Abstract: Bolt looseness is a difficult problem in automobile reliability, which often troubles automobile designers. In this paper, the pre-tightening force, mounting torque and contact surface yield strength of the bolts are calculated and checked by technical cooperation with fastener manufacturers. According to the problems of the contact surface of the suspension bracket, such as the risk of yield collapse and the lack of the pre-tightening force of the bolts, the corresponding improvement schemes are made respectively, and the range of the mounting torque of the fastening bolt is finally determined, to meet the requirements of mounting rubber pad pre-tightening force. The mounting torque determined by the calculation method in this paper is fixed, and after fastener lateral vibration test and cross-country road test, the mounting rubber pad fastening bolts of powertrain mount do not loose again, it can be seen that the bolt loosening calculation check and improvement program is effective. In this paper, the pre-tightening force, mounting torque and the strength of the contact surface of the bolts are calculated and improved, which provides a very good solution to the problem of automotive bolt loose ideas and methods.

Key words: Bolt looseness; Pre-tightening force; Mounting torque; Yield strength

摘要： 螺栓松动作为汽车可靠性问题中的一个难题，经常困扰着汽车设计人员。文章将针对 一款动力总成悬置胶垫螺栓松动问题，通过与紧固件厂家技术合作，对螺栓预紧力、安装扭 矩和接触面屈服强度进行计算校核。并针对计算发现的悬置支架接触面存在的屈服压溃风险 及螺栓预紧力不足等问题，分别制定了相应的整改方案，最终确定了此悬置紧固螺栓的安装 扭矩范围，满足悬置胶垫紧固预紧力要求。根据文章计算方法确定的安装扭矩进行定扭后， 通过紧固件横向振动试验和越野路路试，动力总成悬置胶垫紧固螺栓未再出现松动现象，可 以看出文中螺栓松动计算校核和改进方案有效。文中案例通过对螺栓预紧力、安装扭矩和接 触面屈服强度等进行符合性计算校核和改进，为汽车螺栓松动问题整改提供了一个非常好的 解决思路和方法。

关键词: 螺栓松动；预紧力；安装扭矩；屈服强度