• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.881-886
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• 2009

Research into the replacement of injured systems and tissue in the human body is advancing rapidly. Recently, Ti-Ni shape memory alloys have shown excellent biofunctionality related to their shape memory effect and superelasticity. In this study, the effect of an acid or an alkali treatment on the bioactivity in 49Ti-Ni and 51.5Ti-48.5Ni alloys is investigated in an effort to utilize Ti-Ni alloy as a biomaterial. In addition, the biocompatibility in a SBF solution is assessed through in vitro testing. A porous surface was formed on the surface of both alloys after a chemical treatment. According to the in vitro test, apatite formed on the surfaces of both alloys. The forming rate of apatite in the Ti-rich alloy was faster that in the Ni-rich alloy. The formation of apatite provided proof of the bioactivity of the Ti-Ni alloy. A small quantity of Ni was eluted at the initial stage, whereas Ni was not found for 12 days in the Ti-rich alloy and for 8 days in the Ni-rich alloy. In the case of the treated 51.5Ti-Ni alloy, the shape memory property was worsened but the biocompatibility was improved.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.28-33
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• 2014

Recently, the actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. This paper presents a study on the fatigue life of shape memory alloy (SMA) actuators undergoing thermally induced martensitic phase transformation under various stress levels. shape memory recoverable stress and strain of Ti-44.5at.%Ni-8at.%Cu alloys were by means of constant temperature tensile tests. Differential scanning calorimetry (DSC) was employed in order to investigate the transformation characteristics of the alloy before the tests. the results were summarized as follows. The martensite inducing stress incerased with the increasing of the Cu-contents. The fatigue life decreased with the increasing of the test load and the Cu-content. The data acquired will be very useful during the design process of an SMA NiTiCu element as a functional part of an actuator.

• Journal of Powder Materials
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• v.9 no.2
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• pp.96-102
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• 2002

In the present study, equiatomic porous TiNi shape-memory alloys have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental titanium and nickel powders. The porous TiNi alloys thus obtained have an open porous structure with about 64 vol.% porosity, and the pore size is about 1.8 mm. The effect of preheating temperature on the microstructure have been investigated. It is found that the pore size increases with increasing preheating temperature. Moreover, the preheating temperature was shown to have a significant effect on the microstructrue of the SHS-synthesized porous TiNi shape memory alloys.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.1
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• pp.11-16
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• 2007

The fatigue properties of Ti-Ni shape memory alloy wires were investigated. In Ni-rich Ti-Ni shape memory alloys, $Ti_3Ni_4$ precipitates formed by aging treatments are believed to vary the shape memory and mechanical properties. In this study, the effect of aging temperature and aging time on shape memory properties and fatigue life were investigated using Ti-50.9 at% Ni alloy wires. The specimens were solution-treated at 1073 K for 3.6 ks followed by aging at 573 K, 673 K and 773 K for periods between 3.6 ks and 3600 ks. It was found that the fatigue life under a constant stress decreased with increasing aging temperature. When the specimens were aged at 573 K for periods between 36 ks and 360 ks, superior shape memory and fatigue properties were obtained. The fatigue life also decreased when the test temperature and strain amplitude increased. It was concluded that the fatigue life exhibited a linear relationship with the critical stress for slip.

• Journal of the Korean Society of Safety
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• v.24 no.5
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• pp.1-5
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• 2009

NiTiCu alloys can produce a large force per unit volume and operate with a simple mechanism. For this reasons, it has been widely studied for application as a micro actuator. So in this study, one-way and two way shape memory effects of Ti-42.5at%Ni-2.0at%Cu alloys are studied. In the case of one-way shape memory effects, shape memory recoverable stress and strain of this alloys were measured by means of tension and compression tests under constant temperature. The strains by tension and compression stress were perfectly recovered by heating at any testing conditions also shape memory recoverable stress increased to 116 MPa in tension tests and to 260 MPa in compression tests. In the case of two-way shape memory effects, transformation temperatures from thermal cycling under constant uniaxial applied tension and compression loads linearly increased by increasing external loads and their maximum recoverable strain is 3.8% at 100MPa tensile condition and 2.2% at 125 MPa compression condition.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1998.10b
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• pp.7-7
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• 1998

