the most variance in the thermal and ablation response.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Computational Modeling and Simulation for Advanced Manufacturing

2017;():V002T02A014. doi:10.1115/IMECE2017-70405.

Thermal protection of components such as turbine blades is often done with thermal barrier coatings which are typically ceramic materials. Methods to manufacture ceramic coatings are being developed to create microstructures that optimize thermal protection without degrading mechanical properties of the coating. The coating requires sufficient mechanical properties to remain in place during loads associated with the operation of the component. The work presented in this paper is part of a broader effort that focuses on novel processing techniques. A fabrication method of interest is the inclusion of spherical micron-sized pores to scatter photons at high temperatures along with nano-sized grains to scatter phonons. Pores are sized and distributed so that mechanical strength is maintained. In the current work, yttria-stabilized zirconia (YSZ) is modeled. Three-dimensional microstructures representing YSZ are computationally generated. The defect sizes and orientations are generated to match an experimentally observed distribution. The defects are either randomly or regularly placed in the microstructural models. Stress-displacement analysis is used to determine effective bulk material properties. Comparisons are made to prior two-dimensional work and to experimental measurements available in the literature as appropriate. The influences that defect distributions and three dimensional effects have on the effective bulk material properties are quantified. This work is a preliminary step toward understanding the impacts that micron sized pores, voids and cracks have on thermal and mechanical characteristics. The goal is to facilitate optimizing the microstructure for thermal protection and strength retention.

Commentary by Dr. Valentin Fuster
2017;():V002T02A015. doi:10.1115/IMECE2017-71116.

The in-situ TiB2/7050Al composites is a new kind of particle reinforced metal matrix composites (PRMMCs) with superior properties such as low density, improved strength and increased wear resistance. At present, the study of PRMMCs is focused on the ex-situ SiCp/Al composites, which has been researched from material preparation process to machinability. To the new kind in-situ TiB2/7050Al MMCs, few papers have been published on the cutting performance and finite element method (FEM) simulation. This work involves study on the chip formation and FEM simulation in cutting in-situ TiB2/7050Al MMCs. The orthogonal cutting experiments were carried out in our study. The chip geometric shapes, cutting forces and shear angle were investigated. Meanwhile, the cutting simulation model was established by applying Abaqus-Explicit method to have a deep insight of the chip formation process and mechanisms. The results show that the saw-tooth chips were common found under either low or high cutting speed and small or large feed rate. The mechanisms of chip formation included plastic deformation, adiabatic shear, shear slip and crack extension.

Commentary by Dr. Valentin Fuster
2017;():V002T02A016. doi:10.1115/IMECE2017-71220.

Assembly Fiber-Reinforced Thermoplastic Polymer (AFRTP) is a hybrid material manufactured by injection overmolding of short/long fiber-reinforced thermoplastic resin on the back of continuous fiber-reinforced laminate preformed by thermal stamping to achieve both high mechanical properties and complex geometries. This new technique has attracted large attention from industry recently. The difficulty in applying AFRTP is the progressive damage prediction of heterogeneous interface because the difference in mechanical properties result from materials and process may lead to the interface separation when subjected to bending or tension loads that reduce the bending resistance capability of AFRTP plates. In this paper, the interfacial cohesive parameters of AFRTP structure are identified based on the published experimental data. Additionally, the low-speed impact under three-point bending loads is simulated and the interface stress distribution and failure modes reveal the damage mechanisms of AFRTP interface under shear stress.

Commentary by Dr. Valentin Fuster
2017;():V002T02A017. doi:10.1115/IMECE2017-71225.

In cold spray, bonding forms between a substrate and the particles and between particles through impact deformation at high strain rates. A prominent feature of the cold spray process is the compressive residual stress that arises during the deposition process. Compressive residual stress on the surface can be beneficial for fatigue resistance. As a post processing technique several applications require surface treatment processes that produce this state of stress on component surfaces such as shot peening, laser shock peening, ultrasonic impact treatment, low plasticity burnishing, etc. In all of these methods, the compressive stress is produced through plastic deformation of the surface region. In a similar manner, the cold spray process induces compressive stress by high speed impact of the sprayed particles on the surface, causing a peening effect. The effects of these variations in the properties of the coatings are rarely reported. Moreover, there are some applications which require minimal residual stresses in the components such as in optics. In this study, we have investigated the residual stress using numerical analysis of the multi-particle impact behavior in cold spray.

Commentary by Dr. Valentin Fuster
2017;():V002T02A018. doi:10.1115/IMECE2017-71237.

In the conventional injection molding process a constant temperature of the mold is required depending on the type of injected polymer. Cooling process usually takes 2/3 of the entire production cycle time, so reduction of cooling time should lead to the decrease of the manufacturing cost. In practice, lower mold temperature can lead to the occurrence of the unwanted defects. The most common defects include short shots, diesel effect, visible weld lines, excessive internal stresses and warp. Those defects are more common and evident when injected parts are fitted with thin elastic hinges, where flow of the molten polymer through the very narrow channels causes the shear of polymer chains. In this work, a concept and simulative studies of selectively heated injection molds are presented. The idea of the novel technology is to heat only certain regions of the cavity where molten polymer cools down rapidly or where cavity cross-section is very narrow. It can be achieved with induction heating technology. The results showed that apart from the hinge geometry, the forming temperatures played an important role in shearing of polymer chains. The changes of analyzed parameters also influenced how material filled the cavity.

Commentary by Dr. Valentin Fuster
2017;():V002T02A019. doi:10.1115/IMECE2017-72055.

A numerical method to solve thermal transport problems in powder bed systems and porous materials with finite thermal contact conductance at interfaces between individual powder particles or grains is developed based on the Smoothed Particle Hydrodynamics approach. The developed method is applied to study the effective thermal conductivity of two-dimensional random powder bed systems with binary distribution of powder particles radii. The effects of particle size distribution parameters, density parameter, and effective interface area between particles on the effective thermal conductivity are studied. It is found that at finite Biot number, which characterizes the ratio of the interfacial conductance to the conductance of the bulk powder material, the effective thermal conductivity of porous samples increases with increasing fraction of particles of larger size.

Commentary by Dr. Valentin Fuster
2017;():V002T02A020. doi:10.1115/IMECE2017-72508.

The empirical model of dynamic recrystallization (DRX) coupled with DEFORM 3D® software (based on the finite element method (FEM)) was used to predict the microstructural evolution of the AA7075 processed by four passes of equal channel angular pressing (ECAP) at 250° C. The DRX model parameters were taken from the literature. The simulation results showed that the DRX exhibited a heterogeneous distribution from the back to the frontal part of the sample and this heterogeneity markedly diminished in the fourth pass. The recrystallized volume fraction reached 50% in most of the sample in the fourth pass and the average grain size did not show significant changes, going from an initial value of 16.4 μm to 12.5 μm. This latter result was attributed to the fact that DRX occurred partially even for the last pass. Experimental testing of ECAP was conducted by using the same conditions of computational simulation. The validation of model was performed by comparison of average grain size values with those obtained experimentally by means of image analysis applied on micrographs that were acquired by means of optical microscopy (OM). Hardness and peak load values also indicated the occurrence of a partial dynamic recrystallization and recovery.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Congress-Wide Symposium on Additive Manufacturing

2017;():V002T02A021. doi:10.1115/IMECE2017-70346.

With approximately 12% of adults in the United States affected by osteoarthritis (OA), constant research is being performed to advance treatment techniques for this ailment. 3D printed bio-polymer caps have been proposed as a potential treatment for severe cases of OA, and are an alternative to traditional implants. This report considers the feasibility of one such bio-polymer cap using a simplified, linear, finite element analysis (FEA) model. Material properties for both Bionate 80A and articular cartilage are considered for comparison. The simulation modeled joint loading for a 195 lb, 867.4 N, adult male squatting from 0 to 90-degrees flexion with a mathematical model governing the changing contact area on the medial and lateral condyles. Menisci effects were neglected as a part of the model reduction. For Bionate 80A, minimum and maximum stress values of 1.124 MPa and 3.555 MPa were obtained, with corresponding deflections of 126.8 μm and 316.8 μm. The articular cartilage model gave stress values of 1.102 MPa and 3.623 MPa, with deflections of 170.2 μm and 420.8 μm. A maximum shear stress value of 1.988 MPa was obtained in the Bionate 80A simulation. From these results, it was determined that the Bionate cap is comparable to articular cartilage and could be a viable replacement in the cases of advanced OA, but the Bionate cap may have limitations on joint flexibility due to the relatively small 1.65 factor of safety at 90-degree. The maximum shear stress value indicates it would be viable to use specific biocompatible cements as a method of fixture.

Commentary by Dr. Valentin Fuster
2017;():V002T02A022. doi:10.1115/IMECE2017-70591.

Selective laser sintering is an additive manufacturing technique that uses a high power laser to sinter or melt powder layer by layer to build 3D shapes. This paper focuses on creating a mathematical model of the crack width and surface roughness that occur during the selective laser sintering process. Response surface methodology is used to build and determine a mathematical model. Five variables at five levels are selected: forward step, side step, speed, platform temperature and layer depth. Based on response surface methodology, 32 experiments are used to determine the mathematical model of two selective laser sintering defects: crack width and surface roughness. Next, a genetic algorithm is used to determine the optimal solution to minimize crack width and surface roughness of the part. Results show that the five selected parameters have an effect on the target defects as confirmed by the resulting main effects plots, interaction plots, and contour plots. An optimal set of parameters is determined for future use.

Commentary by Dr. Valentin Fuster
2017;():V002T02A023. doi:10.1115/IMECE2017-70618.

Laser cladding is a surface modification technique that is being explored as an additive manufacturing solution for metal. The laser cladding process is associated with nonuniform material strength within the clad and the heat-affected-zone. In addition, residual stress development increases the crack driving forces and reduces the fatigue life of the part. In the present work, a 3D transient fully coupled thermal-metallurgical-mechanical numerical model was built to simulate the coaxial powder injection laser cladding process for P420 stainless steel powder on an AISI 1018 steel plate for 50% +/− 10% bead overlap conditions. This work is an extension of prior physical and virtual simulation analyses. The model was employed to explore the effect of depositing directions and overlapping configurations on the temperature field evolution, thermal cycling characteristics, mechanical properties, and induced distortions in the clad and substrate. The model was validated by Vickers microhardness measurements and heat-affected-zone geometry from the specimens’ cross-sectioning. The simulation results show good agreement with experimental measurements with a 14% maximum error. It was found that the 50% bead overlap configuration with a raster fill deposition pattern had the most consistent hardness results, and minimal distortion. The presented simulation methodology can be used to predict the mechanical and physical properties of laser cladded components and to provide relevant information for process planning decisions.

Commentary by Dr. Valentin Fuster
2017;():V002T02A024. doi:10.1115/IMECE2017-70886.

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral and octet lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. Five different octahedral structures and seven different octet structures with relative densities ranging from approximately 0.07 to 0.35 were fabricated by changing the strut diameter. The minimum diameter of the strut elements is 0.50 mm and 0.35 mm for the octahedral and octet structures, respectively. The different relative density structures were tested in compression in the as-fabricated state and after they were UV cured. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, and plastic strain hardening to a peak in strength, followed by a drop in flow stress. It was found that the stiffness and strength of octahedral lattice structures is greater than the stiffness and strength of octet lattice structures at all relative densities for both as printed/fabricated and UV cured parts, and the ratio of stiffness and strength of UV cured parts to as fabricated parts decreases as the relative density increases. However, the ratio of stiffness and strength of UV cured parts to as fabricated parts for octet lattice structures in general is greater than that for octahedral structures. This can be attributed to the relative diameter of the struts and the depth of UV curing.

Commentary by Dr. Valentin Fuster
2017;():V002T02A025. doi:10.1115/IMECE2017-71392.

Metal power-based additive manufacturing (PAM) processes typically result in microstructures with a texture and columnar grains of different grain sizes, which affect the mechanical properties of the material. In this work, a method is developed to better represent the local granular stress fields within the microstructure. This is accomplished by converting a digital image segmentation from a synthetic microstructure into a shape-preserving finite element model with a microstructure-informed constitutive model that describes the mechanical behavior of solidified material produced by PAM. The new method to develop the finite element model allows the local stress intensification to be better captured in the vicinity of the grain boundary and helps with the prediction of defects and void formation in the material.

Commentary by Dr. Valentin Fuster
2017;():V002T02A026. doi:10.1115/IMECE2017-71685.

A number of additive manufacturing processes were analyzed and compared in regards to the direct 3D printing of copper induction coils. The purpose of this study was to narrow in on 3D printing technologies that would best be suited for the manufacture of copper inductions coils. The main focus of the study was to look at how all the available additive processes could specifically be successful at creating parts made of copper pure enough to effectively conduct electricity and also geometries complex enough to meet the demands of various induction coil designs. The results of this study led to three main categories of additive manufacturing that were deemed good choices for producing copper induction coils, these included: powder bed fusion, sheet lamination, and directed energy deposition. Specific processes identified within these categories were powder bed fusion using electron beam melting and laser melting; ultrasonic additive manufacturing; and directed energy deposition utilizing laser melting and electron beam melting using both wire and powder material delivery systems. Also discussed was additional benefits that using 3D printing technology could provide beyond the physical manufacturing portion by opening doors for coupling with computer aided drafting (CAD) and computer aided engineering (CAE) software in order to create a seamless design-to-production process.

Commentary by Dr. Valentin Fuster
2017;():V002T02A027. doi:10.1115/IMECE2017-71687.

