Search NASA⌕ Search

SEARCH · Search NASA

Results for “FRACTURES”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

The Effect of Neutron Irradiation on the Fracture Toughness of Graphite

As part of our irradiated graphite recycle program a small quantity of PCEA grade graphite was irradiated in the High Flux Isotope Reactor (HFIR) at ORNL. The graphite will provide the raw material for future recycle experiments. The geometry of the irradiated graphite allowed us to study the effects of neutron irradiation on the Critical Stress Intensity Factor, KIc, of graphite. The specimens where irradiated in two groups of 6 at an irradiation temperature of 900 C in rabbit capsules to doses of 6.6 and 10.2 DPA, respectively. Following a full suite of pre-and post-irradiation examination, which included dimensions, mass, electrical resistivity, elastic constants, and thermal expansion (to 800 C) the samples were notched and tested to determine their KIc using the newly approved ATSM test method for SENB fracture toughness of graphite. Here we report the irradiation induced changes in the dimensions, elastic constants, resistivity, and coefficient of thermal expansion of PCEA graphite. Moreover, irradiation induced changes in the Critical Stress Intensity Factor, KIc, or fracture toughness, are reported and discussed. Very little work on the effect of neutron irradiation on the fracture toughness of graphite has previously be performed or reported.

fracture toughness↗
DOE OSTI2014

Determining Ductile Fracture Toughness in Metals

Ductile fracture toughness determination, such as the J-integral versus crack growth resistance (J-R) curve, is a useful tool for evaluating material structural integrity in the presence of pre-existing defects. The J-R curve represents a way to calculate the work (energy) per unit fracture surface area needed to drive the crack growth. A typical J-R curve is shown in Fig. 1 from which the material fracture toughness near the initiation of stable crack growth (Jq) can be derived. In addition, tearing modulus (TR), representing the material resistance to stable crack growth, can be calculated based on the slope of the J-R curve between two exclusion lines (red dashed lines in Fig. 1). Since the introduction of the J-R curve, extensive efforts have been continuously devoted to develop simplified and reliable methods for determining the material J-R curve. This article briefly reviews three widely-used J-R curve test methods in metals, i.e. elastic unloading compliance (EUC), normalization, and direct current potential drop (DCPD). The main difference in these methods relates to the determination of the crack size. More details of performing the J-R curve determination can be found in ASTM standard E1820-11.

DCPD↗
DOE OSTI2014

Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

02 PETROLEUM↗
DOE OSTI2012

Simulation of film and droplet flow on wide aperture fractures using Smoothed Particle Hydrodynamics

Simulation of flow in fractured porous media represents a challenge due to the highly non-linear dynamics of fluid-air interfaces. Here we present small-scale flow simulations on wide aperture fractures using a modified three-dimensional multiphase SPH model \cite{Tartakovsky2005}. The model is modified to include the effects of random thermal noise. The model is able to reproduce a wide range of wetting conditions and Reynolds numbers encountered in laboratory experiments using pairwise fluid-fluid and solid-fluid interaction forces. Static and transient flow dynamics are compared to empirical and semianalytical solutions: (1) Droplets in a critical state are in agreement with laboratory experiments of \cite{ElSherbini2004}. (2) Well-defined random thermal noise is introduced via the fluctuation-dissipation theorem and its effect on dynamics of droplets in a critical state is investigated. (3) Transient flow dynamics on dry surfaces are validated using the dimensionless relationships established by \cite{Podgorski2001} and compared to (4) dynamics on prewetted surfaces where flow velocities are shown to be nearly tripled. Finally we establish flow regimes and occurrence of trailing films on initially dry fracture surfaces based on dimensionless scaling parameters and Reynolds numbers.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2016

Complex fracture nucleation and evolution with nonlocal elastodynamics

In this study, a mechanical model is introduced for predicting the initiation and evolution of complex fracture patterns without the need for damage variable or law. The model, a continuum variant of Newton's second law, uses integral rather than partial differential operators where the region of integration is over finite domain. The force interaction is derived from a novel nonconvex strain energy density function, resulting in a nonmonotomic material model. The resulting equation of motion is proved to be mathematically well-posed. The model has the capacity to simulate nucleation and growth of multiple, mutually interacting dynamic fractures. In the limit of zero region of integration, the model reproduces the classic Griffith model of brittle fracture. The simplicity of the formulation avoids the need for supplemental kinetic relations that dictate crack growth or the need for an explicit damage evolution law.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Modeling Graphite Behavior (Fracture and Oxidation)

