Search NASA⌕ Search

SEARCH · Search NASA

Results for “PLASTICS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Linking strain anisotropy and plasticity in copper metallization

The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Crystal Plasticity Modeling of Void Growth on Grain Boundaries in Ni-Based Superalloys

In this study, we explore the effect of misorientation angles of crystal orientations between two grains along the grain boundary (GB) on void growth behavior in polycrystalline Ni-based superalloys by using a crystal plasticity finite element method. Quantitative analysis is conducted to study the coupled roles of the crystal orientation and stress triaxiality in void growth in bicrystals. Based on our simulation results, we find that, as the main loading axis perpendicular to the GB, voids grow more slowly on tilt GBs in bicrystals than those in single and bicrystal samples with twist GBs, while the void growth in single- and bicrystal samples with twist GBs exhibited almost the same rate and increased with the stress triaxiality levels. The interaction between two crystals bonded with the GB activates the effective Schmid factors in each crystal, which results in asymmetric distribution of the equivalent plastic strain around the void and induces distinct irregularly shaped voids during deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Plastic deformation mechanism of calcium-silicate hydrates determined by deviatoric-stress Raman spectroscopy

Highlights: • C-(A-)S-H samples under stress were characterized at the bond and grain level. • Small angle scattering showed that 720 MPa reduced grain thickness by 30%. • In-situ Raman showed that cross-linked C-A-S-H slips along its intralayer. • However, in-situ Raman showed that C-S-H slips along the interlayer. • In-situ Raman also showed a growth in CaCO{sub 3}, indicating fracture in both samples. Creep of the cement matrix affects the structural stability of concrete. In Portland cements, the creep is largely controlled by the binding phase calcium-(aluminum-)silicate-hydrate, or C-(A-)S-H. This phase has a lamellar structure and under deviatoric stress aligns its c-axis with the principal stress. However, the limiting resistance to this reorientation is unknown at the nanocrystalline level. Small-angle X-ray scattering shows that the lamellae thickness decreases under 100's MPa deviatoric stress. Deviatoric stress Raman spectroscopy shows that there are two ways that this break-up can occur. If the material's silicate chains are cross-linked, then strain in SiO bonds does not increase above certain stresses, indicating a relaxation adjacent to the SiO bond. If the chains are not cross-linked, then the silicate chains are broken up by rastering against each other, introducing defects. These results show that the plastic deformation of C-(A-)S-H is relevant for Portland cement creep.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microband induced plasticity and the temperature dependence of the mechanical properties of a carbon-doped FeNiMnAlCr high entropy alloy

Highlights: • A superior fcc HEA with the strength of 1.5 GPa at the cryogenic condition is developed. • The strengthening mechanisms of HEAs at different temperatures are clarified. • The temperature dependence of MBIP effect is revealed. - Abstract: The uniaxial mechanical properties of the high entropy alloy (HEA) Fe{sub 40.4}Ni{sub 11.3}Mn{sub 34.8}Al{sub 7.5}Cr{sub 6} doped with 1.1 at.% C have been determined for both the as-cast and recrystallized states at temperatures from 77 to 973 K. Very high yield strengths were obtained at 77 K of 928 MPa for the as-cast HEA and 1037 MPa for the recrystallized HEA. The yield strength decreased sharply to 293 K and more slowly to 973 K, where it was ~200 MPa [11] in both conditions. The lattice friction stress, which results from the increase of the Peierls barrier, was the major contributor to the large yield strength at 77 K. On the other hand, the grain boundaries lose their strengthening ability at a high temperature, which largely accounts for the sharp drop in yield strength of the fine-grained (5 μm) recrystallized HEA at 973 K. The elongation to failure was highest at 293 K and 673 K with the lowest values at 77 K. Transmission electron microscopy was used to study the effects of temperature on the deformation mechanisms of the HEAs, especially the temperature dependence of the microband-induced plasticity effect. At temperatures ranging from 77 K to 673 K microbands form in the as-cast HEA, while dislocation clusters were observed in the recrystallized HEA over this temperature range. Only tangled dislocations were found at 973 K for both the as-cast and recrystallized HEA due to thermally-activated deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2016

The Hugoniot and chemistry of ablator plastic below 100 GPa

The equation of state of glow discharge polymer (GDP) was measured to high precision using the two-stage light gas gun at Lawrence Livermore National Laboratory at pressures up to 70 GPa. Both absolute measurements and impedance matching techniques were used to determine the principal and secondary Hugoniots. GDP likely reacts at about 30 GPa, demonstrated by specific emission at 450 nm coupled with changes to the Hugoniot and reshock points. As a result of these reactions, the shock pressure in GDP evolves in time, leading to a possible decrease in pressure as compression increases, or negative compressibility, and causing complex pressure profiles within the plastic. Velocity wave profile variation was observed as a function of position on each shot, suggesting some internal variation of GDP may be present, which would be consistent with previous observations. The complex temporal and possibly structural evolution of GDP under shock compression suggests that calculations of compression and pressure based upon bulk or mean measurements may lead to artificially low pressures and high compressions. Evidence for this includes a large shift in calculating reshock pressures based on the reflected Hugoniot. These changes also suggest other degradation mechanisms for inertial confinement fusion implosions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

A study of CR-39 plastic charged-particle detector replacement by consumer imaging sensors

