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题名: 航空透明件模具高速切削工艺参数优化及其振动特性的研究
其他题名: Research of Parameters Optimization and Vibration for Aviation Transparent Piece Mould in High-speed Machining
作者: 付涛
导师: 刘伟军
分类号: TG506.1
关键词: NAK80 ; 力学性能 ; 高速数控加工 ; 切削振动 ; 参数优化
页码: 111页
学位专业: 机械电子工程
学位类别: 博士
答辩日期: 2013-05-25
授予单位: 中国科学院沈阳自动化研究所
作者部门: 装备制造技术研究室
中文摘要: 大型精密模具是重要的工艺装备,直接影响到产品的更新换代能力,在现代制造业中占有举足轻重的作用;其加工制造能力则是国家制造水平的综合体现,具有巨大的经济和社会效益。高速数控加工作为现代制造中的标志性加工技术,在航空航天、运载工具和动力装备等领域占据着主导地位。随着国内高速数控加工中心及高档数控机床等硬件设备的日趋成熟和普及,围绕大型精密模具高速数控加工中的一些深层次问题便逐步显现出来,这突出表现在数控机床的高速加工特性与传统加工方法之间的矛盾。本文将主要围绕航空透明件模具高速切削参数优化及其振动特性分析的相关问题,从模具材料的力学性能出发,通过大量的理论和试验分析,全面系统地对高速切削中的工艺参数优化及其切削振动问题做深入研究。 1.为加深对航空透明件模具钢材料NAK80的认识、了解其力学性能,利用电子材料试验机、热模拟试验机和分离式Hopkinson压杆装置,对材料在较宽温度范围和不同应变率条件下的力学性能开展了系列的试验研究,获得了材料在不同温度和应变率耦合作用下的应力—应变曲线,从中探讨了温度和应变率对NAK80塑性流动应力的影响机制。 基于试验数据,拟合了描述该材料力学性能的Johnson-Cook本构模型,并运用该模型对不同温度和不同应变率条件下材料的流变应力进行预测。与试验数据的比较结果表明:该模型能够较好地描述和预测塑料模具钢NAK80的塑性流变行为。 2.针对高速切削系统结构和受力都比较复杂的特点,对空转、空进给条件下和高速切削过程中主轴和工件的振动进行检测并进行对比分析。首先通过模态分析方法获得了VMC0645H机床在高速切削前后的主轴固有频率,然后通过试验首次定量地描述并系统地分析了塑料模具钢NAK80在不同切削用量条件下主轴和工件的振动变化规律,探讨了引起切削振动的内在原因。 这些对切削振动的研究,对揭示切削振动机理,检测和分析切削振动,从而采取有效措施减少切削振动、提高加工表面质量奠定了基础。 3.实际高速切削过程受很多未知因素的影响,针对这种不确定性,对塑料模具钢NAK80的切削性能进行研究并应用基于灰色关联分析的方法将优化多目标转换为以灰色关联度为衡量指标的单目标,最终优化了切削工艺参数并得出了主轴转速、每齿进给量和切削深度对各目标的影响规律。此外,特别提出了将主成分分析方法与灰色关联分析方法相结合,用于评价多目标的权重,使优化目标在不受主观因素影响的前提下体现了各自的重要程度。 该方法使用范围广,不仅仅是铣削,对于磨削、车削、钻削等同样适用;更进一步,还可以推广到各种加工工件材料。本文的基于灰色关联分析和主成分分析的方法还可以考虑更多地加工工艺参数,如切削液浓度、刀具参数等,也可以考虑更多地响应,如刀具磨损、表面粗糙度、材料去除率和机床功率等,从而优化更多地加工工艺,为刀具制造商和数控加工人员寻找最优切削方案奠定了基础。 4. 针对切削过程单目标优化的缺陷,本文提出了一种基于多目标优化的切削工艺参数优化方法。该方法以切削力、表面粗糙度和材料去除率为优化目标,利用多目标进化算法得到优化的工艺参数组合,从而指导加工过程,一定程度上解决了获得最佳切削工艺参数的研发周期和成本。 为建立切削过程参数优化的目标函数,通过试验建立了切削力、表面粗糙度和材料去除率的数学模型,并对模型的精确度进行验证。此外,通过对模型的方差分析,得到了切削速度、每转进给量和切削深度及其之间的交互作用对目标的影响规律。在综合比较了已有的多目标求解方法基础上,针对本文目标函数的特性,选择解算效率较高的非支配遗传算法(NSGA-II)和最新的基于分解的多目标进化算法(MOEA/D)作为切削参数优化的求解方法,得到优化后的Pareto最优解集,并对优化后工艺参数组合进行了试验验证。该方法逻辑性较强,以多个切削目标的综合最优为最终的优化目标,为切削参数优化提供了一种新的思路和方法。
英文摘要: Large precision mould is one of the most important equipments. It has a direct impact on the upgrading of products and plays a significant role in the modern manufacturing industry. The capacity of producing large precision moulds is a comprehensive reflection of the national manufacturing level and has great economic and social benefits. High-speed CNC machining as a symbol of modern manufacturing has dominated the precise complex surface machining in aerospace, vehicle, power-equipment and other fields. With the development of the high-speed CNC machine center and high grade CNC machine, some deep-seated problems on high-speed machining (HSM) of large precision mould are beginning to show up. The conflict between the quality of HSM and the additional machining manner is an outstanding manifestation. This paper will mainly focus on parameters optimization and vibration analysis in HSM of large precision mould. Departure from the mechanical properties of the mould steel NAK80, through a lot of theoretical and experimental analysis, a comprehensively systematic research is made to parameters optimization and vibration analysis in cutting process. 1. In order to deepen the understanding of mould steel NAK80, an experiment of mechanical behaviors test is carried out at a wide temperature range and high strain rates with the electronic material test machine, thermal simulator and Split Hopkinson Pressure Bar. The stress-strain curves of NAK80 under temperature and strain rate actions are obtained. On the basis, the mechanism of effect of temperature and strain rate on the plastic flow stress of material is discussed. Moreover, the Johnson-Cook constitutive model, fitted by the stress-strain curves which are obtained from experiments, predicts the plastic flow behavior of mould steel NAk80 on the condition of different temperatures and strain rates. The comparison result with the experiment shows that the fitted model can provide a satisfactory prediction and description for the plastic flow behavior of NAK80. 