scholarly journals An Analytical Study of Self-Compensating Dynamic Balancer with Damping Fluid and Ball

1995 ◽  
Vol 2 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Jongkil Lee
Keyword(s):  
Dynamic Stability ◽  
Critical Speed ◽  
Analytical Study ◽  
Equations Of Motion ◽  
Circular Disk ◽  
Lagrangian Method ◽  
The Self ◽  
Rotating System ◽  
Stability Investigation ◽  
Low Viscosity

The self-compensating dynamic balancer (SCDB) is composed of a circular disk with a groove containing ball and a low viscosity damping fluid. The equations of motion of the rotating system with SCDB were derived by the Lagrangian method. To consider dynamic stability of the motion, perturbation equations were investigated. Based on the results of stability investigation, ball positions that result in a balanced system are stable above the critical speed with small damping (β′>3.8 case). At critical speed the perturbed motion is said to be stable for large damping (β′>2.3 case). However, below critical speed the balls cannot stabilize the system in any case.

Analytical and Experimental Analysis of a Self-Compensating Dynamic Balancer in a Rotating Mechanism

1996 ◽  
Vol 118 (3) ◽  
pp. 468-475 ◽  
Author(s):  
Jongkil Lee ◽  
W. K. Van Moorhem
Keyword(s):  
Critical Speed ◽  
Equations Of Motion ◽  
Circular Disk ◽  
Experimental Results ◽  
Normal Operation ◽  
Rotating System ◽  
Balance System ◽  
Rotor Imbalance ◽  
Low Viscosity ◽  
The Stability

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.

scholarly journals Dynamic Stability of an Elastic Rotating System: Shell-Disc-Shaft

1997 ◽  
Vol 3 (1) ◽  
pp. 33-44
Author(s):  
P. Ruge ◽  
P. Senker
Keyword(s):  
Finite Element ◽  
Dynamic Stability ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Elastic Shell ◽  
Rotating System ◽  
Finite Element Approach ◽  
Shell System ◽  
Modal Reduction ◽  
Element Approach

This paper presents a methodology and some results on the dynamic stability of an elastic rotating system consisting of one- and twodimensional members. These parts may contain different kinds of unsymmetries: either from mass- or stiffness imperfections or from anisotropic especially hydrodynamic bearings. The equations of motion are formulated using virtual work and an Finite Element approach. Special attention is paid to a kinematically consistent coupling of the elastic shell and disc. The eigenvalue extraction is based upon the method of Lanczos including a modal reduction and a correction process in order to ensure true diagonal system matrices. Some typical results for a shaft-disc-shell system with different bearings and imperfections are presented in detail.

On the Response of a Two-Degree-of-Freedom Rigid Disk With a Moving Massive Load

1973 ◽  
Vol 40 (1) ◽  
pp. 114-120 ◽  
Author(s):  
K. J. Stahl ◽  
W. D. Iwan
Keyword(s):  
Critical Speed ◽  
Equations Of Motion ◽  
Circular Disk ◽  
Instability Region ◽  
Degree Of Freedom ◽  
Viscous Damping ◽  
Elastically Supported ◽  
Two Degree Of Freedom ◽  
Limiting Value ◽  
Mathieu Equations

An analysis of the dynamic response of an elastically supported two-degree-of-freedom rigid circular disk excited by a moving massive load is presented. The equations of motion of the system are solved by transforming a set of coupled Hill-Mathieu equations into an ordinary eigenvalue problem. Two types of system instability are observed. A stiffness instability region exists above the critical speed of the disk and a terminal instability region exists for all load speeds exceeding a certain limiting value. The introduction of viscous damping may destabilize the system.

scholarly journals Dynamic Analysis of a Pendulum Dynamic Automatic Balancer

2007 ◽  
Vol 14 (2) ◽  
pp. 151-167 ◽  
Author(s):  
Jin-Seung Sohn ◽  
Jin Woo Lee ◽  
Eun-Hyoung Cho ◽  
No-Cheol Park ◽  
Young-Pil Park
Keyword(s):  
Stability Analysis ◽  
Dynamic Stability ◽  
Critical Speed ◽  
Equations Of Motion ◽  
Polar Coordinates ◽  
Response Analysis ◽  
Rotating Speed ◽  
Time Response Analysis ◽  
The Stability ◽  
Nonlinear Equations Of Motion

The automatic dynamic balancer is a device to reduce the vibration from unbalanced mass of rotors. Instead of considering prevailing ball automatic dynamic balancer, pendulum automatic dynamic balancer is analyzed. For the analysis of dynamic stability and behavior, the nonlinear equations of motion for a system are derived with respect to polar coordinates by the Lagrange's equations. The perturbation method is applied to investigate the dynamic behavior of the system around the equilibrium position. Based on the linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue analysis.The stability analysis provides the design requirements for the pendulum automatic dynamic balancer to achieve a balancing of the system. The efficiency of ball automatic dynamic balancer, for reducing the total vibration of the system, is better than one of pendulum automatic balancer, if the rotating speed is above critical speed. However, pendulum automatic dynamic balancer can achieve balancing even if the rotating speed is below critical speed.The time response analysis demonstrates the stability analysis from computing the radial displacement of the rotating system and the positions of pendulums. Furthermore, in order to confirm the theoretical analysis, various experiments are made on pendulum automatic dynamic balancer.

