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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Fracture Network Influence on Rock Damage and Gas Transport following an Underground Explosion

Simulations of rock damage and gas transport following underground explosions that omit preexisting fracture networks in the subsurface cannot fully characterize the influence of geo-structural variability on gas transport. Previous studies do not consider the impact that fracture network structure and variability have on gas seepage. In this study, we develop a sequentially coupled, axi-symmetric model to look at the damage pattern and resulting gas breakthrough curves following an underground explosion given different fracture network realizations. We simulate 0.327 and 0.164 kT chemical explosives with burial depths of 100 m for 90 stochastically generated fracture networks. Gases quickly reach the surface in 30% of the higher yield simulations and 5% of the lower yield simulations. The fast breakthrough can be attributed to the formation of connected pathways between fractures to the surface. The formation of a connected damage pathway to the surface is not clearly correlated with the fracture intensity (P32) in our simulations. Breakthrough curves with slower transport are highly variable depending on the fracture network sample. The variability in the breakthrough behavior indicates that ignoring the influence of fracture networks on rock damage, which strongly influences the hydraulic properties following an underground explosion, will likely lead to a large underestimation of the uncertainty in the gas transport to the surface. This work highlights the need for incorporation of fracture networks into models for accurately predicting gas seepage following underground explosions.

58 GEOSCIENCES↗
NASA NTRS1992

Damage to cellular DNA from particulate radiations, the efficacy of its processing and the radiosensitivity of mammalian cells. Emphasis on DNA double strand breaks and chromatin breaks

For several years, it has been evident that cellular radiation biology is in a necessary period of consolidation and transition (Lett 1987, 1990; Lett et al. 1986, 1987). Both changes are moving apace, and have been stimulated by studies with heavy charged particles. From the standpoint of radiation chemistry, there is now a consensus of opinion that the DNA hydration shell must be distinguished from bulk water in the cell nucleus and treated as an integral part of DNA (chromatin) (Lett 1987). Concomitantly, sentiment is strengthening for the abandonment of the classical notions of "direct" and "indirect" action (Fielden and O'Neill 1991; O'Neill 1991; O'Neill et al. 1991; Schulte-Frohlinde and Bothe 1991 and references therein). A layer of water molecules outside, or in the outer edge of, the DNA (chromatin) hydration shell influences cellular radiosensitivity in ways not fully understood. Charge and energy transfer processes facilitated by, or involving, DNA hydration must be considered in rigorous theories of radiation action on cells. The induction and processing of double stand breaks (DSBs) in DNA (chromatin) seem to be the predominant determinants of the radiotoxicity of normally radioresistant mammalian cells, the survival curves of which reflect the patterns of damage induced and the damage present after processing ceases, and can be modelled in formal terms by the use of reaction (enzyme) kinetics. Incongruities such as sublethal damage are neither scientifically sound nor relevant to cellular radiation biology (Calkins 1991; Lett 1990; Lett et al. 1987a). Increases in linear energy transfer (LET infinity) up to 100-200 keV micron-1 cause increases in the extents of neighboring chemical and physical damage in DNA denoted by the general term DSB. Those changes are accompanied by decreasing abilities of cells normally radioresistant to sparsely ionizing radiations to process DSBs in DNA and chromatin and to recover from radiation exposure, so they make significant contributions to the relative biological effectiveness (RBE) of a given radiation.(ABSTRACT TRUNCATED AT 400 WORDS).

Non-NASA Center↗
NASA NTRS2006

Effects of Displacement Damage on the Time-Resolved Gain and Bandwidth of a Low Breakdown Voltage Si Avalanche Photodiode

Effects of displacement damage and ionization damage induced by gamma irradiation on the dark current and impulse response of a high-bandwidth low breakdown voltage Si Avalanche Photodiode has been investigated using picosecond laser microscopy. At doses as high as 10Mrad (Si) minimal alteration in the impulse response and bandwidth were observed. However, dark current measurements also performed with and without biased irradiation exhibit anomalously large damage factors for applied biases close to breakdown. The absence of any degradation in the impulse response is discussed as are possible mechanisms for higher dark current damage factors observed for biased irradiation.

bandwidth↗
NASA NTRS2016

Using Satellite Remote Sensing to Assist the National Weather Service (NWS) in Storm Damage Surveys

In the United States, the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) is charged with performing damage assessments when storm or tornado damage is suspected after a severe weather event. This has led to the development of the Damage Assessment Toolkit (DAT), an application for smartphones, tablets and web browsers that allows for the collection, geolocation, and aggregation of various damage indicators collected during storm surveys.

