Vibration stability of a cantilevered thin plate with inner fluid circulation

2021 ◽  
pp. 107754632098534
Author(s):  
Yunjie Wang ◽  
Yajun Yin ◽  
Gangtie Zheng
Keyword(s):  
Flow Velocity ◽  
Thin Plate ◽  
Torsional Motion ◽  
Fluid Circulation ◽  
Coupled Vibration ◽  
Torsional Mode ◽  
Typical Situation ◽  
Coupled Mode ◽  
Vibration Stability

The vibration of a cantilevered thin plate with inner fluid circulation is a typical situation in engineering. The plate’s vibration can be considered a combination of bending motion and torsional motion. With the force generated by the inner fluid circulation on the plate, these two types of motion affect each other and raise the problem of stability. In the present study, the vibration stability of different vibrating pattern thus generated is investigated. It is found that with the increase of the flow velocity, torsional mode frequencies decrease synchronously, whereas their modal shapes remain unchanged, which results in the buckling of the plate. Under the circumstance of coupled vibration, because both bending and torsional modal frequencies vary with the flow velocity, a phenomenon of coupled-mode flutter occurs between a certain pair of modes with frequency orders of (2 k) and (2 k − 1) and vibration becomes unstable.

Development of Nonlinear Coupled Mode Bushing Model Based on the Bouc-Wen Hysteretic Model

2007 ◽  
Author(s):  
Jin-Kyu Ok ◽  
Jeong-Hyun Sohn ◽  
Wan-Suk Yoo
Keyword(s):  
Sensitivity Analyses ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Torsional Mode ◽  
Coupled Mode ◽  
Sensitivity Indices ◽  
Rubber Bushing ◽  
Hysteretic Characteristics ◽  
Vehicle Suspension System ◽  
And Behavior

In this paper, a coupled bushing model for vehicle dynamics analysis based on the Bouc-Wen hysteretic model is proposed. Bushing components of a vehicle suspension system are tested to capture the nonlinear and behavior of the typical rubber bushing elements using MTS machine. Test results are used to define the parameters of the Bouc-Wen bushing model. The Bouc-Wen model is employed to represent the hysteretic characteristics of the bushing. A coupled relation for radial mode and torsional mode are suggested. Model parameters are obtained by using the genetic algorithm, and sensitivity indices of parameters are also extracted from the sensitivity analyses. ADAMS program is used for the identification process and VisualDOC program is employed to find the optimal parameters of the proposed model. A half-car simulation is carried out to validate the proposed bushing model.

The photoelectron spectra of allene, deuteroallenes and tetrafluoroallene

1974 ◽  
Vol 339 (1616) ◽  
pp. 29-36 ◽  
Keyword(s):  
Current Theory ◽  
Photoelectron Spectra ◽  
Teller Effect ◽  
Molecular Vibration ◽  
Coupled Vibration ◽  
Torsional Mode ◽  
Jahn Teller ◽  
Stretching Vibration ◽  
Jahn Teller Effect ◽  
Vertical Ionization Potentials

The photoelectron spectra of allene, allene 1.1-d 2 , allene-d 4 and tetra­fluoroallene have been measured in the region 6–20 eV. Allene shows three vertical ionization potentials at 10.02, 14.75 and 17.3 eV. The first band, involving ionization from a π orbital, shows a complex vibrational struc­ture, but there is a marked convergence of the intervals towards the higher energy side. It is suggested that the main coupled vibration is the torsional mode. The band appears to involve a Jahn–Teller effect, but there are two sub-maxima, and current theory seems insufficient to account for all the observed features. The spectra of the deuteroallenes show similar bands, the vibrational intervals being affected by the isotope effect. The photoelectron spectrum of tetrafluoroallene shows three bands at 11.24, 16.26 and 17.00 eV. The first band, associated with ionization from a π orbital, shows a coupled vibrational frequency of 1450 cm -1 . The infrared and Raman spectra of tetrafluoroallene have been measured in order to determine the molecular vibration frequencies and all eleven frequencies have been assigned. The first band in the photoelectron spec­trum has been interpreted as involving the C═C═C symmetrical stretching vibration in the ion, and there is no sign of a Jahn–Teller effect.

