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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Hydroxyl radical‐driven transformations of bisphenol A and 2,4‐dinitroanisole: Experimental and computational analysis

Abstract This study used experimental and computational analysis to investigate the advanced oxidation of bisphenol A (BPA) and 2,4‐dinitroanisole (DNAN). The pseudo first‐order reaction rate constants depended on the molar peroxide ratio and were between 0.13 and 0.28 min −1 for BPA and between 0.018 and 0.032 min −1 for DNAN. The kinetic differences appear to be due in part to the energy requirements for oxidation, which depended on the reaction mechanism but were typically lower for BPA than they were for DNAN. Density functional theory (DFT) was used to develop transformation pathways that included experimentally‐detected byproducts. The most energetically favored pathway for BPA oxidation begins with the formation of hydroxylated derivatives, while for DNAN, the most energetically favorable degradation pathway begins with the substitution of the methoxy group. Overall, these findings demonstrate the power of combining experimental and computational tools to reveal transformation mechanisms during water treatment. Practitioner Points Advanced oxidation transformations for two emerging water pollutants, bisphenol A and dinitroanisole, was investigated. The observed reaction kinetics depended on molar peroxide ratio in a manner that is in keeping with previous findings. Density functional theory‐based analysis revealed reaction energy requirements and degradation pathways.

Engineering↗
DOE OSTI2020

Calibration of hyperelastic constitutive models: the role of boundary conditions, search algorithms, and experimental variability

The calibration of hyperelastic constitutive models of soft tissue and tissue surrogates is often treated as an exercise in curve-fitting to the average experimental response, and many of the complicating factors such as experimental boundary conditions and data variability are ignored. Here, we focus on three questions that arise in this area: the ramifications of ignoring the experimental boundary conditions, the use of local optimizers, and the role of data variability. Using data from a uniaxial extension experiment on a tissue surrogate, we study how these three factors affect the calibration of isotropic hyperelastic constitutive models. Our results show that even with the simplest of constitutive models, it is necessary to look beyond a "good fit" to the average.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Experimental and Computational Investigation of the Emission of Radioactive Products from Irradiated Fuel of Fast Sodium-Cooled Reactor

The key experimental and computational studies of the emission of long-lived radioactive fission products and actinides from uranium dioxide irradiated in BN-600 into sodium and the gas phase in the range 150–800°C, performed on the experimental bench at the Leipunskii Institute of Physics and Power Engineering, are presented. The results of measurements of the properties of aerosols of certain radioactive fission products formed upon heating of irradiated nuclear fuel in sodium are presented. The experimental results are of interest for evaluating the radiation impact of reactor facilities on workers and the public during beyond design basis accidents.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Computational and Experimental Studies of Mixing of a Light Gas in the ERCOSAM–SAMARA Projects

Severe accidents in NPP with VVER can be accompanied by hydrogen entering the containment space. The aim of the present work is an experimental and computational study of the possibility of hydrogen stratification in the containment in a scenario replicating the sequence of events occurring during a severe accident with hydrogen emission in a light-water reactor taking account of the impact of accident control on the distribution of a light gas. Euratom and the government corporation Rosatom performed the studies as part of two parallel projects – ERCOSAM and SAMARA. The experimental studies show that heat exchangers aand recombiners do bring about complete mixing of the light gas; a sprinkler system affords mixing of the stratified layer. The experimental studies confirm the results of numerical modeling.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Experimental Determination of Combustion Characteristics for Commercial Biodiesel and 0# Diesel

In this project, we have experimentally studied the combustion characteristics of commercial refined biodiesel and 0# diesel. Combustion of these two types of flammable liquids was carried out in a calorimeter to measure their heat release rate. The results showed that the heat release rate, which is one of the most significant properties in studying combustion, varies significantly depending on the samples and the dimensions of the circular burner. With the aim of evaluating the combustion characteristics, we also determined and analyzed other key properties of the fuels such as flash point, total heat release, and mass loss rate, which reflect the fire hazard. The results provide an experimental basis for developing fire protection measures during use, storage, and distribution of biodiesel. The flash point of biodiesel is higher than for 0# diesel, while the heat release rate, the experimental total heat release, the average combustion temperature and the radiation of biodiesel are lower than for 0# diesel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Review of the synergies between computational modeling and experimental characterization of materials across length scales

