Understanding the shape-memory alloys used in orthodontics.

Science.gov (United States)

Fernandes, Daniel J; Peres, Rafael V; Mendes, Alvaro M; Elias, Carlos N

2011-01-01

Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA.

Shape Memory Alloy-Based Periodic Cellular Structures, Phase I

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National Aeronautics and Space Administration — This SBIR Phase I effort will develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular structures...

Characterization and design of antagonistic shape memory alloy actuators

International Nuclear Information System (INIS)

Georges, T; Brailovski, V; Terriault, P

2012-01-01

Antagonistic shape memory actuators use opposing shape memory alloy (SMA) elements to create devices capable of producing differential motion paths and two-way mechanical work in a very efficient manner. There is no requirement for additional bias elements to ‘re-arm’ the actuators and allow repetitive actuation. The work generation potential of antagonistic shape memory actuators is determined by specific SMA element characteristics and their assembly conditions. In this study, the selected SMA wires are assembled in antagonistic configuration and characterized using a dedicated test bench to evaluate their stress–strain characteristics as a function of the number of cycles. Using these functional characteristics, a so-called ‘working envelope’ is built to assist in the design of such an actuator. Finally, the test bench is used to simulate a real application of an antagonistic actuator (case study). (paper)

Shape Memory Alloy-Based Periodic Cellular Structures, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — This SBIR Phase II effort will continue to develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular...

Vibration Control of a Flexible Rotor Using Shape Memory Alloy Wires

DEFF Research Database (Denmark)

Alves, Marco Túlio Santana; Enemark, Søren; Steffen Jr, Valdar

2015-01-01

In the present contribution, a theoretical model of a test rig containing a flexible rotor is simulated considering pseudoelastic SMA (Shape Memory Alloy) wires connected to a bearing in order to dissipate energy and consequently reduce vibration. SMAs have characteristics of shape memory...... of rotor and SMA wires are coupled. The chosen constitutive model that governs the SMA behaviour is a modified version of the model by Brinson for the one-dimensional case. Both transient and steady-state tests arenumerically simulated. The first one, a run-up test, is performed only at room temperature...

Three-Dimensional Cellular Structures Enhanced By Shape Memory Alloys

Science.gov (United States)

Nathal, Michael V.; Krause, David L.; Wilmoth, Nathan G.; Bednarcyk, Brett A.; Baker, Eric H.

2014-01-01

This research effort explored lightweight structural concepts married with advanced smart materials to achieve a wide variety of benefits in airframe and engine components. Lattice block structures were cast from an aerospace structural titanium alloy Ti-6Al-4V and a NiTi shape memory alloy (SMA), and preliminary properties have been measured. A finite element-based modeling approach that can rapidly and accurately capture the deformation response of lattice architectures was developed. The Ti-6-4 and SMA material behavior was calibrated via experimental tests of ligaments machined from the lattice. Benchmark testing of complete lattice structures verified the main aspects of the model as well as demonstrated the advantages of the lattice structure. Shape memory behavior of a sample machined from a lattice block was also demonstrated.

Development of microactuators from shape memory alloys

International Nuclear Information System (INIS)

Kohl, M.

2002-04-01

Shape memory alloys (SMAs) have the fascinating property of shape recovery, which is associated with the generation of high energy densities. Nowadays, they are already used in several very successful applications. Within the last 10 years, SMA devices have entered also the field of microsystems technology. The present report gives an overview on the current state-of-the-art. For the examples of SMA microvalves and SMA linear actuators, the microactuator development is described from the idea to the prototype in comprehensive breadth. The breadth of research and development activities on SMA microactuators presently ranges from pure scientific topics of materials research to technological problems, e.g. of micromachining, integration and contacting. Further key aspects of development are three-dimensional models for the handling of complex SMA actuator geometries and coupled simulation routines in order to take multifunctional properties into account. For actuator design, mechanical and thermal optimization criteria are introduced, whose systematic implementation allows an optimum use of the shape memory effect. Some of the presented prototypes are already competitive components. One example are normally-open SMA microvalves driven by SMA foil actuators of 20 μm thickness, which are counted among the smallest microvalves and which still are able to control pressures and flows comparable to other valve concepts. Due to their modular design they can be combined with other microfluidic components in a flexible way for realization of fluidic microsystems. Another example are SMA microgrippers, a further development of SMA linear actuators, which presently outperform other microgrippers of comparable size with respect to gripping force and stroke. (orig.)

Experimental Studies on Dynamic Vibration Absorber using Shape Memory Alloy (NiTi) Springs

International Nuclear Information System (INIS)

Kumar, V. Raj; Kumar, M. B. Bharathi Raj; Kumar, M. Senthil

2011-01-01

Shape memory alloy (SMA) springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some vibration control concepts utilizing unique characteristics of SMA's will be presented in this paper.A dynamic vibration absorber (DVA) using shape memory alloy (SMA) actuator is developed for attenuation of vibration in a cantilever beam. The design procedure of the DVA is presented. The system consists of a cantilever beam which is considered to generate the real-time vibration using shaker. A SMA spring is used with a mass attached to its end. The stiffness of the SMA spring is dynamically varied in such a way to attenuate the vibration. Both simulation and experimentation are carried out using PID controller. The experiments were carried out by interfacing the experimental setup with a computer using LabVIEW software, Data acquisition and control are implemented using a PCI data acquisition card. Standard PID controllers have been used to control the vibration of the beam. Experimental results are used to demonstrate the effectiveness of the controllers designed and the usefulness of the proposed test platform by exciting the structure at resonance. In experimental setup, an accelerometer is used to measure the vibration which is fed to computer and correspondingly the SMA spring is actuated to change its stiffness to control the vibration. The results obtained illustrate that the developed DVA using SMA actuator is very effective in reducing structural response and have great potential to be an active vibration control medium.

Properties and medical applications of shape memory alloys.

Science.gov (United States)

Tarniţă, Daniela; Tarniţă, D N; Bîzdoacă, N; Mîndrilă, I; Vasilescu, Mirela

2009-01-01

One of the most known intelligent material is nitinol, which offers many functional advantages over conventional implantable alloys. Applications of SMA to the biomedical field have been successful because of their functional qualities, enhancing both the possibility and the execution of less invasive surgeries. The biocompatibility of these alloys is one of their most important features. Different applications exploit the shape memory effect (one-way or two-way) and the super elasticity, so that they can be employed in orthopedic and cardiovascular applications, as well as in the manufacture of new surgical tools. Therefore, one can say that smart materials, especially SMA, are becoming noticeable in the biomedical field. Super elastic NiTi has become a material of strategic importance as it allows to overcome a wide range of technical and design issues relating to the miniaturization of medical devices and the increasing trend for less invasive and therefore less traumatic procedures. This paper will consider just why the main properties of shape memory alloys hold so many opportunities for medical devices and will review a selection of current applications.

Application of shape memory alloys in bolted flanged connections

International Nuclear Information System (INIS)

Zhu Shichun; Lu Xiaofeng

2009-01-01

The Shape Memory Effect (SME) and super elasticity of the Shape Memory Alloys (SMA) can make up the clamping force decreasing caused by the creep and relaxation behavior in Bolted Flanged Connections (BFC), and improve the reliability of the BFC. Advances in the research of SMA in BFC home and abroad is summarized in this paper. The application prospects of Ti-Ni-Pd, Ti-Ni-Hf, Fe-Mn-Si, Cu-Al-Ni and Ni-Al-Mn in the BFC are also discussed. It is considered that the compressive characteristics of the parent phase of SMA should be studied further for the application of SMA to BFC besides the design of sealing structure. When more basic research data is accumulated, BFC with high sealing performance for the critical engineering applications can be developed based on the comprehensive consideration of the stability and reliability of the clamping force. (authors)

Synthesis and evaluation of ageing effect on Cu–Al–Be–Mn quaternary Shape Memory Alloys

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A.G. Shivasiddaramiah

2016-09-01

Full Text Available Copper based shape memory alloy exhibits high transformation temperature and ability to differ the achieved properties through alloying additions. A quaternary Cu–Al–Be–Mn shape memory alloys of 0.2–0.4 wt% of manganese, 0.4–0.5 wt% of Beryllium and 10–14 wt% of aluminium with remaining copper, showing β-phase at higher temperature and show shape memory effect when quenching to lower temperatures, SMA's were prepared by induction melting. The objective is to study the effect of thermal ageing at different temperatures Af (above austenitic phase finish temperature and at different time on shape memory effect and transformation temperatures. The aged specimens or SMA's were studied by DSC, OM and hardness measurements. The results from this study help to find the applications in different thermal conditions.

Micromechanical modelling of shape memory alloy composites

Energy Technology Data Exchange (ETDEWEB)

Wang, Y.F.; Wang, X.M.; Yue, Z.F. [School of Mechanic, Civil Engineering and Architecture, Northwestern Polytechnical University, Xian, 710072 (China)

2004-03-01

An isothermal finite element method (FEM) model has been applied to study the behavior of two kinds of shape memory alloy (SMA) composites. For SMA-fiber reinforced normal metal composites, the FEM analysis shows that the mechanical behavior of the composites depends on the SMA volume fraction. For normal metal-fiber reinforced SMA matrix composites, the SMA phase transformation is affected by the increasing Young's modulus of the metal fiber. The phase transformation was also treated using a simple numerical analysis, which assumes that there are uniform stresses and strains distributions in the fiber and the matrix respectively. It is found that there is an obvious difference between the FEM analysis and the simple numerical assessment. Only FEM can provide reasonable predictions of phase transformations in SMA/normal metal composites. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

Topology Optimization of Shape Memory Alloy Actuators using Element Connectivity Parameterization

DEFF Research Database (Denmark)

Langelaar, Matthijs; Yoon, Gil Ho; Kim, Yoon Young

2005-01-01

This paper presents the first application of topology optimization to the design of shape memory alloy actuators. Shape memory alloys (SMA’s) exhibit strongly nonlinear, temperature-dependent material behavior. The complexity in the constitutive behavior makes the topology design of SMA structure......) stiffness matrix of continuum finite elements. Therefore, any finite element code, including commercial codes, can be readily used for the ECP implementation. The key ideas and characteristics of these methods will be presented in this paper....

Shape Memory Alloy Cryogenic Transfer Coupling for Space Depot Docking Operations

Data.gov (United States)

National Aeronautics and Space Administration — The technical objective of the proposed effort is to establish the feasibility of using shape memory alloy (SMA) actuators for selected components of the automatic...

A 3D Printed Implantable Device for Voiding the Bladder Using Shape Memory Alloy (SMA) Actuators.

Science.gov (United States)

Hassani, Faezeh Arab; Peh, Wendy Yen Xian; Gammad, Gil Gerald Lasam; Mogan, Roshini Priya; Ng, Tze Kiat; Kuo, Tricia Li Chuen; Ng, Lay Guat; Luu, Percy; Yen, Shih-Cheng; Lee, Chengkuo

2017-11-01

Underactive bladder or detrusor underactivity (DU) is defined as a reduction of contraction strength or duration of the bladder wall. Despite the serious healthcare implications of DU, there are limited solutions for affected individuals. A flexible 3D printed implantable device driven by shape memory alloys (SMA) actuators is presented here for the first time to physically contract the bladder to restore voluntary control of the bladder for individuals suffering from DU. This approach is used initially in benchtop experiments with a rubber balloon acting as a model for the rat bladder to verify its potential for voiding, and that the operating temperatures are safe for the eventual implantation of the device in a rat. The device is then implanted and tested on an anesthetized rat, and a voiding volume of more than 8% is successfully achieved for the SMA-based device without any surgical intervention or drug injection to relax the external sphincter.

FRECUENCIAS NATURALES EN VIGAS ACTIVAMENTE TORSIONADAS USANDO ALAMBRES DE ALEACIÓN CON MEMORIA DE FORMA (SMA | NATURAL FREQUENCIES IN ACTVELY TWISTED BEAMS USING SHAPE MEMORY ALLOY (SMA WIRES

Directory of Open Access Journals (Sweden)

Gaetano Starlacci

2016-08-01

Full Text Available Changes in the geometry and stiffness of structural members can be obtained using Shape Memory Alloys (SMA wires, previously stretched, and externally attached to the member in a helical pattern. The wire was modeled assuming transformation from a pure martensitic phase to a pure austenitic phase. Natural frequency values before and after the SMA wire activation attached to the beam were calculated using the finite element method and these values were compared with those obtained from a model developed for pre-twisted stress-free cantilever members. The results obtained showed the active torsion influence over the structural element in the values of natural frequencies calculated.

Thermo-mechanical response and fatigue behavior of shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya [Tokyo Univ. (Japan). Dept. of Mechanical Engineering

1998-11-01

Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

Thermo-mechanical response and fatigue behavior of shape memory alloy

International Nuclear Information System (INIS)

Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya

1998-01-01

Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

Apparatus and Method for Low-Temperature Training of Shape Memory Alloys

Science.gov (United States)

Swanger, A. M.; Fesmire, J. E.; Trigwell, S.; Gibson, T. L.; Williams, M. K.; Benafan, O.

2015-01-01

An apparatus and method for the low-temperature thermo-mechanical training of shape memory alloys (SMA) has been developed. The experimental SMA materials are being evaluated as prototypes for applicability in novel thermal management systems for future cryogenic applications. Alloys providing two-way actuation at cryogenic temperatures are the chief target. The mechanical training regimen was focused on the controlled movement of rectangular strips, with S-bend configurations, at temperatures as low as 30 K. The custom holding fixture included temperature sensors and a low heat-leak linear actuator with a magnetic coupling. The fixture was mounted to a Gifford-McMahon cryocooler providing up to 25 W of cooling power at 20 K and housed within a custom vacuum chamber. Operations included both training cycles and verification of shape memory movement. The system design and operation are discussed. Results of the training for select prototype alloys are presented.

Experimental analyses of dynamical systems involving shape memory alloys

DEFF Research Database (Denmark)

Enemark, Søren; Savi, Marcelo A.; Santos, Ilmar F.

2015-01-01

The use of shape memory alloys (SMAs) in dynamical systems has an increasing importance in engineering especially due to their capacity to provide vibration reductions. In this regard, experimental tests are essential in order to show all potentialities of this kind of systems. In this work, SMA ...

Shape Memory Alloys (Part II: Classification, Production and Application

Directory of Open Access Journals (Sweden)

I. Ivanic

2014-09-01

Full Text Available Shape memory alloys (SMAs have been extensively investigated because of their unique shape memory behaviour, i.e. their ability to recover their original shape they had before deformation. Shape memory effect is related to the thermoelastic martensitic transformation. Austenite to martensite phase transformation can be obtained by mechanical (loading and thermal methods (heating and cooling. Depending on thermomechanical conditions, SMAs demonstrate several thermomechanical phenomena, such as pseudoelasticity, superelasticity, shape memory effect (one-way and two-way and rubber-like behaviour. Numerous alloys show shape memory effect (NiTi-based alloys, Cu-based alloys, Fe-based alloys etc.. Nitinol (NiTi is the most popular and the most commonly used SMA due to its superior thermomechanical and thermoelectrical properties. NiTi alloys have greater shape memory strain and excellent corrosion resistance compared to Cu – based alloys. However, they are very costly. On the other hand, copper-based alloys (CuZn and CuAl based alloys are much less expensive, easier to manufacture and have a wider range of potential transformation temperatures. The characteristic transformation temperatures of martensitic transformation of CuAlNi alloys can lie between −200 and 200 °C, and these temperatures depend on Al and Ni content. Among the Cu – based SMAs, the most frequently applied are CuZnAl and CuAlNi alloys. Although CuZnAl alloys with better mechanical properties are the most popular among the Cu-based SMAs, they lack sufficient thermal stability, while CuAlNi shape memory alloys, in spite of their better thermal stability, have found only limited applications due to insufficient formability owing to the brittle γ2 precipitates. The most important disadvantage of polycrystalline CuAlNi alloys is a small reversible deformation (one-way shape memory effect: up to 4 %; two-way shape memory effect: only approximately 1.5 % due to intergranular

Vacuum Plasma Spray Formed High Transition Temperature Shape Memory Alloys, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Smart materials control of aero-surfaces based on shape memory alloys (SMA) is seeing increased use for improving of future subsonic fixed wing aircraft aero-surface...

Experimental and numerical investigations of shape memory alloy helical springs

International Nuclear Information System (INIS)

Aguiar, Ricardo A A; Pacheco, Pedro M C L; Savi, Marcelo A

2010-01-01

Shape memory alloys (SMAs) belong to the class of smart materials and have been used in numerous applications. Solid phase transformations induced either by stress or temperature are behind the remarkable properties of SMAs that motivate the concept of innovative smart actuators for different purposes. The SMA element used in these actuators can assume different forms and a spring is an element usually employed for this aim. This contribution deals with the modeling, simulation and experimental analysis of SMA helical springs. Basically, a one-dimensional constitutive model is assumed to describe the SMA thermomechanical shear behavior and, afterwards, helical springs are modeled by considering a classical approach for linear-elastic springs. A numerical method based on the operator split technique is developed. SMA helical spring thermomechanical behavior is investigated through experimental tests performed with different thermomechanical loadings. Shape memory and pseudoelastic effects are treated. Numerical simulations show that the model results are in close agreement with those obtained by experimental tests, revealing that the proposed model captures the general thermomechanical behavior of SMA springs

The Effects of Different Electrode Types for Obtaining Surface Machining Shape on Shape Memory Alloy Using Electrochemical Machining

Science.gov (United States)

Choi, S. G.; Kim, S. H.; Choi, W. K.; Moon, G. C.; Lee, E. S.

2017-06-01

Shape memory alloy (SMA) is important material used for the medicine and aerospace industry due to its characteristics called the shape memory effect, which involves the recovery of deformed alloy to its original state through the application of temperature or stress. Consumers in modern society demand stability in parts. Electrochemical machining is one of the methods for obtained these stabilities in parts requirements. These parts of shape memory alloy require fine patterns in some applications. In order to machine a fine pattern, the electrochemical machining method is suitable. For precision electrochemical machining using different shape electrodes, the current density should be controlled precisely. And electrode shape is required for precise electrochemical machining. It is possible to obtain precise square holes on the SMA if the insulation layer controlled the unnecessary current between electrode and workpiece. If it is adjusting the unnecessary current to obtain the desired shape, it will be a great contribution to the medical industry and the aerospace industry. It is possible to process a desired shape to the shape memory alloy by micro controlling the unnecessary current. In case of the square electrode without insulation layer, it derives inexact square holes due to the unnecessary current. The results using the insulated electrode in only side show precise square holes. The removal rate improved in case of insulated electrode than others because insulation layer concentrate the applied current to the machining zone.

Thermo-Mechanical Methodology for Stabilizing Shape Memory Alloy Response

Science.gov (United States)

Padula, Santo

2013-01-01

This innovation is capable of significantly reducing the amount of time required to stabilize the strain-temperature response of a shape memory alloy (SMA). Unlike traditional stabilization processes that take days to weeks to achieve stabilized response, this innovation accomplishes stabilization in a matter of minutes, thus making it highly useful for the successful and practical implementation of SMA-based technologies in real-world applications. The innovation can also be applied to complex geometry components, not just simple geometries like wires or rods.

Torsional Properties of TiNi Shape Memory Alloy Tape for Rotary Actuator

Science.gov (United States)

Takeda, K.; Tobushi, H.; Mitsui, K.; Nishimura, Y.; Miyamoto, K.

2012-12-01

In order to develop novel shape memory actuators, the torsional deformation of a shape memory alloy (SMA) tape and the actuator models driven by the tape were investigated. The results obtained can be summarized as follows. In the SMA tape subjected to torsion, the martensitic transformation appears along both edges of the tape due to elongation of these elements and grows to the central part. The fatigue life in both the pulsating torsion and alternating torsion is expressed by the unified relationship of the dissipated work in each cycle. Based on an opening and closing door model and a solar-powered active blind model, the two-way rotary driving actuator with a small and simple mechanism can be developed by using torsion of the SMA tape.

Shape Memory Alloy Actuator Design: CASMART Collaborative Best Practices

Science.gov (United States)

Benafan, Othmane; Brown, Jeff; Calkins, F. Tad; Kumar, Parikshith; Stebner, Aaron; Turner, Travis; Vaidyanathan, Raj; Webster, John; Young, Marcus L.

2011-01-01

Upon examination of shape memory alloy (SMA) actuation designs, there are many considerations and methodologies that are common to them all. A goal of CASMART's design working group is to compile the collective experiences of CASMART's member organizations into a single medium that engineers can then use to make the best decisions regarding SMA system design. In this paper, a review of recent work toward this goal is presented, spanning a wide range of design aspects including evaluation, properties, testing, modeling, alloy selection, fabrication, actuator processing, design optimization, controls, and system integration. We have documented each aspect, based on our collective experiences, so that the design engineer may access the tools and information needed to successfully design and develop SMA systems. Through comparison of several case studies, it is shown that there is not an obvious single, linear route a designer can adopt to navigate the path of concept to product. SMA engineering aspects will have different priorities and emphasis for different applications.

Nonlinear finite element formulation for analyzing shape memory alloy cylindrical panels

International Nuclear Information System (INIS)

Mirzaeifar, R; Shakeri, M; Sadighi, M

2009-01-01

In this paper, a general incremental displacement based finite element formulation capable of modeling material nonlinearities based on first-order shear deformation theory (FSDT) is developed for cylindrical shape memory alloy (SMA) shells. The Boyd–Lagoudas phenomenological model with polynomial hardening in conjunction with 3D incremental convex cutting plane explicit algorithm is implemented for preparing the SMA constitutive model in the finite element formulation. Several numerical examples are presented for demonstrating the performance of the proposed formulation in stress, deflection and phase transformation analysis of pseudoelastic behavior of shape memory cylindrical panels with various boundary conditions. Also, it is shown that the presented formulation can be implemented for studying plates and beams with rectangular cross section

Working principle of bio-inspired shape memory alloy composite actuators

International Nuclear Information System (INIS)

Smith, Colin; Villanueva, Alex; Joshi, Keyur; Tadesse, Yonas; Priya, Shashank

2011-01-01

Recently, bio-inspired shape memory alloy composite (BISMAC) actuators have been shown to mimic the deformation characteristics of natural jellyfish medusa. In this study, a constant cross-section BISMAC actuator was characterized in terms of bending deflection and force in conjunction with microscopy to understand its deformation mechanism. The actuator showed bending deflection of 111% with respect to the active length along with a blocking force of 0.061 N. The resulting energy density of the composite actuator was 4929 J m −3 at an input voltage and current level of 12 V and 0.7 A, respectively. For a dry-state actuator, this performance is extremely high and represents an optimum combination of force and deflection. Experiments reveal that BISMAC's performance is related to the moment induced from tip attachment of the shape memory alloy (SMA) rather than to friction within the composite structure. A physics-based model of BISMAC structure is presented which shows that the actuator is highly sensitive to the distance between the SMA wire and the incompressible component. While SMA has both stress and strain limitations, the limiting factor in BISMAC actuators is dependent on separation distance. The limiting factor in BISMAC's suitability for mimicking the performance of medusa was experimentally found to be related to the maximum 4% strain of the SMA and not its force generation. (fast track communication)

Dynamical Jumps in a Shape Memory Alloy Oscillator

Directory of Open Access Journals (Sweden)

H. S. Oliveira

2014-01-01

Full Text Available The dynamical response of systems with shape memory alloy (SMA elements presents a rich behavior due to their intrinsic nonlinear characteristic. SMA’s nonlinear response is associated with both adaptive dissipation related to hysteretic behavior and huge changes in properties caused by phase transformations. These characteristics are attracting much technological interest in several scientific and engineering fields, varying from medical to aerospace applications. An important characteristic associated with dynamical response of SMA system is the jump phenomenon. Dynamical jumps result in abrupt changes in system behavior and its analysis is essential for a proper design of SMA systems. This paper discusses the nonlinear dynamics of a one degree of freedom SMA oscillator presenting pseudoelastic behavior and dynamical jumps. Numerical simulations show different aspects of this kind of behavior, illustrating its importance for a proper understanding of nonlinear dynamics of SMA systems.

Functional Performances of CuZnAl Shape Memory Alloy Open-Cell Foams

Science.gov (United States)

Biffi, C. A.; Casati, R.; Bassani, P.; Tuissi, A.

2018-01-01

Shape memory alloys (SMAs) with cellular structure offer a unique mixture of thermo-physical-mechanical properties. These characteristics can be tuned by changing the pore size and make the shape memory metallic foams very attractive for developing new devices for structural and functional applications. In this work, CuZnAl SMA foams were produced through the liquid infiltration of space holder method. In comparison, a conventional CuZn brass alloy was foamed trough the same method. Functional performances were studied on both bulk and foamed SMA specimens. Calorimetric response shows similar martensitic transformation (MT) below 0 °C. Compressive response of CuZnAl revealed that mechanical behavior is strongly affected by sample morphology and that damping capacity of metallic foam is increased above the MT temperatures. The shape memory effect was detected in the CuZnAl foams. The conventional brass shows a compressive response similar to that of the martensitic CuZnAl, in which plastic deformation accumulation occurs up to the cellular structure densification after few thermal cycles.

Rotor Embedded with Shape Memory Alloy Wires

Directory of Open Access Journals (Sweden)

K. Gupta

2000-01-01

Full Text Available In the present analysis, the fundamental natural frequency of a Jeffcott and a two-mass rotor with fibre reinforced composite shaft embedded with shape memory alloy (SMA wires is evaluated by Rayleigh's procedure. The flexibility of rotor supports is taken into account. The effect of three factors, either singly or in combination with each other, on rotor critical speed is studied. The three factors are: (i increase in Young's modulus of SMA (NITINOL wires when activated, (ii tension in wires because of phase recovery stresses, and (iii variation of support stiffness by three times because of activation of SMA in rotor supports. It is shown by numerical examples that substantial variation in rotor critical speeds can be achieved by a combination of these factors which can be effectively used to avoid resonance during rotor coast up/down.

Deployable auxetic shape memory alloy cellular antenna demonstrator: design, manufacturing and modal testing

International Nuclear Information System (INIS)

Jacobs, S; Coconnier, C; DiMaio, D; Scarpa, F; Martinez, J; Toso, M

2012-01-01

This work describes the design, manufacturing and testing of a deployable antenna for deep-space missions based on a hybrid honeycomb truss made of shape memory alloy (SMA). The deployable characteristics are enhanced by the equivalent auxetic (negative Poisson’s ratio) behaviour of the cellular configuration. Specific emphasis is placed on the modal analysis techniques used to test the lightweight SMA structure. (paper)

Acoustic recognition of stress induced martensitic transformations in Cu-based shape memory alloys

Czech Academy of Sciences Publication Activity Database

Novák, Václav; Landa, Michal; Šittner, Petr

2003-01-01

Roč. 112, - (2003), s. 593-596 ISSN 1155-4339 R&D Projects: GA AV ČR IAA1048107; GA ČR GA106/01/0396 Institutional research plan: CEZ:AV0Z1010914 Keywords : shape memory alloys(SMA) * Cu-based SMA * Martensitic phase transformation * acoustic emission Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.319, year: 2003

High-Temperature Shape Memory Alloys

Science.gov (United States)

Biffi, C. A.; Tuissi, A.

2014-10-01

In this paper, an experimental study of laser micro-processing on a Cu-Zr-based shape memory alloy (SMA), which is suitable for high-temperature (HT) applications, is discussed. A first evaluation of the interaction between a laser beam and Zr50Cu28Ni7Co15 HT SMA is highlighted. Single laser pulses at various levels of power and pulse duration were applied to evaluate their effect on the sample surfaces. Blind and through microholes were produced with sizes on the order of a few hundreds of microns; the results were characterized from the morphological viewpoint using a scanning electron microscope. The high beam quality allows the holes to be created with good circularity and little melted material around the hole periphery. An analysis of the chemical composition was performed using energy dispersive spectroscopy, revealing that compositional changes were limited, while important oxidation occurred on the hole surfaces. Additionally, laser micro-cutting tests were also proposed to evaluate the cut edge morphology and dimensions. The main result of this paper concerned the good behavior of the material upon interaction with the laser beam, which suggests that microfeatures can be successfully produced in this alloy.

Pseudo-elasticity and shape memory effect on the TiNiCoV alloy

International Nuclear Information System (INIS)

Hsu, S.E.; Yeh, M.T.; Hsu, I.C.; Chang, S.K.; Dai, Y.C.; Wang, J.Y.

2000-01-01

Unlike most of the structural intermetallic compound, TiNi is an exceptional case of inherent ductility. Besides its amusing behavior of high damping capacity due to martensitic transformation, the duel properties of shape memory and pseudo-elasticity co-exhibited in the same V and Co-modified TiNi-SMA at various temperature will attract another attention in modern manufacturing technology. The objective of this paper is to investigate the pseudo-elasticity and strain rate effect on TiNiCoV-SMA. The presence of dual behavior of super-elasticity and shape memory effect is technological significant for application of advanced materials on the structural component. An illustration of application of TiNiCoV shape memory alloy on the face of golf club head will be presented in this paper. (orig.)

Finite element analysis of Al 2024/Cu-Al-Ni shape memory alloy composites with defects/cracks

Science.gov (United States)

Kotresh, M.; Benal, M. M., Dr; Siddalinga Swamy, N. H., Dr

2018-02-01

In this work, a numerical approach to predict the stress field behaviour of defect/crack in shape memory alloy (SMA) particles reinforced composite known as the adaptive composite is presented. Simulation is based on the finite element method. The critical stress field approach was used to determine the stresses around defect/crack. Thereby stress amplification issue is being resolved. In this paper, the effect volume % of shape memory alloy and shape memory effect of reinforcement for as-cast and SME trained composites are examined and discussed. Shape memory effect known as training is achieved by pre-straining of reinforcement particles by equivalent changes in their expansion coefficients.

An investigation of shape memory alloys as actuating elements in aerospace morphing applications

DEFF Research Database (Denmark)

Karagiannis, Dimitrios; Stamatelos, Dimtrios; Kappatos, Vasileios

2017-01-01

Two innovative actuating concepts for aerospace morphing applications, based on Shape Memory Alloys (SMAs), are proposed. The first concept investigates a composite plate incorporating embedded SMA wires. A Nonlinear Auto Regressive with eXogenous excitation (NARX) model is proposed for controlling...

Load carrying capacity of RCC beams by replacing steel reinforcement bars with shape memory alloy bars

Science.gov (United States)

Bajoria, Kamal M.; Kaduskar, Shreya S.

2016-04-01

In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

Nonlinear dynamics and bifurcation characteristics of shape memory alloy thin films subjected to in-plane stochastic excitation

International Nuclear Information System (INIS)

Zhu, Zhi-Wen; Zhang, Qing-Xin; Xu, Jia

2014-01-01

A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters

Shape memory alloy actuated accumulator for ultra-deepwater oil and gas exploration

Science.gov (United States)

Patil, Devendra; Song, Gangbing

2016-04-01

As offshore oil and gas exploration moves further offshore and into deeper waters to reach hydrocarbon reserves, it is becoming essential for the industry to develop more reliable and efficient hydraulic accumulators to supply pressured hydraulic fluid for various control and actuation operations, such as closing rams of blowout preventers and controlling subsea valves on the seafloor. By utilizing the shape memory effect property of nitinol, which is a type of shape memory alloy (SMA), an innovative SMA actuated hydraulic accumulator prototype has been developed and successfully tested at Smart Materials and Structure Laboratory at the University of Houston. Absence of gas in the developed SMA accumulator prototype makes it immune to hydrostatic head loss caused by water depth and thus reduces the number of accumulators required in deep water operations. Experiments with a feedback control have demonstrated that the proposed SMA actuated accumulator can provide precisely regulated pressurized fluids. Furthermore the potential use of ultracapacitors along with an embedded system to control the electric power supplied to SMA allows this accumulator to be an autonomous device for deployment. The developed SMA accumulator will make deepwater oil extraction systems more compact and cost effective.

Characterization of NiTi shape memory alloys using dual kriging interpolation

International Nuclear Information System (INIS)

Trochu, F.; Sacepe, N.; Volkov, O.; Turenne, S.

1999-01-01

A large number of industrial applications could benefit from the remarkable properties of shape memory alloys (SMA). The development of a general material law is the first important step before reliable design calculations of shape memory devices can be carried out. This paper presents a new phenomenological constitutive law based on dual kriging, which is a powerful mathematical tool used here as interpolation method to simulate the macroscopic mechanical behavior of shape memory alloys. From a set of experimental strain-temperature curves at constant loads, two deformation surfaces are constructed in the stress, strain and temperature space which describe the cooling and heating behaviors of the material for any stress. The response of a specimen subjected to complex thermomechanical loading can be calculated by dual kriging form a general 3-dimensional parametric solid constructed inside the hysteretic domain delimited by the main cooling and heating deformation surfaces. This approach presents the advantage of yielding immediately the explicit equation of any partial cycle inside the main hysteretic domain, thus yielding a general material law for shape memory alloys. Preliminary validation for a set of simple examples demonstrates the potential of this new model that includes in a single formulation superelasticity, rubber-like behavior and shape memory effect. (orig.)

Effect of heat treatment on transformation behavior of Ti-Ni-V shape memory alloy

International Nuclear Information System (INIS)

He Zhirong; Liu Manqian

2011-01-01

Highlights: → New shape memory alloy (SMA) - Ti-50.8Ni-0.5V SMA. → The evolution laws of transformation types of annealed Ti-50.8Ni-0.5V SMA. → The evolution laws of transformation types of aged Ti-50.8Ni-0.5V SMA. → The effect laws of annealing on transformation temperature and hysteresis of the alloy. → The effect laws of aging on transformation temperature and hysterises of the alloy. - Abstract: Effects of annealing and aging processes on the transformation behaviors of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of differential scanning calorimetry (DSC). The A → R/R → A (A - parent phase, R - R phase) type one-stage reversible transformation occurs in 350-400 deg. C annealed alloy, the A → R → M/M → R → A (M - martensite) type two-stage transformation occurs in 450-500 deg. C annealed alloy, the A → R → M/M → A type transformation occurs in 550 deg. C annealed alloy, and A → M/M → A type transformation occurs in the alloy annealed at above 600 deg. C upon cooling/heating. The transformation type of 300 deg. C aged alloy is A → R/R → A, and that of 500 deg. C aged alloy is A → R → M/M → A, while that of 400 deg. C aged alloy changes from A → R/R → A to A → R → M/M → R → A with increasing aging time. The effects of annealing and aging processes on R and M transformation temperatures and temperature hysteresis are given. The influence of annealing and aging temperature on transformation behaviors is stronger than that of annealing and aging time.

Bio-inspired Miniature Suction Cups Actuated by Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Hu Bing-shan

2010-02-01

Full Text Available Wall climbing robots using negative pressure suction always employ air pumps which have great noise and large volume. Two prototypes of bio-inspired miniature suction cup actuated by shape memory alloy (SMA are designed based on studying characteristics of biologic suction apparatuses, and the suction cups in this paper can be used as adhesion mechanisms for miniature wall climbing robots without air pumps. The first prototype with a two-way shape memory effect (TWSME extension TiNi spring imitates the piston structure of the stalked sucker; the second one actuated by a one way SMA actuator with a bias has a basic structure of stiff margin, guiding element, leader and elastic element. Analytical model of the second prototype is founded considering the constitutive model of the SMA actuator, the deflection of the thin elastic plate under compound load and the thermo-dynamic model of the sealed air cavity. Experiments are done to test their suction characteristics, and the analytical model of the second prototype is simulated on Matlab/simulink platform and validated by experiments.

Bio-inspired Miniature Suction Cups Actuated by Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Hu Bing-Shan

2009-09-01

Full Text Available Wall climbing robots using negative pressure suction always employ air pumps which have great noise and large volume. Two prototypes of bio-inspired miniature suction cup actuated by shape memory alloy (SMA are designed based on studying characteristics of biologic suction apparatuses, and the suction cups in this paper can be used as adhesion mechanisms for miniature wall climbing robots without air pumps. The first prototype with a two-way shape memory effect (TWSME extension TiNi spring imitates the piston structure of the stalked sucker; the second one actuated by a one way SMA actuator with a bias has a basic structure of stiff margin, guiding element, leader and elastic element. Analytical model of the second prototype is founded considering the constitutive model of the SMA actuator, the deflection of the thin elastic plate under compound load and the thermo-dynamic model of the sealed air cavity. Experiments are done to test their suction characteristics, and the analytical model of the second prototype is simulated on Matlab/simulink platform and validated by experiments.

Functional Characterization of a Novel Shape Memory Alloy

Science.gov (United States)

Collado, M.; Cabás, R.; San Juan, J.; López-Ferreño, I.

2014-07-01

A novel shape memory alloy (SMA) has been developed as an alternative to currently available alloys. This alloy, commercially known by its proprietary brand SMARQ, shows a higher working range of temperatures with respect to the SMA materials used until now in actuators, limited to environment temperatures below 90 °C. SMARQ is a high temperature SMA (HTSMA) based on a fully European material technology and production processes, which allows the manufacture of high quality products, with tuneable transformation temperatures up to 200 °C. Both, material and production processes have been evaluated for its use in space applications. A full characterization test campaign has been completed in order to obtain the material properties and check its suitability to be used as active material in space actuators. In order to perform the functional characterization of the material, it has been considered as the key element of a basic SMA actuator, consisting in the SMA wire and the mechanical and electrical interfaces. The functional tests presented in this work have been focused on the actuator behavior when heated by means of an electrical current. Alloy composition has been adjusted in order to match a transition temperature (As) of +145 °C, which satisfies the application requirements of operating temperatures in the range of -70 and +125 °C. Details of the tests and results of the characterization test campaign, focused in the material unique properties for their use in actuators, will be presented in this work. Some application examples in the field of space mechanisms and actuators, currently under development, will be summarized as part of this work, demonstrating the technology suitability as active material for space actuators.

Bioinspired Soft Actuation System Using Shape Memory Alloys

OpenAIRE

Cianchetti, Matteo; Licofonte, Alessia; Follador, Maurizio; Rogai, Francesco; Laschi, Cecilia

2014-01-01

Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors’ previous works on shape memory alloy (SMA) springs used as soft actuators, a specific arrangement of such SM...

Cyclic degradation of antagonistic shape memory actuated structures

International Nuclear Information System (INIS)

Sofla, A Y N; Elzey, D M; Wadley, H N G

2008-01-01

Antagonistic shape memory actuated structures exploit opposing pairs of one-way shape memory alloy (SMA) linear actuators to create devices capable of a fully reversible response. Unlike many conventional reversible SMA devices they do not require bias force components (springs) to return them to their pre-actuated configuration. However, the repeated use of SMA antagonistic devices results in the accumulation of plastic strain in the actuators which can diminish their actuation stroke. We have investigated this phenomenon and the effect of shape memory alloy pre-strain upon it for near equi-atomic NiTi actuators. We find that the degradation eventually stabilizes during cycling. A thermomechanical treatment has been found to significantly reduce degradation in cyclic response of the actuators

Shape memory behavior of single and polycrystalline nickel rich nickel titanium alloys

Science.gov (United States)

Kaya, Irfan

NiTi is the most commonly used shape memory alloy (SMA) and has been widely used for bio-medical, electrical and mechanical applications. Nickel rich NiTi shape memory alloys are coming into prominence due to their distinct superelasticity and shape memory properties as compared to near equi-atomic NiTi shape memory alloys. Besides, their lower density and higher work output than steels makes these alloys an excellent candidate for aerospace and automotive industry. Shape memory properties and phase transformation behavior of high Ni-rich Ni54Ti46 (at.%) polycrystals and Ni-rich Ni 51Ti49 (at.%) single-crystals are determined. Their properties are sensitive to heat treatments that affect the phase transformation behavior of these alloys. Phase transformation properties and microstructure were investigated in aged Ni54Ti46 alloys with differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) to reveal the precipitation characteristics and R-phase formation. It was found that Ni54Ti46 has the ability to exhibit perfect superelasticity under high stress levels (~2 GPa) with 4% total strain after 550°C-3h aging. Stress independent R-phase transformation was found to be responsible for the change in shape memory behavior with stress. The shape memory responses of [001], [011] and [111] oriented Ni 51Ti49 single-crystals alloy were reported under compression to reveal the orientation dependence of their shape memory behavior. It has been found that transformation strain, temperatures and hysteresis, Classius-Clapeyron slopes, critical stress for plastic deformation are highly orientation dependent. The effects of precipitation formation and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]- oriented Ni51Ti49 shape memory alloy were revealed. Additionally, aligned Ni4Ti3 precipitates were formed in a single crystal of Ni51Ti49 alloy by aging under applied compression stress along the

Space Qualification Testing of a Shape Memory Alloy Deployable CubeSat Antenna

Science.gov (United States)

2016-09-15

from a specific input vibration . This excitation vibration can be applied acoustically through a speaker or physically by an impact hammer. NASA...Shape Memory Alloy (SMA) L-band deployable QHA. In this research, a testing approach is developed to conduct random vibration , thermal vacuum...92 4.4 Vibration Test Results

A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators

International Nuclear Information System (INIS)

Sepiani, H.; Ebrahimi, F.; Karimipour, H.

