Back stress and shape recoverability during reverse transformation in an Fe-based shape memory alloy

1998 ◽  
Vol 247 (1-2) ◽  
pp. 275-284 ◽  
Author(s):  
Fumihito Nishimura ◽  
Noriko Watanabe ◽  
Kikuaki Tanaka
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Back Stress ◽  
Reverse Transformation

Transformation/Deformation Behavior and its Constitutive Equation for Ti-Ni-Cu Shape Memory Alloy

2008 ◽  
Vol 59 ◽  
pp. 129-134
Author(s):  
Yuji Takeda ◽  
Takaei Yamamoto ◽  
M. Uegaki ◽  
Hiroki Cho ◽  
Toshio Sakuma ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Constitutive Equation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Constitutive Equations ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
Transformation Process ◽  
Reverse Transformation ◽  
Transformation Behavior

This paper describes the transformation and deformation behavior and its constitutive equation for Ti-41.7Ni-8.5Cu (at%) shape memory alloy. Plastic deformation after pre-deformation is investigated using the volume fraction of slip-deformed martensite. New kinetics and constitutive equations are proposed for the reverse transformation process. The material constants in the proposed equationa are determined from the results of tensile and heating/cooling tests of Ti-41.7Ni-8.5Cu (at%) shape memory alloy. The calculated results describe well the deformation and transformation behavior affected by pre-strain.

Observation of field-induced reverse transformation in ferromagnetic shape memory alloy Ni50Mn36Sn14

2006 ◽  
Vol 88 (13) ◽  
pp. 132505 ◽  
Author(s):  
Keiichi Koyama ◽  
Kazuo Watanabe ◽  
Takeshi Kanomata ◽  
Ryosuke Kainuma ◽  
Katsunari Oikawa ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Reverse Transformation ◽  
Ferromagnetic Shape Memory Alloy ◽  
Ferromagnetic Shape Memory

Thermomechanical modeling and experimental investigation of transformation-induced creep and stress relaxation in shape memory alloy wires

2016 ◽  
Vol 28 (7) ◽  
pp. 923-933 ◽  
Author(s):  
Fateme Zare ◽  
Mohammad Jannesari ◽  
Mahmoud Kadkhodaei ◽  
Peiman Mosaddegh
Keyword(s):  
Stress Relaxation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Reverse Transformation ◽  
Creep Recovery ◽  
Thermomechanical Model ◽  
Ambient Temperatures ◽  
Relaxation Responses ◽  
Creep And Stress Relaxation

Creep and relaxation phenomena are being observed in shape memory alloys, not only at high temperatures but also at room temperature, due to their martensitic transformation. Transformation-induced creep and stress relaxation in shape memory alloys occur due to temperature variations during loading and unloading cycles. In this work, a one-dimensional fully coupled thermomechanical model was employed to develop a continuum framework for studying these behaviors in shape memory alloy wires. A decrease or increase in stress was observed during forward or reverse transformation at a constant amount of strain, showing the stress relaxation and stress recovery, respectively. Similarly, the model predicts that strain increases or decreases when stress is held fixed in the course of forward or reverse transformation, meaning the phenomena of creep and creep recovery, respectively. This model provides the ability of investigating the effects of different ambient temperatures, strain rates, applied stresses and strains, and wire radii on the creep and relaxation responses of shape memory alloys. Relaxation and creep experiments at different ambient temperatures and loading or unloading rates were also done on NiTi wires, and the theoretical predictions were shown to be in a good agreement with the empirical observations.

Two-Way Memory Effect in NiTi Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 77-85 ◽  
Author(s):  
Kiyohide Wada ◽  
Yong Liu
Keyword(s):  
Shape Memory ◽  
Internal Stress ◽  
Memory Effect ◽  
Back Stress ◽  
Nucleation And Growth ◽  
Reverse Transformation ◽  
Thermal Arrest ◽  
Accommodation Process ◽  
Stress Formation ◽  
Niti Shape Memory Alloys

In general, the development mechanisms of TWME have long been understood as the nucleation and growth of preferentially oriented martensite guided by the internal stress. This work extends the study by investigating the effects of martensite deformation, constrained stress and retained martensite via partial reverse transformation through thermal arrest during heating on the stress-assisted two-way memory effect (SATWME) and TWME. It was observed that the generation of maximum SATWME was caused by the development of optimum internal stress. The increase of internal stress was accompanied by the increase of martensitic strain resulting from constrained cooling. When the martensitic strain exceeded the initial pre-strain, it directly influenced on the magnitudes of SATWME and TWME. The accommodation process of stress-assisted and detwinned martensite variants as a result of partial reverse transformation caused the formation of internal forward and back stresses. TWME was promoted by the dominant internal forward stress formation, while the dominance of internal back stress decreased the TWME by decreasing the martensitic strain.

Effect of stress redistribution during thermal actuation of shape memory alloys in notched cylindrical bars

2018 ◽  
Vol 29 (10) ◽  
pp. 2149-2163 ◽  
Author(s):  
Francis R Phillips ◽  
Dimitris C Lagoudas
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Phase ◽  
Reverse Transformation ◽  
Cylindrical Shape ◽  
Austenitic Phase ◽  
Thermal Actuation ◽  
Forward Transformation

Shape memory alloys present a unique ability to undergo a solid-to-solid, diffusionless, reversible phase transformation. The forward phase transformation is commonly associated with transforming from the austenitic phase to the martensitic phase, while the reverse transformation is defined by going from the martensitic phase to the austenitic phase. In thermal actuation loading paths, forward transformation is generally associated with cooling, while reverse transformation is commonly associated with heating. In this article, however, it is shown that reverse transformation may occur during cooling of notched cylindrical shape memory alloy bars. The reversal in phase transformation is associated with the redistribution of stress in the shape memory alloy due to the phase transformation.

scholarly journals Observation of Reverse Transformation in Metamagnetic Shape Memory Alloy Ni40Co10Mn34Al16 by High-Field X-Ray Diffraction Measurements

2010 ◽  
Vol 51 (9) ◽  
pp. 1648-1650 ◽  
Author(s):  
Yoshifuru Mitsui ◽  
Keiichi Koyama ◽  
Wataru Ito ◽  
Rie Y. Umetsu ◽  
Ryosuke Kainuma ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Field ◽  
Reverse Transformation ◽  
X Ray Diffraction ◽  
X Ray
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