Bifurcation analysis of wrinkling formation for anisotropic sheet

Surface distortions in the form of localized buckles and wrinkles are often observed in the sheet metal forming process. In many cases the presence of wrinkles in the final praduct is unacceptable for 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-Viasov shell theory is used. The effects of the various material parameters (yield stress, strain hardening coefficient and normal anisotropy parameter) and geometric parameters on WLD are investigated numerically and compared with Kawai's and Havranek's experiment(1975).