2009-01-01

This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant

Synthesis of shape memory alloys using electrodeposition

Science.gov (United States)

Hymer, Timothy Roy

Shape memory alloys are used in a variety of applications. The area of micro-electro-mechanical systems (MEMS) is a developing field for thin film shape memory alloys for making actuators, valves and pumps. Until recently thin film shape memory alloys could only be made by rapid solidification or sputtering techniques which have the disadvantage of being "line of sight". At the University of Missouri-Rolla, electrolytic techniques have been developed that allow the production of shape memory alloys in thin film form. The advantages of this techniques are in-situ, non "line of sight" and the ability to make differing properties of the shape memory alloys from one bath. This research focused on the electrodeposition of In-Cd shape memory alloys. The primary objective was to characterize the electrodeposited shape memory effect for an electrodeposited shape memory alloy. The effect of various operating parameters such as peak current density, temperature, pulsing, substrate and agitation were investigated and discussed. The electrodeposited alloys were characterized by relative shape memory effect, phase transformation, morphology and phases present. Further tests were performed to optimize the shape memory by the use of a statistically designed experiment. An optimized shape memory effect for an In-Cd alloy is reported for the conditions of the experiments.

Mechanical and microstructural properties of Cu-Al-Ni-Mn-Zr shape memory alloy processed by spray forming

Energy Technology Data Exchange (ETDEWEB)

Cava, R.D.; Bolfarini, C.; Kiminami, C.S.; Mazzer, E.M.; Pedrosa, V.M.; Botta, W.J.; Gargarella, P. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

2016-07-01

Full text: Cu-based shape memory alloys (SMA) presents higher thermal and electrical conductivities, low material cost and combine good mechanical properties with a pronounced shape memory effect [1]. By using rapid solidification methods, their microstructure is refined and detrimental segregations can be avoided, which results in better mechanical properties. Additionally, the microalloying additions as Ti, B, Si and Zr can refine the grains and improve of mechanical and thermal properties of Cu-based SMA alloys [2-4]. In this investigation the Cu81.95Al11.35Ni3.2Mn3Zr0.5 (wt%) SMA alloy has been processed by spray forming in order to investigate the potential of achieving a deposit with adequate microstructure with goal to a SMA part production. The alloy was atomized with nitrogen gas at pressure of 0.5MPa. The microstructure of the deposit was characterized by optical and scanning electron microscopy and X-ray diffraction. The deposit presented homogeneous microstructure consisting of equiaxial grains with martensite microstructure and mean grain size of 30 ?m. The shape memory effect and the temperatures transformation have been evaluated by differential scanning calorimetric. The mechanical properties were evaluated by tensile and compression tests at room and at 220 deg C(T>Af) temperatures. [1] T. Waitz, et al., T, J. of the Mechanics and Physics of Solids, 55, 2007. [2] D. W. Roh, et al., Metall Trans. A, 21, 1990. [3] D. W. Roh, et al., Mat. Sci. and Eng. A136, 1991. (author)

The response of macrophages to a Cu-Al-Ni shape memory alloy.

Science.gov (United States)

Colić, Miodrag; Tomić, Sergej; Rudolf, Rebeka; Anzel, Ivan; Lojen, Gorazd

2010-09-01

Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but little is known about their biocompatibility. The aim of this work was to study the response of rat peritoneal macrophages (PMØ) to a Cu-Al-Ni SMA in vitro, by measuring the functional activity of mitochondria, necrosis, apoptosis, and production of proinflammatory cytokines. Rapidly solidified (RS) thin ribbons were used for the tests. The control alloy was a permanent mold casting of the same composition, but without the shape memory effect. Our results showed that the control alloy was severely cytotoxic, whereas RS ribbons induced neither necrosis nor apoptosis of PMØ. These findings correlated with the data that RS ribbons are significantly more resistant to corrosion compared to the control alloy, as judged by the lesser release of Cu and Ni in the conditioning medium. However, the ribbons generated intracellular reactive oxygen species and upregulated the production of IL-6 by PMØ. These effects were almost completely abolished by conditioning the RS ribbons for 5 weeks. In conclusion, RS significantly improves the corrosion stability and biocompatibility of Cu-Al-Ni SMA. The biocompatibility of this functional material could be additionally enhanced by conditioning the ribbons in cell culture medium.

Shape memory alloy fracture as a deployment actuator

International Nuclear Information System (INIS)

Buban, Darrick M; Frantziskonis, George N

2013-01-01

The paper reports an experimental investigation into using shape memory alloy (SMA) as a deployment actuator. SMA specimens were heated and pulled to failure or pulled and heated to failure, thus developing an environmental and structural operating envelope for application as deployment mechanisms. The experimental results strongly suggest that SMAs can be implemented as deployment actuators. Recorded data shows that SMA fracture is possible over a wide range of temperatures and strains, filling a material performance gap not found in the literature. The obtained information allows design engineers to appropriately size SMAs given the design requirements for achieving the desired deployment effects. The major conclusion of the reported work is that SMAs as actuators are strong competitors to typical existing deployment efforts that use explosive or non-explosive actuators having implementation drawbacks such as the expense associated with special handling and the volume encountered in mounting the devices. (paper)

[Experimental study of an intratracheal stent made of shape memory alloy].

Science.gov (United States)

Yoshimura, M; Tsugawa, C; Tsubota, N

1994-11-01

To develop a new prosthesis for treating tracheal stenosis and tracheobronchomalacia, we examined the usefulness of an intratracheal stent made of shape memory alloy (SMA), a titanium-nickel alloy composed of 50% of each metal. At its recovery temperature (37 degrees C), the SMA stent was designed to recall the memorized shape of a coil with a diameter of 5 or 6 mm and a length of 10 mm. For the present experiment, it was transformed to a smaller coil 3 mm in diameter at a low temperature (-50 degrees C) and then loaded into the prosthesis introducer tube. An experimental model of potentially fatal tracheomalacia was made surgically by cutting and fracturing the tracheal cartilages of rabbits and tracheal collapse was confirmed by rigid bronchoscope. The introducer tube with the SMA stent was inserted and then the prosthesis was advanced into the collapsed segment of the trachea using the stent pusher. The SMA stent warmed bo body temperature and recovered its memorized shape after 1-2 min. In 3 out of 8 rabbits, follow-up bronchoscopy performed at 6, 8, and 10 months after implantation revealed satisfactory patency of the SMA stent and the trachea. After follow-up, 3 animals were sacrificed for histological observation, which showed little proliferation of granulation tissue and no dislocation of the SMA stent from the malacic portion. The remaining 5 rabbits have been followed for 18-24 months and are doing well. We conclude that the SMA stent maintains good tracheal patency, causes little reaction in the tracheal wall, and is easy to handle. Thus, it shows the potential for clinical application.

Fabrication of a smart air intake structure using shape memory alloy wire embedded composite

International Nuclear Information System (INIS)

Jung, Beom-Seok; Kim, Min-Saeng; Kim, Ji-Soo; Kim, Yun-Mi; Lee, Woo-Yong; Ahn, Sung-Hoon

2010-01-01

Shape memory alloys (SMAs) have been actively studied in many fields utilizing their high energy density. Applying SMA wire-embedded composite to aerospace structures, such as air intake of jet engines and guided missiles, is attracting significant attention because it could generate a comparatively large actuating force. In this research, a scaled structure of SMA wire-embedded composite was fabricated for the air intake of aircraft. The structure was composed of several prestrained Nitinol (Ni-Ti) SMA wires embedded in intersection -shape glass fabric reinforced plastic (GFRP), and it was cured at room temperature for 72 h. The SMA wire-embedded GFRP could be actuated by applying electric current through the embedded SMA wires. The activation angle generated from the composite structure was large enough to make a smart air intake structure.

Determination of strain fields in porous shape memory alloys using micro-computed tomography

Science.gov (United States)

Bormann, Therese; Friess, Sebastian; de Wild, Michael; Schumacher, Ralf; Schulz, Georg; Müller, Bert

2010-09-01

Shape memory alloys (SMAs) belong to 'intelligent' materials since the metal alloy can change its macroscopic shape as the result of the temperature-induced, reversible martensite-austenite phase transition. SMAs are often applied for medical applications such as stents, hinge-less instruments, artificial muscles, and dental braces. Rapid prototyping techniques, including selective laser melting (SLM), allow fabricating complex porous SMA microstructures. In the present study, the macroscopic shape changes of the SMA test structures fabricated by SLM have been investigated by means of micro computed tomography (μCT). For this purpose, the SMA structures are placed into the heating stage of the μCT system SkyScan 1172™ (SkyScan, Kontich, Belgium) to acquire three-dimensional datasets above and below the transition temperature, i.e. at room temperature and at about 80°C, respectively. The two datasets were registered on the basis of an affine registration algorithm with nine independent parameters - three for the translation, three for the rotation and three for the scaling in orthogonal directions. Essentially, the scaling parameters characterize the macroscopic deformation of the SMA structure of interest. Furthermore, applying the non-rigid registration algorithm, the three-dimensional strain field of the SMA structure on the micrometer scale comes to light. The strain fields obtained will serve for the optimization of the SLM-process and, more important, of the design of the complex shaped SMA structures for tissue engineering and medical implants.

Modiolus-Hugging Intracochlear Electrode Array with Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Kyou Sik Min

2013-01-01

Full Text Available In the cochlear implant system, the distance between spiral ganglia and the electrodes within the volume of the scala tympani cavity significantly affects the efficiency of the electrical stimulation in terms of the threshold current level and spatial selectivity. Because the spiral ganglia are situated inside the modiolus, the central axis of the cochlea, it is desirable that the electrode array hugs the modiolus to minimize the distance between the electrodes and the ganglia. In the present study, we propose a shape-memory-alloy-(SMA- embedded intracochlear electrode which gives a straight electrode a curved modiolus-hugging shape using the restoration force of the SMA as triggered by resistive heating after insertion into the cochlea. An eight-channel ball-type electrode array is fabricated with an embedded titanium-nickel SMA backbone wire. It is demonstrated that the electrode array changes its shape in a transparent plastic human cochlear model. To verify the safe insertion of the electrode array into the human cochlea, the contact pressures during insertion at the electrode tip and the contact pressures over the electrode length after insertion were calculated using a 3D finite element analysis. The results indicate that the SMA-embedded electrode is functionally and mechanically feasible for clinical applications.

A low-power high-flow shape memory alloy wire gas microvalve

International Nuclear Information System (INIS)

Gradin, Henrik; Braun, Stefan; Stemme, Göran; Van der Wijngaart, Wouter; Clausi, Donato; Peirs, Jan; Reynaerts, Dominiek

2012-01-01

In this paper the use of shape memory alloy (SMA) wire actuators for high gas flow control is investigated. A theoretical model for effective gas flow control is presented and gate microvalve prototypes are fabricated. The SMA wire actuator demonstrates the robust flow control of more than 1600 sccm at a pressure drop of 200 kPa. The valve can be successfully switched at over 10 Hz and at an actuation power of 90 mW. Compared to the current state-of-the-art high-flow microvalves, the proposed solution benefits from a low-voltage actuator with low overall power consumption. This paper demonstrate that SMA wire actuators are well suited for high-pressurehigh-flow applications. (paper)

A Constitutive Description for Shape Memory Alloys with the Growth of Martensite Band

Directory of Open Access Journals (Sweden)

Weiguo Li

2014-01-01

Full Text Available Based on the experimental results and the finite element analysis, a constitutive model is proposed for two phase shape memory alloys by introducing a compensative volumetric strain into a constrained relationship between the two phases, accounting for the reduced constraint due to the growth of martensite band. The pseudoelasticity of NiTi shape memory alloy micro-tube, subjected to pure tension, is analyzed and compared with the experimental results. It can be seen that the pseudoelastic behavior, especially the phenomena of a stress drop during tension processes, can be well described with the proposed model. The proposed model separates the complicated constitutive behavior of a shape memory alloy (SMA into simple responses arising respectively from its two phases, taking into account laminar microstructure, the thickness of martensite phase and the interaction between the two phases, and provides an easy but comprehensive method for the description of the constitutive behavior of SMAs under complex thermomechanical loading.

Superelastic SMA U-shaped dampers with self-centering functions

Science.gov (United States)

Wang, Bin; Zhu, Songye

2018-05-01

As high-performance metallic materials, shape memory alloys (SMAs) have been investigated increasingly by the earthquake engineering community in recent years, because of their remarkable self-centering (SC) and energy-dissipating capabilities. This paper systematically presents an experimental study on a novel superelastic SMA U-shaped damper (SMA-UD) with SC function under cyclic loading. The mechanical properties, including strength, SC ability, and energy-dissipating capability with varying loading amplitudes and strain rates are evaluated. Test results show that excellent and stable flag-shaped hysteresis loops are exhibited in multiple loading cycles. Strain rate has a negligible effect on the cyclic behavior of the SMA-UD within the dynamic frequency range of typical interest in earthquake engineering. Furthermore, a numerical investigation is performed to understand the mechanical behavior of the SMA-UD. The numerical model is calibrated against the experimental results with reasonable accuracy. Then, the stress–strain states with different phase transformations are also discussed.

MOSFET Switching Circuit Protects Shape Memory Alloy Actuators

Science.gov (United States)

Gummin, Mark A.

2011-01-01

A small-footprint, full surface-mount-component printed circuit board employs MOSFET (metal-oxide-semiconductor field-effect transistor) power switches to switch high currents from any input power supply from 3 to 30 V. High-force shape memory alloy (SMA) actuators generally require high current (up to 9 A at 28 V) to actuate. SMA wires (the driving element of the actuators) can be quickly overheated if power is not removed at the end of stroke, which can damage the wires. The new analog driver prevents overheating of the SMA wires in an actuator by momentarily removing power when the end limit switch is closed, thereby allowing complex control schemes to be adopted without concern for overheating. Either an integral pushbutton or microprocessor-controlled gate or control line inputs switch current to the actuator until the end switch line goes from logic high to logic low state. Power is then momentarily removed (switched off by the MOSFET). The analog driver is suited to use with nearly any SMA actuator.

A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

Science.gov (United States)

Notardonato, W. U.; Krishnan, V. B.; Singh, J. D.; Woodruff, T. R.; Vaidyanathan, R.

2005-01-01

Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.

A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

International Nuclear Information System (INIS)

Krishnan, V.B.; Singh, J.D.; Woodruff, T.R.; Vaidyanathan, R.; Notardonato, W.U.

2004-01-01

Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed

Treatment of patella fracture by claw-like shape memory alloy.

Science.gov (United States)

Hao, Wei; Zhou, Lugang; Sun, Yujie; Shi, Peng; Liu, Hongzhi; Wang, Xin

2015-07-01

Titanium-nickel shape memory alloy (Ti-Ni SMA) is characterized by shape-memory effect, super-elasticity, excellent fatigue behavior, corrosion resistance, acceptable biocompatibility and high damping capacity. Claw-like Ti-Ni SMA fixator (SMA-claw) has been used to treat transverse fracture of patella. 29 patients (19 males, 10 females) aged from 21 to 71 years old (averaged 43.0 years old) have been received open reduction and internal fixation with SMA-claw from January 2011 to December 2011. After operation, patients have been received gradual knee function exercises, followed by radiographic analysis and Lysholm Knee Score at 1, 2, 3, 6, 9 and 12 months postoperation. The mean follow-up time was 11.48 months (25 patients finished, 1 lost after 6 months and 3 lost after 9 months). Radiographic bone union occurred at 2 months (7 patients) or 3 months (22 patients). Satisfied range of motion for the knee joint has been observed with 1.90/141.72° (hyperextension/flexion) at 3 months, 4.83/143.97° at 6 months, 4.82/144.82° at 9 months and 5.2/145° at 12 months postsurgery. The Ti-Ni SMA-claw fixator produced good osteosynthesis effect by continuous recovery stress with relatively simple and minimally invasive handling process, which can be introduced as an alternative to traditional tension band technique for treatment of patellar transverse fracture.

Narrow thermal hysteresis of NiTi shape memory alloy thin films with submicrometer thickness

Energy Technology Data Exchange (ETDEWEB)

Hou, Huilong; Hamilton, Reginald F., E-mail: rfhamilton@psu.edu; Horn, Mark W. [Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2016-09-15

NiTi shape memory alloy (SMA) thin films were fabricated using biased target ion beam deposition (BTIBD), which is a new technique for fabricating submicrometer-thick SMA thin films, and the capacity to exhibit shape memory behavior was investigated. The thermally induced shape memory effect (SME) was studied using the wafer curvature method to report the stress-temperature response. The films exhibited the SME in a temperature range above room temperature and a narrow thermal hysteresis with respect to previous reports. To confirm the underlying phase transformation, in situ x-ray diffraction was carried out in the corresponding phase transformation temperature range. The B2 to R-phase martensitic transformation occurs, and the R-phase transformation is stable with respect to the expected conversion to the B19′ martensite phase. The narrow hysteresis and stable R-phase are rationalized in terms of the unique properties of the BTIBD technique.

Investigation of shape memory alloy honeycombs by means of a micromechanical analysis

International Nuclear Information System (INIS)

Freed, Yuval; Aboudi, Jacob; Gilat, Rivka

2008-01-01

Shape memory alloy (SMA) honeycombs are promising new smart materials which may be used for light-weight structures, biomedical implants, actuators and active structures. In this study, the behavior of several SMA honeycomb structures is investigated by means of a continuum-based thermomechanically coupled micromechanical analysis. To this end, macroscopic inelastic stress–strain responses of several topologies are investigated, both for pseudoelasticity and for shape memory effect. It was found that the triangular topology exhibits the best performance. In addition, the initial transformation surfaces are presented for all possible combinations of applied in-plane stresses. A special two-phase microstructure that is capable of producing an overall negative coefficient of thermal expansion is suggested and studied. In this configuration, in which one of the phases is a SMA, residual strains are being generated upon recovery. Here, the negative coefficient of thermal expansion appears to be associated with a larger amount of residual strain upon recovery. Furthermore, a two-dimensional SMA re-entrant topology that generates a negative in-plane Poisson's ratio is analyzed, and the effect of the full thermomechanical coupling is examined. Finally, the response of a particular three-dimensional microstructure is studied

The shape memory alloy actuator controlled by the Sun’s radiation

Science.gov (United States)

Riad, Amine; Alhamany, Abdelilah; Benzohra, Mouna

2017-07-01

Shape memory alloys (SMAs) have many thermo-mechanical characteristics which can return to their original value once exposed to a specific temperature. These materials are able to change their mechanical features such as shape, displacement or frequency in response to stress or heating; this may be useful for actuators in many fields such as aircraft, robotics and microsystems. In order to know the effect of the Sun’s radiation on SMAs we have conducted a numerical study that simulates a SMA actuator.

Shape memory alloy wires turn composites into smart structures: I. Material requirements

Science.gov (United States)

Schrooten, Jan; Michaud, Veronique J.; Zheng, Yanjun; Balta-Neumann, J. Antonio; Manson, Jan-Anders E.

2002-07-01

Composites containing thin Shape Memory Alloy (SMA) wires show great potential as materials able to adapt their shape, thermal behavior or vibrational properties to external stimuli. The functional properties of SMA-composites are directly related to the constraining effect of the matrix on the reversible martensitic transformation of the embedded pre-strained SMA wires. The present work reports results of a concerted European effort towards a fundamental understanding of the manufacturing and design of SMA composites. This first part investigates the transformational behavior of constrained SMA wires and its translation into functional properties of SMA composites. Thermodynamic and thermomechanical experiments were performed on SMA wires. A model was developed to simulate the thermomechanical behavior of the wires. From the screening of potential wires it was concluded that NiTiCu, as well as R-phase NiTi appeared as best candidates. Requirements for the host composite materials were surveyed. A Kevlar-epoxy system was chosen. Finally, the quality of the SMA wire-resin interface was assessed by two different techniques. These indicated that a thin oxide layer seems to provide the best interfacial strength. A temperature window in which SMA composites can be safely used was also defined. The manufacturing and properties of the SMA composites will be discussed in Part II.

Applications of Shape Memory Alloys for Neurology and Neuromuscular Rehabilitation

Directory of Open Access Journals (Sweden)

Simone Pittaccio

2015-05-01

Full Text Available Shape memory alloys (SMAs are a very promising class of metallic materials that display interesting nonlinear properties, such as pseudoelasticity (PE, shape memory effect (SME and damping capacity, due to high mechanical hysteresis and internal friction. Our group has applied SMA in the field of neuromuscular rehabilitation, designing some new devices based on the mentioned SMA properties: in particular, a new type of orthosis for spastic limb repositioning, which allows residual voluntary movement of the impaired limb and has no predetermined final target position, but follows and supports muscular elongation in a dynamic and compliant way. Considering patients in the sub-acute phase after a neurological lesion, and possibly bedridden, the paper presents a mobiliser for the ankle joint, which is designed exploiting the SME to provide passive exercise to the paretic lower limb. Two different SMA-based applications in the field of neuroscience are then presented, a guide and a limb mobiliser specially designed to be compatible with diagnostic instrumentations that impose rigid constraints in terms of electromagnetic compatibility and noise distortion. Finally, the paper discusses possible uses of these materials in the treatment of movement disorders, such as dystonia or hyperkinesia, where their dynamic characteristics can be advantageous.

Recent activities of association of shape memory alloys (ASMA) in Japan

International Nuclear Information System (INIS)

Kobayashi, J.; Yamauchi, K.; Miyashita, T.; Ohkata, I.; Narumi, S.; Suzuki, Y.

1995-01-01

The Association of Shape Memory Alloys(ASMA) was established in 1983 and systematic surveys on the Ni-Ti and Cu based SMAs were carried out until 1986. The ASMA is now reorganized as a private association. In this paper, we briefly introduce several SMA products of the member companies and present a couple of products, a static rock breaking system and a thermostatic mixing valve in detail. (orig.)

Recent activities of association of shape memory alloys (ASMA) in Japan

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, J [ASMA, Yokohama (Japan); Yamauchi, K [TOKIN Corp., Sendai (Japan); Miyashita, T [Nishimatsu Construction Co., Ltd., Yamato (Japan); Ohkata, I [Kato Hatsujo Kaisha, Ltd., Yokohama (Japan); Narumi, S [Sogo Hatsujo Co., Ltd. (Japan); Suzuki, Y [Furukawa Electric Co. Ltd., Tokyo (Japan)

1995-12-01

The Association of Shape Memory Alloys(ASMA) was established in 1983 and systematic surveys on the Ni-Ti and Cu based SMAs were carried out until 1986. The ASMA is now reorganized as a private association. In this paper, we briefly introduce several SMA products of the member companies and present a couple of products, a static rock breaking system and a thermostatic mixing valve in detail. (orig.).

Shape-Memory-Alloy Actuator For Flight Controls

Science.gov (United States)

Barret, Chris

1995-01-01

Report proposes use of shape-memory-alloy actuators, instead of hydraulic actuators, for aerodynamic flight-control surfaces. Actuator made of shape-memory alloy converts thermal energy into mechanical work by changing shape as it makes transitions between martensitic and austenitic crystalline phase states of alloy. Because both hot exhaust gases and cryogenic propellant liquids available aboard launch rockets, shape-memory-alloy actuators exceptionally suited for use aboard such rockets.

Critical Speed Analysis of Fibre Reinforced Composite Rotor Embedded with Shape Memory Alloy Wires

OpenAIRE

Gupta, K.

2000-01-01

In the present analysis, the fundamental natural frequency of a Jeffcott and a two-mass rotor with fibre reinforced composite shaft embedded with shape memory alloy (SMA) wires is evaluated by Rayleigh's procedure. The flexibility of rotor supports is taken into account. The effect of three factors, either singly or in combination with each other, on rotor critical speed is studied. The three factors are: (i) increase in Young's modulus of SMA (NITINOL) wires when activated, (ii) tension in w...

Microplane modelling of shape memory alloys

International Nuclear Information System (INIS)

Kadkhodaei, M; Salimi, M; Rajapakse, R K N D; Mahzoon, M

2007-01-01

A three-dimensional (3D) constitutive model based on a statically constrained microplane theory with volumetric-deviatoric split is proposed for polycrystalline shape memory alloys (SMAs) under multiaxial loading paths. Microplane governing equations are 1D stress-strain relations for normal and shear stresses on each microplane, in which suitable relationships between the microscopic and macroscopic quantities are considered so that switching between elastic and inelastic local responses automatically occurs according to the macroscopic response of SMA without additional constraint. Shear stress on each microplane is expressed by the resultant shear component within the plane to overcome directional bias and to prevent the appearance of shear strain in a pure axial loading or axial strain in a pure shear loading while microplane formulations based on two shear directions may predict such impractical results. The behaviour of SMA under simple and complicated loadings has been studied. In nonproportional loading paths, the model shows interaction between stress components, as well as deviation from normality. Predicted results from the model are in good agreement with those of the existing theoretical and experimental investigations

Investigation of the Self-Healing Behavior of Sn-Bi Metal Matrix Composite Reinforced with NiTi Shape Memory Alloy Strips Under Flexural Loading

Science.gov (United States)

Poormir, Mohammad Amin; Khalili, Seyed Mohammad Reza; Eslami-Farsani, Reza

2018-06-01

Utilizing intelligent materials such as shape memory alloys as reinforcement in metal matrix composites is a novel method to mimic self-healing behavior. In this study, the bending behavior of a self-healing metal matrix composite made from Sn-13 wt.% Bi alloy as matrix and NiTi shape memory alloy (SMA) strips as reinforcement is investigated. Specimens were fabricated in different reinforcement vol.% (0.78, 1.55, 2.33) and in various pre-strains (0, 2, 6%) and were healed at three healing temperatures (170°C, 180°C, 190°C). Results showed that shape recovery was accomplished in all the specimens, but not all of them were able to withstand second loading after healing. Only specimens with 2.33 vol.% of SMA strips, 1.55 vol.% of SMA, and 6% pre-strain could endure bending force after healing, and they gained 35.31-51.83% of bending force self-healing efficiency.

A large-stroke shape memory alloy spring actuator using double-coil configuration

International Nuclear Information System (INIS)

Kim, Seung-Won; An, Sungmin; Cho, Kyu-Jin; Lee, Jong-Gu; Cho, Maenghyo

2015-01-01

One way to increase the range of motion of shape memory alloy (SMA) actuators is to create displacements of the SMA associated with not only the deformation from straining but also rigid-body motion from translation and rotation. Rigid-body motion allows the SMA to create larger displacements without exceeding the maximum recovery strain so that the SMA actuators can have a larger shape recovery ratio. To improve the linear actuation stroke of SMA wire actuators, a novel SMA spring actuator is proposed that employs a double-coil geometry that allows the displacement of the SMA to be mainly induced by rigid-body motion. A double-coil SMA spring actuator is fabricated by coiling an SMA wire twice so that the double coiling results in a reduction of the initial length of the double-coil SMA spring actuator. The effects of the geometric parameters on the actuation characteristic of a double-coil SMA spring actuator are verified numerically by finite element analysis and experimentally according to a parametric study of the geometric parameters. The displacement-to-force profile of the double-coil SMA spring actuator is nonlinear, and the spring stiffness changes when the actuator transforms its configuration from a double-coil shape to a single-coil shape. According to the results of the parametric study, increasing the wire diameter increases both primary and secondary coil stiffness, and increasing the primary inner coil diameter decreases both primary and secondary coil stiffness, whereas increasing the secondary inner coil diameter decreases only the secondary coil stiffness. The result shows that one of the double-coil SMA spring actuators with an initial length of 8 mm has a recovery ratio of 1250%, while the recovery ratio of the single-coil SMA spring actuator with the same geometric parameters is 432%. (paper)

Shape-retainment control using an antagonistic shape memory alloy system

Science.gov (United States)

Ikeda, T.; Sawamura, K.; Senba, A.; Tamayama, M.

2015-04-01

Since shape memory alloy (SMA) actuators can generate large force per unit weight, they are expected as one of the next generation actuators for aircraft. To keep a position of conventional control surfaces or morphing wings with SMA actuators, the SMA actuators must keep being heated, and the heating energy is not small. To save the energy, a new control method proposed for piezoelectric actuators utilizing hysteresis in deformation [Ikeda and Takahashi, Proc. SPIE 8689 (2013), 86890C] is applied to an antagonistic SMA system. By using the control method any position can be an equilibrium point within hysteresis of stress-strain diagrams. To confirm a feasibility of the control method, a fundamental experiment is performed. The SMA wires are heated by applying electric current to the wires. When a pulsed current is applied to the two SMA wires alternately, the equilibrium position changes between two positions alternately, and when a series of pulse whose amplitude increases gradually is applied to one SMA wire, the equilibrium position changes like a staircase. However, just after the pulse the position returns slightly, that is, overshoot takes place. To investigate such a behavior of the system, numerical simulation is also performed. The one-dimensional phase transformation model [Ikeda, Proc. SPIE 5757 (2005), 344-352] is used for a constitutive model of the SMA wires. The simulated result agrees with the experiment qualitatively, including the overshoot. By examining volume fraction of each phase, it is found that the overshoot is caused by that austenite phase transforms into stress-induced martensite phase during the cooling process after the pulse.

Spray forming of Cu–11.85Al–3.2Ni–3Mn (wt%) shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Cava, Régis D., E-mail: regis_cava@hotmail.com [Department of Materials Engineering, Federal University of São Carlos, São Carlos (Brazil); Bolfarini, Claudemiro; Kiminami, Cláudio S. [Department of Materials Engineering, Federal University of São Carlos, São Carlos (Brazil); Mazzer, Eric M. [Postgraduate Program in Materials Science and Engineering, Federal University of São Carlos (Brazil); Botta Filho, Walter J. [Department of Materials Engineering, Federal University of São Carlos, São Carlos (Brazil); Gargarella, Piter; Eckert, Jürger [IFW Dresden, Institute for Complex Materials, Dresden (Germany)

2014-12-05

Highlights: • We characterized a Cu-based shape memory alloy produced by spray forming. • The deposit presented equiaxial grains and monoclinic martensite β′ microstructure. • The deposit’s shape memory properties varied as a function of the cooling rates. • The results opened a new window in the manufacture of Cu shape memory materials. - Abstract: Cu-based shape memory alloys (SMA) in the range of Cu–(11.8–13.5)Al–(3.2–4)Ni–(2–3)Mn (wt%) exhibit high thermal and electrical conductivity, combine good mechanical properties with a pronounced shape memory effect, and are low cost (Dutkiewicz et al., 1999). Their processing requires high cooling rates to reduce grain size, prevent decomposition of the ß phase into equilibrium phases, and induce martensite transformation. In this investigation, Cu–11.85Al–3.2Ni–3Mn (wt%) shape memory alloy was processed by spray forming, a rapid solidification technique that involves cooling rates of 10{sup 1} to 10{sup 4} K/s, to determine the potential of producing deposits with adequate microstructure, homogeneity and porosity for the manufacture of SMA near net shape parts. To this end, 5.2 kg of alloy with nominal composition was atomized with nitrogen gas under a pressure of 0.5 MPa and a gas–metal ratio (GMR) of 1.93. The atomized material was deposited at 60 rpm on a rotating steel substrate positioned 350 mm below the gas nozzle. The microstructure of the deposit was characterized by optical and scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The deposit with an effective diameter of 240 mm and 75 mm height presented equiaxial grains with a martensite microstructure. Grain sizes varied from 25 μm in the lower region (contact with the steel substrate) to 160 μm in the upper region of the deposit. Measurements of the reverse martensite transformation temperature of the deposit in different regions revealed its strong influence on the grain size.

Towards High-Frequency Shape Memory Alloy Actuators Incorporating Liquid Metal Energy Circuits

Science.gov (United States)

Hartl, Darren; Mingear, Jacob; Bielefeldt, Brent; Rohmer, John; Zamarripa, Jessica; Elwany, Alaa

2017-12-01

Large shape memory alloy (SMA) actuators are currently limited to applications with low cyclic actuation frequency requirements due to their generally poor heat transfer rates. This limitation can be overcome through the use of distributed body heating methods such as induction heating or by accelerated cooling methods such as forced convection in internal cooling channels. In this work, a monolithic SMA beam actuator containing liquid gallium-indium alloy-filled channels is fabricated through additive manufacturing. These liquid metal channels enable a novel multi-physical thermal control system, allowing for increased heating and cooling rates to facilitate an increased cyclic actuation frequency. Liquid metal flowing in the channels performs the dual tasks of inductively heating the surrounding SMA material and then actively cooling the SMA via forced internal fluid convection. A coupled thermoelectric model, implemented in COMSOL, predicts a possible fivefold increase in the cyclic actuation frequency due to these increased thermal transfer rates when compared to conventional SMA forms having external heating coils and being externally cooled via forced convection. The first ever experimental prototype SMA actuator of this type is described and, even at much lower flow rates, is shown to exhibit a decrease in cooling time of 40.9%.

Effect of Substrate Roughness on Adhesion and Structural Properties of Ti-Ni Shape Memory Alloy Thin Film.

Science.gov (United States)

Kim, Donghwan; Lee, Hyunsuk; Bae, Joohyeon; Jeong, Hyomin; Choi, Byeongkeun; Nam, Taehyun; Noh, Jungpil

2018-09-01

Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

Characterization and modeling of three-dimensional self-healing shape memory alloy-reinforced metal-matrix composites

Energy Technology Data Exchange (ETDEWEB)

Manuel, Michele Viola [University of Florida, Gainesville; Zhu, Pingping [Northwestern University, Evanston; Newman, John A. [NASA Langely Research Center (LaRC), Virginia; Wright, M Clara [NASA Kennedy Space Center, FL; Brinson, L Catherine [Northwestern University, Evanston; Kesler, Michael S. [ORNL

2016-09-10

In this paper, three-dimensional metal-matrix composites (MMCs) reinforced by shape memory alloy (SMA) wires are modeled and simulated, by adopting an SMA constitutive model accounting for elastic deformation, phase transformation and plastic behavior. A modeling method to create composites with pre-strained SMA wires is also proposed to improve the self-healing ability. Experimental validation is provided with a composite under three-point bending. This modeling method is applied in a series of finite element simulations to investigate the self-healing effects in pre-cracked composites, especially the role of the SMA reinforcement, the softening property of the matrix, and the effect of pre-strain in the SMA. The results demonstrate that SMA reinforcements provide stronger shape recovery ability than other, non-transforming materials. The softening property of the metallic matrix and the pre-strain in SMA are also beneficial to help crack closure and healing. This modeling approach can serve as an efficient tool to design SMA-reinforced MMCs with optimal self-healing properties that have potential applications in components needing a high level of reliability.

Electrochemical Properties of Ni 47 Ti 49 Co 4 Shape Memory Alloy in Artificial Urine for Urological Implant

KAUST Repository

Ahmed, Rasha A.

2015-09-02

© 2015 American Chemical Society. The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications.

Electrochemical Properties of Ni 47 Ti 49 Co 4 Shape Memory Alloy in Artificial Urine for Urological Implant

KAUST Repository

Ahmed, Rasha A.

2015-01-01

© 2015 American Chemical Society. The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications.

Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys

Directory of Open Access Journals (Sweden)

Safaa N. Saud

2017-01-01

Full Text Available The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery, and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film.

Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys.

Science.gov (United States)

Saud, Safaa N; Hamzah, E; Bakhsheshi-Rad, H R; Abubakar, T

2017-01-01

The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery), and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film.

Nonlinear Analysis of Actuation Performance of Shape Memory Alloy Composite Film Based on Silicon Substrate

Directory of Open Access Journals (Sweden)

Shuangshuang Sun

2014-01-01

Full Text Available The mechanical model of the shape memory alloy (SMA composite film with silicon (Si substrate was established by the method of mechanics of composite materials. The coupled action between the SMA film and Si substrate under thermal loads was analyzed by combining static equilibrium equations, geometric equations, and physical equations. The material nonlinearity of SMA and the geometric nonlinearity of bending deformation were both considered. By simulating and analyzing the actuation performance of the SMA composite film during one cooling-heating thermal cycle, it is found that the final cooling temperature, boundary condition, and the thickness of SMA film have significant effects on the actuation performance of the SMA composite film. Besides, the maximum deflection of the SMA composite film is affected obviously by the geometric nonlinearity of bending deformation when the thickness of SMA film is very large.

Development of a Nano-Satellite Micro-Coupling Mechanism with Characterization of a Shape Memory Alloy Interference Joint

Science.gov (United States)

2010-12-01

for the softer martensitic phase was greater than that of the harder austenite phase [8]. When comparing NiTi to stainless steel 304 for resistance...interference joint, consisting of a detwinned martensitic NiTi SMA ring and stainless steel hub, could obtain sufficient axial coupling strength to...titanium (NiTi), shape memory alloy (SMA) cylindrical ring that is press-fit, in its detwinned martensitic phase, into a steel bushing, creating an

Effects of annealing and deforming temperature on microstructure and deformation characteristics of Ti-Ni-V shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

He Zhirong, E-mail: hezhirong01@163.com [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China); Liu Manqian [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China)

2012-07-25

Highlights: Black-Right-Pointing-Pointer The deformation behaviors of annealed Ti-50.8Ni-0.5V shape memory alloy (SMA) were given. Black-Right-Pointing-Pointer The effect of annealing temperature on microstructure and deformation characteristics of Ti-50.8Ni-0.5V SMA was shown. Black-Right-Pointing-Pointer The effect of deforming temperature on deformation characteristics of Ti-50.8Ni-0.5V SMA was given. - Abstract: Effects of annealing temperature T{sub an} and deforming temperature T{sub d} on microstructure and deformation characteristics of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing T{sub an}, the microstructure of Ti-50.8Ni-0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 Degree-Sign C; the critical stress for stress-induced martensite {sigma}{sub M} of the alloy decreases first and then increases, and the minimum value 382 MPa is got at T{sub an} = 450 Degree-Sign C; the residual strain {epsilon}{sub R} first increases, then decreases, and then increases, and its maximum value 2.5% is reached at T{sub an} = 450 Degree-Sign C. With increasing T{sub d}, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME {yields} SE transformation temperature was affected by T{sub an}; the {sigma}{sub M} of the alloy increases linearly; the {epsilon}{sub R} of the alloy annealed at 350-600 Degree-Sign C decreases first and then tends to constant, while that of the alloy annealed at 650 Degree-Sign C and 700 Degree-Sign C decreases first and then increases. To get an excellent SE at room temperature for Ti-50.8Ni-0.5V alloy, T{sub an} should be 500-600 Degree-Sign C.

Effect of thermal cycling on the transformation temperature ranges of a Ni-Ti shape memory alloy

International Nuclear Information System (INIS)

Paula, A.S.; Canejo, J.P.H.G.; Martins, R.M.S.; Braz Fernandes, F.M.