Damage surveys↗
NASA NTRS2017

Simulation-Based Height of Burst Map for Asteroid Airburst Damage Prediction

Entry and breakup models predict that airburst in the Earth's atmosphere is likely for asteroids up to approximately 200 meters in diameter. Objects of this size can deposit over 250 megatons of energy into the atmosphere. Fast-running ground damage prediction codes for such events rely heavily upon methods developed from nuclear weapons research to estimate the damage potential for an airburst at altitude. (Collins, 2005; Mathias, 2017; Hills and Goda, 1993). In particular, these tools rely upon the powerful yield scaling laws developed for point-source blasts that are used in conjunction with a Height of Burst (HOB) map to predict ground damage for an airburst of a specific energy at a given altitude. While this approach works extremely well for yields as large as tens of megatons, it becomes less accurate as yields increase to the hundreds of megatons potentially released by larger airburst events. This study revisits the assumptions underlying this approach and shows how atmospheric buoyancy becomes important as yield increases beyond a few megatons. We then use large-scale three-dimensional simulations to construct numerically generated height of burst maps that are appropriate at the higher energy levels associated with the entry of asteroids with diameters of hundreds of meters. These numerically generated HOB maps can then be incorporated into engineering methods for damage prediction, significantly improving their accuracy for asteroids with diameters greater than 80-100 m.

Burst Map↗
NASA NTRS2018

Simulation of Stochastic Mud-Crack Damage Formation in an Environmental Barrier Coating

The integrated Finite Element Analysis–Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to simulate the formation of mudflat-cracks from thermomechanical loading on a multi-layered Environmental Barrier Coating (EBC) system deposited on a ceramic substrate. FEAMAC/CARES combines MAC/GMC multiscale composite micromechanics code with CARES/Life probabilistic multiaxial failure criteria code and Abaqusfinite element analysis. In this work, step function elastic modulus reduction of randomly damaged finite elements was used to represent discrete cracking events. The use of many small-sized low-aspect-ratio finite elements enabled the depiction of crack boundaries and formation of mudflat patterned damage. Demonstrated examples include finite element models of button–sized disk–shaped 3-D specimen, and a 2-D model of through-the-thickness cross-section. All models were subjected to a progressive cool down from 1300oC to room temperature. Mudflat crack damage in the coating system resulted from the buildup of residual tensile stresses between the individual material constituents from thermal expansion mismatch. A 2-parameter Weibull distribution characterized the coating layer stochastic strength response and the effect of the Weibull modulus on the formation of damage was studied here.

residual tensile stress↗
NASA NTRS2018

Weibull-Based Stochastic Simulation of Mud-Crack Damage Formation in an Environmental Barrier Coating

The integrated Finite Element Analysis Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to simulate the formation of mudflat-cracks from thermomechanical loading on a multi-layered Environmental Barrier Coating (EBC) system deposited on a ceramic substrate. FEAMAC/CARES combines MAC/GMC (Micromechanics Analysis Code/Generalized Method of Cells) multiscale composite micromechanics code with CARES/Life probabilistic multiaxial failure criteria code and Abaqusfinite element analysis. In this work, step function elastic modulus reduction of randomly damaged finite elements was used to represent discrete cracking events. The use of many small-sized low-aspect-ratio finite elements enabled the depiction of crack boundaries and formation of mudflat patterned damage. Demonstrated examples include finite element models of button-sized disk-shaped 3-D specimen, and a 2-D model of through-the-thickness cross-section. All models were subjected to a progressive cool down from 1300 degrees Centigrade to room temperature. Mudflat crack damage in the coating system resulted from the buildup of residual tensile stresses between the individual material constituents from thermal expansion mismatch. A 2-parameter Weibull distribution characterized the coating layer stochastic strength response and the effect of the Weibull modulus on the formation of damage was studied here.

