Temperature Field Measurement in a Cutting Tool by Laser Interferometry

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To increase machining efficiency, in addition to determining the temperature distribution on the tool surface, it is also necessary to determine the internal temperature distribution. The existing methods for determining the cutting tool temperature distribution and temperature field measurement have significant disadvantages, which limit their applicability and accuracy. The purpose of this study is to develop and test a novel cutting tool temperature field measurement method. The method involves recording the cutting tool thermal expansion fields by laser interferometry and calculating the tool material temperatures with its coefficient of thermal expansion (CTE). Compared with the methods employing infrared thermometry, the method developed in the present study has a higher spatial resolution and a lower achievable field of view due to its usage of light in the visible region. In addition, since the oxidation film has a higher reflection coefficient for visible light, the present method is less sensitive to the thin-film interference on an oxidized tool surface than those using infrared thermometry, eliminating the false shift of the measured temperature. Moreover, by utilizing cheaper optical components and equipment for interference fringe pattern registration, this method is more affordable. Unlike the emissivity coefficient in infrared thermometry, CTE is independent of changes in the surface quality and can be measured with high accuracy by modern dilatometry. Therefore, the developed method, which employs CTE to calculate the temperature, has a higher reliability. In the present study, the efficiency of this method is tested by the orthogonal turning of difficult-to-cut martensitic heat-treated steel with a cemented tungsten carbide tool. Through the experiment, the temperature distributions along the rake face and flank of the tool, as well as the temperature field inside the tool, were obtained. The results can improve the temperature field measurement in machining cutting tools.