2003-01-01

Shape memory alloys (SMA) represents a class of metallic materials that has the capability of recovering a previously defined initial shape when subject to an adequate thermomechanical treatment. The present work aims to study the influence of thermal cycles on the transition temperatures of a Ni-Ti alloy. In this system, small variations around the equiatomic composition give rise to significant transformation temperature variations ranging from 173 to 373 K. SMA usually presents the shape memory effect after an annealing treatment at ca. 973 K. The optimisation of the thermomechanical treatment will allow to 'tune' the material to different transformation temperature ranges from the same starting material, just by changing the processing conditions. Differential scanning calorimeter (DSC) and in situ high-temperature X-ray diffraction (XRD) have been used to identify the transformation temperatures and the phases that are present after different thermal cycles. The results concerning a series of thermal cycles with different heating and cooling rates (from 1.67x10 -2 to 1.25x10 -1 K/s) and different holding temperatures (from 473 to 1033 K) are presented

Indirect intelligent sliding mode control of a shape memory alloy actuated flexible beam using hysteretic recurrent neural networks

International Nuclear Information System (INIS)

Hannen, Jennifer C; Buckner, Gregory D; Crews, John H

2012-01-01

This paper introduces an indirect intelligent sliding mode controller (IISMC) for shape memory alloy (SMA) actuators, specifically a flexible beam deflected by a single offset SMA tendon. The controller manipulates applied voltage, which alters SMA tendon temperature to track reference bending angles. A hysteretic recurrent neural network (HRNN) captures the nonlinear, hysteretic relationship between SMA temperature and bending angle. The variable structure control strategy provides robustness to model uncertainties and parameter variations, while effectively compensating for system nonlinearities, achieving superior tracking compared to an optimized PI controller. (paper)

Modeling and Bayesian parameter estimation for shape memory alloy bending actuators

Science.gov (United States)

Crews, John H.; Smith, Ralph C.

2012-04-01

In this paper, we employ a homogenized energy model (HEM) for shape memory alloy (SMA) bending actuators. Additionally, we utilize a Bayesian method for quantifying parameter uncertainty. The system consists of a SMA wire attached to a flexible beam. As the actuator is heated, the beam bends, providing endoscopic motion. The model parameters are fit to experimental data using an ordinary least-squares approach. The uncertainty in the fit model parameters is then quantified using Markov Chain Monte Carlo (MCMC) methods. The MCMC algorithm provides bounds on the parameters, which will ultimately be used in robust control algorithms. One purpose of the paper is to test the feasibility of the Random Walk Metropolis algorithm, the MCMC method used here.

Contribution of Shape Memory Alloys Elements in Designing Underwater Smart Structures

Directory of Open Access Journals (Sweden)

Daniel Amariei

2007-10-01

Full Text Available Shape memory alloys (SMA have generated a lot of new ideas in engineering. Application is however so far limited to clamps and springs. With respect to smart structures sensing as well as control has to be included. While sensing looks to be relatively feasible control is the big challenge. This paper describes some related a smart structure idea using SMAs and discusses the challenges which need to be solved before these ideas can be realised.

Shape memory alloy wire-based smart natural rubber bearing

International Nuclear Information System (INIS)

Hedayati Dezfuli, F; Shahria Alam, M

2013-01-01

In this study, two types of smart elastomeric bearings are presented using shape memory alloy (SMA) wires. Due to the unique characteristics of SMAs, such as the superelastic effect and the recentering capability, the residual deformation in SMA-based natural rubber bearings (SMA-NRBs) is significantly reduced whereas the energy dissipation capacity is increased. Two different configurations of SMA wires incorporated in elastomeric bearings are considered. The effect of several parameters, including the shear strain amplitude, the type of SMA, the aspect ratio of the base isolator, the thickness of SMA wire, and the amount of pre-strain in the wires on the performance of SMA-NRBs is investigated. Rubber bearings are composed of natural rubber layers bonded to steel shims as reinforcement. Results show that ferrous SMA wire, FeNiCuAlTaB, with 13.5% superelastic strain and a very low austenite finish temperature (−62 °C), is the best candidate to be used in SMA-NRBs subjected to high shear strain amplitudes. In terms of the lateral flexibility and wire strain level, the smart rubber bearing with a cross configuration of SMA wires is more efficient. Moreover, the cross configuration can be implemented in high-aspect-ratio elastomeric bearings since the strain induced in the wire does not exceed the superelastic range. When cross SMA wires with 2% pre-strain are used in a smart NRB, the dissipated energy is increased by 74% and the residual deformation is decreased by 15%. (paper)

Intelligent design optimization of a shape-memory-alloy-actuated reconfigurable wing

Science.gov (United States)

Lagoudas, Dimitris C.; Strelec, Justin K.; Yen, John; Khan, Mohammad A.

2000-06-01

The unique thermal and mechanical properties offered by shape memory alloys (SMAs) present exciting possibilities in the field of aerospace engineering. When properly trained, SMA wires act as linear actuators by contracting when heated and returning to their original shape when cooled. It has been shown experimentally that the overall shape of an airfoil can be altered by activating several attached SMA wire actuators. This shape-change can effectively increase the efficiency of a wing in flight at several different flow regimes. To determine the necessary placement of these wire actuators within the wing, an optimization method that incorporates a fully-coupled structural, thermal, and aerodynamic analysis has been utilized. Due to the complexity of the fully-coupled analysis, intelligent optimization methods such as genetic algorithms have been used to efficiently converge to an optimal solution. The genetic algorithm used in this case is a hybrid version with global search and optimization capabilities augmented by the simplex method as a local search technique. For the reconfigurable wing, each chromosome represents a realizable airfoil configuration and its genes are the SMA actuators, described by their location and maximum transformation strain. The genetic algorithm has been used to optimize this design problem to maximize the lift-to-drag ratio for a reconfigured airfoil shape.

Shape memory alloy resistance behaviour at high altitude for feedback control

Science.gov (United States)

Ng, W. T.; Sedan, M. F.; Abdullah, E. J.; Azrad, S.; Harithuddin, A. S. M.

2017-12-01

Many recent aerospace technologies are using smart actuators to reduce the system's complexity and increase its reliability. One such actuator is shape memory alloy (SMA) actuator, which is lightweight, produces high force and large deflection. However, some disadvantages in using SMA actuators have been identified and they include nonlinear response of the strain to input current, hysteresis characteristic that results in inaccurate control and less than optimum system performance, high operating temperatures, slow response and also high requirement of electrical power to obtain the desired actuation forces. It is still unknown if the SMA actuators can perform effectively at high altitude with low surrounding temperature. The work presented here covers the preliminary process of verifying the feasibility of using resistance as feedback control at high altitude for aerospace applications. Temperature and resistance of SMA actuator at high altitude is investigated by conducting an experiment onboard a high altitude balloon. The results from the high altitude experiment indicate that the resistance or voltage drop of the SMA wire is not significantly affected by the low surrounding temperature at high altitude as compared to the temperature of SMA. Resistance feedback control for SMA actuators may be suitable for aerospace applications.

Rapid prototyping prosthetic hand acting by a low-cost shape-memory-alloy actuator.

Science.gov (United States)

Soriano-Heras, Enrique; Blaya-Haro, Fernando; Molino, Carlos; de Agustín Del Burgo, José María

2018-06-01

The purpose of this article is to develop a new concept of modular and operative prosthetic hand based on rapid prototyping and a novel shape-memory-alloy (SMA) actuator, thus minimizing the manufacturing costs. An underactuated mechanism was needed for the design of the prosthesis to use only one input source. Taking into account the state of the art, an underactuated mechanism prosthetic hand was chosen so as to implement the modifications required for including the external SMA actuator. A modular design of a new prosthesis was developed which incorporated a novel SMA actuator for the index finger movement. The primary objective of the prosthesis is achieved, obtaining a modular and functional low-cost prosthesis based on additive manufacturing executed by a novel SMA actuator. The external SMA actuator provides a modular system which allows implementing it in different systems. This paper combines rapid prototyping and a novel SMA actuator to develop a new concept of modular and operative low-cost prosthetic hand.

A Novel Implementation of a Flexible Robotic Fin Actuated by Shape Memory Alloy

Institute of Scientific and Technical Information of China (English)

Qin Yan; Lei Wang; Bo Liu; Jie Yang; Shiwu Zhang

2012-01-01

In this paper,study of a novel flexible robotic-fin actuated by Shape Memory Alloy (SMA) is presented.The developed robotic fin is capable of implementing various 3-Dimensional (3D) motions,which plays an important role in robot propulsion and maneuverability.Firstly,the morphological and mechanics parameters of a real pectoral fin from a carp are investigated.Secondly,a detailed design of the flexible pectoral fin driven by SMA is presented according to the previous morphological and mechanics analyses.Thirdly,a simplified theoretical model on the SMA fin plate is derived.The thermodynamics of the SMA plate and the relationship between curvature and phase transformation are analyzed.Finally,several simulations and model experiments are conducted according to the previous analyses.The results of the experiments are useful for the control of the robotic fin.The experimental results reveal that the SMA actuated fin ray has a good actuating performance.

Rotor-bearing system integrated with shape memory alloy springs for ensuring adaptable dynamics and damping enhancement-Theory and experiment

DEFF Research Database (Denmark)

Enemark, Søren; Santos, Ilmar F.

2016-01-01

nonlinear coupled dynamics of the rotor-bearing system. The nonlinear forces from the thermomechanical shape memory alloy springs and from the passive magnetic bearings are coupled to the rotor and bearing housing dynamics. The equations of motion describing rotor tilt and bearing housing lateral motion......Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic...

A new method to determinate phase transformation in shape memory alloys: infrared thermography

International Nuclear Information System (INIS)

Bubulinca, C.; Balandraud, X.; Grediac, M.; Plaiasu, G. A.; Abrudeanu, M.; Stanciu, S.

2013-01-01

In this article it is presented a shape memory alloy case, based on copper, namely Cu-Zn-Al, which is subjected to periodic mechanical traction. Traction is performed in conditions of normal temperature and pressure. The purpose of this article it is to study stress induced phase transformation. All tests are performed in same conditions. Transformation on which is based this effect occurs in two ways: by applying a stress or temperature variation. In this article it is studied stress induced phase transformation. The method to analyze the microstructure of an shape memory alloy (SMA) is relatively new and it is based on tracking the evolution of temperature. After thermal analysis we can decide in which state is one alloy without any other supplier measures (differential scanning calorimetric or electrical resistivity). If our specimen will producing thermal energy when specimen is tensile he is austenitic. If absorbing heat during the first deformation is in martensitic state. (authors)

Microstructural modeling of fatigue fracture of shape memory alloys at thermomechanical cyclic loading

Science.gov (United States)

Belyaev, Fedor S.; Evard, Margarita E.; Volkov, Aleksandr E.

2018-05-01

A microstructural model of shape memory alloys (SMA) describing their deformation and fatigue fracture is presented. A new criterion of fracture has been developed which takes into account the effect of hydrostatic pressure, deformation defects and material damage. It is shown that the model can describe the fatigue fracture of SMA under various thermomechanical cycling regimes. Results of calculating the number of cycles to failure at thermocycling under a constant stress, at symmetric two-sided cyclic deformation, at straining-unloading cycles, at cycling in the regime of the thermodynamic cycles of a SMA working body in the hard (strain controlled) and soft (stress controlled) working cycles, is studied. Results of calculating the number of cycles to failure are presented for different parameters of these cycles.

Shape memory effect alloys

International Nuclear Information System (INIS)

Koshimizu, S.

1992-01-01

Although the pseudo- or super-elasticity phenomena and the shape memory effect were known since the 1940's, the enormous curiosity and the great interest to their practical applications emerged with the development of the NITINOL alloy (Nickel-Titanium Naval Ordance Laboratory) by the NASA during the 1960's. This fact marked the appearance of a new class of materials, popularly known as shape memory effect alloys (SMEA). The objective of this work is to present a state-of-the-art of the development and applications for the SMEA. (E.O.)

Applications of shape memory alloys in Japan

International Nuclear Information System (INIS)

Asai, M.; Suzuki, Y.

2000-01-01

In Japan, a first application of shape memory TiNi alloy was a moving flap in an air-conditioner which was developed as sensing function of shape memory alloy at Matsushista Electric Industrial Co. Then, shape memory utilized in a coffee maker, an electric rice-cooker, a thermal mixing valve and etc. were commercialized in Japan. And brassiere wires, a guide wire for medical treatment, an antenna for portable telephone and others were commercialized utilizing superelasticity. At the same time with these commercial products, there was not only progress in fabrication technology to effect accurate transformation temperature, but also the discovery of small hysteresis alloy such as R-phase or TiNiCu alloy and low transformation temperature alloy such as TiNiFe, TiNiV and TiNiCo alloys. Therefore the shape memory alloy market has expanded widely to electric appliances, automobile, residence, medical care and other field today. (orig.)

A novel smart rotor support with shape memory alloy metal rubber for high temperatures and variable amplitude vibrations

International Nuclear Information System (INIS)

Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Hong, Jie; Scarpa, Fabrizio; Liu, Baolong

2014-01-01

The work describes the design, manufacturing and testing of a smart rotor support with shape memory alloy metal rubber (SMA-MR) elements, able to provide variable stiffness and damping characteristics with temperature, motion amplitude and excitation frequency. Differences in damping behavior and nonlinear stiffness between SMA-MR and more traditional metal rubber supports are discussed. The mechanical performance shown by the prototype demonstrates the feasibility of using the SMA-MR concept for active vibration control in rotordynamics, in particular at high temperatures and large amplitude vibrations. (paper)

High-strength shape memory steels alloyed with nitrogen

International Nuclear Information System (INIS)

Ullakko, K.; Jakovenko, P.T.; Gavriljuk, V.G.

1996-01-01

Since shape memory effect in Fe-Mn-Si systems was observed, increasing attention has been paid to iron based shape memory alloys due to their great technological potential. Properties of Fe-Mn-Si shape memory alloys have been improved by alloying with Cr, Ni, Co and C. A significant improvement on shape memory, mechanical and corrosion properties is attained by introducing nitrogen in Fe-Mn-Si based systems. By increasing the nitrogen content, strength of the matrix increases and the stacking fault energy decreases, which promote the formation of stress induced martensite and decrease permanent slip. The present authors have shown that nitrogen alloyed shape memory steels exhibit recoverable strains of 2.5--4.2% and recovery stresses of 330 MPa. In some cases, stresses over 700 MPa were attained at room temperature after cooling a constrained sample. Yield strengths of these steels can be as high as 1,100 MPa and tensile strengths over 1,500 MPa with elongations of 30%. In the present study, effect of nitrogen alloying on shape memory and mechanical properties of Fe-Mn-Si, Fe-Mn-Si-Cr-Ni and Fe-Mn-Cr-Ni-V alloys is studied. Nitrogen alloying is shown to exhibit a beneficial effect on shape memory properties and strength of these steels

A jumping shape memory alloy under heat.

Science.gov (United States)

Yang, Shuiyuan; Omori, Toshihiro; Wang, Cuiping; Liu, Yong; Nagasako, Makoto; Ruan, Jingjing; Kainuma, Ryosuke; Ishida, Kiyohito; Liu, Xingjun

2016-02-16

Shape memory alloys are typical temperature-sensitive metallic functional materials due to superelasticity and shape recovery characteristics. The conventional shape memory effect involves the formation and deformation of thermally induced martensite and its reverse transformation. The shape recovery process usually takes place over a temperature range, showing relatively low temperature-sensitivity. Here we report novel Cu-Al-Fe-Mn shape memory alloys. Their stress-strain and shape recovery behaviors are clearly different from the conventional shape memory alloys. In this study, although the Cu-12.2Al-4.3Fe-6.6Mn and Cu-12.9Al-3.8Fe-5.6Mn alloys possess predominantly L2(1) parent before deformation, the 2H martensite stress-induced from L2(1) parent could be retained after unloading. Furthermore, their shape recovery response is extremely temperature-sensitive, in which a giant residual strain of about 9% recovers instantly and completely during heating. At the same time, the phenomenon of the jumping of the sample occurs. It is originated from the instantaneous completion of the reverse transformation of the stabilized 2H martensite. This novel Cu-Al-Fe-Mn shape memory alloys have great potentials as new temperature-sensitive functional materials.

Effect of cold rolling on fatigue crack propagation of TiNi/A16061 shape memory composite

International Nuclear Information System (INIS)

Lee, Jin Kyung; Lee, Sang Pill; Park, Young Chul; Lee, Kyu Chang; Cho, Youn Ho; Lee, Joon Hyun

2005-01-01

TiNi alloy fiber was used to recover the original shape of materials using its shape memory effect. The shape memory alloy plays an important role within the metal matrix composite. The shape memory alloy can control the crack propagation in metal matrix composite, and improve the tensile strength of the composite. In this study, TiNi/A16061 Shape Memory Alloy(SMA) composite was fabricated by hot press method, and pressed by a roller for its strength improvement. The four kinds of specimens were fabricated with 0%, 3.2%, 5.2% and 7% volume fraction of TiNi alloy fiber, respectively. A fatigue test has performed to evaluate the crack initiation and propagation for the TiNi/A16061 SMA composite fabricated by this method. In order to study the shape memory effect of the TiNi alloy fiber, the test has also done under both conditions of the room temperature and high temperature. The relationship between the crack growth rate and the stress intensity factor was clarified for the composite, and the cold rolling effect was also studied

A two-degrees-of-freedom miniature manipulator actuated by antagonistic shape memory alloys

International Nuclear Information System (INIS)

Lai, Chih-Ming; Chu, Cheng-Yu; Lan, Chao-Chieh

2013-01-01

This paper presents a miniature manipulator that can provide rotations around two perpendicularly intersecting axes. Each axis is actuated by a pair of shape memory alloy (SMA) wires. SMA wire actuators are known for their large energy density and ease of actuation. These advantages make them ideal for applications that have stringent size and weight constraints. SMA actuators can be temperature-controlled to contract and relax like muscles. When correctly designed, antagonistic SMA actuators have a faster response and larger range of motion than bias-type SMA actuators. This paper proposes an antagonistic actuation model to determine the manipulator parameters that are required to generate sufficient workspace. Effects of SMA prestrain and spring stiffness on the manipulator are investigated. Taking advantage of proper prestrain, the actuator size can be made much smaller while maintaining the same motion. The use of springs in series with SMA can effectively reduce actuator stress. A controller and an anti-slack algorithm are developed to ensure fast and accurate motion. Speed, stress, and loading experiments are conducted to demonstrate the performance of the manipulator. (paper)

Electromagnetic heating of a shape memory alloy translator

Science.gov (United States)

Giroux, E.-A.; Maglione, M.; Gueldry, A.; Mantoux, J.-L.

1996-03-01

The active part of a linear translator is a shape memory alloy (SMA) made of nickel and titanium (NiTi) wire which is to be thermally cycled. We have achieved heating using electromagnetic radiation with a magnetic sheath and low-frequency waves at 8 kHz and without magnetic sheath and radio frequency waves at 28 MHz. The heating is equivalent for these two arrangements. In vitro experiments have been confirmed by computer simulations of the radiation distribution within the implant. We thus show that electromagnetic radiation could specifically heat a NiTi wire inside a stainless steel tube without heating the tube. An application could be a femoral prosthesis for the lengthening of the bone.

Low-Pressure and Low-Temperature Hydriding-Pulverization-Dehydriding Method for Producing Shape Memory Alloy Powders

Science.gov (United States)

Murguia, Silvia Briseño; Clauser, Arielle; Dunn, Heather; Fisher, Wendy; Snir, Yoav; Brennan, Raymond E.; Young, Marcus L.

2018-04-01

Shape memory alloys (SMAs) are of high interest as active, adaptive "smart" materials for applications such as sensors and actuators due to their unique properties, including the shape memory effect and pseudoelasticity. Binary NiTi SMAs have shown the most desirable properties, and consequently have generated the most commercial success. A major challenge for SMAs, in particular, is their well-known compositional sensitivity. Therefore, it is critical to control the powder composition and morphology. In this study, a low-pressure, low-temperature hydriding-pulverization-dehydriding method for preparing well-controlled compositions, size, and size distributions of SMA powders from wires is presented. Starting with three different diameters of as-drawn martensitic NiTi SMA wires, pre-alloyed NiTi powders of various well-controlled sizes are produced by hydrogen charging the wires in a heated H3PO4 solution. After hydrogen charging for different charging times, the wires are pulverized and subsequently dehydrided. The wires and the resulting powders are characterized using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. The relationship between the wire diameter and powder size is investigated as a function of hydrogen charging time. The rate of diameter reduction after hydrogen charging of wire is also examined. Finally, the recovery behavior due to the shape memory effect is investigated after dehydriding.

Grippers for the micro assembly containing shape memory actuators and sensors

International Nuclear Information System (INIS)

Mertmann, M.; Hornbogen, E.

1997-01-01

Shape memory alloys (SMA) show a high ratio of work capacity per material volume. This makes the application of SMA especially useful in micron-sized systems. The development of robotic grippers is one important prerequisite for the successful automation of the assembly of micro systems. Therefore the SMA may also play a role, for example, as actuators in micron-sized grippers. This paper presents the development of micron-sized grippers. Due to a special relation between the electrical resistance and the shape change of a NiTi-wire the actuator may also be used simultaneously as a sensor. Besides these functional properties a superelastic SMA may be used for structural purposes, i.e. as solid-state flexure hinges. The sensoric features of binary and ternary NiTi-based alloys are investigated using different Ti 50 Ni 50-x Cu x alloys with 0 50 Ni 50-x Cu x alloys and their influence on the functional properties are compared. The effect of the TMT on the amount and the stability of the shape memory effect has to be taken into account if the optimum alloy and condition for the use in grippers for micro assembly are investigated. The function and the properties of the developped gripping devices are demonstrated by prototypes. (orig.)

Modeling and development of a twisting wing using inductively heated shape memory alloy actuators

Science.gov (United States)

Saunders, Robert N.; Hartl, Darren J.; Boyd, James G.; Lagoudas, Dimitris C.

2015-04-01

Wing twisting has been shown to improve aircraft flight performance. The potential benefits of a twisting wing are often outweighed by the mass of the system required to twist the wing. Shape memory alloy (SMA) actuators repeatedly demonstrate abilities and properties that are ideal for aerospace actuation systems. Recent advances have shown an SMA torsional actuator that can be manufactured and trained with the ability to generate large twisting deformations under substantial loading. The primary disadvantage of implementing large SMA actuators has been their slow actuation time compared to conventional actuators. However, inductive heating of an SMA actuator allows it to generate a full actuation cycle in just seconds rather than minutes while still . The aim of this work is to demonstrate an experimental wing being twisted to approximately 10 degrees by using an inductively heated SMA torsional actuator. This study also considers a 3-D electromagnetic thermo-mechanical model of the SMA-wing system and compare these results to experiments to demonstrate modeling capabilities.

Modeling of Stress Development During Thermal Damage Healing in Fiber-reinforced Composite Materials Containing Embedded Shape Memory Alloy Wires

NARCIS (Netherlands)

Bor, Teunis Cornelis; Warnet, Laurent; Akkerman, Remko; de Boer, Andries

2010-01-01

Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment. The composite material

Thermal responses of shape memory alloy artificial anal sphincters

Science.gov (United States)

Luo, Yun; Takagi, Toshiyuki; Matsuzawa, Kenichi

2003-08-01

This paper presents a numerical investigation of the thermal behavior of an artificial anal sphincter using shape memory alloys (SMAs) proposed by the authors. The SMA artificial anal sphincter has the function of occlusion at body temperature and can be opened with a thermal transformation induced deformation of SMAs to solve the problem of severe fecal incontinence. The investigation of its thermal behavior is of great importance in terms of practical use in living bodies as a prosthesis. In this work, a previously proposed phenomenological model was applied to simulate the thermal responses of SMA plates that had undergone thermally induced transformation. The numerical approach for considering the thermal interaction between the prosthesis and surrounding tissues was discussed based on the classical bio-heat equation. Numerical predictions on both in vitro and in vivo cases were verified by experiments with acceptable agreements. The thermal responses of the SMA artificial anal sphincter were discussed based on the simulation results, with the values of the applied power and the geometric configuration of thermal insulation as parameters. The results obtained in the present work provided a framework for the further design of SMA artificial sphincters to meet demands from the viewpoint of thermal compatibility as prostheses.

Nonlinear tension-bending deformation of a shape memory alloy rod

International Nuclear Information System (INIS)

Shang, Zejin; Wang, Zhongmin

2012-01-01

Based on the measured shape memory alloy (SMA) stress–strain curve and the nonlinear large deformation theory of extensible beams (or rods), the first-order nonlinear governing equations of a SMA cantilever straight rod are established. They consist of a boundary-value problem of ordinary differential equations with a strong nonlinearity, in which seven unknown functions are contained and the arc length of the deformed axis is considered as one of the basic unknown functions. The shooting method combining with the Newton–Raphson iteration method is applied to solve the equations numerically. For a SMA cantilever rod subjected to a transverse uniformly distributed force, the deformation characteristics curves, the maximum strain and the maximum stress distribution curves along the longitudinal direction of rod, and the relation curves between deformation characteristic parameters and transverse uniformly force under different slenderness ratios are obtained. The effects of material nonlinearity, geometrical nonlinearity and slenderness ratio on the tension-bending deformation of the SMA cantilever rod are investigated. The numerical simulation results are in good agreement with the experimental data from the literature, verifying the soundness of the entire numerical simulation scheme. (paper)

Evaluating the ductility characteristics of self-centering buckling-restrained shape memory alloy braces

Science.gov (United States)

Abou-Elfath, Hamdy

2017-05-01

Recently, self-centering earthquake resistant systems have attracted attention because of their promising potential in controlling the residual drifts and reducing repair costs after earthquake events. Considerable portion of self-centering research is based on using short-segment superelastic shape memory alloy (SMA) braces as strengthening technique because of the lower modulus of elasticity of SMA in comparison with that of steel. The goal of this study is to investigate the ductility characteristics of these newly proposed short-segment SMA braces to evaluate their safety levels against fracture failures under earthquake loading. This goal has been achieved by selecting an appropriate seismic performance criterion for steel frames equipped with SMA braces, defining the level of strain capacity of SMA and calculating the strain demands in the SMA braces by conducting a series of pushover and earthquake time history analyzes on typical frame structure. The results obtained in this study indicated the inability of short-segment SMA designs to provide adequate ductility to the lateral resistant systems. An alternative approach is introduced by using hybrid steel-SMA braces that are capable of controlling the residual drifts and providing the structure with adequate lateral stiffness.

A Constitutive Model for Superelastic Shape Memory Alloys Considering the Influence of Strain Rate

Directory of Open Access Journals (Sweden)

Hui Qian

2013-01-01

Full Text Available Shape memory alloys (SMAs are a relatively new class of functional materials, exhibiting special thermomechanical behaviors, such as shape memory effect and superelasticity, which enable their applications in seismic engineering as energy dissipation devices. This paper investigates the properties of superelastic NiTi shape memory alloys, emphasizing the influence of strain rate on superelastic behavior under various strain amplitudes by cyclic tensile tests. A novel constitutive equation based on Graesser and Cozzarelli’s model is proposed to describe the strain-rate-dependent hysteretic behavior of superelastic SMAs at different strain levels. A stress variable including the influence of strain rate is introduced into Graesser and Cozzarelli’s model. To verify the effectiveness of the proposed constitutive equation, experiments on superelastic NiTi wires with different strain rates and strain levels are conducted. Numerical simulation results based on the proposed constitutive equation and experimental results are in good agreement. The findings in this paper will assist the future design of superelastic SMA-based energy dissipation devices for seismic protection of structures.

Thermomechanical macroscopic model of shape memory alloys

International Nuclear Information System (INIS)

Volkov, A.E.; Sakharov, V.Yu.

2003-01-01

The phenomenological macroscopic model of the mechanical behaviour of the titanium nickelide-type shape memory alloys is proposed. The model contains as a parameter the average phase shear deformation accompanying the martensite formation. It makes i possible to describe correctly a number of functional properties of the shape memory alloys, in particular, the pseudoelasticity ferroplasticity, plasticity transformation and shape memory effects in the stressed and unstressed samples [ru

Lag-Lead Compensator for Shape Memory Alloy in Gripping Manipulation

Directory of Open Access Journals (Sweden)

Made Andik Setiawan

2010-12-01

Full Text Available Shape Memory Alloy (SMA is emerging actuator for micro and nano application, on the other hand the developing controller in such area needs much further considerations.This paper is to present the evaluation of close-loop controller responses of the TiNi SMA spring based gripper by introduced lag, lead and lag-lead compensator. A SMA spring has a diameter of 50 mm wire and 350 gram hanging mass. Driving the SMA actuator is used pulse width modulation (PWM signal and responses tested by varying frequencies and duty-cycles. The implemented frequencies in this study are 12, 25, 125, 250 and 1150 Hz. Lab-View and DAQ-Card is used as a controller, interfacer and data recorder of the system. The gripper fabricated consists of two fingers and the total angular displacement of the gripper is 300. The experimental result of the SMA open-loop response are presented and discussed. For advanced application, the close-loop controller is implemented and studied. The close-loop controllers employed are lag, lead and lag-lead compensator. The SMA response indicated that the rise-time and the steady-state error of the cloop-loop are shorter and lower than open-loop controller. The tuning, response and program of the lag, lead and lag-lead compensator are presented and discussed in this paper.

Shape memory alloy-based small crawling robots inspired by C. elegans

Energy Technology Data Exchange (ETDEWEB)

Yuk, Hyunwoo; Kim, Daeyeon; Shin, Jennifer H [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Lee, Honggu; Jo, Sungho, E-mail: shjo@kaist.ac.kr, E-mail: j_shin@kaist.ac.kr [Department of Computer Science, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of)

2011-12-15

Inspired by its simple musculature, actuation and motion mechanisms, we have developed a small crawling robot that closely mimics the model organism of our choice: Caenorhabditis elegans. A thermal shape memory alloy (SMA) was selected as an actuator due to the similarities of its properties to C. elegans muscles. Based on the anatomy of C. elegans, a 12-unit robot was designed to generate a sinusoidal undulating motion. Each body unit consisting of a pair of SMA actuators is serially connected by rigid links with an embedded motion control circuit. A simple binary operation-based motion control mechanism was implemented using a microcontroller. The assembled robot can execute C. elegans-like motion with a 0.17 Hz undulation frequency. Its motion is comparable to that of a real worm.

Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

Science.gov (United States)

Colić, Miodrag; Rudolf, Rebeka; Stamenković, Dragoslav; Anzel, Ivan; Vucević, Dragana; Jenko, Monika; Lazić, Vojkan; Lojen, Gorazd

2010-01-01

Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

A Shape Memory Alloy Application for Compact Unmanned Aerial Vehicles

Directory of Open Access Journals (Sweden)

Salvatore Ameduri

2016-05-01

Full Text Available Shape memory alloys materials, SMA, offer several advantages that designers can rely on such as the possibility of transmitting large forces and deformations, compactness, and the intrinsic capability to absorb loads. Their use as monolithic actuators, moreover, can lead to potential simplifications of the system, through a reduction of number of parts and the removal of many free play gaps among mechanics. For these reasons, technological aerospace research is focusing on this kind of technology more and more, even though fatigue life, performance degradation, and other issues are still open. In the work at hand, landing gear for unmanned aerial vehicles, UAV, is presented, integrated with shape memory alloys springs as actuation devices. A conceptual prototype has been realized to verify the system ability in satisfying specs, in terms of deployment and retraction capability. Starting from the proposed device working principle and the main design parameters identification, the design phase is faced, setting those parameters to meet weight, deployment angle, energy consumption, and available room requirements. Then, system modeling and performance prediction is performed and finally a correlation between numerical and experimental results is presented.

Investigation on the Cyclic Response of Superelastic Shape Memory Alloy (SMA Slit Damper Devices Simulated by Quasi-Static Finite Element (FE Analyses

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Jong Wan Hu

2014-02-01

Full Text Available In this paper, the superelastic shape memory alloy (SMA slit damper system as an alternative design approach for steel structures is intended to be evaluated with respect to inelastic behavior simulated by refined finite element (FE analyses. Although the steel slit dampers conventionally used for aseismic design are able to dissipate a considerable amount of energy generated by the plastic yielding of the base materials, large permanent deformation may occur in the entire structure. After strong seismic events, extra damage repair costs are required to restore the original configuration and to replace defective devices with new ones. Innovative slit dampers fabricated by superelastic SMAs that automatically recover their initial conditions only by the removal of stresses without heat treatment are introduced with a view toward mitigating the problem of permanent deformation. The cyclically tested FE models are calibrated to experimental results for the purpose of predicting accurate behavior. This study also focuses on the material constitutive model that is able to reproduce the inherent behavior of superelastic SMA materials by taking phase transformation between austenite and martensite into consideration. The responses of SMA slit dampers are compared to those of steel slit dampers. Axial stress and strain components are also investigated on the FE models under cyclic loading in an effort to validate the adequacy of FE modeling and then to compare between two slit damper systems. It can be shown that SMA slit dampers exhibit many structural advantages in terms of ultimate strength, moderate energy dissipation and recentering capability.

Pulse width modulation-based temperature tracking for feedback control of a shape memory alloy actuator.

Science.gov (United States)

Ayvali, Elif; Desai, Jaydev P

2014-04-01

This work presents a temperature-feedback approach to control the radius of curvature of an arc-shaped shape memory alloy (SMA) wire. The nonlinear properties of the SMA such as phase transformation and its dependence on temperature and stress make SMA actuators difficult to control. Tracking a desired trajectory is more challenging than controlling just the position of the SMA actuator since the desired path is continuously changing. Consequently, tracking the desired strain directly or tracking the parameters such as temperature and electrical resistance that are related to strain with a model is a challenging task. Temperature-feedback is an attractive approach when direct measurement of strain is not practical. Pulse width modulation (PWM) is an effective method for SMA actuation and it can be used along with a compensator to control the temperature of the SMA. Using the constitutive model of the SMA, the desired temperature profile can be obtained for a given strain trajectory. A PWM-based nonlinear PID controller with a feed-forward heat transfer model is proposed to use temperature-feedback for tracking a desired temperature trajectory. The proposed controller is used during the heating phase of the SMA actuator. The controller proves to be effective in tracking step-wise and continuous trajectories.

Hydrodynamic characterization of a passive shape memory alloy valve

International Nuclear Information System (INIS)

Waddell, A M; Punch, J; Stafford, J; Jeffers, N

2014-01-01

Next generation high-performance electronics will have large heat fluxes (>10 2 W/cm 2 ) and an alternative approach to traditional air cooling is required. An attractive solution is micro-channel cooling and micro-valves will be required for refined flow control in the supporting micro-fluidic systems. A NiTi Shape Memory Alloy (SMA) micro-valve design was hydrodynamically characterized in this work to obtain the valve loss coefficient (K) from pressure measurements. The hydrodynamic characterization was important as in the flow regime of the micro-fluidic system K is sensitive to Reynolds number (Re) and geometry. Static replicas of the SMA valve geometry were studied for low Reynolds numbers (110 – 220) in a 1x1 mm CSA miniature channel. The loss coefficients were found to be sensitive to flow rate and decreased rapidly with an increase in Re. The SMA valve was compared to a similar gate micro-valve and loss across both valves was of the same order of magnitude. The valve loss coefficients obtained in this work are important parameters in the modeling and design of micro-fluidic cooling systems.

Bioinspired Soft Actuation System Using Shape Memory Alloys

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Matteo Cianchetti

2014-07-01

Full Text Available Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors’ previous works on shape memory alloy (SMA springs used as soft actuators, a specific arrangement of such SMA springs is presented, which is combined with a flexible braided sleeve featuring a conical shape and a motor-driven cable. This robot arm is able to perform tasks in water such as grasping, multi-bending gestures, shortening and elongation along its longitudinal axis. The whole structure of the arm is described in detail and experimental results on workspace, bending and grasping capabilities and generated forces are presented. Moreover, this paper demonstrates that it is possible to realize a self-contained octopus-like robotic arm with no rigid parts, highly adaptable and suitable to be mounted on underwater vehicles. Its softness allows interaction with all types of objects with very low risks of damage and limited safety issues, while at the same time producing relatively high forces when necessary.

The role of shape memory alloy on impact response of glass/epoxy laminates under low temperature

International Nuclear Information System (INIS)

Kang, K. W.; Kim, H. J.

2007-01-01

The paper aims to evaluate the impact response of glass/epoxy laminates with embedded shape memory alloy (SMA) subject to low velocity impact at various temperatures. For the goal, the impact tests were performed by using an instrumented impact-testing machine at three temperatures: 293K, 263K and 233K for the baseline (laminates without SMA wires) and SMA laminates (laminates with embedded SMA wires). And the resultant damages were inspected through the scanning acoustic microscope (SAM). Also, based on the impact force history and the damage configuration, the impact resistance parameters were employed to evaluate damage resistance of laminates with embedded SMA wires. As a result, it was observed that the damage resistance of glass/epoxy laminates is influenced by embedded SMA wires and embedding SMA wires into laminates does not compromise the structure any differently to laminates without wires. In fact, it has been shown that under lower temperature, the SMA laminates have a little superior damage resistance compared with the baseline laminates

Shape Memory Alloy Research and Development at NASA Glenn - Current and Future Progress

Science.gov (United States)

Benafan, Othmane

2015-01-01

Shape memory alloys (SMAs) are a unique class of multifunctional materials that have the ability to recover large deformations or generate high stresses in response to thermal, mechanical and or electromagnetic stimuli. These abilities have made them a viable option for actuation systems in aerospace, medical, and automotive applications, amongst others. However, despite many advantages and the fact that SMA actuators have been developed and used for many years, so far they have only found service in a limited range of applications. In order to expand their applications, further developments are needed to increase their reliability and stability and to address processing, testing and qualification needed for large-scale commercial application of SMA actuators.

Experimental investigation on local mechanical response of superelastic NiTi shape memory alloy

International Nuclear Information System (INIS)

Xiao, Yao; Zeng, Pan; Lei, Liping

2016-01-01

In this paper, primary attention is paid to the local mechanical response of NiTi shape memory alloy (SMA) under uniaxial tension. With the help of in situ digital image correlation, sets of experiments are conducted to measure the local strain field at various thermomechanical conditions. Two types of mechanical responses of NiTi SMA are identified. The residual strain localization phenomena are observed, which can be attributed to the localized phase transformation (PT) and we affirm that most of the irreversibility is accumulated simultaneously during PT. It is found that temperature and PT play important roles in inducing delocalization of the reverse transformation. We conclude that forward transformation has more influence on the transition of mechanical response in NiTi SMA than reverse transformation in terms of the critical transition temperature for inducing delocalized reverse transformation. (technical note)

Study of shape memory alloy fibers for the development of artificial myocardium.

Science.gov (United States)

Hassoulas, Ioannis A; Ladopoulos, Vlassios S; Kalogerakos, Paris-Dimitrios K

2010-01-01

Circulatory support devices are employed to treat heart failure. Such a device could be made from shape memory alloy (SMA) fibers. These Ni-Ti fibers contract when electric current flows through them, thus resembling artificial muscles. An artificial myocardium device made from SMA fibers can directly compress the epicardial surface of a failing heart, thus contributing to the pumping action. Unlike modern mechanical circulatory support devices, there is no blood-contacting surface to provoke thromboembolism, hemorrhage, inflammatory response or hemolysis. The experimental setup permitted a detailed study of a sample SMA fiber with great accuracy while the ambient temperature was controlled to resemble that of the human body. The current profile through the fiber was controlled (current shaping, CS) by a microcontroller and a portable computer. Parameters such as strain, contraction and relaxation velocities and the effect of ambient temperature were measured. The contraction and relaxation velocities were measured after applying various effective currents. It was found that the contraction velocity could be manipulated to reach that of the healthy myocardium through CS. On the other hand, the relaxation velocity was independent of the contraction velocity. A cardiac assist device can be made from SMA fibers. More studies need to be conducted in this direction.

