Fatigue Crack Initiation Potential from Defects in terms of Local Stress Analysis

查看全文 作　　者：ZHU [1,2]Mingliang;XUAN [1,2]Fuzhen

机构地区：[1]Key Laboratory of Pressure Systems and Safety, Ministry of Education, East China University of Science and Technology;[2]School of Mechanical and Power Engineering, East China University of Science and Technology

出　　处：《Chinese Journal of Mechanical Engineering》索引2014年第27卷第3期,共8页

基　　金：Supported by National Natural Science Foundation of China(Grant No.51205131);Shanghai Provincial Natural Science Foundation of China(Grant No.12ZR1442900);Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120074120010) 摘　　要：The competition of surface and subsurface crack initiation induced failure is critical to understand very high cycle fatigue(VHCF)behavior,which necessitates the elucidation of the underlying mechanisms for the transition of crack initiation from surface to interior defects.Crack initiation potential in materials containing defects is investigated numerically by focusing on defect types,size,shape,location,and residual stress influences.Results show that the crack initiation potency is higher in case of serious property mismatching between matrix and defects,and higher strength materials are more sensitive to soft inclusions(elastic modulus lower than the matrix).The stress localization around inclusions are correlated to interior crack initiation mechanisms in the VHCF regime such as inclusion-matrix debonding at soft inclusions and inclusion-cracking for hard inclusions(elastic modulus higher than the matrix).It is easier to emanate cracks from the subsurface pores with the depth 0.7 times as large as their diameter.There exists an inclusion size independent region for crack incubation,outside which crack initiation will transfer from the subsurface soft inclusion to the interior larger one.As for elliptical inclusions,reducing the short-axis length can decrease the crack nucleation potential and promote the interior crack formation,whereas the long-axis length controls the site of peak stress concentration.The compressive residual stress at surface is helpful to shift crack initiation from surface to interior inclusions.Some relaxation of residual stress can not change the inherent crack initiation from interior inclusions in the VHCF regime.The work reveals the crack initiation potential and the transition among various defects under the influences of both intrinsic and extrinsic factors in the VHCF regime,and is helpful to understand the failure mechanism of materials containing defects under long-term cyclic loadings. 关键词：疲劳裂纹萌生局部应力分析内部缺陷内部裂纹萌生计算弹性模量夹杂物长度控制

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Fatigue Crack Initiation Potential from Defects in terms of Local Stress Analysis

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