机械加工残余应力对调质40CrNiMo钢疲劳特性的影响

Effect of Residual Stress Induced by Machiningon Fatigue Property of 40CrNiMo Steel

机械加工在试样表面造成的残余压应力σｒ，若分布很浅（０．０１～０．０２ｍｍ），疲劳过程中σｒ极易衰减，从而对疲劳极限光明显影响，疲劳极限取决于裂纹萌生寿命。若σｒ分布较深（０．０５～０．０７ｍｍ），在疲劳过程中最外层应力衰减后，次外层残余应力重新分布，这种残余应力与缺口应力场综合作用，有可能在缺口根部产生非扩展裂纹，从而使疲劳极限取决于裂纹的止裂条件，提高了缺口试样疲劳极限。

This paper presents the effect ofresidual compressive stress incurred by machiningon fatigue property of 40CrNiMo steel.For shallowdepth (0.of-0'02 mm)of residual compressivestress layer,the residual stress has shown no evident effect on fatigue limit due to the quick attenuation of residual stress under fatigue loading,in thiscase,the fatigue limit is decided by the crack initiation.For deeper layer(0.05～0.07 mm) of residual compressive stress,under cyclic loading,theresidual stress is redistributed in secondary outerlayer,the comprehensive effect of residual stressand the stress of specimen notch may lead to thenon-propagating crack in the root of notch. In thiscase, the fatigue limit is decided by the conditionsof crack arrest and the fatigue limit is increased.