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You searched for subject:(Mixed mode propagation). Showing records 1 – 3 of 3 total matches.

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University of Texas – Austin

1. Lee, Hunjoo Peter. Fracture propagation in naturally fractured reservoirs.

Degree: PhD, Petroleum Engineering, 2015, University of Texas – Austin

Investigations of hydrocarbons in tight formations require understanding of hydraulic fracturing in order to optimize the production and recovery of oil and natural gas. The classic description of hydraulic fracture is a single bi-wing planar feature, however, field observations show that hydraulic fracture growth in naturally fractured formations like shale is complex. Lack of knowledge concerning the remote stress impact and the interaction with planes of weakness on the fracture propagation trajectory leads to inaccurate predictions of the fracture geometry and the surface area required for the production estimation. Most studies in engineering mechanics extended the standard mixed-mode fracture propagation models, based on the near-tip approximations, to include the impact of the tensile crack-parallel stress on the fracture propagation path. However, for fractures in the subsurface, the remote stress is compression, and internal fluid pressure or frictional stress become important in the near-tip stress field and the propagation trajectory. The Modified Maximum Tangential Principal Stress criterion (MMTPS-criterion) was introduced to address and evaluate the remote and internal crack stresses in the propagation path. The predictions of the fracture propagation angles by the MMTPS-criterion agreed with published experimental results of fractures propagating under both tensile and compressive external loads. In addition, the predictions matched well with uniaxial compression tests on hydrostone samples with the critical radial distance, defined by the process zone size, for open fractures that satisfy the Small Scale Yielding conditions. For short open fractures, a larger critical radial distance was required to correspond with the experimental results. The MMTPS-criterion was also capable of predicting lower propagation angles for closed cracks with higher friction coefficients. Preexisting discontinuities in shale, including natural fractures and bedding, act as planes of weakness that divert fracture propagation. To investigate the influence of weak planes on hydraulic fracture propagation, I performed Semi-Circular Bend (SCB) tests on Marcellus shale core samples containing calcite-filled natural fractures (veins). The approach angle of the induced fracture to the veins and the thickness of the veins had a strong influence on propagation. As the approach angle became more oblique to the induced fracture plane, and as the vein got thicker, the induced fracture was more likely to divert into the vein. Microstructural analysis of tested samples showed that the induced fracture propagated in the middle of the vein rather than the interface between vein and the rock matrix. Cleavage planes and fluid inclusion trails in the vein cements exerted some control on the fracture path. By combining the experimental results with theoretical fracture-mechanics arguments, the fracture toughness of the calcite veins was estimated to range from 0.99 MPa [square root of m] to 1.14 MPa [square root of m], depending on the… Advisors/Committee Members: Olson, Jon E. (advisor), Sharma, Mukul M (committee member), Prodanović, Maša (committee member), Gale, Julia F.W. (committee member), Holder, Jon T (committee member), Schultz, Richard A (committee member).

Subjects/Keywords: Fracture interaction; Mixed-mode propagation

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APA (6th Edition):

Lee, H. P. (2015). Fracture propagation in naturally fractured reservoirs. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/63893

Chicago Manual of Style (16th Edition):

Lee, Hunjoo Peter. “Fracture propagation in naturally fractured reservoirs.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed October 16, 2019. http://hdl.handle.net/2152/63893.

MLA Handbook (7th Edition):

Lee, Hunjoo Peter. “Fracture propagation in naturally fractured reservoirs.” 2015. Web. 16 Oct 2019.

Vancouver:

Lee HP. Fracture propagation in naturally fractured reservoirs. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2019 Oct 16]. Available from: http://hdl.handle.net/2152/63893.

