LOW-CYCLE FATIGUE RELIABILITY ANALYSIS OF ENGINE PISTONS BASED ON PC-KRIGING MODEL

Low-cycle fatigue is a typical failure mode of engine pistons. In order to study the influence of multi-source uncertainty factors on the reliability of low-circumference fatigue of pistons and improve the efficiency of the reliability analysis, a new reliability calculation method is constructed based on the polynomial-chaos-based Kriging (PC-Kriging) model and the Monte Carlo simulation (MCS), and the accuracy and efficiency of this method are proved by numerical examples. Taking the piston group structure of a certain diesel engine as the research object, a finite element model of the piston is established based on the thermal-mechanical coupling analysis, and the reliability analysis of the piston for low-cycle fatigue is carried out by using this method, taking into account the critical dimensions, the material properties, and the uncertainty of the load. The results of the reliability analysis show that, compared with the same type of method, this method is more efficient in calculation, requiring only 20+93 finite element calculations, and the probability of fatigue failure is 1.053% when the expected design life of the piston is 1.4×10⁴. The sensitivity analysis shows that， the height of the piston, the piston diameter, the elasticity modulus of the material, and the parameters of the fatigue calculation model have a greater influence on the reliability. The analysis results can provide a guidance for the reliability design of the piston.