Browsing by Subject "Ductile"

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Risk-informed design of new anchor concept for floating energy production systems
(2016-05) Iturriaga Flores, Jose Eugenio; Gilbert, Robert B. (Robert Bruce), 1965-; Engelhardt, Michael D; Heredia Zavoni, Ernesto A; Kinnas, Spyridon A; Manuel, Lance
The motivation for this work was to (1) improve the performance of permanent mooring systems; (2) pursue a novel anchor concept that minimizes installation effort and exhibits a ductile failure, (3) meet system reliability targets while optimizing resources during installation and operation. The objectives of this research were to (1) develop a new concept for an anchor, (2) optimize the ratio of structural capacity to weight for different configurations of the anchor that are stable during freefall through the water; (3) develop a mechanism to free the shank of the anchor during pitch rotation; (4) develop understanding about how interactions between mooring lines, the anchor and the soil affect the performance of mooring systems; (5) assess the reliability of mooring systems and relate it to the reliability and design factors of safety of individual components in the system, (6) implement a risk-based framework to improve the reliability and efficiency of mooring systems for floating production systems and facilitate implementation of the new anchor concept. This work has produced a new anchor concept. The anchor (1) is liberated at a considerable height above the seafloor, (2) freefalls in a vertical position and trajectory through the water column, (3) embeds vertically into the soil, (4) rotates in places to align itself with an optimized direction and (5) slides laterally to embed deeper into the soil. This anchor has a theoretical efficiency, defined as the maximum holding capacity divided by the anchor weight, of more than 75 and significantly greater than most conventional foundations and anchors. The anchor also could be used to significantly increase the reliability of mooring systems by acting as a fuse to protect lines from breaking. The movement of the new anchor introduces ductility, meaning that the limit state potentially reached by the anchor is always related to excessive deformation and not a complete loss of restoring force. A new design philosophy for mooring systems where anchors have more probability of failing than the lines could be developed to improve the reliability of the system without increasing the capacity of the mooring lines.
Study of brittle/ductile layering effect on fracture geometry and mechanical behavior by tri-axial testing
(2015-05) Yue, Kaimin; Olson, Jon E.; Foster, Jon T
Hydraulic fracturing has been a widely used technology to produce hydrocarbon from shale plays. A better understanding of the fracturing process is needed to improve oil and gas production. Understanding fracture height growth is one of the main concerns and fracture systems are usually influenced by the presence of layers with contrasting mechanical properties. This study uses a tri-axial test to investigate the fracture geometry and mechanical behavior of brittle/ductile layered samples. Synthetic hydrostone is used as brittle rock, and uncemented sand is used to mimic ductile rock. A series of experiments evaluate the effect of loading speed, confining stress, and layer thickness on the mechanical behavior and fracture geometry of the layered samples. A discrete element method is also used to calculate the mechanical behavior of layered samples and investigate the layering effect. The tri-axial test results show that the ductile/brittle multilayer becomes more brittle by increasing the number of layers. According to the results, the loading rate has less effect on thicker layer samples, and the samples are more ductile under higher confining stress. A sensitivity analysis using the discrete element method includes interface properties, number of layers, layer thickness, boundary conditions and edge effects. The results show that the mechanical behavior of brittle/ductile layered samples is highly dependent on the interface properties as well as on the number of layers. The layered samples become stronger and more brittle by increasing interface roughness and friction as well as the number of layers. This work will help better understand brittle ductile behavior of rocks and provide guidelines for the investigation of the brittle ductile layering effect on fracture height containment.
Three-Dimensional Printing of Layered Machinable Ductile Carbide 80
(2000) D'Costa, D.J.; Dimovski, S.D.; Lin., F.; El-Raghy, T.; Barsoum, M.W.; Sun, W.
Ti3SiC2 carbide represents a new class of ceramics with excellent electrical and mechanical properties. This paper presents our preliminary studying on using 3D printing technique, combining with cold isostatic pressing and sintering processing to prototype Ti3SiC2 carbide components. The basic mechanical, electrical and thermal properties of Ti3SiC2 carbide material will be reviewed. Results in die and mold-free 3D printing processing of Ti3SiC2 carbide prototyping will be reported. The SEM characterization of the prototypes and the correlation with the processing parameters will be presented