Papers by Keyword: Shape Memory Alloy (SMA)

Abstract: This paper presents a feasibility study on a self-centering steel column foot equipped with innovative shape memory alloy (SMA) ring springs. The ring spring system includes a series of SMA outer rings and high-strength alloy inner rings stacked in alternation with mating taper faces, and the system is used in conjunction with high-strength bolts in a typical extended end-plate connection to achieve favorable self-centering and energy dissipation performances while ensuring ease of construction. An experimental investigation was first conducted looking into the basic mechanical performance of individual SMA ring springs under cyclic loading. Driven by the superelastic behavior of SMA, excellent self-centering ability with satisfactory energy dissipation is exhibited. Subsequently, a further experimental study on a proof-of-concept column foot specimen is conducted, where the key properties, including ductility, self-centering ability, and energy dissipation capability, are discussed in detail in this paper.

Abstract: Shape memory alloys with their phase transformation properties; have been broadly implemented in smart structures. In this study, a functional design is presented where two wires actuate antagonistically to achieve motion in bending. Effect of heat treatment parameters on the actuator materials is investigated. For this purpose, a novel experimental test bench appropriate for characterizing a smart joint is presented, and joint performance including actuation force and cyclic behavior are demonstrated. Accordingly, a smart joint configuration capable of 60 degrees bending with a repeatability of 50 cycles is developed.

Abstract: Shape memory composites (SMCs) combined with shape memory polymer (SMP) and shape memory alloy (SMA) having excellent mechanical properties and shape memory properties are considered to be ideal materials used in smart adaptive structure. In order to broaden the application of SMCs, a temperature controlled telescopic boom was designed and prepared. The design criteria indicated that temperature sequence was as follow: T _{room temperature}< T_g < A_s, and the deformation temperature was better around T_g+30°C. And the TiNi wires should be displayed in the longitudinal axe and outer race of the boom, and the minimum curved diameter of innermost layer could be calculated by. The recover behavior of the sample corresponded to the design, and the recover process could be repeated more than 10 times.

Abstract: The characteristics of isothermal deformation behavior of Ti-50.8%Ni shape memory alloys were investigated by thermal simulation tests, which were performed on Gleeble-3500 thermal simulation machine. The range of deformation temperatures was 800°C to 1050°C and that of strain rates was 0.01s^-1 to 10s^-1. The stress-true strain curves were corrected by considering deformation-heating and friction. The results show that the flow stress increases with the decrease of deformation temperatures or the increase of strain rates. The constitutive relationship of hot deformation was established on the basis of the Arrhenius equation and the average activation energy of 182 KJ/mol was obtained.

Abstract: Shape Memory Alloy (SMA) is a material with the ability to return to its original position, when being subjected to an appropriate thermo mechanical procedure. SMA find very wide applications in various facets of robotic and bio medical engineering. In this paper, review on ankle/foot diseases and the effective use of heat treated SMA was carried out. The manufacturing industry normally uses a range of between 200°C to 400°C to shape any biomedical product which has been used as the benchmark temperature throughout this research. The results suggested that annealing of 200°C produced the best suited for generating substantial displacement which can promote early rehabilitation of ankle/foot.

Abstract: In this paper, the analyses results on the behavior of Shape Memory Alloy (SMA) in Medical application were carried out. SMA materials are known by their aptitude to recover its original form when undergone suitable thermal changes. SMA is widely used in robotics, automotive, aerospace and it can be a potential application in biomedical engineering due to its low cost, high corrosion resistance and can be easily integrated with human applications. Stewart platform with two different upper platform diameters of 150 mm and 300 mm were designed, fabricated and used as experimental test-rig. Inverse kinematic calculations were carried out to identify a maximum deflection of Stewart platform that can promote continuous passive motion (CPM). The 150 mm base diameter Stewart platform is found to be the suited for generating substantial displacement between ankle and foot. The mechanical changes induced by the heat could be used as a property in manufacturing of rehabilitation device for foot and ankle.

Abstract: Functional recovery of upper limb after stroke is crucial to restore the ability to perform activities of daily living (ADL). This paper presents a robotic rehabilitation approach based on repetitive exercise aimed to help stroke survivors relearn the skills of finger flexion and extension at the comfort of their home. The finger rehabilitation device deploys Shape Memory Alloy (SMA) wires as an actuation approach to deliver three degrees of freedom per finger module. The advantages and challenges of using SMA wires rather than conventional actuators are discussed. A prototype of the finger rehabilitation device was built using PLA material and experiments have been conducted for the purposes of feasibility study. Tests conducted on the wires suggest that it has to have sufficient weight and also has to be stretching at high temperature rather than room temperature in order to have an optimum range of recovery.

Abstract: This paper presents the processing of Nickel Titanium (NiTi) alloy from elemental powders of Nickel and Titanium by conventional powder metallurgy process. Two batches of feedstock containing 2 different formulations (1) Ti-50.4at% Ni and (2) Ti-50.8at% Ni were prepared. The feedstocks for each composition were warm-pressed and subsequently sintered in vacuum at 1150°C. Based on the XRD result, it clearly showed that the conventional sintering following warm-press method is promising in producing greater amount of the predominant NiTi (B2) phase and a minor fraction of martensitic NiTi (B19’) phase. The reversible phase transformation and the microstructure of the sintered samples have also been observed and discussed.

Abstract: The aim of this work was to describe the dependence of microstructure of NiTi shape memory alloy on the conditions of powder metallurgy processing route. The technology consisted of blending of elemental Ni and Ti powders, uniaxial cold pressing and reactive sintering. The effects of reactive sintering temperature, heating rate, holding duration and particle size were determined. The proposed technology can be used as the alternative production route of NiTi to minimize the contamination of the alloy.

Abstract: The main fields of the practical application of Ti-Ni-based alloys, with shape memory and superelasticity effects, in engineering and medicine, have been identified in the past decade. There are temperature-sensitive elements for the actuators, damping devices, fasteners, medical instruments and implants (correctors, clamps, stents), for trauma, spine, dentistry, soft tissues and vessels. The development of science and high technologies to produce semi-finished methods (thin-walled tubes, tapes and thin wire), as well as processing methods (laser cutting and welding) of Ti-Ni-based shape memory alloys (SMA) over the last 10 years has contributed to the creation and implementation into practice of more complicated and advanced devices, based on solid and porous shape memory materials. New technologies require not only the creation of fundamentally new shape-memory devices, but also, more importantly, the achievement of the highest possible functional properties (FP) of the SMA, by creating an optimal type of structure by thermomechanical treatment. Techniques for the regulation of FP are different for Ti-Ni SMA of different compositions. For the non-ageing equiatomic and near-equiatomic Ti-Ni SMA, the basic method of FP control is thermomechanical treatment (ТМT), including severe plastic deformation (SPD), forming various structures: from a well-developed recovered and polygonized dislocation substructure to a nanocrystalline structure. In the framework of the scientific direction, fundamental and applied research in the field of SMA thermomechanical treatment (TMT) has been carried out since 1977, by the Shape Memory Alloys Research Group of the National University of Science and Technology MISIS.The present review provides a brief description of the devices running on the shape-memory effect and superelasticity, developed jointly by NUST "MISIS" and various companies: Globetek 2000 Ltd (Melbourne, Australia); Semashko Central Clinical Hospital of Ministry of Railway Communications; Closed Joint-Stock Company ARMGAS-NT; Scientific-production Enterprise AVTOMATPROM (Moscow, Russia), et al. In addition, it presents the analysis of medical problems that can be solved using data devices, including work items of thermomechanically treated Ti-Ni SMA.