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Investigation of Functional Properties of Thin NiTi Filaments for Applications in Smart Structures and Hybrid Textiles
Pilch, Jan ; Dlouhý, Antonín (referee) ; Heczko,, Oleg (referee) ; Pokluda, Jaroslav (advisor)
PhD thesis focuses the field of textile application of modern functional materials, namely metallic shape memory alloys with unique thermomechanical properties deriving from martensitic transformation in solid state. Particularly, it deals with the development of a nonconventional thermomechanical treatment of thin NiTi filaments via Joule heating by electric current and related basic research involving thermomechanical testing and modeling of functional properties of the filaments, investigation of martensitic transformations and deformation processes in NiTi and investigation of the fast recovery and recrystallization processes in metals heated by short pulses of controlled electric power. The method was developed and called FTMT-EC. In contrast to conventional heat treatment of metallic filaments in environmental furnaces, this method allows for precise control of the raise of the filament temperature and filament stress during the fast heating (rate ~50 000 °C/s). As a consequence, it is possible to precisely control the progress of the fast recovery and recrystallization processes in heat treated filaments. In this way it is possible to prepare filaments with desired nanostructured microstructure and related functional properties. A prototype equipment for application of the method for heat treatment of continuous SMA filaments during respooling in textile processing was designed and built. Comparing to the conventional heat treatment of SMA filaments in tubular environmental furnaces, this approach is faster, saves energy and allows for preparation of filaments with special functional properties. International patent application was filed on the method. It is currently utilized in the research and development of smart textiles for medical applications.
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Ternary shape memory alloys powder feedstock fabrication by advanced mechanical alloying
Regináč, Jan ; Moravčík, Igor (referee) ; Čížek, Jan (advisor)
Prášková metalurgie může být použita jako alternativní metoda pro výrobu slitin s tvarovou pamětí s Cu-bází. Tato metoda poskytla lepší výsledky, co se týče celkového složení a velikosti zrn, než tradiční metoda lití. V této práci byl aplikován proces mechanického legování k přeměně směsí základních prášků Cu-Al-Ni na mechanicky legované směsi. Cílem práce bylo nalezení optimálních parametrů pro výrobu nejvhodnějšího práškového prekurzoru určeného k dalšímu zpracování. SEM, EDX a XRD analýzy byly použity pro zjištění účinku změny parametrů na výslednou strukturu a na případnou tvorbu nových fází. Bylo ukázáno, že vysokoenergetické legování je vhodnou metodou pro výrobu takových prekurzorů. Na základě výsledků bylo zjištěno, že tuhý roztok mědi byl formován nezávisle na změně mlecích parametrů. Výsledky dále odhalily, že vysoký energetický vstup ve formě otáček a dlouhých mlecích časů, může způsobovat vznik amorfních fází.
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Observation of twin boundaries in Ni-Mn-Ga alloys
Čech, Jan ; Jan, Vít (referee) ; Zelený, Martin (advisor)
This bachelor’s thesis is focused on observation of twin boundaries in a magnetic shape memory alloy based on Ni2MnGa with 10M martensitic structure. Theoretical part of the thesis describes materials with shape memory effect, their response on mechanical or magnetic loading, phenomenon of twinning, which is closely connected to the shape memory effect, and various levels of twinning. Experimental part studies different types of twin boundaries in monocrystal of alloy Ni49.2Mn30.4Ga20.4 using optical and electron microscopy. The thesis also deals with detection of structural orientations in different twin variants. A holder of samples was designed and constructed for real time observation of twin-boundary movement by optical microscopy. Deformation by pressure shows, that stress necessary for movement of Type II twin boundaries is ~0.2 MPa, whereas it is ~0.6 MPa for movement of Type I.
