Weld Region Representation during the Simulation of TWB Forming Behavior
The critical issue during finite element analysis of Tailor Welded Blanks is the handling of weld region - either the weld region may be treated just as a weld line (without imposing mechanical properties) or as a weld zone (by imposing separate mechanical properties to the weld region). The formability of TWB will be affected not only by the weld characteristics, but also by the relative mechanical properties of the weld zone and the base metal. In this work, the importance of weld zone assumption during the finite element simulation of forming of TWB will be analyzed, by obtaining the domain of weld conditions (weld width, weld orientations and base metal-weld property combinations) wherein the weld line assumption breaks down. The tensile and Limiting Dome Height (LDH) testing of the TWB are simulated using PAM STAMP 2G, an elastic-plastic FE code. Initially, the FE simulation results of tensile testing of un-welded and welded blanks are validated with that of literature results. In order to obtain the domain of weld conditions, tensile test is simulated with ASTM standard dimensions. In LDH simulations, samples deforming near plane strain and balanced biaxial stretching are simulated. Load-progression behavior is monitored throughout the simulations. It is found from the analysis that modeling weld region as weld line is not accurate for all the weld conditions. The domain of weld conditions, wherein weld line assumption breaks down, depends on the deformation mode or part shape. In the case of transverse weld orientation, the yield strength of weld (YSw) decides the deformation of TWB. Hence the domain of weld conditions obtained for weld zone modeling is independent of strain hardening exponent of weld (nw) and weld width. The contribution of longitudinal weld to TWB deformation is significant unlike in transverse weld orientation. Therefore the domain of weld conditions for weld zone modeling in longitudinal weld orientation depends on yield strength of weld (YSw), strain hardening exponent of weld (nw) and weld width.
R. Ganesh NARAYANAN, K. NARASIMHAN
Tailor Welded Blanks, Weld Region, Finite Element simulation, Forming.