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.

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.

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)

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.

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

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.

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.

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.

Ti-Ni-based shape memory alloys as smart materials

International Nuclear Information System (INIS)

Otsuka, K.; Xu, Y.; Ren, X.

2003-01-01

Smart materials consist of three principal materials, ferroelectrics, shape memory alloys (SMA) and electro-active polymers (EAP). Among these SMAs, especially Ti-Ni-based alloys are important, since only they can provide large recoverable strains and high recovery stress. In the present paper the unique characteristics of Ti-Ni-based shape memory alloys are reviewed on an up-to-date basis with the aim of their applications to smart materials and structures. (orig.)

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

A slant type shape memory alloy

International Nuclear Information System (INIS)

Kanada, T.; Enokizono, M.

2000-01-01

A heat-treated Fe-based shape memory alloy (SMA) has compatible properties, magnetization and shape memory effect (SME). Since SME depends on the heat treatment conditions (temperature and time), we produced a slant-type SMA that has a gradient SME value in the longitudinal direction of the specimen. It is obvious that sheet specimen is superior to wire because the value of SME as a slant SME shows greater efficiency than that of wire

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).

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 alloy actuator

Science.gov (United States)

Varma, Venugopal K.

2001-01-01

An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

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...

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.)

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

Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

Science.gov (United States)

Padula, Santo A., II (Inventor)

2016-01-01

Methods and apparatuses for stabilizing the strain-temperature response for a shape memory alloy are provided. To perform stabilization of a second sample of the shape memory alloy, a first sample of the shape memory alloy is selected for isobaric treatment and the second sample is selected for isothermal treatment. When applying the isobaric treatment to the first sample, a constant stress is applied to the first sample. Temperature is also cycled from a minimum temperature to a maximum temperature until a strain on the first sample stabilizes. Once the strain on the first sample stabilizes, the isothermal treatment is performed on the second sample. During isothermal treatment, different levels of stress on the second sample are applied until a strain on the second sample matches the stabilized strain on the first sample.

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.)

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

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

Nonlinear Model of Pseudoelastic Shape Memory Alloy Damper Considering Residual Martensite Strain Effect

Directory of Open Access Journals (Sweden)

Y. M. Parulekar

2012-01-01

Full Text Available Recently, there has been increasing interest in using superelastic shape memory alloys for applications in seismic resistant-design. Shape memory alloys (SMAs have a unique property by which they can recover their original shape after experiencing large strains up to 8% either by heating (shape memory effect or removing stress (pseudoelastic effect. Many simplified shape memory alloy models are suggested in the past literature for capturing the pseudoelastic response of SMAs in passive vibration control of structures. Most of these models do not consider the cyclic effects of SMA's and resulting residual martensite deformation. Therefore, a suitable constitutive model of shape memory alloy damper which represents the nonlinear hysterical dynamic system appropriately is essential. In this paper a multilinear hysteretic model incorporating residual martensite strain effect of pseudoelastic shape memory alloy damper is developed and experimentally validated using SMA wire, based damper device. A sensitivity analysis is done using the proposed model along with three other simplified SMA models. The models are implemented on a steel frame representing an SDOF system and the comparison of seismic response of structure with all the models is made in the numerical study.

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 Alloy Adaptive Structures, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This SBIR Phase I effort will demonstrate and scale up an innovative manufacturing process that yields aerospace grade shape memory alloy (SMA) solids and periodic...

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%.

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

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...

Nonlinear dynamics of a nonsmooth shape memory alloy oscillator

International Nuclear Information System (INIS)

Cardozo dos Santos, Bruno; Amorim Savi, Marcelo

2009-01-01

In the last years, there is an increasing interest in nonsmooth system dynamics motivated by different applications including rotor dynamics, oil drilling and machining. Besides, shape memory alloys (SMAs) have been used in various applications exploring their high dissipation capacity related to their hysteretic behavior. This contribution investigates the nonlinear dynamics of shape memory alloy nonsmooth systems considering a linear oscillator with a discontinuous support built with an SMA element. A constitutive model developed by Paiva et al. [Paiva A, Savi MA, Braga AMB, Pacheco PMCL. A constitutive model for shape memory alloys considering tensile-compressive asymmetry and plasticity. Int J Solids Struct 2005;42(11-12):3439-57] is employed to describe the thermomechanical behavior of the SMA element. Numerical investigations show results where the SMA discontinuous support can dramatically change the system dynamics when compared to those associated with a linear elastic support system. A parametric study is of concern showing the system behavior for different system characteristics, forcing excitation and also gaps. These results show that smart materials can be employed in different kinds of mechanical systems exploring some of the remarkable properties of these alloys.

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)

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

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

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...

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

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.)

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.)

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

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

Near Net Shape Fabrication Technology for Shape Memory Alloy Components, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This STTR Phase I effort proposes to develop an innovative, affordable processing route for larger-sized shape memory alloy (SMA) components. Despite significant...

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....

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.)

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.

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

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.

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.)

Shape Memory Alloy-Based Periodic Cellular Structures, Phase I

Data.gov (United States)

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...

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.

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.

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.

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...

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.

Constitutive Models for Shape Memory Alloy Polycrystals

Science.gov (United States)

Comstock, R. J., Jr.; Somerday, M.; Wert, J. A.

1996-01-01

Shape memory alloys (SMA) exhibiting the superelastic or one-way effects can produce large recoverable strains upon application of a stress. In single crystals this stress and resulting strain are very orientation dependent. We show experimental stress/strain curves for a Ni-Al single crystal for various loading orientations. Also shown are model predictions; the open and closed circles indicate recoverable strains obtained at various stages in the transformation process. Because of the strong orientation dependence of shape memory properties, crystallographic texture can be expected to play an important role in the mechanical behavior of polycrystalline SMA. It is desirable to formulate a constitutive model to better understand and exploit the unique properties of SMA.

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

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

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.

Stress Relaxation Of Superelastic Shape Memory Alloy Under Bending And Torsional Load

Directory of Open Access Journals (Sweden)

Sakib Tanvir

2017-04-01

Full Text Available Stress Relaxation of Superelastic Shape memory NiTi Alloy under bending and torsion is uncommon in literature. Therefore experimental set up has been devised and test results are obtained for superelastic SMA.Unlike the other common engineering materials superelastic SMA it gives dramatic reduction in stress. In this paper therefore results of stress relaxation of superelastic shape memory alloy under bending and torsion are presented graphically and interpreted in terms of stress induced martensitic transformation.

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.

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.

Titanium-nickel shape memory alloys development in Taiwan

International Nuclear Information System (INIS)

Wu, S. K.; Lin, H. C.

1997-01-01

In Taiwan, many groups engage in the development of TiNi SMAs. The two-stage martensitic transformations of B2 R-phase B19' and B2 B19 B19' have been clarified for both TiNi binary and ternary alloys. The deformation behaviours have been investigated by cold-rolling, hot-rolling and wire drawing. Both shape memory effect and pseudoelasticity can be improved by some thermo-mechanical treatments. The damping characteristics of TiNi and TiNiX SMAs have also been systematically studied. Both B19'/B19 martensite (M) and R-phase (R) have high damping capacities due to stress induced movement of twin boundaries. Meanwhile, the addition of third elements, Fe and Cu, can largely increase the damping capacity. Recently, some high temperature shape memory alloys of TiNiPd and TiNiAu SMAs and thin films of TiNi and TiNiX alloys have also been intensively studied in Taiwan. All these potential investigations on the TiNi SMAs in Taiwan have attracted much attention and their important characteristics will be applied widely in the near future. (author)

A review on shape memory alloys with applications to morphing aircraft

International Nuclear Information System (INIS)

Barbarino, S; Saavedra Flores, E I; Ajaj, R M; Dayyani, I; Friswell, M I

2014-01-01

Shape memory alloys (SMAs) are a unique class of metallic materials with the ability to recover their original shape at certain characteristic temperatures (shape memory effect), even under high applied loads and large inelastic deformations, or to undergo large strains without plastic deformation or failure (super-elasticity). In this review, we describe the main features of SMAs, their constitutive models and their properties. We also review the fatigue behavior of SMAs and some methods adopted to remove or reduce its undesirable effects. SMAs have been used in a wide variety of applications in different fields. In this review, we focus on the use of shape memory alloys in the context of morphing aircraft, with particular emphasis on variable twist and camber, and also on actuation bandwidth and reduction of power consumption. These applications prove particularly challenging because novel configurations are adopted to maximize integration and effectiveness of SMAs, which play the role of an actuator (using the shape memory effect), often combined with structural, load-carrying capabilities. Iterative and multi-disciplinary modeling is therefore necessary due to the fluid–structure interaction combined with the nonlinear behavior of SMAs. (topical review)

A preliminary investigation of shape memory alloys in the surgical correction of scoliosis.

Science.gov (United States)

Sanders, J O; Sanders, A E; More, R; Ashman, R B

1993-09-15

Nitinol, a shape memory alloy, is flexible at low temperatures but retains its original shape when heated. This offers interesting possibilities for scoliosis correction. Of the shape memory alloys, nitinol is the most promising medically because of biocompatibility and the ability to control transition temperature. In vivo: Six goats with experimental scoliosis were instrumented with 6-mm nitinol rods. The rods were transformed, and the scoliosis corrected, in the awakened goats by 450-kHz radio frequency induction heating. The curves averaged 41 degrees before instrumentation, 33 degrees after instrumentation, and 11 degrees after rod transformation. The animals tolerated the heating without discomfort, neurologic injury, or evidence of thermal injury to the tissues or the spinal cord. In vitro: Nitinol rods were tested under both constant deflection and constant loading conditions and plotted temperature versus either force or displacement. The 6-mm rod generated forces of 200 N. The 9-mm rod generated up to 500 N. We safely coupled shape memory alloy transformation to the spine and corrected an experimental spinal deformity in awake animals. The forces generated can be estimated by the rod's curvature and temperature. The use of shape memory alloys allows continuous neurologic monitoring during awake correction, true rotational correction by rod torsion, and the potential option of periodic correction to take advantage of spinal viscoelasticity and the potential of true rotational correction by rod torsion.

Using Shape Memory Alloys: A Dynamic Data Driven Approach

KAUST Repository

Douglas, Craig C.; Calo, Victor M.; Cerwinsky, Derrick; Deng, Li; Efendiev, Yalchin R.

2013-01-01

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

Effect of surface oxidation on thermomechanical behavior of NiTi shape memory alloy wire

Science.gov (United States)

Ng, Ching Wei; Mahmud, Abdus Samad

2017-12-01

Nickel titanium (NiTi) alloy is a unique alloy that exhibits special behavior that recovers fully its shape after being deformed to beyond elastic region. However, this alloy is sensitive to any changes of its composition and introduction of inclusion in its matrix. Heat treatment of NiTi shape memory alloy to above 600 °C leads to the formation of the titanium oxide (TiO2) layer. Titanium oxide is a ceramic material that does not exhibit shape memory behaviors and possess different mechanical properties than that of NiTi alloy, thus disturbs the shape memory behavior of the alloy. In this work, the effect of formation of TiO2 surface oxide layer towards the thermal phase transformation and stress-induced deformation behaviors of the NiTi alloy were studied. The NiTi wire with composition of Ti-50.6 at% Ni was subjected to thermal oxidation at 600 °C to 900 °C for 30 and 60 minutes. The formation of the surface oxide layers was characterized by using the Scanning Electron Microscope (SEM). The effect of surface oxide layers with different thickness towards the thermal phase transformation behavior was studied by using the Differential Scanning Calorimeter (DSC). The effect of surface oxidation towards the stress-induced deformation behavior was studied through the tensile deformation test. The stress-induced deformation behavior and the shape memory recovery of the NiTi wire under tensile deformation were found to be affected marginally by the formation of thick TiO2 layer.

Study of Cu-Al-Ni-Ga as high-temperature shape memory alloys

Science.gov (United States)

Zhang, Xin; Wang, Qian; Zhao, Xu; Wang, Fang; Liu, Qingsuo

2018-03-01

The effect of Ga element on the microstructure, mechanical properties and shape memory effect of Cu-13.0Al-4.0Ni- xGa (wt%) high-temperature shape memory alloy was investigated by optical microscopy, SEM, XRD and compression test. The microstructure observation results showed that the Cu-13.0Al-4.0Ni- xGa ( x = 0.5 and 1.0) alloys displayed dual-phase morphology which consisted of 18R martensite and (Al, Ga)Cu phase, and their grain size was about several hundred microns, smaller than that of Cu-13.0Al-4.0Ni alloy. The compression test results proved that the mechanical properties of Cu-13.0Al-4.0Ni- xGa alloys were improved by addition of Ga element owing to the grain refinement and solid solution strengthening, and the compressive fracture strains were 11.5% for x = 0.5 and 14.9% for x = 1.0, respectively. When the pre-strain was 8%, the shape memory effect of 4.2 and 4.6% were obtained for Cu-13.0Al-4.0Ni-0.5 Ga and Cu-13.0Al-4.0Ni-1.0 Ga alloys after being heated to 400 °C for 1 min.

Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys

Science.gov (United States)

Yamabe-Mitarai, Yoko; Takebe, Wataru; Shimojo, Masayuki

2017-12-01

To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti-(50 - x)Pt- xPd-5Zr alloys ( x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti-50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was training effect was also investigated.

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

Directory of Open Access Journals (Sweden)

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.

Shape memory materials

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

Compared with piezoelectric ceramics and magnetostrictive materials, the shape memory materials possess larger recoverable strain and recovery stress but slower response to external field. It is expected that the magneto-shape memory materials may develop considerable strain as well as rapid and precise shape control. Pseudoelasticity and shape memory effect (SME) resulted from martensitic transformation and its reverse transformation in shape memory materials were generally described. The requirements of appearing the shape memory effect in materials and the criteria for thermoelastic martensitic transformation were given. Some aspects concerning characteristics of martensitic transformation, and factors affecting SME in Ni-Ti, Cu-Zn-Al and Fe-Mn-Si based alloys as well as ZrO2 containing ceramics were briefly reviewed. Thermodynamic calculation of Ms temperature as function of grain size and parent ordering in Cu-Zn-Al was presented. The works on prediction of Ms in Fe-Mn-Si based alloys and in ZrO2-CeO2 were mentioned. Magnetic shape memory materials were briefly introduced.

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

Shape memory characteristics of Ti-22Nb-(2-8)Zr(at.%) biomedical alloys

International Nuclear Information System (INIS)

Kim, J.I.; Kim, H.Y.; Inamura, T.; Hosoda, H.; Miyazaki, S.

2005-01-01

Shape memory characteristics of Ti-22Nb-(2-8)Zr(at.%) biomedical alloys were investigated by using tensile tests and X-ray diffraction (XRD) measurement. The alloy ingots were fabricated by an arc melting method. The ingots were cold-rolled by a reduction up to 95% in thickness at room temperature. All the alloys were solution-treated at 1173 K for 1.8 ks. The alloys subjected to the solution treatment exhibited large elongations ranging between 28 and 40%. The martensitic transformation temperature decreased by 38 K with 1 at.% increase of Zr content. The maximum recovered strain of 4.3% was obtained in the Ti-22Nb-4Zr(at.%) alloy. Ti-22Nb-(2-4)Zr(at.%) and Ti-22Nb-6Zr(at.%) alloys exhibited stable shape memory effect and superelastic behavior at room temperature, respectively

Cellular Shape Memory Alloy Structures: Experiments & Modeling (Part 1)

Science.gov (United States)

2012-08-01

High -­‐ temperature  SMAs 24 Braze  Joint  between  two  wrought  pieces  of  a  Ni24.5Pd25Ti50.5  HTSMA   (HTSMA  from...process  can  be  used   to  join  other  metal  alloys  and   high -­‐ temperature   SMAs 25 Cellular  Shape  Memory...20 30 40 50 60 910 3 4 8 5 2 T (°C) Shape memory & superelasticity 1 0 e (%) (GPa) 6 7 A NiTi wire

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)

Simulation of Dislocation and Transformation Plasticity in Shape Memory Alloys

National Research Council Canada - National Science Library

Volkov, Alexander

1999-01-01

A model of deformation of shape memory alloys has been developed. It takes into account deformation due to the phase transformation and plastic deformation, produced by an external stress or by inter-phase stresses...

Design of shape memory alloy (SMA) actuators

CERN Document Server

Rao, Ashwin; Reddy, J N

2015-01-01

This short monograph presents an analysis and design methodology for shape memory alloy (SMA) components such as wires, beams, and springs for different applications. The solid-solid, diffusionless phase transformations in thermally responsive SMA allows them to demonstrate unique characteristics like superelasticity and shape memory effects. The combined sensing and actuating capabilities of such materials allows them to provide a system level response by combining multiple functions in a single material system. In SMA, the combined mechanical and thermal loading effects influence the functionality of such materials. The aim of this book is to make the analysis of these materials accessible to designers by developing a "strength of materials" approach to the analysis and design of such SMA components inspired from their various applications with a review of various factors influencing the design process for such materials.

Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

Directory of Open Access Journals (Sweden)

Miaolei Zhou

Full Text Available As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

Science.gov (United States)

Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

2014-01-01

As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

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.

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 ...

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.

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.

Phase stability of CuAlMn shape memory alloys

Czech Academy of Sciences Publication Activity Database

Zárubová, Niva; Novák, Václav

2004-01-01

Roč. 378, - (2004), s. 216-221 ISSN 0921-5093 Institutional research plan: CEZ:AV0Z1010914 Keywords : CuAlMn * shape memory alloys * martensitic transformation * - stress -strain tests * tension-compression cycling * history dependent phenomena Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.445, year: 2004

Magnetic shape-memory alloys: thermomechanical modelling and analysis

Czech Academy of Sciences Publication Activity Database

Roubíček, Tomáš; Stefanelli, U.

2014-01-01

Roč. 26, č. 6 (2014), s. 783-810 ISSN 0935-1175 R&D Projects: GA ČR GAP201/10/0357 Institutional support: RVO:61388998 Keywords : magnetic shape- memory alloys * martensitic phase transformation * ferro/paramagnetic phase transformation Subject RIV: BA - General Mathematics Impact factor: 1.779, year: 2014 http://link.springer.com/article/10.1007/s00161-014-0339-8#

Enhanced photomechanical response of a Ni-Ti shape memory alloy coated with polymer-based photothermal composites

Science.gov (United States)

Perez-Zúñiga, M. G.; Sánchez-Arévalo, F. M.; Hernández-Cordero, J.

2017-10-01

A simple way to enhance the activation of shape memory effects with light in a Ni-Ti alloy is demonstrated. Using polydimethylsiloxane-carbon nanopowder (PDMS+CNP) composites as coatings, the one-way shape memory effect (OWSME) of the alloy can be triggered using low power IR light from a laser diode. The PDMS+CNP coatings serve as photothermal materials capable to absorb light, and subsequently generate and dissipate heat in a highly efficient manner, thereby reducing the optical powers required for triggering the OWSME in the Ni-Ti alloy. Experimental results with a cantilever flexural test using both, bare Ni-Ti and coated samples, show that the PDMS+CNP coatings perform as thermal boosters, and therefore the temperatures required for phase transformation in the alloy can be readily obtained with low laser powers. It is also shown that the two-way shape memory effect (TWSME) can be set in the Ni-Ti alloy through cycling the TWSME by simply modulating the laser diode signal. This provides a simple means for training the material, yielding a light driven actuator capable to provide forces in the mN range. Hence, the use of photothermal coatings on Ni-Ti shape memory alloys may offer new possibilities for developing light-controlled smart actuators.

Fracture behaviour of Cu-Al-Ni shape memory alloys obtained by powder metallurgy

International Nuclear Information System (INIS)

Rodriguez, P. P.; Perez-Saez, R. B.; Recarte, V.; San Juan, J.M.; Ruano, O. A.; No, M. L.

2001-01-01

Polycrystalline Cu-Al-Ni shape memory alloys have been scarcely employed for technological applications due to their high brittleness. The development of a new elaboration technique based on powder metallurgy has recently overcome this problem, through the improvement of the ductility of the produced alloys without affecting its shape memory properties. The fracture behaviour of an alloy obtained using the elaboration technique has been studied by means of Scanning Electron Microscopy and mechanical testing. The results show a ductile fracture with a maximum strain close to 13%, which is the best fracture behaviour obtained for Cu-Al-Ni polycrystals. The microstructure of such alloys ha been studied by means of Transmission Electron Microscopy, showing a poligonyzed structure in which martensite plated passing through the subboundaries easily. (Author) 19 refs

A review on the martensitic transformation and shape memory effect in Fe-Mn-Si alloys

International Nuclear Information System (INIS)

Gu, Q.; Humbeeck, J. van; Delaey, L.

1994-01-01

The martensitic transformation and the shape memory effect in Fe-Mn-Si alloys received great attention recently due to its potential commercial value. In this paper, the mechanisms for the martensitic transformation and various parameters influencing the shape memory effect like alloy composition, applied stress, prestrain, crystal orientation, temperature, grain size, pre-existing martensite, thermal cycling and training etc. are reviewed and discussed. (orig.)

