摘要在热动力装置中，内燃机的应用最为广泛。通过燃料在燃烧室中的燃烧，产生大 量热能，将高温高压燃气产生的能量通过连杆、曲轴转换为机械能。活塞为内燃机中 最重的部件，它的运行对整个内燃机的工作的安全性有很大的影响。但活塞的工作环 境是最为恶劣的，它同时承受因高温产生的热载荷和因气体压力和连杆、曲轴的旋转 产生的机械载荷，这些载荷会使活塞产生相应的应力和变形，应力和变形的大小将会 影响内燃机的可靠性，经济性和使用寿命，所以对内燃机活塞的强度校核是很有必要 的。83967

本文首先利用三维建模软件 Pro/E 进行建模，然后导入 ANSYS 软件中进行有限 元分析。分析计算在有限分析中要用到的热边界条件和载荷条件和相应的约束，在有 限元分析先得到活塞的温度场，进而得到热应力和热变形，通过对活塞施加机械载荷 得到机械应力和变形，最后将两个载荷耦合得到最终的应力和变形，并获得所需的计 算结果。

结果表明：4F20 柴油机活塞在热载荷和机械载荷耦合作用得到的应力和变形， 不是两两相加那么简单，而是产生了相互作用。将得到的三种结果进行对比，得到最 大应力为耦合场中活塞销座处，此时起主导作用的是机械载荷。同时，顶部由于温度 较高，起主导作用的是热载荷。最终得到的计算结果满足 4F20 柴油机活塞材料的要 求。

毕业论文关键词：活塞；有限元分析；应力；变形

Abstract The internal combustion engine is the most widely used application in thermal power plant。 By burning fuel in the combustion chamber, generating a lot of heat, the energy of high pressure gas is converted to mechanical energy by a connecting rod and a crankshaft 。 Piston is the most heaviest part in the internal combustion engine, it's running have a great impact on the security of the working of the entire internal combustion engine。 But the work environment of the piston is the worst, because it receive thermal load generated by high temperatures and the mechanical loads due to gas pressure and the rotation of connecting rod and crankshaft。 These will cause the piston to produce the corresponding stress and deformation。 The size of stress and deformation will affect reliability, economy and life of the engine, so the strength check of the internal combustion engine piston is necessary。

At First, model in three-dimensional modeling software Pro / E and then import in ANSYS software to have a finite element analysis 。 Analysis calculated to use in a limited analysis of thermal boundary conditions and loading conditions and corresponding constraints, finite element analysis to get the temperature field of the piston, and then get the thermal stress and deformation of the piston by applying mechanical loads and mechanical stress to give deformation, and finally get the final two load coupling stress and deformation, and obtain the desired results。 Analysis and calculate thermal boundary conditions and loading conditions and corresponding constraints which used in finite element analysis。 Firstly, obtain temperature field of the piston in the finite element analysis。 Secondly, get the thermal stress and deformation。 Thirdly, by applying a mechanical load on the piston to obtain mechanical stress and deformation。 Lastly, let two load couple to get the final stress and deformation and get the result I want。

The results show that letting 4F20 piston’s thermal loads and mechanical  loads couple to get stress and deformation is not like two and two phase,but they have interaction。 Compared the top three results obtained from  analysis  ,maximum  stress field  is  in the  piston pin  boss  by  coupling  two loads,At this  time ,the mechanical   load