An approach based on biological algorithm for three-dimensional shape optimisation with fracture strength constrains

This paper presents an innovative approach to shape optimisation of three-dimensional damage tolerant structures for residual static strength. In this approach, a new and simple method, which we termed FAST (Failure Analysis of Structures), for estimating the stress intensity factor for cracks at a notch, as well as an extension of the biological algorithm was employed to study the problem of optimisation with fracture strength as the design objective. This method is ideal for use in structural optimisation as accurate results are obtained without the need to explicitly model a crack, i.e. it is only necessary to model the uncracked structure. Methodology and software to automate damage tolerance calculations were developed using CAD and FAST software. The numerical examples illustrate the use of the damage tolerance optimisation software and prove that stress optimised geometries are not necessarily optimised for residual static strength or fatigue life.