Martensitic transformation in Co-based ferromagnetic shape memory alloy

Czech Academy of Sciences Publication Activity Database

Kopeček, Jaromír; Yokaichiya, F.; Laufek, F.; Jarošová, Markéta; Jurek, Karel; Drahokoupil, Jan; Sedláková-Ignácová, Silvia; Molnár, Peter; Heczko, Oleg

2012-01-01

Roč. 122, č. 3 (2012), s. 475-477 ISSN 0587-4246. [International Symposium on Physics of Materials, ISPMA /12./. Praha, 04.09.2011-08.09.2011] R&D Projects: GA ČR(CZ) GA101/09/0702; GA ČR GAP107/10/0824; GA AV ČR IAA100100920 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : microstructure * shape memory alloys * neutron diffraction * cobalt alloys Subject RIV: JG - Metallurgy Impact factor: 0.531, year: 2012

A model considering mechanical anisotropy of magnetic-field-induced superelastic strain in magnetic shape memory alloys

International Nuclear Information System (INIS)

Zhu, Yuping; Yu, Kai

2013-01-01

Highlights: ► The model analyzes mechanical anisotropy of magnetic shape memory alloy. ► The numerical evaluation of Eshelby tensor of shape memory alloy is obtained. ► Interaction energy of magnetic shape memory alloy is analyzed. - Abstract: Under applied mechanical load and magnetic field, a micromechanics-based thermodynamic model taking account of mechanical anisotropy of magnetic shape memory alloys (MSMAs) is developed in this work. Considering the crystallographic and magnetic microstructure, the internal state variables are chosen and the model can capture the magnetic shape memory effect caused by the martensitic variant reorientation process. It is assumed that the Gibbs free energy is consisted of the mechanical potential energy of anisotropic matrix, the Zeeman energy and the magnetocrystalline anisotropy energy in the model. In terms of the balance between the thermodynamic driving force derived from the reduction of Gibbs free energy and the resistive force for the variant reorientation, the kinetic equation is established and the Eshelby tensor of anisotropic MSMAs is then obtained by using numerical evaluation. At last, the effects of the anisotropy on interaction energy and macroscopic strain are discussed. The assumption of isotropy tends to underestimate interaction energy and macroscopic strain. The results considering mechanical anisotropy are in good agreement with the experimental data.

Review on structural fatigue of NiTi shape memory alloys: Pure mechanical and thermo-mechanical ones

Directory of Open Access Journals (Sweden)

Guozheng Kang

2015-11-01

Full Text Available Structural fatigue of NiTi shape memory alloys is a key issue that should be solved in order to promote their engineering applications and utilize their unique shape memory effect and super-elasticity more sufficiently. In this paper, the latest progresses made in experimental and theoretical analyses for the structural fatigue features of NiTi shape memory alloys are reviewed. First, macroscopic experimental observations to the pure mechanical and thermo-mechanical fatigue features of the alloys are summarized; then the state-of-arts in the mechanism analysis of fatigue rupture are addressed; further, advances in the construction of fatigue failure models are provided; finally, summary and future topics are outlined.

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...

Cu-based shape memory alloys with enhanced thermal stability and mechanical properties

International Nuclear Information System (INIS)

Chung, C.Y.; Lam, C.W.H.

1999-01-01

Cu-based shape memory alloys were developed in the 1960s. They show excellent thermoelastic martensitic transformation. However the problems in mechanical properties and thermal instability have inhibited them from becoming promising engineering alloys. A new Cu-Zn-Al-Mn-Zr Cu-based shape memory alloy has been developed. With the addition of Mn and Zr, the martensitic transformation behaviour and the grain size ca be better controlled. The new alloys demonstrates good mechanical properties with ultimate tensile strenght and ductility, being 460 MPa and 9%, respectively. Experimental results revealed that the alloy has better thermal stability, i.e. martensite stabilisation is less serious. In ordinary Cu-Zn-Al alloys, martensite stabilisation usually occurs at room temperature. The new alloy shows better thermal stability even at elevated temperature (∝150 C, >A f =80 C). A limited small amount of martensite stabilisation was observed upon ageing of the direct quenched samples as well as the step quenched samples. This implies that the thermal stability of the new alloy is less dependent on the quenching procedure. Furthermore, such minor martensite stabilisation can be removed by subsequent suitable parent phase ageing. The new alloy is ideal for engineering applications because of its better thermal stability and better mechanical properties. (orig.)

Phase transformation and precipitation in aged Ti-Ni-Hf high-temperature shape memory alloys

International Nuclear Information System (INIS)

Meng, X.L.; Cai, W.; Zheng, Y.F.; Zhao, L.C.

2006-01-01

More attention has been paid to ternary Ti-Ni-Hf high-temperature shape memory alloys (SMAs) due to their high phase transformation temperatures, good thermal stability and low cost. However, the Ti-Ni-Hf alloys have been found to have low ductility and only about 3% shape memory effect and these have hampered their applications. It is well known that there are three methods to improve the shape memory properties of high-temperature SMAs: (a) cold rolling + annealing; (b) adding another element to the alloy; (c) aging. These methods are not suitable to improve the properties of Ti-Ni-Hf alloys. In this paper, a method of conditioning Ni-rich Ti-Ni-Hf alloys as high-temperature SMAs by aging is presented. For Ni-rich Ti 80-x Ni x Hf 20 alloys (numbers indicate at.%) the phase transformation temperatures are on average increased by more than 100 K by aging at 823 K for 2 h. Especially for those alloys with Ni contents less than 50.6 at.%, the martensitic transformation start temperatures (M s ) are higher than 473 K after aging. Transmission electron microscopy shows the presence of (Ti + Hf) 3 Ni 4 precipitates after aging. Compared with the precipitation of Ti 3 Ni 4 particles in Ni-rich Ti-Ni alloys, the precipitation of (Ti + Hf) 3 Ni 4 particles in Ni-rich Ti-Ni-Hf alloys needs higher temperatures and longer times

Vacuum Arc Melting Processes for Biomedical Ni-Ti Shape Memory Alloy

OpenAIRE

Tsai De-Chang; Chiang Chen-Hsueh

2015-01-01

This study primarily involved using a vacuum arc remelting (VAR) process to prepare a nitinol shape-memory alloy with distinct ratios of alloy components (nitinol: 54.5 wt% to 57 wt%). An advantage of using the VAR process is the adoption of a water-cooled copper crucible, which effectively prevents crucible pollution and impurity infiltration. Optimising the melting production process enables control of the alloy component and facilitates a uniformly mixed compound during subsequent processi...

Precipitation-induced of partial annealing of Ni-rich NiTi shape memory alloy

Science.gov (United States)

Nashrudin, Muhammad Naqib; Mahmud, Abdus Samad; Mohamad, Hishamiakim

2018-05-01

NiTi shape memory alloy behavior is very sensitive to alloy composition and heat treatment processes. Thermomechanical behavior of near-equiatomic alloy is normally enhanced by partial anneal of a cold-worked specimen. The shape memory behavior of Ni-rich alloy can be enhanced by ageing precipitation. This work studied the effect of simultaneous partial annealing and ageing precipitation of a Ni-rich cold drawn Ti-50.9at%Ni wire towards martensite phase transformation behavior. Ageing treatment of a non-cold worked specimen was also done for comparison. It was found that the increase of heat treatment temperature caused the forward transformation stress to decrease for the cold worked and non-cold worked specimens. Strain recovery on the reverse transformation of the cold worked wire improved compared to the non-cold worked wire as the temperature increased.

Void formation in NiTi shape memory alloys by medium-voltage electron irradiation

International Nuclear Information System (INIS)

Schlossmacher, P.; Stober, T.

1995-01-01

In-situ electron irradiation experiments of NiTi shape memory alloys, using high-voltage transmission electron microscopes, result in amorphization of the intermetallic compound. In all of these experiments high-voltages more than 1.0 MeV had to be applied in order to induce the crystalline-to-amorphous transformation. To their knowledge no irradiation effects of medium-voltage electrons of e.g. 0.5 MeV have been reported in the literature. In this contribution, the authors describe void formation in two different NiTi shape memory alloys, resulting from in-situ electron irradiation, using a 300 kV electron beam in a transmission electron microscope. First evidence is presented that void formation is correlated with the total oxygen content of the alloys

PROPERTY DATABASE FOR THE DEVELOPMENT OF SHAPE MEMORY ALLOY APPLICATIONS

OpenAIRE

Tang , W.; CederstrÖm , J.; SandstrÖm , R.

1991-01-01

Important points involving the selection of shape memory alloy (SMA) application projects are discussed. The development of a property database for SMA is initiated. Both conventional data as well as characteristics which are unique for SMA are stored. As an application example of the database SMA-SELECT, important properties for Ti-Ni alloys near equi-atomic composition, such as temperature window width for superelasticity (SE), stress rate, critical yield stress, and their interaction have ...

B2 intermetallic compounds of Zr. New class of the shape memory alloys

International Nuclear Information System (INIS)

Koval, Yu.N.; Delaey, L.; Jang, W.Y.

1995-01-01

It is known that the B2 equiatomic intermetallic compounds of Zr (ZrCo-based) undergo a martensitic transformation (MT) with wide temperature hysteresis. It was found that the MT is accompanied by the perfect shape memory effect (SME) for ZrCu and ZrRh. In this report we represent the results of structural analysis, electrical resistivity, calorimetric and SME measurements for ZrCu- and ZrCo-based compounds. Interrelation between structural, thermodynamical parameters of MT and SME in this alloys will be described. The shape memory aspects of this potential alloys for the application at high temperatures will be discussed. (orig.)

Impurity levels and fatigue lives of pseudoelastic NiTi shape memory alloys

International Nuclear Information System (INIS)

Rahim, M.; Frenzel, J.; Frotscher, M.; Pfetzing-Micklich, J.; Steegmüller, R.; Wohlschlögel, M.; Mughrabi, H.; Eggeler, G.

2013-01-01

In the present work we show how different oxygen (O) and carbon (C) levels affect fatigue lives of pseudoelastic NiTi shape memory alloys. We compare three alloys, one with an ultrahigh purity and two which contain the maximum accepted levels of C and O. We use bending rotation fatigue (up to cycle numbers >10 8 ) and scanning electron microscopy (for investigating microstructural details of crack initiation and growth) to study fatigue behavior. High cycle fatigue (HCF) life is governed by the number of cycles required for crack initiation. In the low cycle fatigue (LCF) regime, the high-purity alloy outperforms the materials with higher number densities of carbides and oxides. In the HCF regime, on the other hand, the high-purity and C-containing alloys show higher fatigue lives than the alloy with oxide particles. There is high experimental scatter in the HCF regime where fatigue cracks preferentially nucleate at particle/void assemblies (PVAs) which form during processing. Cyclic crack growth follows the Paris law and does not depend on impurity levels. The results presented in the present work contribute to a better understanding of structural fatigue of pseudoelastic NiTi shape memory alloys

Efficiency of Energy Harvesting in Ni-Mn-Ga Shape Memory Alloys

Science.gov (United States)

Lindquist, Paul; Hobza, Tony; Patrick, Charles; Müllner, Peter

2018-03-01

Many researchers have reported on the voltage and power generated while energy harvesting using Ni-Mn-Ga shape memory alloys; few researchers report on the power conversion efficiency of energy harvesting. We measured the magneto-mechanical behavior and energy harvesting of Ni-Mn-Ga shape memory alloys to quantify the efficiency of energy harvesting using the inverse magneto-plastic effect. At low frequencies, less than 150 Hz, the power conversion efficiency is less than 0.1%. Power conversion efficiency increases with (i) increasing actuation frequency, (ii) increasing actuation stroke, and (iii) decreasing twinning stress. Extrapolating the results of low-frequency experiments to the kHz actuation regime yields a power conversion factor of about 20% for 3 kHz actuation frequency, 7% actuation strain, and 0.05 MPa twinning stress.

Uncertainty analysis of a one-dimensional constitutive model for shape memory alloy thermomechanical description

DEFF Research Database (Denmark)

Oliveira, Sergio A.; Savi, Marcelo A.; Santos, Ilmar F.

2014-01-01

The use of shape memory alloys (SMAs) in engineering applications has increased the interest of the accuracy analysis of their thermomechanical description. This work presents an uncertainty analysis related to experimental tensile tests conducted with shape memory alloy wires. Experimental data...... are compared with numerical simulations obtained from a constitutive model with internal constraints employed to describe the thermomechanical behavior of SMAs. The idea is to evaluate if the numerical simulations are within the uncertainty range of the experimental data. Parametric analysis is also developed...

A study on the shape memory characteristics of Ti-Ni50-x-Pdx alloys

International Nuclear Information System (INIS)

Lee, H. W.; Chun, B. S.; Oh, S. J.; Kuk, I.H.

1991-01-01

The shape memory characteristics in TiNi alloys are greatly effected by the alloy composition and heat treatment condition. The present work was aimed to investigate the effect of Pd x (x=5,10,15,20) addition on the shape memory chracteristics of TiNi alloys by means of electrical resistance measurement. X-ray diffraction, differential scanning calorimetry and electron dispersive analysis X-ray measurement. The results obtained from this study are as follows; 1. The martensitic transformation start temperature, Ms of Ti-Ni 50-x -Pd x alloys decreased considerably with the increase of Pd content up to 10at%, whereas increased largely with the increase of Pd content in the alloys with Pd content more than 15at%. 2. The Ms temperature of Ti-Ni 50-x -Pd x alloys with cold working was significantly lower than that of the fully annealed alloys because high density dislocation has been introduced by the cold working which suppressed the martensitic transformation. (Author)

Miniaturized Rotary Actuators Using Shape Memory Alloy for Insect-Type MEMS Microrobot

Directory of Open Access Journals (Sweden)

Ken Saito

2016-03-01

Full Text Available Although several types of locomotive microrobots have been developed, most of them have difficulty locomoting on uneven surfaces. Thus, we have been focused on microrobots that can locomote using step patterns. We are studying insect-type microrobot systems. The locomotion of the microrobot is generated by rotational movements of the shape memory alloy-type rotary actuator. In addition, we have constructed artificial neural networks by using analog integrated circuit (IC technology. The artificial neural networks can output the driving waveform without using software programs. The shape memory alloy-type rotary actuator and the artificial neural networks are constructed with silicon wafers; they can be integrated by using micro-electromechanical system (MEMS technology. As a result, the MEMS microrobot system can locomote using step patterns. The insect-type MEMS microrobot system is 0.079 g in weight and less than 5.0 mm in size, and its locomotion speed is 2 mm/min. The locomotion speed is slow because the heat of the shape memory alloy conducts to the mechanical parts of the MEMS microrobot. In this paper, we discuss a new rotary actuator compared with the previous model and show the continuous rotation of the proposed rotary actuator.

An analytical model for shape memory alloy fiber-reinforced composite thin-walled beam undergoing large deflection

Directory of Open Access Journals (Sweden)

Yongsheng Ren

2015-03-01

Full Text Available The structural model of the thin-walled laminated beams with integral shape memory alloy active fibers and accounting for geometrically nonlinear is presented in this article. The structural modeling is split into two parts: a two-dimensional analysis over the cross section and a geometrically nonlinear analysis of a beam along the beam span. The variational asymptotic method is used to formulate the force–deformation relationship equations taking into account the presence of active shape memory alloy fibers distributed along the cross section of the beam. The geometrically nonlinear governing equations are derived using variational principle and based on the von Kármán-type nonlinear strain–displacement relations. The equations are then solved using Galerkin’s method and an incremental Newton–Raphson method. The validation for the proposed model has been carried out by comparison of the present results with those available in the literature. The results show that significant extension, bending, and twisting coupled nonlinear deflections occur during the phase transformation due to shape memory alloy actuation. The effects of the volume fraction of the shape memory alloy fiber and ply angle are also addressed.

A three-dimensional constitutive model for shape memory alloy

International Nuclear Information System (INIS)

Zhou, Bo; Yoon, Sung-Ho; Leng, Jin-Song

2009-01-01

Shape memory alloy (SMA) has a wide variety of practical applications due to its unique super-elasticity and shape memory effect. It is of practical interest to establish a constitutive model which predicts its phase transformation and mechanical behaviors. In this paper, a new three-dimensional phase transformation equation, which predicts the phase transformation behaviors of SMA, is developed based on the results of a differential scanning calorimetry (DSC) test. It overcomes both limitations: that Zhou's phase transformation equations fail to describe the phase transformation from twinned martensite to detwinned martensite of SMA and Brinson's phase transformation equation fails to express the influences of phase transformation peak temperatures on the phase transformation behaviors of SMA. A new three-dimensional constitutive equation, which predicts the mechanical behaviors associated with the super-elasticity and shape memory effect of SMA, is developed on the basis of thermodynamics and solid mechanics. Results of numerical simulations show that the new constitutive model, which includes the new phase transformation equation and constitutive equation, can predict the phase transformation and mechanical behaviors associated with the super-elasticity and shape memory effect of SMA precisely and comprehensively. It is proved that Brinson's constitutive model of SMA can be considered as one special case of the new constitutive model

Thermomechanical behavior of Ti-rich NiTi shape memory alloys

International Nuclear Information System (INIS)

Paula, A.S.; Mahesh, K.K.; Santos, C.M.L. dos; Braz Fernandes, F.M.; Costa Viana, C.S. da

2008-01-01

Phase transformations associated with shape memory effect in nickel-titanium (NiTi) alloys can be one-stage, B19' (martensite) ↔ B2 (austenite), two-stage including an intermediate R-phase stage, or multiple-stage depending on the thermal and/or mechanical history of the alloy. In the present paper, we highlight the effect of (i) deformation by cold-rolling (from 10% to 40% thickness reduction) and (ii) final annealing on the transformation characteristics of a Ti-rich NiTi shape memory alloy. For this purpose, one set of samples initially heat treated at 773 K followed by cold-rolling (10-40% thickness reduction), has been further heat treated at various temperatures between 673 and 1073 K. Another sample was subjected to heat treatment at 1040 K for 300 s followed by hot rolling (50%) after cooling in air to 773 K and water quenching to room temperature (T room ). Phase transformations were studied using differential scanning calorimetry, electrical resistivity measurements and in situ X-ray diffraction. A specific pattern of transformation sequences is found as a result of combination of the competing effects due to mechanical-working and annealing

Shape memory properties in NiTi alloys

International Nuclear Information System (INIS)

Airoldi, G.; Vicentini, B.; Ranucci, T.; Rivolta, B.

1991-01-01

Mechanical properties of shape memory NiTi alloys are here examined in the frame of literature's results. The operating temperature respect to the intrinsic transformation temperatures explains thoroughly the different stress-strain behaviour, ascribed to different deformation mechanisms acting and to their interplay. Attention is moreover paid to the stress-strain behaviour consequent to a different physical state (martensite phase or parent phase), obtained within the hysteresis cycle, at the same temperature. Evidence of oriented variants, selected by the applied stress, is also given

Additive Manufacturing of Shape Memory Alloys

Science.gov (United States)

Van Humbeeck, Jan

2018-04-01

Selective Laser Melting (SLM) is an additive manufacturing production process, also called 3D printing, in which functional, complex parts are produced by selectively melting patterns in consecutive layers of powder with a laser beam. The pattern the laser beam is following is controlled by software that calculates the pattern by slicing a 3D CAD model of the part to be constructed. Apart from SLM, also other additive manufacturing techniques such as EBM (Electron Beam Melting), FDM (Fused Deposition Modelling), WAAM (Wire Arc Additive Manufacturing), LENS (Laser Engineered Net Shaping such as Laser Cladding) and binder jetting allow to construct complete parts layer upon layer. But since more experience of AM of shape memory alloys is collected by SLM, this paper will overview the potentials, limits and problems of producing NiTi parts by SLM.

Experimental study and theoretical simulation of the cross hardening effect in shape memory alloys

Science.gov (United States)

Movchan, A. A.; Sil'chenko, A. L.; Kazarina, S. A.

2017-10-01

The shapes and the relative position of martensitic inelasticity and forward transformation diagrams are experimentally studied. The strain dependences of the stress in loading under martensitic inelasticity conditions after an experiment on the accumulation of the forward transformation-induced strain at a constant or variable stress are investigated on titanium nickelide samples. It is found that the hardening of the martensite part of the representative volume of a shape memory alloy (titanium nickelide) after forward transformation under a nonmonotonically changing stress can be nonuniform. The cross hardening phenomenon is theoretically described in terms of the model of nonlinear deformation of a shape memory alloy during phase and structural transformations.

Mechanical design of a shape memory alloy actuated prosthetic hand.

