Search Results

Aluminum alloy sheets are used for automotive body-panels, but their small Young's modulus results in inferior shape-fixability than conventionally-applied steel sheets with similar strengths. Smaller radius of curvature, indicating better shape-fixability, is found at the center of a panel press-formed with higher blank holder force (BHF). Higher force can be applied for press-forming of alloy sheets with larger strain-hardening exponent (n value) induced by an increased addition of Mg. Recently-developed 5000 series alloy sheets containing 5.5 pct Mg and 0.3 pct Cu have an elongation over 33 pct at an ultimate tensile strength of 270 MPa and can be press-formed with better shape-fixability.

The application of tailored blanks to autobody parts has progressed because of its numerous advantages. The forming of tailored blanks has, however, a lot of technical problems. Among the problems, weld-line movement and formability deterioration are the most significant ones in case of deep drawing. The weld-line movement and formability change were examined experimentally as a function of weld-line location in square cup deep drawing. The weld-line movement of tailored blank consists of two sources. One is the geometrical reason, and the other is due to the hardening of weld bead. The formability of tailored blank is inferior to that of an original blank by the existence of hardened weld region. The mode of fracture changes from wall breakage to a fracture adjacent to punch radius when the weld-line was close to the punch corner.