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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.

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.

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.

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.

This paper presents the results of fatigue tests conducted on tailor-welded aluminum blanks consisting of 1.66 mm thick and 1.06 mm thick AA 5754-O sheets. The method of joining the sheets was friction-stir welding. The primary purpose of this study was to determine the effect of tensile pre-strains on the fatigue performance of the welded joint. The welded specimens as well as unwelded 1.06-mm thick specimens were subjected to tensile pre-strains of 60 and 80% of their respective uniform strains before the fatigue tests. Fatigue S-N data of all these specimens were compared with similar data for unstrained specimens. Microscopic examinations were conducted to understand the failure modes.

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.

This paper describes an experimental work on the bending springback of aluminum alloy 5754. Experiments were performed using a 90° V-shaped matching die-punch combination, with and without clamping. Clamping was used to create tension during bending. The experimental parameters taken into account are the die radius, sheet clamping torque, sheet thickness and the level of cold work in the sheet.

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.

This paper presents finite element analyses as well as static and fatigue performance of adhesive joints in an automotive composite structure. The automotive composite structure considered is a simply supported beam made by adhesively bonding a flat SRIM panel to the bottom of an SRIM hat section. Finite element analysis of such a beam showed the presence of significant peel stresses in the adhesive layer. Static and fatigue tests were then conducted with transverse tensile loads on adhesively bonded hat sections to determine the failure load in the peel direction. Finite element analysis of the transverse tensile loading condition identified the critical stresses in the adhesive and the failure mode expected in such joints. This study also examined the usefulness of combining adhesive and bolts to improve the joint performance.

This paper presents the static and fatigue strength evaluation of clinched joints in 6111-T4 aluminum alloy sheets. Clinched joints are mechanical joints produced a cold forming technique using a small die-punch combination. A design of experiments approach is used to determine the optimum die-punch combination that produces the least variation in the static pull-out load in single lap shear tests. Fatigue S-N curves are determined for several different clinched joints in load-controlled fatigue tests with the load ratio equal to 0.1. The effect of heat exposure, typically experienced in paint ovens, on the static strength as well as fatigue S-N behavior are also examined.

This paper discusses the design issues related to bolted joints in automotive composites. Pin bearing strength and fatigue test results of bolted joints in both random fiber as well as continuous fiber sheet molding compound composites are reviewed. Fatigue failure modes in bolted joints of these composites are presented. Based on these tests, design guidelines for bolted joints in sheet molding compound composites are proposed. Sheet molding compound (SMC) composites and resin transfer molded (RTM) composites are being considered for applications in automotive chassis components, such as cross members, wheels, and front end structures. Mechanical fasteners will be used to attach these composite components to their supports or other structures. While adhesive joints are preferred in body applications, mechanical fasteners, such as bolts and screws, have some distinct advantages in chassis applications.

Light weight composite materials are being considered in many structural automotive applications such as leaf spring, transmission support member, and wheels. The primary design criteria in all these applications is resistance against fatigue failure. This paper reviews some of the unique features of automotive composites in fatigue loading and discusses their differences with metals, particularly in relation to fatigue crack propagation. Practical consequences of such inherent differences are also discussed.