A genetic algorithm applied to optimisation of patch repairs for cracked plates

The problem of the optimal shape of patch repairs for cracked plates is here examined by applying a biology-based method, known as the genetic algorithm. The optimum design procedure consists in evaluating the patch topology which maximises or minimises some mechanical properties of the repaired plate while keeping constant the total patched area (constrained optimisation problem). In the present paper, the best patch shape is determined by minimising the stress-intensity factor function (which is the adopted objective function). The proposed procedure is implemented in a finite element code, and some numerical simulations are carried out in order to assess the reliability of the method when applied to the case of a cracked plate under Mode I. For some configurations analysed, the stress-intensity factor can significantly be reduced by employing an optimal shape patch instead of a simple shape (square or rectangular) patch.