Residual Tensile Stress↗
NASA NTRSDate not supplied

Progressive Damage Mechanisms in Thick 3D Composite Structures under Static and Fatigue Loading

The objective of this work is to demonstrate validation of predictive capabilities capturing both damage initiation and growth under static and fatigue loading in geometrically complex three-dimensional (3D) composite structures. The composite structure of interest in the present study resembles a 3D blade spar used in rotorcraft applications. Under both static and fatigue testing, it was shown that damage initiated at the same ply-drop location(s) and grew in the axial as well as hoop directions. CompDam – a state-of-the-art Progressive Damage Analysis (PDA) tool was used to achieve successful correlations of metrics including load-displacement responses and damage modes.

progressive damage analysis↗
NASA NTRS2021

Flood Monitoring and Crop Damage Assessment

In recent years, the occurrence and impact of inland and coastal flood events have become more frequent and damaging, especially within agricultural fields, due to the global climate change and consistent sea level rise. Monitoring and measuring the magnitude of flood events in a timely manner and assessing the subsequent crop damages accurately are precursors in minimizing detrimental consequences that could potentially lead to a global food security crisis. Traditional gauge-based measurements with sophisticated hydrological models are capable of monitoring flood events precisely but limited within the smaller spatial extent, time-consuming, and costly. In recent decades, advancement in airborne- and satellite-based remote sensing technologies offering products at a daily global spatial extent with various spectral resolution helps address the shortcomings of the traditional in situ approaches in flood monitoring. Furthermore, the methods such as classification and band ratioing using remote sensing products are simple and effective in assessing flood-induced agricultural damages. The combination of remote sensing products and geographic information systems along with the current development in web mapping, users now can get near real-time flood monitoring and crop damage assessments, albeit dependent upon the quality of available data. A case study to quantify the impact of the 2011 Missouri Mississippi River flooding on the surrounding cornfield was performed through a regression model. The model was trained using historical daily NDVI and corn yield across Nebraska and Missouri, and the overall accuracy in estimating corn yield was about 90%. The method implemented in this localized case study could be extended at a larger geographical scale.

Flood monitoring↗
DOE OSTI2021

Modeling Lithium Diffusion in Battery Cathodes Considering Chemo-Mechanically Induced Damage

This talk will present a 3D, continuum-level damage model for simulating Lithium diffusion within generated Li_{x}Ni_{0.5}Mn_{0.3}Co_{0.2} (NMC 532) secondary cathode particles. The primary motivation of the particle-level model is to inform cathode-particle design and determine charging profiles that reduce cathode fracture. The model considers NMC 532 secondary particles containing an agglomeration of anisotropic, randomly oriented grains. The model predicts that secondary-particle fracture is primarily due to non-ideal grain interactions with slight dependence on high-rate charge demands. The model predicts that small secondary-particles with large grains develop significantly less damage than larger secondary particles with small grains. Finally, the model predicts most of the chemo-mechanical damage accumulates in the first high-rate cycles. This chemo-mechanical “damage saturation” effect indicates that initial secondary-particle fracture occurs within the first few cycles, while long-term cathode degradation is not solely chemo-mechanically induced.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Going for complete defueling - A comprehensive solution for damaged spent fuel

The complete defueling of a NPP is a prerequisite for decommissioning and dismantling. In particular the defueling of damaged spent fuel and the following dry storage remains a challenge. It is the aim of the Quiver project to develop a one-fits-it-all solution for all different kinds of damaged spent fuel and to develop in addition comprehensive handling equipment to ensure a thoroughly dispatch of the damaged spent fuel inside the Quiver. As a comprehensive solution, GNS developed a Quiver System which complies with the requirements of the transport and storage cask CASTOR V. This paper details, first, the loading of damaged fuel rods into the Quivers including the necessary equipment, secondly, the dispatch of the Quivers including an illustration of the required equipment and facilities, and thirdly, the loading and dispatch of Quivers in the CASTOR V casks.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Potential mechanisms for cancer resistance in elephants and comparative cellular response to DNA damage in humans

