Stability analysis is a common method of studying nonlinear. Selfexcited vibrations and damping in circulatory systems. This is called aeroelastic instability, or flutter. Suppressing the unwanted vibration in a spinning disk has become an increasing challenge for mechanical engineers and researchers.
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. Optimization of sensing and feedback control for vibration. Examples of such systems where this phenomenon occurs are. A linearized lumpedparameter model of the clutch was developed to. Pdf selfexcited vibrations are observed in many technical applications. Me 563 mechanical vibrations fall 2010 12 1 introduction to mechanical vibrations 1. Summary this work describes an investigation into the frictionally induced, self excited vibrations which occur in braking systems and are generally known as squeal. 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. A simple rotating machine the rotating machinery equivalent to the single. Pdf an introduction to selfexcited oscillations researchgate.
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. All three matrices may depend on one or more parameters, here denoted by the parameter vector. Selfexcited vibrations of a flexible disk rotating on an. Theory of coupledmode selfexcited vibration of tainter gates keiko anami1, noriaki ishii2 and charles w knisely3 corresponding author. In a self excited system the excitation force is a function of the motion of the system.
Pdf experimental investigation on the avoidance of selfexcited. Spin pit experiments, full scale engine tests, as well as analytical studies have been documented regarding the above crack detection. 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. Vibration control of a spinning disk sciencedirect. 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. Selfexcited vibration of a spinning flexible disk is studied to provide design guidance for high speed. In many cases they are caused by friction as for example in disk and drum. These intermediate positions are not shown in the remainder of the figures. However, the theoretical analyses of self excited vibrations are less proposed now. With nonlinear self excitation of a twomass system deals a paper 61. The dynamic model includes coupling between vibrations of a rotating plate and waves in an incompressible viscous fluid film. Pdf an analysis of the selfexcited torsional vibrations. Usually, the frequency of selfexcited vibration is the natural frequency of the rotor.
An analysis of the self excited torsional vibrations of the electromechanical drive system article pdf available in vibrations in physical systems 27. Self excited vibration of a spinning flexible disk is studied to provide design guidance for high speed magnetic disk storage devices. Vibration is a continuous cyclic motion of a structure or a component. Then, the effects of alford force caused by the airflow excitation are researched on the stability and dynamic response. The physical model of the vibrating system consists of a nonlinear spring with. The steadystate response to harmonic excitation was formulatecl. Interestingly, modern cable stayed bridges that also suffer from a new vibration problem. Although any system can oscillate when it is forced to do so externally, the term vibration in mechanical engineering is often. 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. Even modest levels of vibration can cause extreme discomfort. Generally, engineers try to avoid vibrations, because vibrations have a number of unpleasant effects. Vibration based crack detection in a rotating disk part 2experimental results.
The control mechanism for rotating disk flutter using enclosure surfaces. Rotatingdisklike structures are a common element in rotating machines. In this paper, based on self excited vibrations by causing the structural damping, a suppressing method by using leaf springs is. These will finally result into fatigue failure of materials. Brake squeal noise is still an issue since it generates high warranty costs for the automotive industry and irritation for customers. Transition to fluidinduced limit selfexcited vibrations.
Protecting turbomachinery from self excited rotor whirl, journal of engineering for power 87, 333344. For self excited vibrations, which are of interest here, we have f. 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. 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. Self excited vibrations therefore may lead to destructive stresses. These structures allow very high rotational speeds, but come with the challenge of acoustically perceivable self excited shaft vibrations. This thesis considers a modelling and vibration analysis of thin spinning disks. The lateral regenerative interactive forces that are responsible for self excited vibrations in sawblade cutting are identified and modeled.
P is the geometric center of the disk, and g is the. This book equips the reader to understand every important aspect of the dynamics of rotating machines. The vibration of a rotating disk coupled with surrounding airflow has been of interest to many researchers in past decades. A self excited vibrations affecting on an energy consumption of. Dynamic analysis of flexible shaft and elastic disk rotor.
