Explosive-induced shock damage in copper and recompression of the damaged region
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36 MATERIALS SCIENCE↗
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Results for “DAMAGE”
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The impact of contamination and aging effects on the long-term laser-damage resistance of SiO 2 /HfO 2 /TiO 2 high-reflection coatings for 1054nm
The laser damage thresholds of optical coatings can degrade over time due to a variety of factors, including contamination and aging. Optical coatings deposited using electron beam evaporation are particularly susceptible to degradation due to their porous structure. In a previous study, the laser damage thresholds of optical coatings were reduced by roughly a factor of two from 2013 to 2017. The coatings in question were high reflectors for 1054 nm that contained SiO 2 and HfO 2 and/or TiO 2 layers, and they were stored in sealed PETG containers in a class 100 cleanroom with temperature control. At the time, it was not certain whether contamination or thin film aging effects were responsible for the reduced laser damage thresholds. Therefore, to better understand the role of contamination, the coatings were recleaned and the laser damage thresholds were measured again in 2018. Here, the results indicate that contamination played the most dominant role in reducing the laser damage thresholds of these optical coatings, even though they were stored in an environment that was presumed to be clean.
42 ENGINEERING↗
Numerical study of damage in particulate composites during high-strain rate loading using novel damage model
Not provided.
Materials Science↗
Cationic Dependence of X-ray Induced Damage in Strontium and Barium Nitrate
The response of solids to x-ray irradiation is not well understood, in part, because the interactions between x-rays and molecules in solids depend on the intra- and/or inter-molecular electronic properties of the material. Our previous work demonstrated that x-ray induced damage of certain ionic salts depends on the irradiating photon energy, especially when irradiated with photons of energy near the cation’s K-edge. To advance understanding of the cationic dependence of x-ray photochemistry, we present studies of x-ray induced damage of barium nitrate and strontium nitrate. Polycrystalline samples of barium and strontium nitrate were irradiated with high flux monochromatic synchrotron x-rays at selected energies near the K-edge of the respective cations. The damage processes were studied with powder x-ray diffraction, and irradiation products, NO 2 and O 2 , were characterized via Raman spectroscopy. Our results demonstrate that irradiating barium and strontium nitrate with photons of energy greater than the K-edge of the cation promotes high rate of decomposition compared to that observed when irradiating with photons of energy below the K-edge. Additionally, differences in x-ray induced damage between the two compounds are examined and discussed, and evidence of the diffusion of irradiation products is presented.
36 MATERIALS SCIENCE↗
High-pressure-assisted X-ray-induced damage as a new route for chemical and structural synthesis
A novel structural and chemical synthesis of Cs–O derived materials has been demonstrated via X-ray irradiation of Cs 2 C 2 H 2 O 5 at high pressure.
Evlyukhin, Egor↗
Metabolite Damage and Metabolite Damage Control in Plants
It is increasingly clear that (a) many metabolites undergo spontaneous or enzyme-catalyzed side reactions in vivo, (b) the damaged metabolites formed by these reactions can be harmful, and (c) organisms have biochemical systems that limit the buildup of damaged metabolites. These damage-control systems either return a damaged molecule to its pristine state (metabolite repair) or convert harmful molecules to harmless ones (damage preemption). Because all organisms share a core set of metabolites that suffer the same chemical and enzymatic damage reactions, certain damage-control systems are widely conserved across the kingdoms of life. Relatively few damage reactions and damage-control systems are well known. Uncovering new damage reactions and identifying the corresponding damaged metabolites, damage-control genes, and enzymes demands a coordinated mix of chemistry, metabolomics, cheminformatics, biochemistry, and comparative genomics. This review illustrates the above points using examples from plants, which are at least as prone to metabolite damage as other organisms.
cheminformatics↗
Heterogeneous energetic material damage simulator (HEDS): A deep learning approach to simulate damage–sensitivity linkages
Damage in the microstructures of energetic materials (EMs), such as propellants and plastic bonded explosives (PBXs), can significantly alter their response to external loads. Both sensitization and desensitization can occur, causing concerns with safety and performance in the field; predictive models that connect damage and the sensitivity of EMs can enable design and provide confidence in their robustness and reliability. However, modeling of damage evolution is challenging for real microstructures of EMs; samples of damaged EMs are difficult to obtain, thereby hindering experiments and direct numerical simulations to determine the sensitivity of EMs at various stages of damage. Here, we develop an approach to generate synthetic, i.e., in silico produced, damaged microstructures for use in simulations to connect damage levels to sensitivity. The development of the present workflow to generate and impose varying levels of damage in microstructures, known as HEDS (Heterogeneous Energetic Material Damage Simulator), begins with a small set of images of damaged PBXs and combines a collection of deep neural network techniques to generate microstructures with varying levels of damage. By making the synthetic microstructures conform closely to those observed in available real, imaged microstructures, we develop an ensemble of damaged microstructures that can be used for in silico shock experiments. HEDS develops these microstructure ensembles as level set fields, which are directly employed in a sharp interface Eulerian hydrocode where shock simulations are performed to quantify the energy release rate from hotspot fields generated in the microstructure. These capabilities can be useful for the analysis and assessment of changes in the sensitivity of EMs and to design formulations that are less susceptible to damage-induced changes in sensitivity and performance.