With the increasing interplay between experimental and computational approaches at multiple length scales, new research directions are emerging in materials science and computational mechanics. Such cooperative interactions find many applications in the development, characterization and design of complex material systems. This manuscript provides a broad and comprehensive overview of recent trends in which predictive modeling capabilities are developed in conjunction with experiments and advanced characterization to gain a greater insight into structure–property relationships and study various physical phenomena and mechanisms. The focus of this review is on the intersections of multiscale materials experiments and modeling relevant to the materials mechanics community. After a general discussion on the perspective from various communities, the article focuses on the latest experimental and theoretical opportunities. Emphasis is given to the role of experiments in multiscale models, including insights into how computations can be used as discovery tools for materials engineering, rather than to “simply” support experimental work. This is illustrated by examples from several application areas on structural materials. In conclusion this manuscript ends with a discussion on some problems and open scientific questions that are being explored in order to advance this relatively new field of research.

3-D microstructure characterization↗
DOE OSTI2019

Experimental Validation of the Horikx Theory to be Used in the Rubber Devulcanization Analysis

The waste rubber and end-of-life tires management has become a serious environmental problem. It is well known that the best way to carry out the disposal of these wastes is through recycling by devulcanization. Therefore, in the last decades, many methods have been developed to perform this treatment. Nevertheless, the degree and quality of the achieved devulcanization is still difficult to evaluate. The Horikx theory is an approach often used for this purpose. Hence, in this work, the validity of this theory was experimentally checked. The theoretical curve that represents crosslink scission was experimentally built for sulfur-cured natural rubber, sulfur-cured natural rubber reinforced with carbon black, sulfur-cured ethylene propylene diene monomer rubber and peroxide-cured ethylene propylene diene monomer rubber. Several samples with vulcanization (or devulcanization) degree ranging from 0 to 100% were processed, and the corresponding soluble fractions and crosslink densities were measured by the swelling test. The experimental results were in good agreement with the theoretical predictions, independently of the studied material, fact that confirms the validity of the Horikx approach. This finding will contribute to improve the waste rubber devulcanization, and therefore to progress in the environmental protection.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Theoretical and experimental analysis of bidirectionally pumped 1.3 μm Pr{sup 3+}-doped ASE source

We have analyzed the characteristics of 1.3 μm praseodymium (Pr{sup 3+}) doped bidirectionally pumped double pass (BIP-DP) configuration amplified spontaneous emission (ASE) source theoretically and experimentally. The source’s simulation model was established and corresponding simulated results were given. The effects of pump ratio, Pr{sup 3+}-doped fiber (PDF) length, total pump power and source’s optical losses were researched. The output power of BIP-DP ASE source is mainly affected by the total pump power, PDF length and source’s optical losses, while it has little relationship with the pump ratio. The BIP-DP ASE source operating at the symmetric bi-directional pump condition was constructed experimentally. The acquired output power of more than 5 mW has been obtained experimentally, which was with the quasi-gaussian output spectrum, and its 3 dB bandwidth is ~ 20 nm.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Codimerization of norbornene and 1,3-cyclopentadiene: quantum chemical and experimental research

A comprehensive theoretical and experimental research of the diene synthesis involving norbornene (1) and 1,3-cyclopentadiene (2) was carried out. The thermodynamic and kinetic parameters were evaluated by quantum chemical methods, and the structures of stereoisomeric products and the quantitative estimation of their ratio were predicted. The results of quantum chemical analysis were experimentally confirmed. The structures of codimers of 1 with 2 and their ratio were determined by a number of physicochemical methods. A strategy combining the theoretical and experimental studies and enabling to optimize the search for objects for the synthesis and reaction conditions was proposed.

