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This paper will present the results of 3-D finite element analyses of single lap adhesive joints between magnesium and three other automotive materials, namely steel, aluminum and SRIM composites. The modulus of magnesium is lower than that of either steel or aluminum, but is higher than that of SRIM. Thus, this study aims at determining the effect of the difference in substrate modulus on the deformation, stress and strain distributions and maximum stresses in adhesive joints of magnesium with the other three materials. In addition, the effect of adhesive modulus is also explored.

A ductile failure criterion (DFC), which defines the stretching failure at localized necking (LN) and treats the critical damage as a function of strain path and initial sheet thickness, was proposed in a previous study. In this study, the DFC is revisited to extend the model to the low stress triaxiality domain and demonstrates on modeling forming limit curve (FLC) of TRIP 690. Then, the model is used to predict stretching failure in a finite element method (FEM) simulation on a TRIP 690 steel rectangular cup draw process at room temperature. Comparison shows that the results from this criterion match quite well with experimental observations.

This study considers the thermal stresses in single lap adhesive joints between magnesium and steel. The source of thermal stresses is the large difference in the coefficients of thermal expansion of magnesium and steel. Two different temperature differentials from the ambient conditions (23°C) were considered, namely -30°C and +50°C. Thermal stresses were determined using finite element analysis. In addition to Mg-steel substrate combination, Mg-Mg and steel-steel combinations were also studied. Combined effect of temperature variation and applied load was also explored. It was observed that temperature increase or decrease can cause significant thermal stresses in the adhesive layer and thermal stress distribution in the adhesive layer depends on the substrate combination and the applied load.

An experimental study was conducted to investigate the potential of spot joining aluminum with nylon using frictional heat. The process utilizes the heat generated by friction between a rotating tool surface and the aluminum sheet surface to melt nylon locally in the joining area and create a mechanical interlock between the aluminum and nylon sheets. Lap shear joint specimens were prepared using this process to investigate the effect of several parameters such as tool geometry, tool RPM, tool hold time, tool plunge depth and tool feed rate. Tensile tests were conducted to evaluate the joint strength and to investigate the failure mechanisms of the joint. Furthermore, the effects of cleaning the aluminum surface and baking of the nylon on the joint strength were also studied in this paper. Finally, friction heat generated joints were compared with adhesively bonded joints between aluminum and nylon.

The effects of lubricant on lap shear strength of Spot Friction Welded (SFW) joints made of 6111-T4 alloys were studied. Taguchi L8 design of experiment methodology was used to determine the lubricant effects. The results showed that the lap shear strength increased by 9.9% when the lubricant was present at the top surface compared to that of the baseline (no lubricant) whereas the lap shear strength reduced by 10.2% and 10.9% when the lubricant was present in the middle and at the bottom surfaces compared to that of the baseline (no lubricant), respectively. The microstructure analysis showed a zigzag interface at the joint between the upper and the lower sheet metal for the baseline specimen, the specimens with the lubricant at the top and at the bottom. However, a straight line interface is exhibited at the joint between the upper and the lower sheet for the specimen with the lubricant in the middle. The weld nugget sizes of the lap shear tested specimens were measured.

This study utilized Rutherford Backscattering Spectroscopy (RBS) and Auger Electron Spectroscopy (AES) to determine the thickness and composition of corrosion films formed on magnesium alloys exposed to experimental engine coolants intended for use with creep-resistant magnesium alloy engine blocks. Knowledge on the nature of the film formed may produce a better understanding of corrosion inhibition and protection requirements for these materials. This paper will first briefly review the RBS and AES techniques as applied to the characterization of surface films on metals. It will then present results from experiments conducted with pure magnesium and two different magnesium alloys in two engine coolants.

Spot friction welding is considered a cost-effective method for joining lightweight automotive alloys, such as magnesium and aluminum alloys. An experimental study was conducted to investigate the strength of spot friction welded joints of magnesium to magnesium, aluminum to aluminum, magnesium to aluminum and aluminum to magnesium. The joint structures and failure modes were also studied.

Spot friction welding shows advantages over resistance spot welding for joining light alloys for automotive applications. In this research, fatigue behaviors of spot friction welded joints in lap shear specimens of AM-60 magnesium alloy and AA 5754 aluminum alloy were investigated. Static and fatigue tests were conducted with Mg-Mg, Al-Al and Al-Mg specimens. Fatigue S-N curves were obtained for all these specimens using load-controlled fatigue tests. Finite element analysis was conducted to investigate the stress distribution and the location of maximum stresses in spot friction welded joints in Mg-Mg specimens.

This study reports the performance of three different automotive magnesium substrate materials (AM60B diecastings, AZ31-H24 sheet, and AM30 extrusions), each bonded to a common aluminum reference material with two different toughened adhesives. The magnesium substrates were pretreated with six different commercial pretreatments both with and without a final fused-powder polymeric topcoat. These samples were then evaluated by comparing initial lap-shear strength to the lap-shear strength after cyclic-corrosion testing. Additionally, use of a scribe through the polymer primer permitted assessment of: 1) distance of corrosion undercutting from the scribe (filiform), and 2) percent corrosion over the area of the coupon. The results showed that the performance of each magnesium pretreatment varied on cast AM60B, sheet AZ31-H24, and extruded AM30 substrates.

This paper presents the results of an experimental study conducted to evaluate the effects of four material characteristics and two driver characteristics on the perception of automotive interior materials. The perceptual characteristics of the materials were measured using two sensing conditions, namely, visual sensing only and combined visual and tactile sensing. The experiments were conducted using the Taguchi's L16 orthogonal array with seven independent variables, namely material type, surface roughness, compressibility, driver's age, driver's gender, and sensing method. Twenty-four subjects participated in the experiments. Each subject was asked to evaluate four treatment combinations and provide ratings using seven 5-point semantic differential scales. In addition, physical measurements were made on surface roughness, coefficient of friction, and compressibility.

