APPARATUS FOR HIGH-TEMPERATURE INTERNAL-FRICTION DIFFERENTIAL MEASUREMENTS

We present a new internal friction pendulum conceived and built to work at high temperature (up to 1800 K) with forced vibrations allowing measurements as a function of the frequency (from 10-4 to 10 Hz) as well as the temperature. The main difference with previous constructions is that data are obtained by comparison of the specimen deformation with the deformation of an elastic standard, instead of comparing with the excitation signal. At first we describe the mechanical part and the computed control of all the parameters during measurements. Then we present the first tests that show the great sensitivity of the measurements due to the quality of the mechanics and to the principle of differential acquisition. We also present the interest of internal friction tests to study the behavior of materials for which the plasticity appears at high temperatures (carbides, ceramics).