Vibrating Beam Technique for Measuring Animal Natural Frequency

1995 ◽  
Vol 14 (3) ◽  
pp. 119-133 ◽  
Author(s):  
John M Randall ◽  
Chaoying Peng
Keyword(s):  
Resonant Frequency ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Frequency Measurement ◽  
System Response ◽  
Single System ◽  
Design Requirements ◽  
Modal Mass ◽  
Two Degree Of Freedom ◽  
Beam Technique

The discomfort to animals arising from vibration during transport is likely to be greatest at their natural resonant frequency. This frequency can be measured without compromising animal welfare by placing them on a simple beam support at each end which is caused to vibrate by a small impulse. The optimum beam to give stable and accurate results for this technique is evaluated using a two-degree-of-freedom model. Some design requirements are contradictory, for example sensitivity to the resolution of frequency measurement and the benefits of having a single system response. These problems are alleviated by specifying a unified accuracy at both of the system natural frequencies. In this case the natural frequency of the beam should be twice that of the animal and the modal mass of the beam should equal that of the animal.

The Dynamical Characteristics of a Gyroscope With a Tuned Elastic Suspension

1980 ◽  
Vol 47 (1) ◽  
pp. 161-166 ◽  
Author(s):  
C. H. J. Fox ◽  
J. S. Burdess
Keyword(s):  
Mathematical Model ◽  
Rigid Body ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Elastic Suspension ◽  
Dynamical Characteristics ◽  
Suspension Parameters ◽  
Lower Natural Frequency ◽  
Two Degree Of Freedom ◽  
Selection Of

This study investigates the dynamics of a gyroscope rotor, supported on a “heavy” elastic suspension, using a mathematical model which allows the gyroscope to be treated as a two-degree-of-freedom rigid body on a light suspension. The natural frequencies are functions of spin rate and it is shown that the lower natural frequency can be reduced to zero by appropriate selection of suspension parameters. In this condition the gyroscope is “tuned” and could provide a useful inertial reference. Some problems associated with predicting the tuning speed of a practical gyroscope are highlighted.

Frequency Sweep Test and Modal Analysis of Watermelon during Transportation

2017 ◽  
Vol 13 (5) ◽  
Author(s):  
Fang Wang ◽  
Shaochun Ma ◽  
Wei Wei ◽  
Yong Zhang ◽  
Ziyi Zhang
Keyword(s):  
Resonant Frequency ◽  
Resonance Frequency ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Frequency Range ◽  
Frequency Sweep ◽  
Order Resonance ◽  
Frequency Sweep Test

Abstract Determining the natural frequency of watermelon is important to reduce loss by vibration during transportation. The purpose of frequency sweep test is to determine the tolerance of watermelon to vibration within a certain frequency range and to search the resonant frequency of watermelon in a certain frequency range. Frequency sweep test of Xinong No.8 watermelon cultivar was conducted, and the acceleration transmissibility curve was obtained. Furthermore, the 1st and 2nd order natural frequencies of watermelon were determined as 35.125 Hz and 71.034 Hz respectively from the acceleration transmissibility curve. Based on Geometric and mechanical parameters of Xinong No.8 watermelon cultivar, a finite element analysis model was developed and modal analysis of watermelon was carried out to obtain its natural frequencies and mode shapes. Since the value of 1st and 2nd order resonance frequency were the same or similar to the value of 3rd, 4th, and 5th order resonance frequency, this study only focused on 1st and 2nd order modes. The 1st order and 2nd order natural frequency test data fit to the corresponding simulation data well which validated the FEA model. This study demonstrated the feasibility of detecting the resonant frequency of watermelon vibration during transportation using FEA methods and provided a theoretical basis for watermelon transportation device design to reduce damage by avoiding resonant frequency.

scholarly journals A Method for Improving the Accuracy of Natural Frequency Measurement Using In-the-loop Computing

2021 ◽  
Vol 21 (4) ◽  
pp. 93-98
Author(s):  
Adam Kotowski
Keyword(s):  
Natural Frequency ◽  
Impulse Response ◽  
Finite Length ◽  
Spectral Resolution ◽  
Natural Frequencies ◽  
Reference Method ◽  
Frequency Measurement ◽  
Frequency Resolution ◽  
Zero Padding

Abstract The method presented in the paper is based on in-the-loop computing applied for impulse response to obtain a spectrum with a much higher frequency resolution than using FFT. Then, higher spectrum frequency resolution results in greater accuracy in estimation of natural frequencies. The frequency resolution of estimated spectrum in this method is completely independent of the length of impulse response and, by extension, the method eliminates the problem of spectral resolution limitation using FFT due to finite length of recorded signals. This fact is very useful and is the main advantage of the proposed method. The results of the method have been shown and compared in quantitative terms to natural frequencies estimated using classical FFT with zero-padding as reference method.

Natural Frequencies and Mode Shapes of Beams Carrying a Two Degree-of-Freedom Spring-Mass System

1993 ◽  
Vol 115 (2) ◽  
pp. 202-209 ◽  
Author(s):  
Ming Une Jen ◽  
E. B. Magrab
Keyword(s):  
Exact Solution ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Attached Mass ◽  
Approximate Methods ◽  
Mass System ◽  
The Laplace Transform ◽  
Rigid Mass ◽  
Two Degree Of Freedom

An exact solution for the natural frequencies and mode shapes for a beam elastically constrained at its ends and to which a rigid mass is elastically mounted is obtained. The attached mass can both translate and rotate. The general solution is obtained using the Laplace transform with respect to the spatial variable and yields the exact solutions to several previously published simpler configurations that were obtained using approximate methods. Numerous numerical results are presented for the natural frequency coefficients that extend previously reported results and that show the transition between various limiting cases. In addition, values are presented for the lowest two natural frequency coefficients for a beam that is clamped at both ends and is carrying a two dof spring-mass system. Representative mode shapes at selected values of the system’s parameters are also given.