Purpose of this work Oxidation modeling Oxidation of full-scale components Local properties in oxidized components Graphite fracture strength Phase field fracture modeling Microstructurally informed fracture model IG-110 tensile results and comparison to experiment Work in progress and future work

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

West Flank Coso FORGE: Natural Fracture Data

Natural fracture data from wells 33-7, 33A-7,52A-7, 52B-7 and 83-11 at West Flank. Fracture orientations were determined from image logs of these wells (see accompanying submissions). Data files contain depth, apparent (in wellbore reference frame) and true (in geographic reference frame) azimuth and dip, respectively.

15 GEOTHERMAL ENERGY↗
DOE OSTI2022

Utah FORGE Well 16A(78)-32 Stimulation DFN Fracture Plane Evaluation and Data

This dataset includes files used to fit planar fractures through the preliminary earthquake catalogs of the three stages of the April 2022 well 16A(78)-32 stimulation which is linked bellow. These planar features have been used to update the FORGE reference Discrete Fracture Network (DFN) model. The files are provided to encourage other modelers to use additional workflows to find additional/alternative features. To this end, the dataset includes the cleaned earthquake catalog data translated to the FORGE reference model global reference frame, the well trajectory of 16A(78)-32 in those same coordinates, the fit 15 planar features in csv format, and a pdf file with slides illustrating the process used to fit the features. A recorded presentation of this material is available from the October 2022 FORGE Modeling and Simulation Forum which is also linked below.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Utah FORGE 5-2565: Hydrothermal Evolution of Fracture Properties - Workshop Presentation

This is a presentation on the Evolution of Permeability and Strength Recovery of Shear Fractures Under Hydrothermal Conditions project by the U.S. Geological Survey, presented by Dr. David Lockner. The project's objective was to determine how thermal, hydraulic, mechanical, and chemical processes affect the sustainability of fracture networks in geothermal reservoirs and provide strategies for improved EGS techniques that maximize thermal coupling and increase reservoir longevity. This presentation was featured in the Utah FORGE R&D Annual Workshop on September 8, 2023. The workshop provided a valuable opportunity to explore the progress made in each of the 17 Research and Development projects funded under Solicitation 2020-1 which aim to enhance our understanding of the crucial factors influencing the development of Enhanced Geothermal Systems (EGS) reservoirs and resources.

15 GEOTHERMAL ENERGY↗
DOE OSTI2018

Quantitative In Situ Studies of Dynamic Fracture in Brittle Solids Using Dynamic X-ray Phase Contrast Imaging

Here, we demonstrate the use of X-ray phase contrast imaging with sub-microsecond temporal resolution to obtain quantitative visualization of dynamic fracture processes in brittle solids. We examine an amorphous solid (fused silica), a ceramic single crystal (single-crystal quartz), and a polycrystalline ceramic (boron carbide), in the form of single-edge notched specimens loaded using a three-point apparatus at nominal strain rates up to ~800 s -1 . We observe that the crack tip speed for boron carbide is relatively independent of mode I stress intensity factor rate ($\dot{K}$ I ) for these rates of loading, while that of fused silica and single-crystal quartz increases with $\dot{K}$ I . Further, for the amorphous and single crystal cases, we observe the development of a crack tip instability in the form of crack branching as the crack tip speed approaches 45% of the Rayleigh wave speed. This suggests that strain-rate-dependent mechanisms contribute to crack branching. Such mechanisms may, in turn, affect the macroscopic fracture properties of these materials.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Analysis and Visualization of Discrete Fracture Networks Using a Flow Topology Graph

