Study on the mechanical properties of TiNi shape memory alloy wires using mark shearing system

The Shape memory alloys (SMAs) wires have been used for medical and engineering filed due to the shape memory effect and the superelasticity effect. It is necessary to measure the mechanical properties of the SMA wires accurately. In this paper the mechanical properties of the shape memory alloy wires with different diameters were studied by a self-made testing system. A loading apparatus driven by step motor was used to apply load, and a load cell with the accuracy of 10 mN and the capacity of 90N was used to measure the value of the load. An optical extensometer based on the mark shearing method was used to measure the strain of the SMA wires, which had accuracy with 5 micron-strains in strain measurement. The mechanical properties of the shape memory alloy wires were studied. The nominal stress-strain curves of the SMA wires were acquired. The superelasticity effect was also studied. The successful experimental results also demonstrated the feasibility of the system in silk-like specimen measurement.