Finite element analysis of Thermo-mechanical stresses in diesel engines cylinder heads using a two-layer elastic-viscoplatic model with considering viscosity impacts

Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is finite element analysis of thermo-mechanical stresses in diesel engines cylinder heads using a two-layer elastic-viscoplasic model. The results of the thermo-mechanical analysis indicated that the maximum temperature and stress occurred in the valves bridge. The results of the finite element analysis correspond with the experimental tests, carried out by researchers, and illustrated the cylinder heads cracked in this region. The results of the thermo-mechanical analysis showed that when the engine is running the stress in the region is compressive caused by the thermal loading and combustion pressure. When the engine shut off the compressive stress turned into the tensile stress because of assembly loads. The valves bridge was under the cyclic tensile and compressive stress and then is under low cycle fatigue. Viscous strain was more than the plastic strain which is not negligible.

کلیدواژه ها:

thermo-mechanical fatigue ، finite element analysis ، cylinder heads and valves bridge cracks