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Technical Paper

Characterization of Film Formation on Magnesium Alloys due to Corrosion in Engine Coolants

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.
Technical Paper

Effects of Processing Parameters on Thickness Variation in Pressure Sequence Hydroforming

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.
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

Influence of Weld Characteristics on Numerically Predicted Deformation Behavior of Aluminum Tailor Welded Blanks

The automotive industry is continuously investigating means for producing lighter-weight vehicles in order to improve fuel efficiency and reduce emissions. Lightweight materials, such as aluminum, are often used to replace steel in automotive body structures, such as hoods, decklids, fenders, and their corresponding reinforcements. To further reduce weight and improve stiffness, sheets of different gages and/or properties are welded together prior to stamping to form “tailored” blanks. The presence of the weld and the gage mismatch in these blanks, often result in premature failure, which can be expressed as a shift in the forming limit diagram. Several process variables affect this change in deformation behavior including the welding process used to join the blanks, the weld orientation, the weld geometry, and the mechanical properties of the weld and the base materials.