Thermal Property Measurements on Biological Materials at Subzero Temperatures

1991 ◽  
Vol 113 (4) ◽  
pp. 423-429 ◽  
Author(s):  
Xuemei Bai ◽  
David E. Pegg
Keyword(s):  
Thermal Conductivity ◽  
Low Temperatures ◽  
The Self ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Low Viscosity ◽  
Subzero Temperatures ◽  
Liquid Samples ◽  
Thermal Probes ◽  
Low Ionic Strength

The self-heated thermistor technique was used to measure the thermal conductivity and thermal diffusivity of biomaterials at low temperatures. Thermal standards were selected to calibrate the system at temperatures from −10°C to −70°C. The thermal probes were constructed with a convection barrier which eliminates convection inside liquid samples of low viscosity, without affecting the conductivity and diffusivity results. Using this technique, the thermal conductivity and diffusivity of two organ perfusates (HP5 and HP5 + 2M glycerol), one kidney phantom (a low ionic strength gel), as well as rabbit kidney cortex have been measured from −10°C to −70°C.

Ion acceleration by multiple laser pulses and their spontaneous electromagnetic fields in plasma

2008 ◽  
Vol 74 (1) ◽  
pp. 111-118
Author(s):  
FEN-CE CHEN
Keyword(s):  
Magnetic Fields ◽  
Electric Field ◽  
Analytical Model ◽  
Electromagnetic Fields ◽  
Equations Of Motion ◽  
Charged Particles ◽  
Laser Pulses ◽  
The Self ◽  
Electric And Magnetic Fields ◽  
Relativistic Equations

AbstractThe acceleration of ions by multiple laser pulses and their spontaneously generated electric and magnetic fields is investigated by using an analytical model for the latter. The relativistic equations of motion of test charged particles are solved numerically. It is found that the self-generated axial electric field plays an important role in the acceleration, and the energy of heavy test ions can reach several gigaelectronvolts.

scholarly journals ACCRETION AND PLASMA OUTFLOW FROM DISSIPATIONLESS DISCS

2010 ◽  
Vol 19 (03) ◽  
pp. 339-365 ◽  
Author(s):  
S. V. BOGOVALOV ◽  
S. R. KELNER
Keyword(s):  
Angular Momentum ◽  
Similar Case ◽  
Gravitational Energy ◽  
Accretion Disc ◽  
The Self ◽  
Low Viscosity ◽  
Variable Polarity ◽  
Self Similar ◽  
Similar Solutions ◽  
High Electric Conductivity

We consider the specific case of disc accretion for negligibly low viscosity and infinitely high electric conductivity. The key component in this model is the outflowing magnetized wind from the accretion disc, since this wind effectively carries away angular momentum of the accreting matter. Assuming magnetic field has variable polarity in the disc (to avoid magnetic flux and energy accumulation at the gravitational center), this leads to radiatively inefficient accretion of the disc matter onto the gravitational center. In such a case, the wind forms an outflow, which carries away all the energy and angular momentum of the accreted matter. Interestingly, in this framework, the basic properties of the outflow (as well as angular momentum and energy flux per particle in the outflow) do not depend on the structure of accretion disc. The self-similar solutions obtained prove the existence of such an accreting regime. In the self-similar case, the disc accretion rate (Ṁ) depends on the distance to the gravitational center, r, as [Formula: see text], where λ is the dimensionless Alfvenic radius. Thus, the outflow predominantly occurs from the very central part of the disc provided that λ ≫ 1 (it follows from the conservation of matter). The accretion/outflow mechanism provides transformation of the gravitational energy from the accreted matter into the energy of the outflowing wind with efficiency close to 100%. The flow velocity can essentially exceed the Kepler velocity at the site of the wind launch.

Seismic response for self-strained structures

1974 ◽  
Vol 64 (6) ◽  
pp. 1809-1824
Author(s):  
Mario Paz ◽  
Michael A. Cassaro ◽  
Steven N. Stewart
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Dynamic Properties ◽  
Equations Of Motion ◽  
The Self ◽  
Mode Shapes ◽  
Strain Effect ◽  
Structure Changes ◽  
Superposition Technique ◽  
Initial Strains

abstract The seismic response of multistory building and other structural systems is affected by the existence of self strains which may be induced by temperature gradients, mechanical actions, or prestraining. The fundamental dynamic properties such as natural frequencies and mode shapes are influenced by the presence of these strains. As a consequence, the response of the structure changes to the extent that the self strains change its dynamic characteristics and to the extent that these characteristics are relevant in the interaction of a particular structure with a given ground motion. This paper presents a detailed study of some simple structures such as beams and frames whose members are subjected to initial strains. The homogeneous differential equations of motion are expressed in terms of the stiffness, mass, and geometry matrices and a parameter accounting for the self-strain effect. The solution of the resulting eigenvalue problem is used to write the modal equations into which the desired ground motion is applied. The final response is obtained from the appropriate shock spectrum and the application of root-mean-square superposition technique. The disturbing action produced by the ground motion of the well known El Centro earthquake of 1940 is applied to several structures in which the amount of self-strain is varied as a parameter.

scholarly journals Computer models of spiral structure

1970 ◽  
Vol 38 ◽  
pp. 368-372 ◽  
Author(s):  
F. Hohl
Keyword(s):  
Motion Picture ◽  
Computer Model ◽  
Spiral Structure ◽  
Galactic Disk ◽  
Equations Of Motion ◽  
Computer Models ◽  
The Self ◽  
Large Numbers ◽  
Self Consistent

A computer model for isolated disks of stars is used to study the self-consistent motion of large numbers of point masses as they move in the plane of the galactic disk. The Langley Research Center's CDC 6600 computers are used to integrate the equations of motion for systems containing from 50000 to 200000 stars. The results are presented in the form of a motion picture.

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