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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Testing of the Veggie Vegetable Production System on the International Space Station

The Veggie vegetable production system has been flying on the International Space Station since 2014, with a second Veggie chamber added in 2017. Veggie is a simple, low power, flexible platform for space plant cultivation. Since 2014, over a dozen crop cycles have been conducted in Veggie. Primarily leafy green crops have been grown, and many of these have been used to supplement the crew diet. Flowers were also grown, and the seeds returned produced viable progeny. In addition to the crop plants, Veggie has been used as a platform for model plants grown in Petri dishes or custom magenta jar chambers. Other used have included algal culture and an education seed germination experiment. Science in Veggie has focused on the plant microbiome, the chemistry and food safety of space-grown produce, the impacts of light quality on crop growth, and the behavioral health benefits of cultivating and eating space crops. Veggie is allowing testing and maturation of NASA’s early-stage space crop production research in a relevant environment, and the lessons that we are learning from this research are helping to shape future exploration scenarios. This research was funded by NASA Space Biology and NASA’s Human Research Program.

Veggie↗
NASA NTRSDate not supplied

Testing of the Veggie Vegetable Production System on the International Space Station

The Veggie vegetable production system has been flying on the International Space Station since 2014, with a second Veggie chamber added in 2017. Veggie is a simple, low power, flexible platform for space plant cultivation. Since 2014, over a dozen crop cycles have been conducted in Veggie. Primarily leafy green crops have been grown, and many of these have been used to supplement the crew diet. Flowers were also grown, and the seeds returned produced viable progeny. In addition to the crop plants, Veggie has been used as a platform for model plants grown in Petri dishes or custom magenta jar chambers. Other used have included algal culture and an education seed germination experiment. Science in Veggie has focused on the plant microbiome, the chemistry and food safety of space-grown produce, the impacts of light quality on crop growth, and the behavioral health benefits of cultivating and eating space crops. Veggie is allowing testing and maturation of NASA’s early-stage space crop production research in a relevant environment, and the lessons that we are learning from this research are helping to shape future exploration scenarios. This research was funded by NASA Space Biology and NASA’s Human Research Program.

Veggie↗
DOE OSTI2022

Fatigue-crack propagation behavior in a high-carbon chromium SUJ2 bearing steel: Role of microstructure

High-carbon chromium martensite steels are commonly selected for bearing components in the power generation, automotive and aerospace industries where fatigue failure is a major concern. Accordingly, it is of importance to elucidate the structure-property relationships governing the fatigue properties of such bearing steels. Here, the role of microstructure in influencing the fatigue-crack propagation behavior of a high-carbon chromium SUJ2 bearing steel is examined with emphasis on three martensitic structures: (i) a fine-grained (~10 μm) structure with intragranular (but no intergranular) carbides, (ii) a coarser-grained (~25 μm) structure with discontinuous grain-boundary carbides primarily near triple junctions, and (iii) a coarse-grained (~31 μm) structure with continuous grain-boundary carbides. Although growth rates were fairly similar above ~10 -8 m/cycle, significant differences in behavior were observed at lower, near-threshold growth rates; specifically at a load ratio of 0.1, the ΔKth fatigue threshold was increased from 3.8 MPa m ½ in the fine-grained structure to 5.9 to 6.3 MPa m ½ in the two coarser-grained structures. The dominant factor governing such near-threshold behavior was found to be crack-tip shielding from roughness-induced crack closure, which was most pronounced in the coarser-grained structures; additionally, shielding from crack deflection and branching was apparent in these structures as the crack propagated through the network of intersecting martensite lamellae within the coarse grains. Compared to high-strength stainless steels and low-strength carbon steels, the fine-grained SUJ2 steel displays an exceptional combination of high strength and fatigue-crack growth resistance and is considered to be a superior structural alloy for bearing applications.

36 MATERIALS SCIENCE↗
NASA NTRS2019

Testbed Requirements to Enable New Observing Strategies

Emerging capabilities to integrate instruments on smallsats, airborne platforms and in situ devices into an intelligent, distributed observing strategy show great promise for measuring Earth science natural phenomena and physical processes that have not previously been characterized. To reduce the threshold for success in deploying such an intelligent, integrated observing strategy, a ground-based testbed system is proposed. Virtually all of the technologies needed for using such a tool have matured to the point of being used, individually. Virtually none of the technologies have been deployed, working together. The technologies to be deployed should be integrated into a working "breadboard" where the components can be debugged and performance and behavior characterized and tuned-up. A system of this complexity should not be expected to work without full integration and experimental characterization. Further, and perhaps more importantly, in order to successfully propose a space-based element to this strategy, teams must convince the relevant science community that the risk is low enough to warrant the investment. The main benefit of the testbed is to retire the risk of integrating these new technologies and increase the Technology Readiness Level (TRL) of each component as well as the System Readiness Level (SRL) of the integrated system.

