Thermo-mechanical Fatigue Analysis Of A Turbo Charged Gasoline Engine Cylinder Head

Cylinder head is a key part of the engine,whose performance directly affects the reliability of the whole engine.Based on engineering practices,this paper makes comprehensive and in-depth research on thermo-mechanical fatigue mechanism,simulated analysis and evaluation method on the background of a 1.0L turbocharged gasoline engine cylinder head forward design.High cycle fatigue safety factor and low cycle fatigue life is predicted by simulating engine normal working and cylinder head cold-hot shock experiment,providing the basis for new generation engines reliability design.Firstly,establish the 3D model and the finite element analysis mesh model of the whole engine.An integrated contact relation model including the complete cylinder head,cylinder block,cylinder head gasket and cylinder head bolt is established by integrated contact multi-field indirect coupling method to avoid the disadvantage of partial model research.The thermal boundary condition is obtained by CFD simulation of water jacket and in-cylinder process to reduce errors of boundary conditions sourced in simple empirical formulas.Secondly,analyze cylinder head thermal load with the solid-fluid coupling method,elastic and plastic finite element analysis of the structural strain and stress of the cylinder head under the thermo-mechanical loading is also conducted.Results show,the highest temperature of the cylinder head at rated load is 217.2?,lower than the limiting value 260?.The equivalent plastic strain of critical point on the cylinder head flame face is 2.088e-03,lower than the limiting value 0.02.Thirdly,predict the thermo-mechanical fatigue performance of the cylinder head by setting different analysis step.Results show,the lowest high cycle fatigue safety factor is 1.21,higher than the limiting value 1.1;the low cycle fatigue life is 7480 cycles,higher than 3000 cycles ruled in the engine reliability experiment,and the mechanical damage portion is 96.47%,the oxidation damage portion is 3.42%.According to reliability analysis theory,cylinder head structure reliability degree is 98.3% under high cycle fatigue stress level and it is 90.6% under low cycle fatigue stress level.It is obvious that low cycle fatigue reliability degree is lower than that of high cycle fatigue.Finally,conduct the reliability test of the engine prototype.Result shows that no damage occurs on the cylinder head,proving the availability of the simulated calculation and the evaluation methodology.The comprehensive and in-depth research method of predicting cylinder head thermo-mechanical fatigue in the forward engineering is proposed in this paper,which plays an important role in engineering.