The statistical aspect of fatigue of materials

The phenomenon, which is usually described as ‘fatigue’ of materials, but for which the term ‘progressive failure’ would be more adequate, is the expression, on a macroscopic scale, of the progressive destruction of the cohesive bonds as a result of the repetitive action of an external load. It has the typical features of a mass phenomenon; both the cohesive bonds and the load repetitions are collectives in a statistical sense (Mises 1931). By applying the fundamental rules of the theory of probability many of the experimentally established relations between the principal variables can be theoretically deduced from the purely formal assumption of the existence of a statistical distribution function of the separation-strength of cohesive bonds.