Quasi-static extension of shape memory wires under constant load

1997 ◽  
Vol 45 (1) ◽  
pp. 67-74 ◽  
Author(s):  
T.W. Shield ◽  
P.H. Leo ◽  
W.C.C. Grebner
Keyword(s):  
Shape Memory ◽  
Constant Load ◽  
Static Extension

Transformation Behavior and Shape Memory Characteristics of Ti-45Ni-5Cu(at%) Alloy Ribbons Fabricated by Melt Spinning

2004 ◽  
Vol 449-452 ◽  
pp. 1093-1096 ◽  
Author(s):  
Tae Hyun Nam ◽  
Jae Hwa Lee ◽  
Tae Yeon Kim ◽  
Yeon Wook Kim
Keyword(s):  
Shape Memory ◽  
Melt Spinning ◽  
Constant Load ◽  
X Ray Diffraction ◽  
Transformation Behavior ◽  
X Ray ◽  
Density Of Dislocations ◽  
Large Lattice ◽  
One Step ◽  
Memory Characteristics

Transformation behaviors and shape memory characteristics of Ti-45Ni-5Cu alloy ribbons fabricated by melt spinning were investigated by means of optical microscopy, differential scanning calorimetries(DSC), X-ray diffraction and thermal cycling tests under constant load. They depended largely on temperatures of liquid metal. The B2-B19-B19’ two-step transformation occurred in the ribbons fabricated with the liquid whose temperature was higher than 1723 K, while the B2-B19’ one-step transformation occurred in the ribbons with the liquid at 1673 K. The stabilization of the B19 martensite in Ti-45Ni-5Cu alloy ribbons was ascribed to the high density of dislocations which made strong resistance to large lattice deformation associated with a formation of the B19’ martensite.

Functionally Graded Ti-Ni Shape Memory Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 3169-3172 ◽  
Author(s):  
Tae Hyun Nam ◽  
Cheol Am Yu ◽  
Yun Jung Lee ◽  
Yinong Liu
Keyword(s):  
Temperature Gradient ◽  
Shape Memory ◽  
Tensile Tests ◽  
Constant Load ◽  
Functionally Graded ◽  
Scanning Calorimetry ◽  
Treated Sample ◽  
Ni Alloy ◽  
Temperature Ranges ◽  
Cold Worked

Shape memory characteristics and superelasticity of an temperature gradient annealing(TGA) treated equiatomic Ti-Ni alloy have been investigated by means of differential scanning calorimetry(DSC), thermal cycling tests under constant load and tensile tests. By annealing 25% cold worked alloy under the temperature gradient from 658 K to 466 K, 7 K variation in TR*and 19 K variation in Ms* were obtained along the length of sample(150mm). Temperature dependence of transformation elongation(dε/dT) of TGA treated Ti-Ni alloy wires was in the range of 0.05 %/K and 0.01 %/K depending on annealing temperature ranges. The dε/dT obtained from TGA treated sample under the temperature gradient from 658 K to 466 K was 0.03 %/K. TGA treated alloy showed the clear superelastic recovery.

scholarly journals NiTi shape memory alloy: physical and tribological characterization

2018 ◽  
Vol 27 (1-2) ◽  
Author(s):  
Pardeep Sharma
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Wear Behavior ◽  
Research Work ◽  
Constant Load ◽  
Binder Content ◽  
Niti Shape Memory Alloy ◽  
X Ray Diffraction ◽  
The Coefficient Of Friction ◽  
Tribological Characterization

AbstractThe current research work focuses on the mechanical and tribological behavior of an NiTi shape memory alloy (SMA) processed with the help of powder metallurgy. SMAs have found applications in the medical, space and aerospace industries with usage in the manufacturing of microelectromechanicals (MEMS) and as actuators in the electronic industry. The wear behavior of a material greatly affects its performance. The wear behavior of an SMA can be determined with the help of the dry abrasion test. The increase in binder content and rotational speed at a constant load increases the wear rate of SMA alloys. The coefficient of friction decreases with the usage of alloys. A decrease in density has been found, as well as porosity, with the increasing content of binder in the alloy. Density decreases from 6.7 to 5.1 g/cm3 while porosity decreases from 57 to 23% with increased binder content. Scanning electron microscopy (SEM) and X-ray diffraction has been used for the investigation of surface morphology and phases present in the alloy.

Implementation and Investigation of a Compact, Powerful System for Diagnosis and Control of Shape Memory Alloys in Technical Applications

2019 ◽  
Author(s):  
Max Kaiser ◽  
Nils Neblung ◽  
Martin Gurka
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Electrical Resistance ◽  
Control Strategies ◽  
Memory Systems ◽  
Constant Load ◽  
Resistance Change ◽  
Model Based ◽  
And Control

