NONLINEAR EFFECTS IN THE SNOEK RELAXATION OF NB-O

Internal friction peaks measured as a function of temperature or frequ ency have been associated to non-linear processes only after studying how the amplitude of the applied stress affects the relaxation process . Here it is demonstrated that the partial derivative of the internal friction with respect to the frequency at constant temperature is a us eful tool to determine that non-linear effects are involved. This anal ysis applied to actual data of the Snoek relaxation in Nb-O, reveals t hat at high interstitial contents non-linear effects appear.