Design of structures for optimal static strength using ESO

This paper presents a modified evolutionary structural optimisation (ESO) algorithm for optimal design of damage tolerant structures. The proposed ESO algorithm uses fracture strength as the design objective. The formulation outlined here can be used for shape optimisation of structures and allows for cracks to be located along the entire structural boundary. In this work we use an approximate method for evaluating the stress intensity factors associated with the cracks. This extended ESO algorithm is illustrated using the problem of the optimal shape design of a `cutout' in a rectangular plate under biaxial loading and the design of a shoulder fillet under uniaxial tension. It is found that this method reduced the maximum stress intensity factor for the optimum shape and produced a near uniform level of fracture criticality around the boundary. It is also shown that the shapes optimised for stress and fracture strength may differ. This highlights the need to explicitly include fracture parameters in the design objective function. The results agreed well with those reported in the literature using a biological method.