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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 79 for “"Crack length"”.
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Modified effective crack-length formulations in elastic-plastic fracture mechanics
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1992.
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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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Metal/polymer interactions in polyimide adhesives
… BDSDA/ODA bonded to steel had an initial crack length of 34 mm. Even after eleven days the crack length was only 47 rnm, which was the initial crack length for the next best polyimide. Thus, metal-catalyzed oxidation of sulfur did take place, but not to an extent to have a noticeable …
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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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A Quantitative Study of the Weldability of Inconel 718 Using Gleeble and Varestraint Test Methods
… and Varestraint mechanical test methods. Hot cracking susceptibility was examined in either alloy using a sub-scale Varestraint test method at 5 augmented strain levels: 0.25%, 05.%, 1%, 2%, and 4%. Maximum crack length, total crack length, and number of cracks were measured for each strain …
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Investigation of the Effects of Geometry on the Efficiency of the Double Lap Joint of Unidirectional Fiberglass Composites
… performed by modeling the damage growth at the crack tip as a self similar crack extension through compliance matching procedure. The crack growth resistance at instability and the corresponding critical strain energy release rate are independent of initial crack length in the range of crack …
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Computational study of compact tension and double torsion test geometries
… of cyclic stress intensity below which fatigue crack growth does not occur. For a particular material and environment, this threshold value, Δҝₜₕ, is determined experimentally by monitoring growth of a crack (typically in a compact tension ( CT) specimen) and continually reducing cyclic stress …
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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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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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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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Statistical distribution of times to crack initiation in service using C-130 inspection data
Methods by which in-service crack inspection data may be reduced to yield meaningful time to crack initiation and initial flaw size data are examined. A method is developed by which inspection data consisting of time of inspection and crack length can be used to determine. crack growth constants. …
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Fatigue Life Estimates for a Notched Member in a Corrosive Environment (Corrosion)
… field, and the portion where nominal stress and crack length dominate fatigue damage assessment, was used to estimate fatigue lives for center notched plate specimen.
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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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Crack growth resistance in nuclear graphite
R-curve behaviour is often used for evaluating crack growth resistance in quasibrittle materials but few studies have focused on polycrystalline graphite. In this study, R-curve behaviour in three commercial grade nuclear graphites, of varying structure and properties, is compared using an optical …
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Behavior of alloy 617 at 650°C in low oxygen pressure environments
… static loading. Of particular interest was the crack growth rate in these conditions. For that, tests were conducted at a constant stress intensity factor of 49.45 MPa'm (45 ksidinch) using a direct current potential drop measurement system to determine crack length. High purity argon gas …
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Exploration of Wood DCB Specimens Using Southern Yellow Pine for Monotonic and Cyclic Loading
… earlywood growth and the grain angle along the length of the beams. The grain angle and the stiffness difference between latewood and earlywood growth caused the effective stiffness, (ExxI)eff, to vary along the length of the beam. The effective stiffness variation caused variations in the …
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Water based adhesive primers on aluminum substrates
… wedge samples were immersed in 80°C water and crack lengths were monitored as a function of time. Both the initial crack length and crack propagation were minimized when the primer thickness was a little less than the aluminum oxide thickness. In a separate study, the aluminum oxide surfaces …
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Adhesion Strength of Cordierite Bulk Coatings on Molybdenum Substrates
… was determined from indentation load vs. crack length data by examining the residual stress and critical buckling load of the ceramic coatings. The interfacial fracture toughness values obtained using a slightly different indentation analysis agree with those in the literature. …
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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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Αστοχία ρηγματομένων όλκιμων πλακών με δύο συμμετρικές εγκοπές
… is to study the interaction between a crack and two symmetrical edge notches perpendicular to the plane of the crack. Based on the strain energy density criterion the critical stress for crack growth initiation is determined. The influence of body geometry as it is dictated by notch …
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