Crandallself excited vibrations of a flexible disk rotating on an air film above a flat surface. Generally, engineers try to avoid vibrations, because vibrations have a number of unpleasant effects. Modal testing of rotating systems, such as a rotating disc interacting with a stationary restraint, is considered in this paper. If a rotor operates near its natural frequency, the oscillations swept up and the system becomes unstable. It is particularly important to prevent vibrations in the disk stack assembly and in the disk head positioner.
Friction induced vibrations in moving continua and their. The selfexcited vibration exhibits typical signs of a dynamic instability associated with a constant friction coefficient. A number of scientists have studied the aeroelastic stability stability to self excited vibrations of spinning. The oscillator itself controls the phase with which the external power acts on it. On the basis of a travelling eulerbernoulli beam and a rotating annular kirchhoff plate with frictional point contact the essential properties of the contact kinematics leading to self excited vibrations are worked out. Optimization of sensing and feedback control for vibration. Rotatingdisklike structures are a common element in rotating machines. P is the geometric center of the disk, and g is the.
In this paper we consider the combined effect of rotating and nonrotating asymmetries on a rotor under nonconservative loading, motivated by technical applications in which breaking of symmetries may be used to avoid selfexcited vibrations. Rotors containing an interference fit are particularly prone to such instabilities, so the interest arises, for the formulation of a predictive mathematical model that permits a dynamical study of the system. Self excited vibrations the force acting on a vibrating system is usually independent of the motion of the system. Self excited vibrations of a spi nning disk research and teaching output of the mit community. A finite element model including two rails, one wheelset, and three disc brake units is set up to study the formation mechanism of wheel polygonalization in highspeed trains based on the point of view of frictional self excited vibration. For self excited vibrations, which are of interest here, we have f. The effect of noncircular bearing shapes in hydrodynamic. Protecting turbomachinery from self excited rotor whirl, journal of engineering for power 87, 333344.
This is called aeroelastic instability, or flutter. Prevention methods of selfexcited vibration due to dry. Result showed that breaking of symmetries of the rotating and non rotating restoring terms has opposite. Research on the vibration of an elastic disc excited by a rotating slider system has been reported in 21 25. In recent years, research focused on the disk brakes which. Spin pit experiments, full scale engine tests, as well as analytical studies have been documented regarding the above crack detection. Self excited vibration of a spinning flexible disk is studied to provide design guidance for high speed magnetic disk storage devices. The control mechanism for rotating disk flutter using enclosure surfaces. All of this background and intuition carries over into the rotating machinery world with a few important differences, especially once the rotor starts to spin.
Examples of such systems where this phenomenon occurs are. Pdf self excited vibrations in mechanical engineering systems are in general unwanted and sometimes dangerous. In 26, parametric resonances in a disc with a rotating. We consider a rotating disk with two translatory degrees of freedom describing the displacements of the center of the disk with respect to the axis of rotation and two rotational degrees of freedom describing the tilting angles with respect to the axis. This item appears in the following collections mechanical engineering ph.
Selfexcited vibrations of a flexible disk rotating on an. Based on the rungekutta method of direct integration, dynamic equations are solved successfully. Selfexcited vibration in flexible rotating disks subjected to various transverse interactive forces. Aerodynamically excited vibration and flutter of a thin disk rotating at. Dynamic analysis of flexible shaft and elastic disk rotor. Structural optimization for the avoidance of self excited vibrations based on analytical models structural optimization for the avoidance of self excited vibrations based on analytical models spelsbergkorspeter, gottfried 20101108 00.
Vibration is a continuous cyclic motion of a structure or a component. New developments also involve the stability analysis of a rotating disk subjected to multiple moving concentrated regenerative and follower interactive forces that act over a spacefixed sector. On the other hand, the flow and geometry conditions may result in a net reduction of energy in the rotor and thus exert a vibration damping influence on the rotor. Vibrations of a parametrically and selfexcited system with ideal and nonideal energy sources interactions between parametric, self, and externally excited vibrations are analysed in this paper.
