The review on effect of a high strain rate on the properties of TiNi-shape memory alloys is presented. The study of thermo-mechanical and functional properties of SMA after high strain rate loading was carried out. The object of study was an equiatomic TiNi shape memory alloy. The samples were tensioned at a strain rate of about 103s-1at various temperatures in martensitic, austenitic, and two-phase state, using the Split Hopkinson Pressure Bar technique. Two-way shape memory effects were investigated. Two-way shape memory after high strain rate loading was less than after the quasi-static one for all cases, except for straining in martensitic state.
This paper presents an investigation of the influence of strain rate on the functional behaviour of TiNi alloy. Specimens were deformed in compression and tension modes using the Kolsky method for a split Hopkinson pressure bar, and its modification in martensitic, austenitic, and pre-martensitic states at 500, 1000, and 1500 s−1 strain rates. One-way shape memory and two-way shape memory (TWSM) effects were measured and compared with ones after quasi-static deformation. With an increase in the strain rate, the one-way shape memory effect decreased, but the TWSM effect increased. Functional behaviour indirectly demonstrated the sensitivity of the martensite reorientation and the formation of stress-induced martensite to strain rate. Strain rate sensitivity led to differences in the shape recovery curves during thermocycling.
In this paper is described the mechanical characterization at high strain rate of the high strength steel usually adopted for strands. The experimental set-up used for high strain rates testing: in tension and compression was the Split Hopkinson Pressure Bar installed in the Laboratory of Dynamic Investigation of Materials in Nizhny Novgorod. The high strain rate data in tension was obtained with dog-bone shaped specimens of 3mm in diameter and 5mm of gauge length. The specimens were screwed between incident and transmitter bars. The specimens used in compression was a cylinder of 3mm in diameter and 5mm in length. The enhancement of the mechanical properties is quite limited compared the usual reinforcing steels.
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