Compliance changes for a fatigue edge crack

Abstract

The evaluation of the compliance of specimens or structures with cracks has a fundamental significance in fatigue and fracture. Compliance-based experimental methods are widely utilised to evaluate crack length, residual stresses, crack tip opening loads and the effective stress intensity factor. These methods are often based on linear elastic solutions and, in the absence of analytical and numerical elasto-plastic solutions for propagating fatigue cracks, are largely reliant on empirical criteria and best practice approaches. This article utilises the simplified strip-yield model to investigate the change in compliance for an edge crack in a semi-infinite plate propagating under constant amplitude cyclic loading under plane stress conditions. The main objective of the work is to develop an analytical model for the influence of crack tip plasticity, crack face contact and plasticity-induced crack closure on compliance changes during the loading and unloading parts of a fatigue cycle. The present modelling results agree well with several highly accurate experimental studies published in the past, and allow the investigation of general tendencies in the compliance changes associated with applied fatigue loading. The latter can be very useful in the analysis of outcomes of experimental studies and development of new compliance-based techniques.