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The selfexcited vibration frequency was measured by a newly developed method based on registering the frequency only in the resonance modes which set in when the sphere and pipe vibration eigenfrequencies coincide.


The major nondimensional parameters characterizing the phenomenon considered were revealed, and a universal relation between them and the nondimensional selfexcited vibration frequency was established with acceptable accuracy.


Such geometric imperfections induce flow distortions which can, in turn, cause selfexcited vibration of the rotor, or rotordynamic instability.


At the same time, stability of zero solution of Jeffcott rotor whirl equation and stability of selfexcited vibration are studied.


On the problem of selfexcited vibration quenching by means of parametric excitation

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 Whenever a cutting process becomes unstable. chatter amplitude will rapidly build up and then will stablize itself at a certain value. To explain the reasons of chatter amplitude stability and to predict the amplitude of a stablized chatter vibration are of practical importance with a view to reduce machine tool vibration. But unfortunately these problems can't be solved in the light of traditional linear chatter theory of machine tools since the linear theory, based on the assumption of "small amplitude," cannot... Whenever a cutting process becomes unstable. chatter amplitude will rapidly build up and then will stablize itself at a certain value. To explain the reasons of chatter amplitude stability and to predict the amplitude of a stablized chatter vibration are of practical importance with a view to reduce machine tool vibration. But unfortunately these problems can't be solved in the light of traditional linear chatter theory of machine tools since the linear theory, based on the assumption of "small amplitude," cannot explain the phenomena in a fully established chatter process, such as amplitude stability.An important inevitable nonlinearity in cutting processes, which is due to the cutting tool leaving the workpiece material when chatter amlitudes are sufficiently large, is taken into consideration in this part of the paper, and a nonlinear differential equation of machine tool chatter is derived. The approximat (?)ution of the equation gives explanation of amplitude stability and of the effect of cutting condition on the stablized chatter amplitude.A more perfect theory of machine tool chatter and the experimental evidence of the theory will be presented in Part II of this paper.  本文提出金属切削机床在生产过程中发生自激振动(即颤振)的一个非线性理论模型.该模型能够说明和预测关于机床颤振的一些重要现象,这些现象是传统的线性理论所无法解释的. 本文第一部分把机械加工中,当振幅足够大时必然要出现的一个因素:刀刃运动轨迹的一部份越出工件之外,纳入考虑,建立了机床颤振的非线性微分方程,此方程的解说明了振幅稳定性的原因,并说明各种条件下稳定振幅的大小.  On the basis of a mathematical model for the dynamics of grinding process,the forced vibration due to external disturbances as well as the selfexcited chattering owing to inherent feedback of the process are discussed, and their influences upon the ground surface waviness are studied. An approach to the diagnosing of machine tool failures by means of analyzing the finished workpiece quality is indicated. Thereby, ways to reduce and toeliminate ground surface wavinese are proposed.  本文以磨削加工过程的动态数学模型为基础,就外界干扰所引起的强迫振动以及内在反馈作用下产生的自激振动,对磨削加工后工件表面波纹度的决定性影响,进行了深入的研究。从而探索了由工件加工质量分析机床设备是否异常的方法,解决了实际中的问题,提出了降低和消除磨削波纹度的方向和措施。  It is discussed in this paper that the ring frame spindle(?) when subjected to forcedvibration due to eccentric rotating load,will be disturbed by a tangential force Tproduced by such factors as the inner hysteresis friction of the spindle blade materialand the lubricating oil effect around the bottom portion of the spindle etc.If theforce T is greater than the inherent damping force in the spnidle,the selfexcitedvibration of frequency p with an increasing amplitude will occur and then its movementbelongs in... It is discussed in this paper that the ring frame spindle(?) when subjected to forcedvibration due to eccentric rotating load,will be disturbed by a tangential force Tproduced by such factors as the inner hysteresis friction of the spindle blade materialand the lubricating oil effect around the bottom portion of the spindle etc.If theforce T is greater than the inherent damping force in the spnidle,the selfexcitedvibration of frequency p with an increasing amplitude will occur and then its movementbelongs in unstable.But the damping force in the spindle system is also excitedto increase simultaneously,so,when these two forces become in equilibrium,then aselfexcited vibration with a steady amplitude and of frequency ω_n will occur withthe result that spindle runs at crisis of stability.The spindle blade top will thendescribe a cycloidal locus.This phenomenon appears only when the rotating speedof the spindle is higher than its first critical speed.The chief factors causing theselfexcited vibration can now be traced from the character of the experimentallocus of vibration of the spindle blade top.  本文论述环锭纺细纱锭杆在强迫振动过程中受到材料内摩擦效应、润滑油膜效应等形成的切向力的干扰;当该力大于锭杆振动系统特有的切向阻尼力时,锭杆产生频率 p 的增幅自激振动,其运动属于不稳定。但因锭子结构里的阻尼力同时也被激增,当两力成平衡时锭杆就转变为频率ω_n 的等幅自激振动,其运动属于稳定极限情况,锭端轨迹呈现摆线。这种现象只在锭速高于第一临界转速时才出现,并可以根据锭端轨迹的特征来判别自激振动的产生因素。   << 更多相关文摘 
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