Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Fizik Anabilim Dalı, 2007. / Bibliyografya var.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 70).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Gall, Ken; Committee Chair: May, Gary S; Committee Member: Brand, Oliver; Committee Member: Degertekin, F Levent; Committee Member: Milor, Linda S. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Η διπλωματική αυτή εργασία πραγματεύεται τη μελέτη της μεθόδου Ilizarov καθώς και το σχεδιασμό, την κατασκευή και τον έλεγχο ενός ισοδύναμου με ένα βαθμό ελευθερίας του πλαισίου Taylor στοιχείου δράσης, του οποίου η ενεργοποίηση επιτυγχάνεται με τη χρήση έξυπνων υλικών και συγκεκριμένα μεταλλικών κραμάτων με μνήμη της μορφής (SMA). Πρωτεύον μέλημά μας αποτελεί η μελέτη των γενικών χαρακτηριστικών της εξωτερικής σταθεροποίησης και η κατανόηση της μεθόδου Ilizarov με τη χρήση του πλαισίου Taylor (Κεφάλαιο 2). Ακολούθως, κάνουμε λόγο για τους ενεργοποιητές που χρησιμοποιούνται στη διάταξή μας, αναλύοντας εκτενώς τις ιδιότητες των κραμάτων με μνήμη της μορφής και πιο συγκεκριμένα των κραμάτων NiTi (Κεφάλαιο 3). Λαμβάνοντας υπόψη όλα τα προηγούμενα, είμαστε σε θέση να προχωρήσουμε στην υλοποίηση μίας κατασκευής που προσομοιώνει ένα βαθμό ελευθερίας του πλαισίου Taylor και η οποία ενεργοποιείται από τα παραπάνω έξυπνα υλικά. Πειράματα ανοικτού και κλειστού βρόχου ελέγχου της διάταξης εκτελούνται εν συνεχεία με τη βοήθεια ηλεκτρονικού υπολογιστή (Κεφάλαιο 4). Τέλος, παρουσιάζονται τα συμπεράσματα και οι προοπτικές της εν λόγω εργασίας (Κεφάλαιο 5). / The present diplomatic work consists of the study of Ilizarov method as well as the planning, the construction and the control of one out of six degrees of freedom of a Taylor platform. The activation of the experimental provision is achieved with the use of intelligent material and concretely shape memory alloys (SMA). Our first concern is the study of the general characteristics of the exterior stabilization of the bones and the comprehension of Ilizarov method using the Taylor platform (Chapter 2). Followingly, we deal with the activators that are used in our provision, analyzing extensively the attributes of shape memory alloys and more concretely the alloys NiTi (Chapter 3). Taking into consideration all the above, we are in position to advance in the concretisation of a structure that simulates one degree of freedom of the Taylor platform and is activated by the SMA. We executed control experiments using LabView in an open and closed loop in order to test the provision (Chapter 4). Finally, are presented the conclusions and the prospects of this project (Chapter 5.)

Made available in DSpace on 2015-05-08T14:59:55Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 8849589 bytes, checksum: 337394414de1a3c9ab9c071e9c18f59b (MD5) Previous issue date: 2014-02-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The shape memory alloy, more specifically constituted of CuAlBe, have played an important role in the manufacture of electromechanical components, especially when worked requests from thermal and/or applied stresses. At first, this present research work, were obtained, by casting the gas, samples of alloys Cu-11.8%Al-0.60%Be; Cu-11.8%Al-0.55%Be; Cu-11.8%Al-0.55%Be-0.50%Nb-0.27%Ni (wt%). Sequentially, quenched to half of them, with the intention of doing them acquire the shape memory effect. In a third moment, said samples passed assays DSCs, aiming raise the temperature curves of phase transformation (austenite: Ai/Af and martensite: Mi/Mf). The main study, performed during machining by turning dry, using a piezoelectric dynamometer, were defined the cutting forces of samples tempered and not tempered. In compliance with the track methodology, were applied five replicates, with four levels of cutting speed for each of the samples tested. The signals from the dynamometer were processed in LabVIEW and further processed in by a program done on MatLAB. Secondary assays were also performed soon after machining by turning dry. In the first, by means of a K-type thermocouple, temperatures of machining were measured along the stride; on the second, by assay of circularity, it was verified if there was or no retention of the martensite in the samples of shape memory alloys. It was found that the percentage of beryllium and nickel present in the alloys investigated, as well as the introduction of niobium as a grain refiner were decisive for achieving the results / As ligas com memória de forma, mais especificamente as constituídas de CuAlBe, têm desempenhado um papel importante na fabricação de componentes eletromecânicos, sobretudo quando trabalhados a partir de solicitações térmicas e/ou tensões aplicadas. A princípio, neste presente trabalho de pesquisa, foram obtidas, por fundição a gás, amostras das ligas Cu-11,8%Al-0,60%Be; Cu-11,8%Al-0,55%Be; Cu-11,8%Al-0,55%Be-0,50%Nb-0,27%Ni (% em peso). Sequencialmente, temperou-se a metade delas, com o intuito de fazê-las adquirir o efeito memória de forma. Num terceiro momento, as referidas amostras passaram por ensaios de DSCs, visando levantar as curvas de temperatura de transformação de fases (da austenita: Ai/Af e da martensita: Mi/Mf). No ensaio principal, realizado durante a usinagem por torneamento a seco, por meio de um dinamômetro piezoelétrico, definiram-se as forças de corte das amostras temperadas e não temperadas. Dando cumprimento à trilha metodológica, foram aplicadas cinco réplicas, com quatro níveis de velocidade de corte para cada uma das amostras ensaiadas. Os sinais oriundos do dinamômetro foram processados no LabVIEW e posteriormente tratados por uma programação feita em MatLAB. Ensaios secundários também foram realizados logo após a usinagem por torneamento a seco. No primeiro, por meio de um termopar tipo K, foram medidas as temperaturas de usinagem ao longo da passada; no segundo, por ensaio de circularidade, foi verificado se ocorreu ou não a retenção da martensita nas amostras das ligas com memória de forma. Constatou-se que a percentagem de berílio e de níquel presente nas ligas investigadas, bem como a introdução do nióbio como refinador de grãos foram decisivos para o alcance dos resultados obtidos

