采煤机摇臂传动系统及传动轴的时变可靠性理论研究

Transmission system of a shearer ranging arm is the power transmission parts of the cutting unit of a shearer, whose reliability determines whether the entire shearer can operate safely, reliably and efficiently. Transmission system and transmission shaft of ranging arm of a certain type shearer are taken as the research object in this project, and a theoretical and technical system for optimized design of parts including reliability allocation, stochastic finite element analysis, time-dependent reliability analysis, reliability sensitivity analysis and reliability-based robust optimization design is established. Firstly, factors such as reliability index, running time, importance, complexity and technical cost of the subsystems and parts of the shearer cutting unit are taken into consideration, reliability allocation of cutting unit is studied and reliability target values of each transmission shaft in the transmission system of the ranging arm are determined. Secondly, stochastic finite element mathematical model of the transmission system of the ranging arm is established, dynamic characteristics of the transmission shaft of the ranging arm are analyzed, and rationality of design of transmission shaft is verified. Then, strength, stiffness and dynamic limit state equations of the transmission shaft are established respectively, and reliability analysis and reliability sensitivity analysis are studied. Finally, multi-objective robust optimization model of the transmission shaft is established through taking allocated reliability as the index and mass minimization and robust maximization of the shaft as the target. This method provides theoretical and technical support for design and manufacture in life cycle of transmission system and transmission shaft.

采煤机摇臂传动系统作为采煤机截割部的动力传递部件，其可靠性水平决定了采煤机能否可靠和高效的运行。本项目以某型采煤机摇臂传动系统及传动轴为研究对象，建立一种集可靠性分配、随机有限元分析、时变可靠性分析、可靠性灵敏度分析及可靠性稳健优化设计于一体的零部件优化设计理论与技术体系。首先，考虑采煤机截割部中子系统和零部件的可靠性指标、运行时间、重要程度、复杂程度、技术成本等因素，对截割系统进行可靠性分配研究，并确定摇臂传动系统中各传动轴的目标可靠度值；其次，建立摇臂传动系统的随机有限元模型，对摇臂传动轴进行动态特性分析，并验证传动轴设计的合理性；再者，建立传动轴的强度、刚度和动态极限状态方程，对传动轴进行时变可靠性及灵敏度分析，最后，以分配后的可靠度为指标，轴的质量最小化和稳健最大化为目标，建立传动轴的多目标稳健优化模型。该方法为传动系统和传动轴全寿命周期的设计、制造和使用提供理论与技术支撑。

本项目以MG750和MG500两种采煤机截割部的摇臂系统为研究对象，考虑工况下零件的强度退化以及外载荷随机性的因素，对摇臂系统及传动件（轴和齿轮）进行可靠性分析，并考虑参数及失效模式相关性对可靠性的影响。建立“轴承-转子”系统模型，对轴承和轴分别进行动态特性分析，运用遗传神经网络技术、动态可靠性相关理论分析了齿轮轴结构尺寸、材料属性参数、轴承径向刚度、齿轮啮合频率等参数对系统共振失效的影响。啮合频率、齿轮轴属性参数、轴承径向刚度对齿轮轴刚度可靠性的影响。轴承结构、材料参数、径向游隙及外载荷随工作转速变化下对轴承径向刚度的影响，而后建立轴承滚子与外滚道接触最大正交切应力与轴承结构材料参数之间的函数关系，研究轴承的结构参数对轴承疲劳强度的可靠性影响。最后，综合多种失效模式及可靠性灵敏度计算结果，建立相应数学优化模型，完成零件易破坏部位的结构可靠性稳健优化设计。在采煤机系统结构设计方面，针对目前采用经验设计法设计的产品通常会出现尺寸较大的情况，导致结构不尽合理，项目建立了采煤机系统可靠性模型，对采煤机的系统进行了可靠性分配，基于分配后的摇臂系统可靠度进行结构优化和时变可靠性再分析，进而获得具有结构轻量化、可靠性分配合理、满足可靠性要求的结构参数。此项目的研究成果为采煤机零部件设计和加工、摇臂传动系统可靠性的研究提供了参考依据。