Little, Mike↗
DOE OSTI2021

A constitutive structural parameter c b for the work hardening behavior of additively manufactured Ti-6Al-4V

The mechanical behavior of Ti-6Al-4V produced by additive manufacturing processes is assessed as based on a model derived from the Kocks–Mecking relationship. A constitutive parameter c b is derived from a linear Kocks–Mecking relationship for the microstructure that is characteristic of the work hardening behavior. The formulation for c b is determined by considering the plastic strain between the strengths at the proportional limit and the plastic instability. In this way, the model accommodates the variation in work hardening behavior observed when evaluating material as produced and tested along different orientations. The modeling approach is presented and evaluated for the case of Ti-6Al-4V additively manufactured materials as tested under quasi-static uniaxial tension. It is found that different test specimen orientations, along with postbuild heat treatments, produce a change in the microstructure and plasticity behavior which can be accounted for in the corresponding change of the c b values.

36 MATERIALS SCIENCE↗
DOE OSTI2026

U-net architected deep material network training with microstructure local field information

The Deep Material Network (DMN) has recently emerged as a powerful reduced-order modeling framework for simulating the mechanical response of heterogeneous materials such as composites. Unlike most data-driven approaches that directly learn a material’s response under prescribed loading, the DMN acts as a homogenization operator, learning the kinematic constraints and mechanical interactions of the underlying microstructure. However, traditional DMN training relies exclusively on homogenized effective properties derived from Direct Numerical Simulations (DNS), discarding the rich local field data that govern microstructural interactions. In this work, we extend the DMN framework to incorporate such local field information into the offline training process. Utilizing a U-Net architecture, we augment the DMN training objective to include the first and second statistical moments of the local stress fields obtained from linear DNS. This ensures that the learned network topology not only fits the effective stiffness but also accurately reflects the internal local stress and strain partitioning of the microstructure. The results confirm that supervising the localization process during training yields a superior surrogate model, reducing local prediction errors by an order of magnitude and significantly improving generalization to unseen nonlinear constitutive behaviors compared to traditional DMNs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Contact Angle Measurements Using Sessile Drop and Micro-CT Data from Six Sandstones

Numerous sessile drop and micro-computed tomography (micro-CT) studies have been conducted to quantify Geologic Carbon Storage formation wettability by measuring static contact angles (θ); however, the influence of pore geometry remains unknown. In this work, six sandstones (Bandera Brown, Berea, Bentheimer, Mt. Simon, Navajo, and Nugget) are used to measure θ using the two aforementioned experimental methods at identical testing conditions (45°C and 12.41 MPa). The range of θ measured at in situ conditions (micro-CT) exceeds those the range at ex situ (sessile drop method) conditions for all sandstones. However, when droplets with more representative in situ diameters are analyzed, θ averages show ex situ θ exceed those of in situ θ. Pore geometry does influence local θ, but the size of ex situ droplets relative to pore size appears to influence θ. This is an important to consider for future sessile drop studies used for analysis of CO 2 behavior in carbon storage reservoirs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The combined effects of hydrogen and aging condition on the deformation and fracture behavior of a precipitation-hardened nickel-base superalloy

The effect of hydrogen (H) on the deformation behavior of Monel K-500 in various isothermal heat treatment conditions (non-aged, under-aged, peak-aged, and over-aged) was assessed via uniaxial mechanical testing. H-charged and non-charged specimens were strained to failure to facilitate a comparison of ductility, fracture surface morphology, strength, and work hardening behavior. For all examined heat treatment conditions, H charging leads to a significant reduction in ductility, which is accompanied by a consistent change in fracture surface morphology from ductile microvoid coalescence to brittle intergranular fracture. While H charging led to a systematic enhancement in the yield strength of all heat treatments, the three age-hardened conditions exhibited a more than 2-fold increase relative to the non-aged heat treatment. This suggests that H modifies the dislocation–precipitate interactions, which also manifest themselves through changes in work hardening metrics related to the dislocation storage and recovery rates. In particular, the H-charged peak-aged specimen exhibited a significant increase in initial hardening (dislocation storage) rate relative to the H-charged under-aged specimen. Transmission electron microscopy of these samples revealed the onset of widespread dislocation looping in the H-charged peak-aged sample, in addition to the planar slip bands characteristic of the non-charged condition. This result suggests that hydrogen induces the particle shearing-to-looping transition at smaller particle sizes. Possible mechanistic explanations for this observed behavior are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mesoscopic-scale complexity in macroscopically-uniform plastic flow of an Al 0.3 CoCrFeNi high-entropy alloy

