Lock-in thermography for nondestructive evaluation of materials |
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| Institution: | 1. School of Aeronautics and Astronautics, University of Electronic Science and Technology of China, Chengdu, 611731, China;2. School of Electrical and Electronic Engineering, Newcastle University, Newcastle Upon Tyne, NE1 7UR, UK;3. Materials and Structures (MAST) Centre, Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY, UK;1. School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu, China;2. School of Electrical and Electronic Engineering, Newcastle University, England, United Kingdom;3. University of Michigan-Shanghai Jiao Tong University Joint Institute, 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 |
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| Abstract: | Photothermal radiometry allows for remote measurement of local harmonic heat transport where the phase angle (between remote optical energy deposition and resulting temperature modulation) is sensitive to subsurface features or defects. Phase sensitive modulation thermography (or ‘lock-in thermography’) combines the advantages of photothermal radiometry with the fast technique of infrared imaging thereby revealing hidden defects in a short time. In this paper the principle and various applications are described and analyzed. While this lock-in thermography is based on remote optical heating of the whole area of interest, one can heat defects selectively with modulated ultrasound which is converted into heat by the mechanical loss angle effect which is enhanced in defect regions. This ‘ultrasonic lock-in thermography’ provides images showing defects in a way that is similar to dark field imaging in optical microscopy. |
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