2013 Fiscal Year Research-status Report
Two-beam probing laser-based system for remote inspection of unstable structures
Project/Area Number |
25420495
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Research Institution | Institute for Laser Technology |
Principal Investigator |
コチャエフ オレグ 公益財団法人レーザー技術総合研究所, レーザー計測研究チーム, 研究員 (80399352)
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Project Period (FY) |
2013-04-01 – 2016-03-31
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Keywords | nondestructive testing / laser interferometry / bouncing bridge |
Research Abstract |
Preliminary mobile prototype of the system has been assembled. Optical layout is close to the real system design. The system prototype has been tested in the laboratory and filed conditions. In laboratory, the system has demonstrated capability of detection of laser-initiated vibration. Special samples with inner defect were used as test specimens. The system could recognize inner defect even if the sample was moving imitating bouncing structure. However, working with speckled radiation puts some limitations on the system performance. Instability of speckled leads to fluctuation of the laser signal power after spatial filtering. Despite of comparatively slow movement of bouncing structures – several hertz only – signal power after spatial filtering is fluctuating with frequency up to 80 kHz. Time windows where the signal is comparatively stable are shorter than one observed in the preliminary experiments with using corner cubes in the probing points. The algorithm of inspection should take this fact into account. After laboratory tests, the system prototype was delivered to the field experiment site. Under real bridge loaded with heavy traffic, signal instability due to speckle movement was lower than in laboratory – up to 12 kHz. But it also overlapped the range of expected vibration frequency. Anyway, there still exist time windows when the vibration measurement procedure can be started and completed. In the next field tests, the system will be examined with laser impact.
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Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Progressing is in a good accordance with initial plan.
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Strategy for Future Research Activity |
Future work will follow the initial plan. The main goal of the second year is optimization of laser impact. CO2 laser and Nd:YAG laser will be tested as possible sources of laser impact. As well, details of the algorithm of scanning and real-time processing will be considered.
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Expenditure Plans for the Next FY Research Funding |
209189 yen was non used. This money was supposed to be used for buying new plate polarizers. However, polarizers with desirable parameters were not in stock. They will be available starting from May 2014. The polarizers which were supposed to be purchased last year will be ordered in June 2014.
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