飞刀切削机床的空气动力学行为及其动态响应的研究

发布时间：2018-01-21 23:22

本文关键词： 超精密飞切机床动力学特性外部气动力轴承刚度　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：在惯性激光核聚变装置中,用于倍频转换的KH2PO4(Potassium dihydrogen phosphate,KDP)晶体加工表面质量要求极高,这对用于晶体加工的超精密机床性能提出了很高的要求。在超精密飞刀切削机床加工过程中,机床的动态特性将会直接影响工件的三维表面形貌。传统研究认为,机床的振动对加工表面的影响主要为切削力激振下主轴刀尖的振动。然而,由于飞刀切削是断续切削,并且主轴的转速很高,刀架离工件距离较小,在加工过程中,外部空气将会对主轴刀架下表面和工件上表面产生法向气动力,从而直接导致机床的振动,对加工表面形貌产生重要影响。本文主要针对这一问题展开研究,对进一步深入揭示飞刀切削加工表面的形成机理具有一定的理论意义。首先,针对立式超精密飞切机床,建立了机床外部空气流体场分析模型,基于计算流体力学和有限体积法,分析了刀架和溜板气动力。并研究了不同主轴转速和横向进给方向上不同加工位置的刀架和溜板气动力,分析了主轴转速和加工位置对气动力的影响。其次,建立了立式超精密飞切机床轴承气膜有限元模型,分析了气浮主轴的静态特性。基于弹簧等效法,采用轴承刚度的计算结果,建立了机床整体的动力学模型。并通过机床主轴的模态实验,验证了机床动力学模型的正确性。在此基础上,分析了切削力和气动力激振下的主轴刀尖的振动,并与切削力和气动力单独作用下的刀尖振动进行比较,探讨了气动力对主轴振动的影响。在加工路径对应的溜板模型切削位置加载切削力,仿真计算了加工过程中工件上切削点的瞬时振动。再次,设计并搭建了气动力验证平台,测量了不同主轴转速下的工件气动力,分析了主轴转速对气动力的影响。测量了刀架与工件在不同距离下的工件气动力,分析了刀架与工件距离对气动力的影响。并将仿真计算和实验结果进行比较,验证了仿真模型的正确性。最后,基于立式超精密机床的动态特性研究方法,分析了卧式超精密机床的外部气动力和主轴轴承刚度。在此基础上,建立了主轴系统的动力学模型,研究了切削力和气动力激振下的刀尖振动,并分析了气动力对卧式飞切机床主轴的振动影响。
[Abstract]:KH2PO4(Potassium dihydrogen phosphate for frequency doubling in inertial laser fusion devices. The surface quality of KDPcrystal machining is very high, which puts forward a very high requirement for the performance of ultra-precision machine tools used in crystal machining. The dynamic characteristics of the machine tool will directly affect the three-dimensional surface morphology of the workpiece. The traditional research holds that the vibration of the machine tool is mainly the vibration of the spindle tool tip under the excitation of cutting force. Because the flying knife cutting is intermittent, and the spindle speed is very high, the tool holder distance from the workpiece is small, in the process of processing, the external air will produce normal aerodynamic force on the lower surface of the spindle tool holder and the upper surface of the workpiece. Thus, the vibration of machine tools is directly caused, which has an important impact on the surface morphology of machining. This paper mainly focuses on this problem. It has a certain theoretical significance to further reveal the formation mechanism of the cutting surface of the flying knife. Firstly, an analysis model of the air fluid field outside the machine tool is established for the vertical ultra-precision flying cutting machine. Based on computational fluid dynamics (CFD) and finite volume method, the aerodynamic forces of tool holder and slide plate are analyzed, and the aerodynamic forces of tool holder and slide plate in different spindle speed and transverse feed direction are studied. The influence of spindle speed and machining position on aerodynamic force is analyzed. Secondly, the finite element model of bearing film of vertical ultra-precision flying cutting machine tool is established, and the static characteristics of air-floating spindle are analyzed based on spring equivalent method. Based on the calculation results of bearing stiffness, the dynamic model of the machine tool is established, and the correctness of the dynamic model is verified by the modal experiment of the spindle of the machine tool. The vibration of the spindle tool tip under the cutting force and aerodynamic excitation is analyzed and compared with that under the cutting force and aerodynamic force acting alone. The effect of aerodynamic force on the vibration of spindle is discussed. The cutting force is loaded at the cutting position of the cutting plate model corresponding to the machining path, and the instantaneous vibration of the cutting point on the workpiece during the machining process is simulated and calculated. An aerodynamic verification platform is designed and built to measure the aerodynamic force of the workpiece under different spindle speeds and analyze the influence of the spindle speed on the aerodynamic force. The aerodynamic forces of the workpiece at different distances between the tool holder and the workpiece are measured. The influence of the distance between the tool holder and the workpiece on the aerodynamic force is analyzed, and the simulation results are compared with the experimental results to verify the correctness of the simulation model. Finally, the research method based on the dynamic characteristics of the vertical ultra-precision machine tool is presented. The external aerodynamic force and spindle bearing stiffness of the horizontal ultra-precision machine tool are analyzed. On the basis of this, the dynamic model of the spindle system is established, and the cutting force and aerodynamic vibration of the blade tip are studied. The effect of aerodynamic force on the vibration of horizontal flying cutting machine spindle is analyzed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG501

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