铸件中显微孔洞特征及其对疲劳寿命影响的研究进展

铸件在铸造过程中会不可避免地产生显微孔洞,严重降低了铸件疲劳寿命。本文综述铸件中显微孔洞特征(尺寸、形状和空间分布)对疲劳寿命的影响,包括显微孔洞类型,孔洞特征分布规律,孔洞最大尺寸预测方法和含孔洞材料疲劳寿命预测方法;通过对疲劳寿命预测模型的回顾,发现目前含显微孔洞铸件疲劳寿命预测方法还不成熟;展望了显微孔洞特征对疲劳寿命影响的研究。提出未来应该依靠先进光源展开原位疲劳实验或者分子动力学仿真来研究孔洞疲劳失效微观机理,建立考虑不同显微孔洞特征参数,以及不同孔洞间相互影响的疲劳寿命定量预测模型。

Progress of Microporosity Characteristics in Casting and Their Effects on Fatigue Life

Microporosities in casting alloys cannot be avoided in the casting process. They will destroy the continuity of matrix, cause stress concentration, become the crack source of fatigue failure, and reduce the fatigue life of structure greatly. The current progress of microprosity characteristics (size, shape and position) in casting alloys and their effects on fatigue life is reviewed and prospected in this paper. Most of the microporosities are casting porosities with irregular shape and rough inner wall, and they have great influence on fatigue life of casting alloy. The size characteristic of microporosities well follows the lognormal distribution and the maximum size can be a typical feature to evaluate the fatigue life. And shape characteristics follows the Weibull distribution, however the position characteristics is complex. It is hard to observe the maximum size porosity in large-size casings, so the statistical methods are always used to predict them, and the generalized Pareto distribution method can get the best prediction results. At present, the fatigue life prediction methods of casings with microporosities are not complete and the failure mechanism of microporosity is not clear, the quantitative prediction model of fatigue life needs to be further studied, which considers different characteristic parameters of porosities and the interaction between different porosities under complex loading.