To develop realistic process planning simulation tools and build strategies, an understanding of realistic transient conditions needs to be explored for multiple overlapping beads and 3D build ups. In the past, most of the research has focused on optimization strategies for a process configuration, typically for a single-track bead in steady state conditions. Changes in the bead geometry are inherent when depositing material; consequently, understanding dynamic, time varying heating and solidification conditions for multiple bead scenarios needs to be investigated. It is important to understand the system characteristics and its influence on the all the bead geometry parameters (not just the width) and the resultant hardness. Initially, a set of physical laser cladding experiments have been performed for single and multiple bead scenarios using 420 stainless steel powder being deposited onto mild steel plate with step variations being applied for the process power. For this research, complementary simulation models are developed, and the effects of the transient conditions on the bead hardness for several scenarios are investigated for four process power input step-functions using an imposed thermal cycling simulation approach. It is observed that the hardness values change from higher to lower values between the first and third beads, and for all scenarios, the hardness converges to a uniform value. When comparing geometry and hardness results, it can be seen that the geometry has more oscillations than the hardness. More research in this area is essential to develop robust real-time control solutions that encompass functional requirements such as hardness as well as the bead geometry.

Commentary by Dr. Valentin Fuster
2017;():V002T02A028. doi:10.1115/IMECE2017-71817.

In this report, we present a 3D printed insole which has multiple soft pressure sensors inserted in it to detect the force on the sole including heel, midfoot, and forefoot as well as timing and location of the strike while walking. The insole was 3D printed using a soft and flexible material having multiple open channels on it to attach sensors. Flexible and stretchable piezoresistive sensors were fabricated via screen printing and molding processes. The multi-layer sensor comprises an ionic liquid (IL) based piezoresistive layer sandwiched between two multi-walled carbon nanotube (MWCNT) based stretchable electrodes and finally, top and bottom insulation layers. The sensor was constructed using 3D printable photopolymer as 3D printing is our target manufacturing technique to build the entire structure including insole. The sensor embedded insole was evaluated for different foot landing conditions such as heel strike, midfoot strike, and forefoot strike. Experimental results showed that the developed insole could indicate the amount of force on insole when foot hits ground, with timing and location of the strike.

Commentary by Dr. Valentin Fuster
2017;():V002T02A029. doi:10.1115/IMECE2017-71957.

The development of flexible, viscoelastic materials for consumer 3D printers has provided the opportunity for a wide range of devices with damping behavior such as tuned vibration isolators to be innovatively developed and inexpensively manufactured. However, there is currently little information available about the dynamic behavior of these 3D printed materials necessary for modeling of dynamic behavior prior to print. In order to fully utilize these promising materials, a deeper understanding of the material properties, and the subsequent dynamic behavior is critical.

This study evaluates the use of three different types of models: transient response, frequency response and hysteretic response to predict the dynamic behavior of viscoelastic 3D printed materials based on static and dynamic material properties. Models of viscoelastic materials are presented and verified experimentally using two 3D printable materials and two traditional viscoelastic materials. The experimental response of each of the materials shows agreement with the modeled behavior, and underscores the need for improved characterization of the dynamic properties of viscoelastic 3D printable materials.

Commentary by Dr. Valentin Fuster
2017;():V002T02A030. doi:10.1115/IMECE2017-72007.

Electroactive polymers (EAP) have shown promise in producing significant and controllable linear displacement in slim and lightweight packages. EAPs allow for seamless integration and multi-functionality since they are actuated by a driving voltage that could be controlled by a microprocessor. Polyacrylamide (PAAM)/Polyacrylic acid (PAA) hydrogel EAPs are commonly chosen due to their low driving voltage, significant amount of displacement, and rapid manufacturing capabilities, as these gels can be 3D printed. To effectively extrude these gels in 3D printers, their viscosity, gelation time, shear thinning, and self-wettability must be characterized. In this research, ungelled solutions of PAAM are prepared and then strain-tested at temperatures from 60C to 80C and with 1–2 drops of TEMED catalyst to determine the gelation time that is optimal for 3D printing. Strain testing of ungelled PAAM solutions is also used to determine the shear thinning propertie of the gel. All strain testing is conducted using a rheometer with 25 mm diameter plates and an oven enclosure. A prototype extrusion system is designed and fabricated to be used for self-wettability testing of the gel. The process data will then be used in the design of a modified 3D printer to manufacture and test different configurations of these hydrogel actuators.

Commentary by Dr. Valentin Fuster
2017;():V002T02A031. doi:10.1115/IMECE2017-72041.

Additively manufactured polymers can be reinforced with high-performance reinforcements such as carbon fibers. Printed thermoplastics with embedded continuous carbon fibers are up to two orders of magnitude stronger and stiffer than high-grade 3D printed polymers. In this work, the mechanical response of such 3D printed carbon fiber specimens is evaluated. While the precursor carbon fiber reinforced filaments achieve a stiffness of 50GPa and strength 700MPa, mechanical properties of their printed parts are highly affected by printed carbon fiber curvatures. In this work, the structure of 3D printed parts was examined, and some design rules for 3D printing with continuous carbon fibers are suggested. Moreover, failure mechanisms in these samples are discussed and correlated to the micro-structure of the composites and the carbon fiber configuration.

Commentary by Dr. Valentin Fuster
2017;():V002T02A032. doi:10.1115/IMECE2017-72077.

Material jetting is an additive manufacturing technique that allows to produce three-dimensional solid parts without tooling and with minimum material wastage. In this context, magnetically loaded polymer composites with oriented magnetic particles are promising for many electrical and electronic applications. In this study, permanent magnet based alignment configurations were evaluated and compared in terms of different magnetic flux density using the finite element method. The particle alignment in cured droplet specimens and the stability of magnetically loaded polymer droplets deposited on a substrate were characterized for a material jetting based additive manufacturing process. Particle alignment and droplet deformation under the influence of the magnetic field was captured using real-time optical microscopy. The influence of rheological additives in controlling droplet stability in the magnetic field and mitigating particle settling were studied through experiments. The primary goal of this research was to identify parameters that facilitate high particle alignment, and material combinations that enhance droplet stability and mitigate particle settling. This fundamental research serves to enhance the understanding of processes and material behaviour for material jetting based additive manufacturing.

Commentary by Dr. Valentin Fuster
2017;():V002T02A033. doi:10.1115/IMECE2017-72224.

Selective Laser Melting (SLM) process is a Powder Bed Fusion (PBF) technique, which has shown significantly growth in the recent years. The demand for this process is justified by the versatility and ease in manufacturing the parts from 3D models as well for the increased complexity of engineered parts generated from topology or shape optimization. Automotive, aerospace, medical and aviation industries are taking great advantage of this process due the unique geometry characteristics found in the components. To enhance the benefits of SLM, a vital task is to analyze the laser power input impact on the temperature distribution through the powder bed, important for posterior residual stresses analysis. The Finite Element Method proposed in this study is a transient thermal model, able to predict temperature distribution through different sections of the powder bed when performing a single track of the laser scanning. Furthermore, the impact of the laser power input is carried out utilizing SS 304L, a low cost Stainless Steel alloy that can be employed in the SLM process, in order to determine the influence on the temperature distribution along the different cross sections.

Commentary by Dr. Valentin Fuster
2017;():V002T02A034. doi:10.1115/IMECE2017-72226.

The prediction of the mechanical properties of AM parts is very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. A limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches such as the Finite Element Method (FEM); nevertheless, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication.

In this paper the analysis and numerical simulation of the mechanical performance of FDM samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and PLA material. These samples were measured and modelled in a CAD system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally the experimental and numerical results were compared and conclusions drawn.

Commentary by Dr. Valentin Fuster
2017;():V002T02A035. doi:10.1115/IMECE2017-72232.

3D printing manufacturing technology has been utilized in various applications due to its promising manufacturing advantages. Desktop Digital Light Processing (DLP) printers provide high-resolution products with a moderate price range. DLP uses an array of micromirrors to transmit UV light from the light projector in order to perform selective curing of a prepolymer resin and turn it in to the required geometry. The CAD file is transformed into several slices according to the layer thickness. Each slice is then converted to an image of black and white pixels, in which each white pixel actuates a corresponding micromirror to transmit the UV light to cure a corresponding voxel, while a black pixel corresponds to no actuation, which means no curing for the corresponding voxel. The micromirror’s size determines the resolution of the printer. Although a theoretical voxel size can be determined as a function of the micromirror’s dimensions and layer thickness, the actual voxel volume depends on several parameters such as the layer thickness, UV exposure time, and UV exposure intensity. Controlling these three parameters would result in more accurate 3D printed parts and more control over the dimensional tolerance. In this paper, the effect of variable light intensity in terms of grayscale pixels is studied along with the exposure time and layer thickness to manipulate the voxel horizontal dimensions. This enables printing with voxel dimensions below the size of the micromirrors in the DLP, which improve the geometric dimensioning and tolerance of the printed parts.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Innovative Product Design

2017;():V002T02A036. doi:10.1115/IMECE2017-70123.

Ford Otosan’s Yeniköy plant, which assembles the Transit Courier and Tourneo Courier, has developed a innovative air leakage test method. Air leakage is not a directly measurable metric by customer, but it can be observed in some different ways such as wind noise, road noise, water ingress, dust intrusion, door closing efforts, and better cooling/heating performance. In order to detect leak point by conventional method is dramatically time consuming, needed to remove trim parts and issues under 11/s could not be detectable. Innovative air leakage test method has been designed by using air heater unit, air leak test device and thermal camera. By the assistance of thermal imaging method air leak rate has been improved.

Topics: Automobiles , Leakage
Commentary by Dr. Valentin Fuster
2017;():V002T02A037. doi:10.1115/IMECE2017-70436.

The crankshaft is a key part moving in the internal combustion engine. It converts the reciprocating piston movement into rotary motion. It is exposed to different forces resulted from the pistons pressures, friction, bending stresses and others. The paper concentrates on protecting the crankshaft journals from the direct impact of the piston pressure and other forces. It presents a familiar new modular product design. From this concept, work has done on the additional of the so-called ‘load bearing’ (two halves of a highly finished surfaces sleeve) embedded within the crankshaft journal. The proposed load bearing isolates the crankshaft journal and takes the place in the contact with other rotary components. This is an experimental research because of the presence of an extensive variety of models and uses of crankshafts. A prototype of the new solution was made and implemented on a single piston four stroke internal combustion engine and put in operation for 250 hrs. A precise examination and analyses of parameters in contrast with conventional crankshaft was done for verification and validation.

Commentary by Dr. Valentin Fuster
2017;():V002T02A038. doi:10.1115/IMECE2017-71464.

Lean Production is considered a management methodology that has been implemented in many industries and services. Nevertheless, Lean experts know that this is not only a management methodology; it is more a philosophy and a new way of life. This is the reason why it is difficult to implement but, even worst, to be successful and to be sustainable. A continuous effort of improvement must always be kept in mind. Attending to these factors, it is important to have a methodology that helps to implement Lean Production effectively. This methodology could be different from industry to industry in order to model the differences between them and, most important, to assure its sustainability.

This paper presents the validation of one such methodology for the Textile and Clothing Industry (TCI), based on three case studies (three Textile and Clothing companies located in North of Portugal). To validate it, different field procedures instruments such as interviews, questionnaires, and checklists were used. With these instruments, some validation results of the methodology were obtained, mainly, related with the diagnosis phase of Lean implementation. Results of two case studies were published in previous papers, being the results of a third case presented in this paper. Also, an analysis and discussion of the three case studies results, regarding their attitudes and difficulties are presented.

Topics: Textiles
Commentary by Dr. Valentin Fuster
2017;():V002T02A039. doi:10.1115/IMECE2017-71574.

In this paper, authors explore the analysis and development of a innovative coupling system for industrial vehicles. After an introduction of the topic and the objectives, the advantages for developing such a system are described in detail. Some previously published studies with similar content or conclusions necessary to the understanding of the system under study are also presented.

In order to develop a system more precise than the currently used, the common systems are study in this paper, focusing on four wheeled trailers, varying the coupling system’s rotation center, which can be on the front or rear vehicles. In the commonly used systems the trailers tend to get too close from the rotation center, this means that both trailers have lower trajectory paths and not ideal precision.

Having studied the systems currently used in shop floor, a new coupling system is developed, with the aim of increasing trailers’ trajectory precision and manoeuver options. Two different systems were under study. The first one is to control the trailers steering mechanism, in order to position the trailer in a more precise position. The other system is simply altering the coupling system length and rotation centers. By analyzing both results, the solution with the rotation of the rear axle in each trailer guarantees better precision, where the trailers perform a trajectory precision of 100%. However, the solution that better fits the industrial reality is the solution with the alteration of the length and the rotation center of the coupling system. This solution allows less precision but its better in price, cost and implementation effort.

Commentary by Dr. Valentin Fuster
2017;():V002T02A040. doi:10.1115/IMECE2017-71644.

All sealing technologies present inconveniences to be solved. One of the most significant adverse effects in the sealing production lines is the amount of material waste that is genetated due to the difficulties of achieving the correct thermal phase change in the polymer film during the sealing process. Sealing methods such as Induction, ultrasonic or heated jaw have similar operating characteristics, minimum gradients in pressure and temperature that are nedeed to create an efficient polymer transition, to produce the correct molecular arrangements and to avoid zones with little or null interaction between melted surfaces. This review shows the factors that affect the performance of jaw-multilayer polymer films that produce bad seal integrity; through understanding the design parameters to generate a small pressure and temperature gradients also characterizing and testing this phenomenon, the result of the review will help to identify theoretical basis and opportunities to design an innovate heated jaw sealing system with a uniform pressure and temperature along the sealing area.

Commentary by Dr. Valentin Fuster
2017;():V002T02A041. doi:10.1115/IMECE2017-71983.

