28 March 2012 Evolution of phase transformation and reorientation during stress arrest in shape memory alloys
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Abstract
Stress arrest of loading or unloading during pseudoelastic phase transformations in shape memory alloys has shown to exhibit creep-like phenomenon even at strain rates that can be considered quasi-static and devoid of any thermal effects. This phenomenon termed as pseudo-creep is manifested as positive (negative) accumulation in strain during loading (unloading) when arrested at constant stress. Pseudo-creep is also found to occur during reorientation loading, where thermomechanical coupling is absent. In this paper, we report results of extensive studies conducted on poly-crystal Ni-Ti wires for stress arrest of loading and unloading at normalized strain rates ranging from 4.25E-7 (virtually isothermal conditions) to 4.25E-5 in conjunction with a video multi-extensometry technique developed in our laboratory to measure spatially non-uniform deformations in the sample and have recorded evolution in phase transformations or reorientation in three consecutive segments of the wire (constituting the total gauge length for video multi-extensometry) during stress arrest.
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V. R. Russalian, V. R. Russalian, A. Bhattacharyya, A. Bhattacharyya, } "Evolution of phase transformation and reorientation during stress arrest in shape memory alloys", Proc. SPIE 8342, Behavior and Mechanics of Multifunctional Materials and Composites 2012, 83421P (28 March 2012); doi: 10.1117/12.915433; https://doi.org/10.1117/12.915433
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