Study on wrinkling limit diagram of anisotropic sheet metals

Surface distortions in the form of localized buckles and wrinkles are often observed in sheet metal forming process. In many cases the presence of wrinkles is unacceptable for the final product and the purposes of assembly. Because of the trend in recent years towards thinner gauges and higher strength, wrinkling is increasingly becoming a more common and troublesome mode of failure in sheet metal forming. In this study, a numerical analysis for evaluating a wrinkling limit diagram (WLD) for an anisotropic sheet subjected to biaxial plane-stress is presented. Here the scheme of plastic bifurcation theory for thin shells based on the Donnell–Mushtari–Vlasov shell theory is used. The effects of various material parameters — yield stress, strain-hardening coefficient and normal anisotropy — and geometrical parameters on the WLD are investigated numerically and compared with the results of the experiments of Kawai and Havranek.