EXPLOITING DESIGN LENGTH SCALES IN STRUCTURAL OPTIMIZATION

Many structural optimization methods use geometric length scales as we ll as artificially imposed lengths such as finite element dimensions. One considers functions defined over these dimensions in characterizin g and solving the problem. The natural length scales involved in the p roposed design change are generally overlooked. When one proposes an o ptimization based on change of certain panels in a sheet metal structu re, for instance, it might be helpful to use the dimensions of the red esign areas as characteristic lengths. In the present study, a Rayleig h-Ritz approach is taken where the responses of a structure to pseudo- loads (acting only over specified design-change regions) are employed as basis vectors. It is found that convergence of the optimization pro cess is improved. The method is demonstrated for moderate-sized proble ms, and as with other modal methods, should become even more helpful f or large problems. The new complexity involved is the requirement for a type of problem-dependent linking, in parallel with the conventional design variable linking. This can be automated. (C) 1997 by John Wile y & Sons, Ltd.