Analysis of Random Mechanical Vibrations in Symmetrical Thin Plates Using Full-Field Vibration Measurements

2021 ◽  
Vol 143 (2) ◽  
Author(s):  
Alain Le Bot ◽  
Olivier Robin ◽  
Kevin Rouard ◽  
Alain Berry
Keyword(s):  
High Speed ◽  
Wide Band ◽  
Random Force ◽  
Thin Plates ◽  
Source Analysis ◽  
Vibration Measurements ◽  
Full Field ◽  
Weakly Coupled ◽  
Coupled Subsystems ◽  
Measurement Results

Abstract A successful application of statistical energy analysis for analyzing energy exchanges between weakly coupled subsystems theoretically requires a diffuse vibrational field in all subsystems. So as to verify the conditions of establishment of the diffuse field in practice, full-field vibration measurements were conducted with a high-speed camera on a simply supported rectangular plate excited by a wide band random force. The results constitute an experimental investigation of the diffuse field region in the frequency-structural damping domain and a validation of previously obtained numerical results. The domain of the diffuse field is confined to high frequencies and low damping, with limits than can be easily defined. However, it is shown that the vibrational field is not fully spatially homogeneous due to enhancement of response induced by the effect of coherence of rays. Theoretical values of the enhancement factor obtained using an image source analysis are confirmed by measurement results.

scholarly journals Experimental study of the dynamic behaviour of High Performance Concrete (HPC) under tensile loading

2018 ◽  
Vol 183 ◽  
pp. 02043 ◽  
Author(s):  
Bratislav Lukić ◽  
Dominique Saletti ◽  
Pascal Forquin
Keyword(s):  
High Speed ◽  
High Performance ◽  
High Performance Concrete ◽  
Imaging System ◽  
Spall Strength ◽  
High Speed Imaging ◽  
Dynamic Tensile Strength ◽  
Full Field ◽  
Local Point ◽  
Measurement Results

This paper presents the measurement results of the dynamic tensile strength of a High Performance Concrete (HPC) obtained using full-field identification method. An ultra-high speed imaging system and the virtual fields method were used to obtain this information. Furthermore the measurement results were compared with the local point-wise measurement to validate the data pressing. The obtained spall strength was found to be consistently 20% lower than the one obtained when the Novikov formula is used.

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.

High Speed Impact Behaviour of Thermo-Mechanically Processed AA 6082-T6 Thin Plates

2018 ◽  
Vol 5 (9) ◽  
pp. 17203-17212 ◽  
Author(s):  
Rahul Dubey ◽  
Srinivasa Rakesh ◽  
R Velmurugan ◽  
R Jayaganthan
Keyword(s):  
High Speed ◽  
Thin Plates ◽  
Impact Behaviour ◽  
High Speed Impact

Design of a multi-function high-speed digital baseband data acquisition system

2021 ◽  
Vol 21 (10) ◽  
pp. 248
Author(s):  
Xin Pei ◽  
Jian Li ◽  
Na Wang ◽  
Toktonur Ergesh ◽  
Xue-Feng Duan ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Radio Telescope ◽  
High Speed ◽  
Single Channel ◽  
Wide Band ◽  
Data Acquisition System ◽  
Acquisition System ◽  
Single Server ◽  
Long Baseline ◽  
Digital Baseband

Abstract A multi-function digital baseband data acquisition system is designed for the sampling, distribution and recording of wide-band multi-channel astronomical signals. The system hires a SNAP2 board as a digital baseband converter to digitize, channelize and packetize the received signal. It can be configured dynamically from a single channel to eight channels with a maximum bandwidth of 4096 MHz. Eight parallel HASHPIPE instances run on four servers, each carrying two NVMe SSD cards, achieving a total continuous write rate of 8 GB s−1. Data are recorded in the standard VDIF file format. The system is deployed on a 25-meter radio telescope to verify its functionality based on pulsar observations. Our results indicate that during the 30-minute observation period, the system achieved zero data loss at a data recording rate of 1 GB s−1 on a single server. The system will serve as a verification platform for testing the functions of the QTT (QiTai radio Telescope) digital backend system. In addition, it can be used as a baseband/VLBI (Very Long Baseline Interferometry) recorder or D-F-engine of correlator/beamformer as well.

Using Wavelet Analysis to Distinguish Cavitation Acoustic Emissions From Blunt Impact Noise

2021 ◽  
Author(s):  
Christopher Eckersley ◽  
Joost Op 't Eynde ◽  
Mitchell Abrams ◽  
Cameron R. Bass
Keyword(s):  
Wavelet Transform ◽  
High Speed ◽  
Acoustic Noise ◽  
Bubble Formation ◽  
Acoustic Emissions ◽  
Wide Band ◽  
Water Tank ◽  
Impact Noise ◽  
Blunt Impact

Abstract Cavitation has been shown to have implications for head injury, but currently there is no solution for detecting the formation of cavitation through the skull during blunt impact. The goal of this communication is to confirm the wideband acoustic wavelet signature of cavitation collapse, and determine that this signature can be differentiated from the noise of a blunt impact. A controlled, laser induced cavitation study was conducted in an isolated water tank to confirm the wide band acoustic signature of cavitation collapse in the absence of a blunt impact. A clear acrylic surrogate head was impacted to induce blunt impact cavitation. The bubble formation was imaged using a high speed camera, and the collapse was synched up with the wavelet transform of the acoustic emission. Wideband acoustic response is seen in wavelet transform of positive laser induced cavitation tests, but absent in laser induced negative controls. Clear acrylic surrogate tests showed the wideband acoustic wavelet signature of collapse can be differentiated from acoustic noise generated by a blunt impact. Broadband acoustic signal can be used as a biomarker to detect the incidence of cavitation through the skull as it consists of frequencies that are low enough to potentially pass through the skull but high enough to differentiate from blunt impact noise. This lays the foundation for a vital tool to conduct CSF cavitation research in-vivo.

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