The transient sound radiation monitor of a free beam by a single point vibration measurement

2011 ◽  
Author(s):  
Junhong Dong ◽  
Xianjun Wu ◽  
Yingjian Wang
Keyword(s):  
Single Point ◽  
Sound Radiation ◽  
Vibration Measurement ◽  
Radiation Monitor ◽  
Free Beam

scholarly journals Determination of beam characteristics by its vibration measurement

1995 ◽  
Vol 17 (3) ◽  
pp. 27-38
Author(s):  
Nguyen Cao Menh ◽  
Tran Trong Toan
Keyword(s):  
Inverse Problem ◽  
Analytical Method ◽  
Transverse Vibration ◽  
Vibration Measurement ◽  
Computational Program ◽  
Beam Characteristics ◽  
Free Beam

On the basis of analyzing the transverse vibration of a clamped-free beam, in this paper an inverse problem is investigated. The analytical method· and computational program me have been presented for determination of the length of the beam when vibrations at some points on the beam with external distribution excitation or vibration at one point with some excited frequencies are measured. The obtained results from the illustration examples described in the paper give us the procedure for selecting one solution in multi-solution inverse problem.

A New Imaging Method for Arterial Tubes Based on Vibration Measurement

2003 ◽  
Author(s):  
Xiaoming Zhang ◽  
Mostafa Fatemi ◽  
James F. Greenleaf
Keyword(s):  
Focal Point ◽  
Single Point ◽  
Vibration Measurement ◽  
Ultrasound Transducer ◽  
Imaging Method ◽  
Large Artery ◽  
Large Radius ◽  
Modal Shape ◽  
Measured Velocity ◽  
Gel Phantom

A new method for imaging and detecting modal shapes of vessels is introduced. Theory is developed that predicts the measured velocity is proportional to the value of the mode shape at the focal point of the ultrasound beam. Experimental a cylindrical gel phantom of large radius. This model simulates approximately a large artery and the surrounding body. The fundamental frequency was measured 83 Hz for the tube-phantom system. At this frequency the ultrasound transducer was scanned across the vessel plane with velocity measurement at one single point on the vessel and on the phantom by laser. The images obtained show clearly the interior tube and the modal shape of the tube.

Interface Properties Due to Microslip From Vibration Measurement

1999 ◽  
Vol 123 (1) ◽  
pp. 230-233 ◽  
Author(s):  
H. A. Sherif ◽  
T. M. Abu Omar
Keyword(s):  
Contact Stiffness ◽  
Single Point ◽  
Peak Frequency ◽  
Vibration Measurement ◽  
Interface Properties ◽  
Flat Surfaces ◽  
Dry Contact ◽  
Impulse Excitation ◽  
Interface Parameters ◽  
Two Degree Of Freedom

A method of measuring contact stiffness and friction damping at interacting plane surfaces of a mechanical system comprised of two sub-structures in dry contact is presented. The method is based on the measurement of displacement ratio of the contacting sub-structures as a function of frequency due to light impulse excitation at a single point on any of the two sub-structures. The theoretical analysis depends on a very simple model of a two-degree-of-freedom system with elastic coupling. The effects of applied normal loads, and contact configuration on the interface parameters are shown. The theoretical and experimental analyses show that the interface properties for the flat-on-flat surfaces of the two contacting sub-structures can be determined from the measured peak amplitude and peak frequency of the microslip in the frequency domain.

Elimination of Multi-Points Support Effects in Modal Testing

2013 ◽  
Vol 290 ◽  
pp. 79-84
Author(s):  
Jun Ren ◽  
Shu Sheng Bi ◽  
Wei Wang ◽  
Guang Hua Zong
Keyword(s):  
Single Point ◽  
Noisy Data ◽  
Modal Testing ◽  
Response Functions ◽  
Support Effects ◽  
Modal Test ◽  
Measured Frequency Response ◽  
Support Conditions ◽  
Stiffness And Damping ◽  
Free Beam

The measured Frequency Response Functions (FRFs) often have errors due to the support effects in free-free modal testing. In [1], elimination of support effects from the measured FRFs has been investigated and both stiffness and damping have been considered in support conditions. However, the method is only applicable for single point support occasion while the test structure is usually supported from more than one location in a practical testing. Therefore, this paper further investigates this method to extend its application to multi-points support conditions. Firstly, general formulas of removing the multipoint support effects from the measured FRFs are derived based on the dynamic substructure method. Then a simulated modal test of free-free beam with two points suspension is proposed to verify this method. Finally, the performance of the method is investigated with simulated noisy data. It is shown that the proposed method is effective in removing support stiffness as well as support damping from the measured FRFs as long as the measured data are not heavily contaminated by the noise.

scholarly journals Full-Field Vibration Measurement Using Camera Through Shearlet System

