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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 55 for “"Asperity"”.
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Thermomechanical analysis of rock asperity in fractures of enhanced geothermal systems
… roughness with varying heights which is called asperity. The stability of asperity determines fracture aperture and hence imposes substantial effect on hydraulic conductivity and heat transfer efficiency in EGS.</p> <p>Firstly, two rough fracture surfaces are characterized by statistical method …
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Deformation mechanics of quartz at a single asperity under hydrothermal conditions
Pressure solution is a naturally occurring deformation process in fluid-bearing rocks, with implications for sediment consolidation rates and deformation in the mid to upper crust. The process involves dissolution at asperities under load; diffusion along grain-to-grain contacts; and precipitation …
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Finite element based modeling of multi-asperity contact and validation of Greenwood-Williamson model
… this model is often cited as it is ignoring of asperity interaction effects. This thesis aims to validate the Greenwood-Williamson model by using the finite element method to study multi-asperity contact and asperity interaction effects. The first step in the study of multi-asperity contact was …
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Investigating the Evolution of Rock Discontinuity Asperity Degradation and Void Space Morphology under Direct Shear
… prior studies have attempted to investigate asperity failure mechanisms, they have been hampered by the lack of appropriate visualization and modelling tools. In particular, until recently it was not possible to observe asperity damage without physically separating the joint specimen or …
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Effects of surface morphology and asperity deformation on the frictional behavior of coated sheet steels
Includes bibliographical references (pages 85-87).
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Micro-scale scratching by soft pad asperities in chemical-mechanical polishing
… on hard monolithic layers are modeled. At single-asperity sliding contact, the asperity contact pressure along with the interfacial friction that can induce surface layer yielding are first derived, for different asperity deformation modes: elastic, elastic but at the onset of yielding, …
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Multi-scale scratching in chemical-mechanical polishing
… the scratching of a Cu coating by a soft pad asperity, was modeled. It was first assumed that the asperity deforms linear elastically up to the onset of yielding. A Hertzian pressure distribution in contact with a coating, with and without friction, was modeled to determine the maximum contact …
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An Investigation into the Effects of Asperities on Geomembrane/Geotextile Interface Shear Characteristics
… and mechanism, as well as to identify the asperity parameters combination which optimizes the GMB/GTX interface shear strength. The GMB/GTX interface shear tests were conducted according to ASTM D5321, under saturated conditions with the “305 mm by 305 mm” direct shear box at applied normal …
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Theoretical and Experimental Investigation of Adhesion in Microelectromechanical Systems
… (EMD) elastic theory, an improved single asperity meniscus model considering asperity deformation due to both contact and adhesive forces was developed. Specifically included in this model was the solid surface interaction inside the contact area. It was found that due to asperity …
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Failure of asperities by hydraulically induced fatigue: a model for the generation of intraplate seismicity
… driven by cyclic tensile stresses within an asperity. Cyclic stresses result from cyclic pore pressure variations which propagate from the Earth's surface because of annual variations in the height of the water table. Asperities are postulated to be porous and permeable masses of saturated …
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Multiscale physics-based modeling of friction
… to develop a physics-based friction model at asperity-scale. Then, the statistical summation technique is utilized to build a multiscale modeling framework. A novel joint fretting setup is designed for friction experiments in a practical setting, and the developed models are tested. Both …
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Crustal heterogeneities and complexities of fault processes
… heterogeneity considered involves the concept of asperity. The presence of an asperity in the hypocentral region of the M = 6.5 earthquake of June 17-th, 2000 in the South Iceland Seismic Zone was invoked to explain the change of seismicity pattern before and after the mainshock: in particular, …
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Fault plane structure of the 1995 Antofagasta Earthquake (Chile) derived from local seismological parameters
… geo-scientific studies. In the presented thesis asperity structures are identified on the fault plane of the Mw=8.0 Antofagasta earthquake in northern Chile which occurred on 30th of July, 1995. It was a thrust-type event in the seismogenic zone between the subducting pacific Nazca plate and the …
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Numerical Simulation of Contacts Working Under Mixed Lubricating Conditions
… A substantial aspect of the ML regime is the asperity-asperity interface, whose tribological performance is significantly influenced by contact mechanisms, flash temperature and tribo-chemistry reactions. However, in this study, the focus has been solely on numerically simulating the fluid …
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Contact resistance in RFID chip-antenna interfaces
… to the problem, a random distribution of asperity types was analyzed. An expression was derived for the total force applied in terms of a given deflection and a range of asperity radii of curvature. A three-dimensional graph was created to show how each of these variables depends on the …
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An investigation of friction and wear mechanisms in selected thermoplastics
… wear of a polymer disk sliding against metal asperity models. The investigator was unable to observe actual particle formation but did identify elastic and plastic deformation of the polymer, and a debris buildup and extrusion process occurring at the leading edge of the asperity. On the …
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Rough Surface Interactions of Micro/nano-Scale Contact Systems
… systems has been developed accounting for both asperity and substrate deformation during contact. Compared to a representative asperity-based contact model, it was found that the proposed model is closer to actual contacts of a miniature system. Third, experimental measurements of dynamic …
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The effect of surface finish on piston ring-pack performance in advanced reciprocating engine systems
… was improved. Modifications were made to the asperity contact and oil flow resistance sub-models to enable a more accurate and more general description of surface texture. The accuracy of the new sub- models was validated with experimental results obtained from a ring reciprocating tester. …
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Surface texture enhancement of SLS processed turbine blades using a mix of flexible media and abrasives
… the Ansys package. The simulations include an asperity made of Grade 5 titanium, a SiC abrasive particle and, an HDPE particle as the flexible media. These simulations have tested process parameters such as abrasive size, asperity size and impact velocity. These simulations have shown that …
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Advanced modeling of planarization processes for integrated circuit fabrication
… and verify physical model assumptions. Pad asperity modulus and characteristic asperity height are measured by nanoindentation and microprofilometry, respectively. Pad aging effect is investigated by comparing physical measurement results at different pad usage stages. Results show that …
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