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2010. / Hybrid polymeric composites (HPC) are widely used for the design of aerospace, automobile and civil engineering structures. One of the major challenges posed by these materials and structures is their brittle nature. When subjected to impact and dynamic loads, the polymeric composite structures undergo micro cracking. The cracks coalesce, propagate and can lead to catastrophic failure of the material and structures. In this thesis, an intelligent hybrid polymeric composite (IHPC) beam with healing ability was developed and tested. The IHPC beam developed consisted of a 3% prestrained 1mm diameter Ni-Ti shape memory alloy (SMA) wire actuator embedded in the polymeric host matrix. The function of the embedded Ni-Ti shape memory alloy was to enhance intelligence and healing ability to the IHPC beam. Upon electric current resistance heating, the Ni-Ti SMA actuator responds by contracting as a result of detwinned martensite → austenite phase transformation. Contraction of the SMA in the IHPC beam was utilized to stiffen and enhance healing by retarding crack growth and recovery of the strain induced in the loaded IHPC beam. This can result to increase of the flexural stiffness EI (defined as the product of the Young’s Modulus E of the material and the moment of inertia I of the geometry of the beam) and mode I fracture stress intensity factor KIC of the IHPC beam. One (1) mm diameter Ni-Ti SMA wire was used in the experimental work in this thesis. The wire was cut into 35 pieces, 200 mm long each. Ni-Ti SMA wires were heated in the furnace to a temperature of 250ºC for ten (10) hours then were left to cool in the ambient air. The heat treatment was aimed to release any residual stress and to stabilize the austenite start (AS) and austenite finish (Af) transformation temperatures of the Ni-Ti SMA. After heat treatment, the Ni-Ti SMA wires were prestrained by 3% (based on a gauge length of 150mm) on a tensile testing machine. Prestraining of the Ni-Ti SMA wires was aimed to induce detwinned martensite volume fraction in them hence increasing the transformation strain and recovery force of the Ni-Ti SMA actuator. Intelligent hybrid polymeric composite (IHPC) beams and polymeric virgin (PV) beams, all of dimensions 150mmx25mmx10mm were manufactured by casting 60D polyurethane thermosetting epoxy resin in a silicon mould. transformation strain and recovery force of the Ni-Ti SMA actuator.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2011 / Smart (SMA-Shape Memory Alloy) Technology continues to advance rapidly as engineers move closer to and understand better the industrial and commercial needs for SMA. As a matter of fact, all types of products, which exercise some type of control over their function, are rapidly making their way into the marketplace [36] Nonetheless, nowhere has been evidence in the development of a SMA impeller. Unlike traditional impellers with no control over their function and sometimes fixed angle of attack, this paper demonstrates numerical investigations using analytical algorithms (Matrix laboratory programming and excel spread sheet) and advanced computer simulation package, Engineering Fluid dynamics (EFD) into the feasibility of using a smart impeller to study the performance of a pumping system and the best angle of attack for a Shape Memory Impeller. Primarily, Bench mark data and dimensions are obtained from a standard centrifugal pump run on a FM21 demonstration unit. Using the same standard centrifugal pump, and keeping all other dimensions the same but altering the angle of attack, EFD simulations where made. From analytical algorithm and EFD comparison, it was evident that the best angle of attack is 12 degree at the outlet angle with respect to the inlet angle. From EFD results, it is palpable that, by increasing the angle of attack from 35 degree to 45 degree at the outlet there will be huge increase in flow rate by 63.47% There is also a slight decrease in the impeller Torque from 35 degrees to 42 degrees by 0.72%. It is economically feasible to work at an outlet angle of 42 degrees due to increase in efficiency of 62.1% and a drop in torque of 0.72% by varying the outlet angle from 35 degrees to 42 degree. Understanding how critical actuator design is, it should be suggested that any shape memory impeller should never be used in critical components without a prior history of thermal and mechanical loading. Therefore, a NiTi impeller constitutive model can be designed, with impeller blades made from NiTi plates, trained to remember its best angle of attack (Martensitic phase). NiTi shape memory metal alloy (plates-blades) can exist in a two different temperature-dependent crystal structures (phases) called martensite [9](lower temperature-normal pumping condition) and austenite [9] (higher temperature or parent phase-trained best angle of attack.)