Council of Science Editors:

Lee HP. Fracture propagation in naturally fractured reservoirs. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/63893

2. Tran, Bao Viet. Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material.

Degree: Docteur es, Mécanique, génie mécanique, génie civil, 2010, Université Paris-Est

On s'intéresse plus particulièrement à la modélisation du comportement d'un matériau hétérogène méso-fissuré (béton, roche,...), soumis à une sollicitation thermo-hydro-mécanique avec prise en compte du couplage géométrique. Pour conduire cette étude, on s'appuie notamment sur les approches micro-mécaniques du comportement des milieux méso-fissurés non saturés développées depuis quelques années au Laboratoire des Matériaux et des Structures du Génie Civil - Ur Navier - Université Paris Est. Le milieu fissuré non saturé traité ici est constitué d'une matrice solide homogène élastique linéaire et de fissures connectées saturées par deux fluides immiscibles : un liquide et un gaz séparés par une surface capillaire. La fissure est traditionnellement considérée comme une cavité ellipsoïdale (cas 3D) ou elliptique (cas 2D) dont le rapport d'aspect tend vers zéro. Deux morphologies typiques de matériau sont considérés dans ce travail : la situation où les fissures sont toutes orientées dans la même direction et la situation où les fissures possèdent des orientations aléatoires. Dans une première étape, on rappelle brièvement les résultats disponibles concernant la modélisation des fissures non saturées par des cavités ellipsoïdales aplaties. A la fin de cette première partie, on complète les résultats déjà disponibles en étudiant l'influence de l'histoire de chargement sur la réponse de matériau. Dans une deuxième étape, on s'attache à valider une partie des résultats obtenus en utilisant une description des efforts capillaires dans les fissures par une précontrainte homogène en seréférant aux solutions analytiques exactes disponibles dans la littérature permettant de décrire le comportement d'une fissure isolée au sein d'une matrice élastique. Dans une troisième étape, on s'intéresse aux phénomènes de propagation des fissures en condition non saturée. Les lois de propagation sous critique et le phénomène de branchement des fissures sont également prises en compte dans cette approche. La dernière partie de la thèse concerne l'influence de la température sur le comportement des milieux poreux non saturés

The main topic of my work is the development of a micromechanical model for the behaviour of unsaturated mesocracks in media (concrete, rock...) in which the thermo-hydro-mechanical loadingsand thermo-hydro-mechanical couplings are taken into account. For this, we used the micromechanical approach model of behaviour of cracked porous media recently developed at LMSGC. My thesis is focused on the equilibrium configurations of a porous material whose pore space is saturated by a vapour and a liquid phase. The behaviour of an elastic medium containing unsaturated mesocracks is studied in the framework of a micromechanical approach. The cracks are filled by two immiscible fluids, namely a liquid and a gas, separated by a capillary interface. Furthermore, it is assumed that the set of cracks constitutes a connected network ; the capillary pressure is uniform over a representative elementary volume. The cracks are modelled as…

Advisors/Committee Members: Chateau, Xavier (thesis director).

Subjects/Keywords: Méthode d'homogénéisation; Problèmes non-linéaires; Micro-structures; Capillarité; Milieux poreux non saturés; Mécanique de la rupture; Propagation sous critique; Propagation en mode mixte; Homogenization methods; Non-linear effect; Microporomechanics; Microstructure; Capillarity; Unsaturated porous media; Linear elastic fracture mechanics; Mixed mode fracture

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Tran, B. V. (2010). Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material. (Doctoral Dissertation). Université Paris-Est. Retrieved from http://www.theses.fr/2010PEST1093

Chicago Manual of Style (16th Edition):

Tran, Bao Viet. “Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material.” 2010. Doctoral Dissertation, Université Paris-Est. Accessed October 16, 2019. http://www.theses.fr/2010PEST1093.

MLA Handbook (7th Edition):

Tran, Bao Viet. “Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material.” 2010. Web. 16 Oct 2019.

Vancouver:

Tran BV. Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material. [Internet] [Doctoral dissertation]. Université Paris-Est; 2010. [cited 2019 Oct 16]. Available from: http://www.theses.fr/2010PEST1093.