Science.gov (United States)

De Laurentis, Kathryn J; Mavroidis, Constantinos

2002-01-01

This paper presents the mechanical design for a new five fingered, twenty degree-of-freedom dexterous hand patterned after human anatomy and actuated by Shape Memory Alloy artificial muscles. Two experimental prototypes of a finger, one fabricated by traditional means and another fabricated by rapid prototyping techniques, are described and used to evaluate the design. An important aspect of the Rapid Prototype technique used here is that this multi-articulated hand will be fabricated in one step, without requiring assembly, while maintaining its desired mobility. The use of Shape Memory Alloy actuators combined with the rapid fabrication of the non-assembly type hand, reduce considerably its weight and fabrication time. Therefore, the focus of this paper is the mechanical design of a dexterous hand that combines Rapid Prototype techniques and smart actuators. The type of robotic hand described in this paper can be utilized for applications requiring low weight, compactness, and dexterity such as prosthetic devices, space and planetary exploration.

Characteristics of Fe-28Mn-6Si-5Cr shape memory alloy produced by centrifugal casting

International Nuclear Information System (INIS)

Otsuka, H.; Maruyama, T.; Kubo, H.

2000-01-01

Recent application of ferrous shape memory alloys, particularly Fe-Mn-Si alloys as pipe joints used for a tunnel driving technique in the field of civil engineering, requires efficient production of alloy pipes. Centrifugal casting is one of the efficient manufacturing techniques which can produce suitable sizes of pipes of approximately 4 to 14 inches in outside diameter. The mechanical properties of the centrifugally cast Fe-Mn-Si shape memory alloy were investigated to have 700 MPa in tensile strength and shape recovery of ∝3% of the initial deformation. The shape recovery achieved by the centrifugally cast materials proved to be comparable to that of the rolled materials. The TEM microstructure of the centrifugally cast materials deformed necessarily in the process of shape recovery reveals random distribution of ε (hcp) bands containing many dislocations inside, whereas the structure of the rolled materials shows ε phases containing fewer dislocations. (orig.)

Microstructural evolution in a Ti-Ta high-temperature shape memory alloy during creep

International Nuclear Information System (INIS)

Rynko, Ramona; Marquardt, Axel; Pauksen, Alexander; Frenzel, Jan; Somsen, Christoph; Eggeler, Gunther

2015-01-01

Alloys based on the titanium-tantalum system are considered for application as high-temperature shape memory alloys due to their martensite start temperatures, which can surpass 200 C. In the present work we study the evolution of microstructure and the influence of creep on the phase transformation behavior of a Ti 70 Ta 30 (at.%) high-temperature shape memory alloy. Creep tests were performed in a temperature range from 470 to 530 C at stresses between 90 and 150 MPa. The activation energy for creep was found to be 307 kJ mol -1 and the stress exponent n was determined as 3.7. Scanning and transmission electron microscopy investigations were carried out to characterize the microstructure before and after creep. It was found that the microstructural evolution during creep suppresses subsequent martensitic phase transformations.

Phase transformation, oxidation and shape memory properties of Ti–50Au–10Zr alloy for high temperature applications

International Nuclear Information System (INIS)

Wadood, A.; Hosoda, H.; Yamabe-Mitarai, Y.

2014-01-01

Highlights: • Ti–50Au–10Zr exhibited better thermo-mechanical and shape memory properties than Ti–50Au. • Improvement was related to solid solution and precipitation strengthening. • No oxidation problem as oxidation was observed at 100 K higher than A f . • TMA was used not only for thermo-mechanical but also for shape memory and oxidation. - Abstract: In this study, we investigated the phase transformation, oxidation and high temperature mechanical and shape memory properties of Ti–50Au–10Zr (all compositions in atomic%) alloy. Thermo-mechanical analyzer (TMA) was used not only for phase transformation but also for the measurement of shape memory effect and oxidation behavior in air environment. Ti–50Au–10Zr exhibited lower martensitic transformation temperature of 758 K than TiAu stoichiometric alloy exhibiting 870 K since Zr addition stabilizes B2 parent phase. Oxidation was initiated at 873 K that was about 100 K higher than the austenite finish temperature, indicating no such oxidation problems for practical use. Shape memory effect was improved by partial substitution of Ti with Zr in Ti–50Au–10Zr alloy. Compression test of Ti–50Au–10Zr revealed high compressive strength of 1239 MPa of martensite at 691 K (=M f − 50 K) and 924 MPa of B2 parent phase at 834 K (=A f + 50 K) in comparison with Ti–50Au. It is concluded that Zr is effective to improve the mechanical and shape memory properties of TiAu alloy, and that Ti–50Au–10Zr shape memory alloy has potential for high temperature (∼650–850 K) practical applications

Review of properties of magnetic shape memory (MSM) alloys and MSM actuator designs

International Nuclear Information System (INIS)

Gabdullin, N; Khan, S H

2015-01-01

Magnetic shape memory alloys are a new group of ''smart'' materials that exhibit large strain of 6-12% when subjected to magnetic fields. This indicates their enormous potential to be used in different electromagnetic (EM) devices such as actuators, sensors, energy harvesters and dampers. Shape change in MSM materials is controlled by magnetic field and doesn't involve phase transformation, allowing it to overcome a number of disadvantages of conventional shape memory alloys (SMAs). MSM devices are capable of producing large force and stroke output in considerably small dimensions. At the same time they can have fast response and potentially very long lifetime. This paper discusses different modern designs and approaches to MSM actuator design with their advantages and disadvantages. An overview on characteristics of MSM alloys is also presented in order to highlight how different properties of the material influence the total output of a device

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.

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...

Thermoelastic martensite and shape memory effect in ductile Cu-Al-Mn alloys

Science.gov (United States)

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

1996-08-01

Ductile shape memory (SM) alloys of the Cu-AI-Mn system have been developed by controlling the degree of order in the β phase. Additions of Mn to the binary Cu-Al alloy stabilize the β phase and widen the single-phase region to lower temperature and lower Al contents. It is shown that Cu-Al-Mn alloys with low Al contents have either the disordered A2 structure or the ordered L21 structure with a lower degree of order and that they exhibit excellent ductility. The disordered A2 phase martensitically transforms to the disordered Al phase with a high density of twins. The martensite phase formed from the ordered L21 phase has the 18R structure. The SM effect accompanies both the A2 → Al and L21 → 18R martensitic transformations. These alloys exhibit 15 pct strain to failure, 60 to 90 pct rolling reduction without cracking, and 80 to 90 pct recovery from bend test in the martensitic condition. Experimental results on the microstructure, crystal structure, mechanical properties, and shape memory behavior in the ductile Cu-AI-Mn alloys are presented and discussed.

Development of On-line Monitoring System for Shape Memory Alloy Composite

International Nuclear Information System (INIS)

Lee, Jin Kyung; Park, Young Chul; Lee, Min Rae; Lee, Dong Hwa; Lee, Kyu Chang

2003-01-01

A hot press method was use for the optimal manufacturing condition for a shape memory alloy(SMA) composite. The bonding between the matrix and the reinforcement within the SMA composite by the hot press method was strengthened by cold rolling. In this study, the objective was to develop an on-line monitoring system for the prevention of the crack initiation and propagation by shape memory effort of SMA composite. Shape memory effect was used to prevent the SMA composite from cracking. For the system to be developed, an optimal hE parameter should be determined based on the degree of damage and crack initiation. When the SHA composite was heated by the plate heater attached at the composite, the propagating cracks appeared to be controlled by the compressive force of SMA

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.

Vacuum Arc Melting Processes for Biomedical Ni-Ti Shape Memory Alloy

Directory of Open Access Journals (Sweden)

Tsai De-Chang

2015-01-01

Full Text Available This study primarily involved using a vacuum arc remelting (VAR process to prepare a nitinol shape-memory alloy with distinct ratios of alloy components (nitinol: 54.5 wt% to 57 wt%. An advantage of using the VAR process is the adoption of a water-cooled copper crucible, which effectively prevents crucible pollution and impurity infiltration. Optimising the melting production process enables control of the alloy component and facilitates a uniformly mixed compound during subsequent processing. This study involved purifying nickel and titanium and examining the characteristics of nitinol alloy after alloy melt, including its microstructure, mechanical properties, phase transition temperature, and chemical components.

Entropy change linked to the martensitic transformation inmetamagnetic shape memory alloys

Czech Academy of Sciences Publication Activity Database

Recarte, V.; Pérez-Landazábal, J.I.; Sánchez-Alarcos, V.; Zablotskyy, Vitaliy A.; Cesari, E.; Kustov, S.

2012-01-01

Roč. 60, 6-7 (2012), s. 3168-3175 ISSN 1359-6454 Institutional support: RVO:68378271 Keywords : metamagnetic shape memory alloys (MSMAs) * martensitic phase transformation * thermodynamics * transformation entropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.941, year: 2012

Powder metallurgy of NiTi-alloys with defined shape memory properties

International Nuclear Information System (INIS)

Bram, M.; Ahmad-Khanlou, A.; Buchkremer, H.P.; Stoever, D.

2001-01-01

The aim of the present work is the development of fabrication processes for NiTi shape memory alloys by powder metallurgical means. The starting materials used were prealloyed powders as well as elemental powder mixtures. Three techniques seem to be very promising for shaping of NiTi compacts. Hot Isostatic Pressing (HIP) has been examined for the production of dense semi-finished components. A promising technique for the production of dense and porous coatings with an increased wear resistance is Vacuum Plasma Spraying (VPS). Metal Injection Moulding (MIM) is especially suitable for near-net shape fabrication of small components with a complex geometry considering that large numbers of units have to be produced for compensating high tool and process costs. Subsequently, thermal treatments are required to establish defined shape memory properties. The reproducibility and stability of the shape memory effect are main aspects thinking about a production of NiTi components in an industrial scale. (author)

Effect of electrothermal annealing on the transformation behavior of TiNi shape memory alloy and two-way shape memory spring actuated by direct electrical current

International Nuclear Information System (INIS)

Wang, Z.G.; Zu, X.T.; Feng, X.D.; Zhu, S.; Deng, J.; Wang, L.M.

2004-01-01

In this work, the effect of electrothermal annealing on the transformation characterization of TiNi shape memory alloy and the electrothermal actuating characteristics of a two-way shape memory effect (TWSME) extension spring were investigated with direct electrical current. The results showed that with increasing direct electrical current density, the B2→R-phase transformation shifts to a lower temperature and R-phase→B19' shifts to a higher temperature in the cooling process. When annealing electrical current density reached 12.2 A/mm 2 , the R-phase disappeared and austenite transformed into martensite directly. The electrothermal annealing was an effective method of heat treatment in a selected part of shape memory alloy device. The electrothermal actuating characteristics of a TWSME spring showed that the time response and the maximum elongation greatly depended on the magnitude of the electrical current

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...

Shape memory behavior of high strength NiTiHfPd polycrystalline alloys

International Nuclear Information System (INIS)

Karaca, H.E.; Acar, E.; Ded, G.S.; Basaran, B.; Tobe, H.; Noebe, R.D.; Bigelow, G.; Chumlyakov, Y.I.

2013-01-01

Systematic characterization of the shape memory properties of a quaternary Ni 45.3 –Ti 29.7 –Hf 20 –Pd 5 (at.%) polycrystalline alloy was performed in compression after selected aging treatments. Precipitation characteristics were revealed by transmission electron microscopy. The effects of aging temperature and time on transformation temperatures, recoverable and residual strains, and temperature and stress hystereses were determined by differential scanning calorimetry, constant-load thermal cycling experiments and isothermal strain cycling (superelasticity) tests. The crystal structure and lattice parameters of the transforming phases were determined from X-ray diffraction analysis. It was revealed that precipitation hardening significantly improved the shape memory properties of the NiTiHfPd alloy. Under optimum aging conditions, shape memory strains of up to 4% under 1 GPa were possible, and superelasticity experiments resulted in full strain recovery without any plastic deformation, even at stress levels as high as 2 GPa. The NiTiHfPd polycrystalline alloy exhibited very high damping capacity/absorbed energy (30–34 J cm −3 ) and work output (30–35 J cm −3 ), which were attributed to the ability to operate at high stress levels without significant plastic deformation and to a high mechanical hysteresis (>900 MPa) at temperatures ranging from 20 °C to 80 °C

Production and characterization of stainless steel based Fe-Cr-Ni-Mn-Si(-Co) shape memory alloys

International Nuclear Information System (INIS)

Otubo, J.

1995-01-01

It is well known that the Fe based alloys can exhibit shape memory effect due to the γ to ε martensitic transformation. The effect may not be as striking as observed in the NiTi alloy but it might become attractive from the practical point of view. In this work, two compositions of Fe-Cr-Ni-Mn-Si(-Co) stainless steel based shape memory alloy, prepared by the VIM technique, will be presented. The results are good with shape recovery of 95% for a pre-strain of 4% after some training cycles. In terms of workability the alloys produced are worse than the usual AISI304. However, adjusting the thermo-mechanical processing, it is perfectly possible to produce wire as thin as 1,20mm in dia. or down. (orig.)

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...

Characterization of Transformation-Induced Defects in Nickel Titanium Shape Memory Alloys

Science.gov (United States)

Bowers, Matthew L.

Shape memory alloys have remarkable strain recovery properties that make them ideal candidates for many applications that include devices in the automotive, aerospace, medical, and MEMS industries. Although these materials are widely used today, their performance is hindered by poor dimensional stability resulting from cyclic degradation of the martensitic transformation behavior. This functional fatigue results in decreased work output and cyclic accumulation of permanent strain. To date, few studies have taken a fundamental approach to investigating the interaction between plasticity and martensite growth and propagation, which is vitally important to mitigating functional fatigue in future alloy development. The current work focuses on understanding the interplay of these deformation mechanisms in NiTi-based shape memory alloys under a variety of different thermomechanical test conditions. Micron-scale compression testing of NiTi shape memory alloy single crystals is undertaken in an effort to probe the mechanism of austenite dislocation generation. Mechanical testing is paired with post mortem defect analysis via diffraction contrast scanning transmission electron microscopy (STEM). Accompanied by micromechanics-based modeling of local stresses surrounding a martensite plate, these results demonstrate that the previously existing martensite and resulting austenite dislocation substructure are intimately related. A mechanism of transformation-induced dislocation generation is described in detail. A study of pure and load-biased thermal cycling of bulk polycrystalline NiTi is done for comparison of the transformation behavior and resultant defects to the stress-induced case. Post mortem and in situ STEM characterization demonstrate unique defect configurations in this test mode and STEM-based orientation mapping reveals local crystal rotation with increasing thermal cycles. Changes in both martensite and austenite microstructures are explored. The results for

Silver- and Zirconium-added ternary and quaternary TiAu based high temperature shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Wadood, A., E-mail: abdul.wadood@ist.edu.pk [High Temperature Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Department of Materials Science and Engineering, Institute of Space Technology (IST), Near Rawat Toll Plaza, Islamabad (Pakistan); Yamabe-Mitarai, Y. [High Temperature Materials Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

2015-10-15

Low strength in B2 phase, incomplete shape memory effect and high cost of Au are obstacles for the use of Ti–50Au as a high temperature shape memory alloy. We investigated the effects of partial substitution of Ti with Zr and Au with Ag in Ti–Au on phase constitution, phase transformation, and high temperature thermo-mechanical and shape memory properties. Partial substitution of Ti with Zr in Ti–50Au and Ti–40Au–10Ag was found to improve the thermo-mechanical and shape memory effect. However, partial substitution of Au with Ag in Ti–50Au and Ti–50Au–10Zr was found to have negligible effects. Reasons for such different behavior of Zr- and Ag-added Ti–Au alloys are considered. - Highlights: • Au, Ag and Ti, Zr belong to same group. Effects of partial substitution of Au with Ag and Ti with Zr in Ti–Au are investigated. • Zr was found more effective than Ag in improving shape memory and mechanical properties. • Same atomic size of Au and Ag and large size misfit b/w Ti and Zr atoms. • Ag resulted large amount of precipitation in Ti–Au.

X-ray diffraction studies of NiTi shape memory alloys

OpenAIRE

E. Łągiewka; Z. Lekston

2007-01-01

Purpose: The purpose of this paper is to present the results of the investigations of phase transitions of TiNiCo and Ni-rich NiTi shape memory alloys designed for medical applications.Design/methodology/approach: Temperature X-ray diffraction (TXRD), differential scanning calorimetry (DSC), electrical resistivity (ER) and the temperature shape recovery measurements in three-point bending ASTM 2082-01 tests were used.Findings: It has been found in this work that ageing after solution treatme...

Characterization of the Ni-45wt% Ti shape memory alloy rapidly solidified

International Nuclear Information System (INIS)

Anselmo, G.C.S.; Castro, W.B. de; Araujo, C.J. de

2010-01-01

One important challenge of microsystems design is the implementation of miniaturized actuation principles efficient at the micro-scale. Shape memory alloys (SMAs) have early on been considered as a potential solution to this problem as these materials offer attractive properties like a high-power to weight ratio, large deformation and the capability to be processed at the micro-scale. shape memory characteristics of Ni-45wt%Ti alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray. In these experiments particular attention has been paid to change the velocity of cooling wheel from 30 to 50 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on martensitic transformation behaviors and structure are discussed. (author)

Study of Ni50+xMn25Ga25-x (x = 2-11) as high-temperature shape-memory alloys

International Nuclear Information System (INIS)

Ma Yunqing; Jiang Chengbao; Li Yan; Xu Huibin; Wang Cuiping; Liu Xingjun

2007-01-01

Ni 50+x Mn 25 Ga 25-x (x = 2-11) alloys were studied as high-temperature shape-memory alloys, with regard to their microstructure, martensitic transformation behavior and high-temperature shape-memory effect. Single phase of martensite with tetragonal structure was present for x p increase monotonically from 39.1 deg. C for x = 2 to 443.8 deg. C for x = 7, then remain almost constant at 440 deg. C for x ≥ 7. The shape-memory strains of the alloys decreased gradually from 6.1% for x = 4 to 2.8% for x = 8 and 0% for x = 11 under the same pre-strain. The variations of the martensitic transformation temperatures and the shape-memory effects with Ni contents correlate with changes in size factor, electron concentration and precipitation of γ phase

Phase transformation and microstructure evolution of the deformed Ti-30Zr-5Nb shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Qu, Wentao, E-mail: wtqu@xsyu.edu.cn [School of Mechanical Engineering, Xi' an Shiyou University, Xi' an 710065 (China); Sun, Xuguang; Yuan, Bifei [School of Mechanical Engineering, Xi' an Shiyou University, Xi' an 710065 (China); Xiong, Chengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Nie, Yongsheng [Lanzhou Seemine SMA Co. Ltd., Lanzhou 730010 (China)

2017-04-15

The phase transformation and microstructures of the deformed Ti-30Zr-5Nb shape memory alloy were investigated. The X-ray diffraction measurements indicated that the Ti-30Zr-5Nb alloy was composed of a single orthorhombic α″-martensite phase. The alloy exhibited one yielding behavior in the tensile test, with a critical stress of ~ 600 MPa and a tensile strain of approximately 15%. A shape memory recovery accompanied by a permanent strain was exhibited in the deformed alloys when heated at 873 K. The permanent strain increased with increasing pre-strain. The microstructure evolution of the deformed alloy was investigated by transmission electron microscopy. The results showed that the martensite reorientation occurred and the dislocations were generated during deformation. The alloy displayed a reversible martensite transformation start temperature as high as 763 K. However, no strain-induced martensite stabilization was found in the deformed alloy with different pre-strain levels, potentially because the large chemical energy of the Ti-30Zr-5Nb alloy depressed the effects of the elastic energy and the dissipative energy. - Highlights: • Ti-30Zr-5Nb alloy is composed of single orthorhombic α″-martensite phase with M{sub s} of 721 K. • No martensite stabilization has been found in Ti-30Zr-5Nb alloy with different pre-strain. • Ti-30Zr-5Nb shows the maximum shape memory effect of 2.75% with a pre-strain of 8%.

Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

International Nuclear Information System (INIS)

Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

2015-01-01

Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications

Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

Energy Technology Data Exchange (ETDEWEB)

Czarnowska, Elżbieta [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Borowski, Tomasz [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Sowińska, Agnieszka [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Lelątko, Józef [Silesia University, Faculty of Computer Science and Materials Science, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Wierzchoń, Tadeusz, E-mail: twierz@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland)

2015-04-15

Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

Shape memory effect and super elasticity. Its dental applications.

Science.gov (United States)

Kotian, R

2001-01-01

The shape memory alloys are quite fascinating materials characterized by a shape memory effect and super elasticity which ordinary metals do not have. This unique behaviour was first found in a Au-47.5 at % Cd alloy in 1951, and was published in 1963 by the discovery of Ti-Ni alloy. Shape memory alloys now being practically used as new functional alloys for various dental and medical applications.

[Utility of nickel-titanium shape memory alloys of vertebral body reduction fixator with assisted distraction bar].