Here, evolutionary medicine may provide insights into human physiology and pathophysiology, including tumor biology. To identify mechanisms for cancer resistance in elephants and compare cellular response to DNA damage among elephants, healthy human controls, and cancer-prone patients with Li-Fraumeni syndrome (LFS). Design, Setting, and Participants A comprehensive survey of necropsy data was performed across 36 mammalian species to validate cancer resistance in large and long-lived organisms, including elephants (n=644). The African and Asian elephant genomes were analyzed for potential mechanisms of cancer resistance. Peripheral blood lymphocytes from elephants, healthy human controls, and patients with LFS were tested in vitro in the laboratory for DNA damage response. The study included African and Asian elephants (n=8), patients with LFS (n=10), and age-matched human controls (n=11). Human samples were collected at the University of Utah between June 2014 and July 2015. Exposures Ionizing radiation and doxorubicin. Cancer mortality across species was calculated and compared by body size and life span. The elephant genome was investigated for alterations in cancer-related genes. DNA repair and apoptosis were compared in elephant vs human peripheral blood lymphocytes. Across mammals, cancer mortality did not increase with body size and/or maximum life span (eg, for rock hyrax, 1% [95% CI, 0%-5%]; African wild dog, 8% [95% CI, 0%-16%]; lion, 2% [95% CI, 0%-7%]). Despite their large body size and long life span, elephants remain cancer resistant, with an estimated cancer mortality of 4.81% (95% CI, 3.14%-6.49%), compared with humans, who have 11% to 25% cancer mortality. While humans have 1 copy (2 alleles) of TP53, African elephants have at least 20 copies (40 alleles), including 19 retrogenes (38 alleles) with evidence of transcriptional activity measured by reverse transcription polymerase chain reaction. In response to DNA damage, elephant lymphocytes underwent p53-mediated apoptosis at higher rates than human lymphocytes proportional to TP53 status (ionizing radiation exposure: patients with LFS, 2.71% [95% CI, 1.93%-3.48%] vs human controls, 7.17% [95% CI, 5.91%-8.44%] vs elephants, 14.64% [95% CI, 10.91%-18.37%]; P<.001; doxorubicin exposure: human controls, 8.10% [95% CI, 6.55%-9.66%] vs elephants, 24.77% [95% CI, 23.0%-26.53%]; P<.001). Compared with other mammalian species, elephants appeared to have a lower-than-expected rate of cancer, potentially related to multiple copies of TP53. Compared with human cells, elephant cells demonstrated increased apoptotic response following DNA damage. These findings, if replicated, could represent an evolutionary-based approach for understanding mechanisms related to cancer suppression.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Regional distribution of large blowdown patches across Amazonia in 2005 caused by a single convective squall line: Distribution of Amazonia Blowdown Damage

In mid-January 2005 a convective squall line traversed 4.5 × 10 6 km 2 of Amazonia from southwest to northeast. As seen in Landsat images, this atypical convective storm left blowdown imprints with diffuse geometry, unlike the fan-shaped wind disturbance of much more frequent east-to-west propagating squall lines. Previous work reported 0.2% of the forest area damaged by this one relatively rare event within one Landsat image and assumed similar disturbance across the entire traverse. Here, we mapped convective wind damage impact to the region in 2005 by identifying large-scale (>4 ha) blowdown imprints in 30 Landsat images. The diffuse-type imprints associated with this single squall line contributed up to 60–72% of total 2005 wind-disturbed area detected across the region, but damage was highly concentrated in central Amazonia. Consequently, the distribution of large wind damage patches in 2005 across Amazonia was very different from long-term average. In conclusion, tegional distribution of wind-driven tree mortality for smaller patch sizes remains unknown.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

An Engineered Multifunctional Composite for Passive Sensing, Power Harvesting, and In Situ Damage Identification with Enhanced Mechanical Performance

A multifunctional fiber-reinforced composite with passive self-sensing, energy-harvesting, and damage detection capabilities is presented. In this work, barium titanate piezoelectric microparticles are deposited on basalt fibers by a scalable, low-cost, environmentally friendly continuous feed-through process. The resulting composite derives a superior interlaminar shear strength from the microparticle-modified fiber–matrix interfaces. The composite also demonstrates passive self-sensing capabilities that produce electrical signals proportional to various dynamic loading events. Vibration and strain-controlled experiments are performed on composite beams to quantify the sensitivity and power output as a function of input acceleration and strain. Furthermore, these composite-generated electrical signals are used to identify in situ damage initiation for structural health monitoring to inform composite damage prior to structural failure. In brief, this truly multifunctional composite simultaneously displays a sensitivity of 0.5–2.6 mV g -1 at a resolution of 0.045–0.20g (g = gravitational acceleration), energy harvesting in the range of nW cc -1 , and prediction of early damage by exhibiting 0.017–1.17 mV peaks in voltage–time history profiles while assuring ≈20% improved interlaminar shear strength.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A Hybrid Deep Learning Architecture for Classification of Microscopic Damage on NIF Laser Optics

