Method for predicting forming limit diagram of sheet metal

The invention provides a method for predicting a forming limit diagram of a metal plate, which is an improved M-K method. The method is characterized in that a groove angle is kept unchanged in a loading process, and the groove angle can be given through a loading path; and, according to the method, accurate assignment is carried out on the groove angle, the repeated cycle calculation process of the initial groove angle in the original M-K model is eliminated, the FLD theoretical calculation efficiency is greatly improved, and the prediction precision is consistent with that of the original M-K model. 本发明提供了一种金属板材成形极限图的预测方法，为改进的M-K方法，该方法的特点是：凹槽角度在加载过程中保持不变，并且凹槽角度可以通过加载路径给定：该方法通过对凹槽角度的精准赋值，消除了原始M-K模型中对初始凹槽角度的重复循环计算过程，大幅的提升了FLD理论计算的效率，并且预测精度与原有的M-K模型一致。