Emerging technologies are providing a wide range of benefits for people in their different activities. That fact ranges from daily life activities, to business, teaching or simply for recreation. In what concerns to people with special needs there is a wide range of devices and applications that can be of use in addressing those needs and the will to progress in life. Observing in perspective, the support provided by technology can be seen as augmenting our sensorial experience by providing additional information as in the case of virtual reality and augmented reality. The devices provide additional information for what people sense, adding information and enlarging the sensorial experience while mounting additional information. This paper describes a strategy to extend, thru common use technology, the awareness of people with limited sensorial experience, aligning with other emergent technologies widely applicable to different situations while keeping a focus on teaching environments. That includes sensory devices like the Leap Motion device and 3D printed materials, which combined provide new opportunities for blind people to sense and retrieve new information.

Commentary by Dr. Valentin Fuster
2017;():V002T02A042. doi:10.1115/IMECE2017-72000.

Some of the biggest problems tackling Higher Education Institutions (HEI) are student’s drop-out and academic disengagement. Physical or psychological disabilities, social-economic or academic marginalization, and emotional and affective problems, are some of the factors that can lead to it.

This problematic is worsened by the shortage of educational resources that can bridge the communication gap between the faculty staff and the affective needs of these students.

In this paper, we present a framework capable of collecting analytic data, from an array of emotions, affects and behaviours, acquired either by human observations, like a teacher in a classroom or a psychologist, or by electronic sensors and automatic analysis software, such as eye tracking devices, emotion detection through automatic facial expression recognition software, among others.

This framework compiles the gathered data in an ontology, and will be able to extract patterns outliers via machine learning, enabling the profiling of the students in critical situations, such as disengagement, attention deficit, drop-out, and other sociological issues, setting real time alerts when these profiles are detected.

The goal is that, by providing insightful real time cognitive data and allowing the profiling of the student’s problems, a faster personalized response to help the student is enabled, allowing academic performance improvements.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Manufacturing Process Modeling and Optimization

2017;():V002T02A043. doi:10.1115/IMECE2017-70200.

In this paper, the modeling of a drill bit for the rotational burying steel pipe for a ground source heat exchanger is addressed. The objective of this study is to clarify the relationship of the bit design and bit penetration mechanism by model analysis and experiment. First, the detail of the rotary buried steel pipe pile used for the foundation pile of residential houses is explained. Then, the short heat exchanger well formed by foundation pile is explained. Moreover, the concept of the drill bit modeling for the rotational burying steel pipe pile is explained. The main feature of the modeling method is employing simple plane patches to approximate relatively complicated 3D curved surfaces which forms the 3D bit blade surfaces. Using this method of quasi-static modeling, the thrust force and starting torque of blade type, convex type and hybrid type bits can be computed for their penetration characteristics. Based on the modeling, the drill bit design procedure using a conventional general-purpose CAD system and the bit prototyping using a 3D printer are explained. The prototyping results of the designed bits are also precisely presented. Finally, the experimental results of the designed bits are presented. The relationship between the bit rotation, the penetration depth, and starting torque have been measured. The effect of the bit blade angle on the penetration is investigated and compared with the analysis using the developed bit modeling.

Commentary by Dr. Valentin Fuster
2017;():V002T02A044. doi:10.1115/IMECE2017-70341.

A vehicle’s exterior fit and finish, in general, is the first part to attract customers. For this reason, customers consider the J.D. Power report which classifies all vehicles based on different criteria. One of the criteria is the vehicle exterior fit and finish which is measured by two important factors called Flush and Gap. Automotive exterior engineers have been motivated in the past few years to increase their focus on optimizing the vehicle’s exterior panels split lines quality and minimizing variation in fit and finish to address customer and market quality standards.

Design engineers focus on controlling the deviation from nominal build objective and minimizing it. This study focuses on addressing the contributed factors that impact the quality of fit and finish. These critical factors resulted from the design process, product process and from the assembly process. An empirical analysis was used to minimize the fit and finish deviation.

Models that accurately describe the response values by experiments helped identify the most critical factors, and an analytical model and Response Surface Methodology (RSM) were used to optimize the acceptable values on these factors. Early results showed that some of these factors are critical for improving the quality of the fascia cutline fit and finish by obtaining more consistent gap and flush along the rear fascia cutline as well as reducing the offset issue.

The results of this study identified 17 critical factors which were split between controls and can be dialed to change the magnitude of the results and noises which have less effect on changing the results. Also, the 17 factors were separated into factors that affect Gap “α” or factors that affect flush “β” or both. Eight factors were selected based on production experience and based on their levels. Empirical analysis was conducted to generate regression models for both α & β. The selected factors were tested for their effect; also, the study took in consideration of different combined effect of these factors. Optimization with these factors were conducted for α & β. The results show that α can approach ±0.5 mm and β can approach ± 1 mm. The conclusion is that the consistency of α & β along the fascia to bodyside panel cutline (defined as ϴ) will be maximum when both α & β are minimum. The ultimate goal is to reach the stretched target which means zero mm gap and zero mm flush.

Topics: Finishes , Vehicles
Commentary by Dr. Valentin Fuster
2017;():V002T02A045. doi:10.1115/IMECE2017-70374.

The combined angular contact bearings are widely used in numerous rotating machinery system, but few research works on the combined angular contact ball bearings have been reported. To solve the problem about inconsistency fatigue life of the bearings in the combined bearings with asymmetric arrangement, this paper proposed a special combined bearings arrangement form in which the bearings with different contact angles are used simultaneously for the bearing combination. In order to validate the effectiveness of the proposed method, a mathematical model is proposed to analyze the load distribution, life and stiffness of the combined bearings, and the combined bearings with three different arrangements are comparatively calculated and analyzed. The results show that the whole life of combined bearings is mainly depend on the life of the bearing under heavy load, and the new arrangement form in which the initial contact angle of the bearing under heavy load is increased that can improve the whole life of combined bearings.

Topics: Ball bearings
Commentary by Dr. Valentin Fuster
2017;():V002T02A046. doi:10.1115/IMECE2017-70863.

Ball screw drives are widely used in machine tools to provide accurate linear motion. Elastic deformation is one of the major error sources for ball screw drives in achieving high accuracy motion, and changes greatly when velocity varies. The influence of velocity on the elastic deformation can be estimated and it can be compensated by means of dynamic modeling and servo control method. This paper presents a dynamic model considering torque transmission between the ball screw and the nut. And stiffness is identified by a method of combining theoretical calculation and experimental tests on a constructed test bench, which has two novel symmetrical loading mechanisms. In order to analyze the influence of moving velocity on the elastic deformation, simulation and experiments are conducted when two trajectories which have velocity jumps are input. And the simulated elastic deformations are compared with experimental results to evaluate the accuracy of the model. The results show that the simulated results fit the experimental results with high accuracy. The relationship between the elastic deformation of ball screw drives and the velocity is linear based on the experimental results. Then the simulation results are used to compensate the elastic deformation based on the feed-forward compensation method. The results show that the differences between the actual compensation values and actual elastic deformation are small and most of the elastic deformation of the ball screw drives can be compensated. Therefore, the proposed dynamic model and compensation method can be used to improve the tracking accuracy of ball screw drives.

Topics: Deformation , Screws
Commentary by Dr. Valentin Fuster
2017;():V002T02A047. doi:10.1115/IMECE2017-71336.

Manufacturing processes has seen constant change in the last decades to remain a central element of global wealth and development. Despite large efforts to increase efficiency, still significant sources of waste during manufacturing execution exist. These are mainly based on poor manufacturability, inefficient processes and low machine utilization.

The digital transformation towards “smart factories” will however enable development of new types of methods and technologies that will support advanced automation, resource efficiency and further improvements towards Lean Manufacturing processes.

This paper presents an approach for integrated evaluation of errors introduced from process planning to machined component. Critical parameters, influencing and interrelated factors, nominal value deviations from successive process steps and real-time machining are analyzed in one common cyber-physical model. This will in turn enable analyses of root-causes and serve as basis for process feedback, quality assurance and machine learning.

The focus in this paper is to describe the architecture of the Cyber Integrated Metrology, Learning and Evaluation System (CIMLES) approach and results from proof of concept demonstrators for 3- and 5-axis machining, developed in order to evaluate and verify various subsystems of the approach.

Topics: Metrology
Commentary by Dr. Valentin Fuster
2017;():V002T02A048. doi:10.1115/IMECE2017-71351.

Precision reducer is one of the key parts of an industrial robot, which generally incorporates cycloidal planetary drive. Engagement of the cycloidal wheel and the pins causes rolling friction between the wheel and the pins as well as sliding friction between the pins and the pin housing in the traditional cycloidal transmission of the reducer. In this paper, we present a new kind of design to make the pins and the pin housing a whole structure, thereby the cost of manufacturing and assembly can be significantly reduced. And in this new structure, we only need to consider sliding friction between the cycloidal wheel and the unibody of the pins and pin housing. The difference between the new structure and the conventional structure in the meshing properties was given. In addition, we used finite element method to analyze the friction and contact stress between the cycloidal wheel and the pins in the actual working condition, and compared it with the traditional structure. The simulation results proved the feasibility of the new structure and provided a theoretical basis for further design and manufacturing of this new kind of cycloidal planetary drive structure.

Commentary by Dr. Valentin Fuster
2017;():V002T02A049. doi:10.1115/IMECE2017-71556.

Inconel 718 is gaining its importance in the aerospace and power plant industries because of its high strength to weight ratio. The lack of understanding of the tool chip interface for Inconel 718 restricts the prediction of the apparent coefficient of friction and thus the cutting forces, thereby the machining efficiency. In the present study an analytical model has been developed accounting the actual variation of stresses over the rake face. The model focuses on the variation of shear stresses in the sticking region and has been considered to be increasing exponentially with distance from tool tip. The primary shear zone is assumed to be a thin layer with constant thickness and has been modelled using Johnson Cook material model. The shear stresses at the entry and exit of the primary shear zone has been calculated using iterative techniques proposed in the literature. The secondary shear zone has been analyzed dividing the contact length into two distinct regions and each region has been dealt separately. The ratio of real area of contact to the apparent area of contact has been given consideration and dealt with at macroscopic level. Experimental values have been extracted from previous studies on Inconel 718. The predictions of the analytical model was found to be in good agreement with experimental results. The experimental apparent coefficient of friction was obtained as 0.5119 against 0.4733 from the developed model at a velocity of 70 mm/min, depth of cut of 1mm, nose radius of 0.8mm and with negative rake angle (−6°) with CNMG0812 tool. The predicted and the experimental friction coefficient showed a variation of 7.07% – 10% and thus can serve as reliable model for Inconel 718.

Topics: Friction , Modeling
Commentary by Dr. Valentin Fuster
2017;():V002T02A050. doi:10.1115/IMECE2017-71717.

Virtual assembly systems have become popular in recent years due to its ability to simulate natural interaction between parts and ease of manipulation by the user. One of the most relevant technologies used in virtual assembly systems are haptic devices that provide force feedback and allow simulating real word conditions, such as weight, inertia, texture and collisions. Physics simulation engines (PSE) are another important tool used to simulate a realistic behavior in virtual assembly systems by enabling the effect of gravity and collision response of the virtual objects, resulting in a real world behavior. However, the use of haptic systems together with physics simulation engines is costly in terms of computing resources. This cost is mainly associated to collision detection between virtual objects, and increases when the shapes represented within the PSE are more complex, resulting in a poor performance of the virtual assembly system, making very difficult to simulate the assembly of complex parts or use several parts in the assembly. The present work shows a new algorithm to simulate complex objects, by using a different representation of the same object according with its dynamic state during the assembly process. The results show that the use of mixed model representation reduce the computing time when assembling objects, thus improving the performance of the virtual assembly system and finally allowing a better comfort and performance of the user during the assembly process. The system HAMS (Haptic Assembly and Manufacturing System) was used for the experimental validation, also the simulation of four assembly tasks that simulate real assembly objects, has been conducted.

Commentary by Dr. Valentin Fuster
2017;():V002T02A051. doi:10.1115/IMECE2017-71897.

Tacit knowledge is one of the main intangible assets in different corporations and an important issue is to explore new tacit knowledge elicitation techniques, being able to identify, categorize, represent, store and reuse this important knowledge type. This paper presents a new tacit knowledge technique called MAKMOSE (Manufacturing tAcit Knowledge MOtion Sequence Elicitation). The new knowledge elicitation technique explores the uses of motion sequence to explore the movements that workers and robots use when performing complex activities. This research provides a knowledge infrastructure representing a tacit knowledge super class to extract valuable experiences. This paper argues that the implementation of MAKMOSE requires exploration and connection of (a) a tacit knowledge infrastructure as a repository, (b) a tacit knowledge life cycle, and (c) implementing the right technology capturing valuable experiences through motion sequence. An important challenge is to demonstrate how new tacit knowledge types can be identified, categorized, stored and reused using motion sequences techniques. This paper presents some research ideas to implement the MAKMOSE in Complex Manufacturing Processes (CMP).

Topics: Manufacturing
Commentary by Dr. Valentin Fuster
2017;():V002T02A052. doi:10.1115/IMECE2017-72283.

In this article a GHG and energy analysis for the plastic injection process of an ABS medium sized injected part carried out in a hybrid injection molding machine is reported. A power consumption process pattern for an ABS medium-size part is defined as well as the energy usage of components, the energy used for the injection process is calculated for the injection cycle and for the process setup. The reported study includes a hybrid machine analysis working under an electric network that relies mainly on thermoelectric energy generation. The GHG emissions assessment was estimated using the 2015 emission factor applied for Mexico. The results provide new experimental data for ABS plastic injected parts in hybrid injection machines.

