Lateral Vibration Instability Mechanisms in a Constrained Rotating String

1998 ◽  
Vol 65 (3) ◽  
pp. 774-776 ◽  
Author(s):  
Jifang Tian ◽  
S. G. Hutton
Keyword(s):  
Lateral Vibration ◽  
Rotating String

scholarly journals On the quantization of folded strings in non-critical dimensions

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jacob Sonnenschein ◽  
Dorin Weissman
Keyword(s):  
Scalar Curvature ◽  
Space Dimension ◽  
Massive Particle ◽  
Open String ◽  
Closed String ◽  
Target Space ◽  
Critical Dimensions ◽  
Complete Set ◽  
Rotating String ◽  
Folding Point

Abstract Classical rotating closed string are folded strings. At the folding points the scalar curvature associated with the induced metric diverges. As a consequence one cannot properly quantize the fluctuations around the classical solution since there is no complete set of normalizable eigenmodes. Furthermore in the non-critical effective string action of Polchinski and Strominger, there is a divergence associated with the folds. We overcome this obstacle by putting a massive particle at each folding point which can be used as a regulator. Using this method we compute the spectrum of quantum fluctuations around the rotating string and the intercept of the leading Regge trajectory. The results we find are that the intercepts are a = 1 and a = 2 for the open and closed string respectively, independent of the target space dimension. We argue that in generic theories with an effective string description, one can expect corrections from finite masses associated with either the endpoints of an open string or the folding points on a closed string. We compute explicitly the corrections in the presence of these masses.

Modal synthesis method of lateral vibration analysis for rotor-bearing system

2002 ◽  
Vol 80 (32) ◽  
pp. 2537-2549 ◽  
Author(s):  
Chun-Ping Zou ◽  
Hong-Xing Hua ◽  
Duan-Shi Chen
Keyword(s):  
Vibration Analysis ◽  
Synthesis Method ◽  
Lateral Vibration ◽  
Modal Synthesis ◽  
Rotor Bearing ◽  
Bearing System

Experimental Study on Lateral and Torsional Vibration of Cracked Rotor With Torsional Excitation

2013 ◽  
Author(s):  
Chao Liu ◽  
Dongxiang Jiang
Keyword(s):  
Experimental Study ◽  
Normal Condition ◽  
Torsional Vibration ◽  
Transverse Crack ◽  
Rotating Machinery ◽  
Lateral Vibration ◽  
Cracked Rotor ◽  
Diagnostic Features ◽  
Slant Crack ◽  
Torsional Excitation

Crack failures in rotating machinery can result in catastrophic accidents, and they are are difficult to detect online. Condition monitoring is widely applied in field to detect changes of vibration, and form diagnostic features. However, effective features in vibration of the cracked rotor need more tests, especially validating the features with experiments. This work carried out an experimental study on cracked rotors in laboratory. The experiments are as following: (I) vibration of the rotor in normal condition is firstly tested, where lateral vibration and torsional vibration are measured; (II) torsional excitation is exerted on driven end of rotor system, and vibration characteristics of the rotor are tested; (III) cracked rotors are tested with transverse and slant cracks, respectively. With the measured signals, comparisons of vibrations in normal rotor and cracked rotors are carried out. The results show that, the transverse crack introduces more significant changes in 1X frequency and coupled frequency, while the slant crack employs larger changes in 2X frequency. And variation of phases of 1X frequency is presented. Also, the crack plays an impact on the torsional responses.

Propulsion shafting whirling vibration: case studies and perspective

2015 ◽  
Author(s):  
Yuriy Batrak ◽  
Roman Batrak ◽  
Dmytro Berin ◽  
Andriy Mikhno
Keyword(s):  
Case Studies ◽  
Fatigue Failure ◽  
High Speed ◽  
Rotating Machinery ◽  
Lateral Vibration ◽  
Critical Speeds ◽  
Universal Joints

Since 1869 the main goal of whirling vibration calculations of rotating machinery was to determine critical speeds. Currently, all Classification Societies require a propulsion shafting whirling vibration calculation (also named bending or lateral vibration calculation) in the scope of the critical speeds i.e. free whirling vibration calculation. However, fatigue failure of the bracket and aft stern tube bearings, destruction of high-speed shafts with universal joints, noise and hull vibrations, generated by shafting, indicate the importance and inevitability of forced whirling vibration calculations. This paper presents some latest results of free and forced whirling vibration calculations obtained using the software intended for shaft design.

Impact on Beams

1936 ◽  
Vol 3 (2) ◽  
pp. A55-A61
Author(s):  
H. L. Mason
Keyword(s):  
Historical Development ◽  
Contact Region ◽  
Local Deformation ◽  
Lateral Vibration ◽  
Transverse Impact ◽  
Concentrated Mass ◽  
Impact Theory ◽  
Inelastic Impact ◽  
Maximum Contact

Abstract This paper deals with transverse impact on beams the mass of which is of importance. Experimental results are presented for comparison with theory. Impacts which appear single to the eye are shown to consist in reality of several blows in quick succession. Section 1 of the paper traces the historical development of this subject by discussing the investigations of Young, Hodgkinson, Cox, Saint Venant, and Timoshenko. Section 2 treats a simplified system in which a concentrated mass strikes a smaller concentrated mass having a “soft” spring restraint. For elastic impact, theory predicts for the struck mass a path composed of sinusoidal elements separated by instantaneous blows. For inelastic impact it predicts a joint harmonic motion. Records of the paths of both masses were obtained experimentally. Section 3 of the paper uses Timoshenko’s method of combining local deformation of the contact region with lateral vibration of the beam. An experimental investigation of maximum contact pressure and of blow duration gives what is believed to be the first confirmation of this theory. Section 4 describes an experimental determination of flexural stresses in elastic and inelastic impact on a 3-in. I-beam by the use of a Westinghouse magnetic strain gage. The indication is that stresses may be higher than those calculated by the usual approximations.

Lateral Vibration Research for Railway Deck Steel Plate Bridges

2011 ◽  
Vol 243-249 ◽  
pp. 1646-1650
Author(s):  
Wen Ping Li ◽  
Shu Li Chen ◽  
Mu Biao Su
Keyword(s):  
Steel Plate ◽  
Lateral Vibration ◽  
Vibration Model ◽  
Hunting Motion ◽  
Before And After ◽  
Vibration Mechanism ◽  
Track Irregularity ◽  
Lateral Reinforcement ◽  
Resonant Velocity

In this paper, the vehicle-bridge lateral vibration mechanism was analyzed; the vehicle-bridge vibration model was built and the lateral reinforcement schemes of open steel plate bridges were designed. Numbers of analysis were carried out for the lateral vibration of 40m deck steel plate bridges before and after reinforcement, under input of random artificial hunting waves and track irregularity. The results showed that, the frequency of hunting motion is approaching loaded frequency of the girder. The larger lateral amplitude appears on the bridge when the hunting wavelength is around 8~9m and the velocity of the train is around 55~70km/h. The wavelength is longer, the resonant velocity of the bridge is higher.

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