Nonuniform transformation behaviour of NiTi in a discrete geometrical gradient design

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Abstract

Shape memory alloys exhibit unique thermomechanical properties, e.g., the shape memory effect and the pseudoelasticity. By proper geometrical gradient design, these alloys can be made to exhibit different and more intricate thermomechanical behaviour to enable innovative applications. This paper reports the design of geometrically gradient NiTi and characterisation of its complex and nonuniform transformation and deformation fields. The study investigated two designs, with one using multiple pseudoelastic NiTi strips of different lengths in parallel arrangement to create a discrete geometrical gradient in the direction perpendicular to the loading axis and the other a tapered plate to give a continuous length gradient in the lateral direction for comparison with the former. The geometrically gradient structures exhibited partial stress gradient during stress-induced transformation. A maximum stress window of 520 MPa was achieved, giving an expanded stress interval for shape memory actuation control. Finite element modelling was applied to characterise the deformation behaviour of such structures under tensile loading and to reveal the complex propagation of the stress-induced transformation in such structures. © 2018

Original languageEnglish
Pages (from-to)1260-1266
JournalJournal of Alloys and Compounds
Volume774
DOIs
Publication statusPublished - Feb 2019

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@article{b30eb5d147114628868134088596f6f0,
title = "Nonuniform transformation behaviour of NiTi in a discrete geometrical gradient design",
abstract = "Shape memory alloys exhibit unique thermomechanical properties, e.g., the shape memory effect and the pseudoelasticity. By proper geometrical gradient design, these alloys can be made to exhibit different and more intricate thermomechanical behaviour to enable innovative applications. This paper reports the design of geometrically gradient NiTi and characterisation of its complex and nonuniform transformation and deformation fields. The study investigated two designs, with one using multiple pseudoelastic NiTi strips of different lengths in parallel arrangement to create a discrete geometrical gradient in the direction perpendicular to the loading axis and the other a tapered plate to give a continuous length gradient in the lateral direction for comparison with the former. The geometrically gradient structures exhibited partial stress gradient during stress-induced transformation. A maximum stress window of 520 MPa was achieved, giving an expanded stress interval for shape memory actuation control. Finite element modelling was applied to characterise the deformation behaviour of such structures under tensile loading and to reveal the complex propagation of the stress-induced transformation in such structures. {\circledC} 2018",
keywords = "Shape memory alloy (SMA), Martensitic transformation, NiTi, Functionally graded material (FGM), geometrical gradient, Pseudoelasticity",
author = "{Samsam Shariat}, Bashir and Reza Bakhtiari and Yinong Liu",
year = "2019",
month = "2",
doi = "10.1016/j.jallcom.2018.09.116",
language = "English",
volume = "774",
pages = "1260--1266",
journal = "Journal of Alloys and Compounds",
issn = "0925-8388",
publisher = "Elsevier Science & Technology",

}

TY - JOUR

T1 - Nonuniform transformation behaviour of NiTi in a discrete geometrical gradient design

AU - Samsam Shariat, Bashir

AU - Bakhtiari, Reza

AU - Liu, Yinong

PY - 2019/2

Y1 - 2019/2

N2 - Shape memory alloys exhibit unique thermomechanical properties, e.g., the shape memory effect and the pseudoelasticity. By proper geometrical gradient design, these alloys can be made to exhibit different and more intricate thermomechanical behaviour to enable innovative applications. This paper reports the design of geometrically gradient NiTi and characterisation of its complex and nonuniform transformation and deformation fields. The study investigated two designs, with one using multiple pseudoelastic NiTi strips of different lengths in parallel arrangement to create a discrete geometrical gradient in the direction perpendicular to the loading axis and the other a tapered plate to give a continuous length gradient in the lateral direction for comparison with the former. The geometrically gradient structures exhibited partial stress gradient during stress-induced transformation. A maximum stress window of 520 MPa was achieved, giving an expanded stress interval for shape memory actuation control. Finite element modelling was applied to characterise the deformation behaviour of such structures under tensile loading and to reveal the complex propagation of the stress-induced transformation in such structures. © 2018

AB - Shape memory alloys exhibit unique thermomechanical properties, e.g., the shape memory effect and the pseudoelasticity. By proper geometrical gradient design, these alloys can be made to exhibit different and more intricate thermomechanical behaviour to enable innovative applications. This paper reports the design of geometrically gradient NiTi and characterisation of its complex and nonuniform transformation and deformation fields. The study investigated two designs, with one using multiple pseudoelastic NiTi strips of different lengths in parallel arrangement to create a discrete geometrical gradient in the direction perpendicular to the loading axis and the other a tapered plate to give a continuous length gradient in the lateral direction for comparison with the former. The geometrically gradient structures exhibited partial stress gradient during stress-induced transformation. A maximum stress window of 520 MPa was achieved, giving an expanded stress interval for shape memory actuation control. Finite element modelling was applied to characterise the deformation behaviour of such structures under tensile loading and to reveal the complex propagation of the stress-induced transformation in such structures. © 2018

KW - Shape memory alloy (SMA)

KW - Martensitic transformation

KW - NiTi

KW - Functionally graded material (FGM)

KW - geometrical gradient

KW - Pseudoelasticity

U2 - 10.1016/j.jallcom.2018.09.116

DO - 10.1016/j.jallcom.2018.09.116

M3 - Article

VL - 774

SP - 1260

EP - 1266

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

ER -