This paper describes the outcomes of a GHG emissions and energy assessment for an ABS medium-sized injected part carried out in a HIMM at UNAM. The approach followed by the authors in this assessment was aimed at providing information about the energy usage and GHG emissions for the process and the part.

The main contribution of this paper is the insight related to energy usage indicators in the process, the energy usage and the GHG emissions within components. The product used as a case study and the results of its GHG emissions and energy assessment are presented.

Commentary by Dr. Valentin Fuster
2017;():V002T02A053. doi:10.1115/IMECE2017-72293.

The exchange of data and information among collaborating partners and resources in a distributed manufacturing system assumes significance especially in today’s global economy. In recent years, Internet of Things (IoT) and Cyber Physical Systems (CPS) related practices and technologies have emerged as enablers of collaborative manufacturing and engineering practices. Smart technologies involving Virtual Reality and haptic based interactions are continuing to play an important role in concurrent engineering based methods in distributed contexts. The research presented in this paper explores the design of an IoT based framework for electronics manufacturing involving the use of VR based environments and Cloud computing technologies. The process domain of interest is electronics manufacturing with an emphasis on Surface Mount assembly of printed circuit boards (PCBs). The VR based assembly environment played a key role in this IoT framework as it supported Concurrent Engineering practices by enabling stakeholders in this manufacturing system context to obtain a better understanding of the manufacturing process design while providing ‘what if’ analysis capabilities for changing customer requirements. Another benefit of such VR based IoT frameworks is the potential of such 3D environments to provide effective training of assembly processes as well as facilitating better understanding of process design issues from distributed locations.

Commentary by Dr. Valentin Fuster
2017;():V002T02A054. doi:10.1115/IMECE2017-72558.

As a kind of promising process for mass material removal in rough and semi-rough machining of hard-to-machine materials, plunge milling receives wide concerns and is often considered as one of the most effective methods in metal cutting operation, especially in aircraft industry. The cutting force in plunge milling operation differs from that in side milling or end milling for the complex geometries. To clarify the force based cutting mechanisms, a systematic study on cutting force modeling is conducted in this paper based on the precise cutting geometry which considers both the real-time uncut chip thickness calculation and cutter runout. The deduced cutting force model can be used for different cutting conditions in plunge milling process. Then, series of plunge milling operations with various cutting steps are implemented to verify the proposed force model. The results indicate that the predicted values show quite good agreement with the measured cutting forces.

Topics: Cutting , Milling
Commentary by Dr. Valentin Fuster
2017;():V002T02A055. doi:10.1115/IMECE2017-72559.

In this research, friction stir processing of AZ31B magnesium alloy of 6 mm thickness was done in submerged conditions. The process parameters, i.e. tool pin profile (simple cylindrical, stepped cylindrical, stepped square), rotational speed ranging from 800 to 1200 rpm and traverse speed ranging from 0.5 to 1.5 mm/sec were optimized using the multi response optimization technique. The experiment was conducted with L27 orthogonal arrays. The Immersion test and hardness have been considered as output response. From the view of an application, it would be more significant to optimize the Immersion Corrosion rate and Hardness of Submerged Friction Stir Processed AZ31B alloy. Thus, this study aims at optimizing the process parameters, including various tool pin profiles, feed rates and rotational speeds with corrosion rate and micro hardness using TOPSIS. Using analysis of variance (ANOVA), the most significant parameter effect of the submerged friction stir processing was determined.

Commentary by Dr. Valentin Fuster
2017;():V002T02A056. doi:10.1115/IMECE2017-72636.

High-speed milling has often been applied in injection mold manufacturing processes, where surface roughness is a significant criterion in product quality demands. It is equally applicable to automotive or industrial engineering and to toy manufacturing, where plastic parts with a high-quality surface finish have been processed using the injection molding technique. High-speed milling involves a number of process parameters that may affect the 3D surface topography formation. Literature analysis reveals that dynamical behavior is a significant factor in the end milling process on surface roughness parameters. To improve the accuracy of predicted surface topography models, it is important to include the dynamical behavior of milling factor.

This paper describes the surface prediction model of combined end-milling geometrical and dynamical interaction models. The natural frequency of machine assembly and forced vibrations during the cutting process were measured during the flat-end milling process. Unevenly distributed cutting marks were revealed by surface 3D topography images and microscopy images of the machined samples.

A mathematical model to predict surface topography was developed, including dynamical behavior and cutting geometries. Machine accuracy also has to be addressed. 3D surface topography parameters from the experimental sample provided the results for the mathematical prediction model. This model offers a software tool for manufacturers to improve the quality of machined part surfaces, taking into account the behavioral properties of their machining equipment. Relevant conclusions about the manufacturing equipment accuracy have been drawn. Vibrations in the milling system affect the cutting process and contribute to the surface topography prediction model. Local cutting tool vibrations do not have any influence on surface parameter mean values.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Metal Forming: Novel and Hybrid Processes, Material Characterization, and Control

2017;():V002T02A057. doi:10.1115/IMECE2017-70087.

In fabrication of high strength materials coupled with improved mechanical properties; focus on integration of multifunctional reinforcements are increasing along with novel processing methods. Single layer 2-D material Graphene are among one such novel material with huge aspect ratio, posse’s high strength. But the real challenge is processing and incorporation of these reinforcements with appropriate content in metals or its alloys matrix. Current research work focus to study the anisotropic behavior on addition of pristine Graphene/MWCNT and processing methods like ball milling under constant ball to powder precursor ratio (BPR) of AA 2024 nanocomposites. The extent change in aspect ratio, size of the nanoparticle mixtures during ball milling were analyzed under SEM and Raman spectroscopy. Thus obtained (ball milled) precursors are consolidated through vacuum hot press and hot extruded to get typical flat specimen at optimized processing parameters. XRD analysis, relative density and hardness measurement is done on extruded composites. Thus developed composites are subjected to study the anisotropic behavior at various orientations and strain rates (0.5, 1.0, 1.5 mm/min) using uniaxial tensile testing instrument and corresponding stress strains graphs were obtained. The fracture surfaces were characterized by scanning electron microscope (SEM) and its shows the nucleation of the dimple size are varies with increasing the strain rate and also deeper dimple size were noticed. Negative strain sensitivity were observed for the lower strain rate (0.1 and 0.3 mm/min) and positive strain sensitivity for higher strain rates. Microstructural anisotropy infers that AA2024-Graphene/MWCNT composites are sensitive to strain rate and shear type of failure is observed on increasing the strain rate.

Commentary by Dr. Valentin Fuster
2017;():V002T02A058. doi:10.1115/IMECE2017-70104.

The objectives of this research work are to determine the influence of effect of spark electric discharge machine on the recast layer and indeed the strength properties of the AA 6061-Graphene composites. The green compacts were subjected to microwave sintering at 550 °C for 30 minutes. The sintered samples are then hot extruded at 300 °C to flat plates and air cooled later. The extruded samples are subjected to mechanical characterization for density, hardness and tensile strength. Further, spark EDM process is used to machine the extruded samples. The SEDM processed samples with the aluminium alloys 6061-Gr composites compared with the as extruded condition. The hardness studies on the samples are carried out using Rockwell hardness testing machine with B scale as per standards, Tensile strength studies are carried out in Instron Universal Testing Machine with a standard strain rate of 0.75 mm/min. Recast layer of the SEDM samples is studied using HR-SEM and the thickness of the recast layer is recorded. The influence of the recast layer thickness on the tensile strength the extruded composite is studied. The surface roughness and material removal rate (MRR) of the extruded composites after the SEDM process also studied in correlation with the strength properties.

Commentary by Dr. Valentin Fuster
2017;():V002T02A059. doi:10.1115/IMECE2017-70347.

Micro- and multiscale material properties must be considered when manufacturing miniature devices, especially when considering utilizing multiscale sheet metal hydroforming processes. One of the critical considerations during the design process is the burst pressure for the sheet metal which is a limiting factor for potential hydroforming operations. In order to simplify determining tearing or rupture conditions, it is sometimes desired to use analytical methods for estimating material properties, including burst pressures, which occur shortly after material instability. Many researchers have developed approximate methods for predicting deformation during open die hydroforming based upon analytical approaches for biaxial conditions for circular and elliptical dies. Additionally, extracting material properties of sheet metal under biaxial conditions such as bulge hydroforming more closely matches forming conditions that the sheet metal will undergo for actual parts. The objective of the current research was to evaluate the analytically developed models’ ability to predict burst conditions and compare those burst results to those obtained from finite element models and experimentation. Stainless steel (annealed 0.2-mm thick AISI 304) was hydroformed in a circular open die with diameter of 11mm. Elliptical dies were also evaluated that had minor diameters of 11mm and aspect ratios down to 0.5. It was found that using the analytical method developed specifically for circular dies was a good predictor for the burst pressure while the more general analytical method for elliptical dies did not agree with either results from finite element analysis or experimental results.

Topics: Pressure , Sheet metal
Commentary by Dr. Valentin Fuster
2017;():V002T02A060. doi:10.1115/IMECE2017-70482.

From centuries the metals and materials has been characterized using a traditional method called uniaxial tension test. The data acquired from this test found adequate for operations of simple forming where one axis stretching is dominant. Currently due to the demand of lightweight component production, multiple individual parts are eliminated by stamping in a single complex shape which further reduces many secondary operation. This need is driven by the requirement of 54 miles per gallon by 2025. Due to the complex part geometry, the forming method induces multi-axial stress states, which found difficult to predict using conventional tools. Thus to analyze these multi-axial stress states limiting dome height test and bulge test were recommended in many research. However, these tests limit the possibilities of applying multi-axial loading and resulting stress patterns due to contact surfaces. Thus a test machine called biaxial test is devised which would provide the capability to test the specimen in multi-axial stress states with varying load. In this paper, two processes, limiting dome test and biaxial test were modeled and compared. For this, the cruciform test specimens were used in biaxial test and conventional forming limit specimens for dome test. Variation of loadings were provided multi-axially in both test to capture the limit strain from uniaxial to equi-biaxial strain mode. In addition, the strain path, forming and formability was investigated and difference between the tests were provided.

Commentary by Dr. Valentin Fuster
2017;():V002T02A061. doi:10.1115/IMECE2017-70510.

As a core part of the aero engine casing, the thin-walled tube with large diameter usually formed by sheet hydroforming presents high forming precision and forming quality. In this paper, the appropriate hydraulic pressure and blank holder force should be identified to control the wall thickness uniformity of N08811 alloy tube with large diameter. Firstly, the stress-strain curve of this material at room temperature is obtained from deep drawing tests. Subsequently, within the allowable range of springback and wrinkling errors, finite element simulation and the uniform test design are performed to investigate the effect of the multi-level process parameters on the thickness uniformity of the higher D/t ratio tube. Results show that the blank holder force and the hydraulic pressure produce significant effects on the wall thickness uniformity. Finally, the regression analysis is further carried out for the computational results from uniform experimental design experiments. The optimized process parameters are then obtained and the wall thickness uniformity of the tube is improved. These results provide a theoretical reference for improving the forming quality of thin-walled tube with large diameter.

Commentary by Dr. Valentin Fuster
2017;():V002T02A062. doi:10.1115/IMECE2017-70549.

Exponential increase in the use of auto vehicles, and thus the fuel consumption, which relates to the air pollution, vehicle industry are in a strict environmental regulation from government. Due to which the innovation related to light-weighting is not only an option anymore but became a mandatory necessity to decrease the fuel consumption. To achieve this target, industry has been looking in fabricating components from high strength to ultra-high strength steels. With the usage of these material the lightweight was achieved by reducing a gage thickness. However due to their high strength property often challenges occurred are higher machine tonnage requirement, sudden fracture, geometric defect, etc. The geometric defect comes from elastic recovery of a material, which is also known as a springback. Springback is commonly known as a manufacturing defect due to the geometric error in the part, which would not be able to fit in the assembly without secondary operation or compensation in the forming process. Due to these many challenges, other research route involved is composite material, where light materials can be used with high strength material to reduce the overall vehicle weight. This generally includes, tailor welded blanks, multi-layer material, mechanical joining of dissimilar material, etc. Due to the substantial use of dissimilar materials, these parts are also called as hybrid components. It was noted that the part weight decreases with the use of hybrid components without compromising the integrity and safety. In this paper, a springback analysis was performed considering bilayer metal. For this two dissimilar materials aluminum and composite was considered as bonded material. This material was then bent in a channel forming set-up. The bilayer springback was compared in different condition like aluminum layer on punch side and then on die side. These results were then compared with the baseline springback of only aluminum thin and thick layer. It was found that the layer, which sees the punch side, matters due to the differences in elastic properties for both material and thus it directly influences the springback.

Commentary by Dr. Valentin Fuster
2017;():V002T02A063. doi:10.1115/IMECE2017-71069.

Incremental forming (IF) is a novel sheet material forming technique typically restricted to drafted geometries. By utilizing tooling which features regions that extend radial from the axis of the tool, it is proposed that this restriction can be eliminated. Additionally, by controlling the rotational motion of the tool, it is proposed that greater levels of detail can be achieved in the IF process. In the following works, the feasibility of utilizing this type of tooling in the IF process is discussed, as well as several variations of such tooling. Validation of the proposed tooling is also presented.

Commentary by Dr. Valentin Fuster
2017;():V002T02A064. doi:10.1115/IMECE2017-71199.

Machining induced residual stresses have an important effect on the surface integrity. Effects of various factors on the distribution of residual stress profiles induced by different machining processes have been investigated by many researchers. However, the initial residual, as one of the important factor that affect the residual stress profile, is always been ignored. In this paper, the residual stress field induced by the quenching process is simulated by the FEM software as the initial condition. Then the initial residual stress field is used to study the residual stress redistribution after the machining process. The influence of initial stress on the stress formation is carried out illustrating with the mechanical and thermal loads during machining processes. The effects of cutting speed on the distribution of residual stress profile are also discussed. These results are helpful to understand how initial residual stresses are redistributed during machining better. Furthermore, the results in the numerical study can be used to explain the machining distortion problem caused by residual stress in the further work.

