Detecting deeper defects using pulse phase thermography |
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| Institution: | 1. Graduate University for Advanced Studies (Sokendai), 3-1-1 Yoshinodai, Chuo-ku Sagamihara, Kanagawa 252-5210, Japan;2. Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku Sagamihara, Kanagawa 252-5210, Japan;3. Krautkramer Japan Co. Ltd., Fourth Floor Totojidosha Bldg., 5-13-3 Nishiikebukuro, Toshima-ku, Tokyo 171-0021, Japan;4. Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan;1. School of Mechanical Engineering, Heilongjiang University of Science and Technology, Harbin 150022, PR China;2. College of Light Industry, Harbin University of Commerce, Harbin 150028, PR China;3. Faculty of Electric and Control Engineering, Heilongjiang University of Science and Technology, Harbin 150022, PR China;1. Department of Civil and Architectural Engineering, Changsha University, Changsha 410003, PR China;2. College of Mechatronics Engineering and Automation, National University of Defense Technology, Changsha 410073, PR China;1. College of Mechanical and Electronic Engineering, China University of Petroleum (East China), Qingdao 266580, China;2. College of Engineering, Ocean University of China, Qingdao 266100, China |
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| Abstract: | Detectable defect depth by pulse phase thermography (PPT) is reportedly improved when using phase at low frequency. This study was conducted to identify mechanisms detecting deeper defects by the PPT, and to determine the optimum frequencies for detecting defects with various depths and sizes. One-dimensional and finite element analyses reveal that the optimum frequency decreases continuously with increasing defect depth, and that the amplitude of noise appearing in phase data decreases with decreased frequency. These engender a large signal-to-noise ratio for deep defects in a lower-frequency range. The analytical results were verified by experiments for a polymethylmethacrylate specimen having artificial defects. The experimental results at the optimum frequency demonstrated that defects with up to 5–6 mm depth were detected, which is a significant improvement compared with the reported detectable defect depth of 3.5 mm. |
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