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为实现在全应力强度因子范围合理进行结构安全性分析,提出了概全门槛值和断裂韧度的随机疲劳长裂纹扩展率的新概率模型。考虑了平均应力效应,以给定应力强度因子下裂纹扩展率服从对数正态分布为基础,考虑数据分散性规律和试样数量对概率评价的影响,将存活概率和置信度相融合,由线性回归结合极大似然原理确定概率模型的参数。通过对铁道车辆LZ50车轴钢试验数据的分析表明,模型从数学上良好描述了疲劳长裂纹从裂纹启裂到瞬时断裂的整个随机过程,比较Paris、Elber和Forman模型拟合试验数据表明,该模型相关系数最大,拟合效果最好。
In order to achieve reasonable structural safety analysis in the range of full stress intensity factor, a new probability model of random fatigue long crack propagation rate with generalized threshold value and fracture toughness was proposed. Considering the average stress effect, taking the crack growth rate obeying the logarithm normal distribution under a given stress intensity factor as the basis, taking into account the influence of the data dispersion law and the number of samples on the probability evaluation, the survival probability and the confidence are merged from Linear regression combines the maximum likelihood principle to determine the parameters of the probability model. The analysis of the test data of the LZ50 axle steel for railway vehicles shows that the model mathematically perfectly describes the entire random process of fatigue crack initiation from crack initiation to instantaneous failure. Comparing with the Paris, Elber and Forman model fitting test data, this model The correlation coefficient is the largest and the fitting effect is the best.