An Introduction to a Porous Shape Memory Alloy Dynamic Data Driven Application System

KAUST Repository

Douglas, Craig C.

2012-06-02

Shape Memory Alloys are capable of changing their crystallographic structure due to changes of temperature and/or stress. Our research focuses on three points: (1) Iterative Homogenization of Porous SMAs: Development of a Multiscale Model of porous SMAs utilizing iterative homogenization and based on existing knowledge of constitutive modeling of polycrystalline SMAs. (2) DDDAS: Develop tools to turn on and off the sensors and heating unit(s), to monitor on-line data streams, to change scales based on incoming data, and to control what type of data is generated. The application must have the capability to be run and steered remotely. (3) Modeling and applications of porous SMA: Vibration isolation devices with SMA and porous SMA components for aerospace applications will be analyzed and tested. Numerical tools for modeling porous SMAs with a second viscous phase will be developed.The outcome will be a robust, three-dimensional, multiscale model of porous SMA that can be used in complicated, real-life structural analysis of SMA components using a DDDAS framework.

Application of rapid solidification powder metallurgy processing to prepare Cu–Al–Ni high temperature shape memory alloy strips with high strength and high ductility

Energy Technology Data Exchange (ETDEWEB)

Vajpai, S.K., E-mail: vajpaisk@gmail.com [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Dube, R.K., E-mail: rkd@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Sangal, S., E-mail: sangals@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India)

2013-05-15

Cu–Al–Ni high temperature shape memory alloy (HTSMA) strips were successfully prepared from rapid solidified water atomized Cu–Al–Ni pre-alloyed powders via hot densification rolling of unsheathed sintered powder preforms. Finished heat-treated Cu–Al–Ni alloy strips had fine-grained structure, average grain size approximately 16 μm, and exhibited a combination of high strength and high ductility. It has been demonstrated that the redistribution of nano-sized alumina particles, present on the surface as well as inside the starting water atomized Cu–Al–Ni pre-alloyed powder particles, due to plastic deformation of starting powder particles during hot densification rolling resulted in the fine grained microstructure in the finished SMA strips. The finished SMA strips were almost fully martensitic in nature, consisting of a mixture of β{sub 1}{sup ′} and γ{sub 1}{sup ′} martensite. The average fracture strength and fracture strain of the finished SMA strips were 810 MPa and 12%, respectively, and the fractured specimens exhibited primarily micro-void coalescence type ductile nature of fracture. Finished Cu–Al–Ni SMA strips exhibited high characteristic transformation temperatures and an almost 100% one-way shape recovery was obtained in the specimens up to 4% applied deformation pre-strain. The retained two-way shape memory recovery increased with increasing applied training pre-strain, achieving a maximum value of 16.25% at 5% applied training pre-strain.

Performance characteristics of shape memory alloy and its applications for fusion technology

International Nuclear Information System (INIS)

Nishikawa, Masahiro; Watanabe, Kenji

1987-01-01

As a shape memory alloy, Au-Cd alloy was found in 1951. Thereafter, also in In-Tl alloy, shape memory effect was found. The U.S. Naval Ordinance Laboratory developed Ni-Ti alloy, and published in 1965 as NITINOL. As Cu group shape memory alloys, there are Cu-Zn-Al alloy, Cu-Al-Be alloy and Cu-Al-Ni alloy. Recently, iron group shape memory alloy was published. In 1975, 'Shape memory effect and its application' symposium, in 1978, 'NITINOL heat engine international conference', and in 1982 and 1986, 'Martensite transformation international conference' were held, and the method of the proper use of shape memory alloys and the problems of the alloys themselves such as fatigue have been gradually clarified. In this report, the fundamental action characteristics of shape memory alloys are discribed from the viewpoint of the application, and the possibility of applying these characteristics to nuclear fusion devices and the advantage obtained as the result are explained. Shape memory effect and pseudo-elasticity, reversible shape memory effect, the thermodynamic behavior of shape memory alloys, transformation temperature range and using temperature range and so on are described. (Kako, I.)

Development of laminated nanocomposites on the bases of magnetic and non-magnetic shape memory alloys: Towards new tools for nanotechnology

International Nuclear Information System (INIS)

Irzhak, Artemy; Koledov, Viktor; Zakharov, Dmitry; Lebedev, Gor; Mashirov, Alexey; Afonina, Veronika; Akatyeva, Kristina; Kalashnikov, Vladimir; Sitnikov, Nikolay; Tabachkova, Natalia; Shelyakov, Alexander; Shavrov, Vladimir

2014-01-01

Highlights: ► New results on the recently developed shape memory nanocomposites are reported. ► Impact of FIB fabrication method on shape memory properties was studied. ► Shape memory effect for Ti 2 NiCu sample prepared by FIB vanishes at thickness between 70 nm and 170 nm. ► Ni 2 MnGa-based magnetic microcomposite was fabricated and tested for the first time. -- Abstract: New composite functional material with shape memory effect (SME) has recently been proposed and tested for actuation on microscale. The composite nanotweezers have been designed and tested in manipulation of nano-objects. This report presents the new experiments on shape memory alloy’s (SMAs) properties on submicron scale of dimensions and the development of the technology of nanomanipulation on their bases. The minimal thickness of shape memory layer that undergoes SME was experimentally estimated for Ti 2 NiCu alloy. Impact of the focused ion beam modification of SMA superficial layer on the shape memory properties of micro-sized samples is discussed. Composite actuator of Ni–Mn–Ga magnetic SMA with the size of 20 × 4 × 2 μm 3 was fabricated for the first time and its thermal actuation was experimentally demonstrated ( (http://www.smwsm.org/microactuators/NiMnGa.html))

Using Shape Memory Alloys: A Dynamic Data Driven Approach

KAUST Repository

Douglas, Craig C.

2013-06-01

Shape Memory Alloys (SMAs) are capable of changing their crystallographic structure due to changes of either stress or temperature. SMAs are used in a number of aerospace devices and are required in some devices in exotic environments. We are developing dynamic data driven application system (DDDAS) tools to monitor and change SMAs in real time for delivering payloads by aerospace vehicles. We must be able to turn on and off the sensors and heating units, change the stress on the SMA, monitor on-line data streams, change scales based on incoming data, and control what type of data is generated. The application must have the capability to be run and steered remotely as an unmanned feedback control loop.

Internal stresses in steel plate generated by shape memory alloy inserts

International Nuclear Information System (INIS)

Malard, B.; Pilch, J.; Sittner, P.; Davydov, V.; Sedlák, P.; Konstantinidis, K.; Hughes, D.J.

2012-01-01

Graphical abstract: Display Omitted Highlights: ► Thermoresponsive internal stresses introduced into steel by embedding SMA inclusions. ► Neutron strain scanning on steel plate coupons with NiTi inserts at 21 °C and 130 °C. ► Internal stress field in steel evaluated directly from strains and by FE simulation. ► Internal stress generation by SMA insert resistant to thermal and mechanical fatigue. - Abstract: Neutron strain scanning was employed to investigate the internal stress fields in steel plate coupons with embedded prestrained superelastic NiTi shape memory alloy inserts. Strain fields in steel were evaluated at T = 21 °C and 130 °C on virgin coupons as well as on mechanically and thermally fatigued coupons. Internal stress fields were evaluated by direct calculation of principal stress components from the experimentally measured lattice strains as well as by employing an inverse finite element modeling approach. It is shown that if the NiTi inserts are embedded into the elastic steel matrix following a carefully designed technological procedure, the internal stress fields vary with temperature in a reproducible and predictable way. It is estimated that this mechanism of internal stress generation can be safely applied in the temperature range from −20 °C to 150 °C and is relatively resistant to thermal and mechanical fatigue. The predictability and fatigue endurance of the mechanism are of essential importance for the development of future smart metal matrix composites or smart structures with embedded shape memory alloy components.

TiAu based shape memory alloys for high temperature applications

International Nuclear Information System (INIS)

Wadood, Abdul; Yamabe-Mitarai, Yoko; Hosoda, Hideki

2014-01-01

TiAu (equiatomic) exhibits phase transformaion from B2 (ordered bcc) to thermo-elastic orthorhombic B19 martensite at about 875K and thus TiAu is categorized as high temperature shape memory alloy. In this study, recent research and developments related to TiAu based high temperature shape memory alloys will be discussed in the Introduction part. Then some results of our research group related to strengthening of TiAu based high temperature shape memory alloys will be presented. Potential of TiAu based shape memory alloys for high temperature shape memory materials applications will also be discussed

35 Hz shape memory alloy actuator with bending-twisting mode.

Science.gov (United States)

Song, Sung-Hyuk; Lee, Jang-Yeob; Rodrigue, Hugo; Choi, Ik-Seong; Kang, Yeon June; Ahn, Sung-Hoon

2016-02-19

Shape Memory Alloy (SMA) materials are widely used as an actuating source for bending actuators due to their high power density. However, due to the slow actuation speed of SMAs, there are limitations in their range of possible applications. This paper proposes a smart soft composite (SSC) actuator capable of fast bending actuation with large deformations. To increase the actuation speed of SMA actuator, multiple thin SMA wires are used to increase the heat dissipation for faster cooling. The actuation characteristics of the actuator at different frequencies are measured with different actuator lengths and results show that resonance can be used to realize large deformations up to 35 Hz. The actuation characteristics of the actuator can be modified by changing the design of the layered reinforcement structure embedded in the actuator, thus the natural frequency and length of an actuator can be optimized for a specific actuation speed. A model is used to compare with the experimental results of actuators with different layered reinforcement structure designs. Also, a bend-twist coupled motion using an anisotropic layered reinforcement structure at a speed of 10 Hz is also realized. By increasing their range of actuation characteristics, the proposed actuator extends the range of application of SMA bending actuators.

Adaptive online inverse control of a shape memory alloy wire actuator using a dynamic neural network

Science.gov (United States)

Mai, Huanhuan; Song, Gangbing; Liao, Xiaofeng

2013-01-01

Shape memory alloy (SMA) actuators exhibit severe hysteresis, a nonlinear behavior, which complicates control strategies and limits their applications. This paper presents a new approach to controlling an SMA actuator through an adaptive inverse model based controller that consists of a dynamic neural network (DNN) identifier, a copy dynamic neural network (CDNN) feedforward term and a proportional (P) feedback action. Unlike fixed hysteresis models used in most inverse controllers, the proposed one uses a DNN to identify online the relationship between the applied voltage to the actuator and the displacement (the inverse model). Even without a priori knowledge of the SMA hysteresis and without pre-training, the proposed controller can precisely control the SMA wire actuator in various tracking tasks by identifying online the inverse model of the SMA actuator. Experiments were conducted, and experimental results demonstrated real-time modeling capabilities of DNN and the performance of the adaptive inverse controller.

Confining jackets for concrete cylinders using NiTiNb and NiTi shape memory alloy wires

Energy Technology Data Exchange (ETDEWEB)

Choi, Eunsoo; Yoon, Soon-Jong [Department of Civil Engineering, Hongik University, Seoul 121-791 (Korea, Republic of); Nam, Tae-Hyun [School of Materials Science and Engineering and ERI, Gyeongsang National University, Jinju, Gyeongnam 600-701 (Korea, Republic of); Cho, Sun-Kyu [School of Civil Engineering, Seoul National University of Technology, Seoul 139-743 (Korea, Republic of); Park, Joonam, E-mail: eunsoochoi@hongik.ac.k [Department of Railroad Structure Research, Korea Railroad Research Institute, Uiwang 437-050, Korea (Korea, Republic of)

2010-05-01

This study used prestrained NiTiNb and NiTi shape memory alloy (SMA) wires to confine concrete cylinders. The recovery stress of the wires was measured with respect to the maximal prestrain of the wires. SMA wires were preelongated during the manufacturing process and then wrapped around concrete cylinders of 150 mmx300 mm ({phi}xL). Unconfined concrete cylinders were tested for compressive strength and the results were compared to those of cylinders confined by SMA wires. NiTiNb SMA wires increased the compressive strength and ductility of the cylinders due to the confining effect. NiTiNb wires were found to be more effective in increasing the peak strength of the cylinders and dissipating energy than NiTi wires. This study showed the potential of the proposed method to retrofit reinforced concrete columns using SMA wires to protect them from earthquakes.

Shape-memory effect in Ti-Nb alloys

International Nuclear Information System (INIS)

Peradze, T.; Berikashvili, T.; Chelidze, T.; Gorgadze, K.; Bochorishvili, M.; Taktakishvili, M.

2009-01-01

The work deals with the investigation of the binary alloy of titanium with niobium and is aimed at demonstrating the functional-mechanical possibilities of Ti-Nb alloys from the viewpoint of their potential application in practice. The shape-memory effect, super elasticity and reactive stress in alloys of Ti-Nb system were studied. It turned out that the work carried out expanded the interval of Nb content in the investigated alloys from 25.9 to 33.1 wt%. The shape recovery made up not less than 90% at the deformation of 6-8%. The reactive stress reached 350-450 MPa. In the alloys under study another (high-temperature) shape-memory effect was found, and the influence of hydrogen and oxygen on the inelastic properties of alloys was studied. (author)

Flutter and Thermal Buckling Analysis for Composite Laminated Panel Embedded with Shape Memory Alloy Wires in Supersonic Flow

Directory of Open Access Journals (Sweden)

Chonghui Shao

2016-01-01

Full Text Available The flutter and thermal buckling behavior of laminated composite panels embedded with shape memory alloy (SMA wires are studied in this research. The classical plate theory and nonlinear von-Karman strain-displacement relation are employed to investigate the aeroelastic behavior of the smart laminated panel. The thermodynamic behaviors of SMA wires are simulated based on one-dimensional Brinson SMA model. The aerodynamic pressure on the panel is described by the nonlinear piston theory. Nonlinear governing partial differential equations of motion are derived for the panel via the Hamilton principle. The effects of ply angle of the composite panel, SMA layer location and orientation, SMA wires temperature, volume fraction and prestrain on the buckling, flutter boundary, and amplitude of limit cycle oscillation of the panel are analyzed in detail.

Prospect of Ti-Ni shape memory alloy applied in reactor structures

International Nuclear Information System (INIS)

Duan Yuangang

1995-01-01

Shape memory effect mechanism, physical property, composition, manufacturing process and application in mechanical structure of Ti-Ni shape memory alloy are introduced. Applications of Ti-Ni shape memory alloy in reactor structure are prospected and some necessary technical conditions of shape memory alloy applied in the reactor structure are put forward initially

Hysteresis behaviour of thermoelastic alloys: some shape memory alloys models

International Nuclear Information System (INIS)

Lexcellent, C.; Torra, V.; Raniecki, B.

1993-01-01

The hysteretic behaviour of shape memory alloys (SMA) needs a more and more thin analysis because of its importance for technological applications. The comparison between different approaches allows to explicite the specifity of every model (macroscopic approach, micro-macro level, local description, phenomenological approach) and their points of convergence. On one hand, a thermodynamic treatment with a free energy expression as a mixing rule of each phase (parent or austenite phase and martensite) by adding a coupling term: the configurational energy, allowes modelling of material hysteresis loops. On the other hand, a phenomenological treatment based on a local investigation of two single crystals with a visualisation of microscopic parameters allows to perceive the phase transition mechanisms (nucleation, growth). All the obtained results show the importance of entropy production (or of the definition of the configurational energy term) for the correct description of hysteresis loops (subloops or external). (orig.)

The Characterization of Thin Film Nickel Titanium Shape Memory Alloys

Science.gov (United States)

Harris Odum, Nicole Latrice

Shape memory alloys (SMA) are able to recover their original shape through the appropriate heat or stress exposure after enduring mechanical deformation at a low temperature. Numerous alloy systems have been discovered which produce this unique feature like TiNb, AgCd, NiAl, NiTi, and CuZnAl. Since their discovery, bulk scale SMAs have undergone extensive material property investigations and are employed in real world applications. However, its thin film counterparts have been modestly investigated and applied. Researchers have introduced numerous theoretical microelectromechanical system (MEMS) devices; yet, the research community's overall unfamiliarity with the thin film properties has delayed growth in this area. In addition, it has been difficult to outline efficient thin film processing techniques. In this dissertation, NiTi thin film processing and characterization techniques will be outlined and discussed. NiTi thin films---1 mum thick---were produced using sputter deposition techniques. Substrate bound thin films were deposited to analysis the surface using Scanning Electron Microscopy; the film composition was obtained using Energy Dispersive Spectroscopy; the phases were identified using X-ray diffraction; and the transformation temperatures acquired using resistivity testing. Microfabrication processing and sputter deposition were employed to develop tensile membranes for membrane deflection experimentation to gain insight on the mechanical properties of the thin films. The incorporation of these findings will aid in the movement of SMA microactuation devices from theory to fruition and greatly benefit industries such as medicinal and aeronautical.

The morphing properties of a vascular shape memory composite

International Nuclear Information System (INIS)

Cortes, P; Kubas, G; Terzak, J; Phillips, D; Baur, J W

2014-01-01

This work investigates the fabrication, experimentation, testing, and modeling of shape memory composites consisting of two-way shape memory alloy (SMA) tubes embedded in a shape memory polymer (SMP) matrix. The hybrid system here investigated is thermally activated via internal transport of thermal fluids through the SMA vascular system. The resulting shape memory composite (SMC) combines the high modulus and high specific actuation force of SMAs with the strong shape fixing and variable stiffness of SMPs to create a light-weight composite capable of controllably and rapidly achieving two shape memory states. Specifically, a 25° thermally induced out-of-plane bending state is achieved with a 2% volume fraction of SMA in the composite after 2 min of being activated by an internal thermal fluid. Here, while the thermal structural design of the SMC was not optimized and the thermal cycling was significantly restricted by the low thermal conduction of the SMP, the deflection of the composite was within 20% of the expected value modeled by the thermal–mechanical finite element analysis (FEA) here performed. The close agreement between the experimental performance and the modeled composite response suggests that morphing composites based on SMAs and SMPs are promising structures for adaptive applications. (paper)

Behaviour of smart reinforced concrete beam with super elastic shape memory alloy subjected to monotonic loading

Science.gov (United States)

Hamid, Nubailah Abd; Ibrahim, Azmi; Adnan, Azlan; Ismail, Muhammad Hussain

2018-05-01

This paper discusses the superelastic behavior of shape memory alloy, NiTi when used as reinforcement in concrete beams. The ability of NiTi to recover and reduce permanent deformations of concrete beams was investigated. Small-scale concrete beams, with NiTi reinforcement were experimentally investigated under monotonic loads. The behaviour of simply supported reinforced concrete (RC) beams hybrid with NiTi rebars and the control beam subject to monotonic loads were experimentally investigated. This paper is to highlight the ability of the SMA bars to recover and reduce permanent deformations of concrete flexural members. The size of the control beam is 125 mm × 270 mm × 1000 mm with 3 numbers of 12 mm diameter bars as main reinforcement for compression and 3 numbers of 12 mm bars as tension or hanger bars while 6 mm diameter at 100 mm c/c used as shear reinforcement bars for control beam respectively. While, the minimal provision of 200mm using the 12.7mm of superelastic Shape Memory Alloys were employed to replace the steel rebar at the critical region of the beam. In conclusion, the contribution of the SMA bar in combination with high-strength steel to the conventional reinforcement showed that the SMA beam has exhibited an improve performance in term of better crack recovery and deformation. Therefore the usage of hybrid NiTi with the steel can substantially diminish the risk of the earthquake and also can reduce the associated cost aftermath.

Development of laminated nanocomposites on the bases of magnetic and non-magnetic shape memory alloys: Towards new tools for nanotechnology

Energy Technology Data Exchange (ETDEWEB)

Irzhak, Artemy [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Koledov, Viktor [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation); Zakharov, Dmitry, E-mail: dmitry.zakharov@misis.ru [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Lebedev, Gor [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Mashirov, Alexey; Afonina, Veronika; Akatyeva, Kristina; Kalashnikov, Vladimir [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation); Sitnikov, Nikolay [National Research Nuclear University “MEPhI”, Moscow (Russian Federation); Tabachkova, Natalia [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Shelyakov, Alexander [National Research Nuclear University “MEPhI”, Moscow (Russian Federation); Shavrov, Vladimir [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation)

2014-02-15

Highlights: ► New results on the recently developed shape memory nanocomposites are reported. ► Impact of FIB fabrication method on shape memory properties was studied. ► Shape memory effect for Ti{sub 2}NiCu sample prepared by FIB vanishes at thickness between 70 nm and 170 nm. ► Ni{sub 2}MnGa-based magnetic microcomposite was fabricated and tested for the first time. -- Abstract: New composite functional material with shape memory effect (SME) has recently been proposed and tested for actuation on microscale. The composite nanotweezers have been designed and tested in manipulation of nano-objects. This report presents the new experiments on shape memory alloy’s (SMAs) properties on submicron scale of dimensions and the development of the technology of nanomanipulation on their bases. The minimal thickness of shape memory layer that undergoes SME was experimentally estimated for Ti{sub 2}NiCu alloy. Impact of the focused ion beam modification of SMA superficial layer on the shape memory properties of micro-sized samples is discussed. Composite actuator of Ni–Mn–Ga magnetic SMA with the size of 20 × 4 × 2 μm{sup 3} was fabricated for the first time and its thermal actuation was experimentally demonstrated ( (http://www.smwsm.org/microactuators/NiMnGa.html))

A Review of Selective Laser Melted NiTi Shape Memory Alloy

Science.gov (United States)

Khoo, Zhong Xun; Shen, Yu Fang

2018-01-01

NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed. PMID:29596320

Periodic Cellular Structure Technology for Shape Memory Alloys

Science.gov (United States)

Chen, Edward Y.

2015-01-01

Shape memory alloys are being considered for a wide variety of adaptive components for engine and airframe applications because they can undergo large amounts of strain and then revert to their original shape upon heating or unloading. Transition45 Technologies, Inc., has developed an innovative periodic cellular structure (PCS) technology for shape memory alloys that enables fabrication of complex bulk configurations, such as lattice block structures. These innovative structures are manufactured using an advanced reactive metal casting technology that offers a relatively low cost and established approach for constructing near-net shape aerospace components. Transition45 is continuing to characterize these structures to determine how best to design a PCS to better exploit the use of shape memory alloys in aerospace applications.

Large scale testing of nitinol shape memory alloy devices for retrofitting of bridges

International Nuclear Information System (INIS)

Johnson, Rita; Emmanuel Maragakis, M; Saiid Saiidi, M; Padgett, Jamie E; DesRoches, Reginald

2008-01-01

A large scale testing program was conducted to determine the effects of shape memory alloy (SMA) restrainer cables on the seismic performance of in-span hinges of a representative multiple-frame concrete box girder bridge subjected to earthquake excitations. Another objective of the study was to compare the performance of SMA restrainers to that of traditional steel restrainers as restraining devices for reducing hinge displacement and the likelihood of collapse during earthquakes. The results of the tests show that SMA restrainers performed very well as restraining devices. The forces in the SMA and steel restrainers were comparable. However, the SMA restrainer cables had minimal residual strain after repeated loading and exhibited the ability to undergo many cycles with little strength and stiffness degradation. In addition, the hysteretic damping that was observed in the larger ground accelerations demonstrated the ability of the materials to dissipate energy. An analytical study was conducted to assess the anticipated seismic response of the test setup and evaluate the accuracy of the analytical model. The results of the analytical simulation illustrate that the analytical model was able to match the responses from the experimental tests, including peak stresses, strains, forces, and hinge openings

Characteristics Analysis and Testing of SMA Spring Actuator

Directory of Open Access Journals (Sweden)

Jianzuo Ma

2013-01-01

Full Text Available The biasing form two-way shape memory alloy (SMA actuator composed of SMA spring and steel spring is analyzed. Based on the force equilibrium equation, the relationship between load capacity of SMA spring and geometric parameters is established. In order to obtain the characteristics of SMA spring actuator, the output force and output displacement of SMA spring under different temperatures are analyzed by the theoretical model and the experimental method. Based on the shape memory effect of SMA, the relationship of the SMA spring actuator's output displacement with the temperature, the stress and strain, the material parameters, and the size parameters is established. The results indicate that the trend of theoretical results is basically consistent with the experimental data. The output displacement of SMA spring actuator is increased with the increasing temperature.

Pilot Study for Investigating the Cyclic Behavior of Slit Damper Systems with Recentering Shape Memory Alloy (SMA Bending Bars Used for Seismic Restrainers

Directory of Open Access Journals (Sweden)

Junwon Seo

2015-07-01

Full Text Available Although the steel slit dampers commonly utilized for aseismic design approach can dissipate considerable energy created by the yielding of base materials, large residual deformation may happen in the entire frame structure. After strong external excitation, repair costs will be incurred in restoring a structure to its original condition and to replace broken components. For this reason, alternative recentering devices characterized by smart structures, which mitigate the damage for such steel energy dissipation slit dampers, are developed in this study. These devices, feasibly functioning as seismic restrainers, can be improved by implementing superelastic shape memory alloy (SMA bending bars in a parallel motion with the steel energy-dissipating damper. The bending bars fabricated with superelastic SMAs provide self-centering forces upon unloading, and accordingly contribute to reducing permanent deformation in the integrated slit damper system. The steel slit dampers combined with the superelastic SMA bending bars are evaluated with respect to inelastic behavior as simulated by refined finite element (FE analyses. The FE slit damper models subjected to cyclic loads are calibrated to existing test results in an effort to predict behavior accurately. The responses of the proposed slit damper systems are compared to those of the conventionally used slit damper systems. From the analysis results, it is concluded that innovative steel slit dampers combined with superelastic SMA bending bars generate remarkable performance improvements in terms of post-yield strength, energy dissipation, and recentering capability.

Sensorless displacement estimation of a shape memory alloy coil spring actuator using inductance

International Nuclear Information System (INIS)

Kim, Hongjip; Lee, Dae-young; Cho, Kyu-Jin; Han, Yongsu; Ha, Jung-Ik

2013-01-01

To measure the displacement of a shape memory alloy (SMA) coil spring actuator for feedback control, displacement sensors larger than the actuator are normally required. In this study, a novel method for estimating the displacement of an SMA coil spring actuator without a sensor is proposed. Instead of a sensor, coil inductance is used for estimating the displacement. Coil inductance is estimated by measuring the voltage and the transient response of the current. It has a one-to-one relationship with the displacement of the coil and is not affected by load. Previous methods for estimating displacement using resistance measurements are heavily affected by load variations. The experimental results herein show that displacement is estimated with reasonable accuracy under varying loads using coil inductance. This sensorless method of estimating the displacement of an SMA coil spring actuator can be used to build a compact feedback controller because there is no need for a bulky displacement sensor. (paper)

Influence of Thin-Film Adhesives in Pullout Tests Between Nickel-Titanium Shape Memory Alloy and Carbon Fiber-Reinforced Polymer Matrix Composites

Science.gov (United States)

Quade, Derek J.; Jana, Sadhan; McCorkle, Linda S.

2018-01-01

Strips of nickel-titanium (NiTi) shape memory alloy (SMA) and carbon fiber-reinforced polymer matrix composite (PMC) were bonded together using multiple thin film adhesives and their mechanical strengths were evaluated under pullout test configuration. Tensile and lap shear tests were conducted to confirm the deformation of SMAs at room temperature and to evaluate the adhesive strength between the NiTi strips and the PMC. Optical and scanning electron microscopy techniques were used to examine the interfacial bonding after failure. Simple equations on composite tensile elongation were used to fit the experimental data on tensile properties. ABAQUS models were generated to show the effects of enhanced bond strength and the distribution of stress in SMA and PMC. The results revealed that the addition of thin film adhesives increased the average adhesive strength between SMA and PMC while halting the room temperature shape memory effect within the pullout specimen.

Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Hsu, T.Y.

2000-01-01

Characteristics of martensitic transformation fcc(γ)→hcp(ε) in Fe-Mn-Si based alloys are briefly reviewed. By analyzing the influences of constituents and treatments on shape memory effect (SME) in Fe-Mn-Si, the main factors controlling SME are summarized as austenite strengthening, stacking fault energy (probability) and antiferromagnetic temperature. Contribution of thermomechanical training to SME is introduced. The Fe-Mn-Si-RE (rare earth elements) and Fe-Mn-Si-Cr-N alloys are recommended as two novel shape memory alloys with superior SME. (orig.)

Design and testing of shape memory alloy actuation mechanism for flapping wing micro unmanned aerial vehicles

Science.gov (United States)

Kamaruzaman, N. F.; Abdullah, E. J.

2017-12-01

Shape memory alloy (SMA) actuator offers great solution for aerospace applications with low weight being its most attractive feature. A SMA actuation mechanism for the flapping micro unmanned aerial vehicle (MAV) is proposed in this study, where SMA material is the primary system that provides the flapping motion to the wings. Based on several established design criteria, a design prototype has been fabricated to validate the design. As a proof of concept, an experiment is performed using an electrical circuit to power the SMA actuator to evaluate the flapping angle. During testing, several problems have been observed and their solutions for future development are proposed. Based on the experiment, the average recorded flapping wing angle is 14.33° for upward deflection and 12.12° for downward deflection. This meets the required design criteria and objective set forth for this design. The results prove the feasibility of employing SMA actuators in flapping wing MAV.

Adaptive online inverse control of a shape memory alloy wire actuator using a dynamic neural network

International Nuclear Information System (INIS)

Mai, Huanhuan; Liao, Xiaofeng; Song, Gangbing

2013-01-01

Shape memory alloy (SMA) actuators exhibit severe hysteresis, a nonlinear behavior, which complicates control strategies and limits their applications. This paper presents a new approach to controlling an SMA actuator through an adaptive inverse model based controller that consists of a dynamic neural network (DNN) identifier, a copy dynamic neural network (CDNN) feedforward term and a proportional (P) feedback action. Unlike fixed hysteresis models used in most inverse controllers, the proposed one uses a DNN to identify online the relationship between the applied voltage to the actuator and the displacement (the inverse model). Even without a priori knowledge of the SMA hysteresis and without pre-training, the proposed controller can precisely control the SMA wire actuator in various tracking tasks by identifying online the inverse model of the SMA actuator. Experiments were conducted, and experimental results demonstrated real-time modeling capabilities of DNN and the performance of the adaptive inverse controller. (paper)

Impact damage resistance and damage suppression properties of shape memory alloys in hybrid composites—a review

International Nuclear Information System (INIS)

Angioni, S L; Meo, M; Foreman, A

2011-01-01

Composite materials are known to have a poor resistance to through-the-thickness impact loading. There are various methods for improving their impact damage tolerance, such as fiber toughening, matrix toughening, interface toughening, through-the-thickness reinforcements, and selective interlayers and hybrids. Hybrid composites with improved impact resistance are particularly useful in military and commercial civil applications. Hybridizing composites using shape memory alloys (SMA) is one solution since SMA materials can absorb the energy of the impact through superelastic deformation or recovery stress, reducing the effects of the impact on the composite structure. The SMA material may be embedded in the hybrid composites (SMAHC) in many different forms and also the characteristics of the fiber reinforcements may vary, such as SMA wires in woven laminates or SMA foils in unidirectional laminates, only to cite two examples. We will review the state of the art of SMAHC for the purpose of damage suppression. Both the active and passive damage suppression mechanisms will be considered. (topical review)

Micromechanical analysis of porous SMA

International Nuclear Information System (INIS)

Sepe, V; Marfia, S; Sacco, E; Auricchio, F

2015-01-01

The present paper deals with computational micromechanical analyses of porous shape memory alloy (SMA). Porous SMAs are considered composite materials made of a dense SMA matrix including voids. A three-dimensional constitutive law is presented for the dense SMA able to reproduce the pseudo-elastic as well as the shape memory effects and, moreover, to account for the different elastic properties of the austenite and martensite phases. Furthermore, a numerical procedure is developed and the overall behavior of the porous SMA is recovered studying a representative volume element. Comparisons between the numerical results, recovered using the proposed modeling, and experimental data available in the literature are presented. The case of closed and open porosity is investigated. Parametric studies have been conducted in order to investigate the influence of the porosity, the shape and orientation of the pores on the overall mechanical response and, mainly, on the energy absorption dissipation capability. (paper)

Fabrication and AE characteristics of TiNi/A16061 shape memory alloy composite

International Nuclear Information System (INIS)

Park, Young Chul; Lee, Jin Kyung

2004-01-01

TiNi/A16061 Shape Memory Alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which underwent pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/A16061 SMA composite

35 Hz shape memory alloy actuator with bending-twisting mode

Science.gov (United States)

Song, Sung-Hyuk; Lee, Jang-Yeob; Rodrigue, Hugo; Choi, Ik-Seong; Kang, Yeon June; Ahn, Sung-Hoon

2016-01-01

Shape Memory Alloy (SMA) materials are widely used as an actuating source for bending actuators due to their high power density. However, due to the slow actuation speed of SMAs, there are limitations in their range of possible applications. This paper proposes a smart soft composite (SSC) actuator capable of fast bending actuation with large deformations. To increase the actuation speed of SMA actuator, multiple thin SMA wires are used to increase the heat dissipation for faster cooling. The actuation characteristics of the actuator at different frequencies are measured with different actuator lengths and results show that resonance can be used to realize large deformations up to 35 Hz. The actuation characteristics of the actuator can be modified by changing the design of the layered reinforcement structure embedded in the actuator, thus the natural frequency and length of an actuator can be optimized for a specific actuation speed. A model is used to compare with the experimental results of actuators with different layered reinforcement structure designs. Also, a bend-twist coupled motion using an anisotropic layered reinforcement structure at a speed of 10 Hz is also realized. By increasing their range of actuation characteristics, the proposed actuator extends the range of application of SMA bending actuators. PMID:26892438

Comparing the cyclic behavior of concrete cylinders confined by shape memory alloy wire or steel jackets

International Nuclear Information System (INIS)

Park, Joonam; Choi, Eunsoo; Kim, Hong-Taek; Park, Kyoungsoo

2011-01-01

Shape memory alloy (SMA) wire jackets for concrete are distinct from conventional jackets of steel or fiber reinforced polymer (FRP) since they provide active confinement which can be easily achieved due to the shape memory effect of SMAs. This study uses NiTiNb SMA wires of 1.0 mm diameter to confine concrete cylinders with the dimensions of 300 mm × 150 mm (L × D). The NiTiNb SMAs have a relatively wider temperature hysteresis than NiTi SMAs; thus, they are more suitable for the severe temperature-variation environments to which civil structures are exposed. Steel jackets of passive confinement are also prepared in order to compare the cyclic behavior of actively and passively confined concrete cylinders. For this purpose, monotonic and cyclic compressive loading tests are conducted to obtain axial and circumferential strain. Both strains are used to estimate the volumetric strains of concrete cylinders. Plastic strains from cyclic behavior are also estimated. For the cylinders jacketed by NiTiNb SMA wires, the monotonic axial behavior differs from the envelope of cyclic behavior. The plastic strains of the actively confined concrete show a similar trend to those of passive confinement. This study proposed plastic strain models for concrete confined by SMA wire or steel jackets. For the volumetric strain, the active jackets of NiTiNb SMA wires provide more energy dissipation than the passive jacket of steel

Control of an innovative super-capacitor-powered shape-memory-alloy actuated accumulator for blowout preventer

Science.gov (United States)

Chen, Jian; Li, Peng; Song, Gangbing; Ren, Zhang

2017-01-01

The design of a super-capacitor-powered shape-memory-alloy (SMA) actuated accumulator for blowout preventer (BOP) presented in this paper featured several advantages over conventional hydraulic accumulators including instant large current drive, quick system response and elimination of need for the pressure conduits. However, the mechanical design introduced two challenges, the nonlinear nature of SMA actuators and the varying voltage provided by a super capacitor, for control system design. A cerebellar model articulation controller (CMAC) feedforward plus PID controller was developed with the aim of compensation for these adverse effects. Experiments were conducted on a scaled down model and experimental results show that precision control can be achieved with the proposed configurations and algorithms.

GA-based optimum design of a shape memory alloy device for seismic response mitigation

International Nuclear Information System (INIS)

Ozbulut, O E; Roschke, P N; Lin, P Y; Loh, C H

2010-01-01

Damping systems discussed in this work are optimized so that a three-story steel frame structure and its shape memory alloy (SMA) bracing system minimize response metrics due to a custom-tailored earthquake excitation. Multiple-objective numerical optimization that simultaneously minimizes displacements and accelerations of the structure is carried out with a genetic algorithm (GA) in order to optimize SMA bracing elements within the structure. After design of an optimal SMA damping system is complete, full-scale experimental shake table tests are conducted on a large-scale steel frame that is equipped with the optimal SMA devices. A fuzzy inference system is developed from data collected during the testing to simulate the dynamic material response of the SMA bracing subcomponents. Finally, nonlinear analyses of a three-story braced frame are carried out to evaluate the performance of comparable SMA and commonly used steel braces under dynamic loading conditions and to assess the effectiveness of GA-optimized SMA bracing design as compared to alternative designs of SMA braces. It is shown that peak displacement of a structure can be reduced without causing significant acceleration response amplification through a judicious selection of physical characteristics of the SMA devices. Also, SMA devices provide a recentering mechanism for the structure to return to its original position after a seismic event

Experimental investigation on the vibration tuning of a shell with a shape memory alloy ring

International Nuclear Information System (INIS)

Hong, Jie; Yan, Wenzhong; Ma, Yanhong; Zhang, Dayi; Yang, Xin

2015-01-01

This paper presents a new design of a smart ring with motion actuators made of a shape memory alloy (SMA). The mechanical properties of the SMA actuator were investigated at room (25 °C) and high (90 °C) temperatures to better understand its characteristics. The results show that the smart ring with an SMA not only shows good stability and rapid effectiveness in the vibration control of the test shell, but observably eliminates the nonlinear vibration characteristics due to contact and rubbing between the ring and shell during the heating process. The smart ring also shows excellent performance in the isolation of transient vibration resulting from impact or random loads. With regard to impact loads, the response peak value can reduce by 57.4% in most cases, while the value is 38.7% for random excitations. The study shows the feasibility of using the SMA material for potential applications of vibration tuning the casings of aero-engines. (paper)

Thermomechanical fatigue of shape memory alloys

International Nuclear Information System (INIS)

Lagoudas, D C; Kumar, P K; Miller, D A; Rong, L

2009-01-01

As shape memory alloys (SMAs) gain popularity as high energy density actuators, one characteristic that becomes particularly important is the thermomechanical transformation fatigue life, in addition to maximum transformation strain and stability of actuation cycles. In this paper, a novel test frame design and testing protocol are discussed, for investigating the thermally activated transformation fatigue characteristics of SMAs under various applied loads for both complete and partial phase transformation. A Ni 50 Ti 40 Cu 10 (at.%) SMA was chosen for this investigation and the effects of various heat treatments on the transformation temperatures and the transformation fatigue lives of actuators were studied. For selected heat treatments, the evolution of recoverable and irrecoverable strains up to failure under different applied stress levels was studied in detail. The influence of complete and partial transformation on the fatigue life is also presented. The irrecoverable strain accumulation as a function of the number of cycles to failure for different stress levels is presented by a relationship similar to the Manson–Coffin law for both partial and complete transformations

Fabrication Process and Reliability Evaluation of Shape Memory Alloy Composite

International Nuclear Information System (INIS)

Lee, Jin Kyung; Choi, Il Kook; Park, Young Chul; Lee, Kyu Chang; Lee, Joon Hyun

2001-01-01

Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and A16061 were used as reinforcing material and mix, respectively. In this study, TiNi/A16061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at the boundary between TiNi fiber and Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effect. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/A16061 shape memory alloy composite at high temperature

Development of Miniature Stewart Platform Using TiNiCu Shape-Memory-Alloy Actuators

Directory of Open Access Journals (Sweden)

Alaa AbuZaiter

2015-01-01

Full Text Available A Stewart platform is a parallel manipulator robot that is able to perform three linear movements, lateral, longitudinal, and vertical, and three rotations, pitch, yaw, and roll. This paper reports a 30 mm × 30 mm × 34 mm miniscale Stewart platform using TiNiCu shape-memory-alloy (SMA actuators. The proposed Stewart platform possesses various advantages, such as large actuation force and high robustness with a simple mechanical structure. This Stewart platform uses four SMA actuators and four bias springs and performs a linear z-axis movement and tilting motions. The SMA actuators are activated by passing a current through the SMA wires using a heating circuit that generates a pulse width modulation (PWM signal. This signal is varied to control the level of the displacement and tilting angle of the platform. The tilting direction depends on the SMA actuator that is activated, while all four SMA actuators are activated to achieve the linear z-axis movement. Each SMA actuator exerts a maximum force of 0.6 N at PWM duty cycle of 100%. The fabricated miniature Stewart platform yields a full actuation of 12 mm in the z-axis at 55°C, with a maximum tilting angle of 30° in 4 s.

