Measurement of Torsional Vibration in Rotating Machinery

1986 ◽  
Vol 108 (4) ◽  
pp. 565-577 ◽  
Author(s):  
J. M. Vance ◽  
R. S. French
Keyword(s):  
Torsional Vibration ◽  
Measurement Techniques ◽  
Time History ◽  
Rotating Machinery ◽  
Drive Train ◽  
Vibration Measurement ◽  
Time Interval ◽  
Advantages And Disadvantages ◽  
System A ◽  
History Of

Five techniques for measurement of torsional vibration in a drive train are described, along with the advantages and disadvantages of each. Two laboratory test rigs, designed and constructed for experimental evaluation of various torsional vibration measurement techniques, are described. The measurement techniques investigated fall into three categories: a) those using signals from strain gages, b) those using signals from a magnetically transduced gear, and c) using signals optically transduced from a special tape applied to the shaft. One of the techniques described requires no specialized instrumentation other than a spectrum analyzer, which is now typically available in plants with rotating machinery. Another technique is capable of producing a detailed time history of torsional oscillations during acceleration of the drive train (i.e., startup), using a time interval measurement system. A comparison of results from the various techniques is given, and recommendations are made for several types of applications.

Energies of precipitating electrons during pulsating aurora events derived from ionosonde observations

1981 ◽  
Vol 59 (8) ◽  
pp. 1070-1076 ◽  
Author(s):  
J. W. MacDougall ◽  
J. Hofstee ◽  
J. A. Koehler
Keyword(s):  
Energy Flux ◽  
Time History ◽  
Time Interval ◽  
Characteristic Energy ◽  
Morning Sector ◽  
History Of

The time-history of particle energies and fluxes associated with pulsating auroras in the morning sector is derived from ionosonde measurements. All the pulsating auroras studied showed a similar history with the pulsations occurring during a time interval of the order of an hour during which the average auroral Maxwellian characteristic energy stays relatively constant but the energy flux decreases progressively during the event. A possible explanation for this behaviour in terms of an injection of particles into a magnetospheric "bottle" near the midnight meridian and the progressive precipitation out of the bottle during the pulsating event is suggested.

scholarly journals STRESS-DEFORMED STATE OF STEEL-REINFORCED CONCRETE STRUCTURES OF FLOORS AT THE STAGE OF ESTABLISHMENT OF STRUCTURES

2021 ◽  
pp. 101-106
Author(s):  
M. V. Savytskyi ◽  
T.D. NIKIFOROVA ◽  
M. O. FROLOV
Keyword(s):  
Reinforced Concrete ◽  
Strain State ◽  
Complex Stress ◽  
Time Interval ◽  
Stress Strain ◽  
Advantages And Disadvantages ◽  
Stress Strain State ◽  
Composite Section ◽  
History Of ◽  
Deformed State

Formulation of the problem. Many structures today require floor structures to meet increased requirements for strength, span coverage and surface quality. Steelcrete structures often fit the bill. However, despite a long history of success, the industry is still not fully understood, in particular, the behavior of this structure in the early stages of construction is not unambiguous. Due to the impossibility of creating a composite section, various effects and a complex stress-strain state immediately arise in the time interval between the combination of different materials in space and the combination of different materials in the work. Thus, the stage of erection of a structure before it became reinforced concrete is of interest for a complete understanding of the mechanics of the work of composite sections. The purpose of the study is to investigate the features of the operation of the steelcrete sections at the stage of installation and operation, as a composite structure that combines the advantages and disadvantages of steel and concrete. As a result of the research, it was found that the study of the stress-strain state, which affects the circumstances, both at the operation stage and at the construction stage, is an important task for further understanding the work of reinforced concrete. , and increasing its durability. In particular, at the time of erection, a complex stress-strain state occurs, which can lead to unpredictable changes in shape. This state is unstable up to the inclusion of the concrete shelf of the reinforced concrete section in the work due to the hardening of concrete in the area of the anchors and its subsequent inclusion in work. These issues require further study in order to better understand the work of concrete and steel as a single composite material at various stages of the life cycle of structures.