Topics: Machining , Stress
Commentary by Dr. Valentin Fuster
2017;():V002T02A065. doi:10.1115/IMECE2017-71305.

In this study, Friction Stir Processing (FSP) technique was applied for the development of surface composites of 6082-T6 aluminum alloy reinforced with Titanium Carbide with the aim of investigating the possibility of enhancing the surface property of aluminium alloy by reinforcing it with Titanium Carbide to form metal matrix composites using one pass and three passes respectively. The groove with depth of 1.5 mm and width range from 0.5mm to 1.9mm were machined and filled with reinforcement powder using axial load of 20 kN. The rotational speed of the tools employed is 1000 rpm and the feed rate of 60 mm/min was used. The hardness properties to provide a sense of mechanical response and the surface morphology of the eroded samples were studied and characterised to reveal the microstructural features by using Scanning Electron Microscopy (SEM). Energy dispersive x-ray spectroscopy (EDS) was used to analyse the specimens. This study would motivate future studies to further explore the viability of composites produced using FSP technique.

Commentary by Dr. Valentin Fuster
2017;():V002T02A066. doi:10.1115/IMECE2017-71362.

The trend for lightweight construction, especially in the automotive industry, leads to increased use of corresponding lightweight materials. In addition to novel construction materials such as fiber-reinforced plastics, established materials such as steel or aluminum are continuously being further developed, which is usually accompanied by a distinct increase in their strength. Beside material-related lightweight construction, new designs are applied such as the profile design.

The disadvantage of this development is that established forming processes such as deep drawing, profile bending, hydroforming but also shearing of high-strength components increasingly reach their process limits. Particularly, in the case of trimming of high-strength components such as press-hardened components, it is hard to present conventional shearing processes in serial processes due to low tool life and deficient cutting surface quality. For this reason the laser cutting technology is often used. It is characterized by high flexibility and can largely meet the requirements regarding component quality. In contrast to shearing, however, it requires very long process cycle times due to its process rate, which makes it significantly less productive.

High speed impact cutting offers an alternative. By exploiting high speed effects in the material, which leads to adiabatic heating of the shearing zone and a related significant reduction in strength, even ultra-high strength steel materials with tensile strengths of above 1500 MPa can be cut at high quality and with a short cycle time. In order to transfer this technology to serial applications and to develop process limits, extensive investigations were carried out using high-strength sheet metal materials and tube materials. The results are presented in this paper.

Topics: Cutting
Commentary by Dr. Valentin Fuster
2017;():V002T02A067. doi:10.1115/IMECE2017-71506.

Sheet forming of tailor welded blanks (TWBs) of advanced high strength steels is complex because of the notable differences in mechanical properties, and hence in formability, of base metals, heat affected zones and weld seam. In this work, an accurate characterization of the mechanical behavior of these regions in TWBs made of a DP and TRIP steel was carried out. Micro-samples, machined from base metals and fusion zone were employed to retrieve the local constitutive laws up to fracture. At the same time, macro-samples, extracted throughout the welded joint were tested to assess the weldment overall behavior. Along with global load-displacement data, strain and displacement fields of the joint were evaluated, using a Digital Image Correlation technique. An FE simulation of the entire joint was setup, using the previously identified material properties. In a comparison between the FE model and experiments, good results were obtained both at a global and local level, up to fracture.

Commentary by Dr. Valentin Fuster
2017;():V002T02A068. doi:10.1115/IMECE2017-71722.

The failure mechanism in stretch bending over a small die radius for Advanced High Strength Steels (AHSS), commonly referred as “shear fracture”, has rendered the Forming Limit Diagrams (FLD) fail to predict it based on the initiation of a localized neck. As shown in previous studies using a Stretch-Forming Simulator (SFS) and Bending Under Tension (BUT) test, shear fracture depends not only on the radius-to-thickness (R/T) ratio but also on the tension/stretch level applied to the sheet during bending. Although the stress-base empirical fracture limit criterion was developed for various AHSS grades, the fracture limit was not well implemented in the computer simulations to predict stretch bending fracture.

In this paper, the new developed experimental analysis is conducted on the modified bending under tension test to further investigate the stretch bending fracture mechanism under the production die condition. Various AHSS grades including DP590, DP780, DP980 and DP1180 are included in the study. Based on numerous experimental results, the maximum shear stress at failure, the thinning strain and strain gradient across the die radius are obtained for all test materials. Results demonstrate that the presence of the large strain gradient is the cause for fracture in stretch bending AHSS over a small die radius. The maximum shear stress at failure and the limit thinning strain on the die radius in the stretch bending condition are determined and used as the new fracture criteria, which can be easily implemented in the computer simulations.

Topics: Failure
Commentary by Dr. Valentin Fuster
2017;():V002T02A069. doi:10.1115/IMECE2017-72044.

Laser Beam Forming (LBF) being a novel technique and non-contact manufacturing process, employs laser beam as the tool of shaping and bending metal sheets into different shapes and curvatures for various applications. LBF is a high-temperature process, where rapid heating and cooling occurs causing microstructural changes like dynamic recrystallization and phase changes. The study becomes necessary to ensure that the structural integrity of the processed material is not compromised. Hence, the investigation focuses on the effect of temperature on the developed microstructure during the LBF process. The design of experiment was considered, using three levels and five factors. The experimentally measured curvatures were validated with the predicted measured curvatures, which were found to be in agreement. The result shows that the developed ferrite and pearlite grains were due to the heating and cooling. Furthermore, the average grain sizes at a low energy density of about 355°C and high energy density of about 747°C were found to be about 10 μm and 6 μm respectively. It is implied that the high temperature from the high laser energy aided the deformation of the grains significantly. However, such high temperature must be closely monitored so to avoid metallurgical notches in the processed component.

Commentary by Dr. Valentin Fuster
2017;():V002T02A070. doi:10.1115/IMECE2017-72088.

This paper presents the results of a research project obtained using theoretical, numerical and experimental methods, in order to solve the problems encountered when increasing the height of a double deep drawing sink, and the proposed solution. The analysis considers: Manufacturer limitations (eg. tool modifications, steel material changes etc.), the process parameters observed and measured during the deep drawing operation of the failure part, the theoretical fundamentals of sheet metal forming and the analysis and simulation with a computer program based in the finite element method (FEM). The analysis and simulation results using a FEM program showed that, it is possible the height increment of the sink, utilizing a variable blankholder force, to an 11% above from the fabricated parts before the application of the proposed solution but 5% less than the required final product height.

Commentary by Dr. Valentin Fuster
2017;():V002T02A071. doi:10.1115/IMECE2017-72478.

This work emphasizes on the geometric and dimensional accuracy of cylindrical tailor welded blank (TWB) components manufactured under warm forming conditions. In this work, TWB sheet material made of austenitic stainless steel (ASS 304 Grade) and deep drawing steel (IS 513 grade) materials were TIG welded before subjecting to stamping operation. Numerical simulations were validated with experimental results. Simulation results were analyzed to check the thickness variation and stress distribution within the component which otherwise would be difficult to measure experimentally. Measurements in terms of geometric accuracy gave encouraging results. The roundness and perpendicularity measurements indicated better accuracy whereas, cylindricity value has slightly improved. However, dimensional accuracy of the parts in terms of thinning, cup height and diameter has deteriorated. It was found that the spring back effect played a significant role in the deterioration of dimensional accuracy. Presence of residual stresses might be the cause for this effect; further studies are needed to address this issue.

Topics: Blanks
Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Nanomanufacturing

2017;():V002T02A072. doi:10.1115/IMECE2017-71022.

Properties of phosphorene are intensively researched by many research groups since it was discovered in 2014. This new 2D material has a direct band-gap, depending on the number of layers (0.3 eV for bulk to 2.0 eV for monolayer) similar to MoS2. In this paper, we report layer-by-layer (LbL) deposition method to deposit a few layers of phosphorene film on the substrate, and successfully fabricate phosphorene field effect transistor (FET) with LbL black phosphorus (BP) film. By using the FET characteristics of the device, we fabricate biosensors with Poly-L-lysine (PLL) linker molecules and Alpha-fetoprotein (AFP) antibody to detect different concentration of AFP antigen (0.1 ppb to 1 ppm). The results indicate that BP can be a promising material for biosensing applications.

Commentary by Dr. Valentin Fuster
2017;():V002T02A073. doi:10.1115/IMECE2017-71738.

This paper introduces the use of capillary thermodynamics as a powerful nanomanufacturing tool, and its specific application to infiltrate sulfur into 3-D nanostructured electrodes for advanced lithium-sulfur and/or sodium-sulfur battery development. The capillary effect specifically targets nucleation from the equilibrium vapor pressure of bulk sulfur (gas phase) onto nanoscale surfaces (liquid phase). This leads to condensates that nucleate and grow uniformly over the surface leading to self-limited and conformal composite materials moderated by the chemical potential driving force between the nanoscale nuclei and the bulk sulfur. Our studies show highly consistent and repeatable sulfur loading exceeding 80 wt.% sulfur, fast kinetics that can lead to full infiltration in ∼ 10 minutes, and synergy with pre-formed carbon materials including carbon nanotube arrays, carbon nanotube foams and sponges, and microporous carbons with pore sizes ∼ 0.5 nm. This overcomes challenges of scaling to high areal capacity in lithium-sulfur and sodium-sulfur batteries, and our results emphasize the highest reported areal capacities for solid-processed cathodes to date (> 19 mAh/cm2). This paves the route to batteries with energy density > 500 Wh/kg with reliable manufacturing processes that simultaneously sustain low cost and high throughput.

Commentary by Dr. Valentin Fuster
2017;():V002T02A074. doi:10.1115/IMECE2017-71952.

Carbon nanofibers in polymer-based composites reduce the electrical resistivity of the composite but can be up to 100 times more expensive than the bulk polymer. This work uses acoustic focusing to organize and compact carbon nanofibers in a mineral oil mixture. The result is a decrease in the composite electrical resistivity without an increase in the global volume fraction of the fibers in the composite and associated material cost.

The composite consisted of Pyrograf PR-19-LHT carbon nanofibers mixed in light mineral oil at 1.6% volume fraction carbon nanofibers. The mixture was contained in a 1 cm × 1 cm × 4 cm glass cuvette. A PZT-4 piezoelectric transducer, epoxied to the external face of one of the sidewalls, generated the acoustic radiation forces in the container. A 1.179 MHz sinusoidal signal powered the transducer, producing a standing wave with 27 nodes and 13 antinodes in the container. A digital multimeter performed the 2-wire resistance measurement before, during and after focusing.

Settling of the filler due to gravity resulted in an initial drop in the electrical resistance. Once the mixture reached steady state, toggling the signal power off and on also toggled the approximate electrical resistance between the 19.2 MOhms and 11.5 MOhms respectively. This work also presents a simple volume fraction model, which predicted that the focused resistance would be 34% of the unfocused value. In the experiment, acoustic focusing reduced the electrical resistance to 60% of the resistance in the unfocused mixture, demonstrating acoustic focusing as a method for reducing electrical conductivity within a composite.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Robotics and Automation

2017;():V002T02A075. doi:10.1115/IMECE2017-70404.

The ability to be programmed for a wide range of tasks is what differentiates robots from dedicated automation. Consequently, robots can be faced with often-changing requirements and conditions. Conventional application development based on teach programming takes robots out of production and occupies personnel, limiting robots’ effectiveness in these environments. Off-line programming solves these problems, but robot inaccuracy must be compensated by a combination of calibration, compliance, and sensing. This complicates up-front systems engineering and application development, but results in systems that can operate in a wider range of requirements and conditions. Performance can be optimized if application tolerances and process uncertainties are known. If they often change, optimization must be done dynamically. Automating this optimization is a goal of smart manufacturing. With its trend of increasing connectivity between the components of robotic systems both within workcells and to the enterprise, exchanging this information has become more important. This includes tolerance information from design through process planning to production and inspection, and measurement uncertainty from sensors into operations. Standards such as ISO 10303 (STEP), the Quality Information Framework (QIF), the Robot Operating System (ROS), and MT-Connect support this exchange to varying degrees. Examples include the assignment of assembly tasks based on part tolerances and robot capabilities; the automated generation of robot paths with tolerances arising from sensed obstacles; and the optimization of part placement to minimize the effects of position uncertainty. This paper examines requirements for exchanging tolerance and uncertainty in robotics applications, identifies how these requirements are being met by existing standards, and suggests improvements to enable more automated information exchange.

Topics: Robotics , Uncertainty
Commentary by Dr. Valentin Fuster
2017;():V002T02A076. doi:10.1115/IMECE2017-70465.

In order to paint large workpieces, heavy painting manipulators are always transported by mobile platforms due to their limited workspaces. To reduce the vibration of the end-effector, the base velocity of the manipulator is constant when painting. In this operation mode, the Starting Base Position (SBP) of the manipulator is important to attain the maximum manipulability and dexterity. This paper aims to optimize the SBP for painting a specified surface efficiently. An approximated decouplable model of painting manipulators is first built to get the analytically expressed inverse kinematic solutions. Then joint-level criteria for one manipulating point reflecting the manipulability and dexterity are proposed, followed by the combined criterion for a painting task about SBP with consideration of the platform velocity. Afterwards, the SBP optimization problem is translated into a least squares problem. To solve such a problem, an initial SBP value is first calculated through an algorithm based on internal penalty function method. Then a modified Levenberg-Marquardt method is employed to get the optimal SBP. Results of applications on painting a straight and an arc path indicate that the method proposed is effective and efficient.

