抄録
The stress-strain curve of Ti-Ni alloy on pseudoelasticity forms a hysteresis loop, and there appear large amounts of recoverable strain energy and dissipated strain energy. The experiments on a wire under cyclic uniaxial tension were carried out and the influences of test temperature, maximum strain and shape memory processing temperature on the cyclic behaviors of these strain energies were investigated. The results obtained are summarized as follows.
(1) The recoverable strain energy was large as the test temperature became high, and decreased with the number of cycles.
(2) The dissipated strain energy depended little on the test temperature for small maximum strain, but decreased significantly in the early cycles at low test temperatures if the maximum strain was larger than the range of stress-induced martensitic transformation.
(3) Among the attenuation rates of various strain energies under cyclic deformation, the attenuation rate of dissipated strain energy was largest. The variation of attenuation rate of every strain energy was significant in the early cycles, but became almost constant after the 20th cycle. This means that the training before the actual use is effective for the cyclic stability of each strain energy.
(4) The rate of strain energy storage increased with the number of cycles, but the rate of strain energy dissipation decreased.
(5) Both recoverable strain energy and dissipated strain energy were large as the maximum strain became large in the early cycles. If the maximum strain was in the range of stress-induced martensitic transformation, each strain energy for the 100th cycle became almost a constant value.
(6) The recoverable strain energy was small as the shape memory processing temperature became high. The dissipated strain energy was large as the shape memory processing temperature became high in the early cycles, but became largest at 673K of shape memory processing temperature for the 100th cycle.