In this paper, based on self excited vibrations by causing the structural damping, a suppressing method by using leaf springs is. Special regard is given to an accurate formulation of the kinematics of the frictional contact in two and three dimensions. However, the theoretical analyses of self excited vibrations are less proposed now. An analysis of the self excited torsional vibrations of the electromechanical drive system article pdf available in vibrations in physical systems 27. Special issue article self excited vibration of workpieces in a turning process xianguo han1,2, huajiang ouyang3, minjie wang1, nurhafizzah hassan3 and yuming mao4 abstract vibration occurring during machining is a major limitation to the productivity and quality of products. Even modest levels of vibration can cause extreme discomfort. All three matrices may depend on one or more parameters, here denoted by the parameter vector. Curves a, e are cases for which the mass keeps rotating. Suppressing the unwanted vibration in a spinning disk has become an increasing challenge for mechanical engineers and researchers. Selfexcitedoscillations are encountered in a number of practical applications includingbrakes. Pdf a new treatment for predicting the selfexcited.
The effectiveness of the proposed suppressing method is verified by experiments, simulations, and theoretical analyses. Pdf an analysis of the selfexcited torsional vibrations. These investigations are applicable to a broad range of problems involved in the rotorstator interactions. Selfexcited vibrations simple example the vibration of an aircraft wing can be crudely modelled as mx cx kx ax where m, c and k are the mass, damping and stiffness values of the wing modelled as a sdof system and where is an approximate model of the aerodynamic force on the wing. Vibration based crack detection in a rotating disk part 2experimental results. The transverse vibration of an elastic disc, excited by a preloaded massdamperspring slider dragged around on the disc surface at a constant rotating speed and undergoing inplane stickslip oscillation due to friction, is studied. Selfexcited vibrations and damping in circulatory systems. One of the most intuitive approaches in preventing excessive vibration in a spinning disk is to apply spacefixed restraints or vibration absorbers on the disk surface. A linearized lumpedparameter model of the clutch was developed to. After the vibration of the rotating system is measured and the imbalance in the rotating machinery is estimated, the mass center of the actuator is changed to offset.
Travelingwave modal identification based on forced or. Taken the flexible shaft and elastic disk rotor system as the research object, vibration differential equations are established by the modal synthesis method. Pdf an introduction to selfexcited oscillations researchgate. Stability analysis is a common method of studying nonlinear. Brake squeal noise is still an issue since it generates high warranty costs for the automotive industry and irritation for customers. On self excited vibrations due to sliding friction between moving bodies hartmut hetzler. This book equips the reader to understand every important aspect of the dynamics of rotating machines. Vibration of rotating bladed disc excited by stationary. Theory of coupledmode selfexcited vibration of tainter gates keiko anami1, noriaki ishii2 and charles w knisely3 corresponding author. The vibration of a rotating disk coupled with surrounding airflow has been of interest to many researchers in past decades. Self oscillation is the generation and maintenance of a periodic motion by a source of power that lacks any corresponding periodicity. Key parameters must be known in order to reduce it. In a self excited system the excitation force is a function of the motion of the system.
Vibration analysis of shaftbladed disk system by using substructure synthesis and assumed modes. Eindhoven university of technology master spinning disc. With nonlinear self excitation of a twomass system deals a paper 61. Interestingly, modern cable stayed bridges that also suffer from a new vibration problem.
Optimization of sensing and feedback control for vibrationflutter. The dynamic model includes coupling between vibrations of a rotating plate and waves in an incompressible viscous fluid film. Although any system can oscillate when it is forced to do so externally, the term vibration in mechanical engineering is often. Selfexcited vibration of a spinning flexible disk is studied to provide design guidance for high speed magnetic disk storage devices. Usually, the frequency of selfexcited vibration is the natural frequency of the rotor. A simple rotating machine the rotating machinery equivalent to the single. Effect of the unstable vibration of the disc brake system. Summary this work describes an investigation into the frictionally induced, self excited vibrations which occur in braking systems and are generally known as squeal. These will finally result into fatigue failure of materials. Pdf experimental investigation on the avoidance of selfexcited. Long after early theoretical predictions of self excited vibration limit cycles by poincar6 and lyapunov minorsky, 1947 postinstabilitythreshold limit cycles offluidinduced, self excited lateral vibrations ofrotors. Selfexcited vibrations of a flexible disk rotating on an air film above.
