Theoretical Forming Limit Diagram Based on Induced Stress in the Thickness Direction

The conventional theoretical forming limit diagram (FLD) based on the plane stress state has defects due to neglect of in thickness direction sheet. It is urgent study FLD which considers direction. Through finite element simulation, it further confirmed that will be induced deformation process. At same time, effect not as always applied during Based Modified Maximum Force Criterion (MMFC) instability theory, C-H Mises and Hill48 yield criterion, effects two stresses are compared. also affects sensitivity coefficient normal anisotropy r, but does significantly change stress-strain index n Forming Limit Curves (FLC). calculations three materials TRIP780, AA5182, 5754O compared with experimental data, proves more accurate than stress.