Science.gov (United States)

Man, Yi; Zheng, Yue-huan; Cao, Peng; Chen, Bo; Zheng, Tao; Sun, Chang-hui; Lu, Jiong

2011-06-07

To test the nickel-titanium (Ni-Ti) shape memory alloys of vertebral body reduction fixator with assisted distraction bar for the treatment of traumatic and osteoporotic vertebral body fracture. A Ni-Ti shape memory alloys of vertebral body reduction fixator with assisted distraction bar was implanted into the compressed fracture specimens through vertebral pedicle with the radiographic monitoring to reduce the collapsed endplate as well as distract the compressed vertebral fracture. Radiographic film and computed tomographic reconstruction technique were employed to evaluate the effects of reduction and distraction. A biomechanic test machine was used to measure the fatigue and the stability of deformation of fixation segments. Relying on the effect of temperature shape memory, such an assembly could basically reduce the collapsed endplate as well as distract the compressed vertebral fracture. And when unsatisfied results of reduction and distraction occurred, its super flexibility could provide additional distraction strength. A Ni-Ti shape memory alloys of vertebral body reduction fixator with assisted distraction bar may provide effective endplate reduction, restore the vertebral height and the immediate biomechanic spinal stability. So the above assembly is indicated for the treatment of traumatic and osteoporotic vertebral body fracture.

Mechanical response of nitrogen ion implanted NiTi shape memory alloy

International Nuclear Information System (INIS)

Kucharski, S.; Levintant-Zayonts, N.; Luckner, J.

2014-01-01

Highlights: • The effect of ion implantation process on shape memory alloy was investigated. • In the implantation process both surface layer and bulk material are modified. • The microstructure is modified and superelastic effect is destroyed in surface layer. • The parameters of superelastic phenomena are changed in bulk material. - Abstract: In the paper a change of material (mechanical) parameters of NiTi shape memory alloy subjected to ion implantation treatment is investigated. The spherical indentation tests in micro- and nano-scale and tension test have been performed to study an evolution of local superelastic effect in different volumes of nonimplanted and nitrogen ion implanted NiTi alloy. The differential scanning calorimetry has been applied to measure the change of characteristic temperatures due to ion implantation treatment. The structure of implanted material has been investigated using electron microscopy technique. It has been found that the ion implantation process changes the properties not only in a thin surface layer but also in bulk material. In the layer the pseudoelastic effect is destroyed, and in the substrate is preserved, however its parameters are changed. The characteristic phase transformation temperatures in substrate are also modified

The role of adaptive martensite in magnetic shape memory alloys

Czech Academy of Sciences Publication Activity Database

Niemann, R.; Rößler, U.K.; Gruner, M.E.; Heczko, Oleg; Schultz, L.; Fähler, S.

2012-01-01

Roč. 14, č. 8 (2012), s. 562-581 ISSN 1438-1656 Grant - others:AVČR(CZ) M100100913 Institutional research plan: CEZ:AV0Z10100520 Keywords : Ni-Mn-Ga * magnetic shape memory alloy * ferromagnetic martensite * modulated structure * adaptive phase * mobility of twin boundary Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.608, year: 2012

The pseudoelasticity and the shape memory effect in CoNiAl alloys

Czech Academy of Sciences Publication Activity Database

Kopeček, Jaromír; Jarošová, Markéta; Jurek, Karel; Heczko, Oleg

2014-01-01

Roč. 21, č. 1 (2014), s. 43-48 ISSN 1335-0803 R&D Projects: GA ČR(CZ) GA101/09/0702; GA ČR GAP107/10/0824; GA ČR(CZ) GAP107/11/0391; GA AV ČR IAA100100920 Institutional support: RVO:68378271 Keywords : shape memory alloys * co-alloys * metallography * martensitic transition * stress induced martensite Subject RIV: BM - Solid Matter Physics ; Magnetism

An approach to modeling tensile–compressive asymmetry for martensitic shape memory alloys

International Nuclear Information System (INIS)

Zaki, Wael

2010-01-01

In this paper, the asymmetric tensile–compressive behavior of shape memory alloys is modeled based on the mathematical framework of Raniecki and Mróz (2008 Acta Mech. 195 81–102). The framework allows the definition of smooth, non-symmetric, pressure-insensitive yield functions that are used here to incorporate tensile–compressive modeling capabilities into the Zaki–Moumni (ZM) model for shape memory materials. It is found that, despite some increased complexity, the generalized model is capable of producing satisfactory results that agree with uniaxial experimental data taken from the literature

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.

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)

A Homogenized Free Energy Model for Hysteresis in Thin-film Shape Memory Alloys

National Research Council Canada - National Science Library

Massad, Jordan E; Smith, Ralph C

2004-01-01

Thin-film shape memory alloys (SMAs) have become excellent candidates for microactuator fabrication in MEMS due to their capability to achieve very high work densities, produce large deformations, and generate high stresses...

Magnetic and calorimetric investigations of ferromagnetic shape memory alloy Ni54Fe19Ga27

International Nuclear Information System (INIS)

Sharma, V K; Chattopadhyay, M K; Kumar, Ravi; Ganguli, Tapas; Kaul, Rakesh; Majumdar, S; Roy, S B

2007-01-01

We report results of magnetization and differential scanning calorimetry measurements in the ferromagnetic shape memory alloy Ni 54 Fe 19 Ga 27 . This alloy undergoes an austenite-martensite phase transition in its ferromagnetic state. The nature of the ferromagnetic state, both in the austenite and the martensite phase, is studied in detail. The ferromagnetic state in the martensite phase is found to have higher anisotropy energy as compared with the austenite phase. The estimated anisotropy constant is comparable to that of a well-studied ferromagnetic shape memory alloy system NiMnGa. Further, the present study highlights various interesting features accompanying the martensitic transition (MT). These features suggest the possibility of either a premartensitic transition and/or an inter-MT in this system

Ageing effects in a Cu-Al-Ni shape memory alloy

Czech Academy of Sciences Publication Activity Database

Daříček, Tomáš; Lašek, Jiří; Zárubová, Niva; Novák, Václav; Bartuška, Pavel

2001-01-01

Roč. 11, - (2001), s. Pr8-179-Pr8-184 ISSN 1155-4339 R&D Projects: GA AV ČR IAA1010909; GA AV ČR IAA1010817 Institutional research plan: CEZ:AV0Z1010914 Keywords : Cu-Al-Ni alloy * shape memory * martensitic transformation * resistometry Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.401, year: 2001

RF magnetron sputtered TiNiCu shape memory alloy thin film

International Nuclear Information System (INIS)

Fu Yongqing; Du Hejun

2003-01-01

Shape memory alloys (SMAs) offer a unique combination of novel properties, such as shape memory effect, super-elasticity, biocompatibility and high damping capacity, and thin film SMAs have the potential to become a primary actuating mechanism for micro-actuators. In this study, TiNiCu films were successfully prepared by mix sputtering of a Ti 55 Ni 45 target with a separated Cu target. Crystalline structure, residual stress and phase transformation properties of the TiNiCu films were investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and curvature measurement methods. Effects of the processing parameters on the film composition, phase transformation and shape-memory effects were analyzed. Results showed that films prepared at a high Ar gas pressure exhibited a columnar structure, while films deposited at a low Ar gas pressure showed smooth and featureless structure. Chemical composition of TiNiCu thin films was dependent on the DC power of copper target. DSC, XRD and curvature measurement revealed clearly the martensitic transformation of the deposited TiNiCu films. When the free-standing film was heated and cooled, a 'two-way' shape-memory effect can be clearly observed

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)

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.

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.

Transformation behavior and shape memory properties of Ti50Ni15Pd25Cu10 high temperature shape memory alloy at various aging temperatures

International Nuclear Information System (INIS)

Rehman, Saif ur; Khan, Mushtaq; Nusair Khan, A.; Ali, Liaqat; Zaman, Sabah; Waseem, Muhammad; Ali, Liaqat; Jaffery, Syed Husain Imran

2014-01-01

This research presents an insight into the effect of various aging temperatures on the microstructure, hardness, phase transformation behavior and shape memory properties of Ti 50 Ni 15 Pd 25 Cu 10 high temperature shape memory alloy. The aging temperature was varied from 350 °C to 750 °C, whereas the shape memory properties were evaluated at 100–500 MPa. It was observed that the mentioned properties were strongly dependent on the aging temperatures. Based on the results obtained from scanning electron microscopy, X-ray diffractometry, microhardness testing, differential scanning calorimetry and thermomechanical testing, the aging temperatures can be divided into three ranges. At low aging temperatures (350 °C and below), the properties of the alloy remained the same as were found for solution treated sample, however at intermediate aging temperatures (400–600 °C) the properties of the alloy were changed significantly. Due to the formation of precipitates, the hardness was increased, whereas the phase transformation temperatures and work output were decreased considerably. The recovery ratio was found to be improved for intermediate aging temperatures. At high aging temperatures (650 °C and above), the hardness was decreased and the phase transformation temperatures were increased. Phase transformation temperature at the aging temperature of 750 °C was found to be increased significantly as compared to solution treated sample

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.)

Mechanical and shape memory properties of porous Ni50.1Ti49.9 alloys manufactured by selective laser melting.

Science.gov (United States)

Taheri Andani, Mohsen; Saedi, Soheil; Turabi, Ali Sadi; Karamooz, M R; Haberland, Christoph; Karaca, Haluk Ersin; Elahinia, Mohammad

2017-04-01

Near equiatomic NiTi shape memory alloys were fabricated in dense and designed porous forms by Selective Laser Melting (SLM) and their mechanical and shape memory properties were systematically characterized. Particularly, the effects of pore morphology on their mechanical responses were investigated. Dense and porous NiTi alloys exhibited good shape memory effect with a recoverable strain of about 5% and functional stability after eight cycles of compression. The stiffness and residual plastic strain of porous NiTi were found to depend highly on the pore shape and the level of porosity. Since porous NiTi structures have lower elastic modulus and density than dense NiTi with still good shape memory properties, they are promising materials for lightweight structures, energy absorbers, and biomedical implants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Functional Properties of Porous Ti-48.0 at.% Ni Shape Memory Alloy Produced by Self-Propagating High-Temperature Synthesis

Science.gov (United States)

Resnina, Natalia; Belyaev, Sergey; Voronkov, Andrew

2018-03-01

The functional behavior of the porous shape memory alloy produced by self-propagating high-temperature synthesis from the Ti-48.0 at.% Ni powder mixture was studied. It was found that a large unelastic strain recovered on unloading and it was not attributed to the pseudoelasticity effect. A decrease in deformation temperatures did not influence the value of strain that recovered on unloading, while the effective modulus decreased from 1.9 to 1.44 GPa. It was found that the porous Ti-48.0 at.% Ni alloy revealed the one-way shape memory effect, where the maximum recoverable strain was 5%. The porous Ti-48.0 at.% Ni alloy demonstrated the transformation plasticity and the shape memory effects on cooling and heating under a stress. An increase in stress did not influence the shape memory effect value, which was equal to 1%. It was shown that the functional properties of the porous alloy were determined by the TiNi phase consisted of the two volumes Ti49.3Ni50.7 and Ti50Ni50 where the martensitic transformation occurred at different temperatures. The results of the study showed that the existence of the Ti49.3Ni50.7 volumes in the porous Ti-48.0 at.% Ni alloy improved the functional properties of the alloy.

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

Deformation of shape memory alloys associated with twinned domain re-configurations

International Nuclear Information System (INIS)

Liu Yong; Van Humbeeck, J.; Xie Zeliang; Delaey, L.

1999-01-01

Most of the applications of shape memory alloys (SMAs) imply deformation of martensite; it is therefore one of the fundamental research topics on the shape memory effect. So far, several classifications of the deformation mechanisms have been made as a function of deformation amplitude. However, the deformation details of martensitic SMAs are still not yet satisfactorily understood and these classifications need to be refined, because several incoherencies have been found lately by mechanical testing and transmission electron microscopy (TEM) observations. The present work summarizes some new results on the deformation mechanisms of martensitic NiTi SMAs under tension. As a result, the deformation process of martensite twins as a function of the deformation strain amplitude is refined. (orig.)

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

KAUST Repository

Douglas, Craig C.; Efendiev, Yalchin; Popov, Peter; Calo, Victor M.

2012-01-01

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

Assessment of Shape Memory Alloys - From Atoms To Actuators - Via In Situ Neutron Diffraction

Science.gov (United States)

Benafan, Othmane

2014-01-01

As shape memory alloys (SMAs) become an established actuator technology, it is important to identify the fundamental mechanisms responsible for their performance by understanding microstructure performance relationships from processing to final form. Yet, microstructural examination of SMAs at stress and temperature is often a challenge since structural changes occur with stress and temperature and microstructures cannot be preserved through quenching or after stress removal, as would be the case for conventional materials. One solution to this dilemma is in situ neutron diffraction, which has been applied to the investigation of SMAs and has offered a unique approach to reveal the fundamental micromechanics and microstructural aspects of bulk SMAs in a non-destructive setting. Through this technique, it is possible to directly correlate the micromechanical responses (e.g., internal residual stresses, lattice strains), microstructural evolutions (e.g., texture, defects) and phase transformation properties (e.g., phase fractions, kinetics) to the macroscopic actuator behavior. In this work, in situ neutron diffraction was systematically employed to evaluate the deformation and transformation behavior of SMAs under typical actuator conditions. Austenite and martensite phases, yield behavior, variant selection and transformation temperatures were characterized for a polycrystalline NiTi (49.9 at. Ni). As the alloy transforms under thermomechanical loading, the measured textures and lattice plane-level variations were directly related to the cyclic actuation-strain characteristics and the dimensional instability (strain ratcheting) commonly observed in this alloy. The effect of training on the shape memory characteristics of the alloy and the development of two-way shape memory effect (TWSME) were also assessed. The final conversion from a material to a useful actuator, typically termed shape setting, was also investigated in situ during constrained heatingcooling and

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.

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.

The effect of applied stress on the shape memory behavior of TiNi-based alloys with different consequences of martensitic transformations

International Nuclear Information System (INIS)

Meisner, L.L.; Sivokha, V.P.

2004-01-01

The development of plastic deformation and shape memory behavior of the Ti 49.5 Ni 50.5 , Ti 50 Ni 34 Pt 16 , Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloys are studied. The alloys differ by consequences of martensitic transformations (MT). It is found that the behavior of both accumulated and returned strain components exhibit some features in the alloys under consideration. The strain-temperature diagrams of the Ti 49.5 Ni 50.5 alloy with the B2↔B19' MT are of the one-step form. There are three stages on the strain-stress curves of this alloy depending on value of the applied mechanical torque. The regularity of plastic behavior of the Ti 50 Ni 34 Pt 16 alloy with the B2↔B19 transformation is similar to that of the Ti 49.5 Ni 50.5 alloy. The strain-stress diagram has three stages. However, there is a significant difference in the shape memory behavior of this alloy. The shape-memory behavior of the Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloy corresponds to the two-stage nature of its B2↔B19↔B19' MT. The deformation mechanisms for these stages have their features in contrast to those of the foregoing alloys. The strain and temperature parameters of the shape memory effect and plastic behavior of the TiNi-based alloys are also examined

Texture memory and strain-texture mapping in a NiTi shape memory alloy

International Nuclear Information System (INIS)

Ye, B.; Majumdar, B. S.; Dutta, I.

2007-01-01

The authors report on the near-reversible strain hysteresis during thermal cycling of a polycrystalline NiTi shape memory alloy at a constant stress that is below the yield strength of the martensite. In situ neutron diffraction experiments are used to demonstrate that the strain hysteresis occurs due to a texture memory effect, where the martensite develops a texture when it is cooled under load from the austenite phase and is thereafter ''remembered.'' Further, the authors quantitatively relate the texture to the strain by developing a calculated strain-texture map or pole figure for the martensite phase, and indicate its applicability in other martensitic transformations

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.

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.

Orthodontic applications of a superelastic shape-memory alloy model

International Nuclear Information System (INIS)

Glendenning, R.W.; Enlow, R.L.

2000-01-01

During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

Thermodynamic constitutive model for load-biased thermal cycling test of shape memory alloy

International Nuclear Information System (INIS)

Young, Sung; Nam, Tae-Hyun

2013-01-01

Graphical abstract: - Highlights: • Thermodynamic calculation model for martensitic transformation of shape memory alloy was proposed. • Evolution of the self-accommodation was considered independently by a rate-dependent kinetic equation. • Finite element calculation was conducted for B2–B19′ transformation of Ti–44.5Ni–5Cu–0.5 V (at.%). • Three-dimensional numerical results predict the macroscopic strain under bias loading accurately. - Abstract: This paper presents a three-dimensional calculation model for martensitic phase transformation of shape memory alloy. Constitutive model based on thermodynamic theory was provided. The average behavior was accounted for by considering the volume fraction of each martensitic variant in the material. Evolution of the volume fraction of each variant was determined by a rate-dependent kinetic equation. We assumed that nucleation rate is faster for the self-accommodation than for the stress-induced variants. Three-dimensional finite element analysis was conducted and the results were compared with the experimental data of Ti–44.5Ni–5Cu–0.5 V (at.%) alloy under bias loading

Coupled magnetoelastic waves in ferromagnetic shape-memory alloys

Science.gov (United States)

Bar'Yakhtar, V. G.; Danilevich, A. G.; L'Vov, V. A.

2011-10-01

The theory of the spectra of coupled magnetoelastic waves in ferromagnetic shape-memory alloys (FSMA) is developed. The possibility of an abnormally strong coupling of spin waves with the soft elastic mode at approaching the martensitic transformation (MT) temperature is disclosed. In particular the magnetoelastic waves in Ni-Mn-Ga single crystals are considered. A considerable (by an order of magnitude) reduction of the shear elastic modulus and an appropriate lowering of the transversal velocity of sound in the applied magnetic field are predicted. Optimum conditions for the experimental observation of the predicted effects are specified.

Proof of Concept Study for the Design, Manufacturing, and Testing of a Patient-Specific Shape Memory Device for Treatment of Unicoronal Craniosynostosis.

Science.gov (United States)

Borghi, Alessandro; Rodgers, Will; Schievano, Silvia; Ponniah, Allan; Jeelani, Owase; Dunaway, David

2018-01-01

Treatment of unicoronal craniosynostosis is a surgically challenging problem, due to the involvement of coronal suture and cranial base, with complex asymmetries of the calvarium and orbit. Several techniques for correction have been described, including surgical bony remodeling, early strip craniotomy with orthotic helmet remodeling and distraction. Current distraction devices provide unidirectional forces and have had very limited success. Nitinol is a shape memory alloy that can be programmed to the shape of a patient-specific anatomy by means of thermal treatment.In this work, a methodology to produce a nitinol patient-specific distractor is presented: computer tomography images of a 16-month-old patient with unicoronal craniosynostosis were processed to create a 3-dimensional model of his skull and define the ideal shape postsurgery. A mesh was produced from a nitinol sheet, formed to the ideal skull shape and heat treated to be malleable at room temperature. The mesh was afterward deformed to be attached to a rapid prototyped plastic skull, replica of the patient initial anatomy. The mesh/skull construct was placed in hot water to activate the mesh shape memory property: the deformed plastic skull was computed tomography scanned for comparison of its shape with the initial anatomy and with the desired shape, showing that the nitinol mesh had been able to distract the plastic skull to a shape close to the desired one.The shape-memory properties of nitinol allow for the design and production of patient-specific devices able to deliver complex, preprogrammable shape changes.

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.)

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...

A simple method to treat an ingrowing toenail with a shape-memory alloy device.

Science.gov (United States)

Ishibashi, Masaya; Tabata, Nobuko; Suetake, Takaki; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Yamauchi, Kiyoshi; Ishida, Kiyohito

2008-01-01

An ingrowing toenail has no definitive treatment. Previously, effective methods were complicated but easy ones had less effect. We show both an easy and an effective way with Cu-Al-Mn-based shape-memory alloys (SMAs). They have a characteristic shape which patients themselves can detach easily without any pain. But they also have enough corrective force. Cu-based SMAs cost much less than Ni-Ti-based alloys. Despite not being appropriate for all cases of ingrowing toenails, it is an easy, effective and less costly alternative.

Martensitic phase transformation in shape-memory alloys

International Nuclear Information System (INIS)

Golestaneh, A.A.

