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Plastic deformation of silver micro-wires under uniaxial tensionChen, Xiaoxiao, 陈晓晓 January 2011 (has links)
published_or_final_version / Mechanical Engineering / Master / Master of Philosophy
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Theoretical modelling and numerical simulation of plastic deformation of nanostructured materials with high strength and ductilityLi, Jianjun, 李建军 January 2013 (has links)
Nanostructured materials have attracted intensive scientific interests during the past two decades due to their outstanding physical and mechanical properties. However, the brittleness of nanostructured materials posed a great challenge for their engineering applications. Recently, several strategies were successfully adopted to produce nanostructured materials with both high strength and ductility such as surface-nanocrystallized (SNC) materials, nanocrystalline materials with stress-induced nanograin growth and nanotwinned metals. A lot of molecular dynamics (MD) simulations, modelling and experiments have been conducted to investigate the deformation mechanisms and the correlated exceptional mechanical properties and considerable progress has been made. However, some problems remain unsolved. For example, the complicated structure of SNC materials due to its grain size gradient (GSG) surface layer makes it difficult to establish a quantitative model for prediction of their strength and ductility; the main mode of nanograin growth in nanostructured materials, i.e., shear-coupled migration of grain boundaries (GBs), was experimentally observed as contributing to their enhanced ductility, but the mechanism of the enhancement remains unclear. In addition, there exist contradictory results for the grain size dependence of transitional twin thickness that corresponds to the maximum strength of nanotwinned metals. All these issues should be addressed to gain a better understanding of the mechanism-ductility correlation in order to provide some guidelines for designing lighter, stronger and ductile nanostructured materials. Therefore, an attempt was made to study the plastic deformation of nanostructured materials with high strength and ductility by theoretical modelling and numerical simulations.
Firstly, the enhanced balance of strength and ductility of SNC materials was studied using a combination of theoretical analysis and finite element simulation. A criterion was established for determining the ductility of SNC materials. The results obtained showed that the ductility of a SNC sample could be comparable to that of its coarse-grained counterpart, while it simultaneously possessed a much higher strength than that of the latter if optimal GSG thickness and topmost phase grain size were adopted. Then a dislocation-density-based model was proposed to quantitatively predict the plastic deformation of SNC materials; the stress-driven nanograin growth was also incorporated in the said model. The capability of the model in predicting the strength and work hardening of SNC materials was validated by the existing experimental results. Thirdly, physical models for shear-coupled migration of GBs in nanostructured materials were developed to explain the general coupling between the shear and the normal migration of GBs observed in MD simulations and experiments. The coupled migration process was found to be a general and effective toughening mechanism in nanostructured materials. Moreover, our study showed that the shear-coupled migration is able to enhance the intrinsic ductility considerably when it cooperates with GB sliding. Finally, an elastic-viscoplastic constitutive model based on the competition of intra-twin and twin-boundary-mediated deformation mechanisms was proposed to predict the grain size dependent transitional twin thickness of nanotwinned metals. A linear relation between the transitional twin thickness and the grain size was predicted, which was in excellent agreement with the results obtained from MD simulations and experiments available in the literatures. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy
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FINITE DEFORMATION AND STABILITY OF NONRECTANGULAR ELASTIC RIGID FRAME STRUCTURESQashu, Riyad K. January 1980 (has links)
No description available.
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MECHANICAL ANALOGS OF NONLINEAR STRESS-STRAIN HYSTERESIS IN METALSHonig, Ernest Martin, 1941- January 1973 (has links)
No description available.
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Functional analysis of the response behaviour of structured media.Basu, Sudhamay. January 1973 (has links)
No description available.
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The effect of anticlastic curvature on stresses and deformations in a shell of revolution.Schütz, Reinhard. January 1972 (has links)
No description available.
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Microstructural analysis of finite deformation in FCC polycrystalsLustig, Steven K. 05 1900 (has links)
No description available.
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High temperature monotonic and cyclic deformation in a directionally solidified nickel-base superalloyHuron, Eric S. 05 1900 (has links)
No description available.
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The finite element method for stress and deformation analysisKam, Lit-Yan 05 1900 (has links)
No description available.
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Measurement of inhomogeneous deformation fields in polycrystalline OFHC copperSchroeter, Brian Mark 05 1900 (has links)
No description available.
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