Fang, Irene (ORCID:0009000844557122)↗
A thermodynamics-based damage model for the non-linear mechanical behavior of SiC/SiC ceramic matrix composites in irradiation and thermal environments
A damage model is developed and validated with experimental data for the non-linear mechanical behavior of SiC/SiC composite materials in nuclear applications. Cyclic thermal and mechanical loading associated with neutron irradiation effects of these composites leads to wide-spread and progressive micro-cracking that leads to loss of thermal conductivity and further enhancement of thermo-mechanical damage. A physics-based model of wide-spread micro-cracking is developed within the thermodynamic framework of continuum damage mechanics. Evolution equations for damage parameters that describe the growth of continuum damage are developed, where the material variables are obtained from experiments. The model novelty is in coupling mechanical, thermal, and irradiation damage through a consistent thermodynamic framework, including loss of thermal conductivity due to the evolution of mechanically induced micro-cracks. A number of thermo-mechanical experiments were conducted to confirm model assumptions. The model is shown to be validated with out-of-pile experiments, and then implemented using commercial finite element code COMSOL to the fuel cladding problem with normal and high radiation dose cases.
Materials Science↗
Damage development in neutron-irradiated concrete in a test reactor: Hygro-thermal and mechanical simulations
This paper reports the development of a 3D mesoscale hygro-thermal-mechanical simulation approach to predict damage in concrete irradiated in a test reactor. This framework, developed in MOOSE, considers the effects of elevated temperature, moisture content, and high neutron fluence (energy threshold, E > 0.1 MeV) on the mortar and aggregates separately. The first-stage simulation implements hygro-thermal analysis to determine the temperature and RH inside the specimen as a function of imposed radiation energy. These are used as inputs to the second stage, which considers radiation-induced volumetric expansion (RIVE) of aggregates, and creep, shrinkage, and stress-strain response of mortar to predict the expansion, stresses, and damage in specimens made using different coarse aggregates and subjected to different irradiation times. The irradiation time-dependent damage in the mortar is expressed using an isotropic damage parameter. This multi-physics model serves as a predictive tool for damage quantification in concrete due to neutron irradiation.
36 MATERIALS SCIENCE↗
A directional microcrack damage theory for brittle solids based on continuous hyperplasticity
We present a novel microcrack-damage theory for brittle solids under compression. Instead of using internal variables like zeroth, second or fourth rank damage tensors, the state of material damage is represented by an internal function that encapsulates the information of direction, density and size of microcracks. Just like other internal variables, the evolution of this state function must obey the second law of thermodynamics for arbitrary loading paths. This is done by casting the model in the framework of continuous hyperplasticity and enforcing a non-negative dissipation rate functional. The proposed framework offers predictions on the continuous evolution of microcrack density and the induced material anisotropy along with the macroscopic stress-strain curves. The use of continuous damage function grants the model significantly enhanced resolution in characterizing the direction-dependent response of cracked solids compared to classical models that are based on damage tensors. Two scenarios are considered in developing the theory, one assumes frictionless cracks and the other incorporates friction between crack surfaces. The results highlight that inelasticity, pressure dependence, and loading-unloading hysteresis exhibited by brittle solids are natural consequences of frictional microcracks. The proposed theory offers a generic and versatile framework to upscale micromechanical processes operating at individual crack scale to explain the macroscopic behavior of cracked solids.
Materials Science↗
Molecular Dynamics Simulation of Fission Fragment Damage in Nuclear Fuel and Surrogate Material
We have performed classical molecular dynamics simulations of swift heavy ion damage, typical of fission fragments, in nuclear fuel (UO2) for energy deposition per unit length of 3.9 keV/nm. We did not observe amorphization. The damage mainly consisted of isolated point defects. Only about 1% of the displacements occur on the uranium sublattice. Oxygen Frenkel pairs are an order of magnitude more numerous than uranium Frenkel pairs in the primary damage state. In contrast, previous results show that the ratio of Frenkel pairs on the two sublattices is close to the stoichiometric ratio in ceria. These differences in the primary damage state may lead to differences in radiation response of UO2 and CeO2.
