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.
Results
Showing 1 to 17 of 17 for “"Dislocation structures"”.
-
Resumptive chains in restrictive relatives, appositives, and dislocation structures
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Linguistics and Philosophy, 1991.
-
Multiscale Experimental Analysis in Plasticity: Linking Dislocation Structures to Continuum Fields
… different complicated mechanisms, and among all, dislocation nucleation and motion are the most dominant ones. Dislocation evolution is known to be a multiscale phenomenon, and has been incorporated to crystal plasticity theories to analyze the size effect in metals for almost a decade ago. …
-
Dislocation structures in materials using grand-canonical minima hopping energy minimization
… of the energetics of accompanying defect structures and, therefore, the accompanying conditions in which they might be expected. Continuum based methods offer one solution for predicting their defect or dislocation onset. However, this implementation does not easily allow for the fine, …
-
Dislocation structures associated with advancing cracks in gallium arsenide and magnesium oxide
… purpose of this research was to determine which dislocation mechanisms were the most important in the fracture processes of semi-brittle materials. In situ TEM deformation experiments were conducted to observe the dislocation structures ahead of propagating cracks in GaAs and MgO. Images of the …
-
A study of dislocation structures in bulk-strained and in situ TEM strained nickel aluminide alloys
… the research work presented in this thesis, the dislocation structures in bulk strained and in situ TEM strained alloys of hypo-stoichiometric Ni$\sb3$Al with and without boron, and hyper-stoichiometric Ni$\sb3$Al with boron have been studied. Bulk samples were deformed in tension to 3% and 9% …
-
Impact of cellular dislocation structures produced by additive manufacturing on neutron irradiation damage evolution in stainless steel 316L
… processes that build three-dimensional structures layer-by-layer from computer-aided-design models. The nuclear industry is exploring additive manufacturing technologies for reactor internal applications in order to enhance performance, reduce economic costs, and shorten production …
-
Characterization of silicon photovoltaic wafers using polarized infrared imaging
… wafers. The measured stress pattern shows that dislocation structures interact with the thermal residual stress, forming slip band structures oriented at 45 degrees to the wafer edges. The measured PE images are then interpreted using a discrete dislocation-based numerical modeling approach that …
-
Mechanisms Operating During Continuous Dynamic Recrystallization in an Aluminum-4magnesium-0.3scandium Alloy
… appears to be the rapid generation of dislocations at sources in grain boundaries and at grain boundary triple points. These dislocations slip across the subgrains and either interact with other dislocations or enter nearby grain boundaries. Low-angle grain boundaries were observed to …
-
The tribological behaviour of aluminium matrix composites
… the formation of a transfer layer and subsurface dislocation structures which are similar to those found in metals subjected to low amplitude fatigue. In contrast to the results for abrasive and sliding wear, the composites show increasingly inferior cavitation and solid particle erosion …
-
High-Resolution Characterization of Micro-Scale Crack Tip Fields in Zirconium
… In Chapter IV, localized geometrically necessary dislocation (GND) densities are estimated using HR-EBSD as an indirect measure of plastic deformation ahead of a microscale crack tip. The advantages of HR-EBSD in measuring fine-scale dislocation structures are also described. Chapter V analyzes …
-
Formation and growth of irradiation-induced defect structures in ceria
… formation and growth of radiation-induced defect structures in oxide fuels. Due to the natural complexity of oxide fuels, which consist of both a metal sublattice and an oxygen sublattice, radiation effects are much more complex in oxides than in metals. As a result, there are many radiation …
-
The strengthening and "softening" of low-carbon structural steels by silicon
… were used to characterize the ferrite-pearlite structures, decarburized layers, random interlamellar spacings in the pearlite constituent, slip line, twin and dislocation structures. The precipitates observed were studied qualitatively with the transmission electron microscope, and microanalysis …
-
Phase field modeling of the defect evolution and failure
… <p>In the first part of the work, a phase field dislocation dynamics (PFDD) approach is introduced, which tracks the evolution of the dislocations in ultrafine and nano grained metals and takes into account the elastic interaction between dislocations, obstacles and the applied resolved shear …
-
Hydrogen effects on the evolution of plastic deformation in polycrystalline nickel: A mechanism for intergranular failure
… specimens. The evolution of deformation microstructures was compared in the presence and absence of hydrogen at different length scales to evaluate changes in mechanical response. Dislocation microstructures were systematically interrogated utilizing the focused ion beam (FIB) liftout …
-
On the plastic deformation behaviour of nickel-based superalloys: low cycle fatigue and stress orientation effects
… in nickel-based superalloys, with a focus on dislocation mechanisms and the effect of microstructure. The two main topics treated are the evolution of the dislocation structure during low cycle fatigue and the effect of loading orientation on the propagation of stacking faults. A series of …
-
An advanced perspective on twin growth in nickel-titanium
… in this thesis. In addition, energetics of dislocation twin boundary interactions in a face centered cubic (fcc) metal (Copper) that contributes to strengthening is investigated. Density Functional Theory based ab initio calculation and Molecular dynamics (MD) correspond to the right length …