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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.

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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Final Report for LDRD: The Effect of Proppant Placement on Closure of Fractured Shale Gas Wells

The recent boom in the oil and natural gas industry of hydraulic fracture of source rocks has caused a new era in oil and gas production worldwide. However, there are many parts of this process that are poorly understood and thus hard to control. One of the few things that can be controlled is the process of injection to create the fractures in the subsurface and the subsequent injection of proppants to maintain the permeability of the fractured formation, allowing hydrocarbons to be extracted. The goal of this work was to better understand the injection process and resulting proppant distribution in the fracture through a combination of lab-scale experiments and computational models.

02 PETROLEUM↗
DOE OSTI2019

Post-Irradiation Fracture Toughness Characterization of Generation II FeCrAl Alloys

Currently, the handbook on FeCrAl material properties contains only limited data regarding the fracture toughness properties of any FeCrAl alloy, let alone alloys currently under investigation within the Advanced Fuels Campaign (AFC) such as the Oak Ridge National Laboratory (ORNL) derived FeCrAl alloys. Unirradiated datasets developed both by ORNL and previously within literature using Charpy V-notch specimens to determine the ductile to brittle transition temperature (DBTT) showed key findings including (i) increasing Al and/or Cr content can raise the DBTT of FeCrAl alloys, (ii) DBTT values can typically reside at or above room temperature for FeCrAl alloys, and (iii) grain size and residual strain can have an effect on the fracture properties. These results suggest that the fracture toughness of FeCrAl alloys may be a factor in its deployment for nuclear power applications, but no studies have been completed prior regarding the DBTT or fracture toughness of FeCrAl alloys after neutron irradiation, especially for the leaner Cr content alloys currently under investigation as candidate alloys for light water reactor (LWR) cladding. Taken in isolation, embrittlement of a cladding alloy during service has no bearing on possible licensure. Hydriding of zirconium cladding alloys is well understood to result in significant embrittlement. Furthermore, mechanical failure of irradiated cladding containing fuel pellets occurs at far higher stresses than defueled cladding samples because the presence of the fuel toughens the fuel rod. Despite this absence of direct relevance to licensure, radiation embrittlement is a fundamental structure-property evolution that should be understood to guide further development of FeCrAl alloys. Licensure of FeCrAl incorporates far more complex system behaviors that will not be possible until larger quantities of fueled irradiated rodlets are available.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Fracture Toughness of Microstructural Gradients

Traditional singularity-based fracture mechanics theories rely on their ability to infer the crack tip driving force (local field) by surveying macroscopic physical magnitudes far from the crack tip (far field). This key capability allows engineers to employ nominal forces or displacements to estimate the potential for stable or unstable crack growth. In the case of heterogeneous or anisotropic materials, traditional fracture approaches are not fully theoretically sound and applications rely on extrapolating methodologies with ad-hoc corrections. This Express Laboratory Directed Research and Development (ELDRD) program employed mesoscale-sensitive finite element simulations to assess the impact of grain size and texture on the crack tip behavior. A dislocation-based crystal plasticity model conveys grain size effects by computing the constraint on dislocation cell structures. We assessed the effects of microstructural variability on multiple displacement-based measurements of the fracture driving forces for crack opening (Mode I) and sliding (Mode II). We also consider multiple microstructural realizations of single phase metals undergoing ductile failure. The results show that grain size and texture affect the applied fracture driving force and can induce a significant Mode II deformation under force and displacement control, which is completely neglected in homogeneous models. A large variability in driving forces upon identical far field applied conditions is attributed to a buffering effects of the microstructure. Furthermore, crack mouth opening displacement is almost insensitive to microstructure, which suggests that experimental measurements using such a magnitude (e.g., plastic hinge model) may underestimate local crack tip driving force variability.

