Frequency Related Verification of MPR Model of Elastomeric Bushing in Torsional Mode

With the development of large-scale new energy, the wind–thermal bundled system transmitted via high-voltage direct current (HVDC) has become the main method to solve the problem of wind power consumption. At the same time, the problem of subsynchronous oscillation among wind power generators, high-voltage direct current (HVDC), and synchronous generators (SGs) has become increasingly prominent. According to the dynamic interaction among doubly fed induction generators (DFIGs), HVDC, and SGs, a linearization model of DFIGs and SGs transmitted via HVDC is established, and the influence of the electromagnetic transient of wind turbines and HVDC on the electromechanical transient processes of SGs is studied. Using the method of additional excitation signal injection, the influence of the main factors of DFIG on the damping characteristics of each torsional mode of SG is analyzed, including control parameters and operation conditions when the capacity of HVDC is fixed. The mechanism of the negative damping torsional of SGs is identified. A time-domain simulation model is built in Electromagnetic Transients including DC/Power Systems Computer Aided Design (EMTDC/PSCAD) to verify the correctness and effectiveness of the theoretical analysis.

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Comparison of linear and torsional mode ultrasonic coagulating shears for the sealing of medium- to large-sized arteries

Surgical Endoscopy ◽

10.1007/s00464-006-9113-8 ◽

2006 ◽

Vol 21 (7) ◽

pp. 1165-1169 ◽

Cited By ~ 10

Author(s):

S. S. Ching ◽

M. J. McMahon

Keyword(s):

Torsional Mode ◽

Ultrasonic Coagulating Shears

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Theoretical analyses and numerical simulations of the torsional mode for two acoustic viscometers with preliminary experimental tests

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/tuffc.2008.689 ◽

2008 ◽

Vol 55 (3) ◽

pp. 648-658 ◽

Cited By ~ 9

Author(s):

Yuhui Ai ◽

R.A. Lange

Keyword(s):

Numerical Simulations ◽

Experimental Tests ◽

Torsional Mode ◽

Theoretical Analyses

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Torsional Mode of B2Cl4

The Journal of Chemical Physics ◽

10.1063/1.1678284 ◽

1972 ◽

Vol 57 (2) ◽

pp. 1012-1013 ◽

Cited By ~ 12

Author(s):

L. H. Jones ◽

R. R. Ryan

Keyword(s):

Torsional Mode

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Parametric Instability of a Traveling Plate Partially Supported by a Laterally Moving Elastic Foundation

Journal of Vibration and Acoustics ◽

10.1115/1.2948394 ◽

2008 ◽

Vol 130 (5) ◽

Cited By ~ 7

Author(s):

V. Kartik ◽

J. A. Wickert

Keyword(s):

Data Storage ◽

Parametric Instability ◽

Primary Resonance ◽

Free Edge ◽

Moving Plate ◽

Torsional Mode ◽

Plane Vibration ◽

Out Of Plane ◽

Axially Moving ◽

The Stability

The parametric excitation of an axially moving plate is examined in an application where a partial foundation moves in the plane of the plate and in a direction orthogonal to the plate’s transport. The stability of the plate’s out-of-plane vibration is of interest in a magnetic tape data storage application where the read/write head is substantially narrower than the tape’s width and is repositioned during track-following maneuvers. In this case, the model’s equation of motion has time-dependent coefficients, and vibration is excited both parametrically and by direct forcing. The parametric instability of out-of-plane vibration is analyzed by using the Floquet theory for finite values of the foundation’s range of motion. For a relatively soft foundation, vibration is excited preferentially at the primary resonance of the plate’s fundamental torsional mode. As the foundation’s stiffness increases, multiple primary and combination resonances occur, and they dominate the plate’s stability; small islands, however, do exist within unstable zones of the frequency-amplitude parameter space for which vibration is marginally stable. The plate’s and foundation’s geometry, the foundation’s stiffness, and the excitation’s amplitude and frequency can be selected in order to reduce undesirable vibration that occurs along the plate’s free edge.

