The porosity of the material produced by additive manufacturing technology gives rise to a notable dispersion of the crack initiation life in the very-high-cycle fatigue regime. The crack initiation life in the very high cycle fatigue regime can be divided into the initial crack initiation life and early microcrack growth life. This paper proposed a model considering the effect of pore morphology and location to predict the initial crack initiation life. The average local stress in a grain near the pore is modified by considering the relationship between pore roundness, inclination, position, and stress concentration factor. The growth life of early microcrack is determined by integrating empirical formulas based on dislocation theory. Subsequently, the probability distribution of crack initiation life is obtained, which is in good agreement with the experimental results. The competition factor is proposed to quantitatively evaluate the tendency of crack initiation from the surface or the interior, taking into account the influence of local average stress and grain size. The predicted load corresponding to the shift in crack initiation position is in accordance with the experimental results.

中文翻译：

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基于孔隙的超高周疲劳中裂纹萌生寿命预测


增材制造技术生产的材料的孔隙率导致裂纹萌生寿命在极高周疲劳状态下显着分散。极高周疲劳状态下的裂纹萌生寿命可分为初始裂纹萌生寿命和早期微裂纹扩展寿命。本文提出了一种考虑孔隙形态和位置影响的模型，用于预测初始裂纹萌生寿命。通过考虑孔隙圆度、倾斜度、位置和应力集中因子之间的关系，可以修改孔隙附近颗粒中的平均局部应力。早期微裂纹的生长寿命是通过整合基于位错理论的经验公式来确定的。随后，得到了裂纹萌生寿命的概率分布，与实验结果吻合较好。考虑到局部平均应力和晶粒尺寸的影响，提出了竞争因子来定量评估从表面或内部产生裂纹的趋势。与裂纹起裂位置偏移相对应的预测载荷与实验结果一致。