Parameter free shape optimization of shell structures using stress response

During optimisation, the parameter free approach provides much design freedom for a limited modeling effort since data of the finite element model are used as design variables. Stress results are, however, very sensitive to the local shape changes that can occur during parameter free optimisation. When stress results are used as response function, these irregular results can complicate the optimisation. As a solution, the Kreisselmeier-Steinhauser function for the stresses is introduced as a response function. In this function, the local stress results are aggregated to obtain a global measure of stress in a structure which can be used as an objective to reduce the overall stress in the structure or as a constraint to limit the stress in the structure to a maximum allowable value.

The resulting structures are smooth and material efficient. Several examples are presented in this paper to illustrate the use of the parameter free approach in combination with the stress response function.