A multiproperty method and apparatus for thermophysical measurements on solids

A new method for the simultaneous measurement of different thermophysical properties of elastic solids is presented. The method exploits the temperature variations induced, via the thermoelastic effect, by elastic deformations of a specimen. A homogeneous effective heat source-proportional to the thermal expansion coefficient and to the stress rate-is fed into a cylindrical sample by a uniaxial and uniform compression stage followed by a thermal relaxation at constant stress, the specimen temperature being detected by miniature sensors. An experimental setup has been developed and patented, achieving simple thermal boundary conditions and allowing solution in closed form of the Fourier equation describing the whole transient: from the experimental curve it is possible to determine both the thermal diffusivity and the ratio of thermal expansion coefficient to specific heat. Extensive experimentation was conducted in order to optimise specimen preparation and testing procedures, and to develop criteria for data analysis. The technique was finally validated by reference materials, including Certified Reference Materials (CRMs) for various thermophysical properties, precisely assessing uncertainty and accuracy of method. Metallic and ceramic materials with thermal properties varying in a wide range have been tested, obtaining precisions comparable to those of established methods.