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Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.


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TL;DR: In this paper, a theoretical and experimental approach was used to investigate the motion and effectiveness of a self-compensating dynamic balancer (SCDB), which is a device intended to minimize the effects of rotor imbalance and vibratory forces on a rotating system during normal operation.
Abstract: A theoretical and experimental approach was used to investigate the motion and effectiveness of a Self-Compensating Dynamic Balancer (SCDB). This is a device intended to minimize the effects of rotor imbalance and vibratory forces on a rotating system during normal operation. The basic concept of an automatic dynamic balancer has been described in many U.S. patents. The SCDB is composed of a circular disk with a groove containing massive balls and a low viscosity damping fluid. The objective of this research is to determine the motion of the balls and how this ball motion is related to the vibration of the rotating system using both theoretical and experimental methods. The equations of motion the balls were derived by the Lagrangian method. Static and dynamic solutions were derived from the analytic model. To consider dynamic stability of the motion, perturbation equations were investigated by two different methods: Floquet theory and direct computer simulation. On the basis of the results of the stability investigation, ball positions which result in a balance system are stable above the critical speed and unstable at critical speed and below critical speed. To determine the actual critical speed of the rotating system used in the experimental work, a modal analysis was conducted. Experimental results confirm the predicted ball positions. Based on the theoretical and experimental results, when the system operates below and near the first critical speed, the balls do not balance the system. However, when the system operates above the first critical speed the balls can balance the system.

59 citations

Journal ArticleDOI
TL;DR: In this article, the impact of axially moving single-layered graphene sheet (SLGS) subjected to magnetic field is investigated and the results indicated that the critical speed of moving SLGS is strongly dependent on the moving speed.
Abstract: In the present research, vibration and instability of axially moving single-layered graphene sheet (SLGS) subjected to magnetic field is investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. Third order shear deformation theory (TSDT) is utilized due to its accuracy of polynomial functions than other plate theories. Motion equations are obtained by means of Hamilton’s principle and solved analytically. Influences of various parameters such as axially moving speed, magnetic field, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of SLGS on the vibration characteristics of moving system are discussed in details. The results indicated that the critical speed of moving SLGS is strongly dependent on the moving speed. Therefore, the critical speed of moving SLGS can be improved by applying magnetic field. The results of this investigation can be used in design and manufacturing of marine vessels in nanoscale.

58 citations

Journal ArticleDOI
TL;DR: In this article, a dynamic model based on the traditional transfer matrix method (TMM) and Jones-Harris nonlinear rolling bearing model was proposed to study the effects of the extended structure parameters on the vibration behavior of a high-speed motorized spindle-bearing system.
Abstract: This technical brief presents a dynamic model based on the traditional transfer matrix method (TMM) and Jones-Harris nonlinear rolling bearing model to study the effects of the extended structure parameters on the vibration behavior of a high-speed motorized spindle-bearing system. The first critical speed and the dynamic stiffness of the high-speed motorized spindle-bearing system are systematically studied. A design sensitivity analysis of the structure parameters is then conducted to identify the main factor to affect the first critical speed of the spindle-bearing system. The results show that the processing condition, the shaft shoulder, the dimension of motor, and the bearing arrangement are sensitive to the spindle dynamic behavior. The TMM model of the spindle-bearing system is verified by measuring the high-speed motorized spindle overall dynamic stiffness.

58 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic pull force between the magnetic poles in the damper was analyzed theoretically, and it was shown that the damping force can decrease both the first critical speed and the critical amplitude, but increase the amplitude in a speed range between two undamped critical speeds.
Abstract: By using magnetorheological (MR) fluid in place of lubricating oil in a traditional squeeze film damper (SFD), one can build a variable-damping SFD, thereby controlling the vibration of a rotor by controlling the magnetic field. Assuming a Bingham model, the Reynolds equation for an MR fluid squeeze film is developed and solved to provide expressions for the velocity, the pressure distribution and the damping force. Electromagnetic theory is used to calculate the magnetic pull force between the magnetic poles in the damper. The mechanical properties of the squeeze film and the unbalance response characteristics of an MR fluid SFD–rigid rotor system are analyzed theoretically. An MR fluid SFD is designed and manufactured, and the unbalance response properties and control method of a flexible rotor supported on the damper are studied experimentally. The study shows that the magnetic pull force can decrease both the first critical speed and the critical amplitude; the film damping force can decrease the amplitude at the undamped critical speeds, but increase the amplitude in a speed range between two undamped critical speeds. The damper may have the best control effect to minimize the vibration within the range of all working speed by using the on–off control method.

58 citations

Journal ArticleDOI
TL;DR: In this article, an active balancing program using influence coefficient method and active balancing device of an electro-magnetic type with both simple and reliable structures were applied to the developed high-speed spindle system.
Abstract: A high-speed spindle can be very sensitive to rotating mass unbalance which has harmful effect on many types of rotating machinery. Therefore, the balancing procedure is certainly needed to reduce vibration in all high-speed rotating systems. In this study, an active balancing program using influence coefficient method and an active balancing device of an electro-magnetic type with both simple and reliable structures were applied to the developed high-speed spindle system. A gain scheduling control using influence coefficients of the reference model was proved to be effective in balancing the spindle system although its characteristics were changed. The stability of reference influence coefficients was verified by experiments with frequency response functions. The active balancing experiment of the manufactured spindle system using an active balancing program and device was also performed efficiently during the operation. As a result, controlled unbalance responses after balancing work were below the vibration limit at all rotating speed ranges including critical speeds.

58 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
202343
2022120
202182
202092
2019102