Forming-limit diagrams of aluminum tailor-welded blank weld material

The current work develops forming-limit diagrams (FLDs) for weld materials in aluminum tailor-welded blanks (TWBs) under biaxial stretching conditions. Aluminum TWBs consist of multiple-thickness and alloy sheet materials welded together into a single, variable-thickness blank. The manufacture of TWBs and their application in automotive body panels requires their constituent weld material to deform under biaxial loading during sheet-metal stamping. The weld geometry is typically nonuniform and relatively small, causing difficulty if one attempts to determine the weld metal FLDs via traditional experimental methods. The subject work primarily relies on theoretical FLD calculation techniques using the Marciniak and Kuczynski (M-K) method. This numerical technique requires the use of material constants and levels of initial material imperfection that have been experimentally determined using unique miniature tensile specimens to isolate and characterize the weld metal. The experimental and numerical work, together with statistical analysis of the level of initial imperfection, allows generation of both an average and safe FLD. The weld metals studied in this work were produced via autogeneous gas tungsten are welding of a 1- to 2-mm-thick 5000 series aluminum alloy sheet.