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针对盘毂冷精整成形时出现的凹模掉块问题,对凹模进行断裂分析,得出断裂的原因为:凹模齿形尖角处易出现微裂纹,在精整时凹模底端齿形部分承受轴向拉应力约为1 170 MPa,盘毂预制坯通过凹模后轴向拉应力消失,在交变应力作用下微裂纹逐渐扩展至失稳,凹模发生疲劳断裂,出现掉块缺陷。为避免凹模的早期失效,提出在凹模上增加退让带来降低精整时凹模底端齿形部分承受的轴向拉应力,数值模拟结果显示,增加退让带后,坯料在脱离工作带后不再接触凹模底端,并且退让带增加了工作带齿形部分的强度,精整时最大轴向拉应力降至600 MPa。生产实践表明,改进措施可避免凹模的掉块缺陷。
In order to solve the problem of die dropping due to the cold finishing of the hub, the fracture analysis of the die is made. The reason for the fracture is as follows: the micro-cracks are easily appeared on the sharp corners of the die. When the bottom of the die is finished Tensile part of the axial tensile stress to withstand about 1 170 MPa, hub preform blank through the die after the axial tensile stress disappears, alternating stress in the micro-cracks gradually expanded to instability, the die fatigue fracture occurs out Block defects. In order to avoid the early failure of the die, it is proposed to increase the concession on the die to reduce the axial tensile stress on the bottom of the die during the finishing process. The numerical simulation results show that after the concession belt is increased, No contact with the bottom of the die, and the concession belt with the work to increase the intensity of the toothed part, finishing the maximum axial tensile stress down to 600 MPa. Production practice shows that improvements can prevent the die from falling defects.