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Showing 1 to 20 of 130 for “"Shape Memory Alloys"”.
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Orthopaedic applications of ferromagnetic shape memory alloys
Ferromagnetic shape memory alloys (FSMAs) are a new class of magnetic field-actuated active materials with no current commercial applications. By applying a magnetic field of around 0.4 T, they can exert a stress of approximately 1.5 MPa, exhibiting a strain of up to 6%. This thesis evaluates their …
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Shape Memory Alloys for small scale actuation
Shape Memory Alloys (SMAs), materials that can undergo a fully recoverable strain change due to a thermal cycle, and which can be produced in a form that is superelastic are only utilized limitedly. In this thesis, I investigated the relationship between the material properties of shape memory …
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The constitutive modeling of shape memory alloys
… thermomechanical constitutive model for shape memory alloys based on basic concepts of thermodynamics and phase transformation kinetics. Compared with other developed constitutive relations, this thermomechanical constitutive relation not only reflects the physical essence of shape memory …
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Transmission Electron Microscopy Studies In Shape Memory Alloys
… with strain recovery that results in the shape memory effect. Ternary elemental additions such as Fe can additionally introduce an intermediate rhombohedral (R) phase between the cubic and monoclinic phase transformation. This work was initiated with the broad objective of connecting the …
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Thermodynamic modeling of martensitic transformations in shape memory alloys.
The unusual properties of shape memory alloys (SMAs) are due to solid-to-solid martensitic transformations (MTs) which correspond to a lattice level instability of the crystal structure. Currently, there exists a shortage of material models that can capture the details of lattice level MTs …
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Instrumented Nanoindentation Studies Of Deformation In Shape Memory Alloys
Near equi-atomic nickel titanium (NiTi) shape memory alloys (SMAs) are a class of materials characterized by their unique deformation behavior. In these alloys, deformation mechanisms such as mechanical twinning and stress induced phase transformation between a high symmetry phase (austenite) and a …
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Active fibre-reinforced composites with embedded shape memory alloys
… active fibre-reinforced composites with embedded shape memory alloy wires. The structural application of active materials allows to develop adaptive structures which actively respond to changes in the environment, such as morphing structures, self-healing structures and power harvesting devices. …
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Constitutive modeling of Cu-Al-Ni shape memory alloys
Certain alloys can exist in multiple phases, which, in the context of solids, essentially mean multiple crystallographic structures. For example, at certain compositions, a Cu-Al-Ni alloy can exist as a cubic lattice (austenite), an orthorhombic lattice ([beta]'1-martensite) or a monoclinic lattice …
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Designing mechanisms with shape memory alloys and permanent magnets
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.
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Adaptive prestressing system for concrete structures using shape memory alloys
Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2025-12-01
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Computational modeling of size-dependent superelasticity in shape memory alloys
The superelastic effect in shape memory alloys (SMAs) is attributed to the stress-induced reversible austenitic-martensitic phase transformations. It is characterized by the development of significant strains which are fully recoverable upon unloading, and also characterized by the …
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Exploring crystallographic compatibility in polycrystalline Cu-based shape-memory alloys
Shape-memory alloys (SMAs) are a class of materials that can recover from apparent permanent strain (on the order of 5%) due to a solid-to-solid phase transformation. It has been recently suggested that SMAs satisfying a set of so-called cofactor conditions possess perfect interface compatibility …
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Strain rate effects on the behavior of shape memory alloys
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.
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Heat Engine Driven by Shape Memory Alloys: Prototyping and Design
This work presents a novel approach to arranging shape memory alloy (SMA) wires into a functional heat engine. Significant contributions include the design itself, a preliminary analytical model and the realization of a research prototype; thereby, laying a foundation from which to base refinements …
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Smart Surgical Needle Actuated by Shape Memory Alloys for Percutaneous Procedures
… recently where actuation forces provided by shape memory alloys (SMAs) are utilized to assist the maneuverability and accuracy of surgical needles. This work also aims to introduce a novel needle insertion simulation to predict the deflection of a bevel tip needle inside the tissue. …
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Aging Effects in Copper-Zinc-Aluminium Shape Memory Alloys (Martensite, Bainite)
… the beta phase and martensitic state of Cu-Zn-Al alloys causes deterioration and instability of shape memory properties, even at moderate temperatures. These aging effects have been studied by electrical resistivity measurements and bend tests. The corresponding changes in microstructure were …
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Acoustic assisted actuation of Ni-Mn-Ga ferromagnetic shape memory alloys
Ferromagnetic shape memory alloys (FSMA) have been shown in recent work to exhibit large magnetic field induced strains. The material generally requires a large threshold field (of order 3-4 kOe) to initiate the strain. Thus, the power requirements are large and actuators based on these materials …
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Dynamic actuation properties of Ni-Mn-Ga ferromagnetic shape memory alloys
… least 500 Hz in Ni48.5Mn29.5Ga21 ferromagnetic shape memory alloys (FMSAs) is achieved. Hardware was designed and constructed to measure frequency bandwidth, magnetic-field-induced strain, stress and magnetization driven from an applied magnetic field. The bandwidth in this investigation was …
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Diffraction Studies Of Deformation In Shape Memory Alloys And Selected Engineering Components
Deformation phenomena in shape memory alloys involve stress-, temperature-induced phase transformations and crystallographic variant conversion or reorientation, equivalent to a twinning operation. In near equiatomic NiTi, Ti rich compositions can exist near room temperature as a monoclinic B19' …
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Experimental testing and constitutive modeling of concrete confined with shape memory alloys
… and Shin (2008) first proposed the idea of using shape memory alloy (SMA) spirals to apply active confinement to concrete prior to loading without the need for mechanical prestressing and some research has been done on this topic in the past few years. Results so far show the promise of this new …
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