Vibration of rotating bladed disc excited by stationary. 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. Friction induced vibrations in moving continua and their. Active balancing and vibration control of rotating. This item appears in the following collections mechanical engineering ph. Selfexcited vibration of workpieces in a turning process. On selfexcited vibrations due to sliding friction between. Based on a systematic understanding of its theoretical foundations, selfexcited vibration. These investigations are applicable to a broad range of problems involved in the rotorstator interactions. Pdf selfexcited vibrations and damping in circulatory. A number of scientists have studied the aeroelastic stability stability to self excited vibrations of spinning. The selfexcited vibration exhibits typical signs of a dynamic instability associated with a constant friction coefficient. 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.
The oscillator itself controls the phase with which the external power acts on it. The effect of noncircular bearing shapes in hydrodynamic. Selfexcitedoscillations are encountered in a number of practical applications includingbrakes. Numerical methods for parametric model reduction in the.
Curves a, e are cases for which the mass keeps rotating. 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. The effectiveness of the proposed suppressing method is verified by experiments, simulations, and theoretical analyses. In recent years, research focused on the disk brakes which. 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. Self excited vibrations are related to the instability of the rotary system. Theory, paradigms, and research methods offers a method for analyzing any type of self excited vibration. Frictioninduced vibration of an elastic disc and a moving. 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. As the vertical vibration of the slider grows at certain conditions, it can separate from the disc.
If a rotor operates near its natural frequency, the oscillations swept up and the system becomes unstable. Eindhoven university of technology master spinning disc. Vibration analysis of shaftbladed disk system by using substructure synthesis and assumed modes. Selfexcited vibrations of a flexible disk rotating on an air film above. The excitation force in the self excited vibration maintaining the action is produced or monitored by the action itself, when the. For fe models of rotating machinery such as a disk brake, d and k are typically nonsymmetric due gyroscopic and circulatory forces. Vibration of rotating bladed disc excited by stationary distributed forces.
Aerodynamically excited vibration and flutter of a thin disk rotating at. Effect of the unstable vibration of the disc brake system. Crandallself excited vibrations of a flexible disk rotating on an air film above a flat surface. 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. It is particularly important to prevent vibrations in the disk stack assembly and in the disk head positioner. Taken the flexible shaft and elastic disk rotor system as the research object, vibration differential equations are established by the modal synthesis method. Selfexcited vibrations refer to the interruptions applied to a primarily special group compared to that of the free vibrations or forced vibrations.
Self excited vibrations of a spi nning disk research and teaching output of the mit community. On self excited vibrations due to sliding friction between moving bodies hartmut hetzler. Pdf a new treatment for predicting the selfexcited. Key parameters must be known in order to reduce it. An analysis of the selfexcited torsional vibrations of. 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.
Special regard is given to an accurate formulation of the kinematics of the frictional contact in two and three dimensions. In 26, parametric resonances in a disc with a rotating. Self oscillation is the generation and maintenance of a periodic motion by a source of power that lacks any corresponding periodicity. Literature often refers to these vibrations as oil whirl, constant tone or subsynchronous whining 27. Self oscillators are therefore distinct from forced and parametric resonators, in which the power that sustains the motion must be modulated externally. Prevention methods of selfexcited vibration due to dry. 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.
The main difficulty, however, resides in the characterisation of the internal damping coefficient. Selfexcited vibrations of rotating discs and shafts with. Optimization of sensing and feedback control for vibrationflutter. Selfexcited vibration in flexible rotating disks subjected to various transverse interactive forces. This investigation has proved that the torsional stiffness and damping of drivetrain system strongly affect amplitudes of the self excited vibrations. Based on the rungekutta method of direct integration, dynamic equations are solved successfully. 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. Stability analysis of a rotating disk with rotating and. Structural optimization for the avoidance of selfexcited. The self excited vibrations can be suppressed by using leaf springs on the rotor system with internal frictions. 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. 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. 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.
693 1239 747 1004 904 895 988 528 1493 1169 1567 810 231 18 751 1212 632 1356 1448 833 1231 831 478 1515 982 154 75 780 527 805 740 776 882 759 36