Mathematical model of strip specimens for application of pulse-heating technique

The dynamic measurement of selected thermophysical properties of electrically conducting solids in the temperature range of 1100 K to the melting point was conducted using strip specimens, for simultaneous measurement of the normal spectral emissivity by using integrating sphere reflectometry. The method is based on rapid resistive self-heating of the specimen from room temperature to any desired high temperature in less than several seconds by the passage of an electical current pulse through it to measure the pertinent quantities, as current, voltage, and randiance temperature, with sub-millisecond resolution. The estimation of heat capacity and hemispherical total emissivity is based on various computational methods derived by assuming that the temperature was uniform in the central part of the specimen. The validity of this approach was verified when specimens with large cross sections and when the temperature on the specimen surface was measured. A numerical model was established with the temperature variations across the specimen was taken into consideration. The mathematical model established can be used in the simulation experiments to access the magnitude of specific phenomena due to the temperature gradient inside the specimen, in relation to the specimen geometry and to the specific thermophysical properties of different materials.