基于厚度梯度准则的薄板成形极限图建立方法

介绍一种预测薄板成形极限的新准则——厚度梯度准则,该准则基于薄板颈缩时沿垂直于颈缩方向的厚度梯度分布存在极值RC。在薄板成形过程中,当板面内的厚度梯度值小于临界厚度梯度值RC时,认为薄板发生颈缩。基于厚度梯度准则,结合对IF钢成形极限试验的有限元仿真,计算获得其成形极限图,计算结果与试验数据吻合较好。将厚度梯度准则与有限元方法相结合,可在已知薄板单拉性能参数的条件下计算获得其成形极限图。

Prediction of Forming Limit Diagram in Sheet Metal Forming Based on Thickness Gradient Criterion

A novel criterion,namely,thickness gradient criterion for predicting forming limit diagram(FLD) was presented.This criterion was based on the critical thickness gradient RC which existed in the direction perpendicular to the necking when the failure developed.During the forming process, when the ratio of thickness in neighboring regions of a deforming sheet metal drops below the critical magnitude RC,necking develops.The FLD of interstitial-free steel(IF steel) was calculated based on the "thickness gradient criterion" by means of the FE simulation of Nakazima experiment of IF steel.Good correlation between the simulation and experimental results is indicated.By combining the "thickness gradient criterion" and FEM,the FLD of sheet metal can be calculated when the tensile properties is available.