【作者】 陈永哲；

【导师】 闫伟；

【作者基本信息】 山东大学 ， 交通运输工程， 2015， 硕士

【摘要】 发动机作为现代社会的主要动力源之一,其广泛应用在汽车、船舶以及工程机械等领域。作为一种在现实生活中广泛应用的动力机械,其性能和可靠性严重影响着我们的生活。因此,如何提高发动机的可靠性成为了无数学者和专家孜孜以求的目标。活塞作为发动机的主要零部件之一,其可靠性对发动机的性能及可靠性起着至关重要的作用。为分析活塞的受力情况,本文对活塞进行了有限元仿真计算。首先利用AVL_EXCITE软件计算了发动机缸内燃气的最高爆发压力和平均工作温度以及侧向力等,结合发动机的实测数据、经验公式和半经验公式等确定了活塞的温度场和应力场计算的边界条件,利用ABAQUS软件计算了活塞在热负荷工况、机械负荷工况以及热机耦合工况下的应力及应变。计算结果表明活塞在热负荷工况下其最大应力出现在了活塞内腔顶部,其最大变形出现在了活塞顶部。在机械负荷工况下活塞的最大变形出现在活塞裙部底端,最大应力出现在了活塞销座内部上侧处。对于热机耦合状态下活塞的最大应力出现在了活塞销座内部上侧,其最大变形出现在了活塞顶部。文章还对缸套在热机耦合工况下的应变进行了计算,提取了缸套在不同部位处的径向变形量。为研究活塞寿命与其工况之间的关系,本文探讨了活塞在热负荷工况、机械负荷工况以及热机耦合工况下活塞寿命与应力之间的关系。结果表明活塞在不同热负荷、机械负荷以及热机耦合条件下其寿命与应力之间的关系分别服从于阿伦尼斯模型、逆幂律模型和广义艾林模型。文章还对活塞在不同工作状况下的磨损量进行了分析,利用相关系数证明了不同工况下通过耐久性试验所得的活塞磨损量数据与利用仿真试验所得的活塞和缸套变形后重合面积的线性相关性比较显著,利用活塞与缸套的仿真重合面积对活塞的磨损趋势进行了估计,得到了活塞磨损量随工况变化的变换规律。本文基于威布尔分布对活塞的现场数据进行分析,探讨了利用最小二乘法来求解活塞可靠性的过程与思路。对于活塞的小样本试验,由于其样本量较小,不能够利用常规方法来求取其可靠性特征量,文章介绍了利用贝叶斯小子样理论来求取其可靠性特征量的方法。通过对比发现,利用贝叶斯小子样技术求得的可靠性特征量与利用最小二乘法求得的可靠性特征量十分相似,表明了贝叶斯小子样方法的可行性。最后对全文进行总结,指出了文章的不足之处且对后续工作进行了展望。更多还原

【Abstract】 As one of the main sources of power in modern society, engines are widely used in automobile, ship and engineering machinery and other fields. As a widely used machinery in our real life, its performance and reliability seriously affect our life. Therefore, how to improve the reliability of the engine becomes a target for numerous scholars and experts pursued. And as one of the main parts of engine, the piston’s reliability plays an important role in engine’s performance and reliability.For the analysis of the force on the piston, the finite element simulation is carried out in this paper, the piston is calculated. First AVL_EXCITE software is used to calculate the maximum explosion pressure of gas in cylinder and the average working temperature as well as the lateral force and so on, combined with the measurements of the engine, semi-empirical formula and empirical formula to determine the boundary conditions of the piston temperature field and stress field calculation, using ABAQUS software to calculate the stress and strain of the piston in the condition of heat load, mechanical load and thermal-mechanical coupling conditions. Calculation results show that in thermal load conditions the maximum stress occurred in the second slot, the maximum deformation occurred in the top. Under mechanical load conditions of piston the maximum deformation appears in the lower end of the piston skirt, maximum stress appears in the piston pin internal upper. For thermal-mechanical coupling conditions the maximum stress appears in the piston pin internal upper too, the maximum deformation appears at the top. The article also calculates the cylinder liner’s strain under the thermal-mechanical coupling conditions.To study the relationship between the life of the piston and its working condition, this paper discusses the relationship between the piston life and stress under the conditions of heat load conditions, mechanical load conditions and thermal-mechanical coupling conditions. The results show that in different heat load, mechanical load and thermal-mechanical coupling conditions, the relationship between the life and stress were subject to Arrhenius model, inverse power law model and generalized eyring model. The wear of the piston under different working conditions are analyzed. Put forward using the trend of the piston and cylinder liner deformation amount of overlap method to represent the piston wear, and the results are analyzed. Got the transformation of the piston wear regularity by the working conditions.Based on the Weibull distribution, this article analyzes the field data of the piston, discusses the process and methods to solve of reliability of piston with the least squares method. Due to small sample size, it will not be able to use conventional method to calculate the reliability characteristics quantity. This paper introduces a method to calculate the reliability characteristics quantity by using of Bayes theory of small sample. By contrast, found that the reliability characteristics are similar by using the method of the bayes and by least square method. Show the feasibility of bayesian small sample method.Finally, summarize the full text, points out the shortcomings of the article and the follow-up work is prospected.更多还原