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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.

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 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 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.

Current plastic intake manifolds are manufactured using the injection molding process. In this paper, thermoforming is explored as an alternative to injection molding for making intake manifold shells, which can then be joined by one of the welding techniques used for thermoplastic materials. The investigation reported here includes press-forming experiments of a simple bowl shaped shell and subsequent welding experiments to join these shells.