数值耦合技术的研究及其在高速金属切削问题上的应用

发布时间：2018-04-04 05:33

本文选题：高速金属切削　切入点：有限元　出处：《北京理工大学》2016年博士论文

【摘要】：高速切削加工技术有着高生产效率和高加工精度的特点,所以自其理念提出就受到广泛关注,成为新的热点课题。与传统切削工艺相比,数值方法不仅可以克服试验方法的不足,实现高速切削过程的定量分析,而且投资少,周期短,受到了不少研究工作者的青睐。本文对有限元、物质点以及边界元等数值方法进行了研究,结合各自的优缺点,建立数值方法耦合技术,开发相应地程序,并运用和发展已有的金属切削以及力学理论成果,通过考虑多种非线性因素,在高速条件下模拟和分析金属的切削过程,为进一步的理论研究和工程应用提供可参考的结论。首先,在已有的对称迭代有限元-边界元耦合算法基础上,编制相应的计算程序,对平面含双周期夹杂复合材料的等效弹性性能进行了研究。由于有限元方法适合于分析非均质材料问题,而边界元方法更适合于弹性均质材料问题,因此将所分析的含双周期非均质夹杂的复合材料分解为由有限元方法求解的夹杂子域和由边界元方法求解的基体子域,并分别建立两子域的平衡方程。在满足两子域界面上位移和面力协调连续的条件下,通过迭代得到问题的解。数值算例分别对含不规则各向异性夹杂以及规则功能梯度夹杂的复合材料进行了研究,计算结果与已有的数值解进行了对比,验证了对称迭代耦合算法的正确性和有效性。其次,提出了对称迭代有限元-边界元动力学耦合算法,并通过ABAQUS中用户子程序UEL接口,在商业软件ABAQUS平台上实现了耦合算法的运行,成功地将边界元法与ABAQUS软件结合在一起,使得用户不仅可以受益于ABAQUS强大的前处理和后处理功能,又可以更好地处理有限元不擅长而边界元可以解决的问题,例如无限域系统问题或者高应力集中问题。通过这种二次开发技术,用户一方面可以受益于软件通用的平台,另一方面可以结合特定的专业问题来建立符合自己问题的模型。而且单个或多个子程序与整个程序相比更易于维护。数值算例对弹塑性动力学问题以及无限域问题进行了研究,证明耦合算法嵌入到ABAQUS软件的可行性。最后,实现了物质点方法与边界元方法的耦合,并将其应用于高速金属切削问题中。切削过程中,剧烈的弹塑性变形只发生在切屑产生过程中以及加工表面以下局部区域,离加工表面较远的下方区域仅仅发生弹性变形。基于模型的这个特点,开发了物质点和边界元耦合算法并将其应用到正交金属切削模型中,使得物质点模拟发生严重变形的区域,而边界元法模拟远离加工表面的弹性区域。数值算例运用耦合算法对钛合金(Ti6A14V)进行了不同速度下的切削模拟,模拟结果与实验结果进行了对比,并对不同速度下的切屑形态、切削力以及切削温度进行了分析。
[Abstract]:High speed cutting technology has the characteristics of high production efficiency and high machining precision, so it has been paid more and more attention since its concept was put forward, and has become a new hot topic.Compared with the traditional cutting technology, the numerical method can not only overcome the shortcomings of the test method, but also realize the quantitative analysis of the high-speed cutting process, and the investment is less and the period is short, so it is favored by many researchers.In this paper, the numerical methods such as finite element method, material point and boundary element are studied. Combining their advantages and disadvantages, the coupling technique of numerical method is established, the corresponding program is developed, and the existing results of metal cutting and mechanics theory are applied and developed.By considering a variety of nonlinear factors, the cutting process of metal is simulated and analyzed at high speed, which provides a reference conclusion for further theoretical research and engineering application.Firstly, based on the existing symmetric iterative finite element and boundary element coupling algorithms, the equivalent elastic properties of planar composites with double periodic inclusions are studied by a corresponding calculation program.Because the finite element method is suitable for the analysis of heterogeneous material problems, the boundary element method is more suitable for the elastic homogeneous material problem.Therefore, the composite materials with biperiodic inhomogeneous inclusions are decomposed into two subdomains: the inclusion subdomains solved by the finite element method and the matrix subdomains solved by the boundary element method, and the equilibrium equations of the two subdomains are established respectively.The solution of the problem is obtained by iterative method under the condition that displacement and surface force are coordinated and continuous at the interface of two subdomains.Numerical examples of composite materials with irregular anisotropic inclusions and regular functional gradient inclusions are studied. The results are compared with the existing numerical solutions to verify the correctness and effectiveness of the symmetric iterative coupling algorithm.Secondly, a symmetric iterative finite-boundary element dynamic coupling algorithm is proposed, and the coupling algorithm is implemented on the commercial software ABAQUS platform through the user subprogram UEL interface in ABAQUS. The boundary element method is successfully combined with the ABAQUS software.Not only can users benefit from ABAQUS's powerful preprocessing and post-processing functions, but also they can better deal with problems that the finite element is not good at and boundary elements can solve, such as infinite domain system problems or high stress concentration problems.Through this secondary development technology, users can benefit from the common platform of software on the one hand, and build the model according to their own problems on the other hand, combining with specific professional problems.And a single or more subroutines are easier to maintain than the whole program.Numerical examples are used to study the elastoplastic dynamics problem and infinite domain problem, and the feasibility of embedding the coupled algorithm into ABAQUS software is proved.Finally, the coupling of material point method and boundary element method is realized and applied to high speed metal cutting.In the cutting process, the severe elastic-plastic deformation occurs only in the process of chip generation and the local area below the machined surface, and only elastic deformation occurs in the lower region far from the machined surface.Based on this characteristic of the model, the coupling algorithm of material point and boundary element is developed and applied to the orthogonal metal cutting model, which makes the material point simulate the region with serious deformation, and the boundary element method is used to simulate the elastic region far from the machined surface.A numerical example is used to simulate the cutting of titanium alloy Ti6A14V at different speeds. The simulation results are compared with the experimental results. The chip shape, cutting force and cutting temperature at different speeds are analyzed.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG506.1

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