Suppression Of Self-excited Vibration Research Articles

Stability analysis of 2-DOF milling dynamics for simultaneously varying tooth pitch and spindle speed with helix angle effect

Suppression of self-excited vibrations in their design and incipient stages is vital for assuring surface finish and machining efficiency in the precision machining process. Various cutting vibration suppression methods (e.g., variable tooth pitch and variable spindle speed) have been designed for suppressing regenerative chatter. However, variable parameter-based cutting vibration suppression models have mostly been developed separately with the other parameter assumed to be constant. In addition, these methods failed to provide detailed helix angle information required by a machining practitioner to determine which helix angle degree or group of helix angle degrees would have matched the stability of milling cutters. Moreover, only a single degree of freedom (1-DOF) milling system was adopted; thus, these methods cannot account for two degrees of freedom (2-DOF) and higher milling system. This study proposes a helix angle-based 2-DOF milling model with simultaneous tooth pitch and spindle speed variation to deal with these aforementioned problems. Experimental results showed that the proposed model can be effectively and efficiently applied to the prediction of the regenerative chatter stability for not only 1-DOF but also 2-DOF milling system. Empirical comparisons indicated that the proposed model outperformed the existing methods in stability prediction, while also offering stable area enlargement capability that facilitates cutting vibration suppression. A numerical example is presented to illustrate the usage of the proposed model.

Suppression of Self-Excited Vibrations in Rotating Machinery Utilizing Leaf Springs

When rotating machinery is operated above the major critical speed, self-excited vibrations appear due to internal friction of the shaft. Internal frictions are classified into hysteretic damping due to the friction in the shaft material and structural damping due to the dry friction between the shaft and the mounted elements. In this paper, a method to suppress the self-excited vibration using leaf springs are proposed. The structural damping is considered as the internal damping. The characteristics of a rotor with leaf springs are investigated systematically by using simulative and theoretical analyses. The validity of the proposed method is also proved by experiments.

Suppression of Self-Excited Vibration by Compensating the Unstable Force of Oil Film Bearing Utilizing Electro-Magnetic Actuator

Suppression of Self-Excited Vibration by Compensating the Unstable Force of Oil Film Bearing Utilizing Electro-Magnetic Actuator

Suppression of self-excited vibrations by a random parametric excitation

Previous theoretical and experimental studies have shown that some vibrating systems can be stabilized by zero-averaged periodic parametric excitations. It is shown in this paper that some zero-mean random parametric excitations can also be useful for this stabilization. Under some conditions, they can be even more efficient compared to the periodic ones. Two-mass mechanical system with self-excited vibrations is considered for this comparison. The so-called bounded noise is used as a model of the random parametric excitation. The mean-square stability diagrams are obtained numerically by considering an eigenvalue problem for large matrices.

Beneficial Effect of Noise in Suppression of Self-Excited Vibrations

We discuss the possibility of full suppressions of self-excited vibrations by noise. Recently, periodic excitations have been intensively studied for this aim. We compare the used periodic and random noise excitations in the case of a two-mass system. It is shown that the random noise excitations can be more efficient under certain conditions. The telegraphic process is used as the source of noise. The mean-square (energetic) asymptotic stability of the system is a tool in study of the suppression. The stability charts are presented for different values of the transition rate of the telegraphic noise.

1826 平板に発生する自励振動の低減に関する研究(G04-4 免震および振動特性II,G04 材料力学部門)

1826 平板に発生する自励振動の低減に関する研究(G04-4 免震および振動特性II,G04 材料力学部門)

Self-excited vibrations counteraction in machine tool - cutting process system using controllable eliminator of vibration

In the paper, the results of simulation investigations on the application of a semi-active vibration eliminator for suppression of machining chatter are presented. First, the idea of a semi-active vibration eliminator arranged in the tool – cutting system (MT–CP) is presented. Next, the results of the identification process of parameters of this system are shown. Properties of the mass-damping-spring system of the machine tool were estimated during the modal testing. A mechanistic model of the cutting process was built on the basis of results of cutting tests. Two control algorithms have been tested: one with the time-invariant model of disturbances (MD) and another with the adaptive model of disturbances. Estimation of the eliminator effectiveness in the suppression of self-excited vibrations in a MT–CP system is also included.

512 板ばねを利用した回転機械の自励振動の制振(不つりあい・自励振動,OS-4 ロータダイナミクス)

512 板ばねを利用した回転機械の自励振動の制振(不つりあい・自励振動,OS-4 ロータダイナミクス)

Dynamic response of a workpiece in turning with continuously varying speed

In order to study the influence of workpiece speed variation on the dynamic response of a workpiece in turning operations, this paper develops a finite element model to describe the lateral vibration of a rotating Euler-beam, in which both axial force and damping effect are included and the workpiece speed changes continuously and periodically. A simplified cutting force model which depends on the feed-rate and workpiece deflection is used along with the proposed finite element model. To solve the obtained finite element equations of a workpiece in turning, the Newmark integration scheme is employed to further discretize the time domain. At each time step the resulting nonlinear equations are solved iteratively. The numerical results show the influence of the workpiece speed variation frequency and amplitude on the dynamic response of turning operations. Also, the suppression of self-excited vibration in turning by changing the workpiece speed periodically is demonstrated by using the present analytical model.

Suppression of self-excited vibration by the spindle speed variation method

A method for the analysis of the influence of spindle speed variation on the course of self-excited vibration has been presented. Thisanalysis is based on the influence of self-frequency of self-excited vibration on the stability of machining, and dependence of this frequency on workpiece rotational speed. The influence of the spindle speed variation frequency and amplitude on chatter has been investigated.

On the Suppression of Self-excited Vibration by Servodamper

This paper deals with a technique to suppress the self-excited chatter vibration in machine tools by servodamper method proposed by the authors in the previous papers. Firstly, it is shown that the servodamper designed by applying an output feedback control theory is capable of increasing stability in cutting process against the occurrence of the chatter. Secondly, from a viewpoint of model cutting experiment, the capability of the servodamper to eliminate the chatter is presented. Thirdly, by installing the servodamper in a large-scale vertical lathe which has been required a countermeasure for the chatter occurring frequently, this paper shows the results of a cutting experiment in which a servodamper proves to be effective for eliminating the chatter under various cutting conditions.