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鉴于非金属夹杂诱发Cr-Ni-W高强度钢超长寿命(>107周次)内部疲劳失效的行为,使用4种统计方法(statistics of extreme values,SEV;generalized extreme values,GEV;generalized Pareto distribution,GPD;exponential generalized Pareto distribution,EXPGPD)对其特征夹杂尺寸进行了评估,并基于Murakami方程预测了其超长寿命疲劳强度。结果表明,SEV和EXPGPD预测的夹杂尺寸会随钢体积的增加而无限增大,而GPD和GEV预测的尺寸会逐渐增加并趋于一定值,其中EXPGPD和GPD分别给出了其上下限值。与实验寿命等于108的结果相比较,基于EXPGPD方法的疲劳强度预测结果偏低,而其它方法的预测结果均偏高;从抗疲劳断裂角度出发,对于体积大于1 mm3的Cr-Ni-W钢而言,采用基于EXPGPD方法的夹杂尺寸评估和强度预测是适合的。
In view of the internal fatigue failure behavior of Cr-Ni-W high-strength steels induced by non-metallic inclusions over a long period (> 107 weeks), four statistical methods (statistics of extreme values, SEV; generalized Pareto distribution , GPD (exponential generalized Pareto distribution, EXPGPD) were used to evaluate the characteristic inclusions, and their fatigue life was predicted based on the Murakami equation. The results show that the predicted inclusions of SEV and EXPGPD will increase indefinitely with the increase of the volume of steel, while the predicted sizes of GPD and GEV will gradually increase and tend to a certain value. The upper and lower limits of EXPGPD and GPD are given respectively. Compared with the results of experimental life equal to 108, the prediction results of fatigue strength based on EXPGPD method are low, while the prediction results of other methods are high. For the fatigue resistance fracture, for the Cr-Ni-W steel with the volume larger than 1 mm3 , It is appropriate to use inclusion size assessment and intensity prediction based on the EXPGPD method.