Design for Minimum Stress Concentration by Finite Elements and Linear Programming

ABSTRACT The problem of design for minimum stress concentration is highly nonlinear and must be solved iteratively. Each iteration (redesign) involves three steps: an analysis of the stresses for a design, a sensitivity analysis corresponding to possible changes in this design, and the decision of redesign. For stress analysis, the FEM is a unified approach which is applied in the present paper to axisymmetric solids that are also subjected to nonaxisymmetric loads. The decision of redesign is a linear programming problem and can thus be solved with the Simplex algorithm. The introduction of move-limits to the formulation is of major importance. The optimization approach is described in general, but most of the paper concentrates on a specific example and shows optimum shapes of a shoulder fillet in a stepped bar. Loads are bending, tension, or torsion, and the stress concentrations are considerably reduced.