Experimental Estimation of Probability Distribution of Fatigue Crack Growth Lives.

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This research proposes a method to estimate numerically the reliability of fatigue sensitive structures with respect to fatigue crack growth. A method is proposed to experimentally determine the probability distribution functions of material parameters of the Paris law, da/dN=C (DELTAK/K_0)^m, using stress-intensity -factor-controlled fatigue tests. The auto-correlation function of the resistance to fafigue crack growth, 1/C, is also estimated from the experimental data.The results of two high tensile strength steels, (BS4360 and L36E). show that the distribution of the parameter, m, is approximately normal and that of 1/C is a 3-parameter Weibull. The merit of the proposed method is that only a small number of tests are required to estimate the probability distribution function of fatigue crack growth life. The probability distribution of the fatigue crack length after a given number of load cycles or the number of load cycles for a crack to reach a given length can be estimated by simulation of non- Gaussian random processes with these functions.