板料成形极限应力图研究

基于塑性应力应变关系，推导出极限应力与极限应变相互转换关系，针对分散性失稳、凹槽失稳和平面应变漂移失稳等准则，进行了双线性应变路径、曲线应变路径和复合应变路径下成形极限应力图的理论计算。结果表明，成形极限应力图不受应变路径影响，对于同一失稳准则，在不同加载应变路径下几乎为同一条曲线。因此，成形极限应力图作为复杂加载路径的成形极限判据更加方便和实用。

INVESTIGATION OF FORMING LIMIT STRESS DIAGRAMS OF SHEET METALS

Transformation between limit strain and limit stress is evolves on the basis of plastic relationship between strain and stress. Theoretic FLSDs (Forming limit stress diagrams) are calculated under linear strain path, curvilinear strain path and compounded strain path according to diffuse instability theory, groove instability theory and plane strain floating instability theory. The result shows that FLSD is independent of strain path, and that the FLSD under different strain paths are almost the same curve according to the same instability theory. So it's more convenient and practical to use FLSD as the criterion of forming limit.