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Shape Memory Alloys - Modelling of Non-linear Systems with Hysteresis
Vašina, Michal ; Hrabovský, Miroslav (referee) ; Grepl, Robert (referee) ; Žalud, Luděk (advisor)
This work describes a possibility to use a shape memory alloy as a non-traditional actuator in a particular mechatronic system. The practical part of this work is dedicated to the experimental property verification of the chosen shape memory alloy and also to the design and realization of the new type of electrically controlled gabled valve that uses a shape memory alloy as an actuator. This valve is designed as a replacement of the traditional solution and is also integrated into McKibbens pneumatic muscle endcap. There are also results of practical functional verification of the designed gabled valve solution listed here, and the limited condition for its manufacturing and use is stated here. In the theoretical part of this work, firstly, the shape memory alloy and non-linear systems hysteresis type are discussed. Secondly a new particular solution is designed, which is based on a non-linear computational element, defined by goniometric cosine function. Finally, the properties of the designed solution are verified through the simulations and with the use of experimentally gained datas.
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Smart Materials for Medical Applications
Kaplán, Martin ; Hájek, Petr (referee) ; Florian, Zdeněk (advisor)
This thesis describes materials which react to external stimuli. These materials are know as Smart materials. The thesis provides an overview of these materials and their use in the field of medicine. A lot of attentions is paid to Nitinol as the most significant representative of Smart materials. The thesis brings a simulation of using shape memory effect of Nitinol staple for bone fracture fixation. This simulation use the method of finite elements for solving and it is done in ANSYS modeling software. The simulation has only demonstrational purpose.
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Self Adjustable Discharge Valve
Kuruc, Marek ; Maňas, Pavel (referee) ; Technologies,, Jan Jedlička, Emerson Climate (advisor)
This dissertation deals with design of self adjustable discharge valve used in Emerson reciprocating compressors. This work contains research of current state of knowledge, technical analysis of the valve and calculations of basis parameters. Constructional proposal is then presented. Part of the dissertation is manufacturing of prototype and its test. Finally, conclusions for further development are made.
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DSC evaluation of homogenity of Ni-Ti alloys ingots
Kuběnová, Monika ; Zemčík, Ladislav (referee) ; Dlouhý, Antonín (advisor)
Alloy NiTi with nearequiatomic composition of nickel and titan belongs to a group of metal materials with a shape memory effect (Shape memory alloys). NiTi alloys are a guite attractive materials not only as practical shape memory alloys with hight strenght and ductility but also as those exhibiting unique physical properties. The production of these matrerials is complying with chemical composition. Final charakteristics of alloy are influenced by these bounderies and also by mechanical-heat treatment. This work deal with DSC evaluation of homogenity of ingot structure of NiTi alloy containing 50,8 at.% Ni. The alloy was melted in Y2O3 cricible. In the end the results of DSC method are compared to the microstructure of alloy obtained by SEM and TEM methods.
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Memory Materials
Josiek, Robert ; Šesták, Petr (referee) ; Molliková, Eva (advisor)
Currently, shape memory materials are very popular, especially intermetallic compounds NiTi. This alloy is very stable and corrosion resistant, but its production is very difficult because of the high reactivity of titanium. Shape memory effect in this material is dependent on many parameters, such as chemical composition or heat treatment. This bachelor’s thesis explains one-way and two-way memory effect. Another one phenomenon associated with the martensitic transformation, superelasticity, is mentioned, too. The applications of these materials are described in separate chapter of this bachelor’s thesis.
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Variational Methods in Thermomechanics of Solids
Pelech, Petr ; Kružík, Martin (advisor) ; Dondl, Patrick (referee) ; Zeman, Jan (referee)
The thesis is devoted to study of continuum mechanics and thermodynamics and the related mathematical analysis. It consists of four self-contained chapters dealing with different aspects. The first chapter focuses on peridynamics, a non-local theory of continuum mechanics, and its relation to conventional local theory of Cauchy-Green elasticity. Similar compar- isons has been used for proving consistency and for determining some of the material coefficients in peridynamics, provided the material parameters in the local theory are known. In this chapter the formula for the non-local force-flux is computed in terms of the peridynamic interaction, relating the fundamental concepts of these two theories and establishing hence a new connection, not present in the previous works. The second and third chapters are both devoted to Rate-Independent Systems (RIS) and their applications to continuum mechanics. RIS represents a suitable approximation when the internal, viscous, and thermal effects can be neglected. RIS has been proven to be useful in modeling hysteresis, phase transitions in solids, elastoplasticity, damage, or fracture in both small and large strain regimes. In the second chapter the existence of solutions to an evolutionary rate-independ- ent model of Shape Memory Alloys (SMAs) is proven. The model...
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