NONLINEAR ANELASTICITY OF STRESS INDUCED MARTENSITIC TRANSFORMATION IN A COPPER-15ALUMINUM-3NICKEL ALLOY (INTERNAL FRICTION, SHAPE MEMORY ALLOY)

The dynamics of stress induced martensitic transformation in a Cu-15Al-3Ni alloy (A(,f) = 17(DEGREES)C) has been studied with finite amplitude internal friction. The resonance curves of a reed were measured in vacuum at resonance frequencies of 9, 22, 40 and 60 Hz and at temperatures of 93, 53, 23, -2 and -12(DEGREES)C. The frequency response equation resulting from the theory of the nonlinear anelasticity extended to 4th order was used to analyze the resonance curves quantitatively. The linear damping showed a pronounced peak at 9 Hz and a small peak at 22 Hz at -2(DEGREES)C. The 3rd order nonlinear damping displayed a large increase and the 3rd order nonlinear elastic constant showed a steep decrease as the temperature approached the A(,f) for all the resonance frequencies investigated. The anomalous temperature dependence of the linear damping and that of the ratio of the 3rd order nonlinear damping divided by the 3rd order nonlinear elastic constant at 9 Hz could be interpreted in terms of the dynamics of a system governed by a double well potential.