Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 14 of 14 for “"brittle-to-ductile transition"”.
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Modelling of dislocation-mobility-controlled brittle-to-ductile transition
The phenomenon of brittle-to-ductile transition (BDT) is known to be controlled by the competition between cleavage fracture and dislocation activity at crack tips. The transition can be determined by one of two successive processes--dislocation nucleation and dislocation motion. In this thesis two …
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Experimental investigation of the brittle to ductile transition in fracture of single crystal silicon
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.
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Deformation processed IMC-reinforced metal matrix composites
… investigated. IMCs are "ceramic-like" at ambient to moderate temperatures, and “metallic-like" in their deformation behavior above their brittle-to-ductile transition temperature, thus IMCs create opportunities to create unique in-situ composite microstructures otherwise unattainable using …
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THERMAL AND MECHANICAL PROPERTIES OF NOVEL CARBIDE MATERIALS
… than for cubic tantalum carbide, most likely due to planes of carbon vacancies present in the ζ-Ta<sub>4</sub>C<sub>3-x</sub> crystal structure. The thermal conductivity of (Ta,Hf,Nb,Zr)C was lower than any of its carbide constituents with values ranging from 10.7 W/m•K at room temperature to 39.9 …
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Mechanisms of Deformation and Fracture in TiAl: An Atomistic Simulation Study
… material density, high values of the strength-to-ductility ratio, high elastic moduli, high oxidation resistance, low creep rate, and improved fatigue characteristics. These properties make TiAl alloys very attractive, particularly for structural applications for aerospace and aeronautic …
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Highly Tough, Stiff, and Transparent Poly(Methyl Methacrylate) Composites Incorporating Thermoplastic Elastomer Nanofibrils
… that they must possess both high stiffness and toughness. These two properties, however, are mutually exclusive, meaning that enhancing one typically leads to a reduction in the other. For example, rigid, glassy polymers can be toughened by incorporating soft, rubbery materials, but the …
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Multi-paradigm modeling of mode I&II dynamic fracture mechanisms in single crystal silicon
In addition to its semi-conducting properties, silicon has the ability to be manipulated with high precision at very small length- scales. This property makes it very useful in the design of Nano/Micro-Electromechanical Systems (N/MEMS) and similar technologies. The understanding of fracture of …
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Creep characterization of single crystal silicon in support of the MIT Micro-Engine Project
… the Massachusetts Institute of Technology (MIT) to develop the technology to design and manufacture a micro-gas turbine generator. The objective of the research is to demonstrate a full-scale, functional micro-gas turbine generator by the year 2000. To meet this milestone, the first engine to …
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Thermo-mechanical behavior of silicon at nanoscale — an in situ investigation
… of their deformation mechanism are essential to ensure their reliability and performance. The application of the micro/nano devices are not limited to room temperature as those small devices are often required to operate in high temperature environment. The mechanical properties of micro- and …
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Thermomechanical behavior of single crystal silicon microbeams under bending at elevated temperatures
… used material in these devices. Bulk silicon is brittle at room temperature, but is ductile at 550 ºC - a phenomenon known as brittle-to-ductile transition (BDT). Recently, there has been a speculation in the literature that BDT is size dependent - smaller the size, lower is the BDT temperature. …
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Materials characterization and structural design of ceramic micro turbomachinery
… the technology for micro-gas turbine-generators capable of producing 50 W of electrical power in a package less than one cubic centimeter in volume. The initial goal of this project is to produce a turbine generator and an all-silicon cooled engine by micromachining single crystal silicon. …
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Scale-model investigation of brittle tunnel failure using a true-triaxial device
Brittle instabilities in tunnel excavation have led to severe consequences such as spalling, violent rock ejection or rock burst, and tunnel collapse. Detached rocks from the tunnel boundary not only compromise the structural integrity of tunnels but also pose significant safety risks to personnel …
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Synthesis, microstructure and mechanical properties of bulk ultrafine grained Ti-47Al-2Cr (at%) alloy
… Ti-47Al-2Cr (at%) have been carried out to synthesize bulk ultrafine grained Ti-47Al-2Cr alloy. The Ti/Al/Cr composite powders were produced using high energy mechanical milling of elemental Ti, Al, Cr powders in a retsch planetary mill. The microstructure and mechanical properties of the …
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Mechanics of deformation and fracture of silicon electrodes in high-capacity lithium-ion batteries
… ion batteries, a high energy density system, store energy by insertion of Li ions into solid electrodes. Silicon is one of the most promising electrode materials for high performance lithium ion batteries, since it has a specific capacity of ~10 times higher than conventional graphite …