Molecular dynamics, radiation damage in materials,↗
Isochronal annealing effects on local structure, crystalline fraction, and undamaged region size of radiation damage in Ga-stabilized δ-Pu
The effects on the local structure due to self-irradiation damage of Ga stabilized δ-Pu stored at cryogenic temperatures have been examined using extended x-ray absorption fine structure (EXAFS) experiments. Extensive damage, seen as a loss of local order, was evident after 72 days of storage below 15 K. The effect was observed from both the Pu and the Ga sites, although less pronounced around Ga. Isochronal annealing was performed on this sample to study the annealing processes that occur between cryogenic and room temperature storage conditions, where damage is mostly reversed. Damage fractions at various points along the annealing curve have been determined using an amplitude-ratio method, a standard EXAFS fitting, and a spherical crystallite model, and provide information complementary to the previous electrical resistivity- and susceptibility-based isochronal annealing studies. The use of a spherical crystallite model accounts for the changes in EXAFS spectra using just two parameters, namely, the crystalline fraction and the particle radius. Together, these results are discussed in terms of changes to the local structure around Ga and Pu throughout the annealing process and highlight the unusual role of Ga in the behavior of the lowest temperature anneals.
36 MATERIALS SCIENCE↗
Correlations among void shape distributions, dynamic damage mode, and loading kinetics [Correlations among spall void shape distributions, damage mode and shock loading kinetics]
Here, three-dimensional x-ray tomography (XRT) provides a nondestructive technique to characterize the size, shape, and location of damage in dynamically loaded metals. A shape-fitting method comprising the inertia tensors of individual damage sites was applied to study differences of spall damage development in face-centered-cubic (FCC) and hexagonal-closed-packed (HCP) multicrystals and for a suite of experiments on high-purity copper to examine the influence of loading kinetics on the spall damage process. Applying a volume-weighted average to the best-fit ellipsoidal aspect-ratios allows a quantitative assessment for determining the extent of damage coalescence present in a shocked metal. It was found that incipient transgranular HCP spall damage nucleates in a lenticular shape and is heavily oriented along particular crystallographic slip directions. In polycrystalline materials, shape distributions indicate that a decrease in the tensile loading rate leads to a transition to coalesced damage dominance and that the plastic processes driving void growth are time dependent.
36 MATERIALS SCIENCE↗
Photovoltaic Module Imaging for Hail Damage Assessment with Multi-Year Follow Up
Outdoor-aged photovoltaic modules that have experienced golf-ball sized hail are characterized by flash testing and photoluminescence, electroluminescence, thermal, and ultraviolet fluorescence imaging. These measurements were performed immediately after the hailstorm and then again after another two years and four years in the field. The modules originally experienced different ranges of hail damage with some having cracks on approximately half of the cells and some having few to no cracked cells. Flash testing shows that the hail-damaged modules with the most cracked cells have 3 to 4% less power than those with the least damage. After four more years in the outdoor climate of Golden, Colorado since the hailstorm, all of the modules still exhibit similar relative power and amounts of cell cracking, suggesting that the hail damage has only initially reduced power but has not yet increased the degradation rate.
electroluminescence↗
Role of interfaces in damage process of irradiated lithium aluminate nanocrystals
Molecular dynamics simulations were performed to understand the differences in the response of single crystal and nanocrystalline ?-LiAlO2 to energy deposition by 10 keV Li recoils. The simulations are performed at 573 K and focus on the damage production in the absence of thermal annealing. The grain boundaries in the nanocrystals are found to be amorphous. Analyses of the fate of the beam ions show that the amorphous grain boundaries and differently oriented nanograins increase the number of back-scattered ions and decrease the number of transmitted ions. Damaged regions protruding from the grain boundaries provide a direct evidence of the role of the grain boundaries as scattering centers in collision cascades. The simulations show that the defect density produced in the nanocrystals is about twice that in the single crystals. In both samples, Li defects account for 70% of the defects, demonstrating that LiO4 tetrahedra is much more susceptible to damage than AlO4 tetrahedra. Furthermore, Li defects occur preferentially near grain boundaries. Diffusion simulations confirm the limited thermal diffusion of defects at 573 K, effectively separating the damage production from thermal annealing in the irradiation simulations. Nevertheless, the mean square displacements of grain boundary defects are found to be larger than lattice defects and surface defects.
