Finite Element Analysis And Structural-safety-evaluation Of A Combined-piston

With rising oil prices and more strict exhaust emission regulations, the dynamic performance and fuel economy of internal combustion engine are put forward higher request. But the development of the internal-combustion engine, fundamentally, is based on performance improvement and service life rising of main parts.The piston, as one of the key parts of the engine, its work reliability and durability directly affect the overall performance. To meet the needs of high specific power of internal combustion engine, the piston should bear higher heat load and mechanical load. Hot load and mechanical load coupling make piston to produce crackle, piston-ring glued and scuffing of cylinder bore and so on, serious damage the durability and reliability of the internal combustion engine. Therefore, though finite element analysis for the piston, in terms of temperature field, heat load, mechanical load and stress field of their coupling load, understanding the heat load and stress distribution, is great significant to improve its work reliability.Though transient dynamic analysis, we can better understand the dynamic characteristic of piston in whole work cycle, provide the theory basis for its fatigue life analysis, and have important significance to improve its service life. The main content of the article is shown below:(1) Determination of boundary conditions for heat load and mechanical load of the piston. Searching relevant documents, conducting force analysis of piston, determined the boundary conditions for finite element analysis of the piston;(2) Establishing high accuracy finite element model of the piston. According to the temperature field and stress field of the finite element model with refining grid in different area, confirmed the high precision coupling calculation model.(3) Static thermal analysis of the piston. The temperature and heat transfer coefficient imposed according to the third type of boundary conditions, steady-state temperature field were calculated;(4) Thermo-mechanical coupling analysis of the piston. Taking the gas pressure and inertial force the piston beard at the peak breakout pressure as boundary conditions, analyze strength of the piston; By adopting indirect coupling method, taking temperature field and mechanical load distribution as boundary conditions, analyze the coupling stress and deformation of piston;(5) Thermo-mechanical coupling transient dynamic analysis of the piston. Taking the steady temperature field and alternating mechanical loads as boundary conditions, the article analyze transient dynamic of the combination piston in six cycles under calibration condition. Obtains the stress of where stress concentration, the deformation graph of time-process, stress and strain amplitude of the part, provides the theory basis and the necessary boundary conditions for structure improvement and fatigue analysis of the piston.Through the above work, we obtained evaluation basis for security evaluation of combination piston, established the theoretical basis for further reduction the piston heat load and perfect the stress distribution.