Abstract: The bifurcation, bulging and wrinkling behaviors of square sheet metals with non-uniform tension (called as YBT) are numerically simulated, based on Hill's sufficient condition ofυniqueness for elastic plastic materials, virtual power-rate variational principle, and Mindlin shell element model The calculated results are compared with experimental ones Finally, the effects of the sheet thickness t and the tensile width B at the boundary surface of bifurcation and wrinkling models are discussed ...