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 30 for “"process zone"”.
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Fracture process zone : microstructure and nanomechanics in quasi-brittle materials
… begin (and end) at a crack tip; the "Fracture Process Zone" (FPZ) is a region of damage around the crack tip. The context of this research is the FPZ in quasi-brittle materials, which is characterized by cracking at various scales. This study focuses on crack propagation and FPZ development at …
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A nanomechanical investigation of the crack tip process zone of marble
… and nanomechanical properties in the crack tip process zone (zone of microcracking at the tip of a propagating crack) of a brittle geomaterial. Samples of Carrara marble with pre-existing cracks ("flaws") were loaded in a uniaxial testing machine until the process zone appeared at the tips of …
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Effect of specimen geometry and test configuration on the fracture process zone for asphalt materials
… to the deformation occurring in the fracture process zone (FPZ). FPZ is the region surrounding the notch tip that develops micro cracks before a macro crack is observed. Hence, the energy dissipation due to the deformation that occurs in this region eventually controls the global response of …
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Novel techniques for fracture monitoring in crystalline rock
… structures during failure. Often times, fracture processes observed in the laboratory do not accurately represent what occurs in the field due to the effect that specimen size and loading conditions have on fracture properties, namely, fracture toughness and the size of the fracture process zone. …
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Micromechanical Simulation of Fatigue in Nodular Cast Iron
… and they are resolved discretely in fracture process zone. The region outside of the fracture process zone is considered as a homogenized medium. When positive alternating loads are applied, ligaments in the fracture process zone show ratchetting behavior, which is responsible for an effective …
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Behaviour of fracture process zones in concrete influenced by simultaneously applied normal and shear displacements
… remains consiant during the entire fracture process. However, since the mid-eighties the applicability of the model has been further extended to cases where the direction of the principal stresses is changed during the fracture process. The applications of the model in these cases require …
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Prediction of service load of concrete structures after cracking using ultrasonic technique
… study showed that crack growth and microcrack zone in cementitious composites can be quantitatively detected by the ultrasound technique. To predict crack propagation during the fracture process in plain concrete, an effective compliance fracture model is proposed. A large fracture process zone …
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Mechanisms of Ductile Fracture: Void Growth by Dislocation -Loop Emission and Hydrogen-Assisted Crack Propagation
… propagation in materials which fail by ductile processes in the presence of hydrogen. First the hydrogen effect on dislocation mobility and lattice dilatation was considered to establish the material constitutive law. Simulations in a unit cell containing a void were carried out to devise …
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Fracture Behavior of Masonry Bond
… toughening action took place during the fracture process and the fracture process zone at the crack tip was small relative to plain concrete and mortar. This was due to the highly brittle fracture nature associated with pre-determined weak crack path and relatively smooth crack surfaces. Using the …
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Evaluation of viscous effects in crack tip fields in recycled asphalt pavement materials using digital image correlation
… strain recovery, crack propagation and fracture process zone (FPZ). Energy dissipation was studied on two different aspects: first was the dissipation under the loading head due to crushing of the specimen; the second was dissipation in the bulk of the material. No crushing of the material was …
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Toughness and Flaw Tolerance by Biologically Inspired Approaches
… simple constituents, bottom-up self-assembly process, low density and high potential performance. Like their natural counterparts, bioinspired materials are often sensitive to humidity. In Publication I, we study the effect of water on our clay/polymer nanocomposite films and find that water …
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Simulation of Fracture of Concrete Using Micropolar Peridynamics
… experiments, and the size of the fracture process zone, the damage, and cracking patterns are match experiment as well. As a part of the research the isotropicity of the hexagonal particle lattice , proposed by Gerstle in 2011 and used in our simulations, is shown analytically, and the …
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Fracture of Asphalt Concrete: A Cohesive Zone Modeling Approach Considering Viscoelastic Effects
… effects occurring in a relatively large fracture process zone, a cohesive zone model (CZM) is employed. Finite element implementation of the CZM is accomplished via user subroutines that can be used in conjunction with general-purpose software. The bulk properties (e.g. relaxation modulus) and …
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Investigation of Toughening Mechanisms in the Fracture of Asphalt Concrete Using the Clustered Discrete Element Method
… provides a physical description of the fracture process zone in laboratory fracture tests, the influence of temperature, effects of material parameters, loading rate dependency, and specimen size effect on fracturing of asphalt concrete. The abilities to simulate mixed-mode fracture, crack …
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Three-dimensional modeling of failure in quasi-brittle materials and structures
… due to the presence of a nonlinear fracture process zone ahead of the crack front. Predictive models and design methodologies have to be able to reliably calculate the load capacity, or structural strength, of structures while taking into account the nonlinearity of the material behavior and …
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Mechanical properties and microcracking behaviour of heterogeneous rocks after high-temperature treatment
… of temperature on the evolution of the fracture process zone under mode I/II loading conditions. The results show that with the increase of temperature, the mechanical properties of rock (including peak load, generalized stiffness, mode I/II fracture toughness and absorbed energy) gradually …
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Strain gradient plasticity-based modeling of damage and fracture
… of the size of the specimen - as the plastic zone adjacent to the crack tip is physically small and contains strong spatial gradients of deformation. In this work a general framework for damage and fracture assessment accounting for the role of GNDs is provided. Different classes of gradient …
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Development of a numerical technique for modelling of multi-stage hydraulic fracturing in shale reservoirs
… cohesive cracks in a porous medium with fracture process zone at the crack tip, on the other hand, the Cohesive segments method in combination with Phantom Node Method, termed CPNM, is established. This numerical framework is implemented into a finite element analysis package (ABAQUS) along with …
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Assessment of rock fracture initiation using acoustic emission
DSpace SAF Submission Ingestion Package generated from Vireo submission #14339 on 2019-11-26 at 14:04:18
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Examination of flexural crack width prediction in concrete: comparison of analytical and numerical models
… to the tension area transforms the fracture process zone problem to the definition of a bond-slip relationship. Bond stresses generated at the rebar perimeter define the analytical relationships in design codes. These stresses control crack width at the tension surface. Results from the …
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