42 ENGINEERING↗
DOE OSTI2021

Understanding Discrete Fracture Networks Through Spectral Graph Theory

Discrete Fracture Network models (DFNs) are used to simulate fluid flow and particle transport through fracture networks in low permeability rock. Understanding these processes are essential in many subsurface applications, such as environmental restoration of contaminated fractured media, CO 2 sequestration, detection of low-level nuclear tests, and hydrocarbon extraction. Compared with other models, DFNs allow for incorporation of a wider range of network characteristics but have substantially greater computation cost. These networks can be represented with graphs, allowing the use of graph theory tools to study the networks. I used Python to simulate flow and transport on a range of DFNs and analyzed these networks using methods from network analysis and spectral graph theory. My purpose was to find ways to gain insight about flow and transport on DFNs using these graph representations, bypassing the computationally intensive meshing typically required. My work is still in progress, but I have discovered several interesting trends and patterns that I believe could be useful towards my goal. If I am able to bring these results to fruition, they will aid subsurface geologists in extracting flow and transport information about fracture networks more efficiently.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Fracture Toughness Characterization of Generation II FeCrAl Alloys after ~18 dpa Irradiation

FeCrAl alloys are promising candidate materials for the accident tolerant fuel (ATF) cladding applications due to their excellent corrosion resistance to the elevated temperature steam environment. Currently, the handbook on FeCrAl material properties contains only limited data regarding the fracture toughness properties of any FeCrAl alloy. This includes alloys currently under investigation within the Advanced Fuels Campaign (AFC) at Oak Ridge National Laboratory (ORNL). In this project, a series of irradiation capsules have been irradiated in the High Flux Isotope Reactor (HFIR) at ORNL with two Generation II FeCrAl candidate alloys, i.e., C06M and C36M, to assess the fracture response of these alloys after neutron irradiation. These alloys represent the “book-end” compositions for C26M, the alloy currently being developed as the leading candidate for LWR cladding. A total of six irradiation capsules were irradiated in HFIR at target temperatures of 200°C, 330°C, and 500°C up to target damage doses of 8 displacements per atom (dpa) and 16 dpa. These damage doses represent the expected middle and end of life damage levels for typical LWR cladding while the irradiation temperature regimes will provide insight into the role of varying microstructural features on the fracture toughness properties of neutron irradiated FeCrAl alloys. To date, irradiation of all capsules has been completed in HFIR. This report summarizes the latest results of microhardness and fracture toughness PIE for the 16 dpa capsules (FCAB2, FCAB4, and FCAB6), for which the measured irradiation conditions were: 204°C/17.6dpa, 343°C/18.3dpa, and 507°C/18.6dpa. The main conclusions of this study can be summarized as follows: 1) After the 204°C/17.6dpa irradiation, both C06M and C36M exhibited significant irradiation hardening and embrittlement 2) After the 343°C/18.3dpa irradiation, both C06M and C36M exhibited small irradiation hardening without irradiation embrittlement 3) After the 507°C/18.6dpa irradiation, both C06M and C36M exhibited irradiation softening without irradiation embrittlement 4) Comparing the microhardness and Master Curve reference temperature T 0q before and after neutron irradiation, we did not observe a linear correlation between the two parameters for both C06M and C36M. This should be mainly due to a flat response of the Master Curve reference temperature T 0q to the irradiations at 166-204°C and 315-343°C ranges 5) C06M showed a lower T 0q , meaning better toughness, than C36M at the unirradiated condition and such trend was kept even after neutron irradiation except for the 166-204°C irradiation where both materials had similar T 0q . 6) In terms of hardening and embrittlement, the irradiation effect on both C06M and C36M appeared to saturate after an irradiation dose of 7 dpa.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Integrated Multiphysics Modeling of Environmentally Assisted Brittle Fracture

Brittle materials, such as cement, compose major portions of built infrastructure and are vulnerable to degradation and fracture from chemo-mechanical effects. Currently, methods of modeling infrastructure do not account for the presence of a reactive environment, such as water, on the acceleration of failure. Here, we have developed methodologies and models of concrete and cement fracture that account for varying material properties, such as strength, shrinkage, and fracture toughness due to degradation or hydration. The models have been incorporated into peridynamics, non-local continuum mechanics methodology, that can model intersecting and branching brittle fracture that occurs in multicomponent brittle materials, such as concrete. Through development of new peridynamic capabilities, decalcification of cement and differential shrinkage in clay-cement composites have been evaluated, along with exemplar problems in nuclear waste cannisters and wellbores. We have developed methods to simulate multiphase phenomena in cement and cement-composite materials for energy and infrastructure applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Physically rigorous reduced-order flow models of fractured subsurface environments without explosive computational cost

Fractured media models comprise discontinuities of multiple lengths (e.g. fracture lengths and apertures, wellbore area) that fall into the relatively insignificant length scales spanning millimeter-scale fractures to centimeter-scale wellbores in comparison to the extensions of the field of interest, and challenge the conventional discretization methods imposing highly-fine meshing and formidably large numerical cost. By utilizing the recent developments in the finite element analysis of electromagnetics that allow to represent material properties on a hierarchical geometry, this project develops computational capabilities to model fluid flow, heat conduction, transport and induced polarization in large-scale geologic environments that possess geometrically-complex fractures and man-made infrastructures without explosive computational cost. The computational efficiency and robustness of this multi-physics modeling tool are demonstrated by considering various highly-realistic complex geologic environments that are common in many energy and national security related engineering problems.

