中文摘要：

以汽车热冲压件的典型特征结构——U形梁为研究对象,将BR1500HS钢高温破裂准则嵌入热冲压成形有限元模型中,实现了对高强钢板高温破裂行为的有效预测。基于预测模型,揭示了变形速率对板料破裂起始时刻、位置及扩展方向的影响。结果表明：随变形速率的增大,起裂时刻缩短,起裂位置变化不明显;起裂位于U形梁一端的侧壁,裂纹沿U形梁纵向随形扩展,随后另一端侧壁处开始发生二次破裂,裂纹也沿U形梁纵向随形扩展,但未与初始裂纹产生交汇;变形速率较小时,二次破裂位于侧壁靠近凹模圆角处;变形速率较大时,二次破裂位于侧壁靠近凸模圆角处。

英文摘要：

For the typical feature structure of automotive hot-stamped part U-shaped beam,the prediction of fracture behavior of high strength sheet was realized effectively by implementing the fracture criterion at elevated temperature of BR1500 HS into the finite element model of hot stamping forming. Based on the prediction model,the influences of deformation velocity on the fracture initiation moment,location and propagation direction were clarified. The results show that with the increase of deformation velocity,the fracture initiation moment decreases,but the fracture initiation location has no obvious change. The initial fracture locates at the side wall at one end of the Ushaped beam,and the crack propagates along the longitudinal direction of the U-shaped beam. Then,the secondary fracture occurs at the other end of the U-shaped beam,and the secondary crack also propagates along the longitudinal direction,but the initial crack does not converge. When the deformation velocity is small,the secondary fracture locates at the side wall near the die fillet; and when the deformation velocity is large,the secondary fracture locates at the side wall near the punch fillet.