Improvement in the Thermal Elasto-Plastic FEM Model Applied to Exhaust Manifold

An exhaust manifold undergoing nonlinear thermal deformation was analyzed, using the Thermal Elasto-Plastic finite element model. The creep strain and the temperature-dependent apparent strain as well as nonlinear stress-strain relation are considered in the model for improving the computational accuracy. The stress-strain relation curve was formulated by means of a multi- regression analysis on the experimental data. Three dimensional solid and shell isoparametric elements were used to discretized the geometry of exhaust manifold. The boundary nodes adjacent to the interface of the cylinder head/exhaust manifold are supported by three-way springs allowing those nodes to be moved freely in the three-dimensional coordinates. A number of experiments on the exhaust manifold were also carried out to justify the validity of the finite element model. Comparison of the model study with the experimental data shows an excellent agreement in both the temperature and the strain distributions confirming that deformation due to creep strain cannot be neglected in the exhaust manifold thermal deformation simulation.