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通过对疲劳过程中结构钢表面显微硬度测试结果的检验，证明了不同疲劳阶段的显微硬度测试值服从正态概率分布。依据损伤力学的基本理论建立了用显微硬度定义疲劳损伤变量的概率表达式，并应用于材料表面的损伤行为研究。分析表明，材料微观性能劣化是导致材料表面萌生显微裂纹的主要原因，而在微细观尺度上材料的损伤演化将呈现出显著的不均匀性和概率统计特征。并从疲劳裂纹萌生的无损检测角度指出了显微硬度方法是一种较方便和灵敏的表面测试技术。
Through testing the test results of the microhardness of the structural steel during the fatigue process, it is proved that the microhardness test values of different fatigue stages are subject to the normal probability distribution. According to the basic theory of damage mechanics, the probability expression of the fatigue damage variable defined by microhardness is established and applied to the study of the damage behavior of the material surface. The analysis shows that the deterioration of microscopic properties of the material is the main reason causing the micro-cracks on the surface of the material, while the damage evolution of the material at the micro-scale scales will show significant inhomogeneity and probability statistics. And from the perspective of non-destructive testing of fatigue crack initiation, it is pointed out that the microhardness method is a more convenient and sensitive surface testing technique.