1979-01-01

Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M → P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M → P → M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface

On the thermomechanical deformation of silver shape memory nanowires

International Nuclear Information System (INIS)

Park, Harold S.; Ji, Changjiang

2006-01-01

We present an analysis of the uniaxial thermomechanical deformation of single-crystal silver shape memory nanowires using atomistic simulations. We first demonstrate that silver nanowires can show both shape memory and pseudoelastic behavior, then perform uniaxial tensile loading of the shape memory nanowires at various deformation temperatures, strain rates and heat transfer conditions. The simulations show that the resulting mechanical response of the shape memory nanowires depends strongly upon the temperature during deformation, and can be fundamentally different from that observed in bulk polycrystalline shape memory alloys. The energy and temperature signatures of uniaxially loaded silver shape memory nanowires are correlated to the observed nanowire deformation, and are further discussed in comparison to bulk polycrystalline shape memory alloy behavior

Alloying effect on K shell X-ray fluorescence cross-sections and yields in Ti-Ni based shape memory alloys

Directory of Open Access Journals (Sweden)

Bünyamin Alım

2018-04-01

Full Text Available K shell X-ray fluorescence cross-sections (σKα, σKβ and σK, and K shell fluorescence yields (ωK of Ti, Ni both in pure metals and in different alloy compositions (TixNi1-x; x = 0.3, 0.4, 0.5, 0.6, 0.7 were measured by using energy dispersive X-ray fluorescence (EDXRF technique. The samples were excited by 22.69 keV X-rays from a 10 mCi Cd-109 radioactive point source and K X rays emitted by samples were counted by a high resolution Si(Li solid-state detector coupled to a 4 K multichannel analyzer (MCA. The alloying effects on the X-ray fluorescence (XRF parameters of Ti-Ni shape memory alloys (SMAs were investigated. It is clearly observed that alloying effect causes to change in K shell XRF parameter values in Ti-Ni based SMAs for different compositions of x. Also, the present investigation makes it possible to perform reliable interpretation of experimental σKα, σKβ and ωK values for Ti and Ni in SMAs and can also provide quantitative information about the changes of K shell X-ray fluorescence cross sections and fluorescence yields of these metals with alloy composition. Keywords: Alloying effect, XRF, K X-ray fluorescence cross-section, K shell fluorescence yield, Shape memory alloy

Additive Manufacturing of NiTiHf High Temperature Shape Memory Alloy

Science.gov (United States)

Benafan, Othmane; Bigelow, Glen S.; Elahinia, Mohammad; Moghaddam, Narges Shayesteh; Amerinatanzi, Amirhesam; Saedi, Soheil; Toker, Guher Pelin; Karaca, Haluk

2017-01-01

Additive manufacturing of a NiTi-20Hf high temperature shape memory alloy (HTSMA) was investigated. A selective laser melting (SLM) process by Phenix3D Systems was used to develop components from NiTiHf powder (of approximately 25-75 m particle fractions), and the thermomechanical response was compared to the conventionally vacuum induction skull melted counterpart. Transformation temperatures of the SLM material were found to be slightly lower due to the additional oxygen pick up from the gas atomization and melting process. The shape memory response in compression was measured for stresses up to 500 MPa, and transformation strains were found to be very comparable (Up to 1.26 for the as-extruded; up to 1.52 for SLM).

Processing and Characterization of NiTi Shape Memory Alloy Particle Reinforced Sn-In Solders

National Research Council Canada - National Science Library

Chung, Kohn C

2006-01-01

.... In previous work, it was proposed that reinforcement of solder by NiTi shape memory alloy particles to form smart composite solder reduces the inelastic strain of the solder and hence, may enhance...

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

Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

International Nuclear Information System (INIS)

Nicholson, D E; Vaidyanathan, R; Padula II, S A; Noebe, R D; Benafan, O

2014-01-01

Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni 19.5 Ti 50.5 Pd 25 Pt 5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance. (paper)

Orthodontic applications of a superelastic shape-memory alloy model

Energy Technology Data Exchange (ETDEWEB)

Glendenning, R.W.; Enlow, R.L. [Otago Univ., Dunedin (New Zealand). Dept. of Math. and Stat.; Hood, J.A.A. [Dept. of Oral Sciences and Orthodontics, Univ. of Otago, Dunedin (New Zealand)

2000-07-01

During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

Texture development and anisotropic behaviour of a TI-44.2NI4.9CU (AT.%) shape memory alloy

NARCIS (Netherlands)

Zhao, L.

1997-01-01

The objective of this work was to determine the relationship between texture development and anisotropy of shape memory properties. A commercial Ti-45Ni-5Cu (at.%) shape memory alloy was selected. Textures were developed by controlling rolling parameters, such as rolling temperature, intermediate

Development of elastic properties of Cu-based shape memory alloys during martensitic transformation

Czech Academy of Sciences Publication Activity Database

Novák, Václav; Landa, Michal; Šittner, Petr

2004-01-01

Roč. 115, - (2004), s. 363 ISSN 1155-4339 Institutional research plan: CEZ:AV0Z1010914 Keywords : Cu-based shape memory alloy s * elastic properties * elastic constants * modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.294, year: 2004

Point defects behavior in beta Cu-based shape memory alloys

International Nuclear Information System (INIS)

Romero, R.; Somoza, A.

1999-01-01

A summary of positron annihilation spectroscopy data relating to the point defect behavior after quenching and to thermal equilibrium in β-phase Cu-based shape memory alloys Cu-Zn-Al and Cu-Al-Be is presented. Particular attention is given to the initial concentration of quenched-in vacancies as a function of the quenching temperature, migration of the retained point defects with aging temperature and time, and the vacancy formation and migration energies. (orig.)

Estimation of Transformation Temperatures in Ti-Ni-Pd Shape Memory Alloys

Science.gov (United States)

Narayana, P. L.; Kim, Seong-Woong; Hong, Jae-Keun; Reddy, N. S.; Yeom, Jong-Taek

2018-03-01

The present study focused on estimating the complex nonlinear relationship between the composition and phase transformation temperatures of Ti-Ni-Pd shape memory alloys by artificial neural networks (ANN). The ANN models were developed by using the experimental data of Ti-Ni-Pd alloys. It was found that the predictions are in good agreement with the trained and unseen test data of existing alloys. The developed model was able to simulate new virtual alloys to quantitatively estimate the effect of Ti, Ni, and Pd on transformation temperatures. The transformation temperature behavior of these virtual alloys is validated by conducting new experiments on the Ti-rich thin film that was deposited using multi target sputtering equipment. The transformation behavior of the film was measured by varying the composition with the help of aging treatment. The predicted trend of transformational temperatures was explained with the help of experimental results.

Tribological characteristics of ceramic conversion treated NiTi shape memory alloy

International Nuclear Information System (INIS)

Ju, X; Dong, H

2007-01-01

NiTi shape memory alloys are very attractive for medical implants and devices (such as orthopaedic and orthodontic implants) and various actuators. However, wear is a major concern for such applications and a novel surface engineering process, ceramic conversion treatment, has recently been developed to address this problem. In this study, the tribological characteristics of ceramic conversion treated NiTi alloy have been systematically investigated under dry unidirectional wear, reciprocating-corrosion wear and fretting-corrosion wear condition. Based on the experimental results, the wear behaviour under different conditions is compared and wear mechanisms involved are discussed

Tribological characteristics of ceramic conversion treated NiTi shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Ju, X; Dong, H [Department of Metallurgy and Materials, School of Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2007-09-21

NiTi shape memory alloys are very attractive for medical implants and devices (such as orthopaedic and orthodontic implants) and various actuators. However, wear is a major concern for such applications and a novel surface engineering process, ceramic conversion treatment, has recently been developed to address this problem. In this study, the tribological characteristics of ceramic conversion treated NiTi alloy have been systematically investigated under dry unidirectional wear, reciprocating-corrosion wear and fretting-corrosion wear condition. Based on the experimental results, the wear behaviour under different conditions is compared and wear mechanisms involved are discussed.

Influence of atomic ordering on elastocaloric and magnetocaloric effects of a Ni–Cu–Mn–Ga ferromagnetic shape memory alloy

International Nuclear Information System (INIS)

Huang, Chonghui; Wang, Yu; Tang, Zhao; Liao, Xiaoqi; Yang, Sen; Song, Xiaoping

2015-01-01

Highlights: • Ni 51 Cu 4 Mn 20 Ga 25 alloy exhibits normal elastocaloric and magnetocaloric effects. • L2 1 atomic order of the alloy is increased after annealing at 773 K for 10 h. • Increasing L2 1 atomic order improves its elastocaloric and magnetocaloric effects. • Atomic ordering modifies the magnetic and martensitic transitions of the system. - Abstract: The coexisting elastocaloric and magnetocaloric effects in ferromagnetic shape memory alloys have attracted much attention for the potential application in solid state refrigeration. Previous studies show that the L2 1 atomic ordering of Heusler ferromagnetic shape memory alloys plays important role on their magnetocaloric effect. However, no research work investigates the effect of atomic ordering on their elastocaloric effect yet. In this study, we investigated the influence of atomic ordering on the elastocaloric and magnetocaloric effects of a Ni 51 Cu 4 Mn 20 Ga 25 ferromagnetic shape memory alloy. The alloy exhibits normal elastocaloric effect and normal magnetocaloric effect near room temperature. Moreover, we found that the enhancement of atomic order in this alloy can greatly increase the entropy change and refrigeration capacity of its elastocaloric and magnetocaloric effects. This is attributed to that the atomic ordering modifies the magnetic and martensitic transitions of the system

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.)

Sn buffered by shape memory effect of NiTi alloys as high-performance anodes for lithium ion batteries

International Nuclear Information System (INIS)

Hu Renzong; Zhu Min; Wang Hui; Liu Jiangwen; Liuzhang Ouyang; Zou Jin

2012-01-01

By applying the shape memory effect of the NiTi alloys to buffer the Sn anodes, we demonstrate a simple approach to overcome a long-standing challenge of Sn anode in the applications of Li-ion batteries – the capacity decay. By supporting the Sn anodes with NiTi shape memory alloys, the large volume change of Sn anodes due to lithiation and delithiation can be effectively accommodated, based on the stress-induced martensitic transformation and superelastic recovery of the NiTi matrix respectively, which leads to a decrease in the internal stress and closing of cracks in Sn anodes. Accordingly, stable cycleability (630 mA h g −1 after 100 cycles at 0.7C) and excellent high-rate capabilities (478 mA h g −1 at 6.7C) were attained with the NiTi/Sn/NiTi film electrode. These shape memory alloys can also combine with other high-capacity metallic anodes, such as Si, Sb, Al, and improve their cycle performance.

Vacancy dynamic in Ni-Mn-Ga ferromagnetic shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Merida, D., E-mail: david.merida@ehu.es [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); García, J. A. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); BC Materials (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain); Sánchez-Alarcos, V.; Pérez-Landazábal, J. I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

2014-06-09

Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173 K show a vacancy concentration of 1100 ± 200 ppm. The vacancy migration and formation energies have been estimated to be 0.55 ± 0.05 eV and 0.90 ± 0.07 eV, respectively.

Examination of temperature-induced shape memory of uranium--5.3-to 6.9 weight percent niobium alloys

International Nuclear Information System (INIS)

Hemperly, V.C.

1976-01-01

The uranium-niobium alloy system was examined in the range of 5.3-to-6.9 weight percent niobium with respect to shape memory, mechanical properties, metallography, Coefficients of linear thermal expansion, and differential thermal analysis. Shape memory increased with increasing niobium levels in the study range. There were no useful correlations found between shape memory and the other tests. Coefficients of linear thermal expansion tests of as-quenched 5.8 and 6.2 weight percent niobium specimens, but not 5.3 and 6.9 weight percent niobium specimens, had a contraction component on heating, but the phenomenon was not a contributor to shape memory

Effect of milling duration on the evolution of shape memory properties in a powder processed Cu-Al-Ni-Ti alloy

Energy Technology Data Exchange (ETDEWEB)

Sharma, Mohit; Gupta, Gaurav K.; Shafeeq, Muhamed M.; Modi, Om P.; Prasad, Braj K. [CSIR - Advanced Materials and Processes Research Institute, Bhopal (India)

2013-09-15

The present work describes the effect of milling duration on the properties of a powder metallurgy processed Cu-Al-Ni-Ti shape memory alloy employing mechanical alloying. Powder mixtures milled for different durations were sintered in order to investigate the formation of solid solution and evolution of martensitic structure. The idea was to optimize the duration of milling (mechanical alloying) to obtain chemical homogeneity as well as shape memory properties in the processed material without undergoing extensive post homogenization treatment. The martensitic structure was noted to evolve in the powder mix milled for at least 16 hrs, whereas complete transformation to martensite occurred after milling for 40 hrs. Interestingly, the dissolution of alloying elements (to form the {beta} phase prior to the formation of martensite) was noted to complete partially only during mechanical alloying for 40 hrs and remaining during subsequent sintering for 1 hr. The hot pressed compacts of the powders milled for 40 hrs were chemically homogeneous and consisted of fully martensite phase, which is essential for the realization of shape memory properties. They also revealed almost 100% shape recovery at the applied pre-strain levels of 1 and 2%. (orig.)

Martensitic transformation and shape memory effect in polycomponent TiNi-based alloys

International Nuclear Information System (INIS)

Khachin, V.N.; Voronin, V.P.; Sivokha, V.P.; Pushin, V.G.

1995-01-01

The results of martesitic transformation (MT) and shape memory effect (SME) in quaternary Ti 50 (NiCoCu) 50 , Ti 50 (NiFeCu) 50 and (TiAl) 50 (NiCu) 50 alloys studies are generalized in this paper. On alloying TiNi simultaneously by two elements, their individual effect on MT and SME is conserved. Martensitic transformations B2→R and B2→B19' are almost simultaneously realizing in a binary TiNi. One can selectively control each of two MT channels by selecting property of alloying elements. As a result, the alloys having any sequences of MT and their realizations temperatures, including simultaneous realization of two MTs at low temperatures, which was not observed earlier, can be produced. (orig.)

Performance of Integrated Fiber Optic, Piezoelectric, and Shape Memory Alloy Actuators/Sensors in Thermoset Composites

Science.gov (United States)

Trottier, C. Michael

1996-01-01

Recently, scientists and engineers have investigated the advantages of smart materials and structures by including actuators in material systems for controlling and altering the response of structural environments. Applications of these materials systems include vibration suppression/isolation, precision positioning, damage detection and tunable devices. Some of the embedded materials being investigated for accomplishing these tasks include piezoelectric ceramics, shape memory alloys, and fiber optics. These materials have some benefits and some shortcomings; each is being studied for use in active material design in the SPICES (Synthesis and Processing of Intelligent Cost Effective Structures) Consortium. The focus of this paper concerns the manufacturing aspects of smart structures by incorporating piezoelectric ceramics, shape memory alloys and fiber optics in a reinforced thermoset matrix via resin transfer molding (RTM).

Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

Science.gov (United States)

Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

2005-01-01

High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

Science.gov (United States)

Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

2013-10-01

We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

Characterization of the shape memory properties of a Ni45.3Ti39.7Hf10Pd5 alloy

International Nuclear Information System (INIS)

Acar, E.; Karaca, H.E.; Tobe, H.; Noebe, R.D.; Chumlyakov, Y.I.

2013-01-01

Highlights: •Ni 45.3 Ti 39.7 Hf 10 Pd 5 alloys have transformation strain of up to 4.6% and work output of up to 29 J cm −3 . •The alloy showed good superelastic behavior at 90 °C with recoverable strain of 4.3%. •The alloy exhibited 1.6% two-way shape memory strain after a simple training procedure. •The formation of 〈0 1 1〉 type II twins in martensite plates results in large transformation strain. -- Abstract: The load-biased shape memory and superelastic responses of a Ni 45.3 Ti 39.7 Hf 10 Pd 5 polycrystalline alloy were investigated in compression. Transformation strain of up to 4.6% and work output of up to 29 J cm −3 were determined from load-biased thermal cycling experiments. The alloy showed good superelastic behavior at 90 o C with recoverable strain of over 4%. It was also determined that the Ni 45.3 Ti 39.7 Hf 10 Pd 5 alloy could develop two-way shape memory strain of 1.6% without an intense training process. Transmission electron microscopy (TEM) revealed that the internal twins formed in the martensite variants were 〈0 1 1〉 type II twins

Preparation and evaluation of ageing effect of Cu-Al-Be-Mn shape memory alloys

Science.gov (United States)

Shivasiddaramaiah, A. G.; Mallik, U. S.; Mahato, Ranjit; Shashishekar, C.

2018-04-01

10-14 wt. % of aluminum, 0.3-0.6 wt. % of beryllium and 0.1-0.4 wt. % of manganese and remaining copper melted in the induction furnace through ingot metallurgy. The prepared SMAs are subjected to homogenization. It was observed that the samples exhibits β-phase at high temperature and shape memory effect after going through step quenching to a low temperature. Scanning Electron Microscope, DSC, bending test were performed on the samples to determine the microstructure, transformation temperatures and shape memory effect respectively. The alloy exhibit good shape memory effect, up to around 96% strain recovery by shape memory effect. The ageing is performed on the specimen prepared according to ASTM standard for testing micro-hardness and tensile test. Precipitation hardening method was employed to age the samples and they were aged at different temperature and at different times followed by quenching. Various forms of precipitates were formed. It was found that the formation rate and transformation temperature increased with ageing time, while the amount of precipitate had an inverse impact on strain recovery by shape memory effect. The result expected is to increase in mechanical properties of the material such as hardness.

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)

Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Evirgen, A. [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Karaman, I., E-mail: ikaraman@tamu.edu [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Pons, J.; Santamarta, R. [Departament de Fisica, Universitat de les Illes Balears, E07122 Palma de Mallorca (Spain); Noebe, R.D. [Materials and Structures Division, NASA Glenn Research Center, Cleveland, OH 44135 (United States)

2016-02-08

The microstructure and shape memory characteristics of the Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure–property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformation–precipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} alloy.

Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni_5_0_._3Ti_3_4_._7Zr_1_5 shape memory alloy

International Nuclear Information System (INIS)

Evirgen, A.; Karaman, I.; Pons, J.; Santamarta, R.; Noebe, R.D.

2016-01-01

The microstructure and shape memory characteristics of the Ni_5_0_._3Ti_3_4_._7Zr_1_5 shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure–property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformation–precipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni_5_0_._3Ti_3_4_._7Zr_1_5 alloy.

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

Influence of atomic ordering on elastocaloric and magnetocaloric effects of a Ni–Cu–Mn–Ga ferromagnetic shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Huang, Chonghui [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Yu, E-mail: yuwang@mail.xjtu.edu.cn [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Tang, Zhao; Liao, Xiaoqi; Yang, Sen; Song, Xiaoping [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)

2015-05-05

Highlights: • Ni{sub 51}Cu{sub 4}Mn{sub 20}Ga{sub 25} alloy exhibits normal elastocaloric and magnetocaloric effects. • L2{sub 1} atomic order of the alloy is increased after annealing at 773 K for 10 h. • Increasing L2{sub 1} atomic order improves its elastocaloric and magnetocaloric effects. • Atomic ordering modifies the magnetic and martensitic transitions of the system. - Abstract: The coexisting elastocaloric and magnetocaloric effects in ferromagnetic shape memory alloys have attracted much attention for the potential application in solid state refrigeration. Previous studies show that the L2{sub 1} atomic ordering of Heusler ferromagnetic shape memory alloys plays important role on their magnetocaloric effect. However, no research work investigates the effect of atomic ordering on their elastocaloric effect yet. In this study, we investigated the influence of atomic ordering on the elastocaloric and magnetocaloric effects of a Ni{sub 51}Cu{sub 4}Mn{sub 20}Ga{sub 25} ferromagnetic shape memory alloy. The alloy exhibits normal elastocaloric effect and normal magnetocaloric effect near room temperature. Moreover, we found that the enhancement of atomic order in this alloy can greatly increase the entropy change and refrigeration capacity of its elastocaloric and magnetocaloric effects. This is attributed to that the atomic ordering modifies the magnetic and martensitic transitions of the system.

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.

Mechanical properties and related substructure of TiNi shape memory alloys

International Nuclear Information System (INIS)

Filip, P.; Kneissl, A.C.

1995-01-01

The mechanical properties of binary near equiatomic TiNi shape memory alloys were investigated after different types of mechanical and heat treatments. The changes of deformation behaviour are explained on the basis of substructure differences after work hardening. The ''elastic moduli'' of both the high-temperature phase B2 and the martensite B19' as well as the ''easy stage of deformation'' are dependent on the work hardening intensity and these changes are related to the mobility of B2/B19' interfaces. The martensite changes its morphology after work hardening. In contrast to a twinned martensite, typical for annealed alloys, the internally slipped martensite was detected after work hardening. (orig.)

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.).

