Abstract: Distribution of stress is important for fatigue evaluation and reliability design. Generally, Weibull distribution, Logarithmic normal distribution and truncated Gaussian distributions are used as stress distribution theory hypothesis. Practical calculation shows that it’s difficult to fit distribution of measured dynamic stress effectively with any of these distributions separately. Based on the characteristics of railway vehicle dynamic stress, a new distribution and a way for its fitting with statistics methods are presented. The distribution can fit dynamic stress distribution accurately. It has great significance for the fatigue life estimation of railway vehicles.

Key words: Weibull distribution　Lognormal distribution　Combination distribution　Parameter estimate　Chi-square test