42 ENGINEERING↗
DOE OSTI2023

Closing the loop between in-situ stress complexity and EGS fracture complexity

The goal of the project is to employ a combination of high-fidelity simulations and true-triaxial block fracturing tests at high temperature to explore the intricate relationship between in-situ stress and hydraulic fracture patterns and better characterize the in-situ stress at Utah FORGE. Laboratory experiments are used to validate numerical models and better understand the impact of various parameters (e.g., temperature, well orientation, stress, etc) on the hydraulic fracture nucleation process in EGS. The project will have a significant impact as it will (1) improve the characterization of the in-situ stress field at FORGE; (2) demonstrate how high-fidelity modeling tools can be employed to analyze data for EGS; (3) provide a unique set of high-temperature hydraulic fracturing experimental results for EGS to help identifying the most important components for in-situ stress estimation and to validate the current in-situ stress estimation theory and establish a strong foundation for proposing a new one; (4) provide a validated set of numerical tools in an open source simulation framework (GEOS) that can be used to model EGS.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

Understanding Water Controls on Shale Gas/Oil Mobilization into Fractures (FY 2019-2021(FY2022, No Cost Extension), Final Report)

The large volumes of injected and produced water, and costs associated with both hydraulic fracturing fluids and produced water treatment motivate development of hydraulic fracturing strategies that use water more efficiently. The overall objective of this project is to improve understanding on how water is distributed within unconventional shales during and after hydraulic fracturing in order to provide a more rational basis for reservoir stimulation strategies that increase hydrocarbon recovery per unit of water used. The strong capillary imbibition of water into shale matrix pores and immiscibility with hydrocarbons makes it highly desirable to reduce water use during reservoir development. Given the importance, and competing influences of capillarity and gravity in controlling water in fractured porous media, this project also seeks to understand how these factors interact to obstruct or allow gas flow.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2024

Fracture Network Prediction Using Physics-based Machine Learning Algorithms

In recent years, systematic CO2 injection into geological reservoirs across the U.S. has gained traction as a strategy to mitigate greenhouse gas emissions. This approach necessitates precise monitoring to ensure secure containment, minimize risks, and optimize storage management. Our study leverages machine learning (ML) techniques to advance the understanding of CO2 injection processes, focusing on the Illinois Basin. Over a three-year injection period, we analyzed microseismic data, identifying 19 temporal intervals with significant bottom-hole pressure changes. By partitioning microseismic events into these intervals and estimating b-values, we revealed over 100 clusters of events related to fracture initiation or reactivation. Advanced spatial analysis highlighted horizontally-oriented fractures along the NNW-SSE axis. This quantification of fracture networks informs dynamic injection scheduling, work-over strategies, and risk assessments, enhancing carbon capture, utilization, and storage (CCUS) operations. Additionally, our methodology offers valuable insights for oil and gas operations and geothermal development, supporting fracture-based monitoring and risk mitigation.

Kumar, Abhash↗
DOE OSTI2025

Characterizing Stress Roughness at Utah FORGE Through Simulation of Hydraulic Fracture Growth During 16A Stage 3 Stimulation

In most geologic formations, the vertical gradient of the minimum horizontal stress (𝜎 h ) exceeds the hydrostatic gradient, often driving hydraulic fractures to propagate upward. However, observations indicate that the upward growth of real hydraulic fractures is less pronounced than theoretical predictions based on smoothly varying 𝜎 h fields. In fact, the layered structure of sedimentary rocks hinders fracture propagation across layers, partially explaining the limited height growth observed in practice (Zoback et al., 2022). While crystalline rocks lack the pervasive layered fabric of sedimentary formations, they still possess structural fabric formed over their geologic history, resulting in inherently "rough" in situ stress fields. Recent studies have identified another key factor: the "roughness" of in situ stress, characterized by temporal, relatively short-wavelength fluctuations superimposed on the overall stress gradient. This stress roughness leads to apparent toughness anisotropy, where the vertical toughness appears significantly larger than the horizontal toughness (P. Fu et al., 2019; Dontsov & Suarez-Rivera, 2021). Neglecting the effects of rock fabric and stress roughness can yield inaccurate predictions of hydraulic fracture geometry and growth rates at larger length scales.

