含缩松缺陷的柴油机机身材料疲劳性能研究

Research on Fatigue Property of Material of Diesel Engine Body with Shrinkage Porosity

在含缩松缺陷的材料疲劳试验的基础上,对缩松结构的疲劳寿命的表征方法和疲劳寿命的预估进行了研究。综合考虑缺陷面积、位置和外加载荷的影响,使用扫描电镜分析计算得到了缩松缺陷的应力强度因子变化值。建立了应力强度因子和缺陷结构疲劳寿命之间的相互关系。结果表明,缩松的应力强度因子变化值可表征其疲劳寿命,二者成幂指数函数关系。反推得到了缩松缺陷的当量初始裂纹长度,建立了缺陷应力强度因子变化与当量初始裂纹之间的关系。进一步建立了基于应力强度因子变化的疲劳寿命预测方法,为含缩松缺陷结构的疲劳寿命预估提供依据。

On the basis of fatigue test of materials with shrinkage defects, the characterization method and the prediction method of fatigue life of constructs with shrinkage defects were researched. Considering the comprehensive influence from area size and position of defects and applied load, the stress intensity factor range value was obtained by using the analysis and compute of scanning electron microscope （SEM）. The relationships between stress intensity factor and fatigue life of structure with defects were established. The results show that the fatigue life can be characterized by stress intensity factor range, and both relationship is exponential function. The equivalent initial crack length with shrinkage defects was obtained by inverse method. The relationships between the change of the defect stress intensity factor and the equivalent initial crack length were established. A fatigue life prediction method based on stress intensity factor range was established further, which provides basis for the fatigue life prediction of structure with defects.