Fatigue And Reliability Study Of Pinston Pin Boss

With the engine intensive degree increasing, the reliability issues have also been wide spread concern, and related research is getting more and more attention. As the primary source of engine piston parts, in the process of work, it is directly under huge explosion pressure. Piston continuously bears alternating thermal load and mechanical load.The working environment of it is very poor. In the case of engine damage, the fatigue damage of piston accounted for a large proportion. Piston pin boss, as the common parts of damage, the study of its reliability becomes one of the priorities. The study is of great significance for the improvement of the optimized design and reliability of piston.The paper modified the boundary condition of piston finite element simulation by piston strain test, analyzed the piston bearing strength of different pin hole shapes on rated load and over load,made three kinds of piston hydraulic mechanical fatigue test standard combined with engine experiment and piston hydraulic fatigue experiment,calculated the median intensity of piston fatigue experiment, and veried the piston fatigue test with the analysis results, which provided theory and calculation basis for improving the bearing capacity of piston pin bore.The main work of the thesis is as follows:1.Firstly, strain test of a certain type piston was carried out. And finite element method was used to analyze the piston with different friction coefficient. Compareed with the piston strain test dates, we can get a more practical friction coefficient. Combined with engineering design and related experiments, it is recommended that roughness of piston pin hole should bebetween Ra0.2and Ra0.4. Through the DLC coating processing, we can both guarantee sufficient lubrication and reduce failure problems of the piston pin hole.2.Several piston with different pin hole shapes were designed. And finite element analysis under different working conditions was also carried out. The stress distribution of piston pin seat under different mechanical loadings was compared and the strength evaluation was given based on the strength theories. In addition,the fatigue coefficient and fatigue life of piston pin holes with different shapes were calculated.3. By the analysis of pin cracking failure accidents of the piston pin, simulation of piston with different piston pin wall thickness was carried out. Then, Stress of the piston is obtained. Through the analysis of simulation results, summarizes the affection of the thickness to the piston pin seat section stress. 4. Combining with the engine and piston hydraulic fatigue experiments, three piston hydraulic mechanical fatigue test specification were put forward and summarized Testing methods and application conditons of the scheme are expounded, the strength calculation of piston hydraulic fatigue experimental results was did and piston hydraulic mechanical fatigue test of part of the specimen in finite element analysis was carried out.the sample number with crack and the crack position were consistent with the finite element analysis results.