Commentary by Dr. Valentin Fuster
2017;():V002T02A077. doi:10.1115/IMECE2017-70712.

Velocity stability is one of the most important properties for a parallel tool head during machining process. However, due to the nonlinear kinematic transmission characteristics between the motion in joint space and the motion in task space of a parallel manipulator, there exists obvious rotational velocity fluctuation problem of a parallel tool head which couples two degrees of freedom and one translational degree of freedom (2R1T), and the kinematic performance would be heavily affected by the rotational velocity fluctuation problem. Thus, it is a core issue of how to ensure velocity stability of this type parallel tool heads under general numerical control (NC) system. In this paper, by taking a typical 2R1T parallel tool head as an object of study, a method for solving the rotational velocity fluctuation problem is investigated. First, the nonlinear kinematic characteristics of the 2R1T parallel tool head are analyzed to explain the reason of the rotational velocity fluctuation. Next, a completed optimization method of feed rate is proposed to reduce the rotational velocity fluctuation, and the different displacement increments and velocity mapping abilities of each driving shaft are considered. Finally, a comparison experiment is carried out to validate the effectiveness of the method. The result shows that the rotational velocity fluctuation of the 3-DOF parallel tool head is almost eliminated by setting appropriate feed rate.

Commentary by Dr. Valentin Fuster
2017;():V002T02A078. doi:10.1115/IMECE2017-71118.

Product Lifecycle Management (PLM) Tools have been used extensively in different companies in recent years. These tools enable the development of components, products or assemblies in a digital way through their lifecycle. The entire lifecycle presents different challenges implementing digital tools and this paper explores relevant features between part design and manufacturing at mechatronics systems in the aerospace industry. New Product Introduction (NPI) process is a challenging task. In some cases, it is required not only the use of sophisticated robotics applications, but also in the integration of different instruments and controls in order to meet the accuracy and repeatability requirements. Complex scenarios need to be validated at early NPI stages at aerospace industry at not only part design, but also exploring the manufacturability of complex mechatronics processes demonstrating low cost production. Digital manufacturing tools in PLM are able to evaluate these complex scenarios through virtual prototyping to support the next generation of mechatronics systems in the aerospace industry. This paper argues that the understanding of virtual prototyping using digital PLM tools is an important issue for NExt GenerAtion MechAtronics SYstems (NEGAMASY) to support Aerospace Industry.

Commentary by Dr. Valentin Fuster
2017;():V002T02A079. doi:10.1115/IMECE2017-71670.

Due to their flexibility, low cost and large working volume, 6-axis articulated industrial robots are being used increasingly for drilling, trimming and machining operations. However, producing high quality components has proven to be difficult, as a result of the inherent problems of robots, including low structural stiffness, hence excitation of structural modes, low positional accuracy, and bandwidth limitations associated with dynamics and control. These limit robotic machining to non-critical components and parts with low accuracy and surface finish requirements. As a part of the “Light Controlled Factory” project at the University of Bath, studies have been carried out to improve robotic machine capability, specifically positioning accuracy and vibration reduction. This paper describes experimental studies in reducing robot machining vibrations induced by cutting forces with active vibration control, using accelerometers to measure vibration and inertial actuators to mitigate vibration forces. With a relatively simple controller, a 25% reduction of RMS vibration amplitude is demonstrated.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Second Symposium on Fastening and Joining Research and Advanced Technology

2017;():V002T02A080. doi:10.1115/IMECE2017-70127.

In this study, the Fickian diffusion formulation is extended to the adhesive layer of a single lap joint model, in order to develop a coupled peel and shear stress-diffusion model. Constitutive equation are formulated for shear and peel stresses in terms of adhesive material properties that are time and location-dependent. Numerical solution is provided for the effect of diffusion on shear and peel stresses distribution. Detailed discussion of the results is presented.

Commentary by Dr. Valentin Fuster
2017;():V002T02A081. doi:10.1115/IMECE2017-70503.

In designing a bolted joint consisting of dissimilar hollow cylinders, the load factor (the ratio of an increment in axial bolt force to an external tensile load) is important. In the present paper, the effect of the load application point, the ratio b/a of the outside diameter to the inside diameter of dissimilar hollow cylinders, Young’s modulus ratio between the dissimilar hollow cylinders on the load factor and the interface stress distribution are examined using FEM calculations. As a result, it is found that the values of the load factor decrease as the ratio b/a increases and the positions where the load application point approaches the interfaces while the value of the load factor is independent of the bolt preload. In addition, it is found that the value of the load factor is less than 0.1 for steel and steel hollow cylinder joints, it is less than 0.2 for aluminum and aluminum hollow cylinder joints and it is less than 0.15 for aluminum and steel hollow cylinder joints while the material of bolt is steel in the present study. For verification of the FEM calculations, experiments to measure the load factor and a load when the interfaces start to separate were carried out. The FEM results are in a fairly good agreement with the experimental results. Finally, based on the obtained results, a design method for bolted joints with dissimilar hollow cylinders is demonstrated for determining the nominal bolt diameter and the bolt strength grade.

Commentary by Dr. Valentin Fuster
2017;():V002T02A082. doi:10.1115/IMECE2017-70515.

The objective of the paper is to examine bolt loosening behavior in a bolted joint under transverse loading both experimentally and numerically. Bolt loosening tests were carried out using Junker’s type loosening machine. In the Junker’s loosening tests, repeated transverse displacements (displacement range S = ±0.35mm were applied to a bolted joint with a M10 hexagon bolt and nut, and then a reduction in the axial bolt force was measured. In the FEM calculations, bolt loosening behavior was examined for a model of Junker’s type loosening machine. In addition, the effects of the flatness and the surface roughness at the bearing surfaces in a clamped part on the reduction in the axial bolt force were examined in the FEM calculations. As a results, it was found that the nut rotation occurred when a glider plate moved toward to the center of the joint from the right and the left dead points. In addition, bolt loosening mechanism was elucidated using the change in the contact stress distribution at the engaged screw threads. The reduction in axial bolt force was found to be the largest for the first 1 cycle loading and then it decreased gradually as the loading cycles increased. An amount of the reduction in the axial bolt force was predicted in the FEM calculation taking account of the flatness (inclined of clamped part) and the surface roughness (contact surface ratio) in 10 loading cycles. The contact surface ratio (surface roughness) was found to significantly affect the reduction in axial bolt force. The predicted results were in a fairly good agreement with the experimental results. Furthermore, the effects of the grip length and the nominal bolt diameter were examined on the bolt loosening behavior experimentally.

Topics: Stress , Bolted joints
Commentary by Dr. Valentin Fuster
2017;():V002T02A083. doi:10.1115/IMECE2017-71074.

In this paper, development of a finite element model for simulating welding-induced thermal stresses is discussed. This nonlinear FE model employs sequentially coupled three-dimensional thermo-mechanical formulation. A solid three dimensional 20 node brick elements have been used in ABAQUS, a linearly elastic and linearly plastic approach is implemented in the analysis. The effects of key process parameters, viz., power, size and speed of welding has been discussed. Further, the need for interfacial elements, instead of solid mesh elements to simulate molten weld solidification, has been investigated. Model validation with published literature has been employed to determine the appropriate properties for the interfacial element (shear and normal). Due to the nature of the welding process, heat generation from moving heat source, rapid heating and cooling gives rise to high stresses in the weld. These stresses have been observed to be greatly influenced by the process variables as well the properties of the selected interfacial element. Position, orientation and magnitude of the highest residual stress components are discussed.

Commentary by Dr. Valentin Fuster
2017;():V002T02A084. doi:10.1115/IMECE2017-71079.

In this paper a finite element model is presented which describes the effects of fillet weld geometry on the thermal stresses. In a separate research, development of a finite element model for simulating welding-induced thermal stresses is discussed. This nonlinear FE model employs fully coupled three-dimensional thermo-mechanical formulation, including interfacial element to simulate the weaker solidified molten weld pool. Due to the nature of the welding process, heat generation from moving heat source, rapid heating and cooling gives rise to high stresses in the weld. This research investigates the effect of weld shape & size, weld gap, (l/d ratio) depth of weld to size ratio on the generated thermal stresses. The size of the round and flat stocks has been varied to investigate their effects of the stresses as well as to determine the thick-to-thin geometry limits based on acceptable design limits of thermal stresses.

Commentary by Dr. Valentin Fuster
2017;():V002T02A085. doi:10.1115/IMECE2017-71223.

Adhesive bonding of composite structures has been widely applied in aviation, aerospace, automotive and other industry fields due to the advantages of no holes required, no stress concentration, relative light weight, corrosion resistance and capability of connecting dissimilar materials. However, the strength of joining is greatly influenced by the properties of adhesives and surface treatment of adherents, the geometry and dimension of joints, loading and environmental factors, as well as the curing process and so on. When the finite element (FE) method is used to investigate the influence of above factors on structural response and to optimize the joining design, parametric modeling is required to avoid huge repetitive preprocess work at each evaluation. In this paper, the three-dimensional parametric FE models of Single Lap Joint (SLJ) between carbon fiber-reinforced polymer (CFRP) and steel was established and updated based on the published test data. Using the verified parametric model, the influence of adhesive layer thickness and relative stiffness on the joining strength is investigated, and the results provide a theoretical basis for the design of adhesion joints between CFRP and steel.

Commentary by Dr. Valentin Fuster
2017;():V002T02A086. doi:10.1115/IMECE2017-71248.

As compared to normal Friction Stir Welding (FSW) joints, the Underwater Friction Stir Welding (UFSW) has been reported to be obtainable in consideration of enhancement in mechanical properties. A 5052-Aluminum Alloy welded joints using UFSW method with plate thickness of 6 mm were investigated, in turn to interpret the fundamental justification for enhancement in mechanical properties of material through UFSW. Differences in microstructural features and mechanical properties of the joints were examined and discussed in detail. The results indicate that underwater FSW has reported lower hardness value in the HAZ and higher hardness value in the intermediate of stir zone (SZ). The average hardness value of underwater FSW increases about 53% greater than its base material (BM), while 21% greater than the normal FSW. The maximum micro-hardness value was three times greater than its base material (BM), and the mechanical properties of underwater FSW joint is increased compared to the normal FSW joint. Besides, the evaluated void-area fraction division in the SZ of underwater FSW joint was reduced and about one-third of the base material (BM). The approximately estimated average size of the voids in SZ of underwater FSW also was reduced to as low as 0.00073 mm2, when compared to normal FSW and BM with approximately estimated average voids size of 0.0024 mm2 and 0.0039 mm2, simultaneously.

Commentary by Dr. Valentin Fuster
2017;():V002T02A087. doi:10.1115/IMECE2017-71302.

AISI 304 stainless steel is one of the grades of steel widely used in engineering applications particularly in chemical equipments, food processing, pressure vessels and paper industry. Friction crush welding (FCW) is type of friction welding, where there is a relative motion between the tool and work-piece. In FCW process, the edges of the work-piece to be joined are prepared with flanged edges and then placed against each other. A non-consumable friction disc tool will transverse with a constant feed rate along the edges of the work-piece, which leads to welding. The joint is formed by the action of crushing a certain amount of additional flanged material into the gap formed by the contacting material. The novelty of present work is that FCW removes the limitations of friction stir welding and Steel work pieces can be economically welded by FCW. Taguchi method of Design of Experiments (DOE) is used to find optimal process parameters of Friction Crush Welding (FCW). A L9 Orthogonal Array, Signal to Noise ratio (S/N) and Analysis of Variance are applied to analyze the effect of welding parameters (welding speed, RPM, tool profile) on the weld properties like bond strength. Grain refinement takes place in friction crush welding as is seen in friction stir welding. Friction crush welding process also has added advantage in reducing distortion and residual stresses.

Commentary by Dr. Valentin Fuster
2017;():V002T02A088. doi:10.1115/IMECE2017-71411.

Friction Stir Welding (FSW) is a solid-state joining process invented by The Welding Institute (TWI, United Kingdom) in 1991 in partnership with the National Aeronautics Space Agency. The process is emerging as one of the preferred alternative methods to permanently join materials that are difficult to join with traditional fusion methods (e.g., MIG, TIG, etc.). The welding of various copper alloys to various aluminum alloys is of great interest to the nuclear industry and the electrical distribution industry. The very different melting points of these two alloys preclude traditional fusion welding. Since the pin tool is simultaneously rotating and traversing through the work piece, flow around the tool is asymmetrical. This has led to designating one side of the tool as advancing and the opposite side as retreating. On the advancing side of the weld, the tool has a tangential velocity in the same direction as the weld is being created. The retreating side of the weld tool is the opposite. It can be can expected that asymmetric heating and deformation will occur in the weld due to this advancing/retreating nature of the FSW pin tool. Although previous studies have been performed that have observed this asymmetric behavior in both similar and dissimilar materials, the resulting welds have been of a poor quality. Large statistical experiments were conducted locally to study the effects of tool geometry, process parameters, and material composition have upon the friction stir butt welding of aluminum alloy 6061-T6 to copper alloy 11000 using a modern conventional 3-axis CNC vertical mill. The research seeks to determine (1) which direction a dissimilar metal friction stir weld between aluminum and copper should be executed, (2) the optimal shoulder diameter to be used when friction stir welding aluminum and copper on a CNC mill, and (3) the addition of a third material to act as an aide. The extensive statistical interactions between these parameters is also documented. A weld schedule was developed that resulted in an ultimate tensile strength (UTS) surpassing (greater than 90% of the weaker, more ductile copper alloy UTS strength) what has been documented in the current literature despite the machine limitations of the CNC vertical mill. Proper optimization of the welding schedule developed may approach 100 percent of the basic copper 11000 properties across the welded zone into the aluminum 6061-T6 alloy.

