Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Li plasticity”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Investigating the Ability of Plastic Current Collectors to Isolate Internal Shorts

Metallized plastic current collectors in Li-ion cells reduce mass and reduce the internal short circuit hazard compared to aluminum and copper foils. Shorts induced by nail and by our internal short circuit device were performed on control 18650 cells and on cells with the collectors replaced with metallized polyester and aramid films. Tests were performed inside our fractional thermal runaway calorimeter to quantify the heat transferred and its distributions and those runs done at a synchrotron yielded fascinating very high speedX-ray videography. These show tolerance to nail penetration and activation of defect internal shorts and when thermally forced into thermal runaway, the heat output is significantly reduced. Very high resolutionCT scans, cross sections, and cell tear downs give insights into the thermal and mechanism for these plastic collectors.

Plastic Current Collectors↗
NASA NTRS2019

Metallized Plastic Current Collectors

Metallized plastic current collectors are an innovation patented by the Soteria Battery Innovation Group with the promise of isolating active material involved in an internal short by vaporizing and isolating the short from the rest of the cell electrode jellyroll or stack. Partnering with NREL, UCL, Coulometrics, and Soteria, NASA is leading a research effort into demonstrating the merits and understanding the phenomena of this safety innovation using prototype 18650 cylindrical cells vs control cells with standard metal foil current collectors. Cells with and without the plastic collector, with and without the on-demand internal short circuit device, and with polymer or cellulose separators were made. Safety evaluations were done with driving cells into thermal runaway (TR) with thermal and nail penetration triggers while inside our TR calorimeter and with ultra high speed X-ray videography provided at Synchrotrons. Preliminary results suggests that the thermally unstable plastic current collector innovation has great promise for preventing TR or reducing the severity of the TR output.

Li-ion cell↗
NASA NTRS2019

Automated Grain Yield Behavior Classification

A method for classifying grain stress evolution behaviors using unsupervised learning techniques is presented. The method is applied to analyze grain stress histories measured in-situ using high-energy X-ray diffraction microscopy (HEDM) from the aluminum-lithium alloy Al-Li 2099 at the elastic-plastic transition (yield). The unsupervised learning process automatically classified the grain stress histories into four groups: major softening, no work-hardening or softening, moderate work-hardening, and major work-hardening. The orientation and spatial dependence of these four groups are discussed. In addition, the generality of the classification process to other samples is explored.

Pagan, Darren C↗
NASA NTRS1980

The high energy cosmic ray detector for Spacelab II

A large cosmic ray detector to be flown on Spacelab II is presently under construction at the University of Chicago. The instrument, with a geometric factor of 5 sq m-ster, is designed to measure the elemental composition and the energy spectra of individual cosmic ray nuclei (Li to Fe) from 50 GeV/nucleon to several TeV/nucleon. Plastic scintillators are used for charge determination, and gas Cerenkov and transition radiation detectors for energy measurements. The instrument and its functions are described