Analysis of dependence of internal damping on temperature of austenitic steels

The processes of microplasticity and energy scattering inside the material are analyzed by measuring the internal damping. The mechanism of microplasticity can be evaluated by various dependencies – frequency, time, temperature and amplitude dependencies that characterize the kinetics of accumulation of fatigue damage under long-term load. By measuring the energy scattering in the material, the elastic characteristics, the modulus of elasticity, the degree of stress relaxation in the material can be determined. The ability of a solid to irreversibly disperse energy under mechanical stress is called the internal damping. The time required to achieve the equilibrium deformation value is determined by various processes associated with the reallocation of atoms, magnetic moments and the temperature of the solid subjected to external stresses. The internal damping mechanisms have been studied by ultrasonic resonant apparatus at a frequency close to 20450 Hz and in a temperature range from 30 °C up to 400 °C. Specimens of an hour glass shape were used for experiments. Measurement of internal damping dependence on temperature was performed on austenitic steels AISI 316L, AISI 316Ti and AISI 304, in the initial state and after the deformation. Those materials are commercially available stainless steels, which are very often used as biomaterials in medicine.