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.

Keywords

• crack
• overload
• underload
• plastic zone
• residual stress