Biocompatibility and corrosion behavior of the shape memory NiTi alloy in the physiological environments simulated with body fluids for medical applications

International Nuclear Information System (INIS)

Khalil-Allafi, Jafar; Amin-Ahmadi, Behnam; Zare, Mehrnoush

2010-01-01

Due to unique properties of NiTi shape memory alloys such as high corrosion resistance, biocompatibility, super elasticity and shape memory behavior, NiTi shape memory alloys are suitable materials for medical applications. Although TiO 2 passive layer in these alloys can prevent releasing of nickel to the environment, high nickel content and stability of passive layer in these alloys are very debatable subjects. In this study a NiTi shape memory alloy with nominal composition of 50.7 atom% Ni was investigated by corrosion tests. Electrochemical tests were performed in two physiological environments of Ringer solution and NaCl 0.9% solution. Results indicate that the breakdown potential of the NiTi alloy in NaCl 0.9% solution is higher than that in Ringer solution. The results of Scanning Electron Microscope (SEM) reveal that low pitting corrosion occurred in Ringer solution compared with NaCl solution at potentiostatic tests. The pH value of the solutions increases after the electrochemical tests. The existence of hydride products in the X-ray diffraction analysis confirms the decrease of the concentration of hydrogen ion in solutions. Topographical evaluations show that corrosion products are nearly same in all samples. The biocompatibility tests were performed by reaction of mouse fibroblast cells (L929). The growth and development of cells for different times were measured by numbering the cells or statistics investigations. The figures of cells for different times showed natural growth of cells. The different of the cell numbers between the test specimen and control specimen was negligible; therefore it may be concluded that the NiTi shape memory alloy is not toxic in the physiological environments simulated with body fluids.

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.

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.

The Effect of Heat Treatment on the Thermo-Elastic Behavior of Ti Ni Shape Memory Alloy

International Nuclear Information System (INIS)

Ahmed, K.

2008-01-01

The Ti-Ni shape memory alloys are used in industrial, medical and biological applications because of their outstanding mechanical properties . Research work has been done to design a remote handling unit using such alloy to work in a high neutron irradiated areas .The pre-alloyed powder is supplied by Memory-Metalle GmbH with composition Ti-49.5 at % Ni. The Metal Injection Molding (MIM) technique has been used to fabricate the alloy and subsequent different heat treatments, spectroscopic and thermal analysis have been done to test the alloy performance. Regarding to this pre-alloyed powder composition, the thermo-elastic behavior is perfect. Transformation temperature in the range 27 degree C - 63 degree C has been achieved .The final sintering quality is not satisfactory. The results show that the proposed heat treatments are not able to release the generated internal stress

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.

Microstructural evolution and magnetic properties of binder jet additive manufactured Ni-Mn-Ga magnetic shape memory alloy foam

International Nuclear Information System (INIS)

Mostafaei, Amir; Kimes, Katerina A.; Stevens, Erica L.; Toman, Jakub; Krimer, Yuval L.; Ullakko, Kari; Chmielus, Markus

2017-01-01

This study investigated microstructural evolution, phase transformation and magnetic behavior of additively manufactured magnetic shape memory alloy foam. Pre-alloyed angular Ni-Mn-Ga ball-milled powder was binder jet printed and sintered at 1020 °C for 4 h in both vacuum and argon atmospheres. Porosity of the manufactured foams was studied using micro-computed x-ray tomography and it was found that the relative density of the sintered parts was about 50–60%. In the printed sample that was sintered in argon, electron microscopy with elemental analysis showed no compositional gradient. X-ray diffraction indicated that 10M modulated martensite was present in the pre-alloyed powder as well as the sample sintered in argon. Differential scanning calorimetry and thermomagnetic results showed that martensitic transformation of the sample sintered in argon was at 34 °C, while barely detectable in the sample sintered in vacuum. Saturation magnetization of the printed sample sintered in argon atmosphere was around 68.4 Am"2/kg. Production of a magnetic shape memory alloy by printing would enable complex-shaped elements for demanding applications, and intentionally including porosity could allow these polycrystals to exhibit the magnetic shape memory effect. Therefore, a facile method for sintering of Ni–Mn–Ga printed parts has been presented for the first time.

High Work Output Ni-Ti-Pt High Temperature Shape Memory Alloys and Associated Processing Methods

Science.gov (United States)

Noebe, Ronald D. (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Garg, Anita (Inventor)

2009-01-01

According to the invention, compositions of Ni-Ti-Pt high temperature, high force, shape memory alloys are disclosed that have transition temperatures above 100 C.; have narrow hysteresis; and produce a high specific work output.

Nanoparticles from Cu-Zn-Al shape memory alloys physically synthesized by ion milling deposition

Energy Technology Data Exchange (ETDEWEB)

Pavon, Luis Alberto Lopez [Universidad Autonoma de Nuevo Leon (UANL), Nuevo Leon (Mexico); Cuellara, Enrique Lopez; Castro, Alejandro Torres; Cruza, Azael Martinez de la [Universidad Autonoma de Nuevo Leon (CIIDIT/UANL), Nuevo Leon (Mexico). Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia; Ballesteros, Carmen [Universidad Carlos III de Madrid, Madrid (Spain). Departamento de Fisica; Araujo, Carlos Jose de [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Departamento de Engenharia Mecanica

2012-05-15

In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al alloys with shape memory effect. Two different compositions were used, target A: 75.22Cu-17.12Zn-7.66Al at % with an Ms of -9 deg C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 degree C. Nanoparticles were characterized by High Resolution Transmission Electron Microscopy, Electron Diffraction and Energy Dispersive X-ray Spectroscopy. The obtained nanoparticles showed a small dispersion, with a size range of 3.2-3.5 nm. Their crystal structure is in good agreement with the bulk martensitic structure of the targets. In this sense, results on morphology, composition and crystal structure have indicated that it is possible to produce nanoparticles of CuZnAl shape memory alloys with martensitic structure in a single process using Ion Milling. (author)

Nanoparticles from Cu-Zn-Al shape memory alloys physically synthesized by ion milling deposition

International Nuclear Information System (INIS)

Pavon, Luis Alberto Lopez; Cuellara, Enrique Lopez; Castro, Alejandro Torres; Cruza, Azael Martinez de la; Ballesteros, Carmen; Araujo, Carlos Jose de

2012-01-01

In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al alloys with shape memory effect. Two different compositions were used, target A: 75.22Cu-17.12Zn-7.66Al at % with an Ms of -9 deg C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 degree C. Nanoparticles were characterized by High Resolution Transmission Electron Microscopy, Electron Diffraction and Energy Dispersive X-ray Spectroscopy. The obtained nanoparticles showed a small dispersion, with a size range of 3.2-3.5 nm. Their crystal structure is in good agreement with the bulk martensitic structure of the targets. In this sense, results on morphology, composition and crystal structure have indicated that it is possible to produce nanoparticles of CuZnAl shape memory alloys with martensitic structure in a single process using Ion Milling. (author)

Effect of Si on the reversibility of stress-induced martensite in Fe-Mn-Si shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Stanford, N. [Centre for Material and Fibre Innovation, Deakin University, Geelong, Victoria 3217 (Australia); Dunne, D.P., E-mail: druce_dunne@uow.edu.au [Faculty of Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia)

2010-12-15

Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a-vis shape memory. This paper examines the effect of Si on the morphology and the crystallography of the martensite in the Fe-Mn-Si system. It is concluded that the addition of Si increases the c/a ratio of the martensite, reduces the transformation volume change and decreases the atomic spacing difference between the parallel close-packed directions in the austenite-martensite interface (habit) plane. It is proposed that, in addition to austenite strengthening, Si enhances reversibility by reducing the volume change and the interfacial atomic mismatch between the martensite and the austenite. Although shape memory is improved, transformation reversibility remains limited by the necessary misfit dislocations that accommodate the atomic spacing differences in the interface.

Effect of Si on the reversibility of stress-induced martensite in Fe-Mn-Si shape memory alloys

International Nuclear Information System (INIS)

Stanford, N.; Dunne, D.P.

2010-01-01

Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a-vis shape memory. This paper examines the effect of Si on the morphology and the crystallography of the martensite in the Fe-Mn-Si system. It is concluded that the addition of Si increases the c/a ratio of the martensite, reduces the transformation volume change and decreases the atomic spacing difference between the parallel close-packed directions in the austenite-martensite interface (habit) plane. It is proposed that, in addition to austenite strengthening, Si enhances reversibility by reducing the volume change and the interfacial atomic mismatch between the martensite and the austenite. Although shape memory is improved, transformation reversibility remains limited by the necessary misfit dislocations that accommodate the atomic spacing differences in the interface.

Designing a New Ni-Mn-Sn Ferromagnetic Shape Memory Alloy with Excellent Performance by Cu Addition

Directory of Open Access Journals (Sweden)

Kun Zhang

2018-02-01

Full Text Available Both magnetic-field-induced reverse martensitic transformation (MFIRMT and a high working temperature are crucial for the application of Ni-Mn-Sn magnetic shape memory alloys. Here, by first-principles calculations, we demonstrate that the substitution of Cu for Sn is effective not only in enhancing the MFIRMT but also in increasing martensitic transformation, which is advantageous for its application. Large magnetization difference (ΔM in Ni-Mn-Sn alloy is achieved by Cu doping, which arises from the enhancement of magnetization of austenite due to the change of Mn-Mn interaction from anti-ferromagnetism to ferromagnetism. This directly leads to the enhancement of MFIRMT. Meanwhile, the martensitic transformation shifts to higher temperature, owing to the energy difference between the austenite L21 structure and the tetragonal martensite L10 structure increases by Cu doping. The results provide the theoretical data and the direction for developing a high temperature magnetic-field-induced shape memory alloy with large ΔM in the Ni-Mn-Sn Heusler alloy system.

Shape Memory Characteristics of Ti(sub 49.5)Ni(sub 25)Pd(sub 25)Sc(sub 0.5) High-Temperature Shape Memory Alloy After Severe Plastic Deformation

Science.gov (United States)

Atli, K. C.; Karaman, I.; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

2011-01-01

A Ti(49.5)Ni25Pd25Sc(0.5) high-temperature shape memory alloy is thermomechanically processed to obtain enhanced shape-memory characteristics: in particular, dimensional stability upon repeated thermal cycles under constant loads. This is accomplished using severe plastic deformation via equal channel angular extrusion (ECAE) and post-processing annealing heat treatments. The results of the thermomechanical experiments reveal that the processed materials display enhanced shape memory response, exhibiting higher recoverable transformation and reduced irrecoverable strain levels upon thermal cycling compared with the unprocessed material. This improvement is attributed to the increased strength and resistance of the material against defect generation upon phase transformation as a result of the microstructural refinement due to the ECAE process, as supported by the electron microscopy observations.

Laser Welding of Shape Memory Alloys

Science.gov (United States)

Oliveira, Joao Pedro de Sousa

Joining of shape memory alloys is of great importance for both functional and structural applications as it can provide an increased design flexibility. In this work similar NiTi/NiTi, CuAlMn/CuAlMn and dissimilar NiTi/Ti6Al4V joints were produced by Nd:YAG laser. For the NiTi/NiTi joints the effect of process parameters (namely the heat input) on the superelastic and shape memory effects of the joints was assessed and correlated to its microstructure. Microstructural analysis was performed by means of X-ray diffraction using synchrotron radiation, which allowed for fine probing of the welded material. It was noticed the presence of martensite in the thermally affected regions, while the base material remained fully austenitic. The mechanisms for the formation of martensite, at room temperature, due to the welding procedure are presented and the influence of this phase on the functional properties of the joints is discussed. Additionally, the residual stresses were determined using synchrotron X-ray diffraction. For the dissimilar NiTi/Ti6Al4V joints, a Niobium interlayer was used to prevent the formation undesired brittle intermetallic compounds. Additionally, it was observed that positioning of the laser beam was of significant importance to obtain a sound joint. The mechanisms responsible for the joint formation are discussed based on observations with advanced characterization techniques, such as transmission electron microscopy. At the NiTi/Nb interface, an eutectic reaction promotes joining of the two materials, while at the Ti6Al4V/Nb interface fusion and, subsequent solidification of the Ti6Al4V was responsible for joining. Short distance diffusion of Nb to the fusion zone of Ti6Al4V was observed. Although fracture of the dissimilar welded joints occurred at a stress lower than the minimum required for the stress induced transformation, an improvement on the microstructure and mechanical properties, relatively to existing literature, was obtained. Finally

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.

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.)

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.

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...

''Some features of γ-ε martensitic transformation and shape memory effect in Fe-Mn-Si based alloys''

International Nuclear Information System (INIS)

Gulyaev, A.A.

1995-01-01

In the present paper several important aspects concerning the shape memory behavior of the ε-martensite in the cost-saving Fe-Mn-Si-based alloys and its application are reported. Some kinetic features of the γ-ε martensitic transformation are discussed. The effects of the composition, volume change induced by the transformation, strength of austenite, temperature of pre strain on the shape memory effect have been investigated. (orig.)

The effect of hafnium content on the transformation temperatures of Ni49Ti51-xHfx shape memory alloys

International Nuclear Information System (INIS)

Angst, D.R.; Thoma, P.E.; Kao, M.Y.

1995-01-01

Ternary alloys of NiTiHf, having higher transformation temperatures than binary NiTi shape memory alloys, have been produced and analyzed. Beginning with a base composition of Ni 49 Ti 51 , Hf was substituted for Ti up to 30 atomic percent. Differential scanning calorimetry was used to determine the transformation temperatures of the as-cast alloys. The peak martensite temperature of the Ni 49 Ti 51 alloy was 69 C and increased to 525 C for the Ni 49 Ti 21 Hf 30 alloy. The peak austenite temperature of the Ni 49 Ti 51 alloy was 114 C and increased to 622 C for the Ni 49 Ti 21 Hf 30 alloy. An apparent minimum in the peak transformation temperatures occurred between 0 and 3 atomic percent Hf. Preliminary experiments were also conducted to determine the effect of thermomechanical processing on the shape memory properties of the Ni 49 Ti 41 Hf 10 . Data are presented on the effect of cold work and heat treatment on the transformation temperatures of this alloy. (orig.)

Electron energy-loss spectroscopy study of NiTi shape memory alloys

International Nuclear Information System (INIS)

Yang, Z.Q.; Schryvers, D.

2008-01-01

Electron energy loss spectroscopy (EELS) investigations were carried out on NiTi shape memory alloys. The composition of lens-shaped precipitates is determined to be Ni 4 Ti 3 by model-based EELS quantification, and the Ni-depleted zone in the B2 matrix surrounding the Ni 4 Ti 3 precipitates was quantified. The Young's modulus Y m of the B2 matrix with 51 at.% Ni and the Ni 4 Ti 3 precipitates was evaluated to be about 124 and 175 GPa, respectively. The intensity of the Ni L 3 edge for the precipitate is slightly higher than that for the B2 phase

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.

Internal stresses in steel plate generated by shape memory alloy inserts

Czech Academy of Sciences Publication Activity Database

Malard, B.; Pilch, Jan; Šittner, Petr; Davydov, V.; Sedlák, Petr; Konstantinidis, K.; Hughes, D. J.

2012-01-01

Roč. 60, č. 3 (2012), s. 1378-1394 ISSN 1359-6454 R&D Projects: GA ČR GAP108/10/1296 Grant - others:SMARTNETS(XE) FP7-NMP2-2011-262806 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20760514 Keywords : shape memory alloy * NiTi * residual stress * neutron diffraction * strain scanning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.941, year: 2012 http://www.sciencedirect.com/science/article/pii/S1359645411007294

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.

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

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.

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.

The effect of pre-rolling Fe-Mn-Si-based shape memory alloys: Mechanical properties and transmission electron microcopy examination

International Nuclear Information System (INIS)

Baruj, A.; Troiani, H.E.

2008-01-01

Fe-Mn-Si-based alloys have been promising systems for shape memory applications for a long time. However, the need of a complicated training process in order to get the desired properties avoided their practical use. Recently, several new Fe-Mn-Si-based alloys, with interesting properties, containing different types of precipitates have been developed. In these new systems, the shape memory improvement is obtained either by the sole introduction of precipitates, or by the combination of a simple thermomechanical treatment followed by a subsequent precipitation. In this work, we investigate the effect of a thermomechanical treatment performed at a temperature of 870 K on the shape memory properties of an Fe-28Mn-6Si-5Cr (wt.%). We have found that a simple treatment, without the necessity of introducing precipitates, is enough to obtain good shape memory properties. Transmission electron microscopy shows that a large density of stacking faults is produced during the treatment. From these observations we deduce that this large stacking fault density is clearly related to the observed properties

Precipitation Strengthenable NiTiPd High Temperature Shape Memory Alloys

Science.gov (United States)

Bigelow, Glen; Garg, Anita; Benafan, Othmane; Noebe, Ronald; Gaydosh, Darrell; Padula, Santo, II

2017-01-01

In binary NiTi alloys, it has long been known that Ni-rich alloys can be heat treated to produce precipitates which both strengthen the matrix against dislocations and improve the behavior of the material under thermal and mechanical cycling. Within recent years, the same effect has been observed in Ni-rich NiTiHf high temperature shape memory alloys and heat treatment regimens have been defined which will reliably produce improved properties. In NiTiPd alloys, precipitation has also been observed, but studies are still underway to define reliable heat treatments and compositions which will provide a balance of strengthening and good thermomechanical properties. For this study, a series of NiTi-32 at.Pd alloys was produced to determine the effect of changing nickeltitanium content on the transformation behavior and heat treatability of the material. Samples were aged at temperatures between 350C and 450C for times up to 100 hours. Actuation type behavior was evaluated using uniaxial constant force thermal cycling (UCFTC) to determine the effect of composition and aging on the material behavior. TEMSEM was used to evaluate the microstructure and determine the types of precipitates formed. The correlation between composition, heat treat, microstructure, and thermomechanical behavior will be addressed and discussed.

Fabrication of SLM NiTi Shape Memory Alloy via Repetitive Laser Scanning

Science.gov (United States)

Khoo, Zhong Xun; Liu, Yong; Low, Zhi Hong; An, Jia; Chua, Chee Kai; Leong, Kah Fai

2018-01-01

Additive manufacturing has the potential to overcome the poor machinability of NiTi shape-memory alloy in fabricating smart structures of complex geometry. In recent years, a number of research activities on selective laser melting (SLM) of NiTi have been carried out to explore the optimal parameters for producing SLM NiTi with the desired phase transformation characteristics and shape-memory properties. Different effects of energy density and processing parameters on the properties of SLM NiTi were reported. In this research, a new approach—repetitive laser scanning—is introduced to meet these objectives as well. The results suggested that the laser absorptivity and heat conductivity of materials before and after the first scan significantly influence the final properties of SLM NiTi. With carefully controlled repetitive scanning process, the fabricated samples have demonstrated shape-memory effect of as high as 5.11% (with an average value of 4.61%) and exhibited comparable transformation characteristics as the NiTi powder used. These results suggest the potential for fabricating complex NiTi structures with similar properties to that of the conventionally produced NiTi parts.

Fabrication of SLM NiTi Shape Memory Alloy via Repetitive Laser Scanning

Science.gov (United States)

Khoo, Zhong Xun; Liu, Yong; Low, Zhi Hong; An, Jia; Chua, Chee Kai; Leong, Kah Fai

2018-03-01

Additive manufacturing has the potential to overcome the poor machinability of NiTi shape-memory alloy in fabricating smart structures of complex geometry. In recent years, a number of research activities on selective laser melting (SLM) of NiTi have been carried out to explore the optimal parameters for producing SLM NiTi with the desired phase transformation characteristics and shape-memory properties. Different effects of energy density and processing parameters on the properties of SLM NiTi were reported. In this research, a new approach—repetitive laser scanning—is introduced to meet these objectives as well. The results suggested that the laser absorptivity and heat conductivity of materials before and after the first scan significantly influence the final properties of SLM NiTi. With carefully controlled repetitive scanning process, the fabricated samples have demonstrated shape-memory effect of as high as 5.11% (with an average value of 4.61%) and exhibited comparable transformation characteristics as the NiTi powder used. These results suggest the potential for fabricating complex NiTi structures with similar properties to that of the conventionally produced NiTi parts.

Shape Memory Effect Actuators from Chlorides, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Shape Change Technologies is developing a radical new technique for the fabrication of Shape Memory alloys, such as TiNi and its ternary alloys of Hf, Zr, and Cu....

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

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

Atomic force microscopy study of stacking modes of martensitic transformation in Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Liu, D.Z.; Kikuchi, T.; Kajiwara, S.; Shinya, N.

2000-01-01

Stacking modes of thermally induced and stress-induced martensitic transformation in Fe-28Mn-6Si-5Cr shape memory alloys have been studied using atomic force microscopy (AFM). It has been found that thermally induced martensite plates appear with the self-accommodated stacking form, in which all the three possible variants with different left angle 112 right angle shear directions in a {111} plane are activated and formed in parallel but at separate places; i.e. each plate corresponds to one variant. In addition, a plastic deformation band is always induced in austenite between two different variants. On the other hand, stress-induced martensite plates appear with the mono-partial stacking form, i.e. only single variant is activated in a {111} plane in a grain. The difference between stacking modes of thermally induced and stress-induced martensites makes them play a different role in contributing to shape memory effect in Fe-Mn-Si based shape memory alloys. (orig.)

GRAIN-REFINEMENT AND THE RELATED PHENOMENA IN QUATERNARY Cu-Al-Ni-Ti SHAPE MEMORY ALLOYS

OpenAIRE

Sugimoto , K.; Kamei , K.; Matsumoto , H.; Komatsu , S.; Akamatsu , K.; Sugimoto , T.

