Numerical prediction of fatigue crack propagation lifetime in adhesively bonded structures

In this short paper, a generalised numerical procedure using finite element (FE) analysis for prediction of the fatigue lifetime of adhesively bonded structures is proposed. The number of cycles to failure (Nf) is calculated by integrating a fatigue crack growth law between initial and final crack lengths. This crack growth law is formulated in terms of the strain energy release rate (SERR), which is determined, at any crack length, from an FE analysis. This complete process is implemented within the FE code, enabling automated calculation of the fatigue life for a given set of boundary conditions. This is a development of the approach outlined for single-lap joints [Int. J. Fract., 103 (2000) 41]. However, being fully implemented within an FE code it is not limited by the approximations of the simplified analytical expressions and furthermore can be applied to any structural configuration. The procedure was evaluated by application to a single-lap joint and good results were obtained in comparison with those using other methods. Furthermore, the use of the total SERR (GT) and mode I SERR (GI) as crack-propagation-controlling parameters are investigated and briefly discussed.