Thermal Analysis of Coupled Thermal Stress and Fatigue Life of a Diesel Engine Piston

Using PERMAS software, the temperature and thermal-mechanical coupled stress of a piston under calibration conditions were calculated using the finite element model for the piston skirt profile, the piston combustion chamber and the inner cooling oil path. The fatigue life of the piston was analyzed, and the changes in the piston ring groove and the outer diameter of the piston were measured. The results show that the high temperature region of the piston is mainly distributed at the top of the piston and that the maximum temperature is approximately 301 degrees C, which is within the allowable range of the piston material; the average surface temperature of the first ring groove is 194 degrees C, which is lower than the lubricating oil coking temperature. When the piston is coupled to a heat engine, the piston is tilted toward the main thrust surface, and the main thrust surface is larger, approximately 44 N / mm(2). The maximum stress value of the piston pin seat surface is mainly distributed in the back pin hole, and the stress values are within the allowable range. The lowest fatigue life of the piston occurs at the bottom part of the combustion chamber and the combustion chamber roar mouth, which have theoretical fatigue lives of 6.9 and 7.7, respectively. After 800 hours of thermal shock testing, the piston ring groove, pin hole, piston ring groove bottom diameter and the piston show little change in dimension. All of these piston elements meet the fatigue life requirements.