Resumen de Postbifurcation behavior of wrinkles in square metal sheets under Yoshida Test
Xiaofang Wang, H.N. Lee Lawrence
The stretching of a square sheet along one of its diagonals, called “Yoshida Test”, has been developed to simulate the wrinkling behavior in press forming of steel sheets into autobody panels. The finite deformation, onset of wrinkling, and growth of wrinkles in such a specimen are investigated. Hill's yield criterion for sheet materials having the normal anisotropy and Hill's quasistatic bifurcation criterion are employed. The growth of wrinkles in the finite deformation process is incrementally and numerically determined by a thin shell finite element in a convected coordinate system. The Lagrangian formulation of the thin shell finite element is based on Hill's variational principle for elastic-plastic solids, a modification of Love-Kirchhoff postulates and a quasiconforming element technique. The shell element fulfills the interelement C1 continuity condition in a variational sense. Reasonable agreements between the present numerical results and available analytical and experimental results are shown.
