Characteristics of Empirical Cumulative Distribution Function of Grown Crack Size under Different Maximum Fatigue Loads in AZ31

摘要

The aim of this paper is to find the characteristics of the empirical cumulative distribution function of grown crack size depending on the maximum fatigue loads in AZ31 magnesium alloy. The grown crack data required to estimate the empirical cumulative distribution function and to analyze its probabilistic characteristic are obtained from the fatigue crack propagation experiments. These experiments are carried out on the duplicated compact tension specimens in three different maximum fatigue loads. The 3-parameter Weibull distribution is used to estimate the empirical cumulative distribution function. The slope and the tails of the empirical cumulative distribution function are affected by maximum fatigue load and fatigue crack propagation cycle. The result shows that the tail in the range below 10 % and above 90 % of the empirical cumulative distribution function is longer in case of larger maximum fatigue load and in stage close to failure. It is also found that the nearer a failure, the larger the slope of the empirical cumulative distribution function to the axis of grown crack size. The failure life can be short in larger maximum fatigue load condition.