Among the various high strength steels available today, boron steels are finding increasing applications in bumper beams and other crash resistant structures, primarily for their high strength. However, to overcome the forming difficulty at room temperature and to achieve the microstructural changes needed for high strength, manufacturing of boron steel parts is done under hot forming conditions. In this study, the effect of three principal bumper design parameters, namely depth, thickness and corner radius on the formability of a hat section bumper beam was considered. Using a forming simulation program, 27 different combinations of these three design parameters were examined for forming limits, failure types and failure locations. The bumper beams were also examined for energy absorption in pendulum impact tests. Recommendations are made for the design of boron steel bumper beams based on both impact energy absorption and formability.

The automotive industry is expected to accelerate the transition to revolutionary products, rapid changes in technology and increasing technological sophistication. This will require engineers to advance their knowledge, connect and integrate different areas of knowledge and be skilled in synthesis. In addition, they must learn to work in cross-disciplinary teams and adopt a systems approach. The College of Engineering and Computer Science (CECS) at the University of Michigan-Dearborn (UM-Dearborn) responded by creating interdisciplinary MS and Ph.D. programs in automotive systems engineering (ASE) and augmenting them with hands-on research. Students at the undergraduate level can also engage in numerous ASE activities. UM-Dearborn's ASE programs offer interesting and possibly unique advantages. The first is that it offers a spectrum of ASE degree and credit programs, from the MS to the Ph.D. to continuing education.

This paper describes the results of dynamic denting experiments conducted on AA5754 and AA6061 alloys. Dynamic denting tests were performed using a drop weight impact machine. The drop height was varied from 38 mm to 914 mm to generate impact velocities ranging from 53.4 m/min to 254 m/min. The dent depth created at different drop heights was related to the input impact energy and peak load observed in the tests. The effects of sheet thickness and yield strength were explored.

Self-piercing riveting is a relatively new process for joining sheet metals in automotive applications. Its importance is growing in the automotive industry because of its advantages over spot welding aluminum alloys. One of these advantages is the higher fatigue strength, which is useful in designing body structures. This paper presents experimental data on the effects of several process variables, such as rivet diameter, rivet length, rivet hardness, sheet thickness and die shape, on the static and fatigue properties of self-piercing riveted joints in aluminum alloy 5754. Statistical analysis has been performed to examine the relative importance of these variables on the static and fatigue performance of the joints.

This paper presents cost-benefit analysis of glass and carbon fiber reinforced thermoplastic matrix composites for structural automotive applications based on press forming operation. Press forming is very similar to stamping operation for steel. The structural automotive applications involve beam type components. The part selected for a case study analysis is a crossbeam support for instrument panels.

The purpose of this study is to examine the effect of spot weld spacing on the stiffness and natural frequency of a two-piece welded body structure. The variation in spot weld spacing may occur either by design or due to assembly mistakes. In this study, rectangular beam cross sections with six different weld flange orientations are first considered. Finite element analysis is performed to compare the fundamental frequencies of these sections in bending and torsion. Weld pitch and sheet thickness are varied on two of the sections considered, namely the L-shaped and the clamshell sections. The effects of spot weld spacing on the bending stiffness, torsional stiffness, frequency response and mode shapes of these two sections are determined. Comparisons are made with seam welded sections. It is shown that the torsional stiffness and first torsional frequency can be severely affected by weld pitch, but the effect on the bending performance is not as severe.

The tube hydroforming process is being used by the automotive industry to manufacture parts that are typically produced by stamping and welding processes. The advantages of tube hydroforming over conventional processing methods (i.e. stamping and welding processes) include part-consolidation, weight saving, and improved strength and stiffness of the formed structure. However, one of the drawbacks of the process is the incomplete knowledge base of the effects of processing parameters on the final product. Two of the most significant parameters in the PSH process are the initial level of pressurization, and the amount of die displacement required to achieve the final shape. It is therefore the objective of this paper to investigate the effect of these two parameters on the final shape and thickness distribution in the tube. The paper presents the results of numerical models and experimental validation of these results.

Based on findings from micromechanical studies, a Ductile Failure Criterion (DFC) was proposed. The proposed DFC treats localized necking as failure and critical damage as a function of strain path and initial sheet thickness. Under linear strain path assumption, a method to predict Forming Limit Curve (FLC) is derived from this DFC. With the help of predetermined effect functions, the method only needs a calibration at uniaxial tension. The approach was validated by predicting FLCs for sixteen different aluminum and steel sheet metal materials. Comparison shows that the prediction matches quite well with experimental observations in most cases.

Seat comfort is a highly subjective attribute and depends on a wide range of factors, but the successful prediction of seat comfort from a group of relevant variables can hold the promise of eliminating the need for time-consuming subjective evaluations during the early stages of seat cushion selection and development. This research presents the subjective seat comfort data of a group of 30 participants using a controlled range of seat foam samples, and attempts to correlate this attribute with a) the anthropometric and demographic characteristics of the participants, b) the objective pressure distribution at the body-seat interface and c) properties of the various foam samples that were used for the test.

With increasing use of biofuels in the automotive industry, it has become necessary to evaluate their effects on the properties of polymers used in the fuel delivery systems. In this study, we have considered the effect of biodiesel on the tensile properties of nylon-6, 30% E-glass fiber reinforced nylon-6 and impact-modified nylon-6. The tensile specimens were immersed in 100% biodiesel for up to 7 days before determining their tensile properties. Another set of specimens were immersed in 100% biodiesel under stressed condition and then their tensile properties were determined. The absorption of biodiesel and their effects on tensile modulus, tensile strength and failure strain are reported in this paper.