Design of an Ultrasonic Pointed Cutter

2014 ◽  
Vol 494-495 ◽  
pp. 569-572
Author(s):  
Yun Dian Zhang ◽  
Ying Bin Shen ◽  
Zhi Ping Lu
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Processing Method ◽  
Tool Geometry ◽  
Finite Element Software ◽  
Optimal Geometry ◽  
Measurement Experiment ◽  
Design Requirements ◽  
The Mathematical Model ◽  
Ultrasonic Cutting

Ultrasonic cutting technique is an advanced processing method of cutting honeycomb materials. An ultrasonic pointed cutter was designed. Combined with the principle of ultrasonic cutting, the mathematical model of the tool was established. Modal analysis of the tool was calculated with the finite element software to study the effects of tool geometry on the natural frequency. The results show that the natural frequency increases as the tool thickness increases, but it decreases as the tool length increases. And it obtained the modal shapes and natural frequencies of the tool which meet design requirements. The optimal geometry of the tool was also determined. Finally, it verified the rationality of tool design by amplitude measurement experiment of the tool.

scholarly journals Effects of Elliptical Hole on the Correlation of Natural Frequency with Buckling Load of Basalt Laminates Composite Plates

2020 ◽  
Vol 27 (1) ◽  
pp. 216-225
Author(s):  
Buntheng Chhorn ◽  
WooYoung Jung
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Basalt Fiber ◽  
Orientation Angle ◽  
Elliptical Hole ◽  
Composite Plates ◽  
Buckling Load ◽  
Mode Shapes ◽  
Geometric Ratio

AbstractRecently, basalt fiber reinforced polymer (BFRP) is acknowledged as an outstanding material for the strengthening of existing concrete structure, especially it was being used in marine vehicles, aerospace, automotive and nuclear engineering. Most of the structures were subjected to severe dynamic loading during their service life that may induce vibration of the structures. However, free vibration studied on the basalt laminates composite plates with elliptical cut-out and correlation of natural frequency with buckling load has been very limited. Therefore, effects of the elliptical hole on the natural frequency of basalt/epoxy composite plates was performed in this study. Effects of stacking sequence (θ), elliptical hole inclination (ϕ), hole geometric ratio (a/b) and position of the elliptical hole were considered. The numerical modeling of free vibration analysis was based on the mechanical properties of BFRP obtained from the experiment. The natural frequencies as well as mode shapes of basalt laminates composite plates were numerically determined using the commercial program software (ABAQUS). Then, the determination of correlation of natural frequencies with buckling load was carried out. Results showed that elliptical hole inclination and fiber orientation angle induced the inverse proportion between natural frequency and buckling load.

scholarly journals A Vibration-Based Structural Health Monitoring System for Transmission Line Towers

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 515 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Ye Zhang ◽  
Yi Tian ◽  
Yu Zhao
Keyword(s):  
Structural Health Monitoring ◽  
Transmission Line ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Transmission Tower ◽  
Health Monitoring System ◽  
Wind Speeds ◽  
Before And After

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Vibration of Beams with a Single Delamination under Axial Loading

2011 ◽  
Vol 675-677 ◽  
pp. 477-480
Author(s):  
Dong Wei Shu
Keyword(s):  
Free Vibration ◽  
Natural Frequency ◽  
Analytical Solutions ◽  
Axial Load ◽  
Natural Frequencies ◽  
Axial Loading ◽  
Composite Beams ◽  
Mode Shapes ◽  
Equilibrium Conditions ◽  
Monotonic Relation

In this work analytical solutions are developed to study the free vibration of composite beams under axial loading. The beam with a single delamination is modeled as four interconnected Euler-Bernoulli beams using the delamination as their boundary. The continuity and the equilibrium conditions are satisfied between the adjoining beams. The studies show that the sizes and the locations of the delaminations significantly influence the natural frequencies and mode shapes of the beam. A monotonic relation between the natural frequency and the axial load is predicted.

Nondestructive Detection of a Crack in a Triangular Cantilever Beam Based on Frequency Measurement

2007 ◽  
Vol 353-358 ◽  
pp. 2285-2288
Author(s):  
Fei Wang ◽  
Xue Zeng Zhao
Keyword(s):  
Cantilever Beam ◽  
Natural Frequencies ◽  
Frequency Measurement ◽  
Crack Size ◽  
Force Sensors ◽  
Rotational Spring ◽  
Cantilever Deflection ◽  
Crack Location ◽  
Small Force ◽  
Point Of Intersection

Triangular cantilevers are usually used as small force sensors in the transverse direction. Analyzing the effect of a crack on transverse vibration of a triangular cantilever will be of value to users and designers of cantilever deflection force sensors. We present a method for prediction of location and size of a crack in a triangular cantilever beam based on measurement of the natural frequencies in this paper. The crack is modeled as a rotational spring. The beam is treated as two triangular beams connected by a rotational spring at the crack location. Formulae for representing the relation between natural frequencies and the crack details are presented. To detect crack details from experiment results, the plots of the crack stiffness versus its location for any three natural modes can be obtained through the relation equation, and the point of intersection of the three curves gives the crack location. The crack size is then calculated using the relation between its stiffness and size. An example to demonstrate the validity and accuracy of the method is presented.

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