We present an analysis and visualization prototype using the concept of a flow topology graph (FTG) for characterization of flow in constrained networks, with a focus on discrete fracture networks (DFN), developed collaboratively by geoscientists and visualization scientists. Our method allows users to understand and evaluate flow and transport in DFN simulations by computing statistical distributions, segment paths of interest, and cluster particles based on their paths. The new approach enables domain scientists to evaluate the accuracy of the simulations, visualize features of interest, and compare multiple realizations over a specific domain of interest. Geoscientists can simulate complex transport phenomena modeling large sites for networks consisting of several thousand fractures without compromising the geometry of the network. However, few tools exist for performing higher-level analysis and visualization of simulated DFN data. The prototype system we present addresses this need. Here, we demonstrate its effectiveness for increasingly complex examples of DFNs, covering two distinct use cases - hydrocarbon extraction from unconventional resources and transport of dissolved contaminant from a spent nuclear fuel repository.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Utah FORGE: Updated FMI Fracture Log from Well 16A(78)-32

This dataset consists of an Excel spreadsheet detailing the fracture picks from a reinterpretation of the formation micro-imaging (FMI) log from Utah FORGE well 16A(78)-32. The provided information details fracture location, geometry, and type. Also included here is a link to the original raw and processed FMI logs, as well as other data from the 2021 well logging.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

A Systematic Interpretation of Subsurface Proppant Concentration from Drilling Mud Returns: Case Study from Hydraulic Fracturing Test Site (HFTS-2) in Delaware Basin

The aim of this study is generation and validation of a proppant log using analysis of drilling mud returns for child wells. Proppant log provides qualitative as well as quantitative insights into spatial distribution of proppant sand particles from prior stimulation of parent wells. While the basic methodology was developed and formalized during analysis of material collected from through fracture cores at Hydraulic Fracturing Test Site in Midland Basin (HFTS – 1), the test wells at HFTS – 2 in the neighboring Delaware Basin allowed the opportunity to validate the workflow on actual mud return samples from subsurface. As a child well is being drilled, periodic mud return samples are collected at the rig site and preserved for analysis. The workflow involves systematic cleaning of the samples including various steps such as washing, drying and segregation of samples into relevant size fractions of interest (< Mesh 20) based on specifications of pumped sand during stimulation of the parent well. Clean samples are imaged using high resolution transparency scanning. Scan images are then systematically analyzed for particles of interest using computer vision techniques. Sample counts are further validated using elemental analysis of smaller sub-samples at various depths of interest. This step is necessary to isolate proppant versus other naturally occurring minerals such as sulphates and carbonates which show similar optical properties. We successfully correlated proppant distribution against the existing parent well and validated propped versus relatively un-propped zones for a child well at the test site. The advantage of testing the proppant log concept at the HFTS – 2 site is the plethora of additional diagnostic data that is available to validate our primary observations. We can correlate spatial proppant distribution against variability in stimulation response based on independent observations such as image logs, microseismic attributes as well as DAS response, all of which tend to corroborate one another. One of our significant successes was being able to describe varying degrees of impact of the parent well along the lateral length of a stimulated child well. Our workflow represents a systematic and one-of-a-kind interpretation of spatial proppant distribution while drilling child wells. This provides unique opportunities to better understand the current state of the Downloaded from http://onepetro.org/URTECONF/proceedings-pdf/21URTC/2-21URTC/D021S031R003/2477415/urtec-2021-5189-ms.pdf/1 by Carol Worster on 28 February 2022 URTeC 5189 2 reservoir being targeted including zones which are likely more drained relative to others and how the planned completion of the child well can be improved. Lastly, this log can be useful is validating optimal well spacing in relatively new fields under development.

58 GEOSCIENCES↗
DOE OSTI2015

Modification of the Local Cubic Law of fracture flow for weak inertia, tortuosity, and roughness

The classical Local Cubic Law (LCL) generally overestimates flow through real fractures. We thus developed and tested a modified LCL (MLCL) which takes into account local tortuosity and roughness, and works across a low range of local Reynolds Numbers. The MLCL is based on (1) modifying the aperture field by orienting it with the flow direction and (2) correcting for local roughness changes associated with local flow expansion/contraction. In order to test the MLCL, we compared it with direct numerical simulations with the Navier-Stokes equations using real and synthetic three-dimensional rough-walled fractures, previous corrected forms of the LCL, and experimental flow tests. The MLCL performed well and the effective errors (δ) in volumetric flow rate range from -6.7% to 13.4% with an arithmetic mean of |δ| (<|δ|>) equal to 3.7%. The MLCL is more accurate than previous modifications of the LCL. We also investigated the error associated with applying the Cubic Law (CL) while utilizing modified aperture field. The δ from the CL ranges from -14.2% to 11.2%, with a slightly higher <|δ|> = 6.1% than the MLCL. The CL with the modified aperture field considering local tortuosity and roughness may also be sufficient for predicting the hydraulic properties of rough fractures.

