基于UEL的水电机组导轴承支架非线性连接模态特性分析

Analysis of Nonlinear Connection Modal Characteristics of the Hydroelectric Generating Unit’s Guide Bearing Bracket Based on UEL

模态分析是水电机组故障诊断的重要方法,但其传统方法缺少对接触部分非线性接触的模拟手段,直接影响模态分析的准确性,也无法对链接部位的失效过程及趋势进行分析。该文基于用户自定义单元子程序接口(user-defined element subroutine interface,UEL),建立了结合部三维非线性专用分析单元模型。推导所提模型有限元格式的基本方程,获得表征材料非线性特性的本构关系;给出螺栓连接的固定结合部的静态分析,以及立式水轮发电机导轴承支架的模态分析算例;给出导轴承支架的支臂末端螺栓连接变刚度计算的工程应用实例。实验与仿真对比结果表明了建立的UEL三维非线性接触分析专用单元模型的正确性;连接失效分析表明了随着导轴承支架接触刚度的下降,会在整机模态频率计算中引入新的频率段这一结果的重要性。

Modal analysis is an important method for the fault diagnosis of hydroelectric generating units.However,due to the lack of simulation means for the nonlinear contact of contact parts in traditional modal analysis methods,the accuracy of modal analysis is directly affected,and the link part’s failure process and trend cannot be analyzed.Based on the user-defined element subroutine interface(UEL),a three-dimensional nonlinear special analysis element model of the joint is established in this paper.Firstly,the basic equations of the finite element scheme of the model are derived,and the constitutive relations representing the nonlinear characteristics of the material are obtained;secondly,the static analysis of the fixed joint of the bolt connection and the modal analysis of the guide bearing bracket of the vertical hydro generator are given.Finally,an engineering application example of variable stiffness calculation of bolt connection at the end of guide bearing support arm is given.The comparison between experimental and simulation results shows the correctness of the special element model of the established UEL three-dimensional nonlinear contact analysis.The failure analysis of the connection indicates the importance of introducing a new frequency band into the modal frequency calculation of the entire machine as the contact stiffness of the guide bearing bracket decreases.