Fatigue crack behavior on a Cu-Zn-Al SMA

Directory of Open Access Journals (Sweden)

V. Di Cocco

2014-10-01

Full Text Available In recent years, mechanical property of many SMA has improved in order to introduce these alloys in specific field of industry. Main examples of these alloys are the NiTi, Cu-Zn-Al and Cu-Al-Ni which are used in many fields of engineering such as aerospace or mechanical systems. Cu-Zn-Al alloys are characterized by good shape memory properties due to a bcc disordered structure stable at high temperature called β-phase, which is able to change by means of a reversible transition to a B2 structure after appropriate cooling, and reversible transition from B2 secondary to DO3 order, under other types of cooling. In β-Cu-Zn-Al shape memory alloys, the martensitic transformation is not in equilibrium at room temperature. It is therefore often necessary to obtain the martensitic structure, using a thermal treatment at high temperature followed by quenching. The martensitic phases can be either thermally-induced spontaneous transformation, or stressinduced, or cooling, or stressing the β- phase. Direct quenching from high temperatures to the martensite phase is the most effective because of the non-diffusive character of the transformation. The martensite inherits the atomic order from the β-phase. Precipitation of many kinds of intermetallic phases is the main problem of treatment on cu-based shape memory alloy. For instance, a precipitation of α-phase occurs in many low aluminum copper based SMA alloy and presence of α-phase implies a strong degradation of shape recovery. However, Cu-Zn-Al SMA alloys characterized by aluminum contents less than 5% cover a good cold machining and cost is lower than traditional NiTi SMA alloys. In order to improve the SMA performance, it is always necessary to identify the microstructural changing in mechanical and thermal conditions, using X-Ray analyses. In this work a Cu-Zn-Al SMA alloy obtained in laboratory has been microstructurally and metallographically characterized by means of X-Ray diffraction and Light

A phenomenological two-phase constitutive model for porous shape memory alloys

KAUST Repository

El Sayed, Tamer S.

2012-07-01

We present a two-phase constitutive model for pseudoelastoplastic behavior of porous shape memory alloys (SMAs). The model consists of a dense SMA phase and a porous plasticity phase. The overall response of the porous SMA is obtained by a weighted average of responses of individual phases. Based on the chosen constitutive model parameters, the model incorporates the pseudoelastic and pseudoplastic behavior simultaneously (commonly reported for porous SMAs) as well as sequentially (i.e. dense SMAs; pseudoelastic deformation followed by the pseudoplastic deformation until failure). The presented model also incorporates failure due to the deviatoric (shear band formation) and volumetric (void growth and coalescence) plastic deformation. The model is calibrated by representative volume elements (RVEs) with different sizes of spherical voids that are solved by unit cell finite element calculations. The overall response of the model is tested against experimental results from literature. Finally, application of the presented constitutive model has been presented by performing finite element simulations of the deformation and failure in unaixial dog-bone shaped specimen and compact tension (CT) test specimen. Results show a good agreement with the experimental data reported in the literature. © 2012 Elsevier B.V. All rights reserved.

A cycloidal wobble motor driven by shape memory alloy wires

International Nuclear Information System (INIS)

Hwang, Donghyun; Higuchi, Toshiro

2014-01-01

A cycloidal wobble motor driven by shape memory alloy (SMA) wires is proposed. In realizing a motor driving mechanism well known as a type of reduction system, a cycloidal gear mechanism is utilized. It facilitates the achievement of bidirectional continuous rotation with high-torque capability, based on its high efficiency and high reduction ratio. The applied driving mechanism consists of a pin/roller based annular gear as a wobbler, a cycloidal disc as a rotor, and crankshafts to guide the eccentric wobbling motion. The wobbling motion of the annular gear is generated by sequential activation of radially phase-symmetrically placed SMA wires. Consequently the cycloidal disc is rotated by rolling contact based cycloidal gearing between the wobbler and the rotor. In designing the proposed motor, thermomechanical characterization of an SMA wire biased by extension springs is experimentally performed. Then, a simplified geometric model for the motor is devised to conduct theoretical assessment of design parametric effects on structural features and working performance. With consideration of the results from parametric analysis, a functional prototype three-phase motor is fabricated to carry out experimental verification of working performance. The observed experimental results including output torque, rotational speed, bidirectional positioning characteristic, etc obviously demonstrate the practical applicability and potentiality of the wobble motor. (paper)

Developing prospects of NiAlMn high temperature shape memory alloy

International Nuclear Information System (INIS)

Zou Min

1999-01-01

The reason and information on high temperature shape memory alloy research are introduced briefly Also, referring to some experimental reports on NiAlMn high temperature shape memory alloy, it is pointed out that ductility and memory property of this alloy can be improved by adapting proper composition and procedure to control its microstructure. Meanwhile, the engineering details must be considered when NiAlMn high temperature shape memory alloy being developed so as to resolve the problems of its practical use

Influence of Test Procedures on the Thermomechanical Properties of a 55NiTi Shape Memory Alloy

Science.gov (United States)

Padula, Santo A., II; Gaydosh, Darrell J.; Noebe, Ronald D.; Bigelow, Glen S.; Garg, Anita; Lagoudas, Dimitris; Karaman, Ibrahim; Atli, Kadri C.

2008-01-01

Over the past few decades, binary NiTi shape memory alloys have received attention due to their unique mechanical characteristics, leading to their potential use in low-temperature, solid-state actuator applications. However, prior to using these materials for such applications, the physical response of these systems to mechanical and thermal stimuli must be thoroughly understood and modeled to aid designers in developing SMA-enabled systems. Even though shape memory alloys have been around for almost five decades, very little effort has been made to standardize testing procedures. Although some standards for measuring the transformation temperatures of SMA s are available, no real standards exist for determining the various mechanical and thermomechanical properties that govern the usefulness of these unique materials. Consequently, this study involved testing a 55NiTi alloy using a variety of different test methodologies. All samples tested were taken from the same heat and batch to remove the influence of sample pedigree on the observed results. When the material was tested under constant-stress, thermal-cycle conditions, variations in the characteristic material responses were observed, depending on test methodology. The transformation strain and irreversible strain were impacted more than the transformation temperatures, which only showed an affect with regard to applied external stress. In some cases, test methodology altered the transformation strain by 0.005-0.01mm/mm, which translates into a difference in work output capability of approximately 2 J/cu cm (290 in!lbf/cu in). These results indicate the need for the development of testing standards so that meaningful data can be generated and successfully incorporated into viable models and hardware. The use of consistent testing procedures is also important when comparing results from one research organization to another. To this end, differences in the observed responses will be presented, contrasted and

An innovative ultra-capacitor driven shape memory alloy actuator with an embedded control system

International Nuclear Information System (INIS)

Li, Peng; Song, Gangbing

2014-01-01

In this paper, an innovative ultra-capacitor driven shape memory alloy (SMA) actuator with an embedded control system is proposed targeting high power high-duty cycle SMA applications. The ultra-capacitor, which is capable of delivering massive amounts of instantaneous current in a compact dimension for high power applications, is chosen as the main component of the power supply. A specialized embedded system is designed from the ground up to control the ultra-capacitor driven SMA system. The control of the ultra-capacitor driven SMA is different from that of a regular constant voltage powered SMA system in that the energy and the voltage of the ultra-capacitor decrease as the system load increases. The embedded control system is also different from a computer-based control system in that it has limited computational power, and the control algorithm has to be designed to be simple while effective so that it can fit into the embedded system environment. The problem of a variable voltage power source induced by the use of the ultra-capacitor is solved by using a fuzzy PID (proportional integral and derivative) control. The method of using an ultra-capacitor to drive SMA actuators enabled SMA as a good candidate for high power high-duty cycle applications. The proposed embedded control system provides a good and ready-to-use solution for SMA high power applications. (paper)

Applicability of Shape Memory Alloy Wire for an Active, Soft Orthotic

Science.gov (United States)

Stirling, Leia; Yu, Chih-Han; Miller, Jason; Hawkes, Elliot; Wood, Robert; Goldfield, Eugene; Nagpal, Radhika

2011-07-01

Current treatments for gait pathologies associated with neuromuscular disorders may employ a passive, rigid brace. While these provide certain benefits, they can also cause muscle atrophy. In this study, we examined NiTi shape memory alloy (SMA) wires that were annealed into springs to develop an active, soft orthotic (ASO) for the knee. Actively controlled SMA springs may provide variable assistances depending on factors such as when, during the gait cycle, the springs are activated; ongoing muscle activity level; and needs of the wearer. Unlike a passive brace, an active orthotic may provide individualized control, assisting the muscles so that they may be used more appropriately, and possibly leading to a re-education of the neuro-motor system and eventual independence from the orthotic system. A prototype was tested on a suspended, robotic leg to simulate the swing phase of a typical gait. The total deflection generated by the orthotic depended on the knee angle and the total number of actuators triggered, with a max deflection of 35°. While SMA wires have a high energy density, they require a significant amount of power. Furthermore, the loaded SMA spring response times were much longer than the natural frequency of an average gait for the power conditions tested. While the SMA wires are not appropriate for correction of gait pathologies as currently implemented, the ability to have a soft, actuated material could be appropriate for slower timescale applications.

Influence of Silver nanoparticles addition on the phase transformation, mechanical properties and corrosion behaviour of Cu–Al–Ni shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Saud, Safaa N.; Hamzah, E., E-mail: esah@fkm.utm.my; Abubakar, T.; Bakhsheshi-Rad, H.R.; Farahany, S.; Abdolahi, A.; Taheri, M.M.

2014-11-05

Highlights: • Thermal analysis showed four different phase β, α, NiAl and γ2 during solidification. • The martensite appeared in the microstructure as a plate and needle like shape. • Shape recovery ratio of 80% was obtained after Ag nanoparticles addition. • Effect of Ag nanoparticles on the corrosion behaviour of Cu–Al–Ni SMA was investigated. - Abstract: Incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behaviour. However, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics. Four different phase reactions β, α, NiAl and γ{sub 2} were detected on a derivative curve during the solidification by-computer-aided cooling curve thermal analysis. The highest fraction solid (82%) was calculated for the parent phase (β) based on the Newtonian baseline method. The microstructural changes and mechanical properties were investigated using field emission scanning electron microscopy, X-ray diffraction tensile test and shape memory effect test. It was found that the addition of Ag can control the phase morphology and orientations along with the formation of the Ag-rich precipitates, and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect are improved. Remarkably, the shape recovery ratio reached approximately 80% of the original shape. The corrosion behaviour of the Cu–Al–Ni shape memory alloy were investigated using electrochemical tests in NaCl solution and their results showed that the corrosion potential (E{sub corr}) of Cu–Al–Ni SMA is shifted towards the nobler direction from −307.4 to −277.1 m V{sub SCE} with the addition of 0.25 wt.% Ag.

Transformation condition in a Fe-based shape memory alloy under thermomechanical loadings

International Nuclear Information System (INIS)

Nishimura, F.; Watanabe, T.; Tanaka, K.

2000-01-01

The martensitic transformation start conditions in an Fe-9%Cr-5%Ni-14%Mn-6%Si polycrystalline shape memory alloy (SMA) are studied in the stress-temperature space. The martensite start condition is represented by an oval cone, which is not governed by the von Mises type condition. The subsequent martensite start condition is also investigated. The martensite start stress increases both in the initial loading and in the subsequent loading, with the progress of prior martensitic transformation. The concept of linear hardening in plasticity explains well the experimental results. On the contrary, the subsequent martensite start stress returns to the initial value with the progress of the reverse transformation. (orig.)

Ductile shape memory alloys of the Cu-Al-Mn system

International Nuclear Information System (INIS)

Kainuma, R.; Takahashi, S.; Ishida, K.

1995-01-01

Cu-Al-Mn shape memory alloys with enhanced ductility have been developed by decreasing the degree of order in the β parent phase. Cu-Al-Mn alloys with Al contents lower than 18% exhibit good ductility with elongations of about 15% and excellent cold-workability arising from a lower degree of order in the Heusler (L21) β 1 parent phase, without any loss in their shape memory behavior. In this paper the mechanical and shape memory characteristics, such as the cold-workability, the Ms temperatures, the shape memory effect and the pseudo-elasticity of such ductile Cu-Al-Mn alloys are presented. (orig.)

A 1D constitutive model for shape memory alloy using strain and temperature as control variables and including martensite reorientation and asymmetric behaviors

International Nuclear Information System (INIS)

Jaber, M Ben; Mehrez, S; Ghazouani, O

2014-01-01

In this paper, a new 1D constitutive model for shape memory alloy using strain and temperature as control variables is presented. The new formulation is restricted to the 1D stress case and takes into account the martensite reorientation and the asymmetry of the SMA behavior in tension and compression. Numerical implementation of the new model in a finite element code was conducted. The numerical results for superelastic behavior in tension and compression tests are presented and were compared to experimental data taken from the literature. Other numerical tests are presented, showing the model’s ability to reproduce the main aspects of SMA behavior such as the shape memory effect and the martensite reorientation under cyclic loading. Finally, to demonstrate the utility of the new constitutive model, a dynamic test of a bi-clamped SMA bending beam under forced oscillation is described. (paper)

Effect of ternary alloying elements on the shape memory behavior of Ti-Ta alloys

International Nuclear Information System (INIS)

Buenconsejo, Pio John S.; Kim, Hee Young; Miyazaki, Shuichi

2009-01-01

The effect of ternary alloying elements (X = V, Cr, Fe, Zr, Hf, Mo, Sn, Al) on the shape memory behavior of Ti-30Ta-X alloys was investigated. All the alloying elements decreased the martensitic transformation temperatures. The decrease in the martensitic transformation start (M s ) temperature due to alloying was affected by the atomic size and number of valence electrons of the alloying element. A larger number of valence electrons and a smaller atomic radius of an alloying element decreased the M s more strongly. The effect of the alloying elements on suppressing the aging effect on the shape memory behavior was also investigated. It was found that the additions of Sn and Al to Ti-Ta were effective in suppressing the effect of aging on the shape memory behavior, since they strongly suppress the formation of ω phase during aging treatment. For this reason the Ti-30Ta-1Al and Ti-30Ta-1Sn alloys exhibited a stable high-temperature shape memory effect during thermal cycling.

Cavitation erosion of Ti-Ni shape memory alloy deposited coatings and Fe base shape memory alloy solid

International Nuclear Information System (INIS)

Hattori, Shuji; Fujisawa, Seiji; Owa, Tomonobu

2007-01-01

In this study, cavitation erosion tests were carried out by using thermal spraying and deposition of Ti-Ni shape memory alloy for the surface coating. The results show the test speciment of Ti-Ni thermal spraying has many initial defects, so that the erosion resistance is very low. The erosion resistance of Ti-Ni deposit is about 5-10 times higher than that of SUS 304, thus erosion resistance of Ti-Ni deposit is better than that of Ti-Ni thermal spraying. The cavitation erosion tests were carried out by using Fe-Mn-Si with shape memory and gunmetal with low elastic modulus. The erosion resistance of Fe-Mn-Si shape memory alloy solid is about 9 times higher than that of SUS 304. The erosion resistance of gunmetal is almost the same as SUS 304, because the test specimen of gunmetal has many small defects on the original surface. (author)

Application of Shape Memory Alloys in Seismic Isolation: A Review

Directory of Open Access Journals (Sweden)

Shaghayegh Alvandi

2014-12-01

Full Text Available In the last two decades, there has been an increasing interest in structural engineering control methods. Shape memory alloys and seismic isolation systems are examples of passive control systems that use of any one alone, effectively improve the seismic performance of the structure. Characteristics such as large strain range without any residual deformation, high damping capacity, excellent re-centering, high resistance to fatigue and corrosion and durability have made shape memory alloy an effective damping device or part of base isolators. A unique characteristic of shape memory alloys is in recovering residual deformations even after strong ground excitations. Seismic isolation is a device to lessen earthquake damage prospects. In the latest research studies, shape memory alloy is utilized in combination with seismic isolation system and their results indicate the effectiveness of the application of them to control the response of the structures. This paper reviews the findings of research studies on base isolation system implemented in the building and/or bridge structures by including the unique behavior of shape memory alloys. This study includes the primary information about the characteristic of the isolation system as well as the shape memory material. The efficiency and feasibility of the two mechanisms are also presented by few cases in point.

Structural health monitoring for DOT using magnetic shape memory alloy cables in concrete

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Davis, Allen; Mirsayar, Mirmilad; Sheahan, Emery; Hartl, Darren

2018-03-01

Embedding shape memory alloy (SMA) wires in concrete components offers the potential to monitor their structural health via external magnetic field sensing. Currently, structural health monitoring (SHM) is dominated by acoustic emission and vibration-based methods. Thus, it is attractive to pursue alternative damage sensing techniques that may lower the cost or increase the accuracy of SHM. In this work, SHM via magnetic field detection applied to embedded magnetic shape memory alloy (MSMA) is demonstrated both experimentally and using computational models. A concrete beam containing iron-based MSMA wire is subjected to a 3-point bend test where structural damage is induced, thereby resulting in a localized phase change of the MSMA wire. Magnetic field lines passing through the embedded MSMA domain are altered by this phase change and can thus be used to detect damage within the structure. A good correlation is observed between the computational and experimental results. Additionally, the implementation of stranded MSMA cables in place of the MSMA wire is assessed through similar computational models. The combination of these computational models and their subsequent experimental validation provide sufficient support for the feasibility of SHM using magnetic field sensing via MSMA embedded components.

Effect of Al alloying on the martensitic temperature in Ti-Ta shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Ferrari, Alberto; Rogal, Jutta; Drautz, Ralf [Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universitaet Bochum (Germany)

2017-07-01

Ti-Ta-based alloys are promising candidates as high temperature shape memory alloys (HTSMAs) for actuators and superelastic applications. The shape memory mechanism involves a martensitic transformation between the low-temperature α'' phase (orthorhombic) and the high-temperature β phase (body-centered cubic). In order to prevent the degradation of the shape memory effect, Ti-Ta needs to be alloyed with further elements. However, this often reduces the martensitic temperature M{sub s}, which is usually strongly composition dependent. The aim of this work is to analyze how the addition of a third element to Ti-Ta alloys affects M{sub s} by means of electronic structure calculations. In particular, it will be investigated how alloying Al to Ti-Ta alters the relative stability of the α'' and β phases. This understanding will help to identify new alloy compositions featuring both a stable shape memory effect and elevated transformation temperatures.

Design and experimental testing of an adaptive shape-morphing tensegrity structure, with frequency self-tuning capabilities, using shape-memory alloys

International Nuclear Information System (INIS)

Santos, Filipe Amarante dos; Rodrigues, André; Micheletti, Andrea

2015-01-01

The present paper explores the capabilities of a tensegrity-inspired tower with regard to frequency tuning by shape morphing. To change the configuration of the proposed structure, shape-memory-alloy (SMA) actuators are used. This actuation principle also takes advantage of the variation of the elastic modulus of SMAs associated with the martensitic transformation. The temperature modulation of the SMA wires is successfully achieved by Joule heating, through a proportional-integral-derivative controller, to change between a low-temperature shape and a high-temperature shape. The implementation of a short-time-Fourier-transform control algorithm allows for the correct identification of the dominant input frequency, associated with the dynamic excitation. This information is used to automatically change the configuration of the structure in order to shift its natural frequency away from that of the dynamic excitation. With this frequency tuning, one obtains a reduction of the accelerations throughout the structure up to about 80%. The good performance of the proposed control approach gives promising indications regarding the use of tensegrity systems, in combination with SMAs, for shape-morphing applications, and, in particular, for self-tuning structures. (paper)

Laser welding of Ti-Ni type shape memory alloy

International Nuclear Information System (INIS)

Hirose, Akio; Araki, Takao; Uchihara, Masato; Honda, Keizoh; Kondoh, Mitsuaki.

1990-01-01

The present study was undertaken to apply the laser welding to the joining of a shape memory alloy. Butt welding of a Ti-Ni type shape memory alloy was performed using 10 kW CO 2 laser. The laser welded specimens showed successfully the shape memory effect and super elasticity. These properties were approximately identical with those of the base metal. The change in super elasticity of the welded specimen during tension cycling was investigated. Significant changes in stress-strain curves and residual strain were not observed in the laser welded specimen after the 50-time cyclic test. The weld metal exhibited the celler dendrite. It was revealed by electron diffraction analysis that the phase of the weld metal was the TiNi phase of B2 structure which is the same as the parent phase of base metal and oxide inclusions crystallized at the dendrite boundary. However, oxygen contamination in the weld metal by laser welding did not occur because there was almost no difference in oxygen content between the base metal and the weld metal. The transformation temperatures of the weld metal were almost the same as those of the base metal. From these results, laser welding is applicable to the joining of the Ti-Ni type shape memory alloy. As the application of laser welding to new shape memory devices, the multiplex shape memory device of welded Ti-50.5 at % Ni and Ti-51.0 at % Ni was produced. The device showed two-stage shape memory effects due to the difference in transformation temperature between the two shape memory alloys. (author)

Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

Science.gov (United States)

Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

2018-01-01

Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

Science.gov (United States)

Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

2018-03-01

Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

Dynamics of Shape Memory Alloy Systems, Phase 2

Science.gov (United States)

2015-12-22

Nonlinear Dynamics and Chaos in Systems with Discontinuous Support Using a Switch Model”, DINAME 2005 - XI International Conference on Dynamic Problems in...AFRL-AFOSR-CL-TR-2016-0003 Dynamics of Shape Memory Alloy Systems , Phase 2 Marcelo Savi FUNDACAO COORDENACAO DE PROJETOS PESQUISAS E EEUDOS TECNOL...release. 2 AFOSR FINAL REPORT Grant Title: Nonlinear Dynamics of Shape Memory Alloy Systems , Phase 2 Grant #: FA9550-11-1-0284 Reporting Period

Transformation-Induced Relaxation and Stress Recovery of TiNi Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Kohei Takeda

2014-03-01

Full Text Available The transformation-induced stress relaxation and stress recovery of TiNi shape memory alloy (SMA in stress-controlled subloop loading were investigated based on the local variation in temperature and transformation band on the surface of the tape in the tension test. The results obtained are summarized as follows. (1 In the loading process, temperature increases due to the exothermic martensitic transformation (MT until the holding strain and thereafter temperature decreases while holding the strain constant, resulting in stress relaxation due to the MT; (2 In the unloading process, temperature decreases due to the endothermic reverse transformation until the holding strain and thereafter temperature increases while holding the strain constant, resulting in stress recovery due to the reverse transformation; (3 Stress varies markedly in the initial stage followed by gradual change while holding the strain constant; (4 If the stress rate is high until the holding strain in the loading and unloading processes, both stress relaxation and stress recovery are large; (5 It is important to take into account this behavior in the design of SMA elements, since the force of SMA elements varies even if the atmospheric temperature is kept constant.

Evaluation on microscopic damage and fabrication process of shape memory alloy

International Nuclear Information System (INIS)

Lee, Jin Kyung; Choi, Il Kook; Park, Young Chul; Lee, Kyu Chang; Lee, Jun Hyun

2002-01-01

Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and Al6061 were used as reinforcing material and matrix, respectively. In this study, TiNi/Al6061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at tile boundary between TiNi fiber anti Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effort. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite at high temperature.

Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy.

Science.gov (United States)

Takeda, Kohei; Tobushi, Hisaaki; Pieczyska, Elzbieta A

2012-05-22

If the shape memory alloy is subjected to the subloop loading under the stress-controlled condition, creep and creep recovery can appear based on the martensitic transformation. In the design of shape memory alloy elements, these deformation properties are important since the deflection of shape memory alloy elements can change under constant stress. The conditions for the progress of the martensitic transformation are discussed based on the kinetics of the martensitic transformation for the shape memory alloy. During loading under constant stress rate, temperature increases due to the stress-induced martensitic transformation. If stress is held constant during the martensitic transformation stage in the loading process, temperature decreases and the condition for the progress of the martensitic transformation is satisfied, resulting in the transformation-induced creep deformation. If stress is held constant during the reverse transformation stage in the unloading process, creep recovery appears due to the reverse transformation. The details for these thermomechanical properties are investigated experimentally for TiNi shape memory alloy, which is most widely used in practical applications. The volume fraction of the martensitic phase increases in proportion to an increase in creep strain.

Exploiting NiTi shape memory alloy films in design of tunable high frequency microcantilever resonators

Science.gov (United States)

Stachiv, I.; Sittner, P.; Olejnicek, J.; Landa, M.; Heller, L.

2017-11-01

Shape memory alloy (SMA) films are very attractive materials for microactuators because of their high energy density. However, all currently developed SMA actuators utilize martensitic transformation activated by periodically generated heating and cooling; therefore, they have a slow actuation speed, just a few Hz, which restricts their use in most of the nanotechnology applications such as high frequency microcantilever based physical and chemical sensors, atomic force microscopes, or RF filters. Here, we design tunable high frequency SMA microcantilevers for nanotechnology applications. They consist of a phase transforming NiTi SMA film sputtered on the common elastic substrate material; in our case, it is a single-crystal silicon. The reversible tuning of microcantilever resonant frequencies is then realized by intentionally changing the Young's modulus and the interlayer stress of the NiTi film by temperature, while the elastic substrate guarantees the high frequency actuation (up to hundreds of kHz) of the microcantilever. The experimental results qualitatively agree with predictions obtained from the dedicated model based on the continuum mechanics theory and a phase characteristic of NiTi. The present design of SMA microcantilevers expands the capability of current micro-/nanomechanical resonators by enabling tunability of several consecutive resonant frequencies.

My Experience with Ti-Ni-Based and Ti-Based Shape Memory Alloys

Science.gov (United States)

Miyazaki, Shuichi

2017-12-01

The present author has been studying shape memory alloys including Cu-Al-Ni, Ti-Ni-based, and Ni-free Ti-based alloys since 1979. This paper reviews the present author's research results for the latter two materials since 1981. The topics on the Ti-Ni-based alloys include the achievement of superelasticity in Ti-Ni alloys through understanding of the role of microstructures consisting of dislocations and precipitates, followed by the contribution to the development of application market of shape memory effect and superelasticity, characterization of the R-phase and monoclinic martensitic transformations, clarification of the basic characteristics of fatigue properties, development of sputter-deposited shape memory thin films and fabrication of prototypes of microactuators utilizing thin films, development of high temperature shape memory alloys, and so on. The topics of Ni-free Ti-based shape memory alloys include the characterization of the orthorhombic phase martensitic transformation and related shape memory effect and superelasticity, the effects of texture, omega phase and adding elements on the martensitic transformation and shape memory properties, clarification of the unique effects of oxygen addition to induce non-linear large elasticity, Invar effect and heating-induced martensitic transformation, and so on.

Rapid Obtaining of Nano-Hydroxyapatite Bioactive Films on NiTi Shape Memory Alloy by Electrodeposition Process

Science.gov (United States)

Lobo, A. O.; Otubo, J.; Matsushima, J. T.; Corat, E. J.

2011-07-01

Nano-hydroxyapatite (n-HA) crystalline films have been developed in this study by electrodeposition method on NiTi shape memory alloy (SMA). The electrodeposition of the n-HA films was carried out using 0.042 mol/L Ca(NO3)2 · 4H2O + 0.025 mol/L (NH4) · 2HPO4 electrolytes by applying a constant potential of -2.0 V for 120 min and keeping the solution temperature at 70 °C. The characterization of n-HA films is of special importance since bioactive properties related to n-HA have been directly identified with its specific composition and crystalline structure. AFM, XRD, EDX, FEG-SEM and Raman spectroscopy shows a homogeneous film, with high crystallinity, special composition, and bioactivity properties (Ca/P = 1.93) of n-HA on NiTi SMA surfaces. The n-HA coating with special structure would benefit the use of NiTi alloy in orthopedic applications.

Shape memory effects in a uranium + 14 at. % niobium alloy

International Nuclear Information System (INIS)

Vandermeer, R.A.; Ogle, J.C.; Snyder, W.B. Jr.

1978-01-01

There is a class of alloys that, on cooling from elevated temperatures, experience a martensitic phase change. Some of these, when stressed in the martensitic state to an apparently plastic strain, recover their predeformed shape simply by heating. This striking shape recovery is known as the ''shape memory effect'' (SME). Up to a certain limiting strain, epsilon/sub L/, 100% shape recovery may be accomplished. This memory phenomenon seems to be attributable to the thermoelastic nature of and deformational modes associated with the phase transformation in the alloy. Thus, shape recovery results when a stress-biased martensite undergoes a heat-activated reversion back to the parent phase from which it originated. There are uranium alloys that demonstrate SME-behavior. Uranium-rich, uranium--niobium alloys were the first to be documented; New experimental observations of SME in a polycrystalline uranium--niobium alloy are presented. This alloy can exhibit a two-way memory under cetain circumstances. Additional indirect evidence is presented suggesting that the characteristics of the accompanying phase transformation in this alloy meet the criteria or ''selection rules'' deemed essential for SME

Characterization of mechanical properties of pseudoelastic shape memory alloys under harmonic excitation

Science.gov (United States)

Böttcher, J.; Jahn, M.; Tatzko, S.

2017-12-01

Pseudoelastic shape memory alloys exhibit a stress-induced phase transformation which leads to high strains during deformation of the material. The stress-strain characteristic during this thermomechanical process is hysteretic and results in the conversion of mechanical energy into thermal energy. This energy conversion allows for the use of shape memory alloys in vibration reduction. For the application of shape memory alloys as vibration damping devices a dynamic modeling of the material behavior is necessary. In this context experimentally determined material parameters which accurately represent the material behavior are essential for a reliable material model. Subject of this publication is the declaration of suitable material parameters for pseudoelastic shape memory alloys and the methodology of their identification from experimental investigations. The used test rig was specifically designed for the characterization of pseudoelastic shape memory alloys.

Frontiers of Theoretical Research on Shape Memory Alloys: A General Overview

Science.gov (United States)

Chowdhury, Piyas

2018-03-01

In this concise review, general aspects of modeling shape memory alloys (SMAs) are recounted. Different approaches are discussed under four general categories, namely, (a) macro-phenomenological, (b) micromechanical, (c) molecular dynamics, and (d) first principles models. Macro-phenomenological theories, stemming from empirical formulations depicting continuum elastic, plastic, and phase transformation, are primarily of engineering interest, whereby the performance of SMA-made components is investigated. Micromechanical endeavors are generally geared towards understanding microstructural phenomena within continuum mechanics such as the accommodation of straining due to phase change as well as role of precipitates. By contrast, molecular dynamics, being a more recently emerging computational technique, concerns attributes of discrete lattice structures, and thus captures SMA deformation mechanism by means of empirically reconstructing interatomic bonding forces. Finally, ab initio theories utilize quantum mechanical framework to peek into atomistic foundation of deformation, and can pave the way for studying the role of solid-sate effects. With specific examples, this paper provides concise descriptions of each category along with their relative merits and emphases.

Design and property analysis of a hybrid linear actuator based on shape memory alloy

International Nuclear Information System (INIS)

Zhang, Xiaoguang; Hu, Jinhong; Mao, Shixin; Dong, Erbao; Yang, Jie

2014-01-01

This paper introduces two methods for solving two bottlelike problems regarding the shape memory alloy (SMA) application as actuators. These methods are ‘rotating output,’ which aims to solve the problem of the low working frequency caused by the demand for cool time, and ‘accumulated shifting,’ which solves the problem of difficult-to-obtain output displacements in a large scale. We also introduce a hybrid linear actuator that applies the two methods and achieves both a strong force and an accurate large output displacement while working at a high frequency based on the SMA wires and DC motors. A prototype of this actuator was fabricated and tested to verify the two methods. This hybrid actuator system dynamic model, which was composed of the constitutive model of the SMA, the electrical and heat transfer behavior of the SMA wires and the dynamics of the linear actuation system, was established and discussed. Our study aims to illuminate the application of an SMA in actuators with the proposed methods with regard to its two main problems. An actuator with a high power-weight ratio and the capability to work at a high frequency, as well as accurate linear step displacements in a large scale, is also presented. (paper)

Radioactive material package closures with the use of shape memory alloys

International Nuclear Information System (INIS)

Koski, J.A.; Bronowski, D.R.

1997-11-01

When heated from room temperature to 165 C, some shape memory metal alloys such as titanium-nickel alloys have the ability to return to a previously defined shape or size with dimensional changes up to 7%. In contrast, the thermal expansion of most metals over this temperature range is about 0.1 to 0.2%. The dimension change of shape memory alloys, which occurs during a martensite to austenite phase transition, can generate stresses as high as 700 MPa (100 kspi). These properties can be used to create a closure for radioactive materials packages that provides for easy robotic or manual operations and results in reproducible, tamper-proof seals. This paper describes some proposed closure methods with shape memory alloys for radioactive material packages. Properties of the shape memory alloys are first summarized, then some possible alternative sealing methods discussed, and, finally, results from an initial proof-of-concept experiment described

Constitutive modeling and structural analysis considering simultaneous phase transformation and plastic yield in shape memory alloys

Science.gov (United States)

Hartl, D. J.; Lagoudas, D. C.

2009-10-01

The new developments summarized in this work represent both theoretical and experimental investigations of the effects of plastic strain generation in shape memory alloys (SMAs). Based on the results of SMA experimental characterization described in the literature and additional testing described in this work, a new 3D constitutive model is proposed. This phenomenological model captures both the conventional shape memory effects of pseudoelasticity and thermal strain recovery, and additionally considers the initiation and evolution of plastic strains. The model is numerically implemented in a finite element framework using a return mapping algorithm to solve the constitutive equations at each material point. This combination of theory and implementation is unique in its ability to capture the simultaneous evolution of recoverable transformation strains and irrecoverable plastic strains. The consideration of isotropic and kinematic plastic hardening allows the derivation of a theoretical framework capturing the interactions between irrecoverable plastic strain and recoverable strain due to martensitic transformation. Further, the numerical integration of the constitutive equations is formulated such that objectivity is maintained for SMA structures undergoing moderate strains and large displacements. The implemented model has been used to perform 3D analysis of SMA structural components under uniaxial and bending loads, including a case of local buckling behavior. Experimentally validated results considering simultaneous transformation and plasticity in a bending member are provided, illustrating the predictive accuracy of the model and its implementation.

Constitutive modeling and structural analysis considering simultaneous phase transformation and plastic yield in shape memory alloys

International Nuclear Information System (INIS)

Hartl, D J; Lagoudas, D C

2009-01-01

The new developments summarized in this work represent both theoretical and experimental investigations of the effects of plastic strain generation in shape memory alloys (SMAs). Based on the results of SMA experimental characterization described in the literature and additional testing described in this work, a new 3D constitutive model is proposed. This phenomenological model captures both the conventional shape memory effects of pseudoelasticity and thermal strain recovery, and additionally considers the initiation and evolution of plastic strains. The model is numerically implemented in a finite element framework using a return mapping algorithm to solve the constitutive equations at each material point. This combination of theory and implementation is unique in its ability to capture the simultaneous evolution of recoverable transformation strains and irrecoverable plastic strains. The consideration of isotropic and kinematic plastic hardening allows the derivation of a theoretical framework capturing the interactions between irrecoverable plastic strain and recoverable strain due to martensitic transformation. Further, the numerical integration of the constitutive equations is formulated such that objectivity is maintained for SMA structures undergoing moderate strains and large displacements. The implemented model has been used to perform 3D analysis of SMA structural components under uniaxial and bending loads, including a case of local buckling behavior. Experimentally validated results considering simultaneous transformation and plasticity in a bending member are provided, illustrating the predictive accuracy of the model and its implementation

Analysis of hybrid electric/thermofluidic inputs for wet shape memory alloy actuators

Science.gov (United States)

Flemming, Leslie; Mascaro, Stephen

2013-01-01

A wet shape memory alloy (SMA) actuator is characterized by an SMA wire embedded within a compliant fluid-filled tube. Heating and cooling of the SMA wire produces a linear contraction and extension of the wire. Thermal energy can be transferred to and from the wire using combinations of resistive heating and free/forced convection. This paper analyzes the speed and efficiency of a simulated wet SMA actuator using a variety of control strategies involving different combinations of electrical and thermofluidic inputs. A computational fluid dynamics (CFD) model is used in conjunction with a temperature-strain model of the SMA wire to simulate the thermal response of the wire and compute strains, contraction/extension times and efficiency. The simulations produce cycle rates of up to 5 Hz for electrical heating and fluidic cooling, and up to 2 Hz for fluidic heating and cooling. The simulated results demonstrate efficiencies up to 0.5% for electric heating and up to 0.2% for fluidic heating. Using both electric and fluidic inputs concurrently improves the speed and efficiency of the actuator and allows for the actuator to remain contracted without continually delivering energy to the actuator, because of the thermal capacitance of the hot fluid. The characterized speeds and efficiencies are key requirements for implementing broader research efforts involving the intelligent control of electric and thermofluidic networks to optimize the speed and efficiency of wet actuator arrays.

Martensitic transformations and the shape memory effect in Ti-Zr-Nb-Al high-temperature shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fei; Yu, Zhiguo; Xiong, Chengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), Beihang University, Beijing 100191 (China); Qu, Wentao; Yuan, Bifei [School of Mechanical Engineering, Xi’an Shiyou University, Xi’an 710065 (China); Wang, Zhenguo [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), Beihang University, Beijing 100191 (China); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), Beihang University, Beijing 100191 (China)

2017-01-02

The microstructures, phase transformations, mechanical properties and shape memory effect of Ti-20Zr-10Nb-xAl (x=1, 2, 3, 4 at%) alloys were investigated. The X-ray diffraction results show that the alloys are composed of a single martensitic α″-phase and that the corresponding unit cell volume decreases with increasing Al content. The reverse martensitic transformation start temperature (A{sub s}) of the Ti-20Zr-10Nb-Al alloy is 534 K and decreases with increasing Al content. The addition of Al results in solid solution strengthening and grain refinement strengthening, thus improving the mechanical properties and the shape memory effect of the Ti-20Zr-10 Nb-xAl alloys. The Ti-20Zr-10Nb-3Al alloy shows the greatest shape memory strain (3.2%) and the largest tensile strain (17.6%) as well as a very high tensile strength (886 MPa).

Thermo-mechanically coupled fracture analysis of shape memory alloys using the extended finite element method

Science.gov (United States)

Hatefi Ardakani, S.; Ahmadian, H.; Mohammadi, S.

2015-04-01

In this paper, the extended finite element method is used for fracture analysis of shape memory alloys for both cases of super elastic and shape memory effects. Heat generation during the forward and reverse phase transformations can lead to temperature variation in the material because of strong thermo-mechanical coupling, which significantly influences the SMA mechanical behavior. First, the stationary crack mode is studied and the effects of loading rate on material behavior in the crack tip are examined. Then, the crack propagation analysis is performed in the presence of an initial crack by adopting a weighted averaging criterion, where the direction of crack propagation is determined by weighted averaging of effective stresses at all the integration points in the vicinity of the crack tip. Finally, several numerical examples are analyzed and the obtained results are compared with the available reference results.