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

Experimental Research on Tensile Behavior of Advanced High-Strength Steel DP600 at High Strain Rate

We conducted a series of experimental investigations on the mechanical properties of DP600 dual-phase steel under strain rates from 0.001 to 3000 s{sup −1} at room temperature. A split Hopkinson tensile bar was used to capture a high strain rate response. A comparison of the quasi-static and dynamic experiment results showed that the yield strength and ultimate tensile strength increased significantly under dynamic conditions. Fractographs were analyzed by scanning electron microscopy, which indicated a better ductility at a high strain rate. Based on the experimental results, the Johnson–Cook constitutive model was applied to describe the tensile deformation behavior under various strain rates. A reasonable agreement was observed between the experimental data and the Johnson–Cook model. A metallographic analysis of tensile specimens showed that the average ferritic grain size of the fractured specimens at a high strain rate was smaller than that of the fractured specimens under quasi-static conditions. Ferritic grain refinement proved that high-speed forming could enhance the forming ability of the DP600 steel.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The Effect of the Prior and the Experimental Design on the Inference of the Precision Matrix in Gaussian Chain Graph Models

Here, we investigate whether (and how) experimental design could aid in the estimation of the precision matrix in a Gaussian chain graph model, especially the interplay between the design, the effect of the experiment and prior knowledge about the effect. Estimation of the precision matrix is a fundamental task to infer biological graphical structures like microbial networks. We compare the marginal posterior precision of the precision matrix under four priors: flat, conjugate Normal-Wishart, Normal-MGIG and a general independent. Under the flat and conjugate priors, the Laplace-approximated posterior precision is not a function of the design matrix rendering useless any efforts to find an optimal experimental design to infer the precision matrix. In contrast, the Normal-MGIG and general independent priors do allow for the search of optimal experimental designs, yet there is a sharp upper bound on the information that can be extracted from a given experiment. We confirm our theoretical findings via a simulation study comparing (i) the KL divergence between prior and posterior and (ii) the Stein’s loss difference of MAPs between random and no experiment. Our findings provide practical advice for domain scientists conducting experiments to better infer the precision matrix as a representation of a biological network.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Meshfree simulation and experimental validation of extreme thermomechanical conditions in friction stir extrusion

Abstract Friction stir extrusion (FSE) is a novel solid-phase processing technique that consolidates and extrudes metal powders, flakes, chips, or billets into high-performance parts by plastic deformation, which has the potential to save substantial processing time and energy. Currently, most studies on FSE are experimental and only a few numerical models have been developed to explain and predict the complex physics of the process. In this work, a meshfree simulation framework based on smoothed particle hydrodynamics (SPH) was developed for FSE. Unlike traditional grid-based methods, SPH is a Lagrangian particle-based method that can handle severe material deformations, capture moving interfaces and surfaces, and monitor the field variable histories explicitly without complicated tracking schemes. These aspects of SPH make it attractive for the FSE process, where in situ evolution of field variables is difficult to observe experimentally. To this end, a 3-D, fully thermomechanically coupled SPH model was developed to simulate the FSE of aluminum wires. The developed model was thoroughly validated by comparing the numerically predicted material flow, strain, temperature history, and extrusion force with experimental results for a certain set of process parameters. The validated SPH model can serve as an effective tool to predict and better understand the extreme thermomechanical conditions during the FSE process.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2018

Experimental and Numerical Investigation on Vibration of Sandwich Plates with Honeycomb Cores Based on Radial Basis Function