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Elastic Stiffness of Volcanic Sand through Resonant Column Tests

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.775.292 ◽

2015 ◽

Vol 775 ◽

pp. 292-297

Author(s):

Kostas Senetakis ◽

Anastasios Anastasiadis

Keyword(s):

Dynamic Properties ◽

Experimental Testing ◽

Elastic Stiffness ◽

Laboratory Method ◽

Granular Soils ◽

Resonant Column ◽

Torsional Mode ◽

Resonant Column Test ◽

Basic Features ◽

Low Amplitude

The resonant column method is established as a standard laboratory method for the study of the elastic properties of soils. The study presents low-amplitude resonant column test results on volcanic sands with intra-particle voids. The experiments were performed on dry samples prepared at variable relative densities and tested in torsional mode of vibration. In the first part of the article, the important factors that control the elastic stiffness of uncemented sands are described shortly and recent findings on granular soils dynamic properties are presented briefly. The second part describes the basic features of the resonant column used in the investigation and the materials of the study and in the third part representative results of an extensive experimental testing program on volcanic granular soils are presented and discussed with a focus on comparisons between the elastic stiffness of volcanic and quartz granular soils. The importance of the effect of the presence of intra-particle voids within the particle mass of the volcanic soils is emphasized, which in turn affects markedly the global void ratio of the samples.

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Experimental Study of the Shaft Penetration Factor on the Torsional Dynamic Response of a Drive Train

Machines ◽

10.3390/machines6030031 ◽

2018 ◽

Vol 6 (3) ◽

pp. 31 ◽

Cited By ~ 2

Author(s):

Hans Meeus ◽

Björn Verrelst ◽

David Moens ◽

Patrick Guillaume ◽

Dirk Lefeber

Keyword(s):

Experimental Study ◽

Torsional Vibration ◽

Torsional Stiffness ◽

Vibration Measurement ◽

Dynamic Amplification Factor ◽

Torsional Mode ◽

Penetration Factor ◽

Torsional Response ◽

Major Interest ◽

Drive Trains

Typical rotating machinery drive trains are prone to torsional vibrations. Especially those drive trains that comprise one or more couplings which connect the multiple shafts. Since these vibrations rarely produce noise or vibration of the stationary frame, their presence is hardly noticeable. Moreover, unless an expensive torsional-related problem has become obvious, such drive trains are not instrumented with torsional vibration measurement equipment. Excessive levels can easily cause damage or even complete failure of the machine. So, when designing or retrofitting a machine, a comprehensive and detailed numerical torsional vibration analysis is crucial to avoid such problems. However, to accurately calculate the torsional modes, one has to account for the penetration effect of the shaft in the coupling hub, indicated by the shaft penetration factor, on the torsional stiffness calculation. Many guidelines and assumptions have been published for the stiffness calculation, however, its effect on the damping and the dynamic amplification factor are less known. In this paper, the effect of the shaft penetration factor, and hence coupling hub-to-shaft connection, on the dynamic torsional response of the system is determined by an experimental study. More specifically, the damping is of major interest. Accordingly, a novel academic test setup is developed in which several configurations, with each a different shaft penetration factor, are considered. Besides, different amplitude levels, along with both a sweep up and down excitation, are used to identify their effect on the torsional response. The measurement results show a significant influence of the shaft penetration factor on the system’s first torsional mode. By increasing the shaft penetration factor, and thus decreasing the hub-to-shaft interference, a clear eigenfrequency drop along with an equally noticeable damping increase, is witnessed. On the contrary, the influence of the sweep up versus down excitation is less pronounced.

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The infrared spectrum of di-imide near 7.6 μm

Canadian Journal of Physics ◽

10.1139/p81-083 ◽

1981 ◽

Vol 59 (5) ◽

pp. 663-672 ◽

Cited By ~ 12

Author(s):

K-E. J. Hallin ◽

J. W. C. Johns ◽

A. Trombetti

Keyword(s):

Infrared Spectrum ◽

Gas Phase ◽

Type A ◽

Phase Spectrum ◽

The Other ◽

Mode Analysis ◽

Simultaneous Presence ◽

Torsional Mode ◽

Bending Mode ◽

Type C

The gas phase spectrum of N2H2 has been investigated in the region of 7.6 μm at a resolution of about 0.06cm−1. Two bands have been identified; one, near 1288 cm−1, is a type C band and must correspond to ν4 (the hitherto unidentified Au torsional mode), and the other, near 1317 cm−1, is a type A–B hybrid and corresponds to ν6 (the Bu bending mode). Analysis of the spectrum is complicated by the simultaneous presence of strong A-type and B-type Coriolis interactions which couple the observed levels.

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