Hysteresis model of shape memory alloy wire-based laminated rubber bearing under compression and unidirectional shear loadings

International Nuclear Information System (INIS)

Hedayati Dezfuli, F; Alam, M Shahria

2015-01-01

Smart lead rubber bearings (LRBs), in which a shape memory alloy (SMA) is used in the form of wires, are a new generation of elastomeric isolators with improved performance in terms of recentering capability and energy dissipation capacity. It is of great interest to implement SMA wire-based lead rubber bearings (SMA-LRBs) in bridges; however, currently there is no appropriate hysteresis model for accurately simulating the behavior of such isolators. A constitutive model for SMA-LRBs is proposed in this study. An LRB is equipped with a double cross configuration of SMA wires (DC-SMAW) and subjected to compression and unidirectional shear loadings. Due to the complexity of the shear behavior of the SMA-LRB, a hysteresis model is developed for the DC-SMAWs and then combined with the bilinear kinematic hardening model, which is assumed for the LRB. Comparing the hysteretic response of decoupled systems with that of the SMA-LRB shows that the high recentering capability of the DC-SMAW model with zero residual deformation could noticeably reduce the residual deformation of the LRB. The developed constitutive model for DC-SMAWs is characterized by three stiffnesses when the shear strain exceeds a starting limit at which the SMA wires are activated due to phase transformation. An important point is that the shear hysteresis of the DC-SMAW model looks different from the flag-shaped hysteresis of the SMA because of the specific arrangement of wires and its effect on the resultant forces transferred from the wires to the rubber bearing. (paper)

A bidirectional shape memory alloy folding actuator

International Nuclear Information System (INIS)

Paik, Jamie K; Wood, Robert J

2012-01-01

This paper presents a low-profile bidirectional folding actuator based on annealed shape memory alloy sheets applicable for meso- and microscale systems. Despite the advantages of shape memory alloys—high strain, silent operation, and mechanical simplicity—their application is often limited to unidirectional operation. We present a bidirectional folding actuator that produces two opposing 180° motions. A laser-patterned nickel alloy (Inconel 600) heater localizes actuation to the folding sections. The actuator has a thin ( < 1 mm) profile, making it appropriate for use in robotic origami. Various design parameters and fabrication variants are described and experimentally explored in the actuator prototype. (paper)

Shape memory alloys: metallurgy, biocompatibility, and biomechanics for neurosurgical applications.

Science.gov (United States)

Hoh, Daniel J; Hoh, Brian L; Amar, Arun P; Wang, Michael Y

2009-05-01

SHAPE MEMORY ALLOYS possess distinct dynamic properties with particular applications in neurosurgery. Because of their unique physical characteristics, these materials are finding increasing application where resiliency, conformation, and actuation are needed. Nitinol, the most frequently manufactured shape memory alloy, responds to thermal and mechanical stimuli with remarkable mechanical properties such as shape memory effect, super-elasticity, and high damping capacity. Nitinol has found particular use in the biomedical community because of its excellent fatigue resistance and biocompatibility, with special interest in neurosurgical applications. The properties of nitinol and its diffusionless phase transformations contribute to these unique mechanical capabilities. The features of nitinol, particularly its shape memory effect, super-elasticity, damping capacity, as well as its biocompatibility and biomechanics are discussed herein. Current and future applications of nitinol and other shape memory alloys in endovascular, spinal, and minimally invasive neurosurgery are introduced. An understanding of the metallurgic properties of nitinol provides a foundation for further exploration of its use in neurosurgical implant design.

Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

DEFF Research Database (Denmark)

Enemark, Søren; Santos, Ilmar; Savi, Marcelo A.

2015-01-01

passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with temperature variations and thus they may change system dynamics. Shape memory alloys also exhibit...... perturbations and mass imbalance responses of the rotor-bearing system at different temperatures and excitation frequencies are carried out to determine the dynamic behaviour of the system. The behaviour and the performance in terms of vibration reduction and system adaptability are compared against a benchmark...... configuration comprised by the same system having steel springs instead of shape memory alloy springs. The experimental results clearly show that the stiffness changes and hysteretic behaviour of the shape memory alloys springs alter system dynamics both in terms of critical speeds and mode shapes. Vibration...

Fabricating Composite-Material Structures Containing SMA Ribbons

Science.gov (United States)

Turner, Travis L.; Cano, Roberto J.; Lach, Cynthia L.

2003-01-01

An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated. Such structures, denoted as shape-memory-alloy hybrid composite (SMAHC) structures, have been investigated for their potential to satisfy requirements to control the shapes or thermoelastic responses of themselves or of other structures into which they might be incorporated, or to control noise and vibrations. Much of the prior work on SMAHC structures has involved the use SMA wires embedded within matrices or within sleeves through parent structures. The disadvantages of using SMA wires as the embedded actuators include (1) complexity of fabrication procedures because of the relatively large numbers of actuators usually needed; (2) sensitivity to actuator/ matrix interface flaws because voids can be of significant size, relative to wires; (3) relatively high rates of breakage of actuators during curing of matrix materials because of sensitivity to stress concentrations at mechanical restraints; and (4) difficulty of achieving desirable overall volume fractions of SMA wires when trying to optimize the integration of the wires by placing them in selected layers only.

The industrial applications of shape memory alloys in North America

International Nuclear Information System (INIS)

Mc Schetky D, L.

2000-01-01

Literature in the recent past on shape memory effect alloys dwelt principally on the physical metallurgy, crystallography and kinetics of the shape memory phenomenon. By contrast, we now have books and conference proceedings devoted to the engineering aspects of SMAs, their technology and application. The dominant role SMAs now play in the field of medical and orthodontic devices is well documented and will be reviewed by others in this conference. In this paper we will discuss the commercial applications for shape memory alloy devices in the North American market; applications which are in many cases also produced in European countries and Japan. The early success of shape memory alloy couplings for joining tubing and pipe in the late 1960's was not followed by other large volume applications until the advent of shape memory eyeglass frames, brassiere underwires and cellular phone antennas. Many other applications have now evolved into mature markets and these will be reviewed. In addition to the many commercial applications cited, there are a number of other fields in which shape memory alloys are destined to play a major role; these include smart materials and adaptive structures, MEMS devices, infrastructure systems and electrical power generation and distribution. These applications are being developed with private and government funding and will also be briefly discussed. (orig.)

The industrial applications of shape memory alloys in North America

Energy Technology Data Exchange (ETDEWEB)

Mc Schetky D, L. [Memry Corp., Brookfield, CT (United States)

2000-07-01

Literature in the recent past on shape memory effect alloys dwelt principally on the physical metallurgy, crystallography and kinetics of the shape memory phenomenon. By contrast, we now have books and conference proceedings devoted to the engineering aspects of SMAs, their technology and application. The dominant role SMAs now play in the field of medical and orthodontic devices is well documented and will be reviewed by others in this conference. In this paper we will discuss the commercial applications for shape memory alloy devices in the North American market; applications which are in many cases also produced in European countries and Japan. The early success of shape memory alloy couplings for joining tubing and pipe in the late 1960's was not followed by other large volume applications until the advent of shape memory eyeglass frames, brassiere underwires and cellular phone antennas. Many other applications have now evolved into mature markets and these will be reviewed. In addition to the many commercial applications cited, there are a number of other fields in which shape memory alloys are destined to play a major role; these include smart materials and adaptive structures, MEMS devices, infrastructure systems and electrical power generation and distribution. These applications are being developed with private and government funding and will also be briefly discussed. (orig.)

An innovative seismic bracing system based on a superelastic shape memory alloy ring

International Nuclear Information System (INIS)

Gao, Nan; Jeon, Jong-Su; DesRoches, Reginald; Hodgson, Darel E

2016-01-01

Shape memory alloys (SMAs) have great potential in seismic applications because of their remarkable superelasticity. Seismic bracing systems based on SMAs can mitigate the damage caused by earthquakes. The current study investigates a bracing system based on an SMA ring which is capable of both re-centering and energy dissipation. This lateral force resisting system is a cross-braced system consisting of an SMA ring and four tension-only cable assemblies, which can be applied to both new construction and seismic retrofit. The performance of this bracing system is examined through a quasi-static cyclic loading test and finite element (FE) analysis. This paper describes the experimental design in detail, discusses the experimental results, compares the performance with other bracing systems based on SMAs, and presents an Abaqus FE model calibrated on the basis of experimental results to simulate the superelastic behavior of the SMA ring. The experimental results indicate that the seismic performance of this system is promising in terms of damping and re-centering. The FE model can be used in the simulation of building structures using the proposed bracing system. (paper)

Adaptive proportional–integral–derivative tuning sliding mode control for a shape memory alloy actuator

International Nuclear Information System (INIS)

Tai, Nguyen Trong; Ahn, Kyoung Kwan

2011-01-01

In this paper, a novel adaptive sliding mode control with a proportional–integral–derivative (PID) tuning method is proposed to control a shape memory alloy (SMA) actuator. The goal of the controller is to achieve system robustness against the SMA hysteresis phenomenon, system uncertainties and external disturbances. In the controller, the PID controller is employed to approximate the sliding mode equivalent control along the direction that makes the sliding mode asymptotically stable. Due to the system nonlinearity, the PID control gain parameters are systematically computed online according to the adaptive law. To improve the transient performance, the initial PID gain parameters are optimized by the particle swarm optimization (PSO) method. Simulation and experimental results demonstrate that the controller performs well for the desired trajectory tracking, and the hysteresis phenomenon is compensated for completely. The control results are also compared with the optimized PID controller

Design of shape memory alloy actuators for direct power by an automotive battery

International Nuclear Information System (INIS)

Leary, M.; Huang, S.; Ataalla, T.; Baxter, A.; Subic, A.

2013-01-01

Highlights: ► We model Ni–Ti SMA actuators directly powered by a standard automotive battery. ► Feasible permutations for direct power are identified and confirmed experimentally. ► 0.5 mm diameter SMA of 225 mm length or larger is feasible for direct power. ► The feasibility of 0.25 mm SMA is greater, although the actuation force is lower. ► Prototype actuators are developed for long-stroke and short-stroke applications. -- Abstract: Nickel–Titanium (Ni–Ti) Shape Memory Alloys (SMAs) are increasingly utilized as mechanical actuators due to high power-to-mass ratio, high fatigue life and low cost. The implementation of SMA actuators in an automotive environment is of particular interest due to the potential for lower end-user functional efforts, together with reduced component mass and cost within a limited packaging space. In applications of this kind, the actuators are powered by a standard automotive (six cell lead-acid) battery. Although resistors and electronic devices can be used to avoid overload of either the SMA or battery system, the feasibility of supplying power to the actuators directly from the battery becomes a key objective for reducing system cost and complexity. In this study, the electrical resistivity of a linear Ni–Ti SMA actuator was theoretically calculated and experimentally verified. Based on this developed knowledge, the resistance of various actuator permutations was calculated, and the feasibility of operating the actuators with a standard automotive battery was assessed. To confirm the feasibility of powering SMA actuators directly from the automotive battery, two SMA actuator concepts were developed and experimentally validated.

Oxidation Kinetics of a NiPtTi High Temperature Shape Memory Alloy

Science.gov (United States)

Smialek, James L.; Humphrey, Donald L.; Noebe, Ronald D.

2007-01-01

A high temperature shape memory alloy (HTSMA), Ni30Pt50Ti, with an M(sub s) near 600 C, was isothermally oxidized in air for 100 hr over the temperature range of 500 to 900 C. Parabolic kinetics were confirmed by log-log and parabolic plots and showed no indication of fast transient oxidation. The overall behavior could be best described by the Arrhenius relationship: k(sub p) = 1.64 x 10(exp 12)[(-250 kJ/mole)/RT] mg(sup 2)/cm(sup 4)hr. This is about a factor of 4 reduction compared to values measured here for a binary Ni47Ti commercial SMA. The activation energy agreed with most literature values for TiO2 scale growth measured for elemental Ti and other NiTi alloys. Assuming uniform alloy depletion of a 20 mil (0.5 mm) dia. HTSMA wire, approx. 1 percent Ti reduction is predicted after 20,000 hr oxidation at 500 C, but becomes much more serious at higher temperatures.

Numerical analysis of dynamic behavior of pre-stressed shape memory alloy concrete beam-column joints

Science.gov (United States)

Yan, S.; Xiao, Z. F.; Lin, M. Y.; Niu, J.

2018-04-01

Beam-column joints are important parts of a main frame structure. Mechanical properties of beam-column joints have a great influence on dynamic performances of the frame structure. Shape memory alloy (SMA) as a new type of intelligent metal materials has wide applications in civil engineering. The paper aims at proposing a novel beam-column joint reinforced with pre-stressed SMA tendons to increase its dynamic performance. Based on the finite element analysis (FEA) software ABAQUS, a numerical simulation for 6 beam-column scaled models considering different SMA reinforcement ratios and pre-stress levels was performed, focusing on bearing capacities, energy-dissipation and self-centering capacities, etc. These models were numerically tested under a pseudo-static load on the beam end, companying a constant vertical compressive load on the top of the column. The numerical results show that the proposed SMA-reinforced joint has a significantly increased bearing capacity and a good self-centering capability after unloading even though the energy-dissipation capacity becomes smaller due the less residual deformation. The concept and mechanism of the novel joint can be used as an important reference for civil engineering applications.

A new mechanical characterization method for thin film microactuators and its application to NiTiCi shape memory alloy

International Nuclear Information System (INIS)

Seward, K P

1999-01-01

In an effort to develop a more full characterization tool of shape memory alloys, a new technique is presented for the mechanical characterization of microactuators and applied to SMA thin films. A test instrument was designed to utilize a spring-loaded transducer in measuring displacements with resolution of 1.5 pm and forces with resolution of 0.2 mN. Employing an out-of-plane loading method for freestanding SMA thin films, strain resolution of 30(mu)(epsilon) and stress resolution of 2.5 MPa were achieved. This new testing method is presented against previous SMA characterization methods for purposes of comparison. Four mm long, 2(micro)m thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. The fabrication process used to micromachine the ligaments is presented step-by-step, alongside methods of fabrication that failed to produce testable ligaments. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. In terms of recoverable stress and recoverable strain, the ligaments achieved maximum recovery of 700 MPa and 3.0% strain. No permanent deformations were seen in any ligament during deflection measurements. Maximum actuation forces and displacements produced by the 4 mm ligaments situated on 1 cm square test chips were 56 mN and 300(micro)m, respectively. Fatigue analysis of the ligaments showed degradation in recoverable strain from 0.33% to 0.24% with 200,000 cycles, corresponding to deflections of 90(micro)m and forces of 25 mN. Cycling also produced a wavering shape memory effect late in ligament life, leading to broad inconsistencies of as much as 35% deviation from average. Unexpected phenomena like stress-induced martensitic twinning that leads to less recoverable stress and the shape memory behavior of long life devices are addressed. Finally, a model for design of microactuators using shape memory

Joint made of shape memory alloy

International Nuclear Information System (INIS)

Amano, Kazuo; Enomoto, Kunio

1998-01-01

The present invention provides a joint which is less loosen even if it is used under a circumference undergoing heat cycles such as in a nuclear power plant. Namely, a liner shape has a structure different between the right-to-left, which is different from existent right and left symmetrical shape. A groove is formed on the side of pipeline to be connected, and upon joint connection, the liner is pushed into the groove formed on the pipeline to connect them by the force caused upon transformation of the shape memory alloy. In the joint having such a structure, the clamping force of the joint is less reduced by the effects of heat cycles. Even when the clamping force is reduced by some or other causes, the joint is not dropped off from the pipeline. Even when the joint made of a shape memory alloy of a type using a liner is used as a joint for connecting longitudinal pipelines of a nuclear power plant, the reliability and the safety can be maintained. (I.S.)

Engineering Design Tools for Shape Memory Alloy Actuators: CASMART Collaborative Best Practices and Case Studies

Science.gov (United States)

Wheeler, Robert W.; Benafan, Othmane; Gao, Xiujie; Calkins, Frederick T; Ghanbari, Zahra; Hommer, Garrison; Lagoudas, Dimitris; Petersen, Andrew; Pless, Jennifer M.; Stebner, Aaron P.;

Compliant liquid column damper modified by shape memory alloy device for seismic vibration control

International Nuclear Information System (INIS)

Gur, Sourav; Mishra, Sudib Kumar; Bhowmick, Sutanu; Chakraborty, Subrata

2014-01-01

Liquid column dampers (LCDs) have long been used for the seismic vibration control of flexible structures. In contrast, tuning LCDs to short-period structures poses difficulty. Various modifications have been proposed on the original LCD configuration for improving its performance in relatively stiff structures. One such system, referred to as a compliant-LCD has been proposed recently by connecting the LCD to the structure with a spring. In this study, an improvement is attempted in compliant LCDs by replacing the linear spring with a spring made of shape memory alloy (SMA). Considering the dissipative, super-elastic, force-deformation hysteresis of SMA triggered by stress-induced micro-structural phase transition, the performance is expected to improve further. The optimum parameters for the SMA-compliant LCD are obtained through design optimization, which is based on a nonlinear random vibration response analysis via stochastic linearization of the force-deformation hysteresis of SMA and dissipation by liquid motion through an orifice. Substantially enhanced performance of the SMA–LCD over a conventional compliant LCD is demonstrated, the consistency of which is further verified under recorded ground motions. The robustness of the improved performance is also validated by parametric study concerning the anticipated variations in system parameters as well as variability in seismic loading. (paper)

Thermomechanical behavior of Fe-Mn-Si-Cr-Ni shape memory alloys modified with samarium

International Nuclear Information System (INIS)

Shakoor, R.A.; Khalid, F. Ahmad

2009-01-01

The deformation and training behavior of Fe-14Mn-3Si-10Cr-5Ni (wt.%) shape memory alloys containing samarium addition has been studied in the iron-based shape memory alloys. It is noticed that thermomechanical treatment (training) has significant influence on proof stress, critical stress and shape memory behavior of the alloys. The improvement in shape memory behavior can be attributed to the decrease in the proof stress and critical stress which facilitates the formation of ε (hcp martensite). It is also observed that alloy 2 containing samarium undergoes less softening as compared to alloy 1 with training which inhibits the formation of α (bcc martensite) and thus enhances the shape memory behavior. The excessive thermomechanical treatment with increase in the training cycle has led to the formation of α (bcc martensite) along with ε (hcp martensite) in the alloy 1 which appeared to have decline in the shape memory effect. This has been demonstrated by the examination of microstructure and identification of α (bcc martensite) martensite in the alloy 1 as compared to alloy 2

Neutron irradiation effect on thermomechanical properties of shape memory alloys

International Nuclear Information System (INIS)

Abramov, V.Ya.; Ionajtis, R.R.; Kotov, V.V.; Loguntsev, E.N.; Ushakov, V.P.

1996-01-01

Alloys of Ti-Ni, Ti-Ni-Pd, Fe-Mn-Si, Mn-Cu-Cr, Mn-Cu, Cu-Al-Mn, Cu-Al-Ni systems are investigated after irradiation in IVV-2M reactor at various temperatures with neutron fluence of 10 19 - 10 20 cm -2 . The degradation of shape memory effect in titanium nickelide base alloys is revealed after irradiation. Mn-Cu and Mn-Cu-Cr alloys show the best results. Trends in shape memory alloy behaviour depending on irradiation temperature are found. A consideration is given to the possibility of using these alloys for components of power reactor control and protection systems [ru

Xenon focused ion beam in the shape memory alloys investigation – the case of NiTi and CoNiAl

Czech Academy of Sciences Publication Activity Database

Kopeček, Jaromír; Jurek, Karel; Kopecký, Vít; Klimša, Ladislav; Seiner, Hanuš; Sedlák, Petr; Landa, Michal; Dluhoš, J.; Petrenec, M.; Hladík, L.; Doupal, A.; Heczko, Oleg

2014-01-01

Roč. 20, Aug (2014), s. 335-336 ISSN 1431-9276 R&D Projects: GA ČR(CZ) GA14-03044S Institutional support: RVO:68378271 ; RVO:61388998 Keywords : scanning electron microscope * SEM * focused ion beam * FIB * xenon plasma focused ion beam * dual beam * shape memory alloy * SMA Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.877, year: 2014

Influence of Structure and Microstructure on Deformation Localization and Crack Growth in NiTi Shape Memory Alloys

Science.gov (United States)

Paul, Partha P.; Fortman, Margaret; Paranjape, Harshad M.; Anderson, Peter M.; Stebner, Aaron P.; Brinson, L. Catherine

2018-04-01

Porous NiTi shape memory alloys have applications in the biomedical and aerospace fields. Recent developments in metal additive manufacturing have made fabrication of near-net-shape porous products with complicated geometries feasible. There have also been developments in tailoring site-specific microstructures in metals using additive manufacturing. Inspired by these developments, we explore two related mechanistic phenomena in a simplified representation of porous shape memory alloys. First, we computationally elucidate the connection between pore geometry, stress concentration around pores, grain orientation, and strain-band formation during tensile loading of NiTi. Using this, we present a method to engineer local crystal orientations to mitigate the stress concentrations around the pores. Second, we experimentally document the growth of cracks around pores in a cyclically loaded superelastic NiTi specimen. In the areas of stress concentration around holes, cracks are seen to grow in large grains with [1 1 0] oriented along the tensile axis. This combined work shows the potential of local microstructural engineering in reducing stress concentration and increasing resistance to propagation of cracks in porous SMAs, potentially increasing the fatigue life of porous SMA components.

Ti Ni shape memory alloy film-actuated microstructures for a MEMS probe card

Science.gov (United States)

Namazu, Takahiro; Tashiro, Youichi; Inoue, Shozo

2007-01-01

This paper describes the development of a novel silicon (Si) cantilever beam device actuated by titanium-nickel (Ti-Ni) shape memory alloy (SMA) films. A Ti-Ni SMA film can yield high work output per unit volume, so a Ti-Ni film-actuated Si cantilever beam device is a prospective tool for use as a microelectromechanical system (MEMS) probe card that provides a relatively large contact force between the probe and electrode pad in spite of its minute size. Before fabrication of the device, the thermomechanical deformation behavior of Ti-Ni SMA films with various compositions was investigated in order to determine a sufficient constituent film for a MEMS actuator. As a result, Ti-Ni films having a Ti content of 50.2 to 52.6 atomic% (at%) were found to be usable for operation as a room temperature actuator. We have developed a Ti-Ni film-actuated Si cantilever beam device, which can produce a contact force by the cantilever bending when in contact, and also by the shape memory effect (SME) of the Ti-Ni film arising from Joule heating. The SME of the Ti-Ni film can generate an additional average contact force of 200 µN with application of 500 mW to the film. In addition to physical contact, a dependable electric contact between the Au film-coated probe tip and the Al film electrode was achieved. However, the contact resistance exhibited an average value of 25 Ω, which would have to be reduced for practical use. Reliability tests confirmed the durability of the Ti-Ni film-actuated Si cantilever-beam, in that the contact resistance was constant throughout a large number of physical contacts (>104 times).

Shape recovery characteristics of biaxially prestrained Fe-Mn-Si-based shape memory alloy

International Nuclear Information System (INIS)

Wada, M.; Naoi, H.; Yasuda, H.; Maruyama, T.

2008-01-01

Fe-Mn-Si-based shape memory alloy has already been used practically for steel pipe joints. In most of the applications including the steel pipe joints, it is possible to estimate the reduction of diameter from the experimental data of the shape recovery after uniaxial stretching of the alloy materials. However, studies on shape recovery effects after biaxial stretching are important for the extensive applications of the alloy. In this study, we investigated the shape recovery strain after uniaxial and biaxial stretching and the microstructures of the alloy in order to see the effects of uniaxial and biaxial prestrain on the stress-induced martensitic transformation. Amounts of shape recovery strain in the biaxially prestrained specimens are smaller than those in the uniaxially prestrained specimens. Transmission electron microscopy revealed that reverse transformations of stress-induced martensitic ε-phase are prevented by slip bands formed at the same time in the biaxially prestrained specimens, but not in the uniaxially prestrained specimens. The technological data and interpretations presented in this study should be useful in forming design guidelines for promoting the extensive applications of Fe-Mn-Si-based shape memory alloy

Local annealing of shape memory alloys using laser scanning and computer vision

Science.gov (United States)

Hafez, Moustapha; Bellouard, Yves; Sidler, Thomas C.; Clavel, Reymond; Salathe, Rene-Paul

2000-11-01

A complete set-up for local annealing of Shape Memory Alloys (SMA) is proposed. Such alloys, when plastically deformed at a given low temperature, have the ability to recover a previously memorized shape simply by heating up to a higher temperature. They find more and more applications in the fields of robotics and micro engineering. There is a tremendous advantage in using local annealing because this process can produce monolithic parts, which have different mechanical behavior at different location of the same body. Using this approach, it is possible to integrate all the functionality of a device within one piece of material. The set-up is based on a 2W-laser diode emitting at 805nm and a scanner head. The laser beam is coupled into an optical fiber of 60(mu) in diameter. The fiber output is focused on the SMA work-piece using a relay lens system with a 1:1 magnification, resulting in a spot diameter of 60(mu) . An imaging system is used to control the position of the laser spot on the sample. In order to displace the spot on the surface a tip/tilt laser scanner is used. The scanner is positioned in a pre-objective configuration and allows a scan field size of more than 10 x 10 mm2. A graphical user interface of the scan field allows the user to quickly set up marks and alter their placement and power density. This is achieved by computer controlling X and Y positions of the scanner as well as the laser diode power. A SMA micro-gripper with a surface area less than 1 mm2 and an opening of the jaws of 200(mu) has been realized using this set-up. It is electrically actuated and a controlled force of 16mN can be applied to hold and release small objects such as graded index micro-lenses at a cycle time of typically 1s.

Applications and development of shape-memory and superelastic alloys in Japan

Energy Technology Data Exchange (ETDEWEB)

Takaoka, S.; Horikawa, H. [Furukawa Electric Co., Ltd., Hiratsuka (Japan); Kobayashi, J. [Japan Association of Shape Memory Alloys, Yokohama (Japan); Shimizu, K. [Kanazawa Inst. of Tech., Matsutou (Japan)

2002-07-01

The present situation of the applications and development of shape memory and superelastic alloys in Japan will collectively be introduced. Of many shape memory alloys, TiNi alloy systems have mostly been used for the applications from the point of view of fatigue and corrosion characteristics. Shape memory effect has been utilized for mainly thermal actuators with the form of coil springs. The effect associated with the B2 to R-phase transformation and its reversion exhibits recoverable strain of approximately 1%, and after a million thermal cycles the recovery characteristics are not affected. Thus, the effect is widely utilized as sensor flap of the air conditioner, water flow control valve, underfloor vent, automatic oil volume adjusting equipment for Shinkansen and water mixing valve. Another effect associated with the B2 to orthorhombic transformation and its reversion, as in TiNiCu alloys containing Cu more than 8%, can be applied to actuators required for 10,000 to 50,000 times life, and thus it is utilized as rice cooker, coffee maker and anti-scald valve. In Japan, however, the TiNi shape memory alloy systems are mainly used for applications using the superelasticity, like a rubber material. The superelasticity associated with the B2 to monoclinic stress-induced transformation and its reversion upon un-loading has been utilized as brassiere wire, eye glasses flame, antenna core wire for cellular phone and fishing wire, and that associated with the B2 to orthorhombic stress-induced transformation and its reversion upon un-loading has been as orthodontic wire, because the TiNiCu alloy wire exhibits smaller stress hysteresis than that of usual TiNi alloy wire. The TiNi shape memory alloy systems are now developed to make various shapes, such as tapes, foils and tubes, and the alloys with those shapes are examined to apply to medical uses, such as guide wire for catheter and catheter tube itself, and to any other uses. The development in Japan is rapidly

Cold Forming of Ni-Ti Shape Memory Alloy Sheet

Science.gov (United States)

Fann, Kaung-Jau; Su, Jhe-Yung

2018-03-01

Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its further application, this study attempts to investigate the feasibility of cold forming its sheet blank especially under a bi-axial tensile stress state. Not only experiments but also a Finite Element Analysis (FEA) with DEFORM 2D was conducted in this study. The material data for FEA was accomplished by the tensile test. An Erichsen-like cupping test was performed as well to determine the process parameter for experiment setup. As a result of the study, the Ni-Ti shape memory alloy sheet has a low formability for cold forming and shows a relative large springback after releasing the forming load.

Development of an engineering model for ferromagnetic shape memory alloys

International Nuclear Information System (INIS)

Tani, Yoshiaki; Todaka, Takashi; Enokizono, Masato

2008-01-01

This paper presents a relationship among stress, temperature and magnetic properties of a ferromagnetic shape memory alloy. In order to derive an engineering model of ferromagnetic shape memory alloys, we have developed a measuring system of the relationship among stress, temperature and magnetic properties. The samples used in this measurement are Fe68-Ni10-Cr9-Mn7-Si6 wt% ferromagnetic shape memory alloy. They are thin ribbons made by rapid cooling in air. In the measurement, the ribbon sample is inserted into a sample holder winding consisting of the B-coil and compensation coils, and magnetized in an open solenoid coil. The ribbon is stressed with attachment weights and heated with a heating wire. The specific susceptibility was increased by applying tension, and slightly increased by heating below the Curie temperature

Shape memory and superelastic behavior of Ti-7.5Nb-4Mo-1Sn alloy

International Nuclear Information System (INIS)

Zhang, D.C.; Lin, J.G.; Jiang, W.J.; Ma, M.; Peng, Z.G.

2011-01-01

Research highlights: → A Ti-based shape memory alloy, Ti-7.5Nb-4Mo-1Sn, was designed. → The martensitic transformation start temperature of the alloy, M s , is 261 K. → The alloy exhibits good shape memory and superelastic behaviors. → The alloy also shows a good superelastic stability at room temperature. → The Ti-5Mo-7.5Nb-1Sn alloy has a potential application as a biomedical material. -- Abstract: In the present work, a Ti-based shape memory alloy with the composition of Ti-7.5Nb-4Mo-1Sn was designed based on the d-electron orbit theory. The shape memory and superelastic behavior of the alloy were investigated. It is found that the martensitic transformation temperature of the alloy is near 261 K. The tensile and the thermal cycling testing results show that the alloy exhibits the stable shape memory effect and superelasticity at room temperature. The maximum recovered strain of the alloy is 4.83%.

Surface treatment of NiTi shape memory alloy by modified advanced oxidation process

Institute of Scientific and Technical Information of China (English)

CHU Cheng-lin; WANG Ru-meng; YIN Li-hong; PU Yue-pu; DONG Yin-sheng; GUO Chao; SHENG Xiao-bo; LIN Ping-hua; CHU Paul-K

2009-01-01

A modified advanced oxidation process(AOP) utilizing a UV/electrochemically-generated peroxide system was used to fabricate titania films on chemically polished NiTi shape memory alloy(SMA). The microstructure and biomedical properties of the film were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), inductively-coupled plasma mass spectrometry(ICPMS), hemolysis analysis, and blood platelet adhesion test. It is found that the modified AOP has a high processing effectiveness and can result in the formation of a dense titania film with a Ni-free zone near its top surface. In comparison, Ni can still be detected on the outer NiTi surface by the conventional AOP using the UV/H2O2 system. The depth profiles of O, Ni, Ti show that the film possesses a smooth graded interface structure next to the NiTi substrate and this structure enhances the mechanical stability of titania film. The titania film can dramatically reduce toxic Ni ion release and also improve the hemolysis resistance and thromboresistance of biomedical NiTi SMA.

Reversibility in martensitic transformation and shape memory in high Mn ferrous alloys

International Nuclear Information System (INIS)

Tomota, Y.

2000-01-01

The reversibility of austenite (γ : fcc) epsilon (ε : hcp) martensitic transformation and shape memory effect in high Mn ferrous alloys are discussed. A particular emphasis is put on the ε → γ reverse transformation behavior in two poly-crystalline alloys, Fe-24Mn and Fe-24Mn-6Si, where the latter exhibits excellent shape memory while the former shows poor memory although their forward γ → ε transformation behavior is quite similar. TEM in situ observations have revealed that the motion of Shockley partial dislocations during ε → γ reverse transformation is different from each other in these two alloys. The influence of alloying elements on the shape memory effect can be related to solid solution hardening of austenite, suggesting an important role of internal stress. The effect of training on enhancing the shape memory is explained by such an internal stress distribution associated with the formation of very thin, i.e., nano-scale ε/γ lamellae. (orig.)

Thin film shape memory alloys for optical sensing applications

International Nuclear Information System (INIS)

Fu, Y Q; Luo, J K; Huang, W M; Flewitt, A J; Milne, W I

2007-01-01

Based on shape memory effect of the sputtered thin film shape memory alloys, different types of micromirror structures were designed and fabricated for optical sensing application. Using surface micromachining, TiNi membrane mirror structure has been fabricated, which can be actuated based on intrinsic two-way shape memory effect of the free-standing TiNi film. Using bulk micromachining, TiNi/Si and TiNi/Si 3 N 4 microcantilever mirror structures were fabricated

Influence of cold working on deformation behavior and shape memory effect of Ti-Ni-Nb

International Nuclear Information System (INIS)

Okita, K.; Semba, H.; Okabe, N.; Sakuma, T.; Mihara, Y.

2005-01-01

In this study, the influence of cold working on the deformation behavior and the transformation characteristics was investigated on the Ti-Ni-Nb shape memory alloy (SMA). Both the tensile test and the shape recovery test were performed for the wire specimens of 1mm in the diameter with some different rates of cold working. The shape recovery tests were performed for the wire specimens of different cold working rates until the various levels of maximum applied strain, and the reverse-transformation characteristics on the process of heating after unloading were studied. It is clarified that the higher cold-working rate improves the shape memory properties of the alloy. (orig.)

Characteristics and in vitro biological assessment of (Ti, O, N)/Ti composite coating formed on NiTi shape memory alloy

International Nuclear Information System (INIS)

Sun Tao; Wang Langping; Wang Min; Tong, Ho-Wang; Lu, William W.

2011-01-01

In this investigation, plasma immersion ion implantation and deposition (PIIID) was used to fabricate a (Ti, O, N)/Ti coating on NiTi shape memory alloy (SMA) to improve its long-term biocompatibility and wear resistance. The surface morphology, composition and roughness of uncoated and coated NiTi SMA samples were examined. Energy dispersive X-ray elemental mapping of cross-sections of (Ti, O, N)/Ti coated NiTi SMA revealed that Ni was depleted from the surface of coated samples. No Ni was detected by X-ray photoelectron spectroscopy on the surface of coated samples. Furthermore, three-point bending tests showed that the composite coating could undergo large deformation without cracking or delamination. After 1 day cell culture, SaOS-2 cells on coated samples spread better than those on uncoated NiTi SMA samples. The proliferation of SaOS-2 cells on coated samples was significantly higher at day 3 and day 7 of cell culture.

The influence of the substrate on the adhesive strength of the micro-arc oxidation coating developed on TiNi shape memory alloy

Science.gov (United States)

Hsieh, Shy-Feng; Ou, Shih-Fu; Chou, Chia-Kai

2017-01-01

TiNi shape memory alloys (SMAs), used as long-term implant materials, have a disadvantage. Ni-ion release from the alloys may trigger allergies in the human body. Micro-arc oxidation has been utilized to modify the surface of the TiNi SMA for improving its corrosion resistance and biocompatibility. However, there are very few reports investigating the essential adhesive strength between the micro-arc oxidized film and TiNi SMA. Two primary goals were attained by this study. First, Ti50Ni48.5Mo1.5 SMA having a phase transformation temperature (Af) less than body temperature and good shape recovery were prepared. Next, the Ti50Ni50 and Ti50Ni48.5Mo1.5 SMA surfaces were modified by micro-arc oxidation in phosphoric acid by applying relatively low voltages to maintain the adhesive strength. The results indicated that the pore size, film thickness, and P content increased with applied voltage. The micro-arc oxidized film, comprising Ti oxides, Ni oxide, and phosphate compounds, exhibited a glassy amorphous structure. The outmost surface of the micro-arc oxidized film contained a large amount of P (>12 at%) but only a trace of Ni (micro-arc oxidized films exceeded the requirements of ISO 13779. Furthermore, Mo addition into TiNi SMAs was found to be favorable for improving the adhesive strength of the micro-arc oxidized film.

Nanoscale shape-memory alloys for ultrahigh mechanical damping.

Science.gov (United States)

San Juan, Jose; Nó, Maria L; Schuh, Christopher A

2009-07-01

Shape memory alloys undergo reversible transformations between two distinct phases in response to changes in temperature or applied stress. The creation and motion of the internal interfaces between these phases during such transformations dissipates energy, making these alloys effective mechanical damping materials. Although it has been shown that reversible phase transformations can occur in nanoscale volumes, it is not known whether these transformations have a sample size dependence. Here, we demonstrate that the two phases responsible for shape memory in Cu-Al-Ni alloys are more stable in nanoscale pillars than they are in the bulk. As a result, the pillars show a damping figure of merit that is substantially higher than any previously reported value for a bulk material, making them attractive for damping applications in nanoscale and microscale devices.

Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

Science.gov (United States)

Sehitoglu, H.; Alkan, S.

2018-03-01

This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non- Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

Science.gov (United States)

Sehitoglu, H.; Alkan, S.

2018-03-01

This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non-Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

Modelling, characterisation and uncertainties of stabilised pseudoelastic shape memory alloy helical springs

DEFF Research Database (Denmark)

Enemark, Søren; Santos, Ilmar; Savi, M. A.

2016-01-01

The thermo-mechanical behaviour of pseudoelastic shape memory alloy helical springs is of concern discussing stabilised and cyclic responses. Constitutive description of the shape memory alloy is based on the framework developed by Lagoudas and co-workers incorporating two modifications related t...

Synthesis and characterization of Cu–Al–Ni shape memory alloy multilayer thin films

International Nuclear Information System (INIS)

Gómez-Cortés, J.F.; San Juan, J.; López, G.A.; Nó, M.L.

2013-01-01

Among active materials, shape memory alloys are well recognized for their work output density. Because of that, these alloys have attracted much attention to be used in micro/nano electromechanical systems. In the present work, the electron beam evaporation technique has been used to growth, by a multilayer method, two shape memory alloy thin films with different Cu–Al–Ni composition. Multilayers have been further thermally treated to produce the alloys by solid solution diffusion. The produced multilayers have been characterized and the presence of the martensite phase in the obtained thin films was studied. Furthermore, the influence of two different coatings onto the Si substrates, namely Si/SiO 2 and Si/Si 3 N 4 , was investigated. Mechanically stable, not detaching from the substrates, Cu–Al–Ni shape memory alloy thin films, about 1 micrometre thick, showing a martensitic transformation have been produced. - Highlights: ► Multilayer thin films of Cu–Al–Ni shape memory alloys produced by e-beam evaporation. ► SiN X 200 nm thick coating is good for high quality Cu–Al–Ni shape memory thin films. ► Thermal treatment renders Cu–Al–Ni multilayer in homogeneous martensite thin film

First Principles Modelling of Shape Memory Alloys Molecular Dynamics Simulations

CERN Document Server

Kastner, Oliver

2012-01-01

Materials sciences relate the macroscopic properties of materials to their microscopic structure and postulate the need for holistic multiscale research. The investigation of shape memory alloys is a prime example in this regard. This particular class of materials exhibits strong coupling of temperature, strain and stress, determined by solid state phase transformations of their metallic lattices. The present book presents a collection of simulation studies of this behaviour. Employing conceptually simple but comprehensive models, the fundamental material properties of shape memory alloys are qualitatively explained from first principles. Using contemporary methods of molecular dynamics simulation experiments, it is shown how microscale dynamics may produce characteristic macroscopic material properties. The work is rooted in the materials sciences of shape memory alloys and  covers  thermodynamical, micro-mechanical  and crystallographical aspects. It addresses scientists in these research fields and thei...

Formability of Annealed Ni-Ti Shape Memory Alloy Sheet

Science.gov (United States)

Fann, K. J.; Su, J. Y.; Chang, C. H.

