Subsurface non defect fatigue crack origin and local plasticity exhaustion
Besides fish eye,subsurface non-defect fatigue crack origin (SNDFCO) in the matrix is another fatigue crack origin observed during very high cycle fatigue (VHCF).This paper provides some discussion on the phenomena and damage mechanisms from the recent investigations using four metallic materials with different microstructures.The results show that the strains in these materials in the VHCF regime were highly localized,especially in the multi-phase materials,where the local maximum strain can be eight times higher than the average strain value in the specimen.This high strain localization can lead to a fatigue damage or fatigue crack initiation at grain boundaries or twin boundaries by impingement cracking.High strain localization causes dislocation accumulation of very small strain during each cyclic loading and consequently the formation of local fine grain area and also increases the local hardness of the material.This can cause quasi-cleavage crack origin,and finally the formation of SNDFCO.The results in this paper indicate that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.
Very high cycle fatigue Local plasticity exhaustion Fatigue crack initiation stainless steels
Guocai Chai
Strategy Research,Sandvik Materials Technology,811 81 Sandviken,Sweden;Engneering Materials,Link(o)ping University,581 83 Link(o)ping,Sweden
国际会议
北京
英文
1-10
2013-06-16（万方平台首次上网日期，不代表论文的发表时间）