Commentary by Dr. Valentin Fuster
2017;():V002T02A089. doi:10.1115/IMECE2017-71668.

The 7050-T7451 aluminum alloy has been widely used in the aerospace industry. Due to its chemical composition, this alloy has high levels of mechanical properties that allow the production of low-weight aircraft structural components. However, these alloys are thermally treatable and are not able to bear manufacturing processes involving heat. Because of the importance of their applications, studies based on the development of solid state welding process would be desirable aiming to find an alternative to generate welded joints for this kind of components. In this work, an investigation concerning the behavior of the 7050-T7451 aluminum alloy during Friction Stir Welding (FSW) was carried out. The profile of longitudinal residual stresses of plates welded by the FSW process was obtained using the ultrasonic method through critically refracted longitudinal waves (LCR). Two different frequencies were employed, 3.5 MHz and 5 MHz. The measurements were performed in the longitudinal direction of the welded joint at different distances from the center line of the weld. The magnitude and distribution of residual stresses found with this method are consistent with literature review, reaching 150MPa on the center of the weld.

Commentary by Dr. Valentin Fuster
2017;():V002T02A090. doi:10.1115/IMECE2017-72569.

This paper deals with the investigations on dissimilar weld between two duplex stainless steel grades AISI 2205 and AISI 2507. Increasing use of duplex stainless steel grades instead of austenitic stainless steel grades are growing day by day. This study is an effort in this direction in particularly focusing the dissimilar welding of super duplex stainless steel (AISI 2507) and commercial duplex stainless steel (AISI 2205) grades. Gas tungsten arc welding process was used in this study to fabricate the defect free weld plate. Microstructural analysis on dissimilar weld was carried out to study the diffusion of alloying elements. Micro hardness analysis, Charpy impact toughness test, tensile test and formability test were carried out and the properties were compared with their corresponding base metal properties. Hot corrosion test was carried out to study the feasibility of dissimilar weld in severe corrosive applications. The findings of this paper try to fulfill the applications where commercial duplex stainless steel grades are frequently gets affected in the weld region due to the severity of corrosive environments and due to the sacrificing weld properties.

Topics: Stainless steel
Commentary by Dr. Valentin Fuster
2017;():V002T02A091. doi:10.1115/IMECE2017-72581.

Resistance Spot Welding (RSW) is one of the most common and dominant technologies utilized in the automotive industry to join the thin sheet metals together, and expulsion is a common phenomenon during the operation. How to ensure the high quality nugget formation and joining performance is essential to ensure the quality and integrity of structures. In this study, solid state resistance spot welding is introduced in order to prevent expulsion. The effect of welding current and welding time on the mechanical performance of the solid state RSW in terms of nugget size, tensile performance and nugget formation will be investigated experimentally by using steel sheet metals. Microstructure and micro-hardness of the nugget cross-section will be evaluated as well.

Topics: Welding
Commentary by Dr. Valentin Fuster
2017;():V002T02A092. doi:10.1115/IMECE2017-72691.

A validated Von-Mises stress-based model is presented for multi-axial fatigue evaluation of clamped sheet metal joints that are subjected to a cyclic bending stress additional to the compressive bearing stress in the bolted joint. Joint material, bolt preload level, and the amplitude level of the cyclic bending moment are studied for their effect on the fatigue life of the clamped sheet metal plate. Bolt tightening to a precise preload level is accomplished by using an ultrasonic instrument that has been mechanically pre-calibrated to convert the time delay of longitudinal ultrasonic wave reflection to a bolt elongation and corresponding preload value. Fatigue data is generated using an MTS fatigue testing system. Experimental and FEA results are fitted into a multi-axial model for predicting the fatigue behavior of the bolted joint. Discussion and data analysis are provided.

Commentary by Dr. Valentin Fuster
2017;():V002T02A093. doi:10.1115/IMECE2017-72692.

This study investigates the effect of the rate of autoclave heating and cooling on the performance of bonded lightweight material single lap joints (SLJ) after they have been heat cycled at high relative humidity. Two different temperature ramp rates are used for the autoclave bonding of test joints. Joint performance is assessed in terms of the load transfer capacity (LTC) and the corresponding failure mode in a tensile-shear test. Three different combinations of Aluminium and Magnesium adherends are used in test samples using aliphatic polyether (polyurethane) film adhesive. The effect of heating rate on the peel strength of cured adhesive is also investigated. Data analysis and discussion are provided.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Sensing, Measurement, and Process Control

2017;():V002T02A094. doi:10.1115/IMECE2017-70058.

This paper focuses on the prediction of the Remaining Useful Life (RUL) of a carbide insert end mill. As tool life degradation due to wear is the main limitation to machining productivity and part quality, prediction and periodic assessment of the condition of the tool is very helpful for the machining industry. The RUL prediction of tools is demonstrated based on the force sensor signal values using the Support Vector Regression (SVR) method and Neural Network (NN) techniques. End milling tests were performed on a stainless steel workpiece at constant machining parameters and the cutting force signal data was collected using force dynamometer for feature extraction and further analysis. Both the SVR and NN models were compared based on the same set of experimental data for the prediction performance. Results have shown a good agreement between the predicted and actual RUL of the tools for both models. The difference in the level of the prognostic matrices such as accuracy, precision and prediction horizon for both models was discussed.

Commentary by Dr. Valentin Fuster
2017;():V002T02A095. doi:10.1115/IMECE2017-70301.

When spindle rotates, the stiffness and natural frequency that reflect the dynamic performances of spindle system, vary with different rotating conditions. Therefore, the measurement of stiffness and natural frequency is highly needed. However, it is difficult to apply excitation to the rotating spindle during the measurement. In this paper, a non-contact electromagnetic loading device is developed to provide desirable excitation for the measurement. Next, an experimental spindle test rig with constant pressure preload is established. With the help of the proposed loading device, stiffness and natural frequency of the experimental spindle at different rotating states are measured. Finally, the effects of rotation speed and temperature on the natural frequency and stiffness of spindle are discussed based on the measurement results. The results show that the rotation speed and temperature have the similar influence trend on the experimental spindle’s softening.

Commentary by Dr. Valentin Fuster
2017;():V002T02A096. doi:10.1115/IMECE2017-70914.

Scanning beam interference lithography (SBIL) technology is applied to produce large-area grating with nanoscale phase accuracy. One of the greatest challenges of SBIL is locking interference fringe to a moving substrate with nanometer spatial phase error, which requires measuring the fringe phase with subnanometer precision. We are developing a novel homodyne phase-locking interferometer (HPLI) to meet the harsh measurement requirements. The HPLI offers high precision phase measurements as well as the direction recognition of the interference fringe drift with a four-orthogonal detection system. However, nonlinearity error impacts the phase measurement accuracy of HPLI with nanometer scale, which is mainly due to polarization mixing. In this paper, we present a method to estimate and compensate nonlinearity error in real time by applying an extended Kalman filter algorithm. The simulation results show that the method can effectively eliminate the nonlinearity error.

Commentary by Dr. Valentin Fuster
2017;():V002T02A097. doi:10.1115/IMECE2017-71295.

The main purpose of this initial paper is to demonstrate the application of order statistics in the estimation of form error from a CMM measurement. Nowadays, modern industry sets high standards for geometrical precision, surface texture and material properties. There are many parameters that can characterize mechanical part, out of which flatness error plays important in the assembly process and performance. Recently, due to the greater availability and price reduction, Coordinate Measurement Techniques have increased their popularity in the industry for on-line and off-line measurements as they allow automated measurements at relatively low uncertainty level. Data obtained from CMM measurements have to be processed and analyzed in order to evaluate component compliance with the required technical specification. The article presents an analysis of a minimal sample selection for the evaluation of flatness error by means of coordinate measurement. In the paper, a statistical approach was presented, assuming that, in the repetitive manufacturing process, the distribution of deviations between surface points and the reference plane is stable. Based on the known, statistical distribution, order statistics theorem was implemented to determine maximal and minimal point deviation statistics, as it played a dominant role in flatness error estimation. A brief analysis of normally distributed deviations was described in the paper. Moreover, the case study was presented for the set of the machined parts which were components of a machine tool mechanical structure. Empirical distributions were derived and minimal sample sizes were estimated for the given confidence levels using the proposed theorem. The estimation errors of flatness values for the derived sample sizes were analyzed and discussed in the paper.

Commentary by Dr. Valentin Fuster
2017;():V002T02A098. doi:10.1115/IMECE2017-71609.

Anisotropy of surface texture can in many practical cases significantly affect the interaction between the surface and phenomena that influence or are influenced by the topography. Tribological contacts in sheet forming, wetting behavior or dental wear are good examples. This article introduces and exemplifies a method for quantification and visualization of anisotropy using the newly developed 3D multi-scale curvature tensor analysis. Examples of a milled steel surface, which exhibited an evident anisotropy, and a ruby contact probe surface, which was the example of isotropic surface, were measured by the confocal microscope. They were presented in the paper to support the proposed approach. In the method, the curvature tensor T is calculated using three proximate unit vectors normal to the surface. The multi-scale effect is achieved by changing the size of the sampling interval for the estimation of the normals. Normals are estimated from regular meshes by applying a covariance matrix method. Estimation of curvature tensor allows determination of two directions around which surface bends the most and the least (principal directions) and the bending radii (principal curvatures). The direction of the normal plane, where the curvature took its maximum, could be plotted for each analyzed region and scale. In addition, 2D and 3D distribution graphs could be provided to visualize anisotropic or isotropic characteristics. This helps to determine the dominant texture direction or directions for each scale. In contrast to commonly used surface isotropy/anisotropy determination techniques such as Fourier transform or autocorrelation, the presented method provides the analysis in 3D and for every region at each scale. Thus, different aspects of the studied surfaces could clearly be seen at different scales.

Commentary by Dr. Valentin Fuster

Advanced Manufacturing: Variation Simulation and Design for Assembly

2017;():V002T02A099. doi:10.1115/IMECE2017-70118.

To improve product quality, tolerance analysis represents nowadays a key element in industry. It aims to verify whether allocated tolerances satisfy functional and assembly requirements. Tolerance analysis approaches are generally proposed considering idealized surfaces (such as planes, cylinders, spheres, etc.) and the shape of the components is parameterized to take into account the geometric deviations. However, this approach considers only ideal substitute models, which may strongly differ from the actual geometry of the manufactured components. To enable high-precision products, there is a strong need to integrate parts form defects in the assembly modeling. Form defects are firstly generated by modal decomposition: a basis of modes of deviation is predefined and each mode is associated with a randomly generated weight to account the variability in the geometry of the components. The form defects are subsequently taken into account when handling with constraints in assembly with gaps. Assembly simulation is defined by a mathematical optimization problem, which includes the definition of the signed distance between points of the surfaces undergoing form defects and potentially in contact. The contact configuration is assessed by determining the relative positioning of parts in the assembly. An application example demonstrates the relevance of the procedure; it considers two surfaces classes: planes and cylinders. The assembly probability and functional probability are computed when mechanism is rigid and which is firstly without form defects and then with form defects. The paper closes with a comparison between the reference methods and the proposed procedure.

Commentary by Dr. Valentin Fuster
2017;():V002T02A100. doi:10.1115/IMECE2017-70387.

The high-speed trains are currently considered one of the most significant technological breakthroughs in passenger transportation for providing lower time-consuming and higher quality improvement services. Nevertheless, the manufacturing quality of high speed train is related to driving safety and riding comfort. It needs to be emphasized that the control of dimensional variation plays a crucial and irreplaceable role in today’s manufacturing processing which affect the quality of manufacturing. In this study, a variation simulation method considering both tolerance analysis with rigid assumption and welding distortion is developed to predict dimensional variation of the side wall of high-speed train during the assembly process. Firstly, the tolerance analysis with rigid assumption method is employed to simulate the dimensional variation when the parts of side wall are assembled together. Then, the finite element method (FEM) based on inherent strain is used to predict welding distortion including longitudinal shrinkage, transverse shrinkage and angular distortion. Finally, the results combining both tolerance analysis with rigid assumption and welding distortion are compared with actually measured results to identify the effectiveness of this method.

Topics: Welding , Simulation , Trains
Commentary by Dr. Valentin Fuster
2017;():V002T02A101. doi:10.1115/IMECE2017-70398.

Geometrical variation is a problem in all complex, assembled products. Recently, the Digital Twin concept was launched as a tool for improving geometrical quality and reduce costs by using real time control and optimization of products and production systems. The Digital Twin for geometry assurance is created together with the product and the production systems in early design phases. When full production starts, the purpose of the Digital Twin turns towards optimization of the geometrical quality by small changes in the assembly process.

To reach its full potential, the Digital Twin concept is depending on high quality input data. In line with Internet of Things and Big Data, the problem is rather to extract appropriate data than to find data. In this paper, an inspection strategy serving the Digital Twin is given. Necessary input data describing form and shape of individual parts, and how this data should be collected, stored and utilized is described.

Topics: Inspection , Geometry
Commentary by Dr. Valentin Fuster
2017;():V002T02A102. doi:10.1115/IMECE2017-70550.

Although mass production parts look the same, every manufactured part is unique, at least on a closer inspection. The reason for this is that every manufactured part is inevitable subjected to different scattering influencing factors and variation in the manufacturing process, such as varying temperatures or tool wear. All these factors inevitably lead to parts, which deviate from their ideal shape. Products, which are built from these deviation-afflicted parts consequently show deviations from their ideal properties. To ensure that every single product nevertheless meets its technical requirements, it is necessary to specify the permitted deviations. Furthermore it is necessary to estimate the consequences of the permitted deviations, which is done via tolerance analysis. During this process the imperfect parts are assembled virtually and the effects of the geometric deviations can be calculated during a variation simulation.

