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The use of sheet magnesium for automobile body applications is limited, in part, due to its low room temperature formability. Elevated temperature forming of magnesium sheet could enable the manufacture of automobile body closure and structural panels to meet vehicle mass targets. The effect of temperature in improving the formability of sheet magnesium has been known since the 1940's; however, automobile applications for sheet magnesium still have been very limited. The present work characterizes the elevated temperature mechanical behavior of commercially available magnesium sheet alloys at temperatures between 300°C and 500°C. The materials are then evaluated using both warm forming and superplastic forming technologies.

Forming Limit Curves (FLCs) were developed for the 5083 aluminum alloy at conditions simulating high temperature processes such as superplastic and quick plastic forming. Sheet samples were formed at 450 °C and at a constant strain rate of 5x10-3 s-1, by free bulging into a set of elliptical die inserts with different aspect ratios. Friction-independent formability diagrams, which distinguish between the safe and unsafe deformation zones, were constructed. Although the formability diagrams were confined to the biaxial strain region (right side quadrant of an FLD), the elliptical die insert methodology provides formability maps under conditions where traditional mechanical stretching techniques are limited.

Retrogression heat treatments were developed to improve the formability and mechanical behavior of age-hardenable aluminum wrought products in both the aerospace and automobile industries. The heat treatments can provide an improvement in the flanging and trimming behavior of age-hardenable aluminum sheet alloys. The present paper reviews the effect of retrogression heat treatments on flanging by demonstrating reduced springback and increased flange length; on trimming by showing the elimination of metal slivers; and on shape fixability through a three point deflection test. This work should aid in the development of improved aluminum alloys and modified forming processes to enable the increased use of aluminum sheet products.

Warm forming offers the potential to produce complex aluminum components at high production volumes. The present paper evaluates the warm forming potential of seven different commercial aluminum alloys; 2008-T4, 5454-H32, 5754-O, 6111-T4, GZ45-T4, and two 5083 alloys. The mechanical behavior of these alloys is studied between 25°C and 300°C, and compared with a variety of materials from the literature, especially 5182, which has been well characterized. Analysis of total elongation, strain rate sensitivity, and strain localization demonstrate that 5083 and 5754 have promising warm forming performance.

Global regulations intended to enhance pedestrian protection in a vehicle collision, thereby reducing the severity of pedestrian injuries, are presenting significant challenges to vehicle designers. Vehicle hoods, for example, must absorb a significant amount of energy over a small area while precluding impact with a hard engine compartment component. In this paper, a simple passive approach for pedestrian protection is introduced in which thin metal alloy sheets are bent to follow a C-shaped cross-sectional profile thereby giving them energy absorbing capacity during impact when affixed to the underside of a hood. Materials considered were aluminum (6111-T4, 5182-O) and magnesium (AZ31-O, AZ61-O, ZEK100) alloys. To evaluate the material effect on the head injury criterion (HIC) score without a hood, each C-channel absorber was crushed in a drop tower test using a small dart.