轴承钢GCr15旋转弯曲超长寿命疲劳实验获得的应力-寿命(S-N)曲线数据分散性较大且呈连续下降趋势, 不能用台阶下降的S-N曲线描述. 断口分析表明, 在高应力幅区疲劳破坏主要起始于试样表面的加工划痕或夹杂物; 随着应力幅的降低, 疲劳破坏主要起始于试样内部的夹杂物. 内部破坏均带有鱼眼特征, 大部分的内部夹杂物周围带有颗粒亮区(GBF区). 夹杂物尺寸的较大分散程度和小尺寸夹杂物的簇集是引起 GCr15钢疲劳寿命分散性较大的因素. 使用推定的GBF区成长率能够定量分析夹杂物尺寸对疲劳寿命分散程度的影响.
Gigacycle fatigue properties of bearing steel GCr15, were investigated under cantilever-type rotary bending fatigue tests in an open environment at room temperature. S-N data obtained from fatigue test showed continuous gradual decline and large dispersion. These data could not be described by a step wise S-N curve. From the results of fractography, fatigue fracture mainly occurred at surface flaws or an inclusion in the region of high stress amplitude level, whereas it mainly occurred at a subsurface inclusion in the region of low stress amplitude level. Fish-eye marks were always observed around the subsurface inclusions on the fracture surface, and for most subsurface inclusions, a granular bright facet (GBF) area was observed in the vicinity around them. The experimental results were analyzed and showed that a larger scatter of inclusion size and clusters of smaller inclusion particles are key factors influencing the scatter of fatigue life. Influence of inclusion size on the dispersion of fatigue life can be quantitatively analyzed by using the estimated GBF growth rate from the S-N data.
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