1982-01-01

It was reported that the addition of a small amount of titanium (0.5 - 3.99%) to a Cu-13.93%Al-3.36%Ni ternary alloy resulted in a remarkable grain-refining. The original grain-size of about 750 microns under hot-rolled and quenched conditions of the ternary alloy was reduced to that of the order of about 100 microns by addition of tiatanium. It was suggested that several technical improvements of the mechanical properties of Cu-Al-Ni shape memory alloys, such as better formability, less crac...

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.)

A Two-Way Shape Memory Study on Ni-Rich NiTi Shape Memory Alloy by Combination of the All-Round Treatment and the R-Phase Transformation

Science.gov (United States)

Wu, Z. H.; Vokoun, D.; Leu, C. C.; Hu, C. T.

2017-12-01

Ni4Ti3 precipitates are formed in Ni-rich NiTi shape memory alloys (SMAs) after a certain heat treatment. Such a treatment then results in the changed phase transformation behavior of the alloy switching from the one-step reversible phase change B2 ↔ B19' to the two-step, B2 ↔ R ↔ B19', phase change. The present study reports a two-way shape memory (TWSM) due to an all-round treatment followed by an R-phase constraint aging at room temperature. The enhanced TWSM behavior was observed upon temperature cycling between 273 K (R-phase) and 77 K (B19' phase). The effect of various constraint strains in R-phase aging by employing different diameters of the constraint ring was studied. However, the TWSM effect due to constraining the R-phase will be eliminated after a temperature rise of specimen to the fully parent phase (373 K).

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

Tribological performance of near equiatomic and Ti-rich NiTi shape memory alloy thin films

International Nuclear Information System (INIS)

Tillmann, Wolfgang; Momeni, Soroush

2015-01-01

Near equiatomic and Ti-rich NiTi shape memory alloy thin films were magnetron sputtered with the same processing parameters and thickness of 3 μm. The microstructure, composition, shape memory behavior, mechanical and tribological properties of the deposited thin films were analyzed by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), nanoindentation, ball-on-disc, scratch test, and three dimensional (3D) optical microscopy. The obtained results clearly show how the crystallization evolution and precipitation formation of these two sets of thin films can drastically influence their mechanical and tribological performances

Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

International Nuclear Information System (INIS)

L’vov, Victor A; Kosogor, Anna; Barandiaran, Jose M; Chernenko, Volodymyr A

2015-01-01

An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect. (paper)

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.

Mechanical and functional properties of two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy with the addition of Dy

International Nuclear Information System (INIS)

Yang, S Y; Wang, C P; Liu, X J

2013-01-01

The effects of Dy addition on microstructure, martensitic transformation, mechanical and shape memory properties of the two-phase Ni 53 Mn 22 Co 6 Ga 19 high-temperature shape memory alloy were investigated. It is found that a small Dy addition results in the refinement of grain size, which can effectively improve the tensile ductility and strength of the two-phase Ni 53 Mn 22 Co 6 Ga 19 alloy. However, a Dy(Ni,Mn) 4 Ga precipitate forms in the alloys with the Dy addition, and its amount increases with an increase in the Dy addition. This change causes the ductility of the alloys to decrease when the Dy addition is further increased to 0.3 at.%. The results further show that the changes in the martensitic transformation temperature of the studied alloys can be attributed to the combined effects of the tetragonality (c/a) and electron concentration (e/a) of martensite. Additionally, the shape memory effects of the alloys are closely related to the refinement of grain size and the alloy strength. In this study, the (Ni 53 Mn 22 Co 6 Ga 19 ) 99.8 Dy 0.2 alloy exhibits a variety of good properties, including a high martensitic transformation starting temperature of 385.7 °C, a tensile ductility of 10.3% and a shape memory effect of 2.8%. (paper)

Characterization of the laser gas nitrided surface of NiTi shape memory alloy

International Nuclear Information System (INIS)

Cui, Z.D.; Man, H.C.; Yang, X.J.

2003-01-01

Owing to its unique properties such as shape memory effects, superelasticity and radiopacity, NiTi alloy is a valuable biomaterial for fabricating implants. The major concern of this alloy for biological applications is the high atomic percentage of nickel in the alloy and the deleterious effects to the body by the corrosion and/or wears products. In this study, a continuous wave Nd-YAG laser was used to conduct laser gas nitriding on the substrate of NiTi alloy. The results show that a continuous and crack-free thin TiN layer was produced in situ on the NiTi substrate. The characteristics of the nitrided surface layer were investigated using SEM, XRD, XPS and AAS. No nickel signal was detected on the top surface of the laser gas nitrided layer. As compared with the mechanical polished NiTi alloy, the nickel ion release rate out of the nitrided NiTi alloy decreased significantly in Hanks' solution at 37 deg. C, especially the initial release rate

Evaluation of mechanical alloying to obtain Cu-Al-Nb shape memory alloy

Directory of Open Access Journals (Sweden)

Maria do Carmo Amorim da Silva

2005-06-01

Full Text Available The technical viability of preparing a Cu-Al-Nb shape memory alloy by high energy ball milling in a planetary mill has been evaluated. The alloy Cu-13Al-2Nb (wt. (% was prepared by mixing pure elemental powders. A ball-to-powder weight ratio of 6:1 and rotation rate of 150 rpm in argon atmosphere were the main processing parameters. The milling time ranged from 1 to 65 hours. Changes in microstructure as a function of milling time were investigated, using X-ray diffraction analysis and scanning electron microscopy. To investigate the viability of producing sintered parts from milled powders, the conventional powder metallurgy route was used. The milled powders were compacted in a cylindrical die at 900 MPa. Sintering was carried out in argon atmosphere at 850 °C for 6 hours. This study has shown that high energy ball milling, combined with pressing and sintering, can be used to promote the formation of a copper-aluminum solid solution and achieve final sintered densities of 91% of the theoretical density.

Influence of alloying elements on the corrosion properties of shape memory stainless steels

International Nuclear Information System (INIS)

Della Rovere, C.A.; Alano, J.H.; Silva, R.; Nascente, P.A.P.; Otubo, J.; Kuri, S.E.

2012-01-01

Highlights: ► The corrosion properties of three Fe–Mn–Si–Cr–Ni–(Co) shape-memory stainless steels (SMSSs) were compared with those of a type 304 (SS 304) austenitic stainless steel. ► A considerably high Si content (about 40 at%) is present in the anodic passive films formed on SMSSs in 0.5 M H 2 SO 4 solution. ► The high protectiveness of the anodic passive film formed on SMSSs in 0.5 M H 2 SO 4 solution results from a protective film consisting of a (Fe, Cr)–mixed silicate. ► The SMSSs exhibited higher corrosion resistance than SS 304 in highly oxidizing environments. ► The SMSSs showed poor corrosion resistance in 3.5% NaCl solution compared to that of SS 304. - Abstract: The corrosion properties of three Fe–Mn–Si–Cr–Ni–(Co) shape memory stainless steels were studied based on X-ray photoelectron spectroscopy (XPS) analyses, immersion and polarization tests. The test results were compared with those of a type 304 austenitic stainless steel. The XPS analyses indicated substantial Si content in the anodic passive films formed on shape memory stainless steels in sulfuric acid solution and that the high protectiveness of these films results from a protective film consisting of a (iron, chromium)–mixed silicate. The corrosion rate of the shape memory stainless steels in boiling nitric acid solution was lower than that of austenitic stainless steel. The high silicon content was found to play an important role in the corrosion behavior of these shape memory alloys in highly oxidizing environments. Due to their high manganese content, the shape memory stainless steels showed poor corrosion behavior in 3.5% sodium chloride solution when compared with austenitic stainless steel.

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.

Application of Taguchi method to optimization of surface roughness during precise turning of NiTi shape memory alloy

Science.gov (United States)

Kowalczyk, M.

2017-08-01

This paper describes the research results of surface quality research after the NiTi shape memory alloy (Nitinol) precise turning by the tools with edges made of polycrystalline diamonds (PCD). Nitinol, a nearly equiatomic nickel-titanium shape memory alloy, has wide applications in the arms industry, military, medicine and aerospace industry, and industrial robots. Due to their specific properties NiTi alloys are known to be difficult-to-machine materials particularly by using conventional techniques. The research trials were conducted for three independent parameters (vc, f, ap) affecting the surface roughness were analyzed. The choice of parameter configurations were performed by factorial design methods using orthogonal plan type L9, with three control factors, changing on three levels, developed by G. Taguchi. S/N ratio and ANOVA analyses were performed to identify the best of cutting parameters influencing surface roughness.

Shape memory alloy resetable spring lift for pedestrian protection

Science.gov (United States)

Barnes, Brian M.; Brei, Diann E.; Luntz, Jonathan E.; Strom, Kenneth; Browne, Alan L.; Johnson, Nancy

2008-03-01

Pedestrian protection has become an increasingly important aspect of automotive safety with new regulations taking effect around the world. Because it is increasingly difficult to meet these new regulations with traditional passive approaches, active lifts are being explored that increase the "crush zone" between the hood and rigid under-hood components as a means of mitigating the consequences of an impact with a non-occupant. Active lifts, however, are technically challenging because of the simultaneously high forces, stroke and quick timing resulting in most of the current devices being single use. This paper introduces the SMArt (Shape Memory Alloy ReseTable) Spring Lift, an automatically resetable and fully reusable device, which couples conventional standard compression springs to store the energy required for a hood lift, with Shape Memory Alloys actuators to achieve both an ultra high speed release of the spring and automatic reset of the system for multiple uses. Each of the four SMArt Device subsystems, lift, release, lower and reset/dissipate, are individually described. Two identical complete prototypes were fabricated and mounted at the rear corners of the hood, incorporated within a full-scale vehicle testbed at the SMARTT (Smart Material Advanced Research and Technology Transfer) lab at University of Michigan. Full operational cycle testing of a stationary vehicle in a laboratory setting confirms the ultrafast latch release, controlled lift profile, gravity lower to reposition the hood, and spring recompression via the ratchet engine successfully rearming the device for repeat cycles. While this is only a laboratory demonstration and extensive testing and development would be required for transition to a fielded product, this study does indicate that the SMArt Lift has promise as an alternative approach to pedestrian protection.

Implement of Shape Memory Alloy Actuators in a Robotic Hand

Directory of Open Access Journals (Sweden)

Daniel Amariei

2006-10-01

Full Text Available This paper was conceived to present the ideology of utilizing advanced actuators to design and develop innovative, lightweight, powerful, compact, and as much as possible dexterous robotic hands. The key to satisfying these objectives is the use of Shape Memory Alloys (SMAs to power the joints of the robotic hand. The mechanical design of a dexterous robotic hand, which utilizes non-classical types of actuation and information obtained from the study of biological systems, is presented in this paper. The type of robotic hand described in this paper will be utilized for applications requiring low weight, power, compactness, and dexterity.

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

Science.gov (United States)

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.

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.

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Science.gov (United States)

Bigelow, Glen S.; Padula, Santo A.; Noebe, Ronald D.; Garg, Anita; Gaydosh, Darrell

2010-01-01

While NiTiPd alloys have been extensively studied for proposed use in high-temperature shape-memory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd)49.5Ti50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

Scale up of NiTi shape memory alloy production by EBM

Science.gov (United States)

Otubo, J.; Rigo, O. D.; Moura Neto, C.; Kaufman, M. J.; Mei, P. R.

2003-10-01

The usual process to produce NiTi shape memory alloy is by vacuum induction melting (VIM) using a graphite crucible, which causes contamination of the melt with carbon. Contamination with oxygen originates from the residual oxygen inside the melting chamber. An alternative process to produce NiTi alloys is by electron beam melting (EBM) using a water-cooled copper crucible that eliminates carbon contamination, and the oxygen contamination would be minimal due to operation in a vacuum of better than 10^{-2} Pa. In a previous work, it was demonstrated that the technique is feasible for button shaped samples weighing around 30g. The present work presents the results on the scale up program that enables the production of larger samples/ingots. The results are very promising in terms of chemical composition homogeneity as well as in terms of carbon contamination, the latter being four to ten times lower than the commercially-produced VIM products, and in terms of final oxygen content which is shown to depend primarily on the starting raw materials.

Size effect and scaling power-law for superelasticity in shape-memory alloys at the nanoscale.

Science.gov (United States)

Gómez-Cortés, Jose F; Nó, Maria L; López-Ferreño, Iñaki; Hernández-Saz, Jesús; Molina, Sergio I; Chuvilin, Andrey; San Juan, Jose M

2017-08-01

Shape-memory alloys capable of a superelastic stress-induced phase transformation and a high displacement actuation have promise for applications in micro-electromechanical systems for wearable healthcare and flexible electronic technologies. However, some of the fundamental aspects of their nanoscale behaviour remain unclear, including the question of whether the critical stress for the stress-induced martensitic transformation exhibits a size effect similar to that observed in confined plasticity. Here we provide evidence of a strong size effect on the critical stress that induces such a transformation with a threefold increase in the trigger stress in pillars milled on [001] L2 1 single crystals from a Cu-Al-Ni shape-memory alloy from 2 μm to 260 nm in diameter. A power-law size dependence of n = -2 is observed for the nanoscale superelasticity. Our observation is supported by the atomic lattice shearing and an elastic model for homogeneous martensite nucleation.

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

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)

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 microscopically motivated constitutive model for shape memory alloys: Formulation, analysis and computations

Czech Academy of Sciences Publication Activity Database

Frost, Miroslav; Benešová, B.; Sedlák, P.

2016-01-01

Roč. 21, č. 3 (2016), s. 358-382 ISSN 1081-2865 R&D Projects: GA ČR GA13-13616S; GA ČR GAP201/10/0357 Institutional support: RVO:61388998 Keywords : shape memory alloys * constitutive model * generalized standard materials * dissipation * energetic solution Subject RIV: BA - General Mathematics Impact factor: 2.953, year: 2016 http://mms.sagepub.com/content/21/3/358

Well-posedness of a thermo-mechanical model for shape memory alloys under tension

Czech Academy of Sciences Publication Activity Database

Krejčí, Pavel; Stefanelli, U.

2010-01-01

Roč. 44, č. 6 (2010), s. 1239-1253 ISSN 0764-583X R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : shape memory alloys * thermo-mechanics * well-posedness * hysteresis operator Subject RIV: BA - General Mathematics Impact factor: 1.202, year: 2010 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8129335

Martensitic transformation and shape memory effect in Ni54.75Mn13.25Fe7Ga25 ferromagnetic shape memory alloy

International Nuclear Information System (INIS)

Wang, H.B.; Sui, J.H.; Liu, C.; Cai, W.

2008-01-01

The martensitic transformation and shape memory effect of Ni 54.75 Mn 13.25 Fe 7 Ga 25 (at.%) alloy are studied in the present paper. It is shown that tetragonal martensite with parallel bands substructure transforms to parent phase heated by electron beam. It can be clearly observed that the martensite band becomes smaller and smaller, then transforms to parent phase completely in the end. A large reversible transformation strain, about 1.5%, is obtained in this undeformed polycrystalline alloy due to martensitic transformation and its reverse transformation. This transformation strain is also increased to 1.8% by the external magnetic field. It is believed that the effect of the magnetic field on the preferential orientation of martensitic variants increases the transformation strain

Laser beam welding of NiTi-shape memory alloys; Laserstrahl-Schweissen von NiTi-Formgedaechtnislegierungen

Energy Technology Data Exchange (ETDEWEB)

Haas, T.

1996-04-01

Using a Nd:YAG laser, the weldability of binary nickel-titanium shape memory alloys containing 50.0 and 48.5 at.-% Ti respectively was investigated. By tensile tests within a temperature range of -80 C to +200 C the mechanical properties of the laser welded joints were examined. Changes in the transformation behaviour were detected by calorimetric measurements (DSC method). The stress-strain behaviour was attributed to the microstructure of the welds, revealed by optical microscopy and transmission electron microscopy (TEM). Using a scanning electron microscope (SEM), the mechanisms of failure were examined. Joints of the martensitic Ti-rich alloy were brittle, showing an ultimate tensile strength of 600 MPa, corresponding to half of the value of the base material. The reduction in strength was explained by the formation of Ti{sub 2}Ni precipitations along grain boundaries in the weld. Since the welds still exhibited twin deformation, pseudoplastic strains of 7% were achieved. Ultimate strength data showed a very low scatter. Therefore it was possible to use the shape memory effect up to a strain of 6% without failure. After a total elongation to 6% strain, the laser welded joints showed a free recovery with an amnesia of 0.3%. The shape memory effect was shown to be retained in the laser welded joints. 154 refs.

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.

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.

Integration of Shape Memory Alloys into Low-Damped Rotor-Bearing Systems

DEFF Research Database (Denmark)

Enemark, Søren

2015-01-01

to use passive adaptive control through smart materials. Shape Memory Alloys (SMAs) are interesting candidates in that relation, because of their highly temperature sensitive stiffness and mechanical hysteresis, which can be used for damping purposes. The thesis focuses on three main aspects related...... and identifiability, and to call attention to the inherent uncertainties of model predictions. The second aspect concerns design and modelling of machine elements made from SMAs. Different actuation principles of SMAs are covered, and pseudoelastic elements in pre-tension are found to have the most promising...

Microstructures and phase transformations of Ti-30Zr-xNb (x = 5, 7, 9, 13 at.%) shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Qu, Wentao; Sun, Xuguang; Yuan, Bifei [School of Mechanical Engineering, Xi' an Shiyou University, Xi' an 710065 (China); Xiong, Chengyang; Zhang, Fei [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Sun, Baohui [Lanzhou Seemine SMA Co. Ltd., Lanzhou 730010 (China)

2016-12-15

The microstructures, phase transformations and shape memory properties of Ti-30Zr-xNb (x = 5, 7, 9, 13 at.%) alloys were investigated. The X-ray diffraction and transmission electron microscopy observations showed that the Ti-30Zr-5Nb, Ti-30Zr-7/9Nb and Ti-30Zr-13Nb alloys were composed of the hcp α′-martensite, orthorhombic α″-martensite and β phases, respectively. The results indicated the enhanced β-stabilizing effect of Nb in Ti-30Zr-xNb alloys than that in Ti-Nb alloys due to the high content of Zr. The differential scanning calorimetry test indicated that the Ti-30Zr-5Nb alloy displayed a reversible transformation with a high martensitic transformation start temperature of 776 K and a reverse martensitic transformation start temperature (A{sub s}) of 790 K. For the Ti-30Zr-7Nb and Ti-30Zr-9Nb alloys, the martensitic transformation temperatures decreased with the increasing Nb content. Moreover, an ω phase transformation occurred in the both alloys upon heating at a temperature lower than the corresponding A{sub s}, which is prompted by more addition of Nb. Although the critical stress in tension of the three martensitic alloys decreased with increasing Nb content, the Ti-30Zr-9Nb alloy showed a critical stress of as high as 300 MPa. Among all the alloys, the Ti-30Zr-9Nb alloy exhibited the maximum shape memory effect of 1.61%, due to the lowest critical stress for the martensite reorientation. - Highlights: •Ti-30Zr-5Nb alloy is composed of hcp α′-martensite with the M{sub s} of 776 K. •Ti-30Zr-7Nb and Ti-30Zr-9Nb alloys are predominated by orthorhombic α″-martensite. •Ti-30Zr-13Nb alloy consists of a single β phase due to the β-stabilizing effect of Nb. •The martensitic transformation temperatures decrease with increasing Nb content. •Ti-30Zr-9Nb alloy shows the maximum shape memory effect of 1.61%.

Cyclic deformation of NiTi shape memory alloys

International Nuclear Information System (INIS)

Liu Yong; Van Humbeeck, J.; Xie Zeliang

1999-01-01

Recently, there is an increasing interest in applying the high damping capacity of shape memory alloys (SMAs). The purpose is to explore the feasibility of those materials for the protection of buildings and other civil constructions as a result of earthquake damages. So far, few experimental results have been reported concerning the mechanical cyclic behaviour of SMAs in their martensitic state (ferroelastic). In the present work, the experimental results on the mechanical behaviour of martensitic NiTi SMAs under tension-compression cyclic deformation up to strains of ±4% are summarized with major attention to the damping capacity, characteristic stresses and strains as a function of deformation cycles. Effect of strain rate, strain amplitude and annealing condition on the martensite damping is summarized. Explanation of the cyclic hardening and cyclic softening phenomenon is proposed based on TEM observations. (orig.)

