Abstract: Sheet metal forming limit prediction criterion based on general plastic work is brought out. The integral value of the general plastic work criterion is not a constant but a function relevant to strain paths. The effect of strain path, strain-hardening exponent, anisotropy coefficient and the initial thickness of the material on forming limit is considered. The constant in the criterion can be determined by the forming limit strains under tensile strain path. Then the limit strains under other strain paths between uniaxial tension to equi-biaxial tension can be determined by the criterion combined with numerical simulation of forming process. The calculation as well as the experimental results show that the criterion can predict forming limits for steel and aluminum sheets exactly and makes it possible to determine forming limit strains under defferent strain paths only through tensile test.

Key words: Forming limit, Numerical simulation, Plastic deformation energy, Sheet metal forming