58 GEOSCIENCES↗
DOE OSTI2024

Analysis of Deformation and Fracture Mechanisms in the Harvested High-Dose Baffle-Former Bolt with Stress-Corrosion Cracks Formed While in Service

This report presents the results of advanced mechanical testing conducted on miniature tensile specimens excised from an irradiated baffle-former bolt, a commercial pressurized water reactor component. The specimens were extracted from the midsection of the bolt shank, where the estimated damage dose reached 23 displacements per atom. The mechanical testing included the following tests: (1) conventional tensile testing at room temperature, augmented by digital image correlation (DIC) to enable noncontact strain measurements, and (2) in situ tensile testing within a scanning electron microscopy (SEM) instrument equipped with energy-dispersive x-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) detectors to evaluate active deformation and fracture mechanisms. Additionally, SEM fractographic analysis revealed alterations in the fracture mechanism from a predominantly ductile fracture in nonirradiated steel to a mixed fracture mode (still dominating ductile and minor cleavage spots) in irradiated specimens derived from the baffle bolts. The findings indicate a complex strain localization behavior for in-service irradiated steel specimens. Beyond conventional necking at the macro scale and defect-free channel formation at the micro scale, DIC results identified the presence of deformation bands approximately 100 μm in width. These bands consist of chains of grains exhibiting elevated local strain levels and may be considered an intermediate or mesoscale level of strain localization. These bands become discernible near the yield stress as localized hot spots, areas of elevated strain, persisting throughout most of the experiment. The formation of mesoscale deformation bands as a strain localization mechanism may exacerbate the defect-free channel formation in irradiated materials, further promoting irradiation-assisted stress corrosion crack initiation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

DEMO-FTES: Development, Monitoring, and Control of Fracture Thermal Energy Storage in Crystalline Rock Formations (CRADA Final Report)

The DEMO-FTES project investigated the feasibility of Fracture Thermal Energy Storage (FTES) as a seasonal energy storage solution in crystalline rock formations. FTES leverages hydraulically induced fractures to exchange heat between circulating fluids and the surrounding rock mass, enabling long-term thermal energy retention due to the high specific heat and low thermal conductivity of rock. This approach has the potential to reduce heating and cooling energy demands and enhance building energy resilience. The project combined dimensional analysis, numerical modeling, laboratory experiments, and meso-scale field tests to evaluate FTES performance and advance its technology readiness level from 3 to 5. Scaling analysis identified key dimensionless parameters governing heat transfer and fluid flow, ensuring laboratory and field tests were representative of larger-scale systems. Numerical simulations using TOUGH and iTOUGH2 frameworks supported experiment design and interpretation, modeling fracture geometry, thermal-hydraulic behavior, and thermo-mechanical coupling. Laboratory tests at EPFL involved creating single and multiple fractures in 25 cm cubic samples of Gabbro and Granite under true triaxial stress.

25 ENERGY STORAGE↗
DOE OSTI2020

Microfluidic Fabrication Techniques for High-Pressure Testing of Microscale Supercritical CO 2 Foam Transport in Fractured Unconventional Reservoirs

Pressure limitations of many microfluidic platforms have been a significant challenge in microfluidic experimental studies of fractured media. As a result, these platforms have not been fully exploited for direct observation of high-pressure transport in fractures. This work introduces microfluidic platforms that enable direct observation of multiphase flow in devices featuring surrogate permeable media and fractured systems. Such platforms provide a pathway to address important and timely questions such as those related to CO 2 capture, utilization and storage. This work provides a detailed description of the fabrication techniques and an experimental setup that may serve to analyze the behavior of supercritical CO 2 (scCO 2 ) foam, its structure and stability. Such studies provide important insights regarding enhanced oil recovery processes and the role of hydraulic fractures in resource recovery from unconventional reservoirs. This work presents a comparative study of microfluidic devices developed using two different techniques: photolithography/wet-etching/ thermal-bonding versus Selective Laser-induced Etching. Both techniques result in devices that are chemically and physically resistant and tolerant of high pressure and temperature conditions that correspond to subsurface systems of interest. Both techniques provide pathways to high-precision etched microchannels and capable lab-on-chip devices. Photolithography/wet-etching, however, enables fabrication of complex channel networks with complex geometries, which would be a challenging task for laser etching techniques. This work summarizes a step-by-step photolithography, wet-etching and glass thermal-bonding protocol and, presents representative observations of foam transport with relevance to oil recovery from unconventional tight and shale formations. In conclusion, this work describes the use of a high resolution monochromatic sensor to observe scCO 2 foam behavior where the entirety of the permeable medium is observed simultaneously while preserving the resolution needed to resolve features as small as 10 μm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Experimental Study of Underground Heat Storage via Hydraulic Fractures