2018-03-01

Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its application, this study attempts to investigate the strength and cold formability of its sheet blank, which is annealed at various temperatures, by hardness test and by Erichsen-like cupping test. As a result, the higher the annealing temperature, the lower the hardness, the lower the maximum punch load as the sheet blank fractured, and the lower the Erichsen-like index or the lower the formability. In general, the Ni-Ti sheet after annealing has an Erichsen-like index between 8 mm and 9 mm. This study has also confirmed via DSC that the Ni-Ti shape memory alloy possesses the austenitic phase and shows the superelasticity at room temperature.

Modeling of mechanical properties for ferrous shape memory alloy

International Nuclear Information System (INIS)

Wada, Manabu; Ide, Yusuke; Mizote, Shinichiro; Naoi, Hisashi; Tsukimori, Kazuyuki

2002-08-01

In order to acquire technical data that are necessary for manufacture and design of the simulation test device for analyzing the core mechanics of Fast Breeder Reactor, ferrous shape memory alloy of Fe-28%Mn-6%Si-5%Cr is melted, forged and heat-treated. The microstructures are austenite. The specimens are deformed of up to 16% work-strain by tensile and compressive test, resulting in appearance of epsilon-martensite that is induced by stress. Then, heating at 673K for 10 minutes causes austenitic transformation from epsilon-martensite and shape memory strains are measured. We also investigate shape memory character of specimens, which are given, so called 'training treatment' of 5% pre-strain and recovery heat treatment. As a result, there is little difference between tensile and compressive test without training treatment and shape memory strain is 2% after being given 5% work-strain and recovery heat treatment. On the other hand, training treatment is remarkable and shape memory strain reaches to 3.7% after 5% work-strain. We analyze shape recovery character of this alloy specimen at three-point bending by using finite element method, and indicate possibility that its deformation behavior can be estimated from mechanical properties' data obtained at tensile and compressive test. (author)

A comprehensive energy approach to predict fatigue life in CuAlBe shape memory alloy

International Nuclear Information System (INIS)

Sameallah, S; Kadkhodaei, M; Legrand, V; Saint-Sulpice, L; Arbab Chirani, S

2015-01-01

Stabilized dissipated energy is an effective parameter on the fatigue life of shape memory alloys (SMAs). In this study, a formula is proposed to directly evaluate the stabilized dissipated energy for different values of the maximum and minimum applied stresses, as well as the loading frequency, under cyclic tensile loadings. To this aim, a one-dimensional fully coupled thermomechanical constitutive model and a cycle-dependent phase diagram are employed to predict the uniaxial stress-strain response of an SMA in a specified cycle, including the stabilized one, with no need of obtaining the responses of the previous cycles. An enhanced phase diagram in which different slopes are defined for the start and finish of a backward transformation strip is also proposed to enable the capture of gradual transformations in a CuAlBe shape memory alloy. It is shown that the present approach is capable of reproducing the experimental responses of CuAlBe specimens under cyclic tensile loadings. An explicit formula is further presented to predict the fatigue life of CuAlBe as a function of the maximum and minimum applied stresses as well as the loading frequency. Fatigue tests are also carried out, and this formula is verified against the empirically predicted number of cycles for failure. (paper)

A comprehensive energy approach to predict fatigue life in CuAlBe shape memory alloy

Science.gov (United States)

Sameallah, S.; Legrand, V.; Saint-Sulpice, L.; Kadkhodaei, M.; Arbab Chirani, S.

2015-02-01

Stabilized dissipated energy is an effective parameter on the fatigue life of shape memory alloys (SMAs). In this study, a formula is proposed to directly evaluate the stabilized dissipated energy for different values of the maximum and minimum applied stresses, as well as the loading frequency, under cyclic tensile loadings. To this aim, a one-dimensional fully coupled thermomechanical constitutive model and a cycle-dependent phase diagram are employed to predict the uniaxial stress-strain response of an SMA in a specified cycle, including the stabilized one, with no need of obtaining the responses of the previous cycles. An enhanced phase diagram in which different slopes are defined for the start and finish of a backward transformation strip is also proposed to enable the capture of gradual transformations in a CuAlBe shape memory alloy. It is shown that the present approach is capable of reproducing the experimental responses of CuAlBe specimens under cyclic tensile loadings. An explicit formula is further presented to predict the fatigue life of CuAlBe as a function of the maximum and minimum applied stresses as well as the loading frequency. Fatigue tests are also carried out, and this formula is verified against the empirically predicted number of cycles for failure.

Shape recovery mechanism observed in single crystals of shape memory alloys

Czech Academy of Sciences Publication Activity Database

Seiner, Hanuš; Sedlák, Petr; Landa, Michal

2008-01-01

Roč. 81, č. 6 (2008), s. 537-551 ISSN 0141-1594 Institutional research plan: CEZ:AV0Z20760514 Keywords : shape memory alloys * shape recovery process * martensitic microstructure * non-classical boundaries Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.201, year: 2008

A nonlocal continuum model for the biaxial buckling analysis of composite nanoplates with shape memory alloy nanowires

Science.gov (United States)

Farajpour, M. R.; Shahidi, A. R.; Farajpour, A.

2018-03-01

In this study, the buckling behavior of a three-layered composite nanoplate reinforced with shape memory alloy (SMA) nanowires is examined. Whereas the upper and lower layers are reinforced with typical nanowires, SMA nanoscale wires are used to strengthen the middle layer of the system. The composite nanoplate is assumed to be under the action of biaxial compressive loading. A scale-dependent mathematical model is presented with the consideration of size effects within the context of the Eringen’s nonlocal continuum mechanics. Using the one-dimensional Brinson’s theory and the Kirchhoff theory of plates, the governing partial differential equations of SMA nanowire-reinforced hybrid nanoplates are derived. Both lateral and longitudinal deflections are taken into consideration in the theoretical formulation and method of solution. In order to reduce the governing differential equations to their corresponding algebraic equations, a discretization approach based on the differential quadrature method is employed. The critical buckling loads of the hybrid nanosystem with various boundary conditions are obtained with the use of a standard eigenvalue solver. It is found that the stability response of SMA composite nanoplates is strongly sensitive to the small scale effect.

Attitude Control of Nanosatellites by Paddle Motion Using Elastic Hinges Actuated by Shape Memory Alloy

Science.gov (United States)

Iai, Masafumi; Durali, Mohammad; Hatsuzawa, Takeshi

Recent research has been extending the applications of small satellites called microsatellites, nanosatellites, or picosatellites. To further improve capability of those satellites, a lightweight, active attitude-control mechanism is needed. This paper proposes a concept of inertial orientation control, an attitude control method using movable solar arrays. This method is made suitable for nanosatellites by the use of shape memory alloy (SMA)-actuated elastic hinges and a simple maneuver generation algorithm. The combination of SMA and an elastic hinge allows the hinge to remain lightweight and free of frictional or rolling contacts. Changes in the shrinking and stretching speeds of the SMA were measured in a vacuum chamber. The proposed algorithm constructs a maneuver to achieve arbitrary attitude change by repeating simple maneuvers called unit maneuvers. Provided with three types of unit maneuvers, each degree of freedom of the satellite can be controlled independently. Such construction requires only simple calculations, making it a practical algorithm for a nanosatellite with limited computational capability. In addition, power generation variation caused by maneuvers was analyzed to confirm that a maneuver from any initial attitude to an attitude facing the sun was justifiable in terms of the power budget.

Shape memory effect and superelasticity of titanium nickelide alloys implanted with high ion doses

International Nuclear Information System (INIS)

Pogrebnjak, A D; Bratushka, S N; Beresnev, V M; Levintant-Zayonts, N

2013-01-01

The state of the art in ion implantation of superelastic NiTi shape memory alloys is analyzed. Various technological applications of the shape memory effect are outlined. The principles and techiques of ion implantation are described. Specific features of its application for modification of surface layers in surface engineering are considered. Key properties of shape memory alloys and problems in utilization of ion implantation to improve the surface properties of shape memory alloys, such as corrosion resistance, friction coefficient, wear resistance, etc. are discussed. The bibliography includes 162 references

Laser shock wave assisted patterning on NiTi shape memory alloy surfaces

Science.gov (United States)

Seyitliyev, Dovletgeldi; Li, Peizhen; Kholikov, Khomidkhodza; Grant, Byron; Karaca, Haluk E.; Er, Ali O.

2017-02-01

An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. Scanning electron microscope (SEM) and optical microscope images of square pattern with different sizes were studied. One dimensional profile analysis shows that the depth of the patterned sample initially increase linearly with the laser energy until 125 mJ/pulse where the plasma further absorbs and reflects the laser beam. In addition, light the microscope image show that the surface of NiTi alloy was damaged due to the high power laser energy which removes the graphite layer.

Multi-scale analysis of the fatigue of shape memory alloys

International Nuclear Information System (INIS)

Zheng, Lin

2016-01-01

Shape Memory Alloy (SMA) is a typical smart material having many applications from aerospace industry, mechanical and civil engineering, to biomedical devices, where the material's fatigue is a big concern. One of the challenging issues in studying the fatigue behaviors of SMA polycrystals is the interaction between the material damage and the martensitic phase transformation which takes place in a macroscopic homogeneous mode or a heterogeneous mode (forming macroscopic patterns (Luders-like bands) due to the localized deformations and localized heating/cooling). Such pattern formation and evolution imply the governing physical mechanisms in the material system such as the fatigue process, but there is still no fatigue study of SMAs by tracing the macro-band patterns and the local material responses. To bridge this gap, systematic tensile fatigue experiments are conducted on pseudo-elastic NiTi polycrystalline strips by in-situ optical observation on the band-pattern evolutions and by tracing the deformation history of the cyclic phase transformation zones where fatigue failure occurs. These experimental results help to better understand the stress- and frequency-dependent fatigue behaviors. Particularly, it is found that the local residual strain rather than the structural nominal/global residual strain is a good indicator on the material's damage leading to the fatigue failure, which is important for understanding and modeling the fatigue process in SMAs. (author)

Microstructure, martensitic transformation, mechanical and shape memory properties of Ni–Co–Mn–In high-temperature shape memory alloys under different heat treatments

International Nuclear Information System (INIS)

Yang, Shuiyuan; Wang, Cuiping; Shi, Zhan; Wang, Jinming; Zhang, Jinbin; Huang, Yixiong; Liu, Xingjun

2016-01-01

The microstructure, martensitic transformation behavior, mechanical and shape memory properties of Ni 40 Co 10 Mn 41+x In 9−x (x=0, 2 and 4) high-temperature shape memory alloys annealed at 900 °C for 24 h or at 800 °C for 2 h were investigated, respectively. The tetragonal martensite phase and fcc γ phase are observed in all the studied alloys. The reversible martensitic transformation temperatures of the alloys increase with the increases of the electron concentration and the tetragonality of martensite phase. The amount of γ phase gradually increases with the decrease of In content, and much more γ phase in the alloys annealed at 900 °C results in slightly larger compressive fracture strain. Although the alloys with x=0 and 2 have a mass of γ phase, they still exhibit good shape memory properties. The amount of γ phase reaches about 20% in the alloy with x=0 after annealed at 900 °C, but a full recovery strain of 3.6% and a two-way shape memory effect of 0.8% can be obtained after two thermomechanical cycles.

Shape memory effect in Fe-Mn-Ni-Si-C alloys with low Mn contents

Energy Technology Data Exchange (ETDEWEB)

Min, X.H., E-mail: MIN.Xiaohua@nims.go.jp [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Sawaguchi, T.; Ogawa, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Maruyama, T. [Awaji Materia Co., Ltd. 2-3-13, Kanda ogawamachi, Chiyoda, Tokyo 101-0052 (Japan); Yin, F.X. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Tsuzaki, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki 305-0047 (Japan)

2011-06-15

Highlights: {yields} A class of new Fe-Mn-Ni-Si-C shape memory alloys with low Mn contents has been designed. {yields} A Mn content for the onset of the {alpha}' martensite is less than 13 mass%, and the {epsilon} martensite still exists in the alloy with a 9 mass% Mn. {yields} The shape recovery strain decreases considerably when the Mn content is reduced from 13 to 11 mass%. {yields} The sudden decrease in the shape recovery strain is mainly caused by the formation of {alpha}' martensite. - Abstract: An attempt was made to develop a new Fe-Mn-Si-based shape memory alloy from a Fe-17Mn-6Si-0.3C (mass%) shape memory alloy, which was previously reported to show a superior shape memory effect without any costly training treatment, by lowering its Mn content. The shape memory effect and the phase transformation behavior were investigated for the as-solution treated Fe-(17-2x)Mn-6Si-0.3C-xNi (x = 0, 1, 2, 3, 4) polycrystalline alloys. The shape recovery strain exceeded 2% in the alloys with x = 0-2, which is sufficient for an industrially applicable shape memory effect; however, it suddenly decreased in the alloys between x = 2 and 3 although the significant shape recovery strain still exceeded 1%. In the alloys with x = 3 and 4, X-ray diffraction analysis and transmission electron microscope observation revealed the existence of {alpha}' martensite, which forms at the intersection of the {epsilon} martensite plates and suppresses the crystallographic reversibility of the {gamma} austenite to {epsilon} martensitic transformation.

Nonlinear dynamics of a pseudoelastic shape memory alloy system - theory and experiment

DEFF Research Database (Denmark)

Enemark, Søren; A Savi, M.; Santos, Ilmar

2014-01-01

In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping capabilit...

Vibration control of a flexible rotor suspended by shape memory alloy wires

DEFF Research Database (Denmark)

Alves, Marco Túlio Santana; Steffen Jr., Valder; Castro dos Santos, Marina

2018-01-01

The present contribution is devoted to the study of the influence of shape memory alloys on the dynamic behavior of flexible rotors. In this sense, a suspension composed by pseudoelastic shape memory alloy wires that are connected to a rotor-bearing test rig was designed. To evaluate the performa...

Local atomic and crystal structure rearrangement during the martensitic transformation in Ti50Ni25Cu25 shape memory alloy

International Nuclear Information System (INIS)

Menushenkov, Alexey; Grishina, Olga; Shelyakov, Alexander; Yaroslavtsev, Alexander; Zubavichus, Yan; Veligzhanin, Alexey; Bednarcik, Jozef; Chernikov, Roman; Sitnikov, Nikolay

2014-01-01

Highlights: • Local crystalline structure of TiNiCu SMA is investigated using EXAFS. • Peculiarities of Ni and Cu local environment are found. • Ti atoms show greater mobility relative to Ni atoms. • Ni local environment change is significant for shape memory effect. -- Abstract: The changes of crystal structure and local crystalline environment of Ti, Ni and Cu atoms in Ti 50 Ni 25 Cu 25 shape memory alloy are investigated using X-ray diffraction and extended X-ray absorption fine structure spectroscopy (EXAFS) in temperature range of martensite transformation. The analysis of the EXAFS-spectra shows that the bonds involving Ni atoms have the highest degree of disorder and the change in the local environment around Ni atoms is significant for the occurrence of the shape memory effect, while Cu atoms occupy the normal positions in the crystallographic structure and have the lowest displacement amplitude leading to the stabilization of both phases

Recovery and residual stress of SMA wires and applications for concrete structures

International Nuclear Information System (INIS)

Choi, Eunsoo; Cho, Sung-Chul; Park, Taehyo; Hu, Jong Wan; Chung, Young-Soo

2010-01-01

In general, NiTi shape memory alloys are used for applications in civil structures. NiTi SMAs show good superelasticity and shape memory effect properties. However, for application of the shape memory effect, it is desirable for SMAs to show a wide temperature hysteresis, especially for civil structures which are exposed to severe environmental conditions. NiTiNb SMAs, in general, show a wider temperature hysteresis than NiTi SMAs and are more applicable for civil structures. This study examines the temperature hysteresis of NiTiNb and NiTi SMAs, and their recovery and residual stress are investigated. In addition, the tensile behaviors of SMA wires under residual stress are evaluated. This study explains the possible applications for concrete structures with the shape memory effect and illustrates two experimental results of concrete cylinders and reinforced concrete columns. For both tests, SMA wires of NiTiNb and NiTi are used to confine concrete using residual stress. The SMA wire jackets on the concrete cylinders increase the peak strength and the ductility compared to the plain concrete cylinders. In addition, the SMA wire jackets on reinforced concrete columns increase the ductility greatly without flexural strength degradation

Tracking Control of Shape-Memory-Alloy Actuators Based on Self-Sensing Feedback and Inverse Hysteresis Compensation

Directory of Open Access Journals (Sweden)

Shu-Hung Liu

2009-12-01

Full Text Available Shape memory alloys (SMAs offer a high power-to-weight ratio, large recovery strain, and low driving voltages, and have thus attracted considerable research attention. The difficulty of controlling SMA actuators arises from their highly nonlinear hysteresis and temperature dependence. This paper describes a combination of self-sensing and model-based control, where the model includes both the major and minor hysteresis loops as well as the thermodynamics effects. The self-sensing algorithm uses only the power width modulation (PWM signal and requires no heavy equipment. The method can achieve high-accuracy servo control and is especially suitable for miniaturized applications.

Synthesis and characterization of Cu–Al–Ni shape memory alloy multilayer thin films

Energy Technology Data Exchange (ETDEWEB)

Gómez-Cortés, J.F. [Dpt. Física Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain); San Juan, J., E-mail: jose.sanjuan@ehu.es [Dpt. Física Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain); López, G.A.; Nó, M.L. [Dpt. Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain)

2013-10-01

Among active materials, shape memory alloys are well recognized for their work output density. Because of that, these alloys have attracted much attention to be used in micro/nano electromechanical systems. In the present work, the electron beam evaporation technique has been used to growth, by a multilayer method, two shape memory alloy thin films with different Cu–Al–Ni composition. Multilayers have been further thermally treated to produce the alloys by solid solution diffusion. The produced multilayers have been characterized and the presence of the martensite phase in the obtained thin films was studied. Furthermore, the influence of two different coatings onto the Si substrates, namely Si/SiO{sub 2} and Si/Si{sub 3}N{sub 4}, was investigated. Mechanically stable, not detaching from the substrates, Cu–Al–Ni shape memory alloy thin films, about 1 micrometre thick, showing a martensitic transformation have been produced. - Highlights: ► Multilayer thin films of Cu–Al–Ni shape memory alloys produced by e-beam evaporation. ► SiN{sub X} 200 nm thick coating is good for high quality Cu–Al–Ni shape memory thin films. ► Thermal treatment renders Cu–Al–Ni multilayer in homogeneous martensite thin film.

Miniature High Force, Long Stroke Linear Shape Memory Alloy Actuators, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Shape Memory Alloys (SMAs) are metal alloys (Nickel-Titanium, for example) that change shape when heated. When drawn and processed in wire form, the shape change is...

Powder-metallurgy preparation of NiTi shape-memory alloy using mechanical alloying and spark-plasma sintering.

Czech Academy of Sciences Publication Activity Database

Novák, P.; Moravec, H.; Vojtěch, V.; Knaislová, A.; Školáková, A.; Kubatík, Tomáš František; Kopeček, Jaromír

2017-01-01

Roč. 51, č. 1 (2017), s. 141-144 ISSN 1580-2949 R&D Projects: GA ČR(CZ) GA14-03044S Institutional support: RVO:61389021 ; RVO:68378271 Keywords : mechanical alloying * spark plasma sintering * NiTi * shape memory alloy Subject RIV: JG - Metallurgy; JG - Metallurgy (FZU-D) OBOR OECD: Materials engineering ; Materials engineering (FZU-D) Impact factor: 0.436, year: 2016 https://www.researchgate.net/publication/313900224_Powder-metallurgy_preparation_of_NiTi_shape-memory_alloy_using_mechanical_alloying_and_spark-plasma_sintering

Finite Element Analysis of the Pseudo-elastic Behavior of Shape Memory Alloy Truss and Beam

Directory of Open Access Journals (Sweden)

Kamal M. Bajoria

2010-07-01

Full Text Available The pseudo-elastic behavior of Shape memory alloy (SMA truss and cantilever beam are investigated. Brinson’s one-dimensional material model, which uses the twinned and detwinned martensite fractions separately as internal variables, is applied in the algorithm to establish the SMA stress-strain characteristics. This material model also incorporates different young’s modulus for austenitic and martensite phase to represent the true SMA characteristics. In this model, a cosine function was used to express the evolution of the stress induced martensite fractions during the forward and reverse martensite phase transformation. A finite element formulation for the SMA truss member considering the geometric nonlinearity is proposed and the results are compared with the corresponding linear analysis. As a step forward, a finite element formulation for an SMA cantilever beam with an applied end moment is proposed. The load displacement characteristic for both the loading and unloading phases are considered to check the full pseudo-elastic hysteretic loop. In the numerical investigation, the stress-strain variation along the beam depth is also examined during the loading and unloading process to investigate the forward and reverse martensite phase transformation phenomena. Newton-Raphson’s iterative method is applied to get convergence to the equilibrium for each loading steps. During a complete loading-unloading process, the temperature is kept constant as the model is essentially an isothermal model. Numerical simulation is performed considering two different temperatures to demonstrate the effect of temperature on the hysteretic loop.

Effect of adding Si on shape memory effect in Co-Ni alloy system

Energy Technology Data Exchange (ETDEWEB)

Zhou Weimin [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China); Liu Yan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Jiang Bohong [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)]. E-mail: bhjiang@sjtu.edu.cn; Zhou Pingnan [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

2006-11-25

In this paper, the effect of adding Si to Co-31.5 mass% Ni alloys on fcc-hcp martensitic transformation is investigated. The Co-Ni-Si ternary alloys with different amount of Si from 1 to 5 mass% were prepared. The stacking fault probability of Co-Ni-Si polycrystalline alloys were determined by X-ray diffraction profile analysis and compared with the binary Co-Ni alloy. The results show that the stacking fault probability of the fcc phase of alloys increases with increasing Si content. The effect of Si on phase transformation and shape memory behavior is evaluated. The experimental results show that both the critical strength and the shape memory effect of the ternary alloys will increase by the addition of Si. The improvement mechanism of the shape memory effect by adding Si to binary Co-Ni alloys is discussed.

Formation of two-way shape memory effect in rapid-quenched TiNiCu alloys

International Nuclear Information System (INIS)

Shelyakov, A.V.; Bykovsky, Yu.A.; Matveeva, N.M.; Kovneristy, Yu.K.

1995-01-01

Recently we have developed a number of devices for an optical radiation control based on the shape memory effect. A blind of rapid-quenched TiNiCu alloy having a two-way shape memory in bending was used as a basic element. So far as the rapid quenched alloy used is amorphous in initial state, it needs thermal annealing to form shape memory. This paper describes procedure of thermo-mechanical treatment, that allows to form desired two-way shape memory immediately during thermal annealing of amorphous alloy without training. It was shown that degree of two-way shape recovery depends critically on initial strain, temperature and duration of the annealing. It was experimentally determined optimum parameters of thermo-mechanical treatment to achieve maximum two-way shape memory. (orig.)

Adaptive and energy efficient SMA-based handling systems

Science.gov (United States)

Motzki, P.; Kunze, J.; Holz, B.; York, A.; Seelecke, S.

2015-04-01

Shape Memory Alloys (SMA's) are known as actuators with very high energy density. This fact allows for the construction of very light weight and energy-efficient systems. In the field of material handling and automated assembly process, the avoidance of big moments of inertia in robots and kinematic units is essential. High inertial forces require bigger and stronger robot actuators and thus higher energy consumption and costs. For material handling in assembly processes, many different individual grippers for various work piece geometries are used. If one robot has to handle different work pieces, the gripper has to be exchanged and the assembly process is interrupted, which results in higher costs. In this paper, the advantages of using high energy density Shape Memory Alloy actuators in applications of material-handling and gripping-technology are explored. In particular, light-weight SMA actuated prototypes of an adaptive end-effector and a vacuum-gripper are constructed via rapid-prototyping and evaluated. The adaptive end-effector can change its configuration according to the work piece geometry and allows the handling of multiple different shaped objects without exchanging gripper tooling. SMA wires are used to move four independent arms, each arm adds one degree of freedom to the kinematic unit. At the tips of these end-effector arms, SMA-activated suction cups can be installed. The suction cup prototypes are developed separately. The flexible membranes of these suction cups are pulled up by SMA wires and thus a vacuum is created between the membrane and the work piece surface. The self-sensing ability of the SMA wires are used in both prototypes for monitoring their actuation.

Wafer-level integration of NiTi shape memory alloy on silicon using Au–Si eutectic bonding

International Nuclear Information System (INIS)

Gradin, Henrik; Bushra, Sobia; Braun, Stefan; Stemme, Göran; Van der Wijngaart, Wouter

2013-01-01

This paper reports on the wafer level integration of NiTi shape memory alloy (SMA) sheets with silicon substrates through Au–Si eutectic bonding. Different bond parameters, such as Au layer thicknesses and substrate surface treatments were evaluated. The amount of gold in the bond interface is the most important parameter to achieve a high bond yield; the amount can be determined by the barrier layers between the Au and Si or by the amount of Au deposition. Deposition of a gold layer of more than 1 μm thickness before bonding gives the most promising results. Through patterning of the SMA sheet and by limiting bonding to small areas, stresses created by the thermal mismatch between Si and NiTi are reduced. With a gold layer of 1 μm thickness and bond areas between 200 × 200 and 800 × 800 μm 2 a high bond strength and a yield above 90% is demonstrated. (paper)

Emergency repair of severely damaged reinforced concrete columns using active confinement with shape memory alloys

International Nuclear Information System (INIS)

Shin, Moochul; Andrawes, Bassem

2011-01-01

This experimental study focuses on investigating the feasibility of utilizing spirals made of shape memory alloys (SMAs) to conduct emergency repair on severely damaged reinforced concrete (RC) columns. The thermally triggered shape memory feature of SMAs is sought in this study, to apply active confinement pressure on the column's damaged region. Two severely damaged 1/3-scale RC columns are repaired using the proposed technique and tested under a quasi-static lateral cyclic load. The repair of each column is conducted in less than 15 h, and the columns are tested 24 h after the starting of the repair process. The experimental results show that the new repair technique is successful in either fully restoring the as-built lateral strength, stiffness, and flexural ductility of the columns or making them even better. The efficacy of the proposed repair technique is mainly attributed to the ability of the SMA spirals to apply and maintain active confining pressure on the damaged region of the columns, which increases the strength of the already damaged concrete and delays its damage

Thermodynamic analysis of the effect of annealing on the thermal stability of a Cu–Al–Ni–Mn shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Mazzer, E.M., E-mail: ericmazzer@gmail.com [Postgraduate Program in Materials Science and Engineering, Federal University of São Carlos, São Carlos, SP (Brazil); Kiminami, C.S.; Bolfarini, C.; Cava, R.D.; Botta, W.J.; Gargarella, P. [Department of Materials Engineering, Federal University of São Carlos, São Carlos, SP (Brazil)

2015-05-20

Highlights: • We evaluated the effect of annealing on a Cu-based shape memory alloy. • Stabilization was clarified in terms of the chemical and non-chemical energies. • Stabilization was related to the shift of transformations temperatures. • Insights into the role of stabilization of phases by thermodynamics approach. - Abstract: Shape memory alloys (SMA) usually exhibit shifts in the transformation temperatures with increasing the number of thermal cycles. These shifts result from an increased stability of the martensite during cycling and have an important role in the functionality of the material. The structural reasons for these changes are not fully understood and are investigated here by a thermodynamic approach. The variation in the transformation temperatures and in the chemical and non-chemical energy terms of the total energy involved in the transformation of a Cu–Al–Ni–Mn SMA was studied. Powder of this alloy was produced by gas atomization with size in the range of 32–45 μm and subsequently heat-treated at 180 °C, 250 °C and 300 °C during different times. The as-cast and heat-treated samples were investigated by differential scanning calorimetry, X-ray diffraction and scanning and transmission electron microscopy. Only a single martensitic β′ phase was formed at room temperature. It was observed an increase in the austenitic start transformation temperature (A{sub s}) as well as in the austenitic finish transformation temperature (A{sub f}) with increasing the annealing time and temperature. The shift in the transformation temperatures to higher values is attributed to a decrease of the latent heat of transformation and non-chemical energy term, caused by changes in the structural order of the martensite. This study shows that the variation of the transformation temperatures is strongly linked to the total energy components, which can give important information about the stability of the alloy.

Factors influencing shape memory effect and phase transformation behaviour of Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Li, H.; Dunne, D.; Kennon, N.

1999-01-01

The objective of this research work was to investigate the factors influencing the shape memory effect and phase transformation behaviour of three Fe-Mn-Si based shape memory alloys: Fe-28Mn-6Si, Fe-13Mn-5Si-10Cr-6Ni and Fe-20Mn-6Si-7Cr-1Cu. The research results show that the shape memory capacity of Fe-Mn-Si based shape memory alloys varies with annealing temperature, and this effect can be explained in terms of the effect of annealing on γ ε transformation. The nature and concentration of defects in austenite are strongly affected by annealing conditions. A high annealing temperature results in a low density of stacking faults, leading to a low nucleation rate during stress induced γ→ε transformation. The growth of ε martensite plates is favoured rather than the formation of new ε martensite plates. Coarse martensite plates produce high local transformation strains which can be accommodated by local slip deformation, leading to a reduction in the reversibility of the martensitic transformation and to a degradation of the shape memory effect. Annealing at low temperatures (≤673 K) for reasonable times does not eliminate complex defects (dislocation jogs, kinks and vacancy clusters) created by hot and cold working strains. These defects can retard the movement and rearrangement of Shockley partial dislocations, i.e. suppress γ→ε transformation, also leading to a degradation of shape memory effect. Annealing at about 873 K was found to be optimal to form the dislocation structures which are favourable for stress induced martensitic transformation, thus resulting in the best shape memory behaviour. (orig.)

Magnetic Shape Memory Alloy Actuator for Instrument Applications

Data.gov (United States)

National Aeronautics and Space Administration — This project will develop a simple actuator based on magnetic shape memory alloy (MSMA), a novel new family of crystalline materials which exhibit strain deformation...

Shape memory effect of Fe-14% Mn-6% Si-9% Cr-6% Ni alloy polycrystals

International Nuclear Information System (INIS)

Inagaki, Hirosuke

1992-01-01

Factors affecting the shape memory effect in Fe-14% Mn-6% Si-9% Cr-6% Ni alloy polycrystals were studied in detail. It was found that the shape memory effect in this alloy was most influenced by the amount of deformation. With increasing amount of deformation, the shape memory effect diminished appreciably. Although the fraction of the initial dimensional change that could be restored was about 45% in the specimen strained by 4%, only 21% of the initial dimensional change was recovered in the specimen strained by 9%. Temperatures of deformation were found to be also an important factor that affected the shape memory effect. The maximum shape memory effect was observed in the specimens strained at temperatures between the M s and M d temperatures. In this alloy, however, specimens strained at temperatures below the M s temperature indicated a relatively large shape memory effect, too. It was further found that the shape memory effect was appreciably intensified by repeated straining and annealing, especially when straining was performed at 500deg C. It was suggested that the shape memory effect in Fe base alloys was strongly influenced by the dislocation substructure present in the starting material. (orig.) [de

Stress recovery and cyclic behaviour of an Fe-Mn-Si shape memory alloy after multiple thermal activation

Science.gov (United States)

Hosseini, E.; Ghafoori, E.; Leinenbach, C.; Motavalli, M.; Holdsworth, S. R.

2018-02-01

The stress recovery and cyclic deformation behaviour of Fe-17Mn-5Si-10Cr-4Ni-1(V,C) shape memory alloy (Fe-SMA) strips, which are often used for pre-stressed strengthening of structural members, were studied. The evolution of recovery stress under different constraint conditions was studied. The results showed that the magnitude of the tensile stress in the Fe-SMA member during thermal activation can have a signification effect on the final recovery stress. The higher the tensile load in the Fe-SMA (e.g., caused by dead load or thermal expansion of parent structure during heating phase), the lower the final recovery stress. Furthermore, this study investigated the cyclic behaviour of the activated SMA followed by a second thermal activation. Although the magnitude of the recovery stress decreased during the cyclic loading, the second thermal activation could retrieve a significant part of the relaxed recovery stress. This observation suggests that the relaxation of recovery stress during cyclic loading is due to a reversible phase transformation-induced deformation (i.e., forward austenite-to-martensite transformation) rather than an irreversible dislocation-induced plasticity. Retrieval of the relaxed recovery stress by the reactivation process has important practical implications as the prestressing loss in pre-stressed civil structures can be simply recovered by reheating of the Fe-SMA elements.

Development of a non-explosive release actuator using shape memory alloy wire.

Science.gov (United States)

Yoo, Young Ik; Jeong, Ju Won; Lim, Jae Hyuk; Kim, Kyung-Won; Hwang, Do-Soon; Lee, Jung Ju

2013-01-01

We have developed a newly designed non-explosive release actuator that can replace currently used release devices. The release mechanism is based on a separation mechanism, which relies on segmented nuts and a shape memory alloy (SMA) wire trigger. A quite fast and simple trigger operation is made possible through the use of SMA wire. This actuator is designed to allow a high preload with low levels of shock for the solar arrays of medium-size satellites. After actuation, the proposed device can be easily and instantly reset. Neither replacement, nor refurbishment of any components is necessary. According to the results of a performance test, the release time, preload capacity, and maximum shock level are 50 ms, 15 kN, and 350 G, respectively. In order to increase the reliability of the actuator, more than ten sets of performance tests are conducted. In addition, the proposed release actuator is tested under thermal vacuum and extreme vibration environments. No degradation or damage was observed during the two environment tests, and the release actuator was able to operate successfully. Considering the test results as a whole, we conclude that the proposed non-explosive release actuator can be applied reliably to intermediate-size satellites to replace existing release systems.

Combining thermodynamic principles with Preisach models for superelastic shape memory alloy wires

International Nuclear Information System (INIS)

Doraiswamy, S; Rao, A; Srinivasa, A R

2011-01-01

We present a simple model for simulating the response of a superelastic shape memory alloy wire based on the thermodynamics of irreversible processes, which can simulate the full thermomechanical response including internal hysteresis loops, at different temperatures, with minimal data input. The key idea is to separate the dissipative response and the elastic response of shape memory alloys using a Gibbs potential based formulation, and then use a Preisach model for the dissipative part of the response. This enables better handling of the features observed in the superelastic response such as those due to changes in temperature and internal hysteresis loops. We compare the predicted response with experiments performed on 0.75 mm NiTi shape memory alloy wires at three different temperatures

Dynamical Behavior of a Pseudoelastic Vibration Absorber Using Shape Memory Alloys

Directory of Open Access Journals (Sweden)

Hugo De S. Oliveira

2017-01-01

Full Text Available The tuned vibration absorber (TVA provides vibration reduction of a primary system subjected to external excitation. The idea is to increase the number of system degrees of freedom connecting a secondary system to the primary system. This procedure promotes vibration reduction at its design forcing frequency but two new resonance peaks appear introducing critical behaviors that must be avoided. The use of shape memory alloys (SMAs can improve the performance of the classical TVA establishing an adaptive TVA (ATVA. This paper deals with the nonlinear dynamics of a passive pseudoelastic tuned vibration absorber with an SMA element. In this regard, a single degree of freedom elastic oscillator is used to represent the primary system, while an extra oscillator with an SMA element represents the secondary system. Temperature dependent behavior of the system allows one to change the system response avoiding undesirable responses. Nevertheless, hysteretic behavior introduces complex characteristics to the system dynamics. The influence of the hysteretic behavior due to stress-induced phase transformation is investigated. The ATVA performance is evaluated by analyzing primary system maximum vibration amplitudes for different forcing amplitudes and frequencies. Numerical simulations establish comparisons of the ATVA results with those obtained from the classical TVA. A parametric study is developed showing the best performance conditions and this information can be useful for design purposes.

Nonlinear dynamics of a pseudoelastic shape memory alloy system—theory and experiment

International Nuclear Information System (INIS)

Enemark, S; F Santos, I; A Savi, M

2014-01-01

In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping capabilities and varying stiffness. Besides, these properties depend on the temperature and pretension conditions. Because of these capabilities, shape memory alloys are interesting in relation to engineering design of dynamic systems. A theoretical model based on a modification of the 1D Brinson model was established. Basically, the hardening and the sub-loop behaviour were altered. The model parameters were extracted from force–displacement tests of the spring at different constant temperatures as well as from differential scanning calorimetry. Model predictions were compared with experimental results of free and forced vibrations of the system setup under different temperature conditions. The experiments give a thorough insight into dynamic systems involving pseudoelastic shape memory alloys. Comparison between experimental results and the proposed model shows that the model is able to explain and predict the overall nonlinear behaviour of the system. (paper)

Shape memory and pseudoelastic properties of Fe-Mn-Si and Ti-Ni based alloys

International Nuclear Information System (INIS)

Guenin, G.

1997-01-01

The aim of this presentation is to analyse and discuss some recent advances in shape memory and pseudoelastic properties of different alloys. Experimental work in connection with theoretical ones will be reviewed. The first part is devoted to the microstructural origin of shape memory properties of Fe-Mn-Si based alloys (γ-ε transformation); the second part is a synthetic analysis of the effects of thermomechanical treatments on shape memory and pseudoelastic effects in Ti-Ni alloys, with some focus on the behaviour of the R phase introduced. (orig.)

Shape memory alloy actuation for a variable area fan nozzle

Science.gov (United States)

Rey, Nancy; Tillman, Gregory; Miller, Robin M.; Wynosky, Thomas; Larkin, Michael J.; Flamm, Jeffrey D.; Bangert, Linda S.

2001-06-01

The ability to control fan nozzle exit area is an enabling technology for next generation high-bypass-ratio turbofan engines. Performance benefits for such designs are estimated at up to 9% in thrust specific fuel consumption (TSFC) relative to current fixed-geometry engines. Conventionally actuated variable area fan nozzle (VAN) concepts tend to be heavy and complicated, with significant aircraft integration, reliability and packaging issues. The goal of this effort was to eliminate these undesirable features and formulate a design that meets or exceeds leakage, durability, reliability, maintenance and manufacturing cost goals. A Shape Memory Alloy (SMA) bundled cable actuator acting to move an array of flaps around the fan nozzle annulus is a concept that meets these requirements. The SMA bundled cable actuator developed by the United Technologies Corporation (Patents Pending) provides significant work output (greater than 2200 in-lb per flap, through the range of motion) in a compact package and minimizes system complexity. Results of a detailed design study indicate substantial engine performance, weight, and range benefits. The SMA- based actuation system is roughly two times lighter than a conventional mechanical system, with significant aircraft direct operating cost savings (2-3%) and range improvements (5-6%) relative to a fixed-geometry nozzle geared turbofan. A full-scale sector model of this VAN system was built and then tested at the Jet Exit Test Facility at NASA Langley to demonstrate the system's ability to achieve 20% area variation of the nozzle under full scale aerodynamic loads. The actuator exceeded requirements, achieving repeated actuation against full-scale loads representative of typical cruise as well as greater than worst-case (ultimate) aerodynamic conditions. Based on these encouraging results, work is continuing with the goal of a flight test on a C-17 transport aircraft.

