42CrMo4钢疲劳裂纹扩展时的残余应力及其变化

RESIDUAL STRESS AND ITS VARIATION WITH FATIGUE CRACKRPOPAGATION OF 42CrMo4 STEEL

对４２ＣｒＭｏ４钢调员试样疲劳裂纹扩展时的表面残余应力测定表明，在裂纹尖端前方和裂纹两侧一定范围生成残余压应力，裂纹尖端处压应力最大。随着裂纹的扩展压应力范围增大，最大压应力增加，表明残余应力始终处于一动态再分布过程中，与裂纹尖端区域的塑性变形直接相联系。裂纹扩展时残余应力的真实分布状态，按理想模型已不能作出圆满描述。由于裂纹尖端塑性变形区较小，选用合适的Ｘ线光栅孔径测得的残余应力较为真实。

The quenched and tempered 42CrMo4 steel was used to investigate surface residual stress and its variationswith fatigue crack propagtion.The rasults show that there were compressive residual stresses in the crack tip and the twosides of crack within a certain region,and the maximum compressive residual stress occurred at the crack tip.The area ofcopressive residual stress and the maximum values of compressive residual stress were increasing with the crack growth.The residual stress was always in course of a dynamic redistribution. This phenomenon was directly related to the plasticdeformation at the crack tip. The real distribution state of the residual sirers can not be described by an ided model.Forthe case of the smaller plastic zone at the fatigue crack tip,a proper X-ray grating aperture can be selected to measure thered state of residual stress.