き裂評価のためのサブハーモニック超音波フェーズドアレイ（ＳＰＡＣＥ）へのレーザー干渉計の応用

概要

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Recently, nonlinear ultrasound, especially subharmonics, is highly expected to be a tool for detecting and evaluating closed cracks. Considering the above, we have constructed a Subharmonic Phased Array for Crack Evaluation (SPACE). However, the SPACE with piezoelectric array sensor could not receive wideband frequency components because of the frequency characteristics of the sensor. The present array sensor also had problems in that the in-plane information was averaged and the freedom of the system was limited. In this study, to expand frequency bandwidth and to realize flexible array configuration, we propose laser SPACE that could image the defects by scanning laser interferometer, filtering the received waveforms, matching the phase using delay law and extracting feature quantity. This enables us to image the defects using subharmonics or second harmonics and construct a 2 dimension array that provides detailed information of the thickness direction of the crack. In addition, it is a useful tool for designing optimized elements layout of a piezoelectric 2 dimensional array. In this paper, we formulated imaging algorithms of laser SPACE and applied it to a linear defect and a fatigue crack. Closed parts of the fatigue crack were imaged by subharmonic components only. Additionally, by comparing the results with images provided by a piezo SPACE, we demonstrate the advantage of laser SPACE.
一般社団法人日本非破壊検査協会の論文