Evolutionary structural optimization for stress minimization problems by discrete thickness design

Stress minimization is a major aspect of structural optimization in a wide range of engineering designs. This paper presents a new evolutionary criter ion for the problems of variable thickness design whilst minimizing the max imum stress in a structure. On the basis of finite element analysis, a stre ss sensitivity number is derived to estimate the stress change in an elemen t due to varying the thickness of other elements. Following the evolutionar y optimization procedure, an optimal design with a minimum maximum stress i s achieved by gradually removing material from those elements, which have t he lowest stress sensitivity number or adding material onto those elements, which have the highest stress sensitivity number. The numerical examples p resented in this paper demonstrate the capacity of the proposed method for solving stress minimization problems. The results based on the stress crite rion are compared with traditional ones based on a stiffness criterion, and an optimization scheme based on the combination of both the stress minimiz ation and the stiffness maximization criteria is presented. (C) 2000 Elsevi er Science Ltd. All rights reserved.