Measurement of the Thermal Diffusivity of Optical Materials and Products by a New Thermographic Express Method That Does Not Require Cutting Samples Out of the Bulk.

Autor: Golovin, Yu. I., Samodurov, A. A., Golovin, D. Yu., Tyurin, A. I., Divin, A. G., Zakharov, Yu. A.
Předmět:
Zdroj: Measurement Techniques; Apr2023, Vol. 66 Issue 1, p36-44, 9p
Abstrakt: Thermal diffusivity a and thermal conductivity λ are important parameters for many structural and functional material applications. These parameters determine the intensity of heat transfer, the quality of thermal insulation, the rate of heating/cooling, the efficiency of power equipment, as well as the possibility of reaching a stationary mode. In laser technologies, a and λ define the radiation resistance of the optical components of a system. In laser technologies involving material removal, these parameters determine the speed and quality of machining. At present, the majority of methods for measuring a and λ in solid materials require cutting out samples of a certain geometry, which makes such methods unsuitable for testing finished products. In this paper, we propose an express method for determining a and λ in translucent materials, which does not require cutting samples out of an object under inspection. This method implies registration and analysis of a nonstationary temperature field on the surface of a test object using a high-speed thermal imaging camera. An unsteady heating spot is created by a focused laser beam. The laser is operated in the mode of intermittent switching and continuous irradiation under constant intensity during the entire period of measurements. The heat propagated from this spot to the periphery forms a nonstationary temperature field, which contains information about a and λ. The a value is derived from the primary data using original algorithms and software. The dynamic temperature field is recorded by a thermal camera, a noncontact and high-speed device capable of processing a large amount of information (each of the many hundreds of thousands of pixels of a professional thermal imager matrix is a temperature sensor in a small surface area). The specifics of measuring thermal diffusivity a and thermal conductivity λ in translucent materials of laser beam optics is noted. Thus, the low radiation absorption coefficient and the possible curvature of the surface (for example, in lenses) require special measures. Due to the large amount of information contained in the dynamic patterns of thermal field and the possibility of averaging over a large data array, the RMS of the thermal diffusivity measurement does not exceed 2%. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
Externí odkaz: