Dynamic Thermomechanical Modeling of a Wet Shape Memory Alloy Actuator

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Joel D. Ertel ◽  
Stephen A. Mascaro
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Temperature Change ◽  
Cold Water ◽  
Thermomechanical Model ◽  
Martensite Fraction ◽  
Mechanical Models ◽  
Strain Martensite ◽  
The Wire ◽  
Thermomechanical Modeling

This paper presents combined thermal and mechanical models of a wet shape memory alloy (SMA) wire actuator. The actuator consists of a SMA wire suspended concentrically in a compliant tube. Actuation occurs as hot and cold water that are alternately pumped through the tube to contract and extend the wire, respectively. The thermomechanical model presented in this paper accounts for the nonuniform temperature change of the SMA wire due to alternating the temperature of the flow along the wire. The thermal portion of the model consists of analysis of the heat transfer between the fluid and the SMA wire. Heat loss to the environment and the temperature change of the fluid through the actuator are taken into account. Based on this analysis, the temperature of the wire at segments along its length can be determined as a function of time. The mechanical portion of the model approximates the strain-martensite fraction and martensite fraction-temperature relationships. By combining the thermal and mechanical models, the displacement of the wire can be determined as a function of time. The combined thermomechanical model will be useful for predicting the performance of wet SMA actuators in a variety of applications.

Thermomechanical Modeling of a Wet Shape Memory Alloy Actuator

2006 ◽  
Author(s):  
Joel Ertel ◽  
Stephen Mascaro
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Temperature Change ◽  
Cold Water ◽  
Uniform Temperature ◽  
Thermomechanical Model ◽  
Martensite Fraction ◽  
Mechanical Models ◽  
Sma Actuator ◽  
The Wire

This paper presents combined thermal and mechanical models of a wet shape memory alloy (SMA) wire actuator. The actuator consists of a SMA wire suspended concentrically in a compliant tube. Actuation occurs as hot and cold water are alternately pumped through the tube to contract and extend the wire, respectively. Although other constitutive models of the behavior of SMA's exist, they generally assume uniform temperature change throughout the SMA actuator. The thermomechanical model presented in this paper accounts for the non-uniform temperature change of the SMA wire due to alternating the temperature of the flow along the wire. The thermal model consists of analysis of the heat transfer between the fluid and the SMA wire. Heat loss to the environment and the temperature change of the fluid through the actuator are taken into account. Based on this analysis the temperature of the wire at segments along its length can be determined as a function of time. The mechanical model approximates the strain-martensite fraction and martensite fraction-temperature relationships. By combining the thermal and mechanical models the strain of the wire can be determined as a function of time. The combined thermomechanical model will be used to model applications in which a wet SMA actuator is desired.

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.

Design Framework for Multi-Section Shape Memory Alloy Axial Actuators Considering Material and Geometric Uncertainties

2020 ◽  
Author(s):  
Weilin Guan ◽  
Edwin A. Peraza Hernandez
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Energy ◽  
High Energy Density ◽  
Design Framework ◽  
Efficient Design ◽  
Cross Sectional ◽  
Geometric Uncertainties ◽  
In Series ◽  
The Wire

Abstract Shape memory alloys are metallic materials with the capability of performing as high energy density actuators driven by temperature control. This paper presents a design framework for shape memory alloy (SMA) axial actuators composed of multiple wire sections connected in series. The various wire sections forming the actuators can have distinct cross-sectional areas and lengths, which can be modulated to adjust the overall thermomechanical response of the actuator. The design framework aims to find the optimal cross-sectional areas and lengths of the wire sections forming the axial actuator such that its displacement vs. temperature actuation path approximates a target path. Constraints on the length-to-diameter aspect ratio and stress of the wire sections are incorporated. A reduced-order numerical model for the multi-section SMA actuators that allows for efficient design evaluations is derived and implemented. An approach to incorporate uncertainty in the geometry and material parameters of the actuators within the design framework is implemented to allow for the determination of robust actuator designs. A representative application example of the design framework is provided illustrating the benefits of using multiple wire sections in axial actuators to modulate their overall response and approximate a target displacement vs. temperature actuation path.