In this study, we present a laboratory setup to test the energy flow in the form of underground heat storage using hydraulic fractures, a so-called Fracture Thermal Energy Storage (FTES) system. In the experiment, de-ionized water is circulated under high pressure through steel tubing automatically heated to a target temperature. The fluid adjusts to the tubing temperature during its flow before entering a production well drilled into a 250 mm edge length block of Zimbabwe Gabbro. The warm fluid then circulates through a previously created hydraulic fracture at mid-height of the block to a production well drilled at the block periphery. External fracture appearances are sealed using an epoxy resin and the production well by a cork of polydimethylsiloxane. In this cork, tubing to an open outlet is glued. We demonstrated through the results of a preliminary heating experiment that we can transfer nearly all of the heat from the circulating fluid to the block. An efficient charging of the thermal battery is achieved. This first-order demonstration is currently under further improvement and serves as a knowledge basis for the upscaling of mid- to large-scale field implementation of FTES systems.

Möri, Andreas↗
NASA NTRS1972

Fracture control procedures for aircraft structural integrity

The application of applied fracture mechanics in the design, analysis, and qualification of aircraft structural systems are reviewed. Recent service experiences are cited. Current trends in high-strength materials application are reviewed with particular emphasis on the manner in which fracture toughness and structural efficiency may affect the material selection process. General fracture control procedures are reviewed in depth with specific reference to the impact of inspectability, structural arrangement, and material on proposed analysis requirements for safe crack growth. The relative impact on allowable design stress is indicated by example. Design criteria, material, and analysis requirements for implementation of fracture control procedures are reviewed together with limitations in current available data techniques. A summary of items which require further study and attention is presented.

Wood, H. A.↗
NASA NTRS1971

On nonlinear effects in fracture mechanics.

Linear elastic treatment of fracture is considered applicable for net section stress up to about 0.8 the uniaxial tensile yield stress. Crack front plastic yield is still small enough to be viewed and treated as a small perturbation to the local crack front elastic stress field. Assuming these same circumstances and adopting the same point of view, an approach is presented for incorporating the nonlinear effects of small scale crack front plastic yield and slow crack extension in determination of the energy release rate and fracture toughness. Deviation from linearity of the load-displacement record in a fracture toughness test offers a quantifiable measure of these effects and is used to calculate the energy release rate. Fracture toughness values for one-eight inch thick 7075-T6 center cracked aluminum sheet are compared with uncorrected values and with values obtained by the Irwin method of plasticity correction.

Liebowitz, H.↗
NASA NTRS1972

An Experimental Investigation of the Effects of Vacuum Environment on the Fatigue Life, Fatigue-Crack-Growth Behavior, and Fracture Toughness of 7075-T6 Aluminum Alloy

Axial load fatigue life, fatigue-crack propagation, and fracture toughness tests were conducted on 0.090-inch thick specimens made of 7075-T6 aluminum alloy. The fatigue life and fatigue-crack propagation experiments were conducted at a stress ratio of 0.02. Maximum stresses ranged from 33 to 60 ksi in the fatigue life experiments, and from 10 to 40 ksi in the fatigue-crack propagation experiments, and fatigue life experiments were conducted at gas pressures of 760, 0.5, 0.05, and 0.00000005 torr. Fatigue-crack-growth and fracture toughness experiments were conducted at gas pressures of 760 and 5 x 10 to the minus 8th power torr. Residual stress measurements were made on selected fatigue life specimens to determine the effect of such stresses on fatigue life. Analysis of the results from the fatigue life experiments indicated that fatigue life progressively increased as the gas pressure decreased. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue crack growth rates were approximately twice as high in air as in vacuum. Fracture toughness data showed there was essentially no difference in the fracture toughness of 7075-T6 in vacuum and in air.

Hudson, C. M.↗