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2015. / This dissertation addresses the development and the testing of a simulation tool to be used to predict the behaviour of smart material/structures. Along with the development of the simulation tool, a new form of the model describing the behaviour of shape-memory alloy was developed and implemented. The proposed model was developed based on the existing cosine model, conventionally used in literature, but it uses hyperbolic tangent functions. The hyperbolic tangent function was chosen so as to allow the simulation of any range of temperatures. Experiments were performed to obtain the parameters to be used in the simulation and to validate the numerical results. Two different simulations were performed: a one dimensional FEA analysis with a two dimensional orientation (NiTi SMA wire simulation) and a three dimensional FEA analysis (NiTi SMA plate) [Msomi and Oliver, 2015]. Alongside the FEA analysis, two experiments were performed with the purpose of obtaining the material parameters to be used in FEA analysis and to compare the FEA results to the experimental results. / Airbus Company

Squat reinforced concrete shear walls are stiff structural elements incorporated in buildings and other structures and are capable of resisting large seismic demands. However, when not properly designed, they are prone to shear-related brittle failure. To improve the seismic behaviour of these structural elements, a retrofitting bracing system incorporating superelastic Shape Memory Alloys (SMAs) was developed. Superelastic Shape Memory Alloys (SMAs) are smart materials with the ability to sustain and recover large pseudo-plastic deformations while dissipating energy. The SMA bracing system consists of tension-only SMA links coupled with rigid steel elements. The SMA links were designed to sustain and recover the elongation experienced by the bracing system, while the steel elements were designed to sustain negligible elastic elongations. The SMA bracing system was installed on third-scale, 2000 mm × 2000 mm, shear walls, which were tested to failure under incremental reverse cyclic loading. The experimental results demonstrated that the tension-only SMA braces improve the seismic response of squat reinforced concrete walls. The retrofitted walls experienced higher strength, greater energy dissipation, and less permanent deformation. The re-centering properties of the SMA contributed to the reduction of pinching in the hysteretic response due mainly to the clamping action of the SMA bracings while recovering their original length. The walls were numerically simulated with the nonlinear finite element program VecTor2. The numerical simulations accurately captured the hysteretic response of both the original and the retrofitted walls. A parametric study was conducted to assess the effect of axial loading and size of the SMA braces.

Les Transformation Martensitiques (TM) sont des transitions du premier ordre entre des phases cristallines qui caractérisent une classe intéressante de matériaux intelligents, les Alliages à Mémoire de Forme (AMF). Ces alliages métalliques furent découverts dans les années 1930 environ. Ils sont surtout intéressants car ils combinent deux effets particuliers : l'effet de mémoire de forme et la pseudo-élasticité. L'effet mémoire de forme consiste à mémoriser une configuration particulière et la retrouver après des cycles thermiques ou mécaniques. La Pseudo-Elasticité consiste à rejoindre des niveaux de déformation très grands qui sont, en général, plus typiques du caoutchouc que des métaux. Dans cette thèse, nous avons traité la caractérisation des transformations martensitiques en analysant des points de vue différents. La compréhension du fonctionnement des AMFs est fondamentale pour plusieurs types d'applications industrielles. Elle constitue encore un domaine de recherche très ouvert. (...) / This thesis deals with the characterization of Martensitic Transformations (MT) that are first order phase transitions among different solid states with different crystalline structures. These transitions are at the basis of the behavior of a class of smart materials, called Shape Memory Alloys (SMA). This work combines an experimental study of a mechanically-induced martensitic transformation in a Cu-Al-Be single crystal and a macroscopic model for the reproduction of permanent effects in cyclic temperature-induced and stress-induced transitions. From the experimental point of view, the novelties are in the device that has been built and used for the test and in the full-field measurement technique at the basis of the data treatment. The especially designed gravity-based device allows for a uni-axial and uni-directional tensile test with slow loading rates. Simultaneously, the full-field measurement technique, known as grid method, provides high-resolution two-dimensional strain maps during all the transformation. With all the data collected during the test, we characterize for the first time the two-dimensional strain intermittency in a number of ways, showing heavy-tailed distributions for the strain avalanching over almost six decades of magnitude. In parallel, we develop a macroscopic mathematical model for the description of fatigue and permanent effects in several kinds of martensitic transformations. We show an easy way to calibrate the model parameters in the simple one-dimensional case. Moreover, we compare the numerical results with experimental data for different tests and specimens and obtain a good qualitative agreement.