Structural optimisation with fracture strength constraints

When considering the problem of shape optimisation with residual strength constraints it was recently found [1] that there were cases when the optimal shape for a body without an initial flaw was not the same as the optimal solution for a body with an initial flaw. It was also found that for the optimal case the stress intensity factors, for same length cracks emanating at right angles to any arbitrary point around the hole, were approximately constant along most of its circumference. As a result of this finding the present paper presents a new biological algorithm for the optimal design of structural components with fracture, i.e. residual strength, constraints. This approach is illustrated by considering the problem of an optimum cut-out geometry for a rectangular plate subjected to a bi-axial stress field and the problem of the shape optimisation of a fillet with residual strength constraints.