发动机排气门第二热点疲劳寿命预测方法的研究

摘要

In order to solve the problems existed in gearshift with wet dual clutch transmission, the down-shift control strategy was proposed on the basis of analyzing on gear shift quality evaluation. And then the transmission control system is developed,as well as the control program is compiled.Taking down-shift from 2 to 1 for an example ,positive torque and negative torque down-shifting control tests were carried out under different throttle positions and ideal shifting quality was achieved,it verified the validity of the control strategy.The result indicated that the speed of vehicle changed gentlely without distinct impact,and the oil temperature hardly changed,which can meet the requirement of the vehicle for ride and speed in shifting control and better shifting quality is obtained with the vehicle.%基于ANSYS建立了发动机气门、气门座与导管组件接触模型,并以此分析了排气门异常工况下的应力状态及其S-N关系曲线,计算出与发动机气缸内压力相对应的排气门第二热点处载荷谱及其累积疲劳损伤率.研究表明:排气门第二热点处存在高弯曲应力,其峰值分别发生在燃烧冲击及落座瞬间；但燃烧冲击时对疲劳损伤率的贡献远高于气门落座时.研究还表明:排气门正常工况下为无限疲劳寿命,影响其早期疲劳失效的主要因素是工况—气门往复运动偏摆角；论文基于实例讨论了发动机工作参数与排气门疲劳寿命之间的关系规律.