An Experimental Modal Analysis Technique for Miniature Structures

1996 ◽  
Vol 118 (1) ◽  
pp. 1-9 ◽  
Author(s):  
C. J. Wilson ◽  
D. B. Bogy
Keyword(s):  
Modal Analysis ◽  
Laser Doppler Vibrometer ◽  
Element Model ◽  
Experimental Modal Analysis ◽  
Modal Parameters ◽  
Computational Results ◽  
Magnetic Actuator ◽  
Analysis Technique ◽  
Excitation Force ◽  
Analysis System

This paper describes an experimental modal analysis system which can effectively be used to obtain the modal parameters of small structures. The system uses an electromagnetic exciter to produce the excitation force, a piezoelectric transducer to measure this force, and a Laser Doppler Vibrometer to measure the response. Several designs of the magnetic actuator are discussed and evaluated. The system is verified by obtaining the modal parameters of a miniature cantilever plate, using two preferred exciter designs, and comparing the measured parameters with those acquired from a finite element model. Favorable agreement is obtained between the experimental and computational results. Finally, the two preferred exciters are compared and an optimal configuration is discussed.

Modal Analysis of a Suspension Assembly

1994 ◽  
Vol 116 (3) ◽  
pp. 377-386 ◽  
Author(s):  
C. J. Wilson ◽  
D. B. Bogy
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Experimental System ◽  
Element Model ◽  
Modal Parameters ◽  
Geometrical Features ◽  
Analysis System ◽  
P Type ◽  
Innovative Techniques ◽  
The Finite Element Model

The dynamic characteristics of a suspension assembly are examined using new numerical and experimental techniques. The p-type finite element method is used to construct a numerical model of the suspension. There are significant advantages in using this approach to analyze these types of structures. The model is verified by an experimental modal analysis system, which has been shown to be effective in the study of small structures. The modelled modal parameters agree within 4.5 percent with the experimental results for 14 modes. Since the experimental system uses an electromagnetic exciter, a ferromagnetic target must be attached to the nonferrous suspension so that it can be excited. Innovative techniques are investigated to improve the attachment of this ferromagnetic target. Furthermore, the finite element model is utilized to evaluate the sensitivity of the modal parameters of the suspension to changes in its geometrical features.

Dynamic Simulation and Experimental Modal Analysis of Large Vibratory Feeder

2010 ◽  
Vol 139-141 ◽  
pp. 2423-2426
Author(s):  
Lian Wan Zhang ◽  
Zhong Jun Yin ◽  
Bing Chen ◽  
Zhi Chao Tang ◽  
Zheng Tian
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Element Model ◽  
Experimental Modal Analysis ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Element Analysis ◽  
Dynamic Design ◽  
Vibratory Feeder ◽  
Modal Damping

The LMS Test.Lab system was used to carried out experimental modal analysis of large vibratory feeder, the PloyMAX method was employed to estimate and identify the modal parameter of vibratory feeder and the modal parameters such as modal frequencies, modal damping ratios and mode shape at concerned band were got; Compared the results of experimental modal analysis to the results of finite element method, the results show that the experimental modal analysis and finite element analysis was consistent to some extent, verified the correctness of finite element model; the bias between experimental and theoretical is inevitable, the experimental results are more reliable relative to the actual and better reflect the dynamic characteristics of vibratory feeder, which will be provided as the reference for dynamic design and dynamic improvement of the vibratory feeder.

Experimental Modal Analysis of a Suspension Assembly Loaded on a Rotating Disk

1994 ◽  
Vol 116 (1) ◽  
pp. 85-92 ◽  
Author(s):  
C. J. Wilson ◽  
D. B. Bogy
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Rotating Disk ◽  
Disk Drive ◽  
Experimental Modal Analysis ◽  
Modal Parameters ◽  
Resonant Frequencies ◽  
Analysis System ◽  
Computer Disk

An experimental modal analysis system, which has been shown to be effective in the study of small structures, is utilized to analyze the interaction of the disk and the suspension assembly in a computer disk drive. A thorough understanding of the interaction of these structures is obtained by determining the modal parameters for each of the components in an uncoupled state and in a coupled state with the disk both stationary and rotating. It is shown that when a natural frequency of the suspension is close to that of the disk, two system resonant frequencies are created when the components are coupled together.