Engineering design framework for a shape memory alloy coil spring actuator using a static two-state model

International Nuclear Information System (INIS)

An, Sung-Min; Cho, Kyu-Jin; Ryu, Junghyun; Cho, Maenghyo

2012-01-01

A shape memory alloy (SMA) coil spring actuator is fabricated by annealing an SMA wire wound on a rod. Four design parameters are required for the winding: the wire diameter, the rod diameter, the pitch angle and the number of active coils. These parameters determine the force and stroke produced by the actuator. In this paper, we present an engineering design framework to select these parameters on the basis of the desired force and stoke. The behavior of the SMA coil spring actuator is described in detail to provide information about the inner workings of the actuator and to aid in selecting the design parameters. A new static two-state model, which represents a force–deflection relation of the actuator at the fully martensitic state (M 100% ) and fully austenitic state (A 100% ), is derived for use in the design. Two nonlinear effects are considered in the model: the nonlinear detwinning effect of the SMA and the nonlinear geometric effect of the coil spring for large deformations. The design process is organized into six steps and is presented with a flowchart and design equations. By following this systematic approach, an SMA coil spring actuator can be designed for various applications. Experimental results verified the static two-state model for the SMA coil spring actuator and a case study showed that an actuator designed using this framework met the design requirements. The proposed design framework was developed to assist application engineers such as robotics researchers in designing SMA coil spring actuators without the need for full thermomechanical models. (paper)

An experimental and analytical study on the feasibility of SMA spring driven actuation of an iris mechanism

International Nuclear Information System (INIS)

Rajan, Aravindh; Abouseada, Mostafa; Manghaipathy, Pavithra; Ozalp, Nesrin; Majid, Feras Abdul; Salem, Ayman; Srinivasa, Arun

2016-01-01

Highlights: • An iris mechanism proposed in response to fluctuations in solar energy. • Iris motion controlled with the use of Nickel–Titanium Shape Memory Alloy springs. • Variation of the force exerted by SMA spring w.r.t. temperature tested experimentally. • An analytical expression that relates the aperture area and crank rotation is given. • SMA springs showed promising actuation mechanism as a replacement to motor. - Abstract: Variation in incoming solar energy adversely affects the temperature inside a solar reactor and lowers its efficiency. Therefore, it is important to develop a mechanism that can maintain semi-constant temperatures inside the reactor from sunrise to sunset. In this paper, we present an iris mechanism that reduces or enlarges its circular opening with the use of Nickel–Titanium Shape Memory Alloy (SMA) springs. SMA springs possess memory of their shapes at certain temperatures. Hence, by controlling the temperature of the spring, it is possible to exert different forces that may then be transferred to the variable aperture mechanism. In this study, variation of the force exerted by an SMA spring with respect to temperature was experimentally tested and the viability of an SMA spring’s use in actuating an iris mechanism aperture was examined. In order to simulate conditions under fluctuating solar radiation, a 7 kW solar simulator was used in experiments at varying power levels. It was observed that SMA springs are promising as a replacement of the actuation mechanism driven by a motor.

Deposition of Chitosan Layers on NiTi Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Kowalski P.

2015-04-01

Full Text Available The NiTi shape memory alloys have been known from their application in medicine for implants as well as parts of medical devices. However, nickel belongs to the family of elements, which are toxic. Apart from the fact that nickel ions are bonded with titanium into intermetallic phase, their presence may cause allergy. In order to protect human body against release of nickel ions a surface of NiTi alloy can be modified with use of titanium nitrides, oxides or diamond-like layers. On the one hand the layers can play protective role but on the other hand they may influence shape memory behavior. Too stiff or too brittle layer can lead to limiting or completely blocking of the shape recovery. It was the reason to find more elastic covers for NiTi surface protection. This feature is characteristic for polymers, especially, biocompatible ones, which originate in nature. In the reported paper, the chitosan was applied as a deposited layer on surface of the NiTi shape memory alloy. Due to the fact that nature of shape memory effect is sensitive to thermo and/or mechanical treatments, the chitosan layer was deposited with use of electrophoresis carried out at room temperature. Various deposition parameters were checked and optimized. In result of that thin chitosan layer (0.45µm was received on the NiTi alloy surface. The obtained layers were characterized by means of chemical and phase composition, as well as surface quality. It was found that smooth, elastic surface without cracks and/or inclusions can be produced applying 10V and relatively short deposition time - 30 seconds.

Damage evolution during actuation fatigue in shape memory alloys (SPIE Best Student Paper Award)

Science.gov (United States)

Phillips, Francis R.; Wheeler, Robert; Lagoudas, Dimitris C.

2018-03-01

Shape Memory Alloys (SMAs) are unique materials able to undergo a thermomechanically induced, reversible phase transformation. Additionally, SMA are subject to two types of fatigue, that is structural fatigue due to cyclic loading as experienced by most materials, as well as actuation fatigue due to repeated thermally induced phase transformation. The evolution of multiple material characteristics is presented over the actuation fatigue lifetime of NiTiHf actuators, including the accumulation of irrecoverable strain, the evolution of internal voids, and the evolution of the effective modulus of the actuator. The results indicate that all three of these material characteristics are clearly interconnected and careful analysis of each of these characteristics can help to understand the evolution of the others, as well as help to understand how actuation fatigue leads to ultimate failure of the actuator.

Effects of Hydrogen Charging on the Phase Transformation of Martensitic NiTi Shape Memory Alloy Wires

Science.gov (United States)

Snir, Yoav; Carl, Matthew; Ley, Nathan A.; Young, Marcus L.

2017-12-01

Ti-rich martensitic NiTi shape memory alloy (SMA) wires of 0.5 mm diameter were tested under hydrogen-charging conditions to reveal the effects on phase transformation. Hydrogen charging was performed by immersion testing for several durations. The SMA wires were characterized by differential scanning calorimetry (DSC), scanning electron microscopy with energy dispersive spectroscopy, and synchrotron radiation X-ray diffraction (SR-XRD) for the the as-received, polished, and hydrogen-charged conditions. The DSC revealed the phase-transformation behavior of the NiTi SMA wires. Single and triple heating/cooling cycles in the DSC show the relationship between hydrogen and temperature on the material. Five distinct peaks (peaks I-V) are observed during heating/cooling in the DSC. Peak I corresponds to the martensite-to-austenite (M → A) transformation. Peaks II, III, and IV are related to hydrogen charging. Peak II appears at about 210-230 °C, while peaks III and IV appear at about 350 and 440 °C, respectively. These higher temperature peaks, peaks II-IV, were observed for the first time for a martensitic NiTi SMA due to the large temperature range covered using the DSC. Only one peak (peak V) appears during cooling and corresponds to the austenite-to-martensite transformation peak. Ex situ and in situ SR-XRD revealed the phases and the crystallographic relationship to peaks I-V in the DSC.

Role of samarium additions on the shape memory behavior of iron based alloys

International Nuclear Information System (INIS)

Shakoor, R.A.; Khalid, F. Ahmad; Kang, Kisuk

2011-01-01

Research highlights: → The effect of samarium contents on shape memory behavior has been studied. → Addition of samarium increases the strength, c/a ratio and ε (hcp martensite). → Addition of samarium retards the nucleation of α (bcc martensite). → Improvement in shape memory effect with the increase in samarium contents. - Abstract: The effect of samarium contents on shape memory behavior of iron based shape memory alloys has been studied. It is found that the strength of the alloys increases with the increase in samarium contents. This effect can be attributed to the solid solution strengthening of austenite by samarium addition. It is also noticed that the shape memory effect increases with the increase in samarium contents. This improvement in shape memory effect presumably can be regarded as the effect of improvement in strength, increase in c/a ratio and obstruction of nucleation of α in the microstructure.

Magnetocaloric effect in Heusler shape-memory alloys

International Nuclear Information System (INIS)

Planes, A.; Manosa, Ll.; Moya, X.; Krenke, T.; Acet, M.; Wassermann, E.F.

2007-01-01

We present a comparative study of the magnetocaloric properties of Ni-Mn-X Heusler shape-memory alloys with X=Ga, Sn and In. In these materials, the magnetocaloric effect is a consequence of the magnetostructural coupling that enables the magnetic shape-memory properties. We show that inverse magnetocaloric effects can occur in these materials. The origin of this anomalous behavior is different in stoichiometric Ni 2 MnGa and in Ni-Mn-Sn/In. In the former case it is related to the strong uniaxial magnetic anisotropy of the martensitic phase, while in the later it is an intrinsic effect associated with an incipient antiferromagnetism

Knowledge and method base for shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Welp, E.G.; Breidert, J. [Ruhr-University Bochum, Institute of Engineering Design, 44780 Bochum (Germany)

2004-05-01

It is often impossible for design engineers to decide whether it is possible to use shape memory alloys (SMA) for a particular task. In case of a decision to use SMA for product development, design engineers normally do not know in detail how to proceed in a correct and beneficial way. In order to support design engineers who have no previous knowledge about SMA and to assist in the transfer of results from basic research to industrial practice, an essential knowledge and method base has been developed. Through carefully conducted literature studies and patent analysis material and design information could be collected. All information is implemented into a computer supported knowledge and method base that provides design information with a particular focus on the conceptual and embodiment design phase. The knowledge and method base contains solution principles and data about effects, material and manufacturing as well as design guidelines and calculation methods for dimensioning and optimization. A browser-based user interface ensures that design engineers have immediate access to the latest version of the knowledge and method base. In order to ensure a user friendly application, an evaluation with several test users has been carried out. Reactions of design engineers from the industrial sector underline the need for support related to knowledge on SMA. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] Fuer Konstrukteure ist es haeufig schwierig zu entscheiden, ob sich der Einsatz von Formgedaechtnislegierungen (FGL) fuer eine bestimmte Aufgabe eignet. Fuer den Fall, dass FGL fuer die Produktentwicklung genutzt werden sollen, besitzen Ingenieure zumeist nur unzureichende Detailkenntnisse, um Formgedaechtnislegierungen richtig und in vorteilhafter Weise anwenden zu koennen. Zur Unterstuetzung von Konstrukteuren, die ueber kein Vorwissen und keine Erfahrungen zu FGL verfuegen und zum Transfer von Forschungsergebnissen in die industrielle Praxis, ist eine

On the hydrodynamic characterization of a passive Shape Memory Alloy valve

International Nuclear Information System (INIS)

Waddell, A.M.; Punch, J.; Stafford, J.; Jeffers, N.

2015-01-01

An attractive approach to the thermal management of next generation photonics devices (heat fluxes > 10 2  W/cm 2 ) is micro-channel cooling, and micro-valves will be required for refined flow control in the supporting micro-fluidic systems. In this paper, a NiTi Shape Memory Alloy (SMA) micro-valve design for passive flow control and thermal management was prototyped at the macro scale and hydrodynamically characterized. The dynamic behavior of the valve was observed and the loss coefficient (ζ v ) derived from pressure-flow measurements. The hydrodynamic characterization study is important because ζ v is sensitive to Re and geometry in the flow regime of the micro-fluidic system. Static replicas of the SMA valve geometry were tested for low Re (110–220) and a range of opening ratios (β) in a ø1 mm miniature channel. The loss coefficients were found to be sensitive to flow rate and decreased rapidly with an increase in Re. A correlation was developed to interpolate ζ v from a given Re and β. The valve loss coefficients obtained in this work are important parameters in the modeling and design of future micro-fluidic cooling systems. - Highlights: • A miniature normally closed passive SMA valve for micro-fluidic cooling of Photonics devices is demonstrated in this paper. • The passive dynamic behaviour of the valve in response to temperature change is observed. • The design is hydrodynamically characterized through pressure-flow measurements. • A correlation for head loss across the valve as a function of Re and blockage ratio is presented

Thermo-Mechanical Behavior and Shakedown of Shape Memory Alloy Cable Structures

Science.gov (United States)

Biggs, Daniel B.

Shape memory alloys (SMAs) are a versatile class of smart materials that exhibit adaptive properties which have been applied to solve engineering problems in wide-ranging fields from aerospace to biomedical engineering. Yet there is a lack of understanding of the fundamental nature of SMAs in order to effectively apply them to challenging problems within these engineering fields. Stranding fine NiTi wires into a cable form satisfies the demands of many aerospace and civil engineering applications which require actuators to withstand large tensile loads. The impact of increased bending and twisting in stranded NiTi wire structures, as well as introducing contact mechanics to the unstable phase transformation is not well understood, and this work aims to fill that void. To study the scalability of NiTi cables, thermo-mechanical characterization tests are conducted on cables much larger than those previously tested. These cables are found to have good superelastic properties and repeatable cyclic behavior with minimal induced plasticity. The behavior of additional cables, which have higher transition temperatures that can be used in a shape memory mode as thermo-responsive, high force actuator elements, are explored. These cables are found to scale up the performance of straight wire by maintaining an equivalent work output. Moreover, this work investigates the degradation of the thermal actuation of SMA wires through novel stress-temperature paths, discovering several path dependent behaviors of transformation-induced plasticity. The local mechanics of NiTi cable structures are explored through experiments utilizing digital image correlation, revealing new periodic transformation instabilities. Finite element simulations are presented, which indicate that the instabilities are caused by friction and relative sliding between wires in a cable. Finally, a study of the convective heat transfer of helical wire involving a suite of wind tunnel experiments, numerical

Shape memory alloys as damping materials

International Nuclear Information System (INIS)

Humbeeck, J. van

2000-01-01

Shape memory alloys are gaining an increased interest as passive as well as active damping materials. This damping ability when applied in structural elements can lead to a better noise control, improved life time and even better performance of the envisaged tools. By passive damping, it is understood that the material converts a significant part of unwanted mechanical energy into heat. This mechanical energy can be a (resonance) vibration, impact loading or shock waves. This high damping capacity finds its origin in the thermoelastic martensitic phase due to the hysteretic mobility of martensite-variants or different phase interfaces. The damping capacity increases with increasing amplitude of the applied vibration or impact and is almost frequency independent. Special interest exists moreover for damping extreme large displacements by applying the mechanical hysteresis performed during pseudoelastic loading. This aspect is nowadays very strongly studied as a tool for protecting buildings against earthquakes in seismic active regions. Active damping can be obtained in hybrid composites by controlling the recovery stresses or strains of embedded shape memory alloy wires. This controls the internal energy fo a structure which allows controlled modal modification and tuning of the dynamical properties of structural elements. But also impact damage, acoustic radiation, dynamic shape control can be actively controlled. As a consequence improved fatigue-resistance, better performance and a longer lifetime of the structural elements can be obtained. (orig.)

Nonlinear angle control of a sectioned airfoil by using shape memory alloys

Directory of Open Access Journals (Sweden)

Abreu G.

2014-01-01

Full Text Available The present work illustrates an application of shape memory alloys and nonlinear controller applied to the active angular control of a sectioned airfoil. The main objective of the proposed control system is to modify the shape of the profile based on a reference angle. The change of the sectioned airfoil angle is resultant by the effect of shape memory of the alloy due to heating of the wire caused by an electric current that changes its temperature by Joule effect. Considering the presence of plant’s nonlinear effects, especially in the mathematical model of the alloy, this work proposes the application of an on-off control system.

Modeling size effects on the transformation behavior of shape memory alloy micropillars

International Nuclear Information System (INIS)

Hernandez, Edwin A Peraza; Lagoudas, Dimitris C

2015-01-01

The size dependence of the thermomechanical response of shape memory alloys (SMAs) at the micro and nano-scales has gained increasing attention in the engineering community due to existing and potential uses of SMAs as solid-state actuators and components for energy dissipation in small scale devices. Particularly, their recent uses in microelectromechanical systems (MEMS) have made SMAs attractive options as active materials in small scale devices. One factor limiting further application, however, is the inability to effectively and efficiently model the observed size dependence of the SMA behavior for engineering applications. Therefore, in this work, a constitutive model for the size-dependent behavior of SMAs is proposed. Experimental observations are used to motivate the extension of an existing thermomechanical constitutive model for SMAs to account for the scale effects. It is proposed that such effects can be captured via characteristic length dependent material parameters in a power-law manner. The size dependence of the transformation behavior of NiFeGa micropillars is investigated in detail and used as model prediction cases. The constitutive model is implemented in a finite element framework and used to simulate and predict the response of SMA micropillars with different sizes. The results show a good agreement with experimental data. A parametric study performed using the calibrated model shows that the influence of micropillar aspect ratio and taper angle on the compression response is significantly smaller than that of the micropillar average diameter. It is concluded that the model is able to capture the size dependent transformation response of the SMA micropillars. In addition, the simplicity of the calibration and implementation of the proposed model make it practical for the design and numerical analysis of small scale SMA components that exhibit size dependent responses. (paper)

Effect of alloying elements on the shape memory properties of ductile Cu-Al-Mn alloys

International Nuclear Information System (INIS)

Sutou, Y.; Kainuma, R.; Ishida, K.

1999-01-01

The effect of alloying elements on the M s temperature, ductility and the shape memory properties of Cu-Al-Mn ductile shape memory (SM) alloys was investigated by differential scanning calorimetry, cold-rolling and tensile test techniques. It was found that the addition of Au, Si and Zn to the Cu 73 -Al 17 -Mn 10 alloy stabilized the martensite (6M) phase increasing the M s temperature, while the addition of Ag, Co, Cr, Fe, Ni, Sn and Ti decreased the stability of the martensite phase, decreasing the M s temperature. The SM properties were improved by the addition of Co, Ni, Cr and Ti. (orig.)

Numerical and Experimental Investigation on Aerodynamic Characteristics of SMA Actuated Smart Wing Model

OpenAIRE

Iyyappan Balaguru; Sathiavelu Sendhilkumar

2013-01-01

Due to the advancements in smart actuators, morphing (changing) of aircraft wings has been investigated by increasing number of researchers in recent years. In this research article, the concept of morphing is introduced to the conventional aircraft wing model with the utilization of Shape memory alloys (SMAs). An actuating mechanism is developed and built inside the aircraft wing model along with the SMA actuators which is used to morph its shape. The aircraft wing model with the SMA actuati...

Thermodynamic assessment of the stabilization effect in deformed shape memory alloy martensite

International Nuclear Information System (INIS)

Kato, Hiroyuki; Yasuda, Yohei; Sasaki, Kazuaki

2011-01-01

When a martensitic shape memory alloy is deformed, the reverse transformation occurs at higher temperature than that of undeformed martensite. This is a typical case of the stabilization effect of martensite that is commonly observed in shape memory alloys. Regarding previous results measured by electric resistance and/or dilatometoric methods in NiTi and CuAlNi shape memory alloys, this study has performed calorimetric measurement in these alloys in order to re-examine the stabilization effect in terms of thermodynamics. Experimental evidence for appreciable changes in the reverse transformation temperature due to variant change of the martensite is presented. The elastic energy stored in the deformed martensite and the irreversible energy dissipated during the reverse transformation are estimated from the transformation temperatures, the stress-strain curves of the martensite and the latent heat of transformation. The temperatures of the reverse martensitic transformation have been related to these energies in explicit form.

Effect of tellurium on machinability and mechanical property of CuAlMnZn shape memory alloy

International Nuclear Information System (INIS)

Liu Na; Li Zhou; Xu Genying; Feng Ze; Gong Shu; Zhu Lilong; Liang Shuquan

2011-01-01

Highlights: → A novel free-machining Cu-7.5Al-9.7Mn-3.4Zn-0.3Te (wt.%) shape memory alloy has been developed. → The size of dispersed particles with richer Te is 2-5 μm. → The CuAlMnZnTe alloy has good machinability which approached that of BZn15-24-1.5 due to the addition of Te. → Its shape memory property keeps the same as that of CuAlMnZn alloy with free Te. → The CuAlMnZn shape memory alloy with and without Te both have good ductile as annealed at 700 deg. C for 15 min. - Abstract: The microstructure transition, shape memory effect, machinability and mechanical property of the CuAlMnZn alloy with and without Te have been studied using X-ray diffraction analysis, chips observation and scanning electron microscopy (SEM), tensile strength test and differential scanning calorimeter (DSC), and semi-quantitative shape memory effect (SME) test. The particles with richer Te dispersedly distributed in grain interior and boundary with size of 2-5 μm. After the addition of Te, the CuAlMnZnTe alloy machinability has been effectively increased to approach that of BZn15-24-1.5 and its shape memory property remains the same as the one of CuAlMnZn alloy. The CuAlMnZn shape memory alloys with and without Te both have good ductility as annealed at 700 deg. C for 15 min.

Study of a Ti Ni-based shape memory alloy aiming applications in pipeline connections of the oil and gas industry; Estudo de uma liga base Ti-Ni com memoria de forma visando aplicacoes em conexoes de tubulacoes na industria do petroleo e gas

Energy Technology Data Exchange (ETDEWEB)

Silva, M.M. da; Silva, N.J. da; Gomes, A.A.C.; Reis, R.P.B.; Araujo, C.J. de; Santos, M.A. dos [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Lab. Multidisciplinar de Materiais e Estruturas Ativas (LaMMEA)], e-mail: carlos@dem.ufcg.edu.br

2006-07-01

The objective of this paper is to study the technical feasibility of a TiNi-based Shape Memory Alloy (SMA) with potential application in connections of the oil and gas Sector. The employment of this alloy would increase the reliability of these unions. Thus, a 45,0 Ti-55,0 Ni (% wt) SMA has been manufactured through the plasma skull melting and with subsequent conformation by the Push-Pull method. Samples of this SMA were heat treated at 1173 K during 900s, followed by water quenching. These samples were characterized by optic microscopy, microhardness, differential scanning calorimetry (DSC), and force generation tests. The obtained TiNi SMA has presented an important wide temperature hysteresis. The generated forces substantiate the potential application of these alloys in connection systems of the oil and gas Sector. (author)

Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

Science.gov (United States)

Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

2016-01-01

CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

Investigation on low velocity impact resistance of SMA composite material

Science.gov (United States)

Hu, Dianyin; Zhang, Long; Wang, Rongqiao; Zhang, Xiaoyong

2016-04-01

A method to improve low velocity impact resistance of aeroengine composite casing using shape memory alloy's properties of shape memory(SM) and super-elasticity(SE) is proposed in this study. Firstly, a numerical modeling of SMA reinforced composite laminate under low velocity impact load with impact velocity of 10 m/s is established based on its constitutive model implemented by the VUMAT subroutine of commercial software ABAQUS. Secondly, the responses of SMA composite laminate including stress and deflection distributions were achieved through transient analysis under low velocity impact load. Numerical results show that both peak stress and deflection values of SMA composite laminate are less than that without SMA, which proves that embedding SMA into the composite structure can effectively improve the low velocity impact performance of composite structure. Finally, the influence of SM and SE on low velocity impact resistance is quantitatively investigated. The values of peak stress and deflection of SMA composite based on SM property decrease by 18.28% and 9.43% respectively, compared with those without SMA, instead of 12.87% and 5.19% based on SE. In conclusion, this proposed model described the impact damage of SMA composite structure and turned to be a more beneficial method to enhance the impact resistance by utilizing SM effect.

Effect of titanium addition on shape memory effect and recovery stress of training-free cast Fe–Mn–Si–Cr–Ni shape memory alloys

International Nuclear Information System (INIS)

Wang, Gaixia; Peng, Huabei; Sun, Panpan; Wang, Shanling; Wen, Yuhua

2016-01-01

The shape memory effect and recovery stress of cast Fe–17.2Mn–5.28Si–9.8Cr–4.57Ni (18Mn) and Fe–17.5Mn–5.29Si–9.68Cr–4.2Ni–0.09Ti (18Mn–Ti) alloys have been investigated by optical microscopy, scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and resistivity–temperature curves. The cast 18Mn and 18Mn–Ti alloys solidified as the ferritic mode for which liquid phase fully transforms into primary δ ferrite. The role of titanium is to indirectly refine the austenite through refining the primary δ ferrite. In this case, the austenitic grains of the cast 18Mn alloy were much bigger than that of the cast 18Mn–Ti alloy, although the two alloys underwent δ→γ phase transformation. Grain refinement suppresses the stress-induced ε martensitic transformation, and thus the shape memory effect of the cast 18Mn–Ti alloy is worse than that of the cast 18Mn alloy. On the contrary, the maximum recovery stress and the recovery stress at room temperature are higher for the cast 18Mn–Ti alloy annealed at 1073 K for 30 min than for the cast 18Mn alloy annealed at 973 K for 30 min, because grain refinement suppresses the relaxation of recovery stress caused by the plastic deformation and the stress-induced ε martensitic transformation during cooling process. It is difficult to obtain the training-free cast Fe–Mn–Si based shape memory alloys with excellent shape memory effect and high recovery stress only by grain refinement.

Shape memory alloy fixator system for suturing tissue in minimal access surgery.

Science.gov (United States)

Xu, W; Frank, T G; Stockham, G; Cuschieri, A

1999-01-01

A new technique for suturing human tissue is described in which tissue closure is achieved by means of small fixators made from shape memory alloy. The aim of the development is to provide an alternative to thread suturing in minimal access surgery, which is quicker and requires less skill to achieve the required suturing quality. The design of the fixators is described in terms of the thermal shape recovery of shape memory alloy and a novel form of finite element analysis, which uses a nonlinear elastic element for the material property. Thermal analysis of the fixators and surrounding tissue is used to predict the temperature distribution during and after the application of electric current heating. This was checked in an in vitro experiment, which confirmed that deployment caused no detectable collateral damage to surrounding tissue. In vivo animal studies on the use of the shape memory alloy fixator for suturing tissue are ongoing to establish safety and healing effects.

Static critical phenomena in Co-Ni-Ga ferromagnetic shape memory alloy

International Nuclear Information System (INIS)

Sethi, Brahmananda; Sarma, S.; Srinivasan, A.; Santra, S. B.

2014-01-01

Ferromagnetic shape memory alloys are smart materials because they exhibit temperature driven shape memory effect and magnetic field induced strain. Thus two types of energy, i.e. thermal and magnetic, are used to control their shape memory behaviour. Study of critical phenomenon in such materials has received increased experimental and theoretical attention for better understanding of the magnetic phase transition behavior as well as further development of ferromagnetic shape memory materials. In the present study we report the preparation and characterization of bulk Co 45 Ni 25 Ga 30 alloy, prepared by a sequence of arc melting technique followed by homogenization at 1150 °C for 24 hours and ice-water quenching. Structural and magnetic properties of the alloys were studied by means of X-ray diffraction and vibrating sample magnetometer in an applied field range of ±18 kOe equipped with a high temperature oven. We have determined the critical temperature T C (∼375.5 K) and the critical exponents viz; β=0.40, γ=1.68 and δ=5.2. Asymptotic critical exponents β, γ, and δ obey Widom scaling relation, γ+β=βδ, and the magnetization data satisfy the scaling equation of state for second-order phase transition in the asymptotic critical region

Effect of Ternary Addition of Iron on Shape Memory Characteristics of Cu-Al Alloys

Science.gov (United States)

Raju, T. N.; Sampath, V.

2011-07-01

The effect of alloying Cu-Al alloys with Fe on their transformation temperatures and shape memory properties was investigated by differential scanning calorimetry and bend test. It was found that the minor additions of iron resulted in change of transformation temperatures and led to excellent shape memory properties of the alloys. Since the transformation temperatures are high, they are an ideal choice for high-temperature applications.

SMA bellows as reversible thermal sensors/actuators

International Nuclear Information System (INIS)

Damanpack, A R; Bodaghi, M; Liao, W H

2015-01-01

In this paper, the feasibility of reversible bellows made of shape memory alloys (SMAs) in sensory and actuated applications to transfer pressure and/or temperature into a linear motion is investigated. An analytical three-dimensional model is developed to simulate key features of SMAs including martensitic transformation, reorientation of martensite variants, the shape memory effect, and pseudo-elasticity. Axisymmetric two-dimensional theory of thermo-inelasticity based on the non-linear Green–Lagrange strain tensor is employed to derive the equilibrium equations. A finite element method along with an iterative incremental elastic-predictor–inelastic-corrector procedure is developed to solve the governing equations with both material and geometrical non-linearities. The feasibility of reversible SMA bellows in transferring pressure and/or temperature into a linear motion is numerically demonstrated. In this respect, the effects of geometric parameters, magnitude of thermo-mechanical loadings and end conditions on the performances of SMA bellows are evaluated and discussed in depth. This study provides pertinent results toward an efficient and reliable design of reversible thermally-driven SMA bellows. (paper)

A 3D finite-strain-based constitutive model for shape memory alloys accounting for thermomechanical coupling and martensite reorientation

Science.gov (United States)

Wang, Jun; Moumni, Ziad; Zhang, Weihong; Xu, Yingjie; Zaki, Wael

2017-06-01

The paper presents a finite-strain constitutive model for shape memory alloys (SMAs) that accounts for thermomechanical coupling and martensite reorientation. The finite-strain formulation is based on a two-tier, multiplicative decomposition of the deformation gradient into thermal, elastic, and inelastic parts, where the inelastic deformation is further split into phase transformation and martensite reorientation components. A time-discrete formulation of the constitutive equations is proposed and a numerical integration algorithm is presented featuring proper symmetrization of the tensor variables and explicit formulation of the material and spatial tangent operators involved. The algorithm is used for finite element analysis of SMA components subjected to various loading conditions, including uniaxial, non-proportional, isothermal and adiabatic loading cases. The analysis is carried out using the FEA software Abaqus by means of a user-defined material subroutine, which is then utilized to simulate a SMA archwire undergoing large strains and rotations.

Structural acoustic response of a shape memory alloy hybrid composite panel (lessons learned)

Science.gov (United States)

Turner, Travis L.

2002-07-01

This study presents results from an effort to fabricate a shape memory alloy hybrid composite (SMAHC) panel specimen and test the structure for dynamic response and noise transmission characteristics under the action of thermal and random acoustic loads. A method for fabricating a SMAHC laminate with bi-directional SMA reinforcement is described. Glass-epoxy unidirectional prepreg tape and Nitinol ribbon comprise the material system. Thermal activation of the Nitinol actuators was achieved through resistive heating. The experimental hardware required for mechanical support of the panel/actuators and for establishing convenient electrical connectivity to the actuators is presented. Other experimental apparatus necessary for controlling the panel temperature and acquiring structural acoustic data are also described. Deficiency in the thermal control system was discovered in the process of performing the elevated temperature tests. Discussion of the experimental results focuses on determining the causes for the deficiency and establishing means for rectifying the problem.

Three-dimensional modeling for deformation of austenitic NiTi shape memory alloys under high strain rate

Science.gov (United States)

Yu, Hao; Young, Marcus L.

2018-01-01

A three-dimensional model for phase transformation of shape memory alloys (SMAs) during high strain rate deformation is developed and is then calibrated based on experimental results from an austenitic NiTi SMA. Stress, strain, and martensitic volume fraction distribution during high strain rate deformation are simulated using finite element analysis software ABAQUS/standard. For the first time, this paper presents a theoretical study of the microscopic band structure during high strain rate compressive deformation. The microscopic transformation band is generated by the phase front and leads to minor fluctuations in sample deformation. The strain rate effect on phase transformation is studied using the model. Both the starting stress for transformation and the slope of the stress-strain curve during phase transformation increase with increasing strain rate.

Development and Testing of a Shape Memory Alloy-Driven Composite Morphing Radiator

Science.gov (United States)

Walgren, P.; Bertagne, C.; Wescott, M.; Benafan, O.; Erickson, L.; Whitcomb, J.; Hartl, D.

2018-01-01

Future crewed deep space missions will require thermal control systems that can accommodate larger fluctuations in temperature and heat rejection loads than current designs. To maintain the crew cabin at habitable temperatures throughout the entire mission profile, radiators will be required to exhibit turndown ratios (defined as the ratio between the maximum and minimum heat rejection rates) as high as 12:1. Potential solutions to increase radiator turndown ratios include designs that vary the heat rejection rate by changing shape, hence changing the rate of radiation to space. Shape memory alloys exhibit thermally driven phase transformations and thus can be used for both the control and actuation of such a morphing radiator with a single active structural component that transduces thermal energy into motion. This work focuses on designing a high-performance composite radiator panel and investigating the behavior of various SMA actuators in this application. Three designs were fabricated and subsequently tested in a relevant thermal vacuum environment; all three exhibited repeatable morphing behavior, and it is shown through validated computational analysis that the morphing radiator concept can achieve a turndown ratio of 27:1 with a number of simple configuration changes.

Development and Testing of a Shape Memory Alloy-Driven Composite Morphing Radiator

Science.gov (United States)

Walgren, P.; Bertagne, C.; Wescott, M.; Benafan, O.; Erickson, L.; Whitcomb, J.; Hartl, D.

2018-03-01

Future crewed deep space missions will require thermal control systems that can accommodate larger fluctuations in temperature and heat rejection loads than current designs. To maintain the crew cabin at habitable temperatures throughout the entire mission profile, radiators will be required to exhibit turndown ratios (defined as the ratio between the maximum and minimum heat rejection rates) as high as 12:1. Potential solutions to increase radiator turndown ratios include designs that vary the heat rejection rate by changing shape, hence changing the rate of radiation to space. Shape memory alloys exhibit thermally driven phase transformations and thus can be used for both the control and actuation of such a morphing radiator with a single active structural component that transduces thermal energy into motion. This work focuses on designing a high-performance composite radiator panel and investigating the behavior of various SMA actuators in this application. Three designs were fabricated and subsequently tested in a relevant thermal vacuum environment; all three exhibited repeatable morphing behavior, and it is shown through validated computational analysis that the morphing radiator concept can achieve a turndown ratio of 27:1 with a number of simple configuration changes.

Optimal design of damping layers in SMA/GFRP laminated hybrid composites

Science.gov (United States)

Haghdoust, P.; Cinquemani, S.; Lo Conte, A.; Lecis, N.

2017-10-01

This work describes the optimization of the shape profiles for shape memory alloys (SMA) sheets in hybrid layered composite structures, i.e. slender beams or thinner plates, designed for the passive attenuation of flexural vibrations. The paper starts with the description of the material and architecture of the investigated hybrid layered composite. An analytical method, for evaluating the energy dissipation inside a vibrating cantilever beam is developed. The analytical solution is then followed by a shape profile optimization of the inserts, using a genetic algorithm to minimize the SMA material layer usage, while maintaining target level of structural damping. Delamination problem at SMA/glass fiber reinforced polymer interface is discussed. At the end, the proposed methodology has been applied to study the hybridization of a wind turbine layered structure blade with SMA material, in order to increase its passive damping.

Role of alloying additions on the properties of Cu–Al–Mn shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Dasgupta, Rupa, E-mail: rupadasgupta@ampri.res.in; Jain, Ashish Kumar; Kumar, Pravir; Hussain, Shahadat; Pandey, Abhishek

2015-01-25

Highlights: • Cu based SMAs with high transition temperature could be made using LM route. • The properties depend on alloying composition. • Property characterisation establishes feasibility of making SMAs. - Abstract: The effect of alloying seven different elements [Zn, Si, Fe, Ni, Mg, Cr and Ti] on the microstructure, hardness, phase precipitation and transformation temperature in a Cu–12.5Al–5Mn alloy with a view to possible improvements as a result of these additions is the focus of the reported study. The base alloy has been chosen keeping in mind its ability to exhibit shape memory properties and improved ductility over other Cu-based SMAs. The objective was to ascertain changes or improvements attained due to the individual tertiary additions. The samples were prepared through liquid metallurgy route using pure copper, aluminum, manganese and the respective quaternary alloying elements in right quantities to weigh 1000 g of the alloy in total and were melted together. Samples from the cast alloys were subject to homogenisation treatment at 200 °C for 2 h in a muffle furnace and furnace cooled. Samples from the homogenised alloys were heated and held for 2 h at 920 °C followed by ice quenching to obtain the desired martensitic structure for shape memory behaviour. The alloys in the cast, homogenised and quenched conditions were metallographically polished to observe the martensitic phase formation mainly in quenched samples which is a pre requisite for exhibiting shape memory properties in these alloys. X-ray Diffraction studies were carried out on the cast and quenched samples using Cu Kα target; and the phases identified indicate martensitic phase precipitation; however in some cases the precipitation is incomplete. Differential Scanning Calorimetric [DSC] studies were carried out on quenched samples from room temperature to 600 °C maintaining a constant rate of 10 °C/min. Results indicate clear transformation peaks in all the samples which

Role of alloying additions on the properties of Cu–Al–Mn shape memory alloys

International Nuclear Information System (INIS)

Dasgupta, Rupa; Jain, Ashish Kumar; Kumar, Pravir; Hussain, Shahadat; Pandey, Abhishek

2015-01-01

Highlights: • Cu based SMAs with high transition temperature could be made using LM route. • The properties depend on alloying composition. • Property characterisation establishes feasibility of making SMAs. - Abstract: The effect of alloying seven different elements [Zn, Si, Fe, Ni, Mg, Cr and Ti] on the microstructure, hardness, phase precipitation and transformation temperature in a Cu–12.5Al–5Mn alloy with a view to possible improvements as a result of these additions is the focus of the reported study. The base alloy has been chosen keeping in mind its ability to exhibit shape memory properties and improved ductility over other Cu-based SMAs. The objective was to ascertain changes or improvements attained due to the individual tertiary additions. The samples were prepared through liquid metallurgy route using pure copper, aluminum, manganese and the respective quaternary alloying elements in right quantities to weigh 1000 g of the alloy in total and were melted together. Samples from the cast alloys were subject to homogenisation treatment at 200 °C for 2 h in a muffle furnace and furnace cooled. Samples from the homogenised alloys were heated and held for 2 h at 920 °C followed by ice quenching to obtain the desired martensitic structure for shape memory behaviour. The alloys in the cast, homogenised and quenched conditions were metallographically polished to observe the martensitic phase formation mainly in quenched samples which is a pre requisite for exhibiting shape memory properties in these alloys. X-ray Diffraction studies were carried out on the cast and quenched samples using Cu Kα target; and the phases identified indicate martensitic phase precipitation; however in some cases the precipitation is incomplete. Differential Scanning Calorimetric [DSC] studies were carried out on quenched samples from room temperature to 600 °C maintaining a constant rate of 10 °C/min. Results indicate clear transformation peaks in all the samples which

Numerical tool for SMA material simulation: application to composite structure design

International Nuclear Information System (INIS)

Chemisky, Yves; Tahiri, Vanessa; Duval, Arnaud; Piotrowski, Boris; Ben Zineb, Tarak; Patoor, Etienne

2009-01-01

Composite materials based on shape memory alloys (SMA) have received growing attention over these last few years. In this paper, two particular morphologies of composites are studied. The first one is an SMA/elastomer composite in which a snake-like wire NiTi SMA is embedded into an elastomer ribbon. The second one is a commercial Ni 47 Ti 44 Nb 9 which presents elastic–plastic inclusions in an NiTi SMA matrix. In both cases, the design of such composites required the development of an SMA design tool, based on a macroscopic 3D constitutive law for NiTi alloys. Two different strategies are then applied to compute these composite behaviors. For the SMA/elastomer composite, the macroscopic behavior law is implemented in commercial FEM software, and for the Ni 47 Ti 44 Nb 9 a scale transition approach based on the Mori–Tanaka scheme is developed. In both cases, simulations are compared to experimental data

Quasistatic isothermal evolution of shape memory alloys

Czech Academy of Sciences Publication Activity Database

Frigeri, S.; Krejčí, Pavel; Stefanelli, U.

2011-01-01

Roč. 21, č. 12 (2011), s. 2409-2432 ISSN 0218-2025 R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : shape memory alloys * quasistatic evolution Subject RIV: BA - General Mathematics Impact factor: 1.635, year: 2011 http://www.worldscinet.com/m3as/21/2112/S0218202511005787.html

A one-stage, high-load capacity separation actuator using anti-friction rollers and redundant shape memory alloy wires.

Science.gov (United States)

Xiaojun, Yan; Dawei, Huang; Xiaoyong, Zhang; Ying, Liu; Qiaolong, Yang

2015-12-01

This paper proposes a SMA (shape memory alloy) wire-based separation actuator with high-load capacity and simple structure. The novel actuator is based on a one-stage locking mechanism, which means that the separation is directly driven by the SMA wire. To release a large preload, a group of anti-friction rollers are adopted to reduce the force for triggering. In addition, two SMA wires are used redundantly to ensure a high reliability. After separation, the actuator can be reset automatically without any auxiliary tool or manual operation. Three prototypes of the separation actuator are fabricated and tested. According to the performance test results, the actuator can release a maximum preload of 40 kN. The separation time tends to decrease as the operation current increases and it can be as short as 0.5 s under a 7.5 A (the voltage is 5.8 V) current. Lifetime test indicates that the actuator has a lifetime of more than 50 cycles. The environmental tests demonstrate that the actuator can endure the typical thermal and vibration environment tests without unexpected separation or structure damage, and separate normally after these environment tests.

Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

Science.gov (United States)

La Roca, P.; Baruj, A.; Sade, M.

2017-03-01

Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.