2018 ◽  
Vol 217 ◽  
pp. 01002
Author(s):  
C.A. Wee ◽  
M. Z. Ngali
Keyword(s):  
Promising Result ◽  
Single Point ◽  
Laser Doppler Vibrometer ◽  
Field Capacity ◽  
Vibration Signal ◽  
Vibration Measurement ◽  
Single Frequency ◽  
Mode Shapes ◽  
Circular Membrane ◽  
Full Field

Traditionally, vibration measurement is done using an accelerometer or Laser Doppler Vibrometer, which is an intrusive and single point measurement respectively. This paper demonstrated vibration signal extracted from a perceptually invisible vibrating object using only a camera non-intrusively at full-field capacity. the camera that is capable to capture 1000 frames-per-second video was used to capture the motion of the vibrating object. Each frame of the video was decomposed using complex shearlet transform and the extracted signal was compared to an accelerometer. Shearlet decomposed each frame of the video into complex coefficients which were later used to recover the motion between two consecutive frames. Phase information that were used to retrieve the vibration signal were weighted to decrease unwanted noise. Resonant frequencies of a simply supported beam at 104.0 Hz, 209.5 Hz and 396.0Hz were successfully recovered. Single frequency extraction from an excited loud-speaker at specific frequencies were also conducted and showed a clear peak-to-valley frequency spectrum recovery. the potential of using camera as a full-field displacement measurement where each pixel acting as a vibrometer was explored. Full-field test to recover the mode shape of a circular membrane showed promising result with eight mode shapes successfully retrieved. the experiments proved that each individual pixel was able to retrieve motion at subpixel level that is at 0.00001 pixel scale.

scholarly journals Lateral resolution limit of laser Doppler vibrometer microscopes for the measurement of surface acoustic waves

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Robert Kowarsch ◽  
Christian Rembe
Keyword(s):  
Single Point ◽  
Surface Acoustic Waves ◽  
Numerical Aperture ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Lateral Resolution ◽  
Approximation Formula ◽  
Analytic Approximation ◽  
Resolution Limit ◽  
Measurement Deviation

AbstractThe lateral or transverse resolution of single-point interferometers for vibration measurement is especially critical for microelectromechanical systems (MEMS) vibrating up to the gigahertz range. In this regime, the acoustic wavelengths are typically in the range of the size of the laser focus. Thus, a successful vibration measurement requires distinct knowledge about the lateral resolution limit and its dependencies with instrumentation parameters. In this paper, we derive an analytic approximation formula, which allows for estimation of the systematic measurement deviation of the vibration amplitude and, thus, a definition of the lateral resolution limit of single-point interferometers for vibration measurement. Further, a compensation and an optimum numerical aperture are proposed the reduce the measurement deviation. For this, the model includes a laser-interferometer microscope of Mach-Zehnder type with Gaussian laser beams considering the Gouy effect and wavefront curvature. As a measurement scenario, an unidirectional surface acoustic wave (SAW) is regarded. The theoretic findings have been validated in the experiment with a representative vibration measurement on a SAW filter at $$433\,{\mathrm {MHz}}$$ 433 MHz with our heterodyne laser-Doppler interferometer with offset-locked semiconductor lasers. The provided formulas help instrument designers and users to choose suitable instrument parameters, especially the numerical aperture of the utilized microscope objective.

Fine-scale taxonomic and temporal variability in the energy density of invertebrate prey of juvenile Chinook salmon Oncorhynchus tshawytscha

2020 ◽  
Vol 655 ◽  
pp. 185-198
Author(s):  
J Weil ◽  
WDP Duguid ◽  
F Juanes
Keyword(s):  
Energy Density ◽  
Chinook Salmon ◽  
Temporal Variability ◽  
Energy Content ◽  
Single Point ◽  
Single Species ◽  
Fine Scale ◽  
Temporal Differences ◽  
Juvenile Chinook Salmon ◽  
Juvenile Chinook

Variation in the energy content of prey can drive the diet choice, growth and ultimate survival of consumers. In Pacific salmon species, obtaining sufficient energy for rapid growth during early marine residence is hypothesized to reduce the risk of size-selective mortality. In order to determine the energetic benefit of feeding choices for individuals, accurate estimates of energy density (ED) across prey groups are required. Frequently, a single species is assumed to be representative of a larger taxonomic group or related species. Further, single-point estimates are often assumed to be representative of a group across seasons, despite temporal variability. To test the validity of these practices, we sampled zooplankton prey of juvenile Chinook salmon to investigate fine-scale taxonomic and temporal differences in ED. Using a recently developed model to estimate the ED of organisms using percent ash-free dry weight, we compared energy content of several groups that are typically grouped together in growth studies. Decapod megalopae were more energy rich than zoeae and showed family-level variability in ED. Amphipods showed significant species-level variability in ED. Temporal differences were observed, but patterns were not consistent among groups. Bioenergetic model simulations showed that growth rate of juvenile Chinook salmon was almost identical when prey ED values were calculated on a fine scale or on a taxon-averaged coarse scale. However, single-species representative calculations of prey ED yielded highly variable output in growth depending on the representative species used. These results suggest that the latter approach may yield significantly biased results.

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