Research activities of Russian Medical Engineering Center and Institute of Medical Materials of Shape Memory Alloys and Implants are presented as follows: ${\bullet}$ The direction of elaboration of porous shape memory alloys for medicine. ${\bullet}$ Medical and technical requirements and physical and mechanical criteria of porous shape memory implants elaboration. ${\bullet}$ Basic laws of heat-, stress- and strain-induced changes of mechanical properties, shape memory effect and superelasticity in porous TiNi-based alloys. ${\bullet}$ Methods of regulation of shape memory effect parameters in porous alloys and methods for controlling the regulation-induced changes of physical and mechanical properties. ${\bullet}$ Original technologies of elaboration of porous alloys In various fields of medicine. ${\bullet}$ Arrangement of serial production of shape memory porous implants and examples of their medical use.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.3 no.1
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• pp.32-43
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• 1995

Ni-Ti alloy has excellent corrosion resistance, biocompatibility, shape memory effect and superelasticity, so it has been used widely in biomedical fields. But it has difficulty in casting due to its high melting temperature and oxygen affinity at high temperature. Recently it has been attempted to cast Ni-Ti alloy using new casting machine and investment. The purpose of this study was to examine the superelastic behavior of cast shape memory Ni-Ti alloy and to compare the mechanical properties of the cast shape memory alloy with those of commercial alloys for removable partial denture framework. Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was cast with dental argon-arc pressure casting machine and Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy, pure titanium were cast as reference. Experimental cast Ni-Ti alloy was treated with heat($500{\pm}2^{\circ}C$) in muffle furnace for 1 hour. Transformation temperature range of cast Ni-Ti alloy was measured with differential scanning calorimetry. The superelastic behavior and mechanical properties of cat Ni-Ti alloy were observed and evaluated by three point bending test, ultimate tensile test, Vickers microhardness test and scanning electron microscope. The results were as follows : 1. Cast Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was found to have superelastic behavior. 2. Stiffness of cast Ni-Ti alloy was considerably lesser than that of commercial alloys for removable partial denture. 3. Permanent deformation was observed in commercial alloys for removable partial denture framework at three point bending test over proportional limit(1.5mm deflection), but was not nearly observed in cast Ni-Ti alloy. 4. On the mechanical properties of ultimate tensile strength, elongation and Vickers microhardness number, cast Ni-Ti alloy was similiar to Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy and pure titanium. With these results, cast Ni-Ti alloy had superelastic behavior and low stiffness. Therefore, it is suggested that cast Ni-Ti alloy may be applicated to base metal alloy for removable partial denture framework.

• Steel and Composite Structures
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• v.48 no.3
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• pp.353-365
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• 2023

Shape memory alloys (SMAs) have emerged as a novel functional material that is being increasingly applied in diverse fields including medical, aeronautical and structural engineering to be used in the active, passive and semi-active structural control devices. This paper is mainly aimed at evaluating the ductility and response modification factor of the steel plate shear wall (SPSW) frames with and without the Ni-Ti shape memory alloys. To this end, different configurations were utilized, in which the walls were used in the first, third, middle, and all stories. The models were numerically analyzed using OpenSees Software. The obtained results indicate that improving the shape memory properties of alloys can greatly enhance the ductility and response modification factor. Furthermore, the model whose first and third stories are equipped with the SMA shear wall was found to be 290% more ductile, with a greater response modification factor compared to the unequipped frame.

• Smart Structures and Systems
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• v.4 no.2
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• pp.137-152
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• 2008

The work presented in this paper includes material characterisation and an investigation of suitability in seismic dampers for two commercially available NiTi-alloys, along with a numerical analysis of a new damper system employing composite NiTi-wires. Numerical simulations of the new damper system are conducted, using Brinson's one-dimensional constitutive model for shape memory alloys, with emphasis on the system's energy dissipation capabilities. The two alloys tested showed some unwanted residual strain at temperatures higher than $A_f$, possibly due to stress concentrations near inclusions in the material. These findings show that the alloys are not ideal, but may be employed in a seismic damper if precautions are made. The numerical investigations indicate that using composite NiTi-wires in a seismic damper enhances the energy dissipation capabilities for a wider working temperature range.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.87-88
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• 2006

The phase transformation behaviors of Ni-Ti shape memory alloys were investigated through a DSC(Differential Scanning Calorimetry). The annealing temperatures were applied from $600^{\circ}C,\;700^{\circ}C,\;800^{\circ}C,\;and\;900^{\circ}C$ for their effects on the phase transformation behaviors. Based on the results of DSC, phase transformation behaviors of shape memory alloys can be predicted by Liang's phase transformation model or Tanaka's phase transformation model.