Simulation of the Superelastic Response of SMA Orthodontic Wires

1998 ◽  
Vol 120 (5) ◽  
pp. 676-685 ◽  
Author(s):  
D. Raboud
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Mechanical Response ◽  
Numerical Solutions ◽  
Initial Value ◽  
Orthodontic Wires ◽  
Wide Range ◽  
Superelastic Behavior ◽  
Low Modulus ◽  
Experimental Works

Shape-memory alloys have properties that make them well suited to a variety of applications. One application for which their unique combination of properties (large elastic range, low modulus of elasticity, ability to deliver nearly constant forces over a wide range of deformations) seems ideally suited is for orthodontic retraction appliances where these properties are very desirable. The mechanical response of shape-memory alloys is modeled by a simple constitutive model that captures the essential superelastic behavior of the shape-memory wires. An initial value approach that iteratively converges to the appropriate boundary conditions is utilized to deliver numerical solutions. Qualitative agreement is shown with previous experimental works. The possible benefits of using such wires in an orthodontic retraction appliance are then investigated.

Implementation of Shape Memory Alloys as Active Elements in Injuries Recuperative Equipment

2014 ◽  
Vol 657 ◽  
pp. 392-396
Author(s):  
Adela Ursanu Dragoş ◽  
Sergiu Stanciu ◽  
Nicanor Cimpoeşu ◽  
Mihai Dumitru ◽  
Ciprian Paraschiv
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Spinal Cord Injuries ◽  
Good Alternative ◽  
Careful Consideration ◽  
Damping Capacity ◽  
Loss Of Function ◽  
User Friendliness ◽  
Wide Range ◽  
Constructive Models

Entire or partial loss of function in the shoulder, elbow or wrist represent an increasingly common ailment connected to a wide range of injuries or other conditions including sports, occupational, spinal cord injuries or strokes. A general treatment of these problems relies on physiotherapy procedures. An increasing number of metallic materials are continuously being developed to expect the requirements for different engineering applications including biomedical field. Few constructive models that can involve intelligent materials are analyzed to establish the advantages in usage of shape memory elements mechanical implementation. The shape memory effect, superelasticity and damping capacity are unique characteristics at metallic alloys which demand careful consideration in both design and manufacturing processes. The actual rehabilitation systems can be improved using smart elements in motorized equipments like robotic systems. Shape memory alloys, especially NiTi (nitinol), represent a very good alternative for actuation in equipments with moving dispositive based on very good actuation properties, low mass, small size, safety and user friendliness. In this article the actuation and the force characteristics were analyzed to investigate a relationship between the bending angle and the actuation real value.

scholarly journals An SMA Passive Ankle Foot Orthosis: Design, Modeling, and Experimental Evaluation

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Liberty Deberg ◽  
Masood Taheri Andani ◽  
Milad Hosseinipour ◽  
Mohammad Elahinia
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Motion Analysis ◽  
Experimental Evaluation ◽  
Mechanical Systems ◽  
Drop Foot ◽  
Ankle Foot Orthosis ◽  
New Device ◽  
Superelastic Behavior ◽  
Foot Orthosis

Shape memory alloys (SMAs) provide compact and effective actuation for a variety of mechanical systems. In this work, the distinguished superelastic behavior of these materials is utilized to develop a passive ankle foot orthosis to address the drop foot disability. Design, modeling, and experimental evaluation of an SMA orthosis employed in an ankle foot orthosis (AFO) are presented in this paper. To evaluate the improvements achieved with this new device, a prototype is fabricated and motion analysis is performed on a drop foot patient. Results are presented to demonstrate the performance of the proposed orthosis.

Superelastic behavior modeling in shape memory alloys

2003 ◽  
Vol 112 ◽  
pp. 205-208 ◽  
Author(s):  
S. Arbab Chirani ◽  
D. Aleong ◽  
C. Dumont ◽  
D. McDowell ◽  
E. Patoor
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Behavior Modeling ◽  
Superelastic Behavior

Influence of incorporated nanoparticles on superelastic behavior of shape memory alloys

2020 ◽  
Vol 776 ◽  
pp. 139025
Author(s):  
Victor A. L'vov ◽  
Anna Kosogor ◽  
Serafima I. Palamarchuk ◽  
Gregory Gerstein ◽  
Hans J. Maier
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Superelastic Behavior

