大型水电站检修组合机床有限元分析与结构优化

发布时间：2018-04-30 21:03

本文选题：水轮机组 + 组合机床　；参考：《湖南大学》2014年硕士论文

【摘要】：大型水电站水轮机组由于检修时间和现场环境的限制，对水电站机组的转轮、底环、座环等大型结构部件的修复，提出了智能化程度高的现场修复理念。这不仅可以克服机组局部修补精度不高的问题；而且还可以节省大量的人力物力资源，所以设计制造现场水电机组修复的数控多功能组合机床非常有必要。大型水电站机组现场检修的数控多功能组合机床结构复杂，该机床的刚度和振动频率等机械性能关系到机床的加工精度、加工效率和工件表面粗糙度，关系到机床的安全可靠性及使用寿命。有必要对该机床床身结构等进行动静态分析，，找出机床床身的最大变形处和最大应力；通过模态分析可以判断振型是否影响该机床加工精度；这样可以对机床床身相关的部位进行优化设计来改进性能。所以本文的研究具有重要的理论与工程意义。本文对国内外数控机床结构有限元分析与结构优化研究的现状与发展做了全面深入的评述。对ANSYS Workbench平台建立机床结构有限元分析模型做了阐述。本文对水轮机转轮底环止漏环现场加工时的专用组合机床结构进行有限元静力分析与振动模态分析；在此基础上对机床结构进行了优化改进，并且对优化后的机床结构进行了有限元静力分析与振动模态分析。机床结构优化改进后整个机床的静动态特性都有了明显提高，机床总体变形和各个方向的变形有了较为明显的改善，应力集中也有明显的改善，静态性能有了显著提高，机床结构刚度分布较合理；机床固有频率和模态振型也有一定的改善。其次，针对水电机组转轮下环现场加工数控组合机床的悬臂系统，分析计算该加工工况下机床的变形及应力，并以机床设计部门提出的机床刀尖处综合变形0.15mm为目标，提出机床结构的改进措施，增强该机床悬臂系统刚性，减小机床在受切削力时的结构变形，提高机床加工质量；提出了适当降低机床切削力的方案。最后，对大型水电站水电机组转轮现场检修加工数控专用组合机床进行了静特性和振动模态有限元分析。分析结果认为机床刀架刀夹附近刚度需要加强；机床刀架立柱的轨道处安装刀具，因此该处的各方向有限元变形是影响加工精度的重要因素，要引起重视。机床垂直连接臂和刀架部分是薄弱环节，影响加工精度，需要改进提高其固有频率。
[Abstract]:Due to the limitation of maintenance time and field environment, the paper puts forward a high intelligent field repair idea for large structural parts such as runner, bottom ring, seat ring and so on. This can not only overcome the problem of low repair accuracy, but also save a lot of manpower and material resources, so it is necessary to design and manufacture the NC multifunctional machine tool for the repair of hydropower units. The structure of NC multifunctional machine tool for on-site maintenance of large hydropower station unit is complex. The mechanical properties such as rigidity and vibration frequency of the machine tool are related to the machining accuracy, machining efficiency and surface roughness of the workpiece. Related to the safety and reliability of machine tools and service life. It is necessary to make dynamic and static analysis on the structure of the machine bed, to find out the maximum deformation and stress of the machine bed, and to judge whether the mode shape affects the machining accuracy of the machine by modal analysis. In this way, the machine bed related parts can be optimized to improve the performance. Therefore, the study of this paper has important theoretical and engineering significance. The present situation and development of finite element analysis and structural optimization of CNC machine tools at home and abroad are reviewed in this paper. The finite element analysis model of machine tool structure based on ANSYS Workbench platform is described. In this paper, the finite element static analysis and vibration modal analysis are carried out for the structure of the special composite machine tool, which is used in the field processing of the leakage ring of the bottom ring of the runner of a hydraulic turbine, and the structure of the machine tool is optimized and improved. The finite element static analysis and vibration modal analysis of the optimized machine structure are also carried out. The static and dynamic characteristics of the whole machine tool have been improved obviously after the optimization and improvement of the structure of the machine tool, the overall deformation of the machine tool and the deformation in all directions have been obviously improved, the stress concentration has also been obviously improved, and the static performance has been remarkably improved. The stiffness distribution of machine tool structure is reasonable, and the natural frequency and modal mode of machine tool are also improved. Secondly, aiming at the cantilever system of NC combined machine tool which is machined by the lower ring of the runner of hydropower unit, the deformation and stress of the machine tool under the working condition are analyzed and calculated, and the target is the comprehensive deformation 0.15mm at the cutting tip of the machine tool proposed by the machine tool design department. The improvement measures of the machine tool structure are put forward to enhance the rigidity of the cantilever system of the machine tool, to reduce the structural deformation of the machine tool under the cutting force, and to improve the machining quality of the machine tool, and the scheme to reduce the cutting force of the machine tool is put forward. Finally, the static characteristics and vibration modal finite element analysis of the NC machine tool for the field maintenance and processing of the runner of the large hydropower station are carried out. The analysis results show that the stiffness near the tool holder needs to be strengthened, and the tool is installed in the track of the tool holder column, so the finite element deformation in all directions is an important factor affecting the machining accuracy, which should be paid more attention to. The vertical connecting arm and the tool holder are weak links, which affect the machining accuracy and need to be improved to improve the natural frequency.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK730.8

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