A study on strain-sense and actuated properties of tini shape memory alloys

Tests are conducted in MTS-810 and the testing system developed personally for strain-sense and thermomechanical properties of TiNi shape memory alloys (SMAs). Test results of resistance variation and restrained recovery stress of TiNi SMA wires are presented and discussed. It can be concluded that TiNi SMA wires have good strain-sense property. The change rate of resistance of TiNi SMA wires has a linear relation with the applied strain, whose sensitivity coefficient is much higher than that of the common strain gauge. Recover stresses are generated upon heating due to reverse martensitic transition. The TiNi SMA wires having 5% maximum prestretching strain can generate larger restrained recovery stress than those having 3%, when heating by the same electrical current. Large constant electrical current and relatively large maximum prestretching strain can result in high recovery stress rate dsigma/dT in phase transition process. Furthermore, in maintaining the same maximum prestretching strain, maximum restrained recovery stress is almost identical for different constant electrical currents. This study is devoted to damage detection and damage emergency repair of the structures embedded with TiNi shape memory alloy wires.