Study of Mechanical Behaviour in Shape Memory Alloys Through Adiabatic Thermal Emission and Acoustic Emission Technique

Abstract
Tensile tests were carried out on commercially available NiTi alloys in order to study their mechanical characteristics up to the onset of the superelasticity effect. Two realtime supporting techniques, adiabatic thermal emission and acoustic emission, were employed. Thermal emission allowed to follow local temperature variations in the material due to loading, while acoustic emission was able to detect the propagation of related stress wave. When the material is subjected to repeated loading and provided that test conditions remain the same, compared results from these two techniques could enhance the knowledge of material behaviour. A difficulty lies however in the choice of experimental conditions apt to a successful application of both techniques. Thermal emission in fact has to be performed during a quasi-adiabatic test, while acoustic emission has different requirements, needing in particular a sufficient loading time to allow stresses distribution. Results are promising as a preliminary assessment and could prospectively provide a persuasive quality discrimination.