The concept of a smooth and homogeneous plastic flow of solids is nowadays constantly challenged by various observations of the self-organization of crystal defects on mesoscopic scales pertaining, e.g., to acoustic emission or the evolution of the local strain field. Such investigations would be of particular interest for High-Entropy Alloys (HEAs) characterized by extremely complex microstructures. However, the complexity of their deformation has been only studied in relation to the jerky flow. The present work explores a mesoscale complexity of the macroscopically-smooth plastic flow of an Al 0.3 CoCrFeNi alloy. Here, an inclusive approach involving various experimental methods and complementary nonlinear analyses allowed to reveal transitions between distinct dynamical regimes, which may be assimilated with noises of different colors, in particular the blue noise that is rarely observed in complex systems, and various kinds of reddened behavior. Such findings provide significant new insights into the micro/macro transition in the deformation behavior of HEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Calculation of mode lifetimes in weakly anharmonic solids using self-consistent ensemble eigenstates of the Liouvillian

Recent schemes for the efficient calculation of vibrational mode frequencies and lifetimes in weakly anharmonic systems such as solid crystal structures have shown promise, with simple relationships being observed between low order moments of the Liouvillian and the observed lifetime. While only shown empirically, two parameters seemed sufficient to determine the lifetime to high accuracy over a large range of temperatures for a few simple low degree of freedom models and a Lennard–Jones solid. In this paper we analytically reproduce the numerically observed relationship using a few generally applicable assumptions about the density of states. This advance is made by studying the autocorrelation based on an “ensemble eigenstate” of the Liouvillian. We propose the use of this ensemble eigenstate as the basis for autocorrelations to simplify calculations in richer systems. Finally, an analysis is also performed of the relationship between canonical and microcanonical autocorrelation functions and a long standing error in the long time behavior of such functions originally presented by Sen, Sinkovits, and Chakravarti is corrected.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Particle collisionality in scaled kinetic plasma simulations

Kinetic plasma processes, such as magnetic reconnection, collisionless shocks, and turbulence, are fundamental to the dynamics of astrophysical and laboratory plasmas. Simulating these processes often requires particle-in-cell (PIC) methods, but the computational cost of fully kinetic simulations can necessitate the use of artificial parameters, such as a reduced speed of light and ion-to-electron mass ratio, to decrease expense. While these approximations can preserve overall dynamics under specific conditions, they introduce nontrivial impacts on particle collisionality that are not yet well understood. In this work, we develop a method to scale particle collisionality in simulations employing an artificial speed of light and/or an artificial ion-to-electron mass ratio. By introducing species-dependent scaling factors, we independently adjust inter- and intra-species collision rates to better replicate the collisional properties of the physical system. Our approach maintains the fidelity of electron and ion transport properties while preserving critical relaxation rates, such as energy exchange timescales, within the limits of weakly collisional plasma theory. Furthermore, we demonstrate the accuracy of this scaling method through benchmarking tests against theoretical relaxation rates and connecting to fluid theory, highlighting its ability to retain key transport properties. Existing collisional PIC implementations can be easily modified to include this scaling, which will enable deeper insights into the behavior of marginally collisional plasmas across various contexts.

Totorica, S. R. [Princeton Univ., NJ (United State↗
DOE OSTI2024

Effects of neutron irradiation on hydrogen isotope permeation on W-Re

Hydrogen and deuterium permeation behavior for neutron damaged W and W-3 %Re was evaluated using a Plasma Driven Permeation device. For neutron damaged W-3 %Re at 773 K and 1473 K, precipitation of Re and Os was observed by atom probe tomography. Neutron irradiation introduced defect damage throughout the sample and enhanced H and D diffusion toward downstream side. The existence of irradiation damage by neutron irradiation was found to increase hydrogen isotope permeation. Moreover, the existence of Re has suppressed the formation of irradiation defects for hydrogen isotope trapping sites. Further, the recovery of irradiation defects by increasing the irradiation temperature led to the structural changes due to the diffusion of Re and Os, which also affected the hydrogen isotope permeation behavior.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Effect of hydrogen on plasticity of $α$-Fe: A multi-scale assessment

A multi-scale study was carried out to quantify the effect of interstitial hydrogen concentration on plasticity in $α$-Fe. Here, in this work, the influence of hydrogen on the screw dislocation glide behavior was examined across several length-scales. The insights obtained were integrated to provide an accurate continuum description for the effect of hydrogen on the dislocation based plasticity in polycrystalline $α$-Fe. At the outset of this work, a new Fe—H interatomic potential was formulated that enhanced the atomistic estimation of the variation in dislocation glide behavior in presence of hydrogen. Next, the dislocation core reconstruction observed due to the addition of hydrogen using atomistic simulations was validated with the help of large-scale DFT calculations based on the DFT-FE framework. Several atomistic simulations were carried out to comprehensively quantify the effect of hydrogen on the non-Schmid behavior exhibited during the dislocation glide in $α$-Fe. Finally, crystal plasticity simulations were carried out to understand the effect of hydrogen on the meso-scale deformation behavior of polycrystalline $α$-Fe.

36 MATERIALS SCIENCE↗