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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.

This paper presents a comparison of aqueous corrosion rates in 5% NaCl solution for eight experimental creep-resistant magnesium alloys considered for automotive powertrain applications, as well as three reference alloys (pure magnesium, AM50B and AZ91D). The corrosion rates were measured using the techniques of titration, weight loss, hydrogen evolution, and DC polarization. The corrosion rates measured by these techniques are compared with each other as well as with those obtained with salt-spray testing using ASTM B117. The advantages and disadvantages of the various corrosion measurement techniques are discussed.

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.

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.

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.

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.

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.

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 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.

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.

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.