Theoretical aspects of the Bordoni relaxation

Numerical calculation are made of internal friction due to the thermally activated formation of double-kinks (Seeger-Paré model), by applying the rate theory without making approximations. All the characteristics of the Bordoni relaxation are well explained by this model. In particular, a distribution of internal stresses and dislocation lengths leads to a peak broadening which may be of about 3 to 4. Besides, the model gives important non-linear effects: the stresses (internal or applied) must satisfy the Paré condition, the peak temperature is reduced when the stress increases, the peak is shifted towards high temperatures when the loop length increases and the relaxation strength presents a maximum as a function of stress.