A framework for accurately modelling fatigue crack growth in ductile crystalline solids was necessarily multiscale. The creation of new free surface occurs at the atomistic scale, where the material’s cohesive strength was controlled by the local chemistry. On the other hand, significant dissipation during fatigue crack growth takes place at a size scale that could be modelled appropriately by conventional continuum mechanics. The intermediate size scale where the discreteness of dislocations comes into play was the main origin of the hysteresis needed for fatigue and of the high stresses required for atomistic separation to take place. Attention was focussed upon recent developments which permit analyses of fatigue crack growth involving the direct coupling of disparate size scales. Although no analyses were carried out directly coupling size scales from the atomic to the conventional continuum, the ingredients to do so were in place. Background was provided which illustrated the key role played by the intermediate discrete dislocation size-scale and the steps that were taken to permit direct size-scale coupling were reviewed. The prospects and modelling needs for further developments were also considered.

Hybrid Discrete Dislocation Models for Fatigue Crack Growth. W.A.Curtin, V.S.Deshpande, A.Needleman, E.Van der Giessen, M.Wallin: International Journal of Fatigue, 2010, 32[9], 1511-20