The vibration characteristic of the sandwich plate with a honeycomb core was investigated by experimental measurements and numerical calculation based on radial basis function (RBF). RBF method was used not only in the meshless approach but also in the post-processing of the experimental data. During the experiment, amplitude-fluctuation electronic speckle pattern interferometry was applied to access the resonant frequencies and the corresponding vibration mode shapes simultaneously. Then RBF method was used to improve the quality of patterns and reconstruct the out-of-plane vibration amplitude after fringe analysis. As for numerical calculation, the modal parameters were numerically predicted using the first-order shear deformation theory. The computation approach was based on collocation with multi-quadric radial basis function. To understand the influence of the thickness of face sheet on dynamic behaviors, three types of specimens with different thickness were tested and analyzed. Of particular interest was that the vibration modes show veering due to the thickness increment. Furthermore, the numerical predicted results were compared with the experimental measurements for the first five modes. They are in good agreement with each other for resonant frequencies, mode shapes and relative out-of-plane amplitudes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental Testing and Numerical Modeling of Ballistic Impact on S-2 Glass/SC 15 Composites

Here, the work presented in this paper details both an experimental program and an associated numerical modeling effort to characterize and predict the ballistic response of S-2 glass/SC15 epoxy composite panels. The experimental program consisted of ¼ inch diameter soft carbon steel spheres impacting ¼ and ½ inch thick flat composite panels at velocities ranging from 220 to 1570 m/s. High speed cameras were used to capture the impact event and resulting residual velocity of the spheres for each test configuration. After testing, each panel was inspected both visually and with ultrasonic C-scan techniques to determine the extent and depth of damage imparted on the panel by the impactor. The numerical modeling efforts utilized the anisotropic multi-constituent composite model (MCM) within the CTH shock physics hydrocode. The MCM model allows for evaluation of damage at the constituent level through continuum averaged stress and strain fields. The model also accounts for the inherent coupling of the equation of state and strength response that occurs in anisotropic composite materials. Finally, the simulation results are compared against the experimentally measured residual velocity as a quantitative metric and against the measured damage extent and patterns as a qualitative metric. The comparisons show good agreement in residual velocity and damage extent.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A combined theoretical and experimental study of the phase coexistence and morphotropic boundaries in ferroelectric-antiferroelectric-antiferrodistortive multiferroics

The physical nature of the ferroelectric (FE), ferrielectric (FEI) and antiferroelectric (AFE) phases, their coexistence and spatial distributions underpins the functionality of antiferrodistortive (AFD) multiferroics in the vicinity of morphotropic phase transitions. In this work, using Landau-Ginzburg-Devonshire (LGD) phenomenology and a semi-microscopic four sublattice model (FSM), we explore the behavior of different AFE, FEI, and FE long-range orderings and their coexistence at the morphotropic phase boundaries in FE-AFE-AFD multiferroics. These theoretical predictions are compared with the experimental observations for dense Bi 1-y R y FeO 3 ceramics, where R is Sm or La atoms with the fraction 0 ≤ y ≤ 0.25, as confirmed by the X-ray diffraction (XRD) and Piezoresponse Force Microscopy (PFM). These complementary measurements were used to study the macroscopic and nanoscopic transformation of the crystal structure with doping. The comparison of the measured and calculated AFE/FE phase fractions demonstrate that the LGD-FSM approach well describes the experimental results obtained by XRD and PFM for Bi 1-y R y FeO 3 . Hence, this combined theoretical and experimental approach provides further insight into the origin of the morphotropic boundaries and coexisting FE and AFE states in model rare-earth doped multiferroics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The atomic-level structure and stability of interfaces of Pt nanoparticles in alumina: An experimental and computational evaluation