Council of Science Editors:

Tran BV. Approche micromécanique du comportement d'un matériau fissuré non saturé : Micromechanical approach of behaviour of a cracked unsaturated material. [Doctoral Dissertation]. Université Paris-Est; 2010. Available from: http://www.theses.fr/2010PEST1093


University of Central Florida

3. Gibson, Jason. Nano-particles In Multi-scale Composites And Ballistic Applications.

Degree: 2013, University of Central Florida

Carbon nanotubes, graphene and nano sized core shell rubber particles have all been extensively researched for their capability to improve mechanical properties of thermoset resins. However, there has been a lack of research on their evaluation for energy absorption in high velocity impact scenarios, and the fundamental mechanics of their failure mechanisms during highly dynamic stress transfer through the matrix. This fundamental research is essential for laying the foundation for improvement in ballistic performance in composite armor. In hard armor applications, energy absorption is largely accomplished through delamination between plies of the composite laminate. This energy absorption is accomplished through two mechanisms. The first being the elongation of the fiber reinforcement contained in the resin matrix, and the second is the propagation of the crack in between the discreet fabric plies. This research aims to fundamentally study the energy absorption characteristics of various nano-particles as reinforcements in thermoset resin for high velocity impact applications. Multiple morphologies will be evaluated through use of platelet, tubular and spherical shaped nano-particles. Evaluations of the effect on stress transfer through the matrix due to the combination of nano sized and micro scale particles of milled fiber is conducted. Three different nano-particles are utilized, specifically, multi-walled carbon nanotubes, graphene, and core shell rubber particles. The difference in surface area, aspect ratio and molecular structure between the tube, platelet and spherical nano-particles causes energy absorption through different failure mechanisms. This changes the impact performance of composite panels enhanced with the nanoparticle fillers. Composite panels made through the use of dispersing the various nano-particles iv in a non-contact planetary mixer, are evaluated through various dynamic and static testing, including unnotched cantilever beam impact, mixed mode fracture toughness, split-Hopkinson bar, and ballistic V50 testing. The unnotched cantilever beam testing showed that the addition of milled fiber degraded the impact resistance of the samples. Addition of graphene nano platelets unilaterally degraded impact resistance through the unnotched cantilever beam testing. 1.5% loading of MWCNT showed the greatest increase in impact resistance, with a 43% increase over baseline. Determining the critical load for mixed mode interlaminar shear testing can be difficult for composite panels that bend without breaking. An iterative technique of optimizing the coefficient of determination, R2 , in linear regression is developed for objectively determining the point of non-linearity for critical load. This allows for a mathematical method of determination; thereby eliminating any subjective decision of choosing where the data becomes non-linear. The core shell rubber nano particles showed the greatest strain energy release rate with an exponential improvement over the baseline results. Synergistic effects between… Advisors/Committee Members: Gou, Jihua.

Subjects/Keywords: Nanotubes; graphene; ballistics; composite armor; composites; energy absorption; raman spectroscopy; kevlar; split hopkinson bar; unnotched cantilever beam impact; v50; mixed mode interlaminar shear; astm d6671; astm d4812; mil std 662f; nanocomposite; carbon nanotubes; mwcnt; core shell rubber; crack propagation; impact resistance; energy release rate; Engineering; Mechanical Engineering; Dissertations, Academic  – Engineering and Computer Science, Engineering and Computer Science  – Dissertations, Academic

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gibson, J. (2013). Nano-particles In Multi-scale Composites And Ballistic Applications. (Doctoral Dissertation). University of Central Florida. Retrieved from https://stars.library.ucf.edu/etd/2915

Chicago Manual of Style (16th Edition):

Gibson, Jason. “Nano-particles In Multi-scale Composites And Ballistic Applications.” 2013. Doctoral Dissertation, University of Central Florida. Accessed October 16, 2019. https://stars.library.ucf.edu/etd/2915.

MLA Handbook (7th Edition):

Gibson, Jason. “Nano-particles In Multi-scale Composites And Ballistic Applications.” 2013. Web. 16 Oct 2019.

Vancouver:

Gibson J. Nano-particles In Multi-scale Composites And Ballistic Applications. [Internet] [Doctoral dissertation]. University of Central Florida; 2013. [cited 2019 Oct 16]. Available from: https://stars.library.ucf.edu/etd/2915.

Council of Science Editors:

Gibson J. Nano-particles In Multi-scale Composites And Ballistic Applications. [Doctoral Dissertation]. University of Central Florida; 2013. Available from: https://stars.library.ucf.edu/etd/2915

.