Characteristics of Torsional Vibrations of a Shaft System with Parallel Misalignment

2005 ◽  
Vol 219 (11) ◽  
pp. 1219-1224 ◽  
Author(s):  
Diangui Huang
Keyword(s):  
Experimental Study ◽  
Measurement System ◽  
Torsional Vibration ◽  
Experimental Results ◽  
Vibration Measurement ◽  
Torsional Vibrations ◽  
System A ◽  
Shaft System ◽  
Parallel Misalignment

Couplings are important parts in the movement of a shaft system. A coupling can transfer the torque from one shaft to another through deforming itself. If parallel misalignment exists, the couplings will produce an extra deformation besides the deformation produced by transferring the torque. The exciting moment with one-time rotating frequency produced by this extra deformation is analysed in this article. This moment will result in torsional vibration at one-time rotating frequency. By use of DK-II torsional vibration measurement system, an experimental study of torsional vibrational behaviour in a parallel misalignment shaft system is carried out. The experimental results support the conclusion of analysis.

Discussion of the Available Methods for Blade Vibration Measurement

2002 ◽  
Author(s):  
B. O. Al-Bedoor
Keyword(s):  
Torsional Vibration ◽  
Performance Monitoring ◽  
Measurement Techniques ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Vibration Measurement ◽  
Experimental Investigations ◽  
Main Rotor ◽  
Blade Vibration ◽  
Indirect Approach

Blade vibration has been recognized as one major and costly cause of failure in turbo-machinery. Its vibration measurement has attracted many investigators where until now there is no single reliable approach can be identified. Blade vibration measurement techniques can be classified into two broad categories, namely; (1) the direct approach that includes using strain gages, optical/laser methods, etc., to monitor directly the blade motion at one or more points on the blade span, (2) the indirect approach by extracting some vibration information form the lateral main rotor vibration and the casing/bearing cap vibration, pressure fluctuations, performance monitoring and thermal changes. Recently, a new indirect method has received attention of investigators which is monitoring the torsional vibration of the main rotor. This technique has been investigated by theoretical and experimental studies. The direct and indirect techniques are described in this survey paper and advantages and draw backs are discussed. From the results of this survey it seems that the indirect approach using the torsional vibration measurement is the most promising among all indirect techniques and further theoretical and experimental investigations are recommended.

scholarly journals Radial diffusion simulations of the 20 September 2007 radiation belt dropout

2014 ◽  
Vol 32 (8) ◽  
pp. 925-934 ◽  
Author(s):  
J. Albert
Keyword(s):  
Pitch Angle ◽  
Radiation Belt ◽  
Outer Boundary ◽  
Time History ◽  
Radial Diffusion ◽  
Time Interval ◽  
Resonant Interactions ◽  
Magnetic Field Model ◽  
History Of ◽  
Electromagnetic Ion Cyclotron Waves

Abstract. This is a study of a dropout of radiation belt electrons, associated with an isolated solar wind density pulse on 20 September 2007, as seen by the solid-state telescopes (SST) detectors on THEMIS (Time History of Events and Macroscale Interactions during Substorms). Omnidirectional fluxes were converted to phase space density at constant invariants M = 700 MeV G−1 and K = 0.014 RE G1/2, with the assumption of local pitch angle α ≈ 80° and using the T04 magnetic field model. The last closed drift shell, which was calculated throughout the time interval, never came within the simulation outer boundary of L* = 6. It is found, using several different models for diffusion rates, that radial diffusion alone only allows the data-driven, time-dependent boundary values at Lmax = 6 and Lmin = 3.7 to propagate a few tenths of an RE during the simulation; far too slow to account for the dropout observed over the broad range of L* = 4–5.5. Pitch angle diffusion via resonant interactions with several types of waves (chorus, electromagnetic ion cyclotron waves, and plasmaspheric and plume hiss) also seems problematic, for several reasons which are discussed.