Micro pulling down growth of very thin shape memory alloys single crystals

2017 ◽  
Vol 10 (01) ◽  
pp. 1740003 ◽  
Author(s):  
I. López-Ferreño ◽  
J. San Juan ◽  
T. Breczewski ◽  
G. A. López ◽  
M. L. Nó
Keyword(s):  
Mechanical Properties ◽  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Single Crystals ◽  
Functional Materials ◽  
Small Scale ◽  
Cylindrical Shape ◽  
Minimum Diameter ◽  
Wide Range

Shape memory alloys (SMAs) have attracted much attention in the last decades due to their thermo-mechanical properties such as superelasticity and shape memory effect. Among the different families of SMAs, Cu–Al–Ni alloys exhibit these properties in a wide range of temperatures including the temperature range of 100–200[Formula: see text]C, where there is a technological demand of these functional materials, and exhibit excellent behavior at small scale making them more competitive for applications in Micro Electro-Mechanical Systems (MEMS). However, polycrystalline alloys of Cu-based SMAs are very brittle so that they show their best thermo-mechanical properties in single-crystal state. Nowadays, conventional Bridgman and Czochralski methods are being applied to elaborate single-crystal rods up to a minimum diameter of 1[Formula: see text]mm, but no works have been reported for smaller diameters. With the aim of synthesizing very thin single-crystals, the Micro-Pulling Down ([Formula: see text]-PD) technique has been applied, for which the capillarity and surface tension between crucible and the melt play a critical role. The [Formula: see text]-PD method has been successfully applied to elaborate several cylindrical shape thin single-crystals down to 200[Formula: see text][Formula: see text]m in diameter. Finally, the martensitic transformation, which is responsible for the shape memory properties of these alloys, has been characterized for different single-crystals. The experimental results evidence the good quality of the grown single-crystals.

scholarly journals Finite Element Studies of Triple Actuation of Shape Memory Alloy Wires for Surgical Tools

2018 ◽  
Author(s):  
Bardia Konh
Keyword(s):  
Shape Memory ◽  
Artificial Heart ◽  
Heart Valves ◽  
Engineering Systems ◽  
Design And Development ◽  
Orthodontic Wires ◽  
Recoverable Strain ◽  
Artificial Heart Valves ◽  
Innovative Products ◽  
Superelastic Behavior

Since the early discovery in 1951 [1], shape memory alloys (SMAs) have been used in design and development of several innovative engineering systems. SMAs’ unique characteristics have introduced unconventional alternatives in design and development of advanced devices. SMA’s field of applications has covered many areas from aerospace to auto industries, and medical devices [2]. During the past couple of decades, scientists have suggested material models to predict the SMA’s shape memory effect (SME) and its superelastic behavior. The superelastic characteristic of SMAs (its capability to exhibit a large recoverable strain) has been widely used to develop innovative products including biomedical implants such as stents, artificial heart valves, orthodontic wires, frames of indestructible spectacles, etc. However, its actuation capabilities, known as SME, hasn’t been thoroughly expanded. The number of products privileging from SMA’s SME behavior has been very limited. The reason relies on the SMA’s complex material properties that depend on the stress, strain and temperature at every stage of actuation as well as the material’s processing and the thermomechanical loading history.

Mechanical Deformation of Field-Coupled Materials

2002 ◽  
Author(s):  
Pavel M. Chaplya ◽  
Geoffrey P. McKnight ◽  
Gregory P. Carman
Keyword(s):  
Shape Memory ◽  
Smart Materials ◽  
Residual Strain ◽  
Applied Load ◽  
Mechanical Response ◽  
Volume Fraction ◽  
Mechanical Deformation ◽  
Passive Damping ◽  
Wide Range ◽  
Internal States

