Modeling of SMA superelastic behavior with nonlocal approach

Polycrystalline copper-based shape memory alloys have been of particular interest in relation to Ni-Ti because of their low cost and good shape memory effect. Nevertheless the absence of a pronounced pseudoelasticity effect restricts the number of potential applications. In this work, the influence of Nb and V on the microstructure and the mechanical properties was investigated. Samples of Cu-13.8 Al-Ni containing V and Nb alloy were prepared by induction and solution treated at 850°C and then further quenched into cold water. The addition of Nb and V promotes the formation of precipitates which act as grain refiner and subsequently improve the mechanical properties. The tensile tests were performed at temperatures slightly inferior to Mf and superior to Af, to investigate the shape recovery and pseudoelasticity, respectively. Based on the analyses of the Cu-13,8Al-2Ni-1Nb (wt%) alloy was detected rupture strains greater than 14%, besides observation of the superelasticity of these alloys and quantification of this property by means of cycling, from 0 to strains between 1 and 7%. The studies performed on alloy Cu-13.8Al- 3,5Ni-1V (wt%) made it possible to determine rupture strains in the order of 3% and its superelastic behavior through cycling for deformations between 1 and 3%.

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Influence of Omega-Phase Precipitation Hardening on the Static and Dynamic Properties of Metastable Beta Ti-Nb-Zr and Ti-Nb-Ta Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.738-739.189 ◽

2013 ◽

Vol 738-739 ◽

pp. 189-194 ◽

Cited By ~ 4

Author(s):

Vladimir Brailovski ◽

Sergey Prokoshkin ◽

Karine Inaekyan ◽

Sergey Dubinskiy

Keyword(s):

Mechanical Behavior ◽

Volume Fraction ◽

Thermomechanical Processing ◽

Subgrain Size ◽

Dynamic Properties ◽

Aging Treatment ◽

Stress Generation ◽

Phase Precipitation ◽

Superelastic Behavior ◽

Temperature Scanning

The influence of thermomechanical processing on the Ti-21.8Nb-6Zr (TNZ) and Ti-19.7Nb-5.8Ta (TNT) (at%) alloys’ structure, phase composition, mechanical and functional properties is studied. Both alloys possess polygonized dislocation substructure (average subgrain size  100 nm), and manifest superelastic behavior at room temperature and recovery stress generation during constant-strain temperature scanning experiments. After aging treatment, both alloys were -phase precipitation hardened, but their mechanical behavior was impacted differently -- it was detrimental for TNZ and beneficial for TNT. The different impact of aging heat treatment on the mechanical behavior of these alloys is explained by the differences in the -phase nucleation rate, precipitates’ size, shape, volume fraction and distribution, and by their effect on the alloys’ critical stresses and transformation temperatures.

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An SMA Passive Ankle Foot Orthosis: Design, Modeling, and Experimental Evaluation

Smart Materials Research ◽

10.1155/2014/572094 ◽

2014 ◽

Vol 2014 ◽

pp. 1-11 ◽

Cited By ~ 12

Author(s):

Liberty Deberg ◽

Masood Taheri Andani ◽

Milad Hosseinipour ◽

Mohammad Elahinia

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Motion Analysis ◽

Experimental Evaluation ◽

Mechanical Systems ◽

Drop Foot ◽

Ankle Foot Orthosis ◽

New Device ◽

Superelastic Behavior ◽

Foot Orthosis

Shape memory alloys (SMAs) provide compact and effective actuation for a variety of mechanical systems. In this work, the distinguished superelastic behavior of these materials is utilized to develop a passive ankle foot orthosis to address the drop foot disability. Design, modeling, and experimental evaluation of an SMA orthosis employed in an ankle foot orthosis (AFO) are presented in this paper. To evaluate the improvements achieved with this new device, a prototype is fabricated and motion analysis is performed on a drop foot patient. Results are presented to demonstrate the performance of the proposed orthosis.

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