Measurement of thermal diffusivity by a modification of the Angstroem's method using thermally short specimens

A modification of the Angstroem's method for measurement of thermal diffusivity is presented. The Angstroem's method relies upon the steady-periodic propagation of temperature waves along the specimen. The diffusivity is recovered from combination of phase shift and amplitude decay of the waves, measured by infrared thermography, under the hypothesis of virtually semi-infinite specimen, that is neglecting the reflection of temperature waves at the end of the specimen. In this work, a condition is exploited in which the specimen is not considered semi-infinite. Testing of a large set of materials is made possible, as well as recovering the diffusivity value from either amplitude decay or phase shift, independently. A procedure to estimate the diffusivity is developed from the mathematical model of the 'thermally short' specimen and it is subsequently validated by numerical simulation.