【作者】 李彪；

【导师】 张大卫； 常文芬；

【作者基本信息】 天津大学 ， 工程（专业学位）， 2023， 硕士

【摘要】 刚度质量比是衡量数控机床整机结构静动特性的重要指标,而实现高刚度质量比目标的主要途径是基础结构件与筋板拓扑结构设计。仿生设计方法被认为是结构件设计的有效方法,但目前结构件设计方法仍存在筋板设计结果较为复杂、难以进行数学描述、理论方法较难应用于实际生产制造等问题。因此,本文从仿生设计的角度,探究了基础结构件参数化建模方法及筋板拓扑结构的数学描述方法,研究了结构件优化设计流程与整机有限元建模方法,搭建了静动特性试验平台对试验样件进行试验验证。全文研究内容如下:研究了结构件筋板元结构参数化建模方法及元结构特性。分析了自然界中高刚度质量比的分叉结构形成特点,从仿生的角度提出了基于自然界分叉单元的三叉元结构模型,建立了结构件筋板生长规则,探究了结构件筋板生长路径的迭代关系,在此基础上确定了筋板结构的生长流程,最终构建了结构件参数化模型。通过仿真分析,掲示了元结构尺寸变量及出砂孔设计参数等对结构动特性的影响规律。为提高结构件刚度质量比,需要在完成筋板拓扑结构布局的基础上,确定结构件的最佳尺寸。因此,提出了基于三叉元结构的机床结构件优化设计流程。首先,通过三叉元结构的生长规则和参数化模型完成结构件的参数化设计;其次,利用拉丁超立方法确定样本点;再次,基于i SIGHT的结构件CAD/CAE集成优化平台,获取机床结构件样本点的仿真结果。在此基础上,利用BP神经网络对样本点训练,生成BP神经网络模型;最后,通过遗传算法对BP神经网络模型求解,获得机床结构件最优解。以床身结构件为例,验证了该设计流程的正确性。为验证优化后的结构件对整机静动特性的影响,构建了整机精细化有限元模型。基于弹簧阻尼基本连接单元探究了整机结合部有限元建模方法,针对某型号精密卧式加工中心阐述了结合部等效方法及弹簧刚度阻尼参数确定方法,通过APDL语言重建了多工况下有限元模型,依据整机有限元仿真结果,验证了采用筋板拓扑结构仿生设计方法改进的T型床身,能够提高整机的静动特性。针对T型床身结构特点设计了床身试验样件,搭建了导轨安装基面重力载荷变形测试及锤击法动态特性测试试验系统。开展了试验样件导轨安装基面重力载荷变形试验、动态特性试验,得到了加载前后导轨安装基面的变形趋势、试验样件前六阶固有频率及振型,对比验证了理论研究和仿真分析的正确性。更多还原

【Abstract】 The stiffness to mass ratio is an important index to measure the static and dynamic characteristics of the entire structure of CNC machine tools,and the main approach to achieve the goal of high stiffness to mass ratio is the design of basic structural parts and the topological structure of rib plates.The bionic design method is considered to be an effective method for structural part design.However,the current structural part design method still has problems such as more complex rib design results,difficulty in mathematical description,and difficulty in applying the theoretical method to actual manufacturing.Therefore,from the perspective of bionic design,this paper explored the parametric modeling method of the basic structural parts and the mathematical description method of the topological structure of rib plates,investigated the optimization design process of the structural parts and the finite element modeling method of the entire machine,and built a static and dynamic test platform to test and verify the test specimens.The full research content is as follows:The parametric modeling method and meta-structural characteristics of the rib plate meta-structure of structural parts are studied.The formation characteristics of the bifurcated structure with high stiffness to mass ratio in nature are analyzed,and the triple bifurcation structure model based on the bifurcated unit in nature is proposed from the bionic perspective,established the growth rules of structural parts rib plates,explored the iterative relationship of the growth path of structural parts rib plates,and determined the growth process of rib plate structures based on this.Finally,a parameterized model of structural parts was constructed.Through simulation analysis,the influence of structural size variables and sand hole design parameters on the dynamic characteristics of the structure was demonstrated.In order to improve the stiffness to mass ratio of structural parts,it is necessary to determine the optimal dimensions of structural parts based on the completed topological layout of the rib plates.Therefore,the optimized design process of machine tool structural parts based on the triple bifurcation structure is proposed.Firstly,the parametric design of the structural parts is completed by the growth rules and parametric model of the triple bifurcation structure;secondly,the sample points are determined by using the Latin hypercube sampling;next,the simulation results of the sample points of the structural member of the machine tool are obtained based on the integrated CAD/CAE optimization platform of structural member of i SIGHT.Based on this,BP neural network is used to train the sample points and generate BP neural network model;finally,the BP neural network model is solved by genetic algorithm to obtain the optimal solution for the structural parts of machine tools.The correctness of the design process is verified by taking the bed structural parts as an example.In order to verify the influence of optimized structural components on the static and dynamic characteristics of the whole machine,a refined finite element model of the whole machine is constructed.Based on the spring-damped basic connection unit,the finite element modeling method of the whole machine joint is explored,the equivalent method of the joint and the method of determining the spring stiffness damping parameters are elaborated for a certain type of precision horizontal machining center,and the finite element model under multiple working conditions is reconstructed by APDL language.Based on the finite element simulation results of the whole machine,it was verified that the T-shaped bed improved by the bionic design method of topological structure of rib plates could improve the static and dynamic characteristics of the whole machine.The bed test specimen was designed according to the characteristics of T-bed structure,and the test system of gravity load deformation test and dynamic characteristics test of hammering method was built.The gravity load deformation test and dynamic characteristics test of the test specimen were carried out,and the deformation trend of the base surface of the rail mounting before and after loading,the first six orders of inherent frequency and vibration pattern of the test specimen were obtained,and the correctness of the theoretical research and simulation analysis were verified by comparison.更多还原