Two new practical models for estimation reliabilitybased fatigue strength of composites

ABSTRACT: This paper outlines two new practical models to evaluate fatigue residual strength and the overall range of life for reliability-based design. A new fatigue-driven residual strength surface model with four parameters is derived based on an expression form of power function product to estimate the parameters more easily and expediently, and logically characterize the physical characteristics and the phenomenological quantitative laws. A more appropriate S–N curve formulation with four parameters is presented to cover overall life range. By means of the likelihood principle and the linear regression, the parameter determination formulae of these two models are respectively established to deal with the test data effectively and easily. The probability distributions for these two models are also given. Finally, the models are applied to two sets of experimental data, demonstrating the practical and effective use of the proposed models. It is shown from these examples that fatigue-driven residual strength and the overall range of life can be obtained realistically according to the small sample test data using the new formulae