Nonlinear Resonator With Interacting Flexural-Torsional Modes for Mass Sensing

2007 ◽  
Author(s):  
Ashwin Vyas ◽  
Anil K. Bajaj ◽  
Dimitrios Peroulis
Keyword(s):  
Natural Frequency ◽  
Torsional Motion ◽  
Attached Mass ◽  
Mass Sensing ◽  
Torsional Mode ◽  
Flexural Mode ◽  
Torsional Response ◽  
Highly Sensitive ◽  
Out Of Plane ◽  
Nonlinear Resonator

We explore the use of a pedal shaped nonlinear microresonator designed with torsion and flexural modes in 1:2 internal resonance for mass sensing. The higher natural frequency in-plane flexural mode of the resonator is coupled nonlinearly through inertial coupling to the out-of-plane torsional mode with one-half natural frequency. When the flexural mode excited resonantly has response above a threshold, the torsional mode is excited. This response in torsional mode is highly sensitive to any mass perturbation that results in mistuning the two modes away from 1:2 resonance. The mistuning can drastically change the nonlinearly excited torsional response from non-zero amplitude to zero amplitude. The required increase in the actuation strength to reactivate the torsional motion can serve as a measure for the attached mass.

Flutter of Conservative Systems of Pipes Conveying Incompressible Fluid

1975 ◽  
Vol 17 (1) ◽  
pp. 19-25 ◽  
Author(s):  
M. P. Paidoussis
Keyword(s):  
Flow Velocity ◽  
Shell Theory ◽  
Beam Theory ◽  
High Flow ◽  
Coupled Mode ◽  
Conservative Systems ◽  
Pipes Conveying Fluid ◽  
The One ◽  
Thin Shell Theory ◽  
Conveying Fluid

An examination of the dynamics of beam-like motions of pipes conveying fluid, with both ends clamped, is presented by means of beam theory and, in the case of thin-walled pipes, by thin-shell theory. Both theories predict that the system loses stability by divergence at sufficiently high flow velocity, and that at higher flow velocity the system is subject to coupled-mode flutter; between the two instabilities there is sometimes a region where the system is completely stable. The critical flow velocities obtained by beam theory and by shell theory are compared, and it is shown that the former coverage towards the latter as the length of the pipe increases. Finally, the existence of coupled-mode flutter in gyroscopic conservative systems, such as the one investigated here, is briefly discussed.

scholarly journals Vibration and Stability of Two Tubes in Cross-Flow

1997 ◽  
Vol 119 (2) ◽  
pp. 142-149 ◽  
Author(s):  
S. Zhu ◽  
S. S. Chen ◽  
Y. Cai
Keyword(s):  
Unsteady Flow ◽  
Flow Velocity ◽  
Water Channel ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Coupled Vibration ◽  
Fluid Forces ◽  
Stiffness Coefficients ◽  
Fluid Damping

Two tubes in tandem and normal to flow were studied on the basis of the unsteady-flow theory. Motion-dependent fluid forces were measured in a water channel, and the pitch-to-diameter ratio was 1.35. From the measured fluid forces, fluid damping and stiffness were calculated as a function of reduced flow velocity and several Reynolds numbers. Once the fluid-damping and fluid-stiffness coefficients are known, coupled vibration and stability of the two tubes in cross-flow can be predicted.

The new CM-Series TEMs: integration of a five-axis motorized, fully computer-controlled goniometer

1993 ◽  
Vol 51 ◽  
pp. 258-259
Author(s):  
Marc J.C. de Jong ◽  
P. Emile S.J. Asselbergs ◽  
Max T. Otten
Keyword(s):  
Mechanical Design ◽  
Computer Control ◽  
Objective Lens ◽  
Access Port ◽  
Vibration Stability ◽  
Transmission Electron ◽  
Computer Controlled ◽  
High Degree ◽  
Five Axis ◽  
Five Axes

A new step forward in Transmission Electron Microscopy has been made with the introduction of the CompuStage on the CM-series TEMs: CM120, CM200, CM200 FEG and CM300. This new goniometer has motorization on five axes (X, Y, Z, α, β), all under full computer control by a dedicated microprocessor that is in communication with the main CM processor. Positions on all five axes are read out directly - not via a system counting motor revolutions - thereby providing a high degree of accuracy. The CompuStage enters the octagonal block around the specimen through a single port, allowing the specimen stage to float freely in the vacuum between the objective-lens pole pieces, thereby improving vibration stability and freeing up one access port. Improvements in the mechanical design ensure higher stability with regard to vibration and drift. During stage movement the holder O-ring no longer slides, providing higher drift stability and positioning accuracy as well as better vacuum.

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