Crack propagation under variable amplitude loading

Abstract

Experience shows that a damage induced by a given cycle is dependent on the loading history. In this regard, the objective of this paper is to study and describe the phenomenology of the loading history on crack propagation. Different loading configuration has been considered for fatigue crack propagation of XC38 steel; overload cycles followed by underload and vice versa were considered during propagation. Measure of crack opening has been made using compliance method. It is shown that the main parameters which cause retardation are the residual compressive stresses and the crack closure. The finite element modeling is used to calculate the evolution of residual stress profiles before and after application of the overload-underload cycle. It corroborates the hypotheses on the mechanisms behind, including those proposed on the residual stresses at the crack tip.

Influence of load interaction and hydrogen on fatigue crack growth behavior in steel pipelines under mean load pressure fluctuations

“…There is no consensus on the effect of mean load on crack growth generally. Some experimental works have shown that mean load with load sequence of underload + overload + minor cycles (Type II mean load) causes retardation of crack growth, 24–28 while other research works have shown an opposite trend 29,30 …”

An experimental investigation on the fatigue crack growth behaviour of AISI/SAE 1045 under load sequences containing underloads

“…The ability to reduce the retardation due to overloads is another widely investigated effect of underloads . The majority of these investigations stated that the reduction of retardation is more significant, if the underload or the underload block is applied after the overload(s).…”