Feedback Linearization of Hysteretic Thermoelastic Dynamics of Shape Memory Alloy Actuators with Phase Transformations

2008 ◽  
Vol 47-50 ◽  
pp. 69-72 ◽  
Author(s):  
Lin Xiang Wang ◽  
Rong Liu ◽  
Roderick Melnik
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Feedback Linearization ◽  
Landau Theory ◽  
Nonlinear Feedback ◽  
Differential Model ◽  
Mechanical Coupling ◽  
First Order ◽  
First Order Phase ◽  
Material Temperature

In the current paper, a macroscopic differential model for the hysteretic dynamics in shape memory alloy actuators is constructed by using the modified Landau theory of the first order phase transformation. An intrinsic thermo-mechanical coupling is achieved by constructing the free energy as a function depends on both mechanical deformation and the material temperature. Both shape memory and pseudoelastic effects are modeled. The hysteretic dynamics is linearized by introducing another hysteresis loop via nonlinear feedback strategy, which cancels the original one.

Hysteretic Dynamics of Ferroelectric Materials Under Electro-Mechanical Loadings

2008 ◽  
Author(s):  
Linxiang Wang
Keyword(s):  
Electric Field ◽  
Phase Transformations ◽  
Landau Theory ◽  
Hysteresis Loops ◽  
Ferroelectric Materials ◽  
Differential Model ◽  
Mechanical Coupling ◽  
First Order ◽  
Bias Stress ◽  
First Order Phase

In the current paper, the hysteretic dynamics of ferroelectric materials under combined electro-mechanical loadings is investigated using a macroscopic differential model. The model is constructed on the basis of the Landau theory of the first order phase transformations. Hysteresis loops in the electric field and the butterfly-shaped behaviors in the electro-mechanical coupling are modeled as a consequence of polarizations and orientation switchings, together with nonlinear electro-mechanical coupling effects. The effects of bias stress on the orientation switchings are investigated numerically. Comparison of the model results with its experimental counterparts is presented, capability of the model is approved.

Macroscopic Differential Model for Hysteresis and Butterfly-Shaped Behavior in Ferroelectric Materials

2008 ◽  
Vol 47-50 ◽  
pp. 65-68 ◽  
Author(s):  
Lin Xiang Wang ◽  
Ying Chen ◽  
Wen Li Zhao
Keyword(s):  
Landau Theory ◽  
Hysteresis Loops ◽  
Ferroelectric Materials ◽  
Free Energy Function ◽  
System State ◽  
Differential Model ◽  
First Order ◽  
State Switching ◽  
Transformation Hysteresis ◽  
First Order Phase

In the current paper, a macroscopic differential model is constructed on the basis of the Landau theory of the first order phase transformation. Hysteresis loops and butterfly-shaped behaviors are modeled as a consequence of polarizations and orientation switchings. A non-convex free energy function is constructed to characterize different polarization orientations in the materials. Polarizations and orientation switchings are modeled by formulating the system state switching from one equilibrium state to another, as differential equations. The hysteresis loops and butterfly-shaped behaviors are successfully modeled. Comparison of the model results with the experimental counterpart is also presented.

Rate-Dependent Damping Capacity of NiTi Shape Memory Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 37-42 ◽  
Author(s):  
Yong Jun He ◽  
Qing Ping Sun
Keyword(s):  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Strain Curve ◽  
Tensile Loading ◽  
Niti Shape Memory Alloy ◽  
Damping Capacity ◽  
Environmental Condition ◽  
Mechanical Coupling ◽  
Rate Dependent

High damping capacity is one of the prominent properties of NiTi shape memory alloy (SMA), having applications in many engineering devices to reduce unwanted vibrations. Recent experiments demonstrated that, the hysteresis loop of the stress-strain curve of a NiTi strip/wire under a tensile loading-unloading cycle changed non-monotonically with the loading rate, i.e., a maximum damping capacity was obtained at an intermediate strain rate (ε.critical). This rate dependence is due to the coupling between the temperature dependence of material’s transformation stresses, latent-heat release/absorption in the forward/reverse phase transition and the associated heat exchange between the specimen and the environment. In this paper, a simple analytical model was developed to quantify these thermo-mechanical coupling effects on the damping capacity of the NiTi strips/wires under the tensile loading-unloading cycle. We found that, besides the material thermal/mechanical properties and specimen geometry, environmental condition also affects the damping capacity; and the critical strain rate ε.criticalfor achieving a maximum damping capacity can be changed by varying the environmental condition. The theoretical predictions agree quantitatively with the experiments.

A phenomenological model for thermally-induced hysteresis in polycrystalline shape memory alloys with internal loops

2021 ◽  
pp. 1045389X2110482
Author(s):  
Yuxiang Han ◽  
Haoyuan Du ◽  
Linxiang Wang ◽  
Roderick Melnik
Keyword(s):  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Phenomenological Model ◽  
Landau Theory ◽  
Thermally Induced ◽  
First Order ◽  
Proposed Model ◽  
Crystal Model ◽  
Hysteretic Response

In the current study, a 1-D phenomenological model is constructed to capture the temperature-induced hysteretic response in polycrystalline shape memory alloys (SMAs). The martensitic and austenitic transformations are regarded as the first-order transitions. A differential single-crystal model is formulated on the basis of Landau theory. It is assumed that the transformation temperatures follow the normal distribution among the grains due to the anisotropic stress field developed in the material. The polycrystalline hysteretic response is expressed as the integration of single-crystal responses. Besides, the prediction strategy for incomplete transitions is presented, and the first-order reversal curves are obtained via density reassignment. The proposed model is numerically implemented for validation. Comparisons between the modeling results and the experimental ones demonstrate the capability of the proposed model in addressing the hysteresis in thermally-induced phase transformations.

scholarly journals Buckling Strengths of Composite Plate Using Shape Memory Alloy under In-Plane Shear

2021 ◽  
Vol 12 (2) ◽  
pp. 1729-1738
Author(s):  
Yatendra Saraswat, Et. al.
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Plate ◽  
Shear Deformation Theory ◽  
Shear Load ◽  
Plane Shear ◽  
Alloy Plate ◽  
First Order ◽  
Circular Cutout ◽  
Ansys Workbench

In this article, we analyze the strength and buckling response in the plane shear load fixed at the corner of the composite plate. The fem is formulated is done on the basis of first-order shear deformation theory and assumptions of von Karman. The Newton-Raphson technique is considered to analyze the non-linearity algebraic equation. The effect of shape memory alloy in shear load and buckling response is discussed. In this study we analyze the two cases in the first simple carbon/epoxy plate is analyze and then we use the shape memory wire embedded in the plate which is about 1% of the volume of the plate and studies the buckling response effect on the plate. In the second case we use Shape Memory Alloy plate and loading but a circular cutout at the middle of the plate this case we analyze for both with the use of shape memory alloy and without the use of shape memory. It is observed that the shape memory alloy increases the strength of the plate in both cases. The whole simulations are done using Ansys workbench software v 2020R2.

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