This article describes remarkable similarities in the nonlinear mechanical response of different active/smart materials despite fundamental differences in the underlying mechanisms associated with each material. Active/smart materials (i.e., piezoelectric (PZT-5H), magnetostrictive (Terfenol-D), and shape memory alloys (NiTi)) exhibit strong non-linear mechanical behavior produced by changing non-mechanical internal states such as polarization, magnetization, and phase/twin configuration. In active/smart materials the initial deformation proceeds linearly followed by a jump in strain associated with the transformation of an internal non-mechanical state. After the transformation, the mechanical response returns to linear elastic. Upon unloading, a residual strain is observed which can be recovered with the application of a corresponding external field (i.e., electric, magnetic, or thermal). Due to coupling between applied fields and non-mechanical internal states, mechanical deformation is also a function of applied external fields. At a critical applied field, the residual strain is eliminated, providing repeatable cyclic characteristics that can be used in passive damping applications. Even though different intrinsic processes (i.e., polarization, magnetization, and phase/twin variant composition) govern the deformation of each material, their macroscopic behavior is explained using a unified volume fraction concept. That is, the deformation of piezoelectric material is described in terms of the volume fraction of ferroelectric domains with polarization parallel or orthogonal to the applied load; the deformation of magnetostrictive materials is described in terms of the volume fraction of magnetic domains with magnetization parallel or orthogonal to the applied load; and the deformation of shape memory material is described in terms of the volume fraction of twin variants that are oriented favorably to the applied load. Although the qualitative behavior of each material is similar, the average magnitude of stress required to induce non-linearity varies from ~10 MPa for Terfenol-D to ~65 MPa for PZT-5H to ~300 MPa for NiTi shape memory alloy. It is hypothesized that a composite material made of these materials connected in series would exhibit passive damping over a wide range of applied stress.

Iron-based superelastic alloys with near-constant critical stress temperature dependence

Science ◽  
2020 ◽  
Vol 369 (6505) ◽  
pp. 855-858 ◽  
Author(s):  
Ji Xia ◽  
Yuki Noguchi ◽  
Xiao Xu ◽  
Takumi Odaira ◽  
Yuta Kimura ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Temperature Dependence ◽  
Critical Stress ◽  
Outer Space ◽  
Alloy System ◽  
Large Temperature ◽  
Superelastic Behavior ◽  
Iron Based ◽  
Metal Shape

Shape memory alloys recover their original shape after deformation, making them useful for a variety of specialized applications. Superelastic behavior begins at the critical stress, which tends to increase with increasing temperature for metal shape memory alloys. Temperature dependence is a common feature that often restricts the use of metal shape memory alloys in applications. We discovered an iron-based superelastic alloy system in which the critical stress can be optimized. Our Fe-Mn-Al-Cr-Ni alloys have a controllable temperature dependence that goes from positive to negative, depending on the chromium content. This phenomenon includes a temperature-invariant stress dependence. This behavior is highly desirable for a range of outer space–based and other applications that involve large temperature fluctuations.

Cast NiTi Shape-Memory Alloys

2004 ◽  
Vol 855 ◽  
Author(s):  
Alicia M. Ortega ◽  
Carl P. Frick ◽  
Jeffrey Tyber ◽  
Ken Gall ◽  
Hans J. Maier
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Orientation ◽  
Mechanical Response ◽  
Complex Geometry ◽  
Low Cost ◽  
Orientation Distribution ◽  
Scanning Calorimetry ◽  
Cast Material ◽  
Niti Shape Memory Alloys

ABSTRACTThe purpose of this study is to investigate the structure and properties of polycrystalline NiTi in its cast form. Although it is commonly stated in the literature that cast NiTi has poor shape-memory behavior, this study demonstrates that with appropriate nano/micro structural design, cast NiTi possesses excellent shape-memory properties. Cast NiTi shape-memory alloys may give rise to a new palette of low-cost, complex-geometry components. Results from two different nominal compositions of cast NiTi are presented: 50.1 at.%Ni and 50.9 at.%Ni. The cast NiTi showed a spatial variance in grain size and a random grain orientation distribution throughout the cast material. However, small variances in the thermo-mechanical response of the cast material resulted. Transformation temperatures were slightly influenced by the radial location from which the material was extracted from the casting, showing a change in Differential Scanning Calorimetry peak diffuseness as well as a change in transformation sequence for the 50.9 at.%Ni material. Mildly aged 50.9 at.%Ni material was capable of full shape-memory strain recovery after being strained to 5% under compression, while the 50.1 at.%Ni demonstrated residual plastic strains of around 1.5%. The isotropic and symmetric response under tensile and compressive loading is a result of the measured random grain orientation distribution. The favorable recovery properties in the cast material are primarily attributed to the presence of nanometer scale precipitates, which inhibit dislocation motion and favor the martensitic transformation.

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