以汽车热成形件的典型特征结构--U形梁为研究对象,将高温破裂准则与数值模拟相结合,对BR1500HS钢板在热成形中的高温破裂现象进行了预测,分析了凹模圆角半径R对该钢板破裂行为的影响.结果表明:高强钢热成形破裂预测模型预测得到的破裂位置与试验结果吻合良好,凸模温度的预测值与实测值的相对误差在10%以内,该模型可靠性高;随着R增大,板料起裂时间延长;起裂均位于U形梁一端的侧壁,但起裂位置沿高度方向有差异;板料破裂均沿U形梁纵向扩展,R为2,6.5 mm时在U形梁另一端侧壁处发生了二次破裂,破裂易发生在靠近较小半径模具圆角的U形梁侧壁.
Taking the typical feature structure, namely U-shaped beam, of automotive hot-stamped parts as the object, the high-temperature fracture phenomena of BR1500HS steel sheet during hot forming was predicted by the combination of high-temperature fracture criterion and numerical simulation.The effects of female die fillet radius R on the steel sheet fracture behavior were analyzed.The results show that the fracture locations predicted by the hot forming fracture prediction model of high strength steel agreed well with the experimental results, and the relative error was below 10% between the predicted and experimental punch temperatures, indicating the relatively high reliability of the model.With R increasing, the fracture initiation time of the plank increased.The fracture initiation located at the side wall of one end of the U-shaped beam, but these locations along the height direction were different.The plank fractured along the longitudinal direction of the U-shaped beam, and the secondary fracture occurred at the side wall of another end of the U-shaped beam when R was equal to 2 mm and 6.5 mm.The fracture tended to appear at the side wall of U-shaped beam near the mould corner with a relatively small corner radius.
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