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Full-Text Articles in Engineering
Physics-Based Crystal Plasticity Model For Predicting Microstructure Evolution And Dislocation Densities, Juyoung Jeong
Physics-Based Crystal Plasticity Model For Predicting Microstructure Evolution And Dislocation Densities, Juyoung Jeong
LSU Doctoral Dissertations
This work presents three different studies investigating plastic deformation mechanisms in metals and alloys using crystal plasticity finite element (CPFE) modeling. The first study presents a new nonlocal crystal plasticity model for face-centered cubic single crystals under heterogeneous inelastic deformation. The model incorporates generalized constitutive relations that incorporate the thermally activated and drag mechanisms to cover different kinetics of viscoplastic flow in metals and describes the plastic flow and yielding of single-crystals using dislocation densities. The model is compared to micropillar compression experiments for copper single crystals and clarifies the complex microstructural evolution of dislocation densities in metals. The second …
Experimental Evaluation Of How Mineralogy And Microstructure Impact Micro-Geomechanics Of Shale Rocks, Hui Du
LSU Doctoral Dissertations
Shales play an essential role in petroleum exploration and production because they can occur either as unconventional reservoir rocks for hydrocarbon extraction via hydraulic fracturing or as caprocks for conventional reservoirs and subsurface gas/ waste storage. For both extraction and storage applications, the success rate is directly depending on the rigorous candidate selection. Conventional rock characterization techniques normally measure rock properties by seismic/logging at the reservoir scale, and on drilled/outcrop cores at the core scale. However, shales are highly heterogeneous in composition, containing a large number of reactive minerals in micro/nanoscale with significantly different properties. The structural features and properties …
Synthesis And Characterization Of Geopolymers For Infrastructural Applications, Jian He
Synthesis And Characterization Of Geopolymers For Infrastructural Applications, Jian He
LSU Doctoral Dissertations
In this study, the synthesis process, composition, and microstructure as well as mechanical properties of geopolymers generated by 3 different kinds of raw materials (i.e., metakaolin, mixture of red mud and fly ash, mixture of red mud and rice husk ash) was explored. For geopolymers from identical raw materials, variable parameters involved in the synthesis were examined to investigate the extent and degree of geopolymerization. Uniaxial compression testing was used to examine the mechanical properties (i.e. compressive strength, stiffness, and failure strain). Then the composition and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well …
Effects Of Processing Parameters On The Embrittlement Of Self Reacting Friction Stir Welds, David Eric Taylor
Effects Of Processing Parameters On The Embrittlement Of Self Reacting Friction Stir Welds, David Eric Taylor
LSU Master's Theses
Friction Stir Welding (FSW) has been adopted as one of the major welding processes for joining Aluminum. Many aerospace and marine structures are welded through this novel FSW processes currently. The Lockheed Martin Space Systems (LMSS), Michoud Operations, in New Orleans is continuously pursuing Friction Stir Welding technologies in its efforts to advance fabrication of the external tanks of the space shuttle. Recently, a reduction in mechanical strength (embrittlement) has been observed especially in self-reacting (SR) friction stir welds. This strength reduction was attributed to Residual Oxide Defects (ROD) but the exact reasons for this type of behavior needed to …