Consumer imaging sensors (CIS) are examined for real-time charged-particle detection and CR-39 plastic detector replacement. Removing cover glass from CIS is hard if not impossible, in particular for the latest inexpensive webcam models. We show that $10-class CIS are sensitive to MeV and higher energy protons and α-particles by using a {sup 90}Sr β-source with its cover glass in place. Indirect, real-time, high-resolution detection is also feasible when combining CIS with a ZnS:Ag phosphor screen and optics. Noise reduction in CIS is nevertheless important for the indirect approach.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Machining Specific Fourier Power Spectrum Profiles into Plastics for High Energy Density Physics Experiments [Machining Specific Fourier Power Spectrum Profiles into Plastics for HEDP Experiments]

In this paper, the High Energy Density Physics program at Los Alamos National Laboratory (LANL) has had a multiyear campaign to verify the predictive capability of the interface evolution of shock propagation through different profiles machined into the face of a plastic package with an iodine-doped plastic center region. These experiments varied the machined surface from a simple sine wave to a double sine wave and finally to a multitude of different profiles with power spectrum ranges and shapes to verify LANL’s simulation capability. The MultiMode-A profiles had a band-pass flat region of the power spectrum, while the MultiMode-B profile had two band-pass flat regions. Another profile of interest was the 1-Peak profile, a band-pass concept with a spike to one side of the power spectrum. All these profiles were machined in flat and tilted orientations of 30 and 60 deg. Tailor-made machining profiles, supplied by experimental physicists, were compared to actual machined surfaces, and Fourier power spectra were compared to see the reproducibility of the machining process over the frequency ranges that physicists require.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

A comparison of plastic and visco-plastic constitutive models for accurate predictions in PM-HIP

Powder metallurgy hot isostatic pressing (PM-HIP) is an advanced manufacturing process that can efficiently produce near net shape parts with high material utilization and uniform microstructures. While the PM-HIP process is used frequently to produce small-scale components, its application to large-scale components is still limited due to inadequate understanding of its complex processes that cause unpredictable post-HIP shape distortions. A computational model can be a cost-effective alternative to exhaustive experimentation required to understand the PM-HIP process fully. Therefore, we present a comparison of plastic and visco-plastic models that are frequently used to model the PM-HIP process. We show that the predictions of powder densification behavior and shape distortions obtained from both the models are similar under most conditions and agree well with experimental observations.

Sarkar, Subrato [ORNL]↗
DOE OSTI2013

Characterization of wood plastic composites made from landfill-derived plastic and sawdust: Volatile compounds and olfactometric analysis

Graphical abstract: This work details the characterization of VOCs of WPC, produced from residual materials which would have landfills as current destination, and evaluates their odor profile. Highlights: ► More than 140 volatile compounds were identified in raw materials and WPC products. ► Markers were related to the thermal degradation, sawdust or coupling agents. ► WPC prototype showed a characteristic odor profile of burnt, sweet and wax-like. ► Aldehydes, carboxylic acids, ketones and phenols were odor descriptors of WPC. - Abstract: Application of wood plastic composites (WPCs) obtained from recycled materials initially intended for landfill is usually limited by their composition, mainly focused on release of volatile organic compounds (VOCs) which could affect quality or human safety. The study of the VOCs released by a material is a requirement for new composite materials. Characterization and quantification of VOCs of several WPC produced with low density polyethylene (LDPE) and polyethylene/ethylene vinyl acetate (PE/EVA) films and sawdust were carried out, in each stage of production, by solid phase microextraction in headspace mode (HS-SPME) and gas chromatography–mass spectrometry (GC–MS). An odor profile was also obtained by HS-SPME and GC–MS coupled with olfactometry analysis. More than 140 compounds were observed in the raw materials and WPC samples. Some quantified compounds were considered WPC markers such as furfural, 2-methoxyphenol, N-methylphthalimide and 2,4-di-tert-butylphenol. Hexanoic acid, acetic acid, 2-methoxyphenol, acetylfuran, diacetyl, and aldehydes were the most important odorants. None of the VOCs were found to affect human safety for use of the WPC.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Online Characterization of Mixed Plastic Waste Using Machine Learning and Mid-Infrared Spectroscopy

To recycle the mixed plastic wastes (MPW), it is important to obtain the compositional information online in real time. We present a sensing framework based on a convolutional neural network (CNN) and mid-infrared spectroscopy (MIR) for the rapid and accurate characterization of MPW. The MPW samples are placed on a moving platform to mimic the industrial environment. The MIR spectra are collected at the rate of 100 Hz, and the proposed CNN architecture can reach an overall prediction accuracy close to 100%. Therefore, the proposed method paves the way toward the online MPW characterization in industrial applications where high throughput is needed.

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

The influence of hold time on the onset of plastic deformation in silicon

The transformation of diamond-cubic silicon to the metallic β-Sn phase is known to be “sluggish,” even when the critical pressure (∼11 GPa) for the transformation is reached. In this letter, we use nanoindentation to apply pressures to just above the critical threshold. In this regime, the sample displays purely elastic behavior at zero hold time. As the hold time at maximum load is increased up to 180 s, the percentage of indents that plastically deform also increase. Interestingly, the indents deform via one of two distinct processes: either via a phase transformation to a mixed bc8/r8-Si end phase, or by initiation of crystalline defects. Raman spectroscopy and cross-sectional transmission electron microscopy are used to show that the two deformation mechanisms are mutually exclusive under the indentation conditions presented here, and elastic modelling was utilized to propose a model for this mutually exclusive behavior. Hence, this behavior enhances the potential for application of the exotic bc8/r8-Si end phase.

36 MATERIALS SCIENCE↗