基于瞬态动力学的柴油机曲轴疲劳寿命研究

发布时间：2018-04-15 13:18

本文选题：曲轴 + 疲劳寿命预测　；参考：《中北大学》2015年硕士论文

【摘要】：曲轴是发动机内最重要的运动部件之一，其结构参数和性能参数对柴油机整体的重量、可靠性以及寿命都有决定性的影响。在实际工作过程中曲轴受力极其复杂，其内部会产生拉、压、弯、扭的交变应力，致使曲轴过早的出现弯曲疲劳破坏，，在主轴颈和连杆轴颈的过渡圆角处应力集中现象比较严重，在这些地方会过早的产生疲劳裂纹，从而导致曲轴断裂。因此，为了掌握曲轴在工作过程中的应力的分布规律，对曲轴进行瞬态动力学研究和疲劳寿命研究，是很必要的。在今后对曲轴的改进、优化也具有十分重要的意义。针对曲轴会过早的出现弯曲疲劳破坏这一问题，进行了以下几个方面的研究：（1）利用三维造型软件Pro/E建立了曲轴实体模型，并用前处理软件对其进行前处理并离散成有限元模型；（2）分析曲轴所承受的载荷，依据有限元动力学理论基础，结合曲轴结构特点和实际的工作状态，对其进行了动态响应分析，并对动态响应中遇到的模型网格大小的确定、约束方式的确定、接触关系的选择、加载方式的选择以及载荷步选取的方法等进行了对比研究。然后重点研究了应力集中部位的应力状态和特征，并分析应力集中部位的应力-时间历程曲线，以便于了解曲轴动态响应特性，并为疲劳分析提供了载荷数据。（3）在研究曲轴疲劳寿命预测方法的基础上对其寿命进行了预测。具体研究了零件S-N曲线获取及表面加工系数、尺寸系数以及强化系数的修正；疲劳损伤累积方法；损伤参量的选取；（4）在以上研究的基础上对曲轴的危险部位明确后，对其进行了基于Spearman秩相关系数的敏感度研究，通过研究得出了对危险部位的应力影响最大的是过渡圆角半径。
[Abstract]:Crankshaft is one of the most important moving parts in engine. Its structure parameters and performance parameters have a decisive effect on the whole weight, reliability and life of diesel engine.In the actual working process, the crankshaft is very complicated in force, and the internal stress of the crankshaft will produce the alternating stress of tension, compression, bending and torsion, resulting in premature bending fatigue failure of the crankshaft.The stress concentration at the transition corners of the main and connecting rod necks is very serious, and fatigue cracks will occur prematurely in these places, which will lead to the fracture of the crankshaft.Therefore, it is necessary to study the transient dynamics and fatigue life of the crankshaft in order to understand the stress distribution of the crankshaft in the working process.In the future, the improvement of crankshaft, optimization also has very important significance.Aiming at the problem of premature bending fatigue failure of crankshaft, the following aspects are studied:1) the crankshaft solid model is established by using 3D modeling software Pro/E, and the preprocessing software is used to preprocess it and discretize it into finite element model.Based on the finite element dynamics theory, the dynamic response of the crankshaft is analyzed according to the characteristics of the crankshaft structure and the actual working state, and the mesh size of the model encountered in the dynamic response is determined.The determination of constraint mode, the choice of contact relation, the choice of loading mode and the method of selecting load step are compared.Then the stress state and characteristics of the stress concentration are studied and the stress-time history curve of the stress concentration is analyzed in order to understand the dynamic response characteristics of the crankshaft and provide the load data for fatigue analysis.3) the fatigue life of crankshaft is predicted on the basis of the study of fatigue life prediction method of crankshaft.The S-N curve acquisition and the modification of surface machining coefficient, dimension coefficient and strengthening coefficient, the fatigue damage accumulation method, and the selection of damage parameters are studied in detail.4) on the basis of the above research, the sensitivity of the crankshaft is studied based on the Spearman rank correlation coefficient after the dangerous position of the crankshaft is defined. The results show that the most important influence on the stress of the dangerous part is the transition radius.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK423

【参考文献】