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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Effect of Crystallographic Orientation and Thermo-mechanical Loading Conditions on the Phase Transformation Characteristics of Ferromagnetic Shape Memory Alloys

Zhu, Ruixian 2009 December 1900 (has links)
The effects of crystallographic orientation, temperature and heat treatment on superelastic response of Ni45Mn36.5Co5In13.5 single crystals were investigated. Superelastic experiments with and without various magnetic field were conducted under compression on a custom built magneto-thermo-mechanical test setup. Magnetostress, which is the difference in critical stress levels for the martensitic transformation with and without magnetic field, was determined as a function of crystallographic orientation, heat treatment and temperature parameters. Magnetostress of [111] crystals was observed to be much higher than that of [001] crystals with same heat treatment. Water quenched samples have the highest magnetostress among other samples with the same orientation that were oil quenched and furnace cooled. Crystal structure and atomic ordering of the samples were examined using Synchrotron High-Energy X-Ray Diffraction to rationalize observed differences. Magnetostress levels were also traced at various temperatures. A Quantum Design superconducting quantum interference device (SQUID) was utilized to examine the magnetic properties of the material. The difference in saturation magnetization at various temperatures was analyzed to explain the temperature effect on magnetostress. Calculations based on the energy conversion from available magnetic energy to mechanical work output were used to predict the magnetic field dependence of magnetostress, which provides a guideline in material selection for the reversible magnetic field induced martensitic phase transformation. Isothermal superelastic response and load-biased shape memory response of Co48Ni33Al29 single crystals were determined as a function of temperature and stress, respectively. The aim of the work is to provide a new direction to understand the anomaly of transformation strain and hysteresis for ferromagnetic shape memory alloys. Thermo-mechanical behavior of Co48Ni33Al29 single crystal was determined by a custom built thermo-mechanical compression setup based on an electromechanical test frame made by MTS. Transformation strain was observed to decrease with increasing applied stress in isothermal tests or increasing temperature in superelastic experiments. The variation in the lattice constant in martensite and austenite was verified to account for such a trend. It was also discovered that both thermal and stress hysteresis decreased with increasing applied stress and temperature, respectively. Multiple factors may be responsible for the phenomenon, including the increase of dislocation, the compatibility between martensite and austenite phase.
2

Transformation surfaces and normality for random and textured pseudoelastic shape memory alloys

Aleong, Douglas Kent 05 1900 (has links)
No description available.
3

Distributed control of a segmented and shape memory alloy actuated biologically inspired robot

Schubert, Oliver John. January 2005 (has links) (PDF)
Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Hongwei Gao. Includes bibliographical references (leaves 63-66).
4

An experimental study on cyclic behavior of extended end-plate connections equipped with shape memory alloy bolts

Xie, Lang Kun January 2017 (has links)
University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering
5

Haemocompatibility and characterisation of modified nickel titanium surfaces

Armitage, David A. January 1998 (has links)
No description available.
6

Cyclic behavior of steel beam-column connections with shape memory alloy connecting elements

Ocel, Justin M. 05 1900 (has links)
No description available.
7

Low temperature NiTiFe shape memory alloys actuator engineering and investigation of deformation mechanisms using in situ neutron diffraction at Los Alamos National Laboratory /

Krishnan, Vinu Bala. January 2007 (has links)
Thesis (Ph.D.)--University of Central Florida, 2007. / Adviser: Raj Vaidyanathan. Includes bibliographical references (p. 115-120). Also available in print.
8

Prestressing of simply supported concrete beam with nitinol shape memory alloy /

Kotamala, Sreenath. January 2004 (has links)
Thesis (M.S.V.)--University of Toledo, 2004. / Typescript. "A thesis [submitted] as partial fulfillment of the requirements of the Master of Science degree in Civil Engineering." Includes bibliographical references (leaves 63-64).
9

Factors affecting reversible shape-memory

Friend, C. M. January 1985 (has links)
In the last twenty years Reversible Shape-Memory (RSM) alloys have become the source of considerable technological interest as a result of their ability to generate spontaneous and reversible changes of shape on thermal cycling. This has led to the development of a range of reversible shape-memory devices for thermostatic sensing applications. In these devices the alloy is subjected to several thousand shape-memory cycles and the stability of the reversible shape-memory is therefore an important alloy property. Data on the effect of shape-memory cycling on the long-term stability of the reversible shape-memory, however, is extremely limited. The present work, conducted to fill this gap, has shown that there is an inherent instability in the reversible shape-memory, with changes in the operating temperatures and cumulative reductions in the maximum shape-strain output of actuators on long-term thermal cycling under conditions simulating real devices. Extensive investigation has shown that these instabilities result from a number of sources, ageing of the shape-memory martensites and most importantly from morphological disruptions in the "trained" martensites caused by two-stage stress-induced transformation and due to the build-up of transformation-induced dislocation debris. This shape-strain degradation has also been successfully modelled by means of a simple two-stage stress-induced martensitic transformation model.
10

The development of an 'active' surface using Shape Memory Alloys

Saal, Sheldon Chrislee January 2006 (has links)
Thesis (MTech (Technology : Mechanical Engineering))--Cape Peninsula University of Technology, 2006 / Recent years have witnessed a tremendous growth and significant advances in "smart" composites and "smart" composite structures. These smart composites integrate active elements such as sensors and actuators into a host structure to create improved or new functionalities through a clever choice of the active elements and/or a proper design of the structure. Such composites are able to sense a change in the environment and make a useful response by using an external feedback control system. Depending on their applications. smart composites usually make use of either the joint properties of the structure or the properties of the individual elements within the composites. The accumulation in the understanding of materials science and the rapid developments in computational capabilities have provided an even wider framework for the implementation of multi-functionality in composites and make "smart" composites "intelligent". This thesis is a contribution towards the global endeavour to innovate using smart structures to enhance our everyday lives. One of the phenomena of shape memory alloys. the shape memory effect was put to use in the development of an active surface. Here the pre-stressed shape memory alloy (in its de-twinned martensitic state) is surrounded or embedded in a non-SMA matrix material. This active surface can be used in a variety of applications that requires active shape control to change the shape of a flexible structure member such as a submarine stem, aerospace control surfaces and aircraft wings. An experimental protocol was developed to treat or stabilize shape memory alloys that are used as actuators within composite structures. Shape memory alloys exhibit complex behaviour during their quasi-plastic material response. The complex behaviour includes variability in yield values and the transformation region/range.

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