Data from: The interaction of fatigue cracks with a residual stress field using thermoelastic stress analysis and synchrotron x-ray diffraction experiments

This article presents an experimental study on the fatigue behaviour of cracks emanating from cold-expanded holes utilising thermoelastic stress analysis (TSA) and synchrotron x-ray diffraction (SXRD) techniques with the aim of resolving the long-standing ambiguity in the literature regarding potential relaxation, or modification, of beneficial compressive residual stresses as a result of fatigue crack propagation. The crack growth rates are found to be substantially lower as the crack tip moved through the residual stress zone induced by cold expansion. The TSA results demonstrated that the crack tip plastic zones were reduced in size by the presence of the residual compressive stresses induced by cold expansion. The crack tip plastic zones were found to be insignificant in size in comparison to the residual stress zone resulting from cold expansion, which implied that they were unlikely to have had a notable impact on the surrounding residual stresses induced by cold expansion. The residual stress distributions measured along the direction of crack growth, using SXRD, showed no signs of any significant stress relaxation or redistribution, which validates the conclusions drawn from the TSA data. Fractographic analysis qualitatively confirmed the influence on crack initiation of the residual stresses induced by the cold expansion. It was found that the application of single compressive overload caused a relaxation, or reduction in the residual stresses, which has wider implications for improving the fatigue life.本文针对源自冷胀孔的裂纹的疲劳行为开展实验研究，采用热弹性应力分析（thermoelastic stress analysis, TSA）与同步辐射X射线衍射（synchrotron x-ray diffraction, SXRD）技术，旨在解决学界长期存在的一项歧义：疲劳裂纹扩展是否会导致有益的残余压应力发生松弛或改变。研究发现，当裂纹尖端穿过冷胀诱导的残余应力区时，裂纹扩展速率显著降低。热弹性应力分析结果表明，冷胀诱导的残余压应力可缩小裂纹尖端塑性区的尺寸。相较于冷胀产生的残余应力区，裂纹尖端塑性区的尺寸极微小，这意味着其不大可能对冷胀诱导的周围残余应力产生显著影响。通过同步辐射X射线衍射测得的沿裂纹扩展方向的残余应力分布未出现明显应力松弛或重分布的迹象，这验证了热弹性应力分析数据所得出的结论。断口分析定性证实了冷胀诱导的残余应力对裂纹萌生的影响。单次压缩过载的施加会引发残余应力松弛或降低，该发现对提升构件疲劳寿命具有更广泛的应用价值。