【作者】 黄志刚；

【导师】 柯映林；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2003， 博士

【摘要】 整体结构件的数控加工厂变形是航空制造技术所面对的最突出问题之一，严重地阻碍了航空制造业的发展。因此，实现航空整体结构件数控加工变形的预测和控制具有重大的理论意义和工程应用价值。鉴于问题的复杂性，本文通过机械制造、固体力学和有限元法等多学科的深入交叉，采用实验研究、理论建模和软件分析相结合的方法，从余属切削原理入手，分别建立了金属下交切削加工的热力耦合有限元模型和三维铣削加工的有限元模型，对铣削加工变形的机理、变形抑制的理论和工艺措施进行了广泛、深入的研究。 本文，在第一章首先阐述了论文研究的背景和意义。其次总结了国内外航空整体结构件的数控加工概况，并对其加工变形产生的原因进行了详细的分析。进而，在详细论述本领域国內外研究现状的基础上，结合国家自然科学基金和国防型号工程项目，提出了航空整体结构件铣削加工有限元模拟的研究目标和技术路线。最后给出了本论文的研究内容和总体框架。 第二章基于金属切削原理，建立了金属正交切削加工的热力耦合有限元模型，对有限元模拟所涉及的若干关键技术进行了研究，提出了几何—应力的切屑分离标准，并讨论了切削加工的模拟过程。最后，对所建立的有限元模型进行了实验验证。 第三章提出了基于正交切削加工有限元模型的铣削参数优化方法。在铣削加工力学模型建立的基础上，对铣削加工模拟获得的一些基本物理量进行了分析、讨论，并对铣削加工产生的已加工表面残余应力，以及铣削刀具前角和铣削用量的优化进行了模拟研究。 第四章基于M．C．Shaw提出的切屑可以视为一系列平行正交切片的思路，建立了基于正交切削加工模拟数据的切削力与切削温度的计算模型。通过将斜角切削加工时的切屑离散为数个切片，实现了三维切削加工与平面正交切削加工之间的相互映射，从而为斜角切削加工的切削力与切削温度的求解提供了一种新的思路，为进一步实现三维的铣削加工模拟提供了输入参数。 第五章针对航空整体结构件铣削加工变形这一复杂的制造难题，建立了三维铣削加工的弹塑性热力耦合有限元模型，研究了材料模型、残余应力施加、刀具动态载荷、材料去除等铣削加工模拟所涉及的关键技术。最后，对三维铣削加工的模拟过程进行了详细的论述。 第六章基于对航空框类结构件铣削加工变形产生原因的分析，分别研究了毛坯初始残余应力释放以及多因素耦合对零件加工变形规律的影响。通过将多因素耦合浙江大学博士学位论文模拟结果与比例件加工实验进行比较，证明了三维铣削加工有限元模型的正确性。在其它加工条件确定的前提下，对不同隔框加工顺序进行了模拟，确定了变形最小的隔框加工顺序。 第七章对全文工作进行了概括总结，并对有待进一步研究的内容进行了展望。关键词:整体结构件;加工变形;热力祸合;正交切削;铣削加工;有限元模拟; 生死单元;切屑成形;切屑分离标准;加工顺序;残余应力;切削力;切 削温度;优化;动态切削载荷;加工路径本论文研究得到了国家自然科学基金项目、国防军工项目、教育部博士点基金项目等国家重点课题的资助更多还原

【Abstract】 The distortion of monolithic component due to CNC machining is one of the most striking problems that aviation manufacturing technologies have to face up to, and seriously hinders the process of the aviation industry. So, it has great value in academic and engineering area to realize the prediction and manipulation of monolithic component machining distortion. The research of monolithic component involves many disciplines, such as mechanical manufacture, solid mechanics, finite element method and etc. In view of the complex nature of problem, a method combining experiment with theoretical modeling and computer analysis is proposed in this dissertation. Then, beginning with the metal cutting principle, two finite element models are constructed, one is a coupled thermo-mechanical finite element model with regard to plain strain orthogonal metal cutting and the other is a three-dimensional finite element model used to simulate milling process. Furthermore, these two models are used to study on the mechanism of milling distortion, the theory of restraining distortion and the process measure.Firstly, the background and significance of this dissertation are elaborated. Then, the current situation of CNC machining of aerospace monolithic component at home and abroad is summarized, and the main factors resulting in machining distortion are analyzed deeply. Furthermore, funded by the subject of national nature science fund and national defense model engineering, the research objective and technical route of this dissertation are advanced, and its research contents and overall structure are listed.In chapter 2, based on metal cutting principle, a coupled thermo-mechanical finite element model is constructed with regard to plain strain orthogonal metal cutting. In addition, several special finite element techniques, such as the chip separation criteria and friction model, have been implemented to improve the accuracy and efficiency of the finite element simulation. A chip separation criterion based on stress failure and geometry is proposed to realize separation of twin nodes. Then, simulating process of metal cutting is discussed. Afterwards, the above finite element model is proved to be right by comparing experiment data with simulation results.In chapter 3, an optimum method of milling parameter based on orthogonal cutting finite element model is proposed. According to mechanics analysis for milling process, a FEM for milling simulation is established. Then, some basic physical parameters, such as stress, strain, temperature and etc, are analyzed and discussed. After that, both residual stress of finished surface caused by milling process and optimization of milling tool rake and milling parameter are researched by simulation.In accordance with M.C.Shaw’s idea that chip could be regard as a series of parallel orthogonal slices, a computing model of cutting force and cutting temperature based on orthogonal cutting simulation results is constructed in chapter 4, and a map is established between the three-dimensional cutting process and planar orthogonal cutting process. Thismethod can be used to solve cutting force and cutting temperature of oblique angle cutting process, and provide input parameters for further simulation of 3D cutting process.So as to reveal the reason to bring in distortion due to milling and control it further, an elastic-plastic finite element model is established to simulate the aircraft integrated-components milling process in chapter 5. Some key techniques, including material model, initial residual stress model, dynamic cutting load model and material removal model, are explored and researched deeply. After that, a new flowchart for simulating the milling process is proposed.In chapter 6, the machining distortion law of part caused by release of initial residual stresses and multi-factors coupling are researched. Comparing the result of multi-factors coupling simulation to experiment, the FEA model is proved to be right and can be used to predict distortion of aircraft integrated-part due to milling更多还原