Flow induced vibration measurement for a 4 × 4 rod bundle with spacer grids by the Laser Doppler Vibrometer

2022 ◽  
Vol 166 ◽  
pp. 108805
Author(s):  
Botao Zhang ◽  
Shengjie Gong ◽  
Fujun Gan ◽  
Chaozhu Zhang ◽  
Hanyang Gu
Keyword(s):  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Flow Induced Vibration ◽  
Spacer Grids ◽  
Rod Bundle

Temperature coefficient of Young’s modulus of silver microwhiskers determined by a laser Doppler vibration measurement

2021 ◽  
pp. 2150350
Author(s):  
Yijun Jiang ◽  
Mingyuan Lu ◽  
Shiliang Wang ◽  
Han Huang
Keyword(s):  
Temperature Dependence ◽  
Temperature Coefficient ◽  
Single Crystals ◽  
Young’S Modulus ◽  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Young's Modulus ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement

Temperature dependence of Young’s modulus of Ag microwhiskers was determined by a laser Doppler vibrometer. The Ag whiskers with diameters in sub-microns were synthesized by the use of physical vapor deposition (PVD). They have a five-fold twinned structure grown along the [1 1 0] direction. The temperature coefficient of Young’s modulus was measured to be [Formula: see text] ppm/K in the range of 300 K to 650 K. The measured values are very close to the reported values of [Formula: see text] ppm/K for bulk Ag single crystals. This finding can benefit the design of Ag-based micro/nano-electromechanical systems or micro/nano-interconnectors operated at elevated or lowered temperatures.

scholarly journals Damage Identification by Using a Self-Synchronizing Multipoint Laser Doppler Vibrometer

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Chong Yang ◽  
Yu Fu ◽  
Jianmin Yuan ◽  
Min Guo ◽  
Keyu Yan ◽  
...  
Keyword(s):  
Mode Shape ◽  
Natural Frequencies ◽  
Damage Identification ◽  
Reference Beam ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Interference Signal ◽  
Short Period

The vibration-based damage identification method extracts the damage location and severity information from the change of modal properties, such as natural frequency and mode shape. Its performance and accuracy depends on the measurement precision. Laser Doppler vibrometer (LDV) provides a noncontact vibration measurement of high quality, but usually it can only do sampling on a single point. Scanning LDV is normally used to obtain the mode shape with a longer scanning time. In this paper, a damage detection technique is proposed using a self-synchronizing multipoint LDV. Multiple laser beams with various frequency shifts are projected on different points of the object, reflected and interfered with a common reference beam. The interference signal containing synchronized temporal vibration information of multiple spatial points is captured by a single photodetector and can be retrieved in a very short period. Experiments are conducted to measure the natural frequencies and mode shapes of pre- and postcrack cantilever beams. Mode shape curvature is calculated by numerical interpolation and windowed Fourier analysis. The results show that the artificial crack can be identified precisely from the change of natural frequencies and the difference of mode shape curvature squares.

Case Studies of LDV-Aided Dynamic Testing

2012 ◽  
Vol 226-228 ◽  
pp. 2066-2071 ◽  
Author(s):  
Kao Shan Dai ◽  
Xiao Song Ren ◽  
Qing Jun Chen ◽  
Bin Zhao
Keyword(s):  
Prestressed Concrete ◽  
Dynamic Testing ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Structural Vibration ◽  
Structural Dynamic ◽  
Vibration Sensors ◽  
Sensing Technology ◽  
Contact Sensing

The laser Doppler vibrometer is a non-contact sensing technique developed based on the Doppler effect of a laser beam emerging from a subject surface. As a vibration transducer, the laser Doppler vibrometer offers many advantages over the conventional contact vibration sensors. It allows remote, non-intrusive measurement of structural vibration and it is very useful in scenarios when traditional contacting measurement is inconvenient. In this paper, four laser-based structural dynamic studies were presented and some results were briefly reported, which include laboratory dynamic testing of a bolted steel beam, a scaled-down high-rise building model, and a prestressed concrete reaction wall, and field vibration measurement of a viaduct bridge. Through these demonstrating cases, it is anticipated to help civil engineers get familiar with the laser-based sensing technology and to extend their selections for effective measurement approaches during experimental research.

scholarly journals Development of a High-Resolution All-Fiber Homodyne Laser Doppler Vibrometer

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5801
Author(s):  
Jianhua Shang ◽  
Yan He ◽  
Qi Wang ◽  
Yilun Li ◽  
Lihong Ren
Keyword(s):  
High Resolution ◽  
Background Noise ◽  
Sound Pressure ◽  
Laser Doppler Vibrometer ◽  
Cost Effective ◽  
Pressure Level ◽  
Laser Doppler ◽  
Vibration Measurement ◽  
Calibration Experiment ◽  
Optic Communication

Based on the homodyne detection, a compact and cost-effective all-fiber laser Doppler vibrometer (LDV) with high resolution is presented. For the signal processing, the discrimination algorithm combined with the nonorthogonal correction is applied. The algorithm corrects the quadrature imbalance and other nonlinearity. In the calibration experiment, with the glass pasted on a piezoceramic transducer (PZT), the velocity resolution of 62 nm/s at 4 kHz and displacement resolution of 2.468 pm are achieved. For the LDV-based acousto-optic communication, the minimum detectable sound pressure level (SPL) reached 0.12 Pa under the hydrostatic air-water surface. The results demonstrate that the designed homodyne LDV has a low system background noise and can offer high precision in the vibration measurement.

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