Conventional Plasticity Constitutive Model for Shape Memory Alloys

2011 ◽  
Vol 216 ◽  
pp. 469-473
Author(s):  
Hai Tao Li ◽  
Xiang He Peng
Keyword(s):  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Numerical Algorithm ◽  
Individual Behavior ◽  
Two Phase ◽  
The Individual

A two-phase constitutive model for shape memory alloys (SMAs) is proposed based on the fact that SMAs is dynamically composed of austenite and martensite. The behavior of SMAs is regarded as the dynamic combination of the individual behavior of each phase. This model can describe the main characteristics of SMAs, such as pseudoelasticity and shape memory effect. The corresponding numerical algorithm was also developed to describe the main features of shape memory alloy Au-47.5at.%Cd.

Cold Bending a Ni-Ti Shape Memory Alloy Wire

2015 ◽  
Vol 661 ◽  
pp. 98-104 ◽  
Author(s):  
Kuang-Jau Fann ◽  
Pao Min Huang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Room Temperature ◽  
Aging Treatment ◽  
Treatment Temperature ◽  
Bending Test ◽  
Solution Treatment Temperature

Because of being in possession of shape memory effect and superelasticity, Ni-Ti shape memory alloys have earned more intense gaze on the next generation applications. Conventionally, Ni-Ti shape memory alloys are manufactured by hot forming and constraint aging, which need a capital-intensive investment. To have a cost benefit getting rid of plenty of die sets, this study is aimed to form Ni-Ti shape memory alloys at room temperature and to age them at elevated temperature without any die sets. In this study, starting with solution treatments at various temperatures, which served as annealing process, Ni-rich Ni-Ti shape memory alloy wires were bent by V-shaped punches in different curvatures at room temperature. Subsequently, the wires were aged at different temperatures to have shape memory effect. As a result, springback was found after withdrawing the bending punch and further after the aging treatment as well. A higher solution treatment temperature or a smaller bending radius leads to a smaller springback, while a higher aging treatment temperature made a larger springback. This springback may be compensated by bending the wires in further larger curvatures to keep the shape accuracy as designed. To explore the shape memory effect, a reverse bending test was performed. It shows that all bent wires after aging had a shape recovery rate above 96.3% on average.

A Three-Phase Constitutive Model for TiNiNb Shape Memory Alloys

2010 ◽  
Vol 97-101 ◽  
pp. 660-666
Author(s):  
Jun Wang ◽  
Zhi Ming Hao ◽  
Ping An Shi ◽  
Shao Rong Yu ◽  
Wei Fen Li
Keyword(s):  
Phase Transition ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Conventional Theory ◽  
Material Parameters ◽  
Three Phase ◽  
The Individual

A three-phase constitutive model for TiNiNb shape memory alloys (SMAs) is proposed based on the fact that TiNiNb SMAs are dynamically composed of austenite, martensite and -Nb phases. In the considered ranges of stress and temperature, the behaviors of austenite, martensite and -Nb phases are assumed to be elastoplastic, and the behavior of an SMA is regarded as the dynamic combination of the individual behavior of each phase. Then a macroscopic constitutive description for TiNiNb SMAs is obtained by the conventional theory of plasticity, the theory of mixture, the theory of inclusion, and the description of phase transition by Tanaka. The method for determination of the material parameters is given. This constitutive model can describe the main characteristics of SMAs, such as ferrcelasticity, pseudoelasticity and shape memory effect.

A Constitutive Model for Shape Memory Alloys Involving Transformation, Reorientation and Plasticity

2013 ◽  
Vol 535-536 ◽  
pp. 105-108
Author(s):  
Xiang He Peng ◽  
Min Mei Chen ◽  
Jun Wang
Keyword(s):  
Plastic Deformation ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Volume Fraction ◽  
Transformation Rule ◽  
Constitutive Behavior ◽  
Plastic Parts

A constitutive model is developed for shape memory alloys (SMAs) based on the concept that an SMA is a mixture composed of austenite and martensite. The deformation of the martensite is separated into elastic, thermal, reorientation and plastic parts, and that of the austenite is separated into elastic, thermal and plastic parts. The volume fraction of each phase is determined with the modified Tanaka’s transformation rule. The typical constitutive behavior of some SMAs, including pseudoelasticity, shape memory effect, plastic deformation as well as its effects, is analyzed.

