AN IMPROVED APPROACH FOR DETERMINING THE OPTIMAL ORIENTATION OF ORTHOTROPIC MATERIAL

Several approaches for determining the optimal orientation in the topo logical optimization process are discussed in this paper. It is shown that the use of strain based method may give an even worse result than the case in which the discrete orientational variables are fixed in t he optimization process, because strong couplings exist among the orie ntational variables when the strain field is used. The stress field is less sensitive than the strain field with respect to the variations o f the orientational variables. Therefore, the coupling between the ori entational variables is relatively weak when the stress field is used. This explains why the stress based approaches (e.g. Suzuki and Kikuch i 1991; Diaz and Bendsoe 1992) are more efficient than the strain base d method. This kind of approach will be generalized to deal with more general optimization problems. It will be shown that the new approach can not only obtain the best result for the problem as compared to the other methods, but also has the generality for various optimization p roblems. Several examples will be presented to support the above state ments.