冲击疲劳裂纹扩展的偏折现象

DEFLECTION BEHAVIORS OF CRACK GROWTH UNDER IMPACT FATIGUE LOADING

考察了在冲击疲劳载荷下低碳钢试样表面裂纹扩展的偏折现象，结果表明，冲击疲劳裂纹扩展的微观途径是以ｚｉｇｚａｇ 方式为主要特征的晶界、滑移带、邻近裂纹间的相互作用是引起裂纹扩展偏折的三个主要因素。晶界和滑移带的影响主要体现在短裂纹扩展阶段，邻近裂纹间相互作用的影响贯穿于整个冲击疲劳裂纹扩展阶段，尤其在疲劳后期的表现更为突出，它使得裂纹扩展以微裂纹连接的方式进行。相应于裂纹扩展微观途径的改变，裂纹扩展速率在短裂纹扩展阶段会出现波浪式变化。

An examination of deflection behaviors of crack growth on the surface of a low carbon steel under impact fatigue loading has been carried out.It is revealed that the main characteristic of micro\|path of crack growth is zig\|zag form.Fatigue crack deflection is usually caused by grain boundary(GB),slip band (SB) and crack\|crack interaction.GB and SB play an important role in early fatigue life.When a crack arrives at a GB or a SB,the propagation is obstructed and the crack tip branches.Then the crack select the direction of main slip system within the grain to propagate,and the crack deflection occures.The effect of crack\|crack interaction on crack growth behavior of impact fatigue take place during the whole fatigue life,particularly during the last life,when crack propagate in such a way as cracks linking-up.With changing of crack growth path,the growth rate changes in a wave form,particularly during early fatigue life.