LZ50钢断裂韧度的合理统计模型

REASONABLE STATISTICAL MODEL FOR RANDOM FRACTURE TOUGHNESS DATA OF LZ50 AXLE STEEL

试验研究了LZ50车轴钢的断裂韧度的合理统计模型。结果表明,LZ50钢是一种偏脆性的材料,应当严格控制铁道车辆车轴的制造表面质量。同时证实了现有正态分布模型不能合理描述试验数据。为此,通过比较三参数Weibull、两参数Weibull、正态、对数正态、极小值和极大值6种常用统计分布对试验数据的拟合优度、数理一致性和尾部安全性,说明了极小值分布是良好统计模型。建立了断裂韧度的极小值概率测定方法,测定了典型存活概率和置信度下的材料断裂韧度值。

Experimental study is carried out to study the reasonable statistical model for the random fracture toughness data of LZ50 axle steel. It is found that the material is brittle and a strict control of the manufacturing surface quality of railway vehicle axles is required. Meanwhile, it is shown that the existent normal distribution-based model is not useful to descibe the test data. The goodness-of-fit, consistence with failure physics, and safety of predictions in tail region are examined for six statistical distributions, i.e., three-parameter Weibull, two-parameter WeibuU, normal, lognormal, extreme minimum value, and extreme maximum value. Results show that the extreme minimum value distribution is a reasonable model. A probabilistic method is constructed on the basis of the model. The probabilistic values for the toughness are given under the typical survival probabilities and confidences.