2. Considering the complexity of the structure and the force in HSM system, the experiments, including the blank of spindle and high-speed machining, are designed and carried out to investigate the vibration of the spindle and workpiece thoroughly. Firstly, the natural frequency for the spindle of the lathe, whose type is VMC0645H, is obtained by modal analysis method before and after the high-speed cutting. Then, the changing law of the vibration of spindle and workpiece under different cutting conditions for NAK80 is firstly quantificationally described and systematically analyzed through a series of experiments. Moreover, the internal reasons caused by cutting vibration are also discussed. These results laid a foundation not only for taking effective measures to reducing cutting vibration and improving the quality of the machined surface, but also for researching, detecting and analyzing cutting vibration and revealing the mechanism of vibration. 3. High-speed cutting process is always affected by many unknown factors. Aiming at this uncertainty, the cutting performance of the plastic mould steel NAK80 is researched. The paper converts the multi-objectives in the cutting process to a single objective of grey relational grade by using grey relational analysis and ultimately optimizes the cutting parameters. Furthermore, the effect of the spindle speed, feed per tooth and depth of cut on responses is also investigated. Moreover, the principal component analysis is applied to evaluate the weighted values so that their relative importance can be described properly and objectively. This method is not just suitable for milling, but also for grinding, turning and drilling. Furthermore, it can be also extended to a variety of materials. Therefore, tool manufacturers and CNC machining workers can use the method to find the optimum cutting scheme. The method in this paper can be further improved to consider more cutting parameters, such as the concentration of cutting fluid, the parameters of cutting tool; One can also consider more response variables, such as tool wear, surface roughness, material removal rate, machine power and so on in order to optimize more processing technology. 4. For the defect of single-objective optimization in HSM process, a method based on multi-objective evolutionary algorithm is explored. In order to guide the machining process, shorten the cycle time and cost in obtaining optimum cutting parameters to some extent, the method optimizes the combination of cutting parameters by using two multi-objective evolutionary algorithms with cutting force, surface roughness and removal rate as the optimization objectives. In order to establish the objective functions of the cutting parameters optimization, an orthogonal experiment of NAK80 for milling is carried out with cutting speed, feed rate and depth of cut, all of which are considered as relevant variables. Moreover, the accuracy of the three models is verified through variances of analysis and the effects of cutting parameters on the objectives are also got. Based on a comprehensive comparison of the existing multi-objective solving methods, two more efficient evolutionary algorithms, including non-dominated genetic algorithm (NSGA-II) and multi-objective evolutionary algorithm based on decomposition (MOEA/D) are selected as the methods for sloving the problem in cutting process. The Pareto optimal solution sets are obtained and verified by experiments finally. The methods proposed here have a stronger logic. They put the comprehensive optimization of several cutting objectives as a goal and provide a new way of thinking and methods for the optimization of cutting parameters.
语种: 中文
产权排序: 1
内容类型: 学位论文
URI标识: http://ir.sia.cn/handle/173321/10754
Appears in Collections:装备制造技术研究室_学位论文

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Recommended Citation:
付涛.航空透明件模具高速切削工艺参数优化及其振动特性的研究.[博士学位论文].中国科学院沈阳自动化研究所.2013
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