【作者】 何昕；

【导师】 王启富；

【作者基本信息】 华中科技大学 ， 机械工程， 2011， 硕士

【摘要】 数控机床向高速度、高精度、高效率的方向发展,必然要求机床具有较高的加工性能和较轻的重量。床身作为机床的关键零部件,其结构性能直接影响机床的加工性能。结构性能包括静、动态特性和热特性,其中动态特性的提高对降低床身振动具有很大意义。本文研究了某立式铣床床身的结构性能并基于模态分析进行结构优化。为了研究床身的静态特性,在CATIA中建立床身的几何模型,利用SpaceClaim快速简化几何模型并导入ANSYS中建立有限元模型。静力分析的结果表明床身具有较高的静刚度和强度,为减轻床身重量提供依据。为了克服床身静态设计的不足,提高床身的动态特性,在模态分析的基础上,研究了床身的动刚度薄弱环节。提出了利用元结构和筋板理论修改模型,建立五种方案。通过比较后选择具有较高固有频率和较轻重量的方案四。在此基础上研究出砂孔尺寸和筋板厚度对床身固有频率的影响。最后获得的方案六相比原方案重量减轻16.76%,第一阶固有频率增加35.32%。研究表明选择合适的元结构和筋板布局可以提高结构的固有频率并降低重量、节省材料。为了控制床身的热变形,研究了温升对床身的影响。分析床身的热源和边界条件,建立床身温度场的有限元模型并在ANSYS中求解了床身的稳态温度场,结果表明床身的温升较小。施加静态载荷和热载荷对床身进行热-应力耦合分析,结果表明床身的耦合变形主要来自于热变形。对导轨的变形进行分析,表明导轨满足导向精度要求。结合床身的热变形特点,提出一些降低热变形、减小热误差的措施。更多还原

【Abstract】 With the development of Numerical Control machine tools to the high-speed, high precision and high efficiency, higher machining capability and lighter weight are necessarily required. As the key component of machine tools, the bed’s structure performance will directly influence the processing performance. The structure performance contains the static & dynamic characteristics and the thermal characteristics. Improving the dynamic characteristics of the bed will reduce the vibration of the bed. This thesis studies the structural performance of a vertical milling machine bed and its structural optimization based on modal analysis.In order to research the static characteristics of the bed, the geometric model of the bed is created in CATIA and simplified efficiently in SpaceClaim. After importing the model to ANSYS, the finite element model is established for static analysis. The result of static analysis of the bed indicates that it is extremely high in the static stiffness and intensity of the bed, and foundations are provided to lighten it.In order to overcome the disadvantages of static design of the bed, to raise its dynamic characteristics, the weakness of the structure is studied based on the modal analysis of the bed. Five schemes of improving the bed are proposed based on unit structures & rib walls theory. It finally find that scheme four’s natural frequency is quite high and its weight is lightest relatively. The influences of the diameter of sand hole and the thickness of rib walls to the natural frequencies of the bed are researched on the base of previous work. Finally, the scheme six is released which is 16.76 percent lighter and the first frequency is 35.32 percent higher than the original one. It illustrates that the natural frequency can be raised, the weight can be reduced and the material can be saved by choosing the appropriate unit structures and rib walls.In order to control the thermal deformation of the bed, it studies the impact of the temperature rise on the bed. Based on analyzing the heat source and boundary conditions of the bed, the finite element model of the bed’s temperature field is constructed. After the calculation accomplished, the bed’s temperature field dedicate that the temperature rise is extreme low. Through exerting the ststic & thermal load and calculating the heat-structure coupling, it is verified that the major deformation of the bed comes from the thermal deformation. It also indicates that the slide guides have a high steering precision. Combined with the thermal deformation characteristics of the bed, several measures are offered to reduce the thermal deformation and compensate the thermal error.更多还原