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 20 of 37 for “"yield surface"”.
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Experimental yield surface studies for the compaction of metal powder
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1993.
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A nonlinear viscoplastic double yield surface constitutive model for geologic materials
… this aim the constitutive model is based on two yield surfaces based on overstress viscoplasticity theory: one is quasi-instantaneous (for the fast part of plastic deformations) and the other is viscous (for the slow part of plastic deformations). This assumption permits the reliable simulation …
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A new constitutive model for the finite element analysis of metal powder compaction
… work has concentrated on the use of quadratic yield surfaces but experimentation has shown that this type of yield surface does not always correctly represent metal powder behaviour (Brown, 1994 ). This thesis details the development of a new constitutive model for the finite element analysis …
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Yielding of unsaturated soil.
… models is the suggestion of the existence of a yield surface in mean net stress : deviator stress : suction space. Suction-controlled triaxial tests were performed to investigate the shape of the yield surface for unsaturated compacted speswhite kaolin with a particular stress history. The tests …
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Calculation of Notch Strains Under Multiaxial Nominal Loading
… plasticity theory to define a structural yield surface in nominal stress space that incorporates both the isotopic material properties and the anisotropic geometry factors of the notch, and accounts for varying degrees of constrained plastic flow at the stress concentrator. Plastic strain …
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A yield function to simulate earing in the deep drawing of aluminium
… texture models or phenomenological yield surface models. Crystallographic models have the advantage over phenomenological ones in that they are able to describe both initial and evolving anisotropy. However, they are very demanding in terms of computational power and are reported to …
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Climatic and Geomorphic Interactions on Alluvial Fans in the Atacama Desert, Chile
Alluvial fan surfaces in the Atacama Desert of northern Chile preserve evidence of recent, precipitation-driven, surface flows. Determining the hydrologic characteristics of these flows is important for understanding the effects of rare yet significant storms in the region. Flow reconstruction, …
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Shear behaviour and stiffness of naturally cemented sands
… of confining pressures. Identification of the yield surface was found to be an essential feature to describe the shear behaviour of the soils examined. The determination of the yield points of such stiff soils required internal measurements of stresses and strains, with an accuracy higher than …
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Mechanics of inelastic deformation and delamination in paperboard
… of interface separation is controlled by a limit surface in the normal-shear traction space. The limit surface is taken to shrink with a monotonically-increasing scalar internal variable reflecting damage associated with the history of inelastic relative interface displacement. (2) A …
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Numerical Analysis of Stable Crack Growth in Elastic-Plastic Materials in Small Scale and General Yielding
… for steady state crack growth under small scale yielding conditions has the feature that the finite element mesh convects along with the moving crack tip. Various models for plastic flow were used. In Mode III, calculations were carried out for J(,2) incremental theory and a modified J(,2) …
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Finite element micromechanics modeling of inelastic deformation of unidirectionally fiber-reinforced composites
… analysis using the endochronic theory without a yield surface. The underlying algorithm for integrating the endochronic constitutive equation was derived by piecewise linearization of the plastic strain path. The approach was employed to solve a micromechanics boundary value problem of a …
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Incorporating Grain Size Effects in Taylor Crystal Plasticity
… equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or materials that contain unequal grain size distributions. These deficiencies can be overcome by incorporating both grain size and orientation characteristics into crystal plasticity theory. …
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Non-Linear Finite Element Method Simulation and Modeling of the Cold and Hot Rolling Processes
… Prandtl-Reuss) formulation, with a von Mises yield surface, the Praguer kinematic hardening rule, and the Ramberg-Osgood hardening material model. The FE models also demonstrate that the steel in hot rolling can be modeled using the rigid-viscoplastic (flow Levy-Mises) formulation, with a von …
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Micromechanical finite element model for constitutive elastoplastic analysis of unidirectional fiber-reinforced composites
… modeled using the endochronic theory without a yield surface. Various off-axis elastoplastic characteristics predicted by the mini grid for a boron/aluminum composite are presented. Comparison with experimental data and a fine grid finite element solution shows very good agreement and …
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The Role of Soil Stiffness in Reverse Fault Rupture Propagation
… constitutive model with a strain dependent yield surface and non-associated flow was employed to study the plastic soil properties which affect the rate of surface fault rupture propagation in reverse events. These numerical simulations show a trend for soils with higher stiffness to have a …
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Mechanical response of unidirectional Boron/Aluminum under combined loading
… includes the elastic material properties, yielding and subsequent hardening of the unidirectional composite under different stress ratios in the material principal coordinate system. The elastic response is compared with the prediction of the transformation theory, based on the far field …
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The mathematical modelling of concrete constitutive relationships
… in Chapter Three. A three-dimensional concrete yield surface is developed in Chapter Three. This yield surface is used in the theory of hardening plasticity to establish the incremental constitutive relationships for concrete. Furthermore, this model is extended to represent the strain-softening …
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Numerical simulation of implant-bone interaction following cementless joint replacement
… coating, which covers a portion of the component surface, to achieve the required mechanical interlock. Once mineralised bone tissue has formed within .the porous surface, a stable bond results which will be maintained by the normal bone turnover processes, thereby providing long term attachment. …
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Equivalent plastic strain for the Hill's yield criterion under general three-dimensional loading
… applications, an accurate model of the initial yield surface of materials with a significant degree of anisotropy is required. Anisotropy due to preferred orientation can occur in sheet metal parts used in automotive applications due to the rolling processes used to form the sheets. Hill's …
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The heterogeneous partial oxidation of light alkanes
(cont.) With this approach, an upper bound on the yield for OCM was computed. Results showed that even with optimal surface chemistry, strict limits existed on the attainable yield. Surface energetics necessary for superior OCM performance were identified and the origins of these requirements …
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