Quasi-static characterisation of trained pseudoelastic shape memory alloy wire subjected to cyclic loading: transformation kinetics

DEFF Research Database (Denmark)

Enemark, Søren; Santos, Ilmar

2016-01-01

A kinetic law for constitutive modelling of shape memory alloys is proposed in order to increase model predictability in comparison with experimental data. The proposed law is based on cubic Bézier curves and contains curvature controlling parameters. The kinetic law and also the Duhem–Madelung sub......-loop model are implemented in a state-of-the-art constitutive model based on the framework by Lagoudas and coworkers. The original and modified models are fitted to consistent experimental results from mechanical cyclic loading under isothermal conditions (0–800 MPa, 30–70 °C) of a trained pseudoelastic...... shape memory alloy wire. Quantitative measures of goodness of fit show that both models perform well, but use of the modified model results in 31% reduction of the residual standard deviation compared with the original model (21.4 versus 14.8 MPa) in model calibration and 23% in model validation...

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

A new intratracheal stent made from nitinol, an alloy with "shape memory effect".

Science.gov (United States)

Vinograd, I; Klin, B; Brosh, T; Weinberg, M; Flomenblit, Y; Nevo, Z

1994-05-01

Temporary or permanent tracheal splinting in pediatric patients may be indicated in tracheomalacia or bronchomalacia, repair of congenital tracheal stenosis, and after tracheal resection. This study presents the results of the development of a new intraluminal airway stent made from titanium alloy, a metal with "shape memory effect". At low temperatures (martensitic state) the titanium alloy stent can be fashioned into a specific shape; then when heated to a higher temperature (austenitic state) the stent alters its shape, only to regain its original shape when recooled to the lower temperature. The stent, connected to a small electric power supply, was introduced into 20 young rabbits with the use of a 2.5 cm rigid bronchoscope. After implantation in the martensitic state the stent was warmed to 40 degrees C, the austenitic state, by an electric current of 1.5 to 3 ampere for 1 to 2 seconds. After a period of 8 to 10 weeks the stent was removed (in its martensitic state) through the same-sized bronchoscope after being cooled with 3 to 4 ml of 80% alcohol solution at 6 degrees C. No signs of airway obstruction developed in any of the animals after implantation or extraction of the stent. The biomechanical properties of the trachea, as shown by strain measurements with the use of incremental forces, showed significant differences between the stented and unstented segments (p stent adequately fulfilled the requirements of a temporary intraluminal airway splint, and because of its unique feature of shape memory effect the stent could be inserted, fixed, and removed easily, even in very small airways.

Martensitic Transformation and Superelasticity in Fe-Mn-Al-Based Shape Memory Alloys

Science.gov (United States)

Omori, Toshihiro; Kainuma, Ryosuke

2017-12-01

Ferrous shape memory alloys showing superelasticity have recently been obtained in two alloy systems in the 2010s. One is Fe-Mn-Al-Ni, which undergoes martensitic transformation (MT) between the α (bcc) parent and γ' (fcc) martensite phases. This MT can be thermodynamically understood by considering the magnetic contribution to the Gibbs energy, and the β-NiAl (B2) nanoprecipitates play an important role in the thermoelastic MT. The temperature dependence of critical stress for the MT is very small (about 0.5 MPa/°C) due to the small entropy difference between the parent and martensite phases in the Fe-Mn-Al-Ni alloy, and consequently, superelasticity can be obtained in a wide temperature range from cryogenic temperature to about 200 °C. Microstructural control is of great importance for obtaining superelasticity, and the relative grain size is among the most crucial factors.

Temperature dependence of magnetic susceptibility in the vicinity of martensitic transformation in ferromagnetic shape memory alloys

Czech Academy of Sciences Publication Activity Database

Zablotskyy, Vitaliy A.; Pérez-Landazábal, J.I.; Recarte, V.; Gómez-Polo, C.

2010-01-01

Roč. 22, č. 31 (2010), 316004/1-316004/7 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100520 Keywords : shape memory alloys * magnetic susceptibility * martensitic transition * magnetic domains Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.332, year: 2010

Influence of compressive load conditions and thickness on the two-way shape memory behavior in tube-shaped NiTi alloy

International Nuclear Information System (INIS)

Yoo, Young Ik; Shin, Dong Kil; Lee, Jung Ju; Lee, Chang Ho

2012-01-01

The two-way shape memory behavior of Ni 55 Ti 45 was investigated to develop a tube-shaped NiTi actuator which could generate a large amount of force. The two-way shape memory effect (TWSME) was induced by thermal cycling under various amounts of constant compressive stress. Six specimens with the same outer diameter and different thickness were used to apply the TWSME to an actuator. A fast saturation tendency of the recovery strain was shown through training at each level of constant stress, after which the two-way shape memory strain was quantitatively measured during thermal cycling for each level of applied stress. From the results, the maximum two-way strain value was obtained after training at a constant level of stress and then decreased thereafter. In addition, the two-way strain was found to depend on the thickness of the tube-shaped specimen. All specimens could be divided into two groups depending on the rate of increase in the two-way strain. After two-way strain was obtained, the two-way recovery stress was measured to verify the performance of the sample as an actuator. The results showed that the two-way recovery stress behavior was similar to the two-way strain; if the optimal thickness of the specimen and the stress applied for training are used for the development of the TWSME, tube-shaped NiTi using the TWSME can replace one-way shape memory alloys. (paper)

In vitro corrosion behaviour of Ti-Nb-Sn shape memory alloys in Ringer's physiological solution.

Science.gov (United States)

Rosalbino, F; Macciò, D; Scavino, G; Saccone, A

2012-04-01

The nearly equiatomic Ni-Ti alloy (Nitinol) has been widely employed in the medical and dental fields owing to its shape memory or superelastic properties. The main concern about the use of this alloy derives form the fact that it contains a large amount of nickel (55% by mass), which is suspected responsible for allergic, toxic and carcinogenic reactions. In this work, the in vitro corrosion behavior of two Ti-Nb-Sn shape memory alloys, Ti-16Nb-5Sn and Ti-18Nb-4Sn (mass%) has been investigated and compared with that of Nitinol. The in vitro corrosion resistance was assessed in naturally aerated Ringer's physiological solution at 37°C by corrosion potential and electrochemical impedance spectroscopy (EIS) measurements as a function of exposure time, and potentiodynamic polarization curves. Corrosion potential values indicated that both Ni-Ti and Ti-Nb-Sn alloys undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Ti-18Nb-5Sn alloy. Significantly low anodic current density values were obtained from the polarization curves, indicating a typical passive behaviour for all investigated alloys, but Nitinol exhibited breakdown of passivity at potentials above approximately 450 mV(SCE), suggesting lower corrosion protection characteristics of its oxide film compared to the Ti-Nb-Sn alloys. EIS studies showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The obtained EIS spectra were analyzed using an equivalent electrical circuit representing a duplex structure oxide film, composed by an outer and porous layer (low resistance), and an inner barrier layer (high resistance) mainly responsible for the alloys corrosion resistance. The resistance of passive film present on the metals' surface

3D phenomenological constitutive modeling of shape memory alloys based on microplane theory

International Nuclear Information System (INIS)

Mehrabi, R; Kadkhodaei, M

2013-01-01

This paper concerns 3D phenomenological modeling of shape memory alloys using microplane theory. In the proposed approach, transformation is assumed to be the only source of inelastic strain in 1D constitutive laws considered for any generic plane passing through a material point. 3D constitutive equations are derived by generalizing the 1D equations using a homogenization technique. In the developed model, inelastic strain is explicitly stated in terms of the martensite volume fraction. To compare this approach with incremental constitutive models, such an available model is applied in its 1D integral form to the microplane formulation, and it is shown that both the approaches produce similar results for different uniaxial loadings. A nonproportional loading is then studied, and the results are compared with those obtained from an available model in which the inelastic strain is divided into two separate portions for transformation and reorientation. A good agreement is seen between the results of the two approaches, indicating the capability of the proposed microplane formulation in predicting reorientation phenomena in shape memory alloys. The results of the model are compared with available experimental results for a nonproportional loading path, and a good agreement is seen between the findings. (paper)

On the widths of the hysteresis of mechanically and thermally induced martensitic transformations in Ni-Ti-based shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Jaeger, Stefanie; Maass, Burkhard; Frenzel, Jan; Schmidt, Marvin; Ullrich, Johannes; Seelecke, Stefan; Schuetze, Andreas; Kastner, Oliver; Eggeler, Gunther [Bochum Univ. (Germany). Inst. fuer Werkstoffe

2015-10-15

It is well known that a good crystallographic compatibility between austenite and martensite in Ni-Ti-based shape memory alloys results in narrow thermal hystereses (e.g. Ball and James, Arch. Ration. Mech. Anal., 1987). The present work suggests that a good crystallographic fit is moreover associated with a small mechanical hysteresis width, observed during a forward and reverse stress-induced transformation. Furthermore, shape memory alloys with a good crystallographic fit show smaller transformation strains. The results obtained in the present study suggest that these correlations are generic and apply to binary Ni-Ti (with varying Ni contents) and quaternary Ni-Ti-Cu-X (X = Cr, Fe, V) alloys. For binary Ni-Ti, it was observed that Ni-rich compositions (good lattice fit) show a lower accumulation of irreversible strains during pseudoelastic cycling.

Annealing behavior and shape memory effect in NiTi alloy processed by equal-channel angular pressing at room temperature

International Nuclear Information System (INIS)

Shahmir, Hamed; Nili-Ahmadabadi, Mahmoud; Wang, Chuan Ting; Jung, Jai Myun; Kim, Hyoung Seop; Langdon, Terence G.

2015-01-01

A martensitic NiTi shape memory alloy was processed successfully by equal-channel angular pressing (ECAP) for one pass at room temperature using a core–sheath billet design. The annealing behavior and shape memory effect of the ECAP specimens were studied followed by post-deformation annealing (PDA) at 673 K for various times. The recrystallization and structural evolution during annealing were investigated by differential scanning calorimetry, dilatometry, X-ray diffraction, transmission electron microscopy and microhardness measurements. The results indicate that the shape memory effect improves by PDA after ECAP processing. Annealing for 10 min gives a good shape memory effect which leads to a maximum in recoverable strain of 6.9 pct upon heating where this is more than a 25 pct improvement compared with the initial state

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

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.

Plugging of feed inlet tube upstands with Ni/Ti shape memory alloy plugs - Heysham 1 power station

International Nuclear Information System (INIS)

Mathews, A.J.

1988-01-01

The paper contains a description of a new approach for Plugging feed inlet tubes of Gas-Cooled Reactors. Instead of utilizing the original explosive method plugging by fitting a shape memory alloy plug into the upstand is being described. (author)

Dynamical Jumps in a Shape Memory Alloy Oscillator

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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.

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)

On the shock response of the shape memory alloy, NiTi

International Nuclear Information System (INIS)

Millett, J.C.F.; Bourne, N.K.; Stevens, G.S.; Gray, G.T. III

2002-01-01

There has been recent interest in the behaviour of the shape-memory alloy NiTi since it undergoes a stress-induced phase change at a low stress value. It has been additionally noted that the NiTi does not appear to exhibit a Hugoniot elastic limit (HEL) in the way normally associated with other metals. In order to investigate the possible mechanisms operating to give rise to these effects, a series of plate impact experiments have been conducted in order to probe the material's response to shock. In particular attention has been paid to determination of the material Hugoniot in order to ascertain whether the observed features of the response may be explained. A series of other shots where shaped waves are applied are described in order to probe the lower rate response

Simulating Solid-Solid Phase Transition in Shape-Memory Alloy Microstructure by Face-Offsetting Method

International Nuclear Information System (INIS)

Bellur Ramaswamy, Ravi S.; Tortorelli, Daniel A.; Fried, Eliot; Jiao Xiangmin

2008-01-01

Advances in the understanding of martensitic transformations (diffusionless, solid-solid phase transformations) have been instrumental to the recent discovery of new low hysteresis alloys. However, some key fundamental issues must be better understood to design still better alloys. Restricting attention to antiplane shear, we use finite element analysis to model the shape-memory alloy microstructure within the Abeyaratne-Knowles continuum thermomechanical framework and use an interface kinetic relation of the kind proposed by Rosakis and Tsai. Geometric singularities and topological changes associated with microstructural evolution pose significant numerical challenges. We address such challenges with a recently developed front-tracking scheme called the face-offsetting method (FOM) to explicitly model phase interfaces. Initial results demonstrate the effectiveness of FOM in resolving needle-like twinned microstructures

Magnetic Shape Memory Alloys as smart materials for micro-positioning devices

Directory of Open Access Journals (Sweden)

A. Hubert

2012-10-01

Full Text Available In the field of microrobotics, actuators based on smart materials are predominant because of very good precision, integration capabilities and high compactness. This paper presents the main characteristics of Magnetic Shape Memory Alloys as new candidates for the design of micromechatronic devices. The thermo-magneto-mechanical energy conversion process is first presented followed by the adequate modeling procedure required to design actuators. Finally, some actuators prototypes realized at the Femto-ST institute are presented, including a push-pull bidirectional actuator. Some results on the control and performances of these devices conclude the paper.

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.

Heat treatments and thermomechanical cycling influences on the R-phase in Ti-Ni shape memory alloys

Directory of Open Access Journals (Sweden)

Cezar Henrique Gonzalez

2010-09-01

Full Text Available This article studies changes observed on the R-phase thermoelastic behavior in a near-equiatomic Ti-Ni shape memory alloy. Three kinds of procedures have been performed: different treatments, thermomechanical cycling under constant loading in shape memory helical springs and thermal cycling in as-treated and trained samples. Several heat treatments were carried out to investigate evolution of the R-phase by differential scanning calorimetry (DSC. A heat treatment was chosen on which R-phase is absent. Shape memory springs were produced and submitted to a training process in an apparatus by tensioning the springs under constant loading. Thermal cycling in DSC was realized in as-treated and trained samples. Several aspects of one-step (B2→B19' and two-steps (B2→R→B19' martensitic transformations and R-phase formation and their evolution during tests were observed and discussed.

Shape Memory Alloy (SMA)-Based Launch Lock

Science.gov (United States)

Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph

2014-01-01

Most NASA missions require the use of a launch lock for securing moving components during the launch or securing the payload before release. A launch lock is a device used to prevent unwanted motion and secure the controlled components. The current launch locks are based on pyrotechnic, electro mechanically or NiTi driven pin pullers and they are mostly one time use mechanisms that are usually bulky and involve a relatively high mass. Generally, the use of piezoelectric actuation provides high precession nanometer accuracy but it relies on friction to generate displacement. During launch, the generated vibrations can release the normal force between the actuator components allowing shaft's free motion which could result in damage to the actuated structures or instruments. This problem is common to other linear actuators that consist of a ball screw mechanism. The authors are exploring the development of a novel launch lock mechanism that is activated by a shape memory alloy (SMA) material ring, a rigid element and an SMA ring holding flexure. The proposed design and analytical model will be described and discussed in this paper.

Effect of magnetostatic interactions on twin boundary motion in Ni-Mn-Ga magnetic shape memory alloy

Czech Academy of Sciences Publication Activity Database

Heczko, Oleg; Vokoun, David; Kopecký, Vít; Beleggia, M.

2015-01-01

Roč. 6, Jul (2015), s. 1000204 ISSN 1949-307X R&D Projects: GA ČR GA15-00262S Institutional support: RVO:68378271 Keywords : magnetism in solids * demagnetization factors * magnetostatic interactions * shape memory alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.978, year: 2015

An informatics approach to transformation temperatures of NiTi-based shape memory alloys

International Nuclear Information System (INIS)

Xue, Dezhen; Xue, Deqing; Yuan, Ruihao; Zhou, Yumei; Balachandran, Prasanna V.; Ding, Xiangdong; Sun, Jun; Lookman, Turab

2017-01-01

The martensitic transformation serves as the basis for applications of shape memory alloys (SMAs). The ability to make rapid and accurate predictions of the transformation temperature of SMAs is therefore of much practical importance. In this study, we demonstrate that a statistical learning approach using three features or material descriptors related to the chemical bonding and atomic radii of the elements in the alloys, provides a means to predict transformation temperatures. Together with an adaptive design framework, we show that iteratively learning and improving the statistical model can accelerate the search for SMAs with targeted transformation temperatures. The possible mechanisms underlying the dependence of the transformation temperature on these features is discussed based on a Landau-type phenomenological model.

P-phase precipitation and its effect on martensitic transformation in (Ni,Pt)Ti shape memory alloys

International Nuclear Information System (INIS)

Gao, Y.; Zhou, N.; Yang, F.; Cui, Y.; Kovarik, L.; Hatcher, N.; Noebe, R.; Mills, M.J.; Wang, Y.

2012-01-01

A new precipitate phase named P-phase has recently been identified in (Ni,Pt)Ti high temperature shape memory alloys. In order to understand the roles played by the fine coherent P-phase precipitates in determining the martensitic transformation temperature (M s ), strength of the B2 matrix phase, dimensional stability and shape memory effect of the alloys, a phase field model of P-phase precipitation is developed. Model inputs, including lattice parameters, precipitate–matrix orientation relationship, elastic constants and free energy data, are obtained from experimental characterization, ab initio calculations and thermodynamic databases. Through computer simulations, the shape and spatial distribution of the P-phase precipitates, as well as the compositional and stress fields around them, are quantitatively determined. On this basis, the elastic interaction energy between the P-phase precipitates and a martenstic nucleus is calculated. It is found that both the chemical non-uniformity and stress field associated with the P-phase precipitates are in favor of the martensitic transformation. Their relative contributions to the increase in M s temperature are quantified as a function of aging time and the result seems to agree with the experimental measurements. The shape and spatial distribution of the P-phase precipitates predicted by the simulations also agree well with experimental observations.

Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response.

Science.gov (United States)

Hu, Li; Jiang, Shuyong; Zhou, Tao; Tu, Jian; Shi, Laixin; Chen, Qiang; Yang, Mingbo

2017-10-13

Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA) are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM). Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD) density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response

Directory of Open Access Journals (Sweden)

Li Hu

2017-10-01

Full Text Available Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM. Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

Composition and temperature dependence of twinning stress in non-modulated martensite of Ni-Mn-Ga-Co-Cu magnetic shape memory alloys

Czech Academy of Sciences Publication Activity Database

Soroka, A.; Sozinov, A.; Lanska, N.; Rameš, Michal; Straka, Ladislav; Ullakko, K.

2018-01-01

Roč. 144, Feb (2018), s. 52-55 ISSN 1359-6462 R&D Projects: GA ČR GA16-00043S Institutional support: RVO:68378271 Keywords : Heusler phases * martensite * ferromagnetic shape memory alloy * magnetic shape memory * twinning Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.747, year: 2016

The study of mechanical properties and reactive stresses in the i-Ni-Nb shape memory alloys

International Nuclear Information System (INIS)

Popov, N.N.; Sysoeva, T.I.; Lar'kin, V.F.; Vedernikova, I.I.; Prokoshkin, S.D.

2007-01-01

One investigated into the effect of the induced deformation value, rate and temperature, of the thermal treatment procedure and of the chemical composition on the mechanical properties and the development of the reactive stresses in Ti-Ni-Nb system shape memory alloys. One showed the effect of the material composition and of the deformation temperature on the mechanical features of the investigated alloys. One determined the temperature and deformation conditions ensuring the maximum level of the reactive stresses in the alloys. One revealed the dependence of the maximum reactive stress value on the austenite mechanical features, namely, on its yield limit. One chose Ti-Ni-Nb alloy compositions applicable in the pipeline thermomechanical connections [ru

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

Relationship between thermomechanical treatment, microstructure and α' martensite in stainless Fe-based shape memory alloys

International Nuclear Information System (INIS)

Otubo, J.; Mei, P.R.; Shinohara, A.H.; Suzuki, C.K.

1999-01-01

This work presents some preliminary results relating training treatment, training temperature and the formation of α' martensite to the shape recovery effect of stainless shape memory alloys. For the composition tested, the sample shows some mechanical memory (constant tensile stress at 4% strain and constant yield stress throughout the training cycles) with a very good shape recovery (95% after 4% tensile strain) at a training temperature of 873 K. Its residual strain is related to the generation of perfect dislocations only. For the sample trained at 723 K, the residual strain could be attributed to incomplete reversion of stress-induced ε martensite, in part due to the blocking effect of α' martensite and also to the generation of perfect dislocations. The influence of α' martensite on shape recovery is relative and is dependent on training temperature, and the preferential growth of α' martensite is shown to occur for large grain size. (orig.)

Finding the energy source for self-propagating high-temperature synthesis production of NiTi shape memory alloy

Czech Academy of Sciences Publication Activity Database

Novák, P.; Školáková, A.; Pignol, D.; Průša, F.; Salvetr, P.; Kubatík, Tomáš František; Perriere, L.; Karlík, M.

2016-01-01

Roč. 181, September (2016), s. 295-300 ISSN 0254-0584 Institutional support: RVO:61389021 Keywords : NiTi * Shape memory alloys * Powder metallurgy * Microstructure Subject RIV: JG - Metallurgy Impact factor: 2.084, year: 2016 http://www.sciencedirect.com/science/article/pii/S025405841630476X

Modiolus-Hugging Intracochlear Electrode Array with Shape Memory Alloy

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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.

Ni4Ti3 precipitate structures in Ni-rich NiTi shape memory alloys