P. Sittner, V. Novak, L. Heller, Institute of Physics Academy of Sciences of the Czech Republic, Prague, Czech Republic; M. Landa, P. Sedlak, Institute of Thermomechanics Academy of Sciences of the Czech Republic, Prague, Czech Republic
| Functional properties of NiTi are very sensitive to the chemical composition and thermomechanical treatments, which affect their thermodynamic characteristics and microstructure. Some novel engineering applications (e.g. smart textiles with NiTi wires) require usage of ultrathin wires (d<20mm). These wires have become available only recently. Compared to the standard wires, they commonly have finer microstructure, exhibit different properties (e.g. higher strength and flat plateaus) and require usage of special experimental equipments. In this work, selected experimental results achieved in frame of a recently started research program focused on NiTi thin wires and smart textiles are reported. Two basic kinds of tests - thermal cycling at constant stress level and stress-strain cycling in tension at constant temperatures – were performed on several thin NiTi wires. Electric resistance and propagation speed of acoustic waves were measured during the tests. Two earlier developed models of NiTi thermomechanical behaviours were updated to capture the observed responses. |
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Ultrathin NiTi wires (d<0.02mm) are needed for development of smart textiles. These wires have become available only recently, have commonly finer microstructure, exhibit slightly different properties compared to standard wires. In this work, several such wires were investigated in thermomechanical tests with simultaneous measurements of electric resistance and speed of propagating acoustic waves. The results are interpreted with the help of earlier developed mechanics models.
