Separation of Notches and their Shape-Optimization in a Thermally Loaded Vessel Using the CAO-Method

摘要

Shape optimization of highly loaded technical components often means to avoid stress concentration in notches like shoulders, fillets etc. This can be achieved by using the computer program CAO (Computer Aided Optimization), that has been developed at Forschungszentrum Karlsruhe. The basic design rule of CAO is the axiom of uniform stress which is adopted from biological load carriers like trees, which use adaptive growth to minimize stress concentrations on their surface. Analogous technical structures "grow" by CAO at zones with high stresses. This growth and with it the optimized design is depending on the stress distribution caused by the loading conditions. The CAO method was applied to optimize the shape of the transition between a vessel wall and the holding units of a thermally loaded vessel. Finite element analyses show, that during heating the stress maximum is shifted locally within the fillet between the vessel wall and the holding units. The fact that the position of the stress maximum is not stationary causes a special problem in optimization. The shape optimized for a certain temperature gradient may cause even larger stress concentrations in case of another gradient. This problem was solved by a spatial separation of the locations of maximum stresses.