The component of foundation damping has the same form as the negative component of the self excitation of the basic subsystem and, furthermore, certain conditions are met. Prevention methods of selfexcited vibration due to dry friction of vertical rotor yusuke watanabe1, masaji ishii1 isromac 2016 international symposium on transport phenomena and dynamics of rotating machinery hawaii, honolulu april 1015, 2016 abstract recently, because of performance upgrades of rotating machinery, the clearance between. The lateral regenerative interactive forces that are responsible for self excited vibrations in sawblade cutting are identified and modeled. Me 563 mechanical vibrations fall 2010 12 1 introduction to mechanical vibrations 1. The physical model of the vibrating system consists of a nonlinear spring with. Read effect of highfrequency excitation on natural frequencies of spinning discs, journal of sound and vibration on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Tian department of mechanical engineering, the university of british columbia, vancouver, bc v6t 1z4, canada. In many cases they are caused by friction as for example in disk and drum.
Self oscillators are therefore distinct from forced and parametric resonators, in which the power that sustains the motion must be modulated externally. For fe models of rotating machinery such as a disk brake, d and k are typically nonsymmetric due gyroscopic and circulatory forces. Based on a systematic understanding of its theoretical foundations, selfexcited vibration. Transition to fluidinduced limit selfexcited vibrations. Vibration control of a spinning disk sciencedirect. Vibrations of a parametrically and selfexcited system. Selfexcited vibrations refer to the interruptions applied to a primarily special group compared to that of the free vibrations or forced vibrations. The steadystate response to harmonic excitation was formulatecl. Self excited vibrations therefore may lead to destructive stresses. The main difficulty, however, resides in the characterisation of the internal damping coefficient. Literature often refers to these vibrations as oil whirl, constant tone or subsynchronous whining 27. The theoretical model has been considered as a linear system and.
Selfexcited vibration of a spinning flexible disk is studied to provide design guidance for high speed. These intermediate positions are not shown in the remainder of the figures. As the vertical vibration of the slider grows at certain conditions, it can separate from the disc. This thesis considers a modelling and vibration analysis of thin spinning disks. Pdf selfexcited vibrations are observed in many technical applications. Frictioninduced vibration of an elastic disc and a moving. Pdf selfexcited vibrations and damping in circulatory. These structures allow very high rotational speeds, but come with the challenge of acoustically perceivable self excited shaft vibrations. Active balancing and vibration control of rotating. An analysis of the selfexcited torsional vibrations of. Vibration of rotating bladed disc excited by stationary distributed forces.
The excitation force in the self excited vibration maintaining the action is produced or monitored by the action itself, when the. This thesis investigates a number of major self excited vibrations and instabilities that are involved in the interactions between moving flexible components, such as rotating discs or rotating shafts, and stationary systems, such as workpieces or constrained systems. This investigation has proved that the torsional stiffness and damping of drivetrain system strongly affect amplitudes of the self excited vibrations. A practical and effective identification method called the artificial damping method adm is proposed to identify the travelingwave modes for rotating discs based on forced or self excited resonant responses measured using two displacement probes. Then, the effects of alford force caused by the airflow excitation are researched on the stability and dynamic response.
On selfexcited vibrations due to sliding friction between. Stability analysis of a rotating disk with rotating and. Structural optimization for the avoidance of selfexcited. A self excited vibrations affecting on an energy consumption of. Numerical methods for parametric model reduction in the. Self excited vibrations are related to the instability of the rotary system. Selfexcited vibration of workpieces in a turning process. Theory, paradigms, and research methods offers a method for analyzing any type of self excited vibration. Selfexcited vibrations of rotating discs and shafts with.
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