SHAPE OPTIMAL-DESIGN OF AN ENGINE EXHAUST MANIFOLD

An engine exhaust manifold made of cast iron cracks during thermal sho ck testing. The test process is simulated by finite element analysis. The manifold is formulated as a linear heat transfer and thermoelastic ity problem in a variational form. Analytical expressions for shape de sign sensitivities of general three-dimensional problems are presented , using the material derivative approach. A hybrid approach is describ ed and used during the optimization process. This approach takes advan tage of the direct and the adjoint variable methods and is the most ef ficient in calculating the sensitivity of the structural responses. Af ter the finite element model is verified by comparing the results with those from testing, the engine exhaust manifold is optimized with res pect to its geometry.