Effect of Aging on Mechanical Properties of Ti-Mo-Al Biomedical Shape Memory Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 2150-2153 ◽  
Author(s):  
Hideki Hosoda ◽  
Makoto Taniguchi ◽  
Tomonari Inamura ◽  
Hiroyasu Kanetaka ◽  
Shuichi Miyazaki
Keyword(s):  
Mechanical Properties ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Shape Recovery ◽  
Tensile Tests ◽  
Single Step ◽  
Two Phase ◽  
Solution Treated

Effects of single- and multi-step aging on mechanical properties and shape memory properties of Ti-6Mo-8Al (mol%) biomedical shape memory alloy were studied using tensile tests at room temperature (RT). The solution-treated alloy at RT was two phase of bcc β and martensite α". Tensile tests revealed that the solution-treated alloy exhibited good shape memory effect. As for the single-step aging, (1) pseudoelastic shape recovery by unloading was observed after aging at 623K, (2) the alloy became brittle after aging at 773K due to ω embrittlement, and (3) strength was improved with small shape memory effect by aging at 1023K. On the other hand, after a multistep aging at 773K-1023K-1123K, the alloy was strengthened and showed perfect shape recovery. The improvement must be achieved by the formation of fine and uniform hcp α precipitates.

Behavio of Supeaplastically Extruded Cu-26wt%Zn–3.5wt%Al Shape Memory Alloy

1990 ◽  
Vol 196 ◽  
Author(s):  
Zheng Zhengyt ◽  
Zhcng Weijian ◽  
Lin Fuzeng ◽  
Chew Yingsheng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Strain Rate ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Heat Treated

ABSTRACTThe influence of superplastic extrusion on the microstructures and the shape memory effect of the Cu-Zn-Al shape memory alloys has been investigated. The shape memory alloy Cu-26%wt%Zn-3.5wt%Al is superplastio with an index of strain rate sensitivity n = 0.48 at 600°C, at a strain of . After extrusion under the superplastio condition the miorostruotures are improved and no cavities are observed. The superplastically extruded specimens of this alloy were heat-treated to obtain the shape memory effect. These specimens indicate that no deterioration of shape memory effect of the alloy is induced by the superplastio extrusion and the shape memory effect of the alloy is somewhat improved.

Investigation of the Kinetic of a Bainitic Reaction upon Heating in a CuAlNiMn and a CuAlNiMnFe Shape Memory Alloy

2013 ◽  
Vol 752 ◽  
pp. 3-9 ◽  
Author(s):  
Marton Benke ◽  
Valéria Mertinger ◽  
Peter Barkoczy
Keyword(s):  
Solid State ◽  
Kinetic Model ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
One Stage ◽  
Shape Memory Behaviour ◽  
Memory Characteristics

The examination of solid state processes leading to the degradation of the shape memory behaviour is essential with respect to the suitability of shape memory alloys. Besides degradation processes occurring during relatively long periods of time called ageing, bainitic reactions that suddenly degrade the shape memory behaviour were also observed in many Cu-based shape memory alloys. The mechanisms and effects of the bainitic reactions on the shape memory characteristics were investigated in many Cu-based systems, but the kinetic of the reaction was not examined so far. In the present paper, an examination was carried out on a CuAlNiMn and a CuAlNiMnFe shape memory alloy to reveal what kinetic model describes the bainitic reaction occurring and thus completely destroying the shape memory effect during one stage of heating.

A Multidimensional Constitutive Model for Shape Memory Alloys

2014 ◽  
Vol 584-586 ◽  
pp. 1141-1144
Author(s):  
Wei Wang ◽  
Ji Yuan Liu
Keyword(s):  
Free Energy ◽  
Constitutive Model ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Dissipation Energy ◽  
Thin Walled

A multidimensional constitutive model for shape memory alloys (SMA) is developed in the paper, which is based on the thermodynamics theories of free energy and dissipation energy. This model can well describe both the shape memory effect (SME) and super elasticity effect (SE) of the thin-walled SMA cylinder under an axial tensional force and torsion.

Unexpected Constrained Twin Hierarchy in Equiatomic Ru-Based High Temperature Shape Memory Alloy Martensite

2013 ◽  
Vol 738-739 ◽  
pp. 195-199 ◽  
Author(s):  
Philippe Vermaut ◽  
Anna Manzoni ◽  
Anne Denquin ◽  
Frédéric Prima ◽  
Richard Portier
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensitic Transformations ◽  
Single Transition

Among the different systems for high temperature shape memory alloys (SMA’s), equiatomic RuNb and RuTa alloys demonstrate both shape memory effect (SME) and MT temperatures above 800°C. Equiatomic compounds undergo two successive martensitic transformations, β (B2) → β’ (tetragonal) → β’’ (monoclinic), whereas out of stoechiometry alloys exhibit a single transition from cubic to tetragonal. In the case of two successive martensitic transformations, we expect to have a finer microstructure of the second martensite because it is supposed to develop inside the smallest twin elements of the former one. In equiatomic Ru-based alloys, if the first martensitic transformation is “normal”, the second one gives different unexpected microstructures with, for instance, twins with a thickness which is larger than the smallest spacing between twin variants of the first martensite. In fact, the reason for this unexpected hierarchy of the twins size is that the second martensitic transformation takes place in special conditions: geometrically, elastically and crystallographically constrained.

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