电机换向抽油机结构的动态特性分析及参数优化设计

【作者】 王新琴；

【导师】 曾励； 杨海滨；

【作者基本信息】 扬州大学 ， 机械制造及其自动化， 2005， 硕士

【摘要】 结构的动态特性分析是结构动力学领域的一个重要研究方面,已被西欧发达国家列为结构设计领域的重点发展方向之一。本文以电机换向抽油机这一新型抽油机为工程研究背景,对其进行动态特性分析。抽油机是由传动件、支承件等组成的,保证传动部分各部件可靠、稳定地工作固然重要,然而传动部分要靠支架来支承,因此支架的可靠性、稳定性将会对整个抽油机产生直接影响。文章对抽油机支架动态特性的理论分析和试验分析进行了系统研究,提出了试验方案,为支架下一步的动力响应分析和优化设计提供了理论和实验基础,也为抽油机结构的改进提供了一条途径。 本文首先总结了国内外结构动态特性分析的研究成果,然后阐述了结构模态分析的理论基础,并以简支梁为例,讨论了在任意冲击载荷下结构的有限变形问题。文章从抽油机的组成和工作特点入手,系统地应用了有限元方法,综合考虑了提高计算精度和降低计算规模这个建模的根本问题,利用ANSYS软件,建立了抽油机支架的有限元计算模型。本文所建的模型采用空间桁架结构,混合使用梁单元和杆单元来离散支架,并对支架进行了静力分析、模态分析,讨论了支架结构参数变化及材料变化对模态的影响。对支架进行了极端情况下的瞬态分析,即钢丝绳断,支架在冲击载荷下的响应分析,并以分析结果为依据,从实际出发,提出建议。 分析结果表明,设计的支架结构存在较大的安全余量。本文在此基础上,以各杆件截面尺寸为设计变量,节点最大位移、杆内最大应力及截面尺寸范围为约束条件,支架重量最小为目标函数,对支架的结构参数进行了优化设计。优化后,根据就近原则确定各杆截面尺寸。经有限元再分析证明:优化后的支架能满足设计要求,且减轻了重量,降低了制造成本。 结构动态特性分析要求对结构系统进行较为准确的数学描述,目前工程中主要应用有限元技术来建立理论计算模型。这种方法采用了离散化的思想:将连续系统离散为一个节点上互相关联的离散结构。但是由于对结构物理、几何特性的假设和对结构约束及连接状态等的简化,使得理论计算模型在模型结构、模型阶次以及模型参数等三个主要方面存在误差,其计算结果的精度是否可靠,这需要更多还原

【Abstract】 The dynamic characteristic analysis of structural systems has increasingly studied in structural dynamics field, and it has been regarded as one of the important direction to development by occidental developed countries. This paper is based on the engineering research on complex structures of the motor-reversing type pumping unit. The pumping unit is mainly made up of driving members, support members. Of course, it’s very important to ensure the driving members work reliably and stably. But it is the bracket that supports them, so, the reliability and stability of the bracket affect the whole pumping unit directly. This paper systematically makes the dynamic characteristic analysis and experimental verification of the bracket, and establishes a foundation on the dynamic response calculation, the dynamic characteristic analysis of the bracket and optimization in structural designing step by step. This work also finds a way for the improvement of the bracket simultaneously.This paper summarizes researches on dynamic characteristic analysis at home and abroad at first. And then, based on the modal analysis theory, it analyzes the component and working situation of the motor-reversing type pumping unit, considers improving accuracy and reducing calculational scale to a lower rank synthetically, then makes calculational model of the bracket with Finite Element Method (FEM) applied. In this paper, the model is made as a special truss work with beam element and link element used together to disperse the bracket. Then the static analysis, modal analysis and response to impact load are all made in this paper. And influence to mode produced by different structural parameters and material is discussed in the paper too. This paper also analyses another kind of pumping unit which influenced deeply by impact load, and discusses the relation among the magnitude of impact load, acting time and the maximum displacement of the bracket.The result forenamed shows that he safety margins of static strength and stiffness are excessive. According to this, this paper takes size of sections as design variables, maximum displacements of nodes, maximum stress of members and range of sections’ size as constraint conditions, and minimum weight of bracket as object function, then makes optimization designing about the structural parameters of the bracket. In the end,this paper makes analysis again on the bracket after optimization designing, and draws a conclusion that the modified bracket can satisfy the working requirement and result in a reduction in weight and cost.The dynamic characteristic analysis of structures is required to describe the structural systems accurately, and FEM is often used to make theoretical calculation models in engineering. FEM applies discretization theory, that is, the continuous system is dispersed into a discrete system with interdependence in a node. Through the hypothesis of the structural material and shape, the simplification of the structural constraints and joints, the theoretical calculation model is made with finite element techniques. And because of the hypothesis and simplification, the calculation model gets error about structure, orders and parameters of itself. So, it needs tests to verify whether the precision of calculation results is reliable. According to this, the paper analyzes the process and principles of modal test and stress strain test, and brings forward ideas and methods about structural modal test. But owning to the limit of test conditions, the modal test hasn’t been executed.更多还原