Simulation of fatigue behaviour in fusion welded 2024-T351

A model has been developed to predict short crack fatigue life in the fusion zone of Metal Inert Gas (MIG) welded 2024-T351, based on the observed propensity for complex, multiple cracking processes in this region. To initiate cracks, a Monte-Carlo method has been used, based on the probability of initiation at interdendritic defects derived from the experimental observations. Short crack propagation simulation has been achieved via a microstructurally sensitive approach using continuous dislocation distribution methods. Different geometrical conditions to define crack shielding or crack coalescence have also been identified, along with a first order estimate of crack closure effects and associated influences of residual stress on crack growth. In the regime of specific interest here (crack growth to 1mm total length), good correlation is shown between measured and predicted fatigue performance.