scholarly journals The Use of LiDAR-Derived DEM in Flood Applications: A Review

2020 ◽  
Vol 12 (14) ◽  
pp. 2308 ◽  
Author(s):  
Nur Atirah Muhadi ◽  
Ahmad Fikri Abdullah ◽  
Siti Khairunniza Bejo ◽  
Muhammad Razif Mahadi ◽  
Ana Mijic
Keyword(s):  
Lidar Data ◽  
Time Interval ◽  
Flood Simulation ◽  
Advantages And Disadvantages ◽  
Future Assessment ◽  
System A ◽  
Reflected Light ◽  
Digital Elevation ◽  
Elevation Model ◽  
Derived Data

Flood occurrence is increasing due to escalated urbanization and extreme climate change; hence, various studies on this issue and methods of flood monitoring and mapping are also increasing to reduce the severe impacts of flood disasters. The advancement of current technologies such as light detection and ranging (LiDAR) systems facilitated and improved flood applications. In a LiDAR system, a laser emits light that travels to the ground and reflects off objects like buildings and trees. The reflected light energy returns to the sensor, whereby the time interval is recorded. Since the conventional methods cannot produce high-resolution digital elevation model (DEM) data, which results in low accuracy of flood simulation results, LiDAR data are extensively used as an alternative. This review aims to study the potential and the applications of LiDAR-derived DEM in flood studies. It also provides insight into the operating principles of different LiDAR systems, system components, and advantages and disadvantages of each system. This paper discusses several topics relevant to flood studies from a LiDAR-derived DEM perspective. Furthermore, the challenges and future perspectives regarding DEM LiDAR data for flood mapping and assessment are also reviewed. This study demonstrates that LiDAR-derived data are useful in flood risk management, especially in the future assessment of flood-related problems.

PROGRAM OF PREDICTION AND MANAGEMENT OF COINTEGED DYNAMIC ECONOMIC PROCESSES BASED ON THE CYBERNETIC APPROACH

2019 ◽  
Author(s):  
Olena Bundak ◽  
Nataliia Zubovetska
Keyword(s):  
Computer Program ◽  
Pair Correlation ◽  
Time History ◽  
Critical Area ◽  
Concrete Object ◽  
Graphic Arts ◽  
Ex Post ◽  
History Of ◽  
Successive Change ◽  
Rms Errors

A method and computer program ConRow, which prognostication of development of the dynamically CPLD economic transients is executed by, is described in the article. Such prognostication of economic processes is very important in the cases when their development can result in undesirable consequences, that to go out in the so-called critical area. Extrapolation in a critical area with the use of information about the conduct of the system at an area, near to it, allows to estimate to the lead through of experiment in the critical area of his consequence. For the imitation of conduct of object the function of review is set on entrance influence. For a concrete object this function can express, for example, dependence of change of level sale from time-history of charges on advertising and set as a numeral row. Statistics as a result of analysis of row are represented in a table, where the level of meaningfulness is set statistician, and also parameters of the handed over criteria. The graphic reflection of information is intended for visualization of analysis. Here represented on the points of graphic arts, the crooked smoothing which are calculated as полиномиальные regressions is added. The best approaching is controlled by sight on the proper graph, and also by minimization of their rms errors. Models of prognostication by sight and as formulas represented on graphic arts, the middle is here determined tailings and their chance is checked up on statistics of signs. After the got models determined also and prognosis values of influences and reviews. Establishing an order models of Сr(p) of co integrate regression is carried out separate custom controls. The coefficient of clay correlation of ruФ shows by itself pair correlation between lines with a successive change in relation to each other on a size to лагу of l = 1, 2, 3 . The program was tested on the example of ex-post prognosis at establishing an integration connection and possibility of prognostication of growth of nominal average monthly settlings on the basis of these statistical indexes of consumer inflation in Ukraine.

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