Since the tolerance analysis is to enable engineers to identify weak points in an early design stage it is important to know which contribution every single tolerance has on a certain quality-relevant characteristic, to restrict or increase the correct tolerances. In this paper two different approaches are shown and compared to represent the statistical behavior and the strongly connected sensitivity analyses. In particular a newly developed approach, which is based on fuzzy arithmetic, is compared to the established EFAST-method. The exemplary application of both methods and the comparison of the results are illustrated on a case study.

Commentary by Dr. Valentin Fuster
2017;():V002T02A103. doi:10.1115/IMECE2017-70630.

Process control in 3D printing (also known formally as Additive Manufacturing - AM) has largely been absent even in production systems. Simultaneously, computer vision has become more accessible with open source libraries (e.g. OpenCV, used successfully for traversing the state of California in an autonomous vehicle to win a DARPA Grand Challenge). 3D printing is particularly well suited to be enhanced by computer vision as fabrication is layer wise and predictable assuming correct operation. Big Area Additive Manufacturing (BAAM) — operating at significantly larger scales than traditional 3D printing — stands to benefit given the higher throughput of material (hundreds of pounds per hour) and the associated high costs of errant fabrication. Furthermore, minimum feature sizes in BAAM, such as individual layers, are sufficiently large to be analyzed with standard photography. With computer vision, sophisticated algorithms can be applied to identify problems early in the process that are not normally manifest until after process completion. Subtle and latent defects can be remediated before the onset of permanent damage or at a minimum the process can be aborted to avoid significant material loss. Fourier analysis can provide a useful perspective of the spatial periodicity of the layers of exposed surfaces during fabrication and this spectral information can inform the process of surface roughness, delamination, and deposition consistency in a data efficient manner. The large layer thickness of BAAM allow for Fourier analysis to be performed with standard photography. This paper explores the implementation and advantages of a low cost computer vision system that leverages OpenCV libraries operating on a Raspberry Pi Linux computer with simple yet high resolution photography — driven by the hypothesis that quality and yield of open source BAAM hardware can be dramatically enhanced.

Commentary by Dr. Valentin Fuster
2017;():V002T02A104. doi:10.1115/IMECE2017-70877.

Locating schemes, used to position parts during manufacturing, are usually designed in such a way that the response from the system is minimized. This implies that the position of the fasteners and/or welds are known in an assembly. Today there exist numerous of methods aiming to find an optimal set of locating points to increase the stability of an assembly, for both rigid and compliant parts. However, various industrial applications use surface-to-surface contacts to constrain certain degrees of freedom. This can lead to designs sensitive to geometric and load variations. As the complexity of the surfaces increases, difficulties of allocating geometric tolerances arise. An approach to control this is to keep the contact locations statistically stable. In this paper a methodology is presented where the First-Order Reliability Method (FORM) is applied for numerical data, retrieved through Finite Element Analysis (FEA), to ensure that statistically stable contact location are achieved for two bodies with surface-to-suface contact. The FEA data represents how much of the total stress that lies within a given area, σΩ. The data is continuous and therefore it is assumed that the gradient can be calculated numerically with small steps. The objective function is to maximize σΩ for n variables. The data set is simulated through Finite Element Analysis using the commercial software Ansys and the results is illustrated on a case study from the machining industry.

Commentary by Dr. Valentin Fuster
2017;():V002T02A105. doi:10.1115/IMECE2017-70899.

This paper addresses some important theoretical issues for constrained least-squares fitting of planes and parallel planes to a set of input points. In particular, it addresses the convexity of the objective function and the combinatorial characterizations of the optimality conditions. These problems arise in establishing planar datums and systems of planar datums in digital manufacturing. It is shown that even when the input points are in general position: (1) a primary planar datum can contact 1, 2, or 3 input points, (2) a secondary planar datum can contact 1 or 2 input points, and (3) two parallel planes can each contact 1, 2, or 3 input points, but there are some constraints to these combinatorial counts. In addition, it is shown that the objective functions are convex over the domains of interest. The optimality conditions and convexity of objective functions proved in this paper will enable one to verify whether a given solution is a feasible solution, and to design efficient algorithms to find the global optimum solution.

Topics: Fittings
Commentary by Dr. Valentin Fuster
2017;():V002T02A106. doi:10.1115/IMECE2017-71130.

The suspension spring compression introduce local deformation in the suspension shock tower, and it brings the imprecision or uncertainty of the computer aided tolerancing (CAT) results of the suspension assembly. This work presents an integrated tolerancing and motion error analysis method of suspension assembly to consider the local deformation in the suspension shock tower. Tolerancing model of the suspension assembly is constructed in CAT software. FEA model provides the local deformation in the suspension shock tower introduced by the suspension spring compression under full loaded condition. The local deformation is represented with the modified probability distribution function (PDF) of the joining point between the suspension and the suspension shock tower. The modified PDFs of the joining points, together with the manufacturing deviations of the suspension parts are input to the constructed tolerancing model. The results are obtained that the final assembly variations of the suspension assembly under empty and full loaded conditions. Based on the tolerancing results, motion errors of the suspension from empty condition to full loaded condition are analyzed with the ADAMS model of the suspension. The results have shown that tolerancing and motion error analysis results considering the local deformation in suspension shock tower are more accurate than the initial normal distribution. The tolerancing and motion error analysis work presented in the paper will enhance the understanding of the suspension assembling, and help systematically improving the precision control efficiency in automobile industry.

Commentary by Dr. Valentin Fuster
2017;():V002T02A107. doi:10.1115/IMECE2017-71215.

Geometric variation produces gaps or interferences between the mating features of parts when assembling them. To accomplish the operation, forces need to be applied to deform the parts; while as a price, stresses arise around the structure and accumulate as the assembly process proceeds, which could impair the structural reliability. A tool modeling and analyzing the accumulation of assembly stresses can help us predict and control it. Associated with geometric variation, the levels of assembly stresses are variables as well, thus variation analysis of them is required rather than a single case analysis; however, research on assembly variation analysis has focused mainly on the geometric variation itself. In a previous study, we developed a compliant assembly variation analysis method which is based on a Finite Element (FE) model condensation technique of substructuring (Lin J, et al. “Compliant assembly variation analysis of aeronautical panels using unified substructures with consideration of identical parts.” Computer-Aided Design, 2014.). In this paper, by introducing Output Transformation Matrices (OTMs) into the unified substructure system, we add the analysis of assembly stresses onto that of assembly deviations: no extra modeling work is needed, but the assembly stresses within a part are recovered from its assembly deviations by OTMs. Though these OTMs need to be generated in advance, this one-off effort will be relatively small when the assembly process to be analyzed involves multiple steps. A case study on an aeronautical panel assembly is presented to illustrate the proposed method and investigate the characteristics of assembly stresses.

Topics: Manufacturing , Stress
Commentary by Dr. Valentin Fuster
2017;():V002T02A108. doi:10.1115/IMECE2017-71218.

Volatile markets, tough customer expectations, and short product life cycles are just some of the challenges the automotive industry has to deal with. In this context, important quality features are expressed as key product characteristics (KPC). The process of defining and reviewing such KPCs concerns each department of an automobile company.

This paper presents a method for an intersubjective problem understanding of inter-divisional working groups and a common product KPC’s definition. The scientific contribution lies in the field of quality assessment for the premium-segment automotive industry, while the novelty can be found in providing the opportunity to take quality decisions based on variation simulations and on high-end-visualizations. The proposed method aims to realize and implement a higher premium quality standard and, at the same time, to reduce the number of physical prototypes, to shorten development times and to facilitate an intersubjective problem understanding. In relation to the developed method, an industrial application and its results are presented.

Topics: Visualization
Commentary by Dr. Valentin Fuster
2017;():V002T02A109. doi:10.1115/IMECE2017-71310.

The mass production paradigm strives for uniformity, and for assembly operations to be identical for each individual product. To accommodate geometric variation between individual parts in such a process, tolerances are introduced into the design. However, for certain assembly operations this method can yield suboptimal quality. For instance, in welded assemblies, geometric variation in ingoing parts can significantly impair quality. When parts misalign in interfaces, excessive clamping force must be applied, resulting in additional residual stresses in the welded assemblies. This problem may not always be cost-effective to address simply by tightening tolerances. Therefore, under new paradigm of mass customization, the manufacturing approach can be adapted on an individual level. Since parts in welded assemblies are not easily disassembled and reused, interchangeability is not a relevant concern. This recognition means that each welded assembly can be adapted individually for the specific idiosyncrasies of ingoing parts.

This paper focuses on two specific mass customization techniques; permutation genetic algorithms to assemble nominally identical parts, and virtual locator trimming. Based on these techniques, a six-step method is proposed, aimed at minimizing thing effects of geometric variation. The six steps are nominal reference point optimization, permutation GA configuration optimization, virtual locator trimming, clamping, welding simulation, and fatigue life evaluation. A case study is presented which focuses on one specific product; the turbine rear structure of a commercial turbofan engine.

Using this simulation approach, the effects of using permutation genetic algorithms and virtual locator trimming to reduce variation are evaluated.

The results show that both methods significantly reduce seam variation. However, virtual locator trimming is far more effective in the test case presented, since it virtually eliminates seam variation. This can be attributed to the orthogonality in fixturing. Seam variation is linked to weldability, which in turn has significant impact on estimated fatigue life. These results underscore the potential of virtual trimming and genetic algorithms in manufacturing, as a means both to reduce cost and increase functional quality.

Commentary by Dr. Valentin Fuster
2017;():V002T02A110. doi:10.1115/IMECE2017-71405.

Faster optimization algorithms, increased computer power and amount of available data, can leverage the area of simulation towards real-time control and optimization of products and production systems. This concept — often referred to as Digital Twin — enables real-time geometry assurance and allows moving from mass production to more individualized production.

To master the challenges of a Digital Twin for Geometry Assurance the project Smart Assembly 4.0 gathers Swedish researchers within product development, automation, virtual manufacturing, control theory, data analysis and machine learning. The vision of Smart Assembly 4.0 is the autonomous, self-optimizing robotized assembly factory, which maximizes quality and throughput, while keeping flexibility and reducing cost, by a sensing, thinking and acting strategy. The concept is based on active part matching and self-adjusting equipment which improves geometric quality without tightening the tolerances of incoming parts. The goal is to assemble products with higher quality than the incoming parts. The concept utilizes information about individual parts to be joined (sensing), selects the best combination of parts (thinking) and adjust locator positions, clamps, weld/rivet positions and sequences (acting).

The project is ongoing, and this paper specifies and highlights the infrastructure, components and data flows necessary in the Digital Twin in order to realize Smart Assembly 4.0. The framework is generic, but the paper focuses on a spot weld station where two robots join two sheet metal parts in an adjustable fixture.

Commentary by Dr. Valentin Fuster
2017;():V002T02A111. doi:10.1115/IMECE2017-71456.

Variation simulation is one important activity during early product development. It is used to simulate the statistical distribution of assemblies or sub assemblies in intended manufacturing process to assure that assembly, function and aesthetical properties comply with the requirements set. In non-rigid variation simulation, components or sub assemblies can deform during assembly. To simulate non-rigid variation the Method of Influence Coefficient (MIC) is typically used. Solving the necessary sensitivity matrices used by MIC is time consuming. In this article we will apply the Sherman-Morrison and Woodbury formula (SMW) for updating the sensitivity response in the different assembly steps. It is shown that SMW can lead to substantial saving in computation time, when compared to the standard MIC.

Topics: Simulation
Commentary by Dr. Valentin Fuster
2017;():V002T02A112. doi:10.1115/IMECE2017-72526.

Product requirements, tolerance standards and design experience are three main aspects need to be considered during assembly tolerance design process. Currently the standards of tolerance has been included in the process of computer aided tolerance design. The representation for geometrical product specification and verification knowledge has been studied as well. However, the studies mentioned above is lack of a unified knowledge representation to visually express product requirements and design experience. A semantic hierarchical representation structure of assembly tolerance is proposed in this paper to establish the mapping between the geometric feature of the part and the tolerance type as well as tolerance value. A domain ontology model for assembly tolerance design is established with OWL ontology to describe domain information while SWRL rules to enrich the semantics of domain ontology. The application of the model in the proposed hierarchical representation structure enables the consideration tolerance standards, product requirements and design experience of in computer aided tolerancing process, by which the assembly tolerance design knowledge is able to be shared effectively. The application of proposed model is verified by an instance of assembly tolerance reasoning in this paper.

Commentary by Dr. Valentin Fuster
2017;():V002T02A113. doi:10.1115/IMECE2017-72661.

High-precision spindles have significant influence on the machining precision and finishing quality largely due to their motion errors. However, the analysis of rotation accuracy is quite not easy in design stage because of the neglecting of geometric errors and deformations of parts in the traditional dimension chains. Hence, a theoretical analysis model is built in present study to do the prediction. The 3D error accumulation path is recognized by Datum Flow Chain (DFC) and the key tolerances are modeled by Small Displacement Torsor (SDT). Thereafter, the variation propagation is conducted by Homogeneous Transformation Matrices (HTM) and the geometric misalignment in the spindle is calculated. Then, an FEA model is built with Timoshenko beam elements and the deformation is calculated after the geometric misalignment is applied to the model. As spindle rotates, the trajectory of the spindle nose is obtained. Finally, the Monte Carlo (MC) method is used to get the distribution and the range of motion errors. To verify the feasibility and reliability of the analysis model, the radial and axial motion errors of a double supported high-precision spindle are analyzed.

Commentary by Dr. Valentin Fuster

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