12 May 2015 Active infrared thermographic testing with distance heating
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In order to efficiently inspect very wide area of concrete structure wall, an infrared thermographic testing with a distance heating was developed in this study. The researched subjects were the following three; 1. Improvement of radiant heating efficiency, 2. Development of distance heating method and 3. Development of data analysis method against nonuniformity of a heating and/or a wall absorptivity. In this paper, we focus on the first issue. In order to investigate about combinations between the spectral emissivity of radiant heater and the spectral absorptivity of concrete, three different types of radiant heater, a near infrared type, a far infrared type and blackbody type, were used to heat concrete specimens. As a results, both a blackbody type and a far infrared type, e.g. a ceramics heater and a blackbody coated heater, can heat a concrete wall more efficiently than a near infrared type, e.g. a halogen lamp heater and a xenon lamp heater. This is because the spectral absorptivity of concrete is higher in a far infrared region than in a near infrared region. We find that the efficiency of the heating process may be improved by choosing a heater whose radiation is concentrated near wavelengths at which the structure to be heated exhibits maximal absorptivity. The efficiency of the concrete heating process may be easily improved simply by covering the surface of a near infrared heater with a blackbody surface coating to mimic the radiation characteristics of a blackbody.
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N. Ogasawara, N. Ogasawara, H. Ando, H. Ando, C. Kobayashi, C. Kobayashi, H. Yamada, H. Yamada, "Active infrared thermographic testing with distance heating", Proc. SPIE 9485, Thermosense: Thermal Infrared Applications XXXVII, 94850A (12 May 2015); doi: 10.1117/12.2176961; https://doi.org/10.1117/12.2176961

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