20 April 2012 Laser ultrasonic imaging of a rotating blade
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Abstract
Although there are many laser ultrasonic imaging techniques developed so far, it still remains challenging to create such images from a rotating object. In this study, an advanced laser ultrasonic imaging technique is developed so that wavefield images can be constructed from a rotating blade using an embedded piezoelectric sensor and a scanning excitation laser system. Here, the biggest challenge is to precisely estimate and control the exact excitation point when the wind blade is rotating with additional ambient vibration and having complex shapes. In this study, the laser excitation point is precisely estimated by computing the correlation values between the measured response signal and the ones in the training data sets. First, training ultrasonic signals are measured at the fixed sensing point by scanning the excitation laser over the target surface of the blade when the blade is in a stationary condition. Once the training is complete, an ultrasonic signal is generated for the rotating blade using the excitation laser and measured by the sensor. The correlation between the measured response and a training response is maximized when they correspond to the same excitation point. Finally, ultrasonic images are generated by scanning the excitation laser over the target surface of the blade. The effectiveness of the proposed imaging technique is investigated through experimental tests performed on a rotating blade specimen.
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Byeongjin Park, Troung Thanh Chung, Chul Min Yeum, Hoon Sohn, "Laser ultrasonic imaging of a rotating blade", Proc. SPIE 8348, Health Monitoring of Structural and Biological Systems 2012, 83481A (20 April 2012); doi: 10.1117/12.918007; https://doi.org/10.1117/12.918007
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