FGH95粉末高温合金裂纹闭合效应及裂纹扩展特性研究

摘要

Plasticity‐induced crack closure effect of compact tension (CT) specimen of FGH95 powder metallurgy superalloy was investigated by using finite element method . The stress distribution in crack surface was analyzed .The effects of three principal factors ,the constitutive model ,mesh densi‐ty and stress ratio ,on the crack closure behavior were studied ,to further establish crack propagation life analysis model of CT specimens with considering crack closure ,and to predict life .The results show that crack closure in elastic‐perfectly plastic constitutive model appears more sensitive to grid cell than that in multi‐linear kinematic hardening constitutive model .Crack closure trends to be stable with the number of crack tip elements in the plastic zone reach to 20 .Crack closure decreases with the increase of stress ratio ,and disappears as stress ratio reaches to 0 .5 .The revised life prediction model shows higher prediction accuracy than traditional model for CT specimens .%采用有限元方法研究FGH95粉末高温合金标准紧凑拉伸（CT ）试样的塑性诱发裂纹闭合效应，分析裂纹面上的应力分布，并考察本构模型，网格密度及应力比对裂纹闭合效应的影响，进而建立考虑裂纹闭合效应下CT试样裂纹扩展寿命分析模型，并进行寿命预测。结果表明：理想弹塑性模型下的裂纹闭合效应对网格单元的敏感性比多线性随动强化模型高；裂纹尖端塑性区内网格数达到20时，裂纹闭合趋于稳定；应力比增加裂纹闭合效应减小，当应力比达到0．5时裂纹闭合效应消失。修正的寿命预测模型对CT试样的预测精度比传统模型更高。