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 51 for “"necking"”.
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Necking strains and forming limits of aluminum
Includes bibliographical references (pages 127-129).
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Effect of loading history in necking and fracture
… on metal forming limit diagram (FLD). Given the necking locus under proportional loading conditions, and using a non-linear accumulation rule of forming severity index, the proposed model well predicts the FLDs under different pre-loading conditions. As an extension of the ductile fracture locus …
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Analysis of plane strain necking and fracture in strain hardening materials
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.
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Analytical and numerical prediction of localized necking in sheet metal forming processes
<p>The goal of this research is to investigate, develop and validate analytical and numerical tools that can accurately predict failure in sheet metal forming operations. The strain-based forming limit curve (FLC) is one of the tools to predict the maximum permissible strains of thin metallic …
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The Role of Branching Topology on Rheological Properties and its Effect on Film-Casting Performance
… theory. Analysis of film-width reduction or necking during film-casting for the series of LLDPE-based resins determines whether uniaxial extensional rheological characteristics, in particular strain-hardening, that are a result of LCB influence the film-necking properties. At the lowest …
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High energy x-ray diffraction microstructural analysis of oxide dispersion strengthened steel for advanced nuclear systems
… measurement of material responses from both necking and un-necked parts of the specimens. From the X-ray measurement, the load partitioning between the ferritic matrix and the nanoparticles was found to occur during the yielding process. The nanoparticles experienced a dramatic loading …
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Tensile Fracture Mechanisms of Ferritic/martensitic Structural Materials
… and severe distortion of grain structure in the necking region, it is a challenge to determine the true strain/stress curve, a critical input in finite element modeling (FEM) analysis. Previous scholars have developed several analytical methods to characterize true strain/stress behavior after …
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Modeling of sheet metal fracture for shell finite elements with component level validation
… elements, violated after the onset of localized necking, is responsible for an inaccurate numerical prediction of mechanical response with mesh-size sensitivity. This thesis proposes a new approach to predict ductile failure with shell elements. It is based on the concept of a Domain of …
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Fracture prediction in metal sheets
… For ductile sheet, fracture is preceded by necking. Prediction of necking which limits sheet metal formability is well established and has been developed over the past several decades. However, an in-depth understanding of the mechanical process inside the neck leading to sheet metal …
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Development of a hybrid process for manufacturing surgical-grade knife blade cutting edges from bulk metallic glass
… and were dependent on the balance between necking and elongation during drawing. The amount of necking and elongation was determined by the free volume behavior of bulk metallic glass and the formation of nano-crystals. Both these phenomena were found to be influenced by the atomic mobility …
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Design of a silicon carbide micro-hotplate geometry for high temperature chemical sensing
… designs minimize heat lose from the hotplate and necking creates heat generation regions. The excellent thermal properties of SiC allow heat to be transferred from the necked tethers to the hotplate; producing a hotplate with a uniform temperature distribution, important to the sensitivity and …
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Effects of polymer concentration and molecular weight on the dynamics of visco-elasto-capillary breakup
… Below a critical dilution, the stress in the necking thread is carried solely by the solvent with no appreciable contribution from the polymer chains, and the dynamics of the necking process change appreciably. A sensitive force transducer is also added to the CABER. This allows us to measure …
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The role of molecular length scale on the viscoplastic response of amorphous polymer nanofibers in the glassy state
… very repeatable post-yield behavior including necking and pronounced strain-hardening. Specifically, the ratio of the structural length scale (fiber diameter) to the intrinsic macromolecular length scale (root-mean-square end-to-end chain distance), Dnorm, was shown be an excellent scaling …
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Effect of non-linear loading paths on sheet metal fracture : large strain in-plane compression followed by uniaxial tension
… onset of fracture. The phenomenon of localized necking occurs prior to ductile fracture in most types of loading of sheet metal. In order to measure the local state of stress and strain, a hybrid experimental and numerical method is tested. The Finite Element model can accurately predict the …
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Linking Rheological and Processing Behavior to Molecular Structure in Sparsely-Branched Polyethylenes Using Constitutive Relationships
… LDPE, exhibited the least degree of necking at distances less than the HDPE frostline. The sparsely-branched HDPE resins films had similar final film-widths that were larger than those of the linear HDPE. As the drawdown ratio was increased, film width profiles separated based on …
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The Effect of Composition on the Linear and Nonlinear Mechanical Properties of Particulate Filled Elastomers
… rubber. For the first time, necking was observed for a lightly cross-linked poly(dimethylsiloxane) elastomer filled with 30 phr (parts per hundred rubber) or more of high surface area (≥300 m<sup>2</sup>/g) fumed silica. A series of linear and nonlinear mechanical properties …
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FAILURE MECHANISMS OF ULTRA HIGH MOLAR MASS POLYETHYLENE SINGLE FIBERS AT EXTREME TEMPERATURES AND STRAIN-RATES
… was observed to be pseudo-brittle, plateauing, necking, and non-failure and transitions between these phases were observed within a strain-rate dependent temperature range. For low and intermediate strain rates, a temperature and strain-rate equivalence is observed: a decadal increase of …
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Damage and repair evolution of cold formed linepipe steel
… results reproduce the essential features of necking phenomena and provide a physical insight into damage evolution within a tensile testpiece under given necking conditions. Dual phase steel is of greater importance industrially, than a single phase steel, but because of the greater …
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Disproportionate Collapse Resistance of Timber Beam-column Connections
… in order to accurately simulate their post-necking behaviour. Then, two custom-designed knife-plate beam hanger type steel connectors were tested experimentally and numerically under shear and moment-dominated loading until failure to assess their performance under large deformations. …
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Study of microstructure evolution in F/M steel T91 by in-situ synchrotron wide-angle X-rays scattering
… fracture happened violently with huge cracks on necking center cross-section, while fracture happened slowly with voids and dimples on cross-section under higher temperatures. SEM Energy Dispersive Spectroscopy (EDS) mapping also found that rupture protrusions on necking center edges had higher C …
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