The atomic-level structure of interfaces between Pt and a transition form of Al2O3 were studied using a combination of electron microscopy and first principles calculations. A model system of Pt nanoprecipitates in Al2O3 were formed in sapphire wafers via high-energy ion implantation of Pt followed by thermal annealing at 1000 °C in air. The Pt nanoparticles took the form of tetrahedra and truncated tetrahedra primarily bound by {111}Pt facets. The high prevalence of these facets motivated the development of density functional theory (DFT) based models of (111)Pt interfaces with six different chemical terminations of ( 2 ¯ 01 ) θ-alumina. The atomic-level structure of the Pt/Al2O3 interfaces was characterized with aberration-corrected scanning transmission electron microscopy (STEM) and the experimental images were compared to STEM image simulations of the DFT models. The model interface with Pt bonded to oxygen-terminated θ-Al2O3, with the Pt located on top of the O and with an underlying layer of octahedral Al, provided the best match to the experimental images. This interfacial termination is also the most stable for the thermal annealing conditions used based on thermodynamic calculations of the interfacial energy as a function of temperature and oxygen partial pressure. This experimentally verified model provides a basis for improving models of Pt/γ-alumina interfaces.

Clauser, A L↗
DOE OSTI2018

Thermal scattering law of C 2 H 4 n : Integrating experimental data with DFT calculations

Improvements in determination of the thermal scattering law of moderator materials (measuring, calculating and validating) are important for accurate prediction of neutron thermalization in nuclear systems. In this paper a methodology for producing thermal scattering libraries from the experimental data for polyethylene C 2 H 4 n is discussed. Double differential scattering cross section (DDSCS) experiments were performed at the Spallation Neutron Source of Oak Ridge National Laboratory (SNS ORNL). New scattering kernel evaluations, based on phonon spectrum for C 2 H 4 n , are created using the NJOY2016 code. Two different methods were used: direct and indirect geometry neutron scattering at ARCS and SEQUOIA, and VISION instruments, respectively, where the phonon spectrum was derived from the dynamical structure factor S(Q, ω ) obtained from the measured DDSCS. In order to compare and validate the newly created library, the experimental setup was simulated using MCNP6.1. Compared with the current ENDF/B-VII.1, the resulting RPI C 2 H 4 n libraries improved both double differential scattering and total scattering cross sections. A set of criticality benchmarks containing C 2 H 4 n from HEU-MET-THERM resulted in an overall improved calculation of K eff , although the libraries should be tested against benchmarks more sensitive to C 2 H 4 n . The DFT + oClimax method is used and is shown to be most comprehensive method for analysis of moderator materials. Finally, the importance of DFT + oClimax method lies in the fact that it can be validated against all data measured at VISION, ARCS and SEQUOIA, and experimental total scattering cross section measurements.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Design of an experimental facility with a unit cell test section for studies of the lower plenum in prismatic high temperature gas reactors

A proposed design for a Generation IV reactor is the very-high temperature reactor (VHTR), which employs helium as the primary coolant. Although many advantages exist with this design, a number of challenges remain. One such area of concern is the turbulent mixing of non-isothermal flows in the lower plenum, where an array of coolant jets collectively mix and traverse around a series of structural support posts before exiting the core. Neighboring jets in the lower plenum could experience temperature differences as high as 300–400 K, causing potential hot streaking in the support posts. Additional problems could occur further downstream if the level of non-uniformity in the temperatures is too high (e.g, inducing thermal stresses on gas turbine blades). Therefore, it is important that adequate tools exist to predict the turbulent mixing within the VHTR lower plenum. This task remains difficult to achieve due to the complex geometry and flow physics that dictate the mixing. Various modeling approaches can only be assessed using data acquired from a carefully designed experimental facility. This paper presents details of such a facility, where high-fidelity measurements can be acquired for a scaled portion of the lower plenum defined herein as a ‘‘unit cell”, which consists of a hexagonal array of jets whose flow is directed into a test section with support posts positioned between neighboring jets, and subjected to a crossflow. Through adjusting velocity and temperature conditions at the jet inlets, different locations within the lower plenum can be experimentally simulated. System response quantities (SRQs) include both temperature and velocity measurements, captured via multiple thermocouples embedded in each post, and particle image velocimetry (PIV), respectively. These SRQs provide assessment metrics for both the momentum and energy models present in current computational solvers, and therefore the experimental facility is a valuable source for validation data. Another benefit is a more comprehensive understanding of the thermal-hydraulic loading conditions and flow physics present in the VHTR lower plenum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