Fatigue Life Prediction Of Cylinder Head Under The Action Of Impulsive Loads

As one of the most complicated and most important components, cylinder head always works in a hyperthermal, high-pressured and highly corrosive environment, it mainly bears the thermal loads and impulsive loads of the cylinder. Fatigue life and reliability of the cylinder head directly work on the engine performance. Many earlier researches used to use statical loads instead of impulsive loads in, and this kind of method is proved unaccurate these days. This article focuses on the characteristic of impulsive load and fits the impulse load curve by using the pressure data of cylinder in order to predict cylinder head’s fatigue life and reliability under the effect of thermal-impulse loads.In this article, impulse load curve is fitted on the basis of cylinder pressure data, and three-dimension modle which includes cylinder head, cylinder body and bolts is founded according to the interactive surface modeling method. Thermal analysis and static analysis show that there are high temperature and thermal stress on the surface of flame-face nearby the out-gas channel and the boss in the out-gas channel. That’s because the cooling performance is inefficient in these two areas. By considering impulsive load’s characteristic and the request of following analysis, an analysis of strcture dynamic response is carried. The results of dynamics transient analysis show that structure starts to vibrate when the impulse load acts on it. The results of the analysis also include local load-time response data and many other dynamic response data. Several dangerous points are defined base on the dynamics transient analysis results. Fatigue life of the dangerous points are predicted according to the time-domain vibration fatigue life analysis mathod in order to predict the fatigue life of the structure.