Journal ArticleDOI
One-Dimensional Thermomechanical Constitutive Relations for Shape Memory Materials
Chen Liang,Craig A. Rogers +1 more
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TLDR
In this article, a complete, unified, one-dimensional constitutive model of shape memory materials is developed and presented in the form of a thermomechanical model for shape memory alloys.Abstract:
The use of the thermoelastic martensitic transformation and its reverse transformation has recently been proposed and demonstrated for several active control ap plications. However, the present constitutive models have lacked several important funda mental concepts that are essential for many of the proposed intelligent material system ap plications such as shape memory hybrid composites.A complete, unified, one-dimensional constitutive model of shape memory materials is developed and presented in this paper. The thermomechanical model formulation herein will investigate important material characteristics involved with the internal phase transformation of shape memory alloys. These characteristics include energy dissipation in the material that governs the damping behavior, stress-strain-temperature relations for pseudoelasticity, and the shape memory effect. Some numerical examples using the model are also presented.read more
Citations
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Journal ArticleDOI
A three-dimensional constitutive model for shape memory alloy
TL;DR: In this article, a new three-dimensional phase transformation equation was developed based on the results of a differential scanning calorimetry (DSC) test, which predicts the phase transformation behaviors of SMA.
Journal ArticleDOI
Combining thermodynamic principles with Preisach models for superelastic shape memory alloy wires
TL;DR: In this article, a Gibbs potential-based formulation is used to separate the dissipative response and the elastic response of shape memory alloys, and then a Preisach model is used for dissipative part of the response.
Journal ArticleDOI
Multi-dimensional superelastic behavior of shape memory alloys via nonlinear finite element method
TL;DR: In this article, a numerical multi-dimensional constitutive model is formulated by thermomechanics incorporated with the "yield" surface of shape memory alloys, and the phase flow direction can be decided by using the yield stresses of a particular SMA in uni-axial tension and compression.
Journal ArticleDOI
Backstepping Control of a Shape Memory Alloy Actuated Robotic Arm
TL;DR: In this paper, a nonlinear controller designed to stabilize a single-degree-of-freedom rotary shape memory alloy (SMA) actuated robotic arm is presented, which is a bias-type robotic arm.
DissertationDOI
Fast, accurate force and position control of shape memory alloy actuators
Abstract: Shape memory alloy (SMA) actuators have great potential in niche applications where space, weight, cost and noise are crucial factors. Despite many of the advantages, they remain mostly as experimental actuators due to their perceived slow response speed, low accuracy and controllability. Especially in situations where there is a moving link or an external payload, the problem of limit cycles has been pursued by various researchers but never fully solved. In this thesis, practical, effective control systems are applied to achieve fast and accurate force and position control of SMA wire actuators. Investigations into very high-frequency responses from SMAs are initially explored, which produce surprising results of audio frequency responses. This discovery has led us towards using high-bandwidth control systems as a possible method of eliminating limit cycles. Frequency response analysis of SMA actuators have also been carried out. Based on the results, linear force models for single SMA wires as well as for an actuator comprising of an antagonistic pair of SMA wires have been developed. A position model for an antagonistic SMA-actuated robotic joint has also been developed based on the force models. These models are integral in the design, tuning and simulation of various control systems for SMA actuators. High-bandwidth PID control has been employed in the force control of single SMA wire actuators. More importantly, it forms the main control component in the differential force control architecture for antagonistic SMA actuators. Other components are the anti-slack mechanism, the rapid-heating mechanism and the anti-overload mechanism. The closed loop response is fast and accurate, even in the presence of external motion disturbances. There is generally no limit cycles in the actuator’s differential force output; and the performance is unaffected by large load inertias. This thesis also presents a two-loop architecture for position control, in which a position feedback loop is added to the force control architecture. Experimental results demonstrate highly accurate position control with no limit iii cycles in the presence of external loads. The accomplishments reported in this thesis represent a significant development in making SMA actuators faster, more accurate and effective. It is aspired that the results and control methods in this work can be utilised in enabling practical SMA technologies for robotic and commercial applications.
References
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Journal ArticleDOI
Thermoelasticity, pseudoelasticity and the memory effects associated with martensitic transformations
TL;DR: In this paper, the pertinent thermodynamic relations, nucleation and growth and the influence of stress are considered and applied to thermoelasticity and the memory effects, and the effects of stress on memory are investigated.
Journal ArticleDOI
A thermomechanical description of materials with internal variables in the process of phase transitions
K. Tanaka,S. Nagaki +1 more
TL;DR: In this article, a model for thermoplastic materials in the process of solid-solid phase transition is presented, where the material is characterized by three different internal state variables: two internal variables which specify the crystallographic structural change during the plastic deformation, and a set of scalar internal variables describing the extent of phase transition.
Journal ArticleDOI
Some Applications of Shape-Memory Alloys
TL;DR: In this article, the shape memory effect and other interesting properties of shape memory alloys are discussed after a brief discussion of the nature of the shape-memory effect and some interesting properties.