Papers by Keyword: Self-Excited Vibration

Abstract: In this paper a horizontal vibration problem in strip rolling was studied; dynamic model was established; the mechanism of self-excited vibration was analyzed. The main reason of surface quality of strip is self-excited vibration. A vertical natural frequency and vibration mode of the rolling mill are obtained by finite element method. It lays the theoretic foundation for future researches on rolling mill vibraton.

Abstract: Aimed at the self-excited vibration of caused by unreasonable clearance in wearing ring of the Francis turbine, whole flow passage of prototype hydraulic turbine which contains the clearance in wearing ring is numerically calculated by computational fluid dynamics software CFX based on N-S equation and RNG k-turbulence model. The result shows that the flow field in front of inlet of runner is unstable extremely, even if a tiny disturbance effects on, which will be out-of-balance symmetrically in the radial direction, then the force of runner will be unbalance, which will cause vibration of the hydraulic turbine. As well as, a reasonable clearance in wearing ring of the Francis turbine will reduce the impact of the water in the inlet of the clearance, and self-excited vibration of the hydraulic turbine will eliminate.

Abstract: A two degrees of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction of brake disk and pads is built firstly, the numerical method is taken to study the impacts of damping on automobile brake groan. The calculation result shows that the variation of damping coefficient and has different influence on automobile brake groan. and all have A critical value, when damping coefficient greater or less than the critical value the brake disk and pad possess the different vibration state respectively.

Abstract: A one degree of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction is built firstly, the numerical method is taken to study the impacts of dynamics parameters on self-excited vibration. The calculation result shows that Along with the variation of system dynamics parameters such as initial velocity or normal pressure the self-excite vibration has the weakened trend or the enhanced trend, so the self-excite vibration could be controled through the control of dynamics parameters.

Abstract: A two degrees of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction of brake disk and pads is built firstly, the stability of vibration system at the equilibrium points is analyzed using the nonlinear dynamics theory. Finally the numerical method is taken to study the impacts of friction coefficient on brake groan. The calculation result shows that with the increase of kinetic friction coefficient /or the decrease of difference value between static friction coefficient and kinetic friction coefficient can prevent or restrain self-excited vibration from happening.

Abstract: The track-induced self-excited vibration is a special problem that exists in EMS (Electromagnetic Suspension) maglev systems. In this paper, the stability of the electromagnet-track coupled model is examined, and it is found that the second order vibration mode of the track may cause instability problem. To suppress the self-excited vibration, an LMS (Least Mean Square) adaptive cancellation scheme is presented, and a phase locked loop is employed to generate a reference signal for the LMS algorithm. Analysis and simulation show that the proposed adaptive cancellation algorithm is effective in suppressing the vibration with unknown frequency.

Abstract: A review of mass measurement devices developed by the author is presented. According to the measurement principles, the treated devices are classified into two types. The first type uses a dynamic vibration absorber as a device for both mass measurement and vibration control. The main advantage is no vibration transmitted into the surrounding structures during measurement. The second type uses relay feedback. The advantages are simpler mechanism and robustness against disturbances. In this article, the principles of measurement of each type are presented.

Abstract: With the intention of researching suspension’s effect on the self-excited vibration of tire, according to the characters of polygonal wear, the twist beam suspension of car PassatB5 was simplified to proper mechanical model in the method of FEA. Then, making the coupling of lateral friction self-excited vibration of tire and draw-wrest operation of lengthways pendulum arm taking the previously built friction coefficient model into account which could cause the self-excited vibration of tire, besides the velocity of car’s driving, another exciting source could be found in this model.

Abstract: In this study we attempted to suppress chatter vibration in end-milling of austenitic stainless steels with an end-mill having different helix angles. We showed there were two types of chatter vibration in end-milling with a conventional end-mill with regular helix angle. The two types of chatter vibration depend on the cutting speed. We detected these two types of chatter vibration by the developed monitoring method using laser Doppler vibrometers. We classified the two types of chatter vibration according to chatter generating tendency, frequency and vibration mode. We showed that chatter vibration generated at lower cutting speeds was regenerative chatter vibration. On the other hand, chatter vibration generated at higher cutting speeds was another type. We showed that a end-mill with different helix angles could prevent generative chatter vibration at lower cutting speeds and was also effective in suppressing chatter vibration at higher cutting speeds.