Accurately classifying microscopic damage helps automate the repair and recycling of National Ignition Facility optics and informs the study of damage initiation and growth. This complex 12-class problem previously required human experts to distinguish and label the various damage morphologies. Finding image analysis methods to extract and calculate distinguishing features would be time consuming and challenging, so we sought to automate this task by using convolutional neural networks (CNNs) pretrained on the ImageNet database to take advantage of its automated feature discovery and extraction. We compared three model architectures on this dataset and found the one with highest overall accuracy, 99.17%, was a novel hybrid architecture, one in which we removed the final decision-making layer of the deep learner and replaced it with an ensemble of decision trees (EDT). This combines the power of feature extraction by CNNs with the decision-making strength of EDT. The accuracy of the hybrid architecture over the deep learning alone is shown to be significantly improved. Furthermore, we applied this novel hybrid architecture to an entirely different dataset, one containing images of repaired damage sites, and improved on the previously published findings, also with a demonstrably significant increase in accuracy over using the deep learner alone.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

Future property damage from flooding: sensitivities to economy and climate change

Using a unique dataset for Indiana counties during the period 1995-2012, we estimate the effects of flood hazard, asset exposure, and social vulnerability on property damage. This relationship then is combined with the expected level of future flood risks to project property damage from flooding in 2030 under various scenarios. We compare these scenario projections to identify which risk management strategy offers the greatest potential to mitigate flooding loss. Results show that by 2030, county level flooding hazard measured by extreme flow volume and frequency will increase by an average of 16.2% and 7.4%, respectively. The total increase in property damages projected under different model specifications range from 13.3% to 20.8%. Across models future damages consistently exhibit the highest sensitivity to future increases in asset exposure, reinforcing the importance of non-structural measures in managing floodplain development.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Ion mass dependence of irradiation-induced damage accumulation in KTaO 3

Damage production and amorphization resulting from the interaction of medium-energy (from 40 to 480 keV) noble-gas ions (from He to Kr) with potassium tantalate (KTaO 3 ) are determined using ion channeling measurements. A disorder accumulation model has been fit to the maximum damage concentration versus ion fluence to extract the cross sections for direct-impact and defect-stimulated amorphization, and the results indicate that defect-stimulated amorphization is the dominant mechanism. These cross sections exhibit a strong dependence on the calculated cross sections for displacing lattice atoms, indicating a dominant contribution of nuclear interactions to the defect production and amorphization processes under the irradiation conditions used in this study. Furthermore, these experimental findings, along with the model fits, suggest that the difference in recoil spectra between He and the other heavier ions may be the main driving force for the decreased damage efficiency observed for He ions, which results in a reduced rate of damage accumulation.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Impact of Hot Bending on the High-Temperature Performance and Hydrogen Damage of 2.25Cr-1Mo-0.25V Steel

The impact of hot bending forming process on the high-temperature mechanical properties and hydrogen damage of 2.25Cr-1Mo-0.25V steel was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectrum (EDS) and the slow strain rate tensile (SSRT) test in high-temperature hydrogen environment. The samples containing hot bending residual influence were extracted from a real hydrogenation reactor shell fabricated through hot bending–welding process. SEM images of the material demonstrated that the density and size of carbides in 2.25Cr-1Mo-0.25V increased after forming. TEM and EDS results revealed that ferrite matrix of the formed material was purified. The mechanical properties measured by SSRT test manifested that 2.25Cr-1Mo-0.25V was softened after forming. Moreover, it was observed that high-temperature hydrogen environment embrittled the material and the susceptibility to hydrogen damage increased after forming. The role of hot bending process on the evolution of mechanical properties and hydrogen damage susceptibility was discussed. Possible mechanism for the impact of hot bending process on the high-temperature hydrogen damage was proposed.

36 MATERIALS SCIENCE↗