【作者】 韩贤国；

【导师】 王敏杰； Ouyang Huajiang；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 在切削加工中,细长轴工件是难加工零件之一,工件振动、加工稳定性、加工质量都是必须解决的关键问题。尤其是旋转工件表面上移动载荷的作用,工件振动与切削力的相互影响,都加剧了切削工件的振动甚至引起颤振,制约了加工质量和生产效率的提高,影响加工过程顺利进行。因此,研究切削加工过程中细长轴工件的振动规律,己成为实施和解决细长轴工件切削加工技术的瓶颈环节,是亟需解决的关键技术。本文从移动载荷作用下旋转细长轴工件振动分析的角度,针对切削加工过程中三维移动切削力作用下旋转工件的振动问题,采用理论建模与实验研究相结合的方法,开展了车削、外圆磨削加工过程中三维移动载荷作用下旋转细长轴工件的振动研究。(1)考虑了切削加工过程中移动载荷的作用,以及工件的变质量、变直径、变刚度等时变特性因素的影响,用Rayleigh连续梁振动理论,建立了切削加工过程中三维移动载荷作用下旋转细长轴工件振动的动力学模型和二阶耦合微分方程。此外,还考虑了工件表面的再生效应的影响,建立了切削加工过程中三维移动载荷作用下旋转工件振动的延时动力学模型和二阶延时微分方程。用上述模型研究了车削、外圆磨削加工过程中旋转细长轴工件的振动和颤振问题,并对工件振动方程进行求解和理论分析。(2)建立了切削加工过程中三维移动载荷作用下旋转工件振动的转子动力学模型,将切削加工过程中细长轴工件的振动简化为质量集中系统的已加工、在加工和待加工的三转子动力学系统,考虑了加工过程中工件质量和直径随时间变化,以及加工表面的再生效应对工件振动的影响。(3)开展了切削加工过程中工件振动的稳定性研究,考虑了工件和刀具两者振动相互作用的影响,用工件振动方程和质量集中系统的刀具振动方程,建立了车削工件颤振稳定性分析模型,求解车削用量临界极限值,从而避免工件颤振发生。(4)分析了切削加工过程中工件的不同夹紧方式及其边界条件的建立,并求解工件的振动方程；用理论计算方法,分析了车削、外圆磨削加工过程中切削用量、工件直径等参数对工件振动及其稳定性的影响。(5)进行了切削加工振动实验,对移动载荷作用下工件振动的理论模型进行验证；对加工中不同夹紧边界下(如车削、磨削)的工件、刀具和刀架进行模态分析及其参数识别；分别开展了车削和磨削加工过程中的工件振动、加工精度和表面粗糙度的测量实验。为了测量外圆磨削力,自主研制了外圆磨削用压电式测力装置,并对该装置进行了标定、精度分析和测力实验。本文对细长轴工件振动的研究表明,切削加工过程中移动载荷作用、旋转工件的质量和直径的时变特性对工件振动都有影响,移动载荷作用下旋转细长轴工件振动模型能够准确地反映加工过程中工件的振动规律,为今后进一步开展切削加工过程中移动载荷作用下不同截面的细长轴工件的振动研究奠定了良好的基础。更多还原

【Abstract】 A long slender workpiece is one of the most difficult-to-cut parts in machining process, in which workpiece vibration, machining stability and machining quality are the key issues to be solved. Especially, the effect of moving load acting on surface of the workpiece and interaction between workpiece vibration and cutting force exacerbate the vibration and then chatter in machining process. These reasons limit promotion of machining quality and production rate and affect the machining process also. Thus, research on vibration of a long and slender workpiece in machining process has become bottlenecks of implement and solution of machining technology for the workpiece and it is an urgent and key technology to be resolved.From the point of view of theory on vibration analysis of shaft subjected to moving loads, this paper analyzes vibration of a long and slender workpiece subjected to three dimensions moving cutting forces in machining process. Moreover, it is studied that vibration analysis of rotation workpiece is subjected to three dimensions cutting force machining process such as turning operation and external grinding process with the method of combination of theoretical model establishment and experiment.Rayleigh continuous beam vibration theory is used to establish motion equation of vibration of dynamic model for a rotation workpiece subjected to three-dimension moving cutting force. The model is used to study the workpiece vibration in turning process and external grinding. The effect of moving load and variable mass and diameter of the workpiece are considered in establishment of two-order time-varying differential equations of the workpiece for dynamic vibration analysis in turning and external grinding process. So the motion equations of the model are derived, from which numerical solutions of the equation are computed. On the basis of the model, with consideration of regenerative effect, two-order differential delay equations of model for vibration analysis of rotation workpiece are derived in machining process. The motion equations of two models are solved and used to study vibration and chatter analysis of rotation slender workpiece in turning and external grinding process.Based on vibration theory of rotor dynamics, rotor dynamics model of rotating workpiece subjected to the three-dimensions cutting force is built in machining process, in which the workpiece is simplified as a concentrated mass system consisted of three rotors, i.e., the machined, the machining, the unmachined part of shaft, respectively. The model is used to study vibration of workpiece in turning and external grinding operation. Moreover variable mass and diameter of workpiece is considered in machining process. So the equations of motion of rotation shaft are derived.In order to research machining stability, stability of turning process is discussed, in which combination of the motion equations of workpiece and one degree of freedom motion equation of tool is used and interactive influence of cutter post and workpiece. And a predictive stability model of choosing critical values of machining parameters is established for prediction of chatter in turning process.According to different clamped conditions for workpiece in machine tools, vibration equation of rotation shaft is numerically solved in corresponding boundary conditions and initial values, in which the effect of cutting parameters such as depth of cut, rotation speed, diameter of workpiece, etc. on dynamic response of vibration and stability of cutting are discussed in turning process and external grinding operations.Modal test of workpiece are made in boundary conditions of machine tool for the turning and external grinding operation. Identification of modal parameters for workpiece is conducted. Moreover, fundamental Frequency and modal parameters is tested in different cutting condition. Stiffness of chucked end as elastic support end in turning process is computed.According to requirement of vibration test for grinding process, three-dimension dynamometer of piezoelectric on external grinding is designed and installed. Static calibration of the dynamometer is conducted and then the dynamometer is used to test cutting force in grinding process. Meanwhile, vibration and machined surface roughness of workpiece is tested in machining process such as turning and external grinding. Numerical analysis and experimental verification of dynamic response of vibration, stability model, surface roughness model of turning and external grinding for workpiece is conducted in turning and grinding process.The research on a long and slender workpiece vibration shows the variable mass and diameter of the workpiece has an obvious effect on the vibration of workpiece and the model is exactly able to describe vibration of the workpiece subjected to the moving load in machining process. The results lay a good foundation for the further research on the rotation workpiece vibration with different cross-sections subjected to the moving load in machining process.更多还原