Recoverable strain storage capacity of shape memory polyethylene

2013 ◽  
Vol 51 (13) ◽  
pp. 1033-1040 ◽  
Author(s):  
Robin Hoeher ◽  
Thomas Raidt ◽  
Maik Rose ◽  
Frank Katzenberg ◽  
Joerg C. Tiller
Keyword(s):  
Shape Memory ◽  
Storage Capacity ◽  
Recoverable Strain ◽  
Strain Storage

Experimental and numerical studies on a novel shape-memory alloy wire–woven trusses capable of undergoing large deformation

2019 ◽  
Vol 30 (15) ◽  
pp. 2283-2298
Author(s):  
Zhixiang Rao ◽  
Xiaojun Yan ◽  
Xiaoyong Zhang ◽  
Bin Zhang ◽  
Jun Jiang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Large Deformation ◽  
Residual Deformation ◽  
Shape Memory Alloy Wire ◽  
Static Compression ◽  
Recoverable Strain ◽  
Alloy Wire ◽  
Assembly Method ◽  
Finite Element Analysis Simulation

Currently, most wire-woven trusses are fabricated with traditional metals such as steel and aluminum, thus the deformation ability is constrained due to the low yield strain of common metals. Shape-memory alloy is a kind of smart material which can bear large recoverable strain while producing hysteresis. Due to the unique capacity of large deformation and remarkable damping property of the shape-memory alloy, a novel lattice trusses assembled by superelastic shape-memory alloy coil springs was proposed. Furthermore, the treatment processes to prepare the shape-memory alloy coil springs and the assembly method to fabricate the shape-memory alloy wire–woven trusses were also introduced. The quasi-static compression under different maximum deformation and temperatures was performed to investigate the mechanical and thermal responses of the proposed shape-memory alloy wire–woven trusses. Cyclic compression tests were also performed to study the functional fatigue of the shape-memory alloy wire–woven trusses. The proposed wire-woven trusses can undergo up to 80% deformation by compression and recover without evident residual deformation after unloading. Finite element analysis simulation of representative volume element under different deformation was presented. Analytical modeling of the stiffness of shape-memory alloy wire–woven trusses was also carried out. Both the numerical and analytical methods can predict the stiffness within a small deviation.

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

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

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

A Memory Variable Approach to Modeling the Magneto-Mechanical Behavior of Magnetic Shape Memory Alloys

2013 ◽  
Author(s):  
Doug LaMaster ◽  
Heidi Feigenbaum ◽  
Isaac Nelson ◽  
Constantin Ciocanel
Keyword(s):  
Magnetic Field ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Mechanical Strain ◽  
Magnetization Vector ◽  
Unit Cell ◽  
Magnetic Shape Memory ◽  
Magnetic Shape Memory Alloys ◽  
Short Side ◽  
Recoverable Strain

Magnetic shape memory alloys (MSMAs) have attracted interest because of their considerable recoverable strain (up to 10%) and fast response time (1 kilohertz or higher). MSMAs are comprised of martensitic variants that have tetragonal unit cells and a magnetization vector that is innately aligned with the short side of the unit cell. These variants rotate either to align the magnetization vector with an applied magnetic field or to align the short side of the unit cell with an applied compressive stress. This reorientation leads to a mechanical strain and an overall change in the material’s magnetization, allowing MSMAs to be used as actuators, sensors, and power harvesters. This paper builds upon the work of Kiefer and Lagoudas [4,5] as well as improvements proposed by LaMaster et al. [1] to present a thermodynamic based model to predict the response of an MSMA to axial mechanical loading and transverse magnetic loading. This work is unique, however, in its use of a memory variable, which references the last stable configuration. This is similar to the approach used by Saint-Sulpice [2] in modeling SMA wires. The resulting model has zero driving force for reorientation of variants at the beginning of any load and again when the load is removed. Thus the model predicts what is seen physically, that the material is stable when no magneto-mechanical load is present. Furthermore, this model is more physical and less empirical than others in the literature, having only 2 material parameters associated with the stress-strain or stress-field response. In addition, this model includes evolution rules for the magnetic domain volume fractions and the angle of rotation of the magnetization vectors based on thermodynamic requirements. The resulting model is calibrated and predictions are compared with both the more established Keifer and Lagoudas model as well as experimental data. Results show decent correlation with experiments. The model can be further improved by calibrating the demagnetization factor to experimentally measured changes in magnetic field.

