<title>Thermal diffusivity imaging with a moving line source</title>

Abstract

The thermal line scan technique has been shown to be an effective technique for rapid inspection of aerospace specimens. Past efforts have focused on thermal measurements far behind the line source where the heat flow normal to the surface is negligible. This paper focuses on measurements closer to the line source to enable the measurement of the thermal diffusivity in the surface normal direction. This measurement also enables an independent characterization of the thermal diffusivity in the direction of motion of the thermal line source. An analytical solution is given for a line source moving with constant velocity across an anisotropic plane. A nonlinear least squares fitting routine is used to reduce the temporal response of a specimen to images of the thermal diffusivity in both the directions normal to the surface and parallel to the motion of the line source. Measurements are presented on specimens with known variations in effective diffusivity. Measurements on these specimens allow a comparison of this technique to more conventional techniques for diffusivity measurement.