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 38 for “"Triaxiality"”.
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Fully-plastic back-bend tests for low-triaxiality plane strain crack growth
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.
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Deformation and fracture of polycarbonate and rubber-modified polycarbonate under controlled temperature, deformation rate, and notch stress triaxiality
… of strain rate, temperature, and notch stress triaxiality on deformation and fracture are studied. The Arruda-Boyce constitutive model for glassy polymers and finite element simulations are used to simulate the deformation of the polycarbonate homopolymer subjected to compression and tension …
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Prediction of ductile crack formation in uncracked bodies
… weighting functions for different stress triaxiality ranges where different ductile crack formation mechanisms occur ("shear fracture" in negative stress triaxialities, void nucleation, growth, and linkage in high stress triaxialities, a transition mode in intermediate stress …
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In situ measurement of lattice strain using synchrotron radiation and a conical slit system
… of stain, and reveal an elevated initial triaxiality which approached the expected value for tensile loading of an isotropic material as the sample was loaded. Potential error sources are discussed in relation to strain measurements and considerations when using the conical slit system are …
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Experimental investigation and constitutive modeling of the large deformation behavior of anisotropic steel sheets undergoing strain-induced phase transformation
… demonstrate the influence of both the stress triaxiality and Lode angle parameter on the austenite-to-martensite transformation kinetics. A stress-state dependent transformation kinetics evolution equation is proposed which describes the martensite content as a function of plastic strain, the …
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Mechanisms of Ductile Fracture: Void Growth by Dislocation -Loop Emission and Hydrogen-Assisted Crack Propagation
… the material constraint ahead of a crack tip. A triaxiality/hydrogen-informed cohesive element was devised to simulate the effect of the microscopic void response in the fracture process zone on the macroscopic crack propagation under plane strain small scale yielding conditions. Numerical …
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Micromechanics of Hydrogen-Induced Crack Initiation in Pipeline Steels and Subcritical Crack Growth
… we quantify the void growth dependence on stress triaxiality and hydrogen-induced material softening as a function of position ahead of a crack tip. Correlation of the calculated void diameters with experimentally measured ones leads to the identification of a microstructural length that …
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Effects of prior ductile tearing on cleavage fracture in the ductile-to-brittle transition region
… which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (typically $<$1-2 mm) routinely precede termination of the ${J-\Delta a}$ curve by brittle fracture. Large-scale yielding, coupled with small amounts of …
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Investigation of Taylor impact test of isotropic and anisotropic material through geometrical characteristics of specimens
… stress, equivalent plastic strain and stress triaxiality.
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Micromechanics of toughening in polymeric composites
… or cavitation-induced brittle failure under high triaxiality [e.g., polycarbonate (PC)]. Judicious choice of polymer composites alleviates the above concerns by spreading the inelastic deformation and damage throughout the material, thereby increasing the macroscopic toughness. This thesis focuses …
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Mechanics of Notched Izod impact testing of polycarbonate
… energy absorbed prior to failure under high triaxiality and high rate loading conditions. Much research has been done using Izod testing to compare the fracture energies of blends of Polycarbonate and rubbery materials; however the specific yielding and fracture mechanisms associated with …
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Fracture and plasticity characterization of DH-36 Navy steel
… by the stress state invariants of Lode angle and triaxiality.
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Analytical Development of A Plastic Hinge Detail for Steel SMFs
… weld from the critical cross-section, reduces triaxiality and eliminates through-thickness failure modes at the beam/column interface. The BPHC preserves the primary features of the PH-MN and provides performance at nearly the same efficiency, but, as a replaceable field-bolted component, is …
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An experimental and theoretical study on the effect of strain rate on ductile damage
… at fracture to material parameters such as triaxiality, lode angle and strain rate in a specimen, which is verified using experiments performed under various loading conditions and strain rates.
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Fracture prediction in metal sheets
… equivalent plastic strain with the stress triaxiality as a weighting function is considered. Using the equations of plane stress von-Mises plasticity and the strain-to-stress mapping procedure, the BW fracture criterion is transformed to the spaces of the principal tensile strains and …
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Micromechanics, macromechanics and constitutive modeling of the elasto-viscoplastic deformation of rubber-toughened glassy polymers
… since they fail in a brittle manner under low triaxiality conditions, such as under uniaxial tension. Polycarbonate is considered to be a more ductile polymer than PMMA and PS, since it will deform plastically under uniaxial tension. However, PC does exhibit brittle behavior under certain …
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Development of a punching technique for ductile fracture testing over a wide range of stress states and strain rates
… that the dependence of ductility on the stress triaxiality and Lode parameter must be accounted for, but this dependence has not been investigated in the dynamic range. The aim of the current thesis is to contribute a new methodology based on an instrumented drop tower that will allow for …
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Micromechanical modeling of the toughening mechanisms in particle-modified semicrystalline polymers
… filler particles and the level of applied stress triaxiality. In particular it is shown, that in the case where transcrystallized material spans the interparticle ligaments, the unique morphology of the matrix impedes dilatational expansion of the material, while promoting ...
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The corrosion fatigue behavior of notched 2024-T351 aluminum
… as those of other high strength aluminum alloys. Triaxiality and stress concentration were the main factors in determination of the notch characteristics. A new definition of notch ductility was developed in this study and the results compared to the use of area-contraction ductility. Air and 3% …
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The Orbital Structure of Galaxies and Dark Matter Halos in N-Body Simulations
… parameters of an elliptical galaxy, such as its triaxiality or the ratios of its principal axes. We are deriving a global occupation probability for self-consistent triaxial galaxies which are in agreement with theoretical expectations. Furthermore we find that the isophotal structure of the …
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