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为了提高随机疲劳长裂纹扩展率预测精度,基于Forman方程,发展了随机疲劳长裂纹扩展概率模型及其参数测定方法,考虑数据分散性规律和试样数量对概率评价的影响,得到了包含存活概率曲线、置信度曲线和两者融合曲线在内的长裂纹扩展率关系曲线,在给定应力强度因子范围内,裂纹扩展率服从对数正态分布条件下,采用线性回归和极大似然法测定模型参数。对铁道车辆LZ50车轴钢裂纹扩展数据分析表明,该模型反映了材料断裂韧度对长裂纹扩展率的影响,克服了基于Paris-Er-dogan方程的概率模型在高应力强度因子范围预测偏于危险的缺陷,验证了该模型的合理性。
In order to improve the prediction accuracy of the random fatigue crack propagation rate, based on the Forman equation, a model of random fatigue crack propagation probability and its parameter determination were developed. By considering the data dispersion law and the influence of the number of samples on the probability evaluation, Curves, confidence curves and long-term crack growth rate curves of the two fusion curves. Under a given stress intensity factor range, the crack growth rate obeys the logarithm normal distribution conditions, using linear regression and maximum likelihood method Determination of model parameters. The analysis of crack growth data of LZ50 axle steel for railway vehicles shows that the model reflects the effect of material fracture toughness on the rate of long crack propagation and overcomes the fact that the probability model based on the Paris-Er-dogan equation is predominantly dangerous in the high stress intensity range The defects of the model verify the rationality of the model.