58 GEOSCIENCES↗
DOE OSTI2024

In Situ Study on Fracture Behavior of Thick-Section Friction Stir-Welded AA 5083 Alloy

Friction stir welding (FSW) produces a gradient microstructure with distinct metallurgical zones. Here, the present study focuses on characterizing the fracture behavior during uniaxial loading across thick-section FSW joint in nonheat-treatable 5083 aluminum alloy. The hardness variation is linked to microstructural features across the weld zones through correlative microscopy. Notably, the heat-affected zone (HAZ) exhibits a lower hardness of 75 HV, while the thermomechanically affected zone (TMAZ) and stir zones (SZ) display a hardness of around 79HV. A marginal difference in hardness in HAZ prompts strain localization in HAZ on the advancing side of the weld, resulting in offset in fracture from the SZ, which is captured through in situ monitoring of the tensile test. Further, the postdeformation analysis reveals crack propagation along the maximum shear stress plane due to the coalescence of microvoids resulting from the fracturing and debonding of second-phase particles. Overall, this study provides valuable insight for optimizing the FSW process of AA 5083 alloy for thick-section applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

An Improved Fracture Mechanics-Informed Multiscale Thermomechanical Damage Model for Ceramic Matrix Composites

This paper extends recent work done by the authors in modeling length scale-dependent damage behavior of ceramic matrix composites (CMCs) to include effects of local anisotropy introduced by matrix cracking. This model captures scale-dependent damage initiation and propagation behavior of the brittle matrix by employing internal state variable (ISV) theory within a multiscale modeling framework to obtain damaged matrix stress/strain constitutive relationships at each length scale. The damage ISV captures the effects of matrix cracking and growth by using fracture mechanics and the self-consistent scheme to determine the reduced stiffness of the cracked matrix. Matrix cracks, which activate when stress intensity factors near manufacturing induced cavities exceed the fracture toughness of the material, are assumed to be transversely isotropic in the plane of the crack, and matrix anisotropy occurs when the damaged stiffness tensor is rotated from the crack plane to the global axes. The crack progression and temporal evolution of the damage ISV are governed by fracture mechanics and crack growth kinetics. The model effectively captures first matrix cracking, which is the first significant deviation from linear elasticity. The nonlinear predictive capabilities of the material model are demonstrated for monolithic silicon carbide (SiC) and a 2D woven five-harness satin (5HS) carbon fiber SiC matrix (C/SiC) CMC.

Skinner, Travis↗
DOE OSTI2016

Percutaneous CT and Fluoroscopy-Guided Screw Fixation of Pathological Fractures in the Shoulder Girdle: Technical Report of 3 Cases

ObjectiveTo review our initial experience with percutaneous CT and fluoroscopy-guided screw fixation of pathological shoulder-girdle fractures.Materials and MethodsBetween May 2014 and June 2015, three consecutive oncologic patients (mean age 65 years; range 57–75 years) with symptomatic pathological shoulder-girdle fractures unsuitable for surgery and radiotherapy underwent percutaneous image-guided screw fixation. Fractures occurred through metastases (n = 2) or a post-ablation cavity (n = 1). Mechanical properties of osteosynthesis were adjudged superior to stand-alone cementoplasty in each case. Cannulated screws were placed under combined CT and fluoroscopic guidance with complementary radiofrequency ablation or cementoplasty to optimise local palliation and secure screw fixation, respectively, in two cases. Follow-up was undertaken every few weeks until mortality or most recent appointment.ResultsFour pathological fractures were treated in three patients (2 acromion, 1 clavicular, 1 coracoid). Mean size of associated lesion was 2.6 cm (range 1–4.5 cm). Technical success was achieved in all cases (100 %), without complications. Good palliation and restoration of mobility were observed in two cases at 2–3 months; one case could not be followed due to early post-procedural oncologic mortality.ConclusionPercutaneous image-guided shoulder-girdle osteosynthesis appears technically feasible with good short-term efficacy in this complex patient subset. Further studies are warranted to confirm these promising initial results.

62 RADIOLOGY AND NUCLEAR MEDICINE↗