Low Cycle Fatigue Simulation of Valve Bridge Region in Cylinder Head Based on Critical Plane Model

The reason of this study is low cycle failure of cast iron cylinder head during the E5 standard durability test. The goal of the present investigation is durability test simulation and low cycle fatigue life evaluation of cast iron cylinder head. With uncouple structural analysis, preloads, thermal and mechanical load and boundary conditions are prescribed to finite element model of the cylinder head. To cover the durability test, the analysis steps repeated at five crack speed, 750, 1650, 2075, 2350 and 2600 rpm. The cylinder head is subjected to cyclic multi-axial non-proportional variable amplitude loads. In fatigue analysis, critical plane model with cumulative damage theory is applied to predict fatigue life. A general scripting is developed and validated to calculate fatigue life. The results show that the failure of critical cylinder head is the type of low cycle fatigue. The valve bridge region, where high temperature exists during operation of the engine, is the critical area in cast iron cylinder head in fatigue analysis approach. The simulation results are in accordance with the results of durability test.