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Durability assessments of modern engines often require accurate modeling of thermal stresses in critical regions such as cylinder head firedecks under severe cyclic thermal loading conditions. A new methodology has been developed and experimentally validated in which transient temperature distributions on cylinder head, crankcase and other components are determined using a Conjugate Heat Transfer (CHT) CFD model and a thermal finite element analysis solution. In the first stage, cycle-averaged gas side boundary conditions are calculated from heat transfer modeling in a transient in-cylinder simulation. In the second stage, a steady-state CHT-CFD analysis of the full engine block is performed. Volume temperatures and surface heat transfer data are subsequently transferred to a thermal finite element model and steady state solutions are obtained which are validated against CFD and experimental results.

Crankshaft is usually hardened on its main and pin journal surfaces and fillets. The subsurface area right underneath the hardened zone is therefore the most vulnerable area (if the case depth is not deep enough). During the bending tests fatigue failures have been occurred on the subsurface sites of the pin journal fillets. Finite element method can be employed to simulate the bending tests. Using the stress data measured on pin fillet surface, the fatigue behavior of its subsurface can be characterized. The results of this research can be used to predict fatigue failure of crankshaft subsurface under engine operating condition. In this research, the finite element model is validated by comparing the stresses on pin surface with the bending tests. Excellent correlation has been achieved between finite element modeling and the test results. Then, the stresses along the case depth are calculated and the curve of stress vs. case depth is plotted.