Thermomechanical Fatigue Analysis of Diesel Engine Piston: Finite Element Simulation and Lifetime Prediction Technique

Abstract

Nowadays, piston aluminum–silicon alloys are widely used for high-powered engines due to their low specific gravity, high thermal conductivity, and good castability. However, under the conditions of increase of thermomechanical loads caused by the rise in the specific power output of diesel engines, and the operating temperatures of pistons go up to 0.8–0.9 of the melting temperature resulting in a significant reduction of the Al–Si alloy high-temperature strength. In this regard, to provide a required lifetime of pistons, it is necessary to more precisely simulate their thermal and stress-strain state, taking into account two-frequency loading and inelastic deformation. In this paper, a review of existing methods for the piston life estimation is carried out; a calculation method of the piston transient temperature and strain fields for engine start-stop cycles and one operating cycle at a nominal power mode is developed. The material constants in plasticity and creep models for the Al–12Si–Cu–Ni–Mg alloy are determined. On the basis of the obtained stabilized elastoplastic hysteresis loop, the piston low-cycle fatigue is estimated using the energy criterion. According to experimental data, the piston life is corrected taking into account high-frequency load.