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Journal Article

Analysis of Single Lap Adhesive Joints between Magnesium and Other Structural Automotive Materials

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.
Technical Paper

Fatigue of Spot Friction Welded Joints of Mg-Mg, Al-Al and Al-Mg Alloys

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.
Technical Paper

Spot Friction Welding of Mg-Mg, Al-Al and Mg-Al Alloys

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.
Technical Paper

Fatigue of Friction-Stir Welded Joints in Aluminum Tailor Welded Blanks

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.
Technical Paper

Effect of Weld Pitch Variation on the Performance of a Two-Piece Spot-Welded Body Structure

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.
Technical Paper

Effect of Process Variables on the Static and Fatigue Properties of Self-Piercing Riveted Joints in Aluminum Alloy 5754

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.
Technical Paper

Performance of Adhesive Joints in an Automotive Composite Structure

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.