Flying-spot thermography: measuring the in-plane (an)isotropic thermal diffusivity of large and complex parts

Abstract

We present a methodology to measure the in-plane thermal diffusivity of (an)isotropic samples using flying spot thermography. We obtain an analytical expression for the surface temperature distribution when a continuous wave laser spot scans the sample surface at constant velocity. By analyzing this expression, we propose three simple methods to measure the thermal diffusivity in the directions parallel and perpendicular to the motion. The methodology can also be applied in the case where the laser spot is at rest, and the specimen moves at constant velocity. This configuration is interesting for in-line evaluation of industrial products. Finally, we present a set-up allowing the inspection of large and complex parts, by means of a robotic arm used to displace the part and orient the region of interest perpendicular to the optical axis of the camera.