Texture Evolution during Diffusional Heat Treatment from Roll-Bonded Ti/Ni Laminates to TiNi Shape Memory Alloy Sheets

2007 ◽  
Vol 539-543 ◽  
pp. 3442-3447 ◽  
Author(s):  
Hirofumi Inoue ◽  
K. Asao ◽  
Masaaki Ishio ◽  
Takayuki Takasugi
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Early Stage ◽  
Texture Evolution ◽  
Reactive Diffusion ◽  
Thin Sheets ◽  
Orientation Relationships ◽  
Nickel Metal ◽  
Recoverable Strain

TiNi shape memory alloy thin sheets were produced from titanium and nickel metal sheets by a new processing consisting of repetitive roll-bonding and diffusional heat treatment. TiNi sheets after heat treatment at a relatively low temperature for a long time exhibited fairly isotropic and high shape-recoverable strain, because a near {111} B2-phase texture such as {223}<110> and {332}<113> was developed through reactive diffusion during heat treatment. In the early stage of reactive diffusion, intermetallic layers of Ti2Ni, TiNi and Ni3Ti were formed at once at the Ti/Ni interfaces of the roll-bonded laminate and then growth of a TiNi phase took place with the progress of interdiffusion. Texture of the final TiNi thin sheets, therefore, is derived from that of TiNi layers generated at the Ti/Ni interfaces, which is considered to have inherited rolling textures of Ni and Ti layers in the Ti/Ni laminate prior to reactive diffusion under orientation relationships on close-packed plane and direction between parent and product phases.

Sintering and Morphology of Porous Structure in NiTi Shape Memory Alloys for Biomedical Applications

2012 ◽  
Vol 570 ◽  
pp. 87-95 ◽  
Author(s):  
Irfan Haider Abidi ◽  
Fazal Ahmad Khalid
Keyword(s):  
Elastic Modulus ◽  
Shape Memory Alloys ◽  
Porous Structure ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Biomedical Implants ◽  
Recoverable Strain ◽  
Porous Niti ◽  
Niti Shape Memory Alloys

The combination of attractive properties of porous NiTi shape memory alloys like high recoverable strain due to superelasticity and shape memory effect, good corrosion resistance, improved biocompatibilty, low density and stiffness along with its porous structure similar to that of bone make them best materials for biomedical implants. In current study porous NiTi SMAs have been fabricated successfully by space holder technique via pressureless sintering using NaCl powder as a spacer. Various volume fractions of NaCl powders have been involved to study their effect on the pore characteristics as well as on mechanical properties of foam. Porous NiTi with average porosity in the range of 44.3%-63.5% have been fabricated having average pore size 419µm which were very appropriate for various biomedical implants. Porous NiTi SMAs exhibited superelasticity at room temperature and shape memory effect was also determined. Maximum recoverable strain of 6.79% was demonstrated by the porous NiTi alloy with 44.3% porosity and it was diminishing with increasing porosity. Compression strength and elastic modulus have shown a decreasing trend with increasing porosity content. Elastic modulus of porous NiTi extends from 1.38 to 5.42GPa depending upon the pore volume which was very much comparable to that of various kinds of bones.

Effect of Ta Addition on Properties and Microstructures of Fe-28Ni-11.5Al Shape Memory Alloys

2014 ◽  
Vol 787 ◽  
pp. 288-294 ◽  
Author(s):  
Wen Yi Peng ◽  
Neng Wu Yang ◽  
Gui Li Qu ◽  
Wei Wei Wang ◽  
Hai Ping Shi ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Thermal Expansion ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Test Machine ◽  
X Ray Diffraction ◽  
Recoverable Strain ◽  
The Mean

The effects of Ta additions (x=0, 0.5, 1.0, 1.5) in Fe60.5-xNi28Al11.5Tax(at.%) shape memory alloys on microstructure, thermal expansion, and pseudoelasticity of the aged alloys were investigated by metallurgical microscope, X-ray diffraction, SEM, EDS, high-temperature dilatometer spectrometer and pressure test machine. The results showed that with the increment of Ta additions, the γ' phase content increased which strengthened the austenitic matrix, meanwhile the compressive strength, the recoverable strain and the maximum strain of the aging state alloys decreased first and then increased, and the alloy’s residual strain firstly decreased and then increased. When the Ta content was 1.0 at.%, the alloy’s compressive strength, recoverable strain and plastic deformation strain reached its maximum value, 2.5Gpa, 14.4%, and 16.0% respectively. Thus, the alloy had the best pseudo-elastic at this time. The mean thermal expansion coefficient of the alloys decreased with Ta additions, when the Ta content was 1.0 at.%, the mean thermal expansion coefficient was at its minimum.

