scholarly journals Thermomechanical Modeling of Shape Memory Alloys with Rate Dependency on the Pseudoelastic Behavior

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Jin-Ho Roh
Keyword(s):  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory ◽  
Loading Rate ◽  
Strain Rates ◽  
Rate Dependency ◽  
Strain Rate Dependency ◽  
Improved Model ◽  
Thermomechanical Modeling ◽  
Pseudoelastic Behavior

The loading-rate dependency on the pseudoelastic behaviors of shape memory alloy (SMA) wires is experimentally and numerically investigated. The results are analyzed to estimate the parameters for a thermomechanical constitutive model of SMA wire with strain-rate dependency of the hysteresis behavior. An analytical model of SMAs is developed by using nonconstant parameters during various strain rates. Numerical simulations are performed to demonstrate the accuracy of the improved model.

scholarly journals Experimental and Numerical Analysis of the Mechanical Properties of a Pretreated Shape Memory Alloy Wire in a Self-Centering Steel Brace

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 80
Author(s):  
Bo Zhang ◽  
Sizhi Zeng ◽  
Fenghua Tang ◽  
Shujun Hu ◽  
Qiang Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Energy Dissipation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Loading Rate ◽  
Effective Elastic Modulus ◽  
Maximum Energy ◽  
Numerical Results ◽  
Energy Dissipation Capacity

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires may not be accurately obtained. In this paper, the cyclic tensile tests of a kind of SMA wire with a 1 mm diameter and special element composition were tested under multi-working conditions, which were pretreated by first tensioning to the 0.06 strain amplitude for 40 cycles, so the mechanical properties of the pretreated SMA wires can be simulated in detail. The accuracy of the numerical results with the improved model of Graesser’s theory was verified by a comparison to the experimental results. The experimental results show that the number of cycles has no significant effect on the mechanical properties of SMA wires after a certain number of cyclic tensile training. With the loading rate increasing, the pinch effect of the hysteresis curves will be enlarged, while the effective elastic modulus and slope of the transformation stresses in the process of loading and unloading are also increased, and the maximum energy dissipation capacity of the SMA wires appears at a loading rate of 0.675 mm/s. Moreover, with the initial strain increasing, the slope of the transformation stresses in the process of loading is increased, while the effective elastic modulus and slope of the transformation stresses in the process of unloading are decreased, and the maximum energy dissipation capacity appears at the initial strain of 0.0075. In addition, a good agreement between the test and numerical results is obtained by comparing with the hysteresis curves and energy dissipation values, so the numerical model is useful to predict the stress–strain relations at different stages. The test and numerical results will also provide a basis for the design of corresponding self-centering steel dampers.

A constitutive model for Fe-based shape memory alloy considering martensitic transformation and plastic sliding coupling: Application to a finite element structural analysis

2012 ◽  
Vol 23 (10) ◽  
pp. 1143-1160 ◽  
Author(s):  
Walid Khalil ◽  
Alain Mikolajczak ◽  
Céline Bouby ◽  
Tarak Ben Zineb
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Structural Analysis ◽  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Shape Memory ◽  
Internal Variables ◽  
Thermomechanical Loading ◽  
Proposed Model ◽  
Numerical Tool

In this article, we propose a finite element numerical tool adapted to a Fe-based shape memory alloy structural analysis, based on a developed constitutive model that describes the effect of phase transformation, plastic sliding, and their interactions on the thermomechanical behavior. This model was derived from an assumed expression of the Gibbs free energy taking into account nonlinear interaction quantities related to inter- and intragranular incompatibilities as well as mechanical and chemical quantities. Two scalar internal variables were considered to describe the phase transformation and plastic sliding effects. The hysteretic and specific behavior patterns of Fe-based shape memory alloy during reverse transformation were studied by assuming a dissipation expression. The proposed model effectively describes the complex thermomechanical loading paths. The numerical tool derived from the implicit resolution of the nonlinear partial derivative constitutive equations was implemented into the Abaqus® finite element code via the User MATerial (UMAT) subroutine. After tests to verify the model for homogeneous and heterogeneous thermomechanical loadings, an example of Fe-based shape memory alloy application was studied, which corresponds to a tightening system made up of fishplates for crane rails. The results we obtained were compared to experimental ones.

Complex transformation field created by geometrical gradient design of NiTi shape memory alloy

2017 ◽  
Vol 10 (01) ◽  
pp. 1740011 ◽  
Author(s):  
Reza Bakhtiari ◽  
Bashir S. Shariat ◽  
Fakhrodin Motazedian ◽  
Zhigang Wu ◽  
Junsong Zhang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Deformation Behavior ◽  
Stress Gradient ◽  
Tensile Loading ◽  
Niti Shape Memory Alloy ◽  
Mechanical Behaviors ◽  
Modeling Framework ◽  
Complex Transformation ◽  
Pseudoelastic Behavior

Owing to geometrical non-uniformity, geometrically graded shape memory alloy (SMA) structures by design have the ability to exhibit different and novel thermal and mechanical behaviors compared to geometrically uniform conventional SMAs. This paper reports a study of the pseudoelastic behavior of geometrically graded NiTi plates. This geometrical gradient creates partial stress gradient over stress-induced martensitic transformation, providing enlarged stress controlling interval for shape memory actuation. Finite element modeling framework has been established to predict the deformation behavior of such structures in tensile loading cycles, which was validated by experiments. The modeling results show that the transformation mostly propagates along the gradient direction as the loading level increases.

The Concept of Physical Metric in the Thermomechanical Modeling of Phase Transformations With Emphasis on Shape Memory Alloy Materials

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Vassilis P. Panoskaltsis ◽  
Lazaros C. Polymenakos ◽  
Dimitris Soldatos
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Phase Transformations ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Material Model ◽  
Internal Variable ◽  
Theoretical Interest ◽  
Numerical Examples ◽  
Thermomechanical Modeling

In this work we derive a new version of generalized plasticity, suitable to describe phase transformations. In particular, we present a general multi surface formulation of the theory which is capable of describing the multiple and interacting loading mechanisms, which occur during phase transformations. The formulation relies crucially on the consideration of the intrinsic material (“physical”) metric as a primary internal variable and does not invoke any decomposition of the kinematical quantities into elastic and inelastic (transformation induced) parts. The new theory, besides its theoretical interest, is also important for application purposes such as the description and the prediction of the response of shape memory alloy materials. This is shown in the simplest possible setting by the introduction of a material model. The ability of the model in simulating several patterns of the experimentally observed behavior of these materials such as the pseudoelastic phenomenon and the shape memory effect is assessed by representative numerical examples.

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