柴油机活塞的热疲劳寿命预测

Prediction of thermal fatigue life for diesel engine piston under states of multiaxial stresses

按照热疲劳和高温低周疲劳断裂机制研究了柴油机活塞的寿命和安全性评定．采用Ｍｉｓｅｓ当量准则，求出当量应变范围，通过实验证实，它与寿命之间存在着ＭａｎｓｏｎＣｏｆｆｉｎ公式关系，并把这一表达式推广到复杂应力状态且摆脱结构形状和尺寸的影响，从而可把实验室中利用试件进行的一维状态下疲劳特性的试验结果用于复杂应力状态下不同形状和尺寸的构件．最后把这一成果用于１２Ｖ－１８０型柴油机活塞寿命预测并证实同相热疲劳模式预测结果是合适的．

The diesel engine piston life is predicted according to the fracture mechanism of thermal fatigue and high temperature low cyclic fatigue. The experiments confirm that the equivalent strain range from Mises equivalent theory is related with the life as Manson Coffin formula. That is to say, this relation is extended to multiaxial stresses states and it is not affected by specimen shape and size, so that the results of one dimesional fatigue tests which are carried out in the laboratory can be used to multiaxial stresses states. Finally, this achievements are used to predict light 12V 180 engine piston life and the results show that in phase thermal fatigue model is most suitable.