Backstepping Control of a Shape Memory Alloy Actuated Robotic Arm

2005 ◽  
Vol 11 (3) ◽  
pp. 407-429 ◽  
Author(s):  
M. Elahinia ◽  
J. Koo ◽  
M. Ahmadian ◽  
C. Woolsey
Keyword(s):  
Heat Transfer ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sliding Mode ◽  
Angular Position ◽  
Robotic Arm ◽  
Transfer Model ◽  
Nonlinear Controller ◽  
Model Based ◽  
The Wire

This paper investigates a nonlinear controller designed to stabilize a single-degree-of-freedom rotary shape memory alloy (SMA) actuated robotic arm. To this end, a bias-type robotic arm was built using 150 pm Flexinol SMA wire. This robot is designed to lift and position lightweight objects. Upon complete phase transformation, the SMA wire actuates the robot to rotate up to 1350. A linear spring is used to extend the wire to its original length because the SMA wire can only apply force in one direction. To measure the angular position of the robotic arm, an optical rotary encoder was used. To stabilize the robot, a model-based controller was developed. The controller incorporates the SMA actuated robot model with nonlinear control techniques. The model consists of three parts: the dynamics/kinematics of the arm, the thermoruechanical behavior of SMA wire, and the heat transfer model of the wire. The model-based backstepping controller determines the applied voltage to the SMA wire for positioning the arm at the desired angle by first calculating the wire's stress to stabilize the arm. The voltage to the SMA wire is then calculated based on the desired stress and the SMA's thermomechanical and heat transfer models. A series of simulations were performed to investigate stabilizing performance of the controller. Moreover, other issues such as robustness of the control design was evaluated. The results show that the control algorithms is able to globally and asymptotically stabilize the robot. The results further indicate that the sliding mode control has better robustness properties.

Study on Superelasticity and Microstructure of TiNiV Shape Memory Alloy by Medium-Temperature Treatment

2011 ◽  
Vol 418-420 ◽  
pp. 222-227
Author(s):  
Zhi Jian Zhang ◽  
Nai Chao Si ◽  
Guang Lei Liu ◽  
Song Hai Si
Keyword(s):  
Shape Memory Alloy ◽  
Tensile Test ◽  
Shape Memory ◽  
Room Temperature ◽  
Temperature Treatment ◽  
Shape Memory Alloy Wire ◽  
Medium Temperature ◽  
Alloy Wire ◽  
The Wire ◽  
Cold Pressed

The TiNiV shape memory alloy wire that was cold pressed under 9Mpa at the room temperature had good superelasticity. On this basis, a tensile test was made after a series of medium-temperature treatment. Then the effect of superelasticity and microstructure of TiNiV shape memory alloy by medium-temperature treatment were studied. The results indicate that the experimental wires assume thorough non-linear superelasticity after holding 30 min at 430°C. The superelasticity of the wire enhances firstly, then declines with the ascent of the temperature and extension of the time of the holding. A kind of potentiation phase-Ti3Ni4 precipites out of the wire under different medium-temperature treatment.

scholarly journals Multi-Response Optimization of WEDM Process Parameters for Machining of Superelastic Nitinol Shape-Memory Alloy Using a Heat-Transfer Search Algorithm

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1277 ◽  
Author(s):  
Rakesh Chaudhari ◽  
Jay J. Vora ◽  
S. S. Mani Prabu ◽  
I. A. Palani ◽  
Vivek K. Patel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Process Parameters ◽  
Discharge Process ◽  
The Wire ◽  
Pulse On Time ◽  
Wedm Process

