Thermal-mechanical Coupling Simulation Analysis And Fatigue Life Prediction Of A Steel Piston

The internal combustion engine is currently the world’s most widely usedthermodynamic device which makes the fuel burning in the combustion chamber andreleasing heat energy. It’s an industrial revolution product that makes the heat energy of thehigh temperature and pressure fuel gas itself transferred by a crank rod and then turned intomechanical energy through the crank to generate power. As a part working in the most severeenvironment of the internal combustion engine, piston is subjected high intensity mechanicalloads and heat loads, fatigue design of the piston is directly related to the internal combustionengine’s economy, reliability and service life, so it’s necessary to analysis thethermal-mechanical coupling of the piston and predict the piston’s fatigue life.This article studied mechanical stress, thermal stress and thermal-mechanical couplingunder the multiaxial stresses for the piston based on Siemens UG NX software,pre-processing ANSA software, finite element analysis software ANSYS, as well as fatiguelife NCODE-DESIGNLIFE processing software, analyzing it’s deformation and thedistribution of stress and strain field. In addition, combining transient dynamics analysis onthermal-mechanical coupled to predict the piston’s multiaxial fatigue life,at the same time,also studied the low cycle thermal fatigue life of the piston. The main content of the article isshown below:(1) Using Siemens UG software to establish a quarter of the model for the piston, thenimport the model to ANSA software for meshing. In order to obtain accurate results, deal withchamfer, round, small holes and the first ring groove parts for grids refining processing.(2) According to the empirical formula and semi-empirical formula to obtain the thirdtype of thermal boundary conditions of piston. Applied the boundary conditions on the finiteelement model of piston, calculating it’s steady temperature field with ANSYS software, inthis way can we get the piston temperature field, heat flux and temperature gradient distribution for piston.(3) On the basis of the calculated temperature field, further do the simulation to calculatethe thermal stress distribution and thermal strain distribution at the peak breakout pressure ofthe piston. Finally, combining with dynamics, analyzed the thermal-mechanical coupling astransient of the piston to obtain piston’s deformation and distribution of stress and strain.(4) According to the analysis results above, use critical plane method and the E-N curveof the piston’s material, predict multiaxial fatigue life of the piston in a professional fatiguesimulation software NCODE-DESIGNLIFE; at the same time, also studied the low cyclethermal fatigue life of the pistonThrough the above analysis, obtained the dangerous work place and fatigue lifeprediction results of the piston, provide the basis for the piston’s further weight reductiondesign.