Functional Properties of Ti-Ni-Based Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 156-161 ◽  
Author(s):  
I. Khmelevskaya ◽  
Sergey Prokoshkin ◽  
Vladimir Brailovski ◽  
K.E. Inaekyan ◽  
Vincent Demers ◽  
...  
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Functional Properties ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Critical Temperatures ◽  
Recoverable Strain ◽  
Ultrafine Grained

The main functional properties (FP) of Ti-Ni Shape Memory Alloys (SMA) are their critical temperatures of martensitic transformations, their maximum completely recoverable strain (er,1 max) and maximum recovery stress (sr max). Control of the Ti-Ni-based SMA FP develops by forming well-developed dislocation substructures or ultrafine-grained structures using various modes of thermomechanical treatment (TMT), including severe plastic deformation (SPD). The present work shows that TMT, including SPD, under conditions of high pressure torsion (HPT), equal-channel angular pressing (ECAP) or severe cold rolling followed by post-deformation annealing (PDA), which creates nanocrystalline or submicrocrystalline structures, is more beneficial from SMA FP point of view than does traditional TMT creating well-developed dislocation substructure. ECAP and low-temperature TMT by cold rolling followed by PDA allows formation of submicrocrystalline or nanocrystalline structures with grain size from 20 to 300 nm in bulk, and long-size samples of Ti-50.0; 50.6; 50.7%Ni and Ti-47%Ni-3%Fe alloys. The best combination of FP: sr max =1400 MPa and er,1 max=8%, is reached in Ti-Ni SMA after LTMT with e=1.9 followed by annealing at 400°C which results in nanocrystalline (grain size of 50 to 80 nm) structure formation. Application of ultrafine-grained SMA results in decrease in metal consumption for various medical implants and devices based on shape memory and superelastiсity effects.

Quantitative predictions of maximum strain storage in shape memory polymers (SMP)

Polymer ◽  
2020 ◽  
Vol 186 ◽  
pp. 122006 ◽  
Author(s):  
Chris C. Hornat ◽  
Marlies Nijemeisland ◽  
Michele Senardi ◽  
Ying Yang ◽  
Christian Pattyn ◽  
...  
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymers ◽  
Maximum Strain ◽  
Strain Storage

The effect of deformation on the banded martensite microstructure in a dilute uranium alloy

1986 ◽  
Vol 44 ◽  
pp. 566-567
Author(s):  
John G. Speer ◽  
David V. Edmonds
Keyword(s):  
Mechanical Behavior ◽  
Shape Memory ◽  
Work Hardening ◽  
Shape Recovery ◽  
Recoverable Strain ◽  
Shape Memory Behavior ◽  
Uranium Alloy ◽  
Work Hardening Rate ◽  
Underlying Mechanisms ◽  
Martensite Microstructure

Experimental observations of shape-memory behavior and related phenomena have been reported for uranium alloy systems. Vandermeer, et al. published the first evidence of shape-memory in uranium alloys using a U-14 at.% Nb alloy. On heating the deformed martensitic phase, complete shape recovery was observed for tensile strains up to 7%. The work hardening rate was very low in the region of recoverable strain, and Vandermeer suggested that the shapememory behavior in these alloys results from the ability of the banded martensite to deform by the movement of glissile interfaces. The present investigation was undertaken in order to examine the effect of deformation on the microstructure of a banded uranium martensite, and to provide a better understanding of the underlying mechanisms responsible for the mechanical behavior of these alloys.

scholarly journals Brief Overview on Nitinol as Biomaterial

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Abdul Wadood
Keyword(s):  
Phase Transformation ◽  
Research And Development ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Recoverable Strain

Shape memory alloys remember their shape due to thermoelastic martensitic phase transformation. These alloys have advantages in terms of large recoverable strain and these alloys can exert continuous force during use. Equiatomic NiTi, also known as nitinol, has a great potential for use as a biomaterial as compared to other conventional materials due to its shape memory and superelastic properties. In this paper, an overview of recent research and development related to NiTi based shape memory alloys is presented. Applications and uses of NiTi based shape memory alloys as biomaterials are discussed. Biocompatibility issues of nitinol and researchers’ approach to overcome this problem are also briefly discussed.

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