lithium aluminate, interfaces, irradiation, molecu↗
Sapphire advanced mitigation process: wet etch to expose sub-surface damage and increase laser damage resistance and mechanical strength
In this study, a novel, to the best of our knowledge, method of wet chemical etching of sapphire workpieces (such as optics, wafers, windows, and cones), called the sapphire advanced mitigation process (or sapphire AMP), has been developed that exposes sub-surface mechanical damage created during the optical fabrication process and significantly enhances the surface laser damage resistance (> 2×) and mechanical strength (up to ~ 2.6×). Sapphire AMP involves first treating the workpiece with a mixture of sulfuric and phosphoric acid ([H 2 SO 4 ]:[H 3 PO 4 ]= 1 : 3) at 220°C, followed with phosphoric acid at 160°C, then with sodium hydroxide base (NaOH) and surfactant at 40°C, and finally with a high-pressure deionized water spray rinse. Sapphire AMP has been demonstrated on both A- and C-plane sapphire workpieces. The mechanism of this etch process involves the reaction of the sapphire (Al 2 O 3 ) surface with sulfuric acid (H 2 SO 4 ) forming aluminum sulfate [Al2(SO4)3], which has low solubility. The high phosphoric acid content in the first and second steps of sapphire AMP results in the efficient conversion of Al 2 (SO 4 ) 3 to aluminum phosphate (AlPO 4 ), which is very soluble, greatly reducing reaction product redeposition on the workpiece surface. Sapphire AMP is shown to expose sub-surface mechanical damage on the sapphire surface created during the grinding and polishing processes, whose etched morphology has either isotropic or anisotropic evolution depending on the nature of the initial surface damage. Sapphire AMP was also designed to remove the key known surface, laser absorbing precursors (namely, foreign chemical impurities, the fracture surface layer of preexisting sub-surface damage, and reaction product or foreign species redeposition or precipitation). Static and sliding indention induced surface microfractures on sapphire are shown after sapphire AMP to have a significant decrease in the fast photoluminescence intensity (a known metric for measuring the degree of laser damaging absorbing precursors). In addition, the onset of laser damage (at 351 nm 3 ns) on sapphire AMP treated workpieces was shown to increase in fluence from ~ 4 to >9.5J/cm 2 . Finally, biaxial ball-on-ring mechanical tests on sapphire disks showed an increase in the failure stress from 340 MPa (with pre-existing 28 µm flaws) to ~ 900MPa after sapphire AMP, which is attributed to the blunting of the surface microfractures.
36 MATERIALS SCIENCE↗
Retention properties in displacement damaged ultra-fine grain tungsten exposed to divertor plasma
One of the main advantages of using tungsten (W) as a plasma facing material (PFM) is its low uptake and retention of tritium. However, in high purity (ITER grade) W, hydrogenic retention increases significantly with neutron-induced displacement damage in the W lattice. This experiment examines an alternative W grade PFM, ultra-fine grain (UFG) W, to compare its retention properties with ITER grade W after 12 MeV Si ion displacement damage up to 0.6 dpa (displacements per atom.) Following exposure to plasma in the DIII-D divertor, D retention was then assessed with Nuclear Reaction Analysis (NRA) depth profiling up to 3.5 µm and thermal desorption spectrometry (TDS). Undamaged specimens were also included in our test matrix for comparison. For all samples, D release peaks were observed during TDS at approximately 200 °C and 750 °C. For the ITER-grade W specimens, the intensity of the 750 °C release peak was more pronounced for specimens that had been pre-damaged. Conversely, UFG samples that had been damaged by 12 MeV Si showed enhancement of the lower temperature release peak (200 °C). NRA profiles also reveal a higher D concentration for UFG W samples up to the peak in the damage profile at a depth of 2 m. Overall, we observed that the total trapped inventory in UFG W was 20% higher than ITER grade W in the undamaged case and 10% higher in the damaged case. A comparison of NRA and TDS data indicates that a larger fraction of the total retained D is trapped near the surface (86–100%) in UFG W pre-damaged to 0.6 dpa compared with ITER grade W (39–61%). Further examination of the UFG material with microscopy is recommended for a definitive determination of the types of defects responsible for D trapping. Our results highlight some potential trade-offs associated UFG W regarding its performance from a tritium retention standpoint. That said, our TDS results indicate that this enhanced inventory can be released by baking at relatively low temperatures (<500 °C), providing an avenue for minimizing tritium retention in this material that would be practical for implementation in a tokamak.
Barton, J↗