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
Author(s):  
Ewa B. Skrodzka ◽  
Bogumił B.J. Linde ◽  
Antoni Krupa
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Normal Value ◽  
Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

scholarly journals Transmissibilty-Based Operational Modal Analysis for Flight Flutter Testing Using Exogenous Inputs

2012 ◽  
Vol 19 (5) ◽  
pp. 1071-1083 ◽  
Author(s):  
Christof Devriendt ◽  
Tim De Troyer ◽  
Gert De Sitter ◽  
Patrick Guillaume
Keyword(s):  
Modal Analysis ◽  
Frequency Domain ◽  
Experimental Modal Analysis ◽  
Operational Modal Analysis ◽  
Modal Parameters ◽  
Input Output ◽  
Output Only ◽  
Flutter Testing

During the recent years several new tools have been introduced by the Vrije Universiteit Brussel in the field of Operational Modal Analysis (OMA) such as the transmissibility based approach and the the frequency-domain OMAX concept. One advantage of the transmissibility based approach is that the ambient forces may be coloured (non-white), if they are fully correlated. The main advantage of the OMAX concept is the fact that it combines the advantages of Operational and Experimental Modal Analysis: ambient (unknown) forces as well as artificial (known) forces are processed simultaneously resulting in improved modal parameters. In this paper, the transmissibility based output-only approach is combined with the input/output OMAX concept. This results in a new methodology in the field of operational modal analysis allowing the estimation of (scaled) modal parameters in the presence of arbitrary ambient (unknown) forces and artificial (known) forces.

Experimental Modal Analysis of Car's Body-in-White

2011 ◽  
Vol 346 ◽  
pp. 627-633 ◽  
Author(s):  
He Li ◽  
Shi Bo Fu ◽  
Bang Chun Wen
Keyword(s):  
Modal Analysis ◽  
Single Point ◽  
Test System ◽  
Experimental Modal Analysis ◽  
Modal Parameters ◽  
Modal Characteristics ◽  
Car Body ◽  
Modal Test ◽  
Acceleration Sensors ◽  
Body In White

To reduce noise and make the structure of the car more rational, we established modal test system of car's body-in-white in this paper. Car body-in-white was mounted on rigid platform with four coil springs. The car was excited by an electromagnetic exciter. The method of single-point excitation and multi-point collecting vibration was used in this test. Excitation point was chosen in the bearing beam. Signals picked up by the acceleration sensors were processed in the software of Mescope. With this system, different modal frequencies and modal characteristics of the car are acquired. The results show that modal parameters are effective and reliable and those parameters can be basis for the designer to improve the structure of the car.

scholarly journals Influence of Crack on Modal Parameters of Cantilever Beam Using Experimental Modal Analysis

2018 ◽  
Vol 1 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Siva Sankara Babu Chinka ◽  
Balakrishna Adavi ◽  
Srinivasa Rao Putti
Keyword(s):  
Numerical Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Cantilever Beam ◽  
Damping Ratio ◽  
Crack Depth ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Crack Location

In this paper, the dynamic behavior of a cantilever beam without and with crack is observed. An elastic Aluminum cantilever beams having surface crack at various crack positions are considered to analyze dynamically. Crack depth, crack length and crack location are the foremost parameters for describing the health condition of beam in terms of modal parameters such as natural frequency, mode shape and damping ratio. It is crucial to study the influence of crack depth and crack location on modal parameters of the beam for the decent performance and its safety. Crack or damage of structure causes a reduction in stiffness, an intrinsic reduction in resonant frequencies, variation of damping ratios and mode shapes. The broad examination of cantilever beam without crack and with crack has been done using Numerical analysis (Ansys18.0) and experimental modal analysis. To observe the exact higher modes of beam, discretize the beam into small elements. An experimental set up was established for cantilever beam having crack and it was excited by an impact hammer and finally the response was obtained using PCB accelerometer with the help sound and vibration toolkit of NI Lab-view. After obtaining the Frequency response functions (FRFs), the natural frequencies of beam are estimated using peak search method. The effectiveness of experimental modal analysis in terms of natural frequency is validated with numerical analysis results. This paper contains the study of free vibration analysis under the influence of crack at different points along the length of the beam.

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