Nitinol, a shape-memory alloy (SMA), is gaining popularity for use in various applications. Machining of these SMAs poses a challenge during conventional machining. Henceforth, in the current study, the wire-electric discharge process has been attempted to machine nickel-titanium (Ni55.8Ti) super-elastic SMA. Furthermore, to render the process viable for industry, a systematic approach comprising response surface methodology (RSM) and a heat-transfer search (HTS) algorithm has been strategized for optimization of process parameters. Pulse-on time, pulse-off time and current were considered as input process parameters, whereas material removal rate (MRR), surface roughness, and micro-hardness were considered as output responses. Residual plots were generated to check the robustness of analysis of variance (ANOVA) results and generated mathematical models. A multi-objective HTS algorithm was executed for generating 2-D and 3-D Pareto optimal points indicating the non-dominant feasible solutions. The proposed combined approach proved to be highly effective in predicting and optimizing the wire electrical discharge machining (WEDM) process parameters. Validation trials were carried out and the error between measured and predicted values was negligible. To ensure the existence of a shape-memory effect even after machining, a differential scanning calorimetry (DSC) test was carried out. The optimized parameters were found to machine the alloy appropriately with the intact shape memory effect.

Effect of Geometric Design Parameters on Contractile SMA Knitted Actuator Performance

2017 ◽  
Author(s):  
Kevin Eschen ◽  
Julianna Abel
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Load Capacity ◽  
Design Parameters ◽  
Partial Recovery ◽  
Thermal Actuation ◽  
The Wire ◽  
High Level ◽  
Actuator Design ◽  
Actuator Performance

Shape memory alloy (SMA) knitted actuators are a type of functional fabric that uses shape memory alloy wire as an active fiber within a knitted textile. Through intentional design of the SMA knitted actuator geometry, various two- and three-dimensional actuation motions, such as scrolling and contraction [1], can be accomplished. Contractile SMA knitted actuators leverage the unique thermo-mechanical properties of SMA wires by integrating them within the hierarchical knitted structure to achieve large distributed uniaxial contractions and variable stiffness behavior upon thermal actuation. During the knit manufacturing process, the SMA wire is bent into a network of interlacing adjacent loops, storing potential energy within the contractile SMA knitted actuator. Thermal actuation above the wire-specific austenite finish temperature leads to a partial recovery of the bending deformations, resulting in large distributed uniaxial contraction (15–40% actuation contraction observed) of the SMA knitted actuator. The achievable load capacity and %-actuation contraction are dependent on the geometric loop parameters of the contractile SMA knitted actuator. While exact descriptions of the geometric loop parameters exist, a reduction of the geometric complexity is advantageous for high-level contractile SMA knitted actuator design procedures. This paper defines a simple geometric measure, the non-dimensional knit density, and experimentally correlates the contractile SMA knitted actuator performance to this measure. The experimentally demonstrated dependency of relevant actuator metrics on the knit density and the wire diameter, suggests the usability of the simplified geometry definition for a high-level contractile SMA knitted actuator design.

Self-Folding Origami Using Torsion Shape Memory Alloy Wire Actuators

2014 ◽  
Author(s):  
Je-sung Koh ◽  
Sa-reum Kim ◽  
Kyu-jin Cho
Keyword(s):  
Form Factor ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Alloy Wire ◽  
Maximum Torque ◽  
Alloy Wire ◽  
Low Profile ◽  
The Wire ◽  
Linear Manner ◽  
Novel Design

Self-folding origami requires a low-profile actuator to be embedded in a sheet of paper-like planar material. Various actuation methods have been employed to actively fold such sheets. This paper presents a torsion shape-memory alloy (SMA) wire actuator embedded in patterned origami structures that actively folds the origami by twisting the SMA wire. A simple wire is aligned with the fold line, and each end is fixed to a facet. The twisting of the wire directly rotates the facets. This method has the advantage of using an easily available wire SMA and the advantage of a flat form factor similar to that of sheet SMA. Generally, SMA wire is used in a linear manner or as a spring. The torsion SMA wire presented in this paper is trained to generate torsional force when heated. The amount of rotation depends on the length of the wire; a 200-μm-diameter SMA wire 12 mm in length can induce 540° rotation. SMA wires are arranged in pairs side by side to rotate the facets in both directions. Maximum torque of 70 mNcm is generated in this antagonistic arrangement. The torsion SMA wire actuators enable a novel design for a programmable folding sheet that is easily manufactured and exhibits fast folding and unfolding.

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