STUDY OF MECHANICAL-BEHAVIOR IN SHAPE-MEMORY ALLOYS THROUGH ADIABATICTHERMAL EMISSION AND ACOUSTIC-EMISSION TECHNIQUE

Tensile tests were called out on commercially available NiTi alloys in order to study their mechanical characteristics up to the onset of th e superelasticity effect. Two real-time supporting techniques, adiabat ic thermal emission and acoustic emission, were employed. Thermal emis sion allowed to follow local temperature variations in the material du e to loading, while acoustic emission was able to detect the propagati on of related stress wave. When the material is subjected to repeated loading and provided that test conditions remain the same, compared re sults from these two techniques could enhance the knowledge of materia l behaviour. A difficulty lies however in the choice of experimental c onditions apt to a successful application of both techniques. Thermal emission in fact has to be performed during a quasi-adiabatic test, wh ile acoustic emission has different requirements, needing in particula r a sufficient loading time to allow stresses distribution. Results ar e promising as a preliminary assessment and could prospectively provid e a persuasive quality discrimination.