Abstract In this paper we present the development, implementation and testing of a compact system for diagnosis and control of actuators based on metallic shape memory alloys (SMA). Using NiTi-SMA, very compact, cost-effective and lightweight actuation systems can be realized. In applications where the SMA is activated by internal Joule heating or its condition is diagnosed by the self-sensing of its electrical resistance, an electrical system capable of reliably measuring very small resistance changes (< 1 ohm) without affecting the phase-state of the SMA is required. In addition, the system must offer the possibility to evaluate the nonlinear, hysteresis-afflicted behavior of the SMA and to handle this difficulty, e.g. utilizing a model-based control. This paper presents a simple compact and adaptive system based on a microcontroller that meets these requirements. Detailed functional tests were carried out with the system to establish a correlation between the change in electrical resistance in the range < 200 mOhm and the current strain state of the actuator. For this purpose, a first series of tests was performed, with the SMA wires working against a constant load. In a second tests series, the SMA wires worked against springs of different stiffness. The use of a microcontroller enables simple implementation of different control strategies. The control system for the non-linear resistance change utilizes a fuzzy logic which divides the control algorithm into three regimes. In the regime of the martensitic phase transformation a PI-controller is used. The state of actuators with an absolute electrical resistance < 1 Ohm and a resistance change < 200 mohm associated with the phase transformation can be precisely measured and controlled with an accuracy < 10 mohm. The system can be configured with little effort for different tasks and shape memory systems of different sizes. Furthermore, it is possible to implement more complex control algorithms up to model-based controllers.

scholarly journals Investigation on thermo-mechanical behavior of shape memory alloy actuator

2017 ◽  
Vol 66 (4) ◽  
pp. 751-760
Author(s):  
Milena Kurzawa ◽  
Dorota Stachowiak
Keyword(s):  
Shape Memory Alloy ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Design Procedure ◽  
Constant Load ◽  
Heating And Cooling ◽  
Sma Actuator ◽  
Set Up ◽  
Hysteresis Characteristics

Abstract The paper presents the design procedure and elaborated software for designing calculation of the shape memory alloy (SMA) actuator. The thermo-mechanical behavior of a linear SMA actuator has been studied. The experimental set-up was especially designed to perform the thermo-mechanical characterization of SMA wires. The stroke (s) - temperature (T) hysteresis characteristics have been determined. The cycle of heating and cooling has been performed under a constant load. The model for the SMA actuator s - T behavior has been proposed and successfully implemented. The selected results and conclusions have been presented. The concept proposal of the linear actuator using the SMA wire has been given.

Shape Memory Effect and Superelasticity of an Equiatomic Ti-Ni Alloy with Surface Sulfide Layers

2006 ◽  
Vol 510-511 ◽  
pp. 262-265
Author(s):  
Tae Hyun Nam ◽  
Shin Goo Hur ◽  
Jae Hwa Lee ◽  
Gyu Bong Cho
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Tensile Tests ◽  
Constant Load ◽  
Ni Alloy ◽  
Memory Characteristics ◽  
Scanning Electron ◽  
Start Temperature

Shape memory characteristics and superelasticity of an equiatomic Ti-Ni alloy with surface sulfide layers were investigated by means of thermal cycling tests under constant load, tensile tests, and scanning electron microscopy. Martensitic transformation start temperature (Ms) increased by sulfidation, which is ascribed to a compressive stress imposed by surface sulfide layers. Surface sulfide layers were found to make transformation elongation be small when their thickness was less than 5 ㎛. This is ascribed to the fact that the surface sulfide layers were not detached from substrates and constrained martensitic transformation. When thickness of the surface sulfide layers was 35 ㎛, transformation elongation was not affected by them because they were detached during transformation. Superelastic recovery decreased by the sulfide layers when their thickness was about 5 ㎛, while it did not change when the thickness was about 35 ㎛.

Modeling and Experiments for Deformation Under Load in Ni-Mn-Ga Ferromagnetic Shape Memory Alloy

1999 ◽  
Vol 604 ◽  
Author(s):  
S. J. Murray ◽  
S. M. Allen ◽  
R. C. O'Handley
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Energy ◽  
Constant Load ◽  
Constant Field ◽  
Ferromagnetic Shape Memory Alloy ◽  
Strain Behavior ◽  
Modeling And Experiments ◽  
Orthogonal Field ◽  
Ferromagnetic Shape Memory

AbstractA simple model is proposed to relate strain, stress, field and anisotropy in a ferromagnetic shape memory alloy (FSMA) and experiments were performed to test the validity of the model. The model is presented as applied to the case of orthogonal field and load in a NiMn-Ga FSMA. The model predicts threshold-type strain behavior as field changes at constant load or as load changes with constant field. The measured behavior of strain with stress at constant field approximated the predictions of the model. Field-induced strain remained constant at about 6% with the addition of stress until such a stress was applied that the mechanical energy overcame the anisotropy of the sample and the strain was reduced to 0. The model's predictions of critical strain behavior with applied field at constant stress were qualitatively accurate at some stress levels, but under-predicted the field necessary to produce strain.

Deformation Behavior of Functionally Graded Ti-Ni Shape Memory Alloys

2007 ◽  
Vol 544-545 ◽  
pp. 211-214 ◽  
Author(s):  
Tae Hyun Nam ◽  
Hyun Gon Kim ◽  
Ju Young Choi ◽  
Jung Moo Lee ◽  
Suk Bong Kang ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Annealing Temperature ◽  
Tensile Tests ◽  
Constant Load ◽  
Functionally Graded ◽  
Ni Alloy

Deformation behavior of temperature gradient anneal(TGA) treated Ti-50.0Ni(at%) alloys were investigated by means of thermal cycling tests under constant load and tensile tests. TGA treated Ti-Ni alloy wires showed a sequential deformation behavior along the length of the specimen since the stress required for the B2-B19’ transformation increased with decreasing annealing temperature. Considerably large residual elongation(about 0.4 %) occurred in the TGA treated Ti-Ni alloy under the applied stress of 80 MPa, which is ascribed to the fact that yield stress of the sample annealed at 823 K is lower than the stress required for the B2-B19’ transformation of the sample annealed at 658 K.

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