| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1758964 | Ultrasonics | 2014 | 6 Pages |
•Variation in flow stress at insonation of TiNi alloy is due to non-monotonic dependence of yield stress on temperature.•Variation in value of shape memory effects is caused by alternate stresses induced by the ultrasonic vibration.•Action of ultrasonic on shape memory alloys is due to an increase in temperature and creation of alternate stresses.
It is known that the main factors in a variation in the shape memory alloy properties under insonation are heating of the material and alternate stresses action. In the present work the experimental study of the mechanical behaviour and functional properties of shape memory alloy under the action of alternate stresses and varying temperature was carried out. The data obtained had demonstrated that an increase in temperature of the sample resulted in a decrease or increase in deformation stress depending on the structural state of the TiNi sample. It was shown that in the case of the alloy in the martensitic state, a decrease in stress was observed, and on the other hand, in the austenitic state an increase in stress took place. It was found that action of alternate stresses led to appearance of strain jumps on the strain–temperature curves during cooling and heating the sample through the temperature range of martensitic transformation under the constant stress. The value of the strain jumps depended on the amplitude of alternate stresses and the completeness of martensitic transformation. It was shown that the heat action of ultrasonic vibration to the mechanical behaviour of shape memory alloys was due to the non-monotonic dependence of yield stress on the temperature. The force action of ultrasonic vibration to the functional properties was caused by formation of additional oriented martensite.
