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The present paper describes a CAE analysis approach to evaluate the thermal-mechanical fatigue (TMF) of the cylinder head of a turbo charged GDI engine with integrated exhaust manifold. It allows design engineers to identify structural weakness at the early stage or to find the root cause of cylinder head TMF failures. At SAIC Motor, in test validation phase a newly developed engine must pass a strict durability test on test bed under thermal cycling conditions so that the durability characteristics can be evaluated. The accelerated dynamometer test is so designed that it gives equivalent cumulative damage as what would occur in the field. The duty cycle includes rated speed full load, rated speed motored and idle speed conditions. A transient none-linear finite element method is used to calculate the plastic deformation and thermal mechanical behaviors of the cylinder head assembly during thermal cycling.

The present paper describes a CAE analysis approach to evaluate the design of exhaust manifold of a turbo charged gasoline engine. It allows design engineers to identify structural weakness at the early stage or to find the root cause of exhaust manifold failures. A transient none-linear finite element method is used to calculate the plastic deformation and thermal mechanical behaviors of the exhaust manifold assembly during thermal shock cycles, which include rated speed full load, rated speed motored and idle speed conditions. A transient heat transfer simulation is performed to provide thermal boundary conditions for the nonlinear stress/strain analysis. The finite element model includes a part of cylinder head, exhaust manifold, gaskets, turbo charger housing, catalytic converter, brackets, bolts and nuts. The results show that plastic deformation is the main cause of manifold cracking and the manifold flange distortion causes the exhaust leakage.