Application of Vibration Pattern Imaging to modal analysis; a comparison with full-field and point measurement techniques

1989 ◽  
Author(s):  
R. G. Bream ◽  
B. C. Gasper ◽  
B. E. Lloyd ◽  
G. M. Everett
Keyword(s):  
Modal Analysis ◽  
Measurement Techniques ◽  
Full Field ◽  
Point Measurement ◽  
Vibration Pattern

scholarly journals Full-Field Operational Modal Analysis of an Aircraft Composite Panel from the Dynamic Response in Multi-Impact Test

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1602
Author(s):  
Ángel Molina-Viedma ◽  
Elías López-Alba ◽  
Luis Felipe-Sesé ◽  
Francisco Díaz
Keyword(s):  
Modal Analysis ◽  
Energy Absorption ◽  
High Speed ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Image Correlation ◽  
Composite Panel ◽  
Impact Excitation ◽  
Full Field ◽  
The Impact

Experimental characterization and validation of skin components in aircraft entails multiple evaluations (structural, aerodynamic, acoustic, etc.) and expensive campaigns. They require different rigs and equipment to perform the necessary tests. Two of the main dynamic characterizations include the energy absorption under impact forcing and the identification of modal parameters through the vibration response under any broadband excitation, which also includes impacts. This work exploits the response of a stiffened aircraft composite panel submitted to a multi-impact excitation, which is intended for impact and energy absorption analysis. Based on the high stiffness of composite materials, the study worked under the assumption that the global response to the multi-impact excitation is linear with small strains, neglecting the nonlinear behavior produced by local damage generation. Then, modal identification could be performed. The vibration after the impact was measured by high-speed 3D digital image correlation and employed for full-field operational modal analysis. Multiple modes were characterized in a wide spectrum, exploiting the advantages of the full-field noninvasive techniques. These results described a consistent modal behavior of the panel along with good indicators of mode separation given by the auto modal assurance criterion (Auto-MAC). Hence, it illustrates the possibility of performing these dynamic characterizations in a single test, offering additional information while reducing time and investment during the validation of these structures.

scholarly journals Comparison between Accelerometer and Laser Vibrometer to Measure Traffic Excited Vibrations on Bridges

2002 ◽  
Vol 9 (1-2) ◽  
pp. 11-18 ◽  
Author(s):  
G. Rossi ◽  
R. Marsili ◽  
V. Gusella ◽  
M. Gioffrè
Keyword(s):  
Modal Analysis ◽  
Measurement Techniques ◽  
Forced Vibrations ◽  
The Other ◽  
Laser Vibrometer ◽  
Threshold Parameter ◽  
Civil Structures ◽  
Low Frequencies ◽  
Acceleration Amplitude ◽  
The One

The use of accelerometer based measurement techniques for evaluating bridge forced vibrations or to perform bridge modal analysis is well established. It is well known to all researchers who have experience in vibration measurements that values of acceleration amplitude can be very low at low frequencies and that a limitation to the use of accelerometer can be due to the threshold parameter of this kind of transducer. Under this conditions the measurement of displacement seems more appropriate. On the other hand laser vibrometer systems detect relative displacements as opposed to the absolute measures of accelerometers. Vibrations have been measured simultaneously by a typical accelerometer for civil structures and by a laser vibrometer equipped with a fringe counter board in terms of velocity and displacements. The accelerations calculated from the laser vibrometer signals and the one directly measured by the accelerometer has been compared.

FP+DIC for low-cost 3D full-field experimental modal analysis in industrial components

2019 ◽  
Vol 128 ◽  
pp. 329-339 ◽  
Author(s):  
Luis Felipe-Sesé ◽  
Ángel J. Molina-Viedma ◽  
Elías López-Alba ◽  
Francisco A. Díaz
Keyword(s):  
Modal Analysis ◽  
Low Cost ◽  
Experimental Modal Analysis ◽  
Full Field

Investigating the Flexural Behaviour of Foams at High Strain Rate Using Optical Measurement Techniques

2013 ◽  
Vol 569-570 ◽  
pp. 799-804
Author(s):  
Duncan A. Crump ◽  
Janice M. Dulieu-Barton
Keyword(s):  
High Speed ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Maximum Load ◽  
Image Correlation ◽  
Test Machine ◽  
Full Field ◽  
Closed Cell ◽  
Load To Failure ◽  
Point Bend

Polymer closed cell foam beam specimens manufactured from H100 Divinycell (Diab) are tested in four point bend at three loading speeds using a specially designed rig and an Instron VHS test machine. Synchronised high speed images are captured using white light and infra-red thermography (IRT) to obtain the mid-point full-field deflection and strains using digital image correlation (DIC) along with the temperature evolutions. There is a marked increase in the maximum load to failure with loading rate and the optical techniques provide an opportunity to analyse the strain and temperature evolution within the specimens.

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