Experimental estimation of the probability distribution of fatigue crack growth lives.

This paper deals with a method to estimate numerically the reliability of fatigue sensitive structures with respect to the fatigue crack growth. A method is proposed to experimentally determine the Probability distribution functions of material parameters of the Paris law, da/dN=C(ΔK/K0)m, using stress-intensity-factor-controlled fatigue tests. The auto-correlation function of the resistance to fatigue crack growth, 1/C, is also estimated from the experimental data. The results of a high tensile strength steel 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 determine these functions. 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.