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

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 Weibull, 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.