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 45 for “"Crack Closure"”.
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Fractographic investigation of crack-closure.
Thesis: M.S., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 1978
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An Analytical Model Which Combines Roughness- and Plasticity- Induced Fatigue Crack Closure
… using the PICC-RICC model. The initial crack length (a$\rm\sb{i})$ for propagation was estimated. The predicted notch fatigue strength compared favorably with the Initiation-Propagation (I-P) Model prediction and test data. The existence of a ""worst case notch"" previously postulated …
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Fatigue Crack Closure and Crack Growth Outside the Small Scale Yielding Regime
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.
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Investigation of thermal effects on fatigue crack closure using multiscale digital image correlation experiments
… length scales, the thermal effects on fatigue crack closure of Hastelloy X, a nickel-based superalloy. Using multiscale, digital image correlation (DIC), macroscale experiments were performed at 2x magnification (2 µm/pix), providing full-field crack closure measurements. Microscale experiments …
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A crack closure model for the fatigue behavior of notched components and welded joints
"Newman's Dugdale strip-yield model for crack closure was modified to estimate the crack-closure behavior of cracks emanating from notches. The results obtained using this crack-tip plastic deformation model showed that the estimated effective stress-intensity ratio $U(a)$ (=$\Delta K\sb{\rm …
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High resolution fatigue crack growth analysis of crack closure and slip irreversibility using digital image correlation
Crack closure and slip irreversibility in the fatigue crack growth of 316L stainless steel were investigated using digital image correlation (DIC). A polycrystalline and a oriented specimen were tested to study mode I fatigue crack growth, while oriented specimens were used to study mixed mode (I …
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Numerical Modeling Issues in Finite Element Simulation of Plasticity Induced Crack Closure With an Emphasis on Material Model Effects
Plasticity induced crack closure (PICC) has a potentially strong effect on the growth rate of fatigue cracks in metal structures. As a crack grows through previously yielded material, the permanent deformation in the crack wake Shields the crack tip from the full impact of the remote load. This …
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Finite element simulations of fatigue crack growth and closure
… element program was used to simulate fatigue crack growth and closure. The study has identified some of the factors that contribute to crack closure. It has provided an evaluation of stress, strain and displacement fields near crack tips and their contribution to crack closure. The thesis …
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A model for the long-life fatigue behavior of small notches
… regime fatigue properties was studied. A crack-closure-at-a-notch (termed CCN) model for predicting the fatigue life and fatigue threshold stress was developed based on the assumption that the da/dN vs. $\Delta$K$\sb{\rm eff}$ relation is a unique material property independent of crack …
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The Effects of Load Ratio on Threshold Fatigue Crack Growth of Aluminum Alloys
… structures are threatened by the presence of cracks. Structural failure occurs if a crack larger than a critical size exists. Although most well designed structures initially contain no critical cracks, subcritical cracks can grow to failure under fatigue loading, called fatigue crack growth …
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Hydrogen degradation and microstructural effects of the near-threshold fatigue resistance of pressure vessel steels
… of the mechanism of environmentally-induced crack propagation and the mechanism by which process-induced microstructures as in thick section weldments affect the fatigue resistance of the structure. At low stress intensities near-threshold [delta]K₀ ([delta]K = Kmax - Kmin), water vapor in …
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Effect of Variable Amplitude Loading on Fatigue Crack Growth Rate
Fatigue crack growth (FCG) is a major cause of failure in many engineering component and structure that are subjected to dynamic loading conditions. Several models have been proposed for estimating crack growth rate da/dN under various conditions. The majority of work reported has focused on …
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Relating fatigue crack growth to microstructure via multiscale digital image correlation
This work investigates fatigue crack growth at multiple scales and links material deformation to microstructural properties. The optical technique of digital image correlation (DIC) is well suited for this task since it provides quantitative full-field deformation measurements at multiple length …
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Fatigue crack growth in ceramics containing a viscous grain boundary phase at elevated temperatures
Elevated-temperature crack growth behavior in a commercial Al$\sb2$O$\sb3$ and a hot-pressed 30 vol.% TiB$\sb2$-SiC composite was examined under tensile static loading (static fatigue) and tension-tension cyclic loading (cyclic fatigue). The study was carried out at temperatures of …
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Non-linear individual and interaction phenomena associated with fatigue crack growth.
… a new approach for the analysis of fatigue crack growth, known as damage tolerant design. This approach utilises fracture mechanics principles to consider the propagation of fatigue cracks from an initial crack length until final fracture, or a critical crack length, is reached. Since the …
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Finite element models for predicting crack growth characteristics in composite materials
… finite element models for the prediction of crack growth characteristics, including crack growth direction, in laminated composite materials are presented. Mixed-mode crack growth in isotropic materials, unidirectional and laminated composites is considered. The modified crack closure method …
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A critical analysis of fatigue-crack propagation data for 2024-T3 aluminum.
Fatigue-crack growth data for 2024-T3 aluminum was used to evaluate the accuracy of Forman's equation. Forman's equation was found to predict from one-third to twice the observed cycles to a given crack length when applied to multiple cyclic stress ratios. An alternative approach was developed, …
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Theoretical and experimental modelling of multiple site damage in plate components.
… damage (MSD), such as two or more interacting cracks, currently represents a challenging problem. The lifetime prediction of structural components with MSD is still largely based on 2D single crack solutions available in various handbooks or derived from the simplified finite element analysis. …
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Closure of fatigue cracks at high strains
… were conducted on smooth specimens to study the closure behavior of short cracks at high cyclic strains under completely reversed cycling. Testing procedures and methodology, and closure measurement techniques, are described in detail. The strain levels chosen for the study cover from …
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