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 24 for “"SURFACE CRACK"”.
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Fatigue growth of surface flaws in finite plates
… most commonly observed structural defect is the surface crack. The primary difficulty in analyzing the growth of surface cracks is the stress intensity factor which varies from point to point along the crack due to crack front curvature and the complex local geometry. The study of surface cracks …
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A Machine Learning and Computer Vision Framework for Damage Characterization and Structural Behavior Prediction
… work focuses on using computer vision to relate surface (and limited subsurface) damage observations to quantitative damage and load levels in structural components. In particular, image processing and machine learning regression techniques have been used to build predictive models capable of …
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Crack Path Predictions Under Mixed Mode Loading In Aero-Structures: Measurements and Analysis
… conditions, the flaw is likely to undergo stable crack growth (SCG) in ductile materials. Understanding such fracture events in ductile materials is an important component of structural integrity analysis for ductile structures, especially since there are no general fracture criterion available to …
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Análise elasto-plástica da propagação de trincas não-passantes em estruturas de superfície utilizando elementos escalares
… of this work is to analyse the behaviour of surface structures with part-through surface crack. The structure is modeled using degenerated tri-dimensional quadratic finite elements in conjuntion with line-spring elements for crack simulation. The analysis is performed considering linear …
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The Propagation of Stress Corrosion Cracks in Alpha-Brasses
… transgranular and intergranular stress corrosion cracks in commercial grade alpha-brasses tested in a tarnishing ammoniacal solution. Observation of the surface crack traces indicated that the transgranular cracks propagated discontinuously by the sudden appearance, in its entirety, of a fine …
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Response of a cracked rotating shaft with a disk during passage through a critical speed
Non-stationary motion of a cracked rotating shaft with accelerating or decelerating angular velocity Ω through a critical speed is studied. The shaft has a breathing transverse crack and a disk. There are two parts, which are the investigation of flexural response, neglecting the torsional …
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The effect of cracks on the dynamic behavior of bars and shafts
Nondestructive methods of detecting cracks in structural components and machinery are important, both in preventing failures and in establishing maintenance procedures. This thesis considers how the vibration behavior of cracked members can be modelled mathematically and how these mathematical …
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Corrosion Protection Service Life of Epoxy Coated Reinforcing Steel in Virginia Bridge Decks
… coatings. The size and length distributions of cracks in Virginia bridge decks were investigated to assess the frequency and severity of cracks. Correlation of cracks with chloride penetration was used to characterize the influence of cracking on deck deterioration. Cracks influence the rate of …
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Theoretical analysis and experimental investigation of contact fatigue and surface damage in prealloyed and diffusion bonded sintered steels
The contact fatigue and surface damage of prealloyed (Fe-0.85Mo, Fe-1.5Mo) and diffusion bonded (Ni-free, low-Ni, high-Ni) powder metallurgy (PM) steels were investigated. Materials subjected to contact stress fail due to the nucleation of subsurface cracks (contact fatigue cracks), nucleation of …
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Fatigue life prediction on nickel base superalloys
… developed with promising initial results.<br/>Crack initiation at high temperatures has been studied in CMSX4 in both air and vacuum environments, to elucidate the effect of oxidation on the notch fatigue initiation process. In air, crack initiation occurred at sub-surface interdendritic pores …
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Rolling Contact Wear of Hybrid Ceramic Bearings with Refrigerant Lubrication.
… that residual stresses are relieved due to sub-surface damage and are inversely related to stress cycles. Maximum tensile stresses at the edges of the contact path cause a weaker residual stress field at the sub-surface crack front.
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Three-dimensional boundary element and experimental analysis of lubricant ceramic surface ring cracks in rolling contact.
Surface defects such as ring cracks are located on silicon nitride ceramic rolling elements.The random nature of ring crack position creates difficulties in predicting rolling contact fatigue (RCF) life. The influence of the lubricant, contact pressure and crack geometry on the RCF mechanism is …
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The topological derivative and its applications to fracture-based analysis and design
… such as the introduction of an infinitesimal crack or hole. In a previous work, Silva et al. [1] developed a first-order approximation of the energy release rate field in a two-dimensional domain associated with a small edge crack at any boundary location and any orientation. In this thesis, …
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Role of cement content in determining resistance of concrete to reinforcement corrosion
… be more severe in the presence of defects (e. g. cracks)in the concrete surface. The review of published literature shows that at fixed w/c ratio, cement reduction is not detrimental to fresh and hardened concrete properties and may improve performance in some cases. However, cement content …
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Concrete crack width under combined reinforcement corrosion and applied load
… resulting primarily from premature concrete cracking and spalling have an estimated cost running to $100 billion per annum world-wide. The continual demands for greater load carrying capacity of existing infrastructure only exacerbate the problem. In practice, concrete crack width propagation …
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Data Structure and Error Estimation for an Adaptive <i>p</i>-Version Finite Element Method in 2-D and 3-D Solids
… the stress intensity factor of a semi-elliptical surface crack in a finite-thickness plate, non-uniform <i>p</i> analysis used fewer degrees of freedom than a conventional <i>h</i>-type element analysis found in the literature.
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Propagation of delamination in layered anisotropic cylinders
… it as a thin shell, with an axisymmetric crack in the adhesive layer between two laminae, and an axisymmetric loading acting as the driving force. The axial and shear strains of the reference plane are considered negligible compared to its circumferential strain. The cylinder, after …
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Deterioration and Cracking in Reinforced Concrete Bridges
… of the internal steel reinforcement and cracking of the concrete cover. Thus, half-joints are particularly vulnerable to bond degradation due to corrosion and cracking. To develop an improved understanding of deterioration in reinforced concrete, and half-joints in particular, three …
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Fracture mechanics analysis of offshore wind turbine monopile structures for lifetime extension
… it is likely that an aged monopile already has a crack initiated. There may actually be multiple cracks on the same plane due to manufacturing defects from the time of fabrication or due to loading. Therefore, later life fatigue calculation must focus on the crack propagation phase. Crack …
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Engineering properties and structural behaviour of high strength reinforced concrete beams
… concrete (HSRC) beams, sectional ductility, crack patterns and surface crack width. Further, theoretical analyses were undertaken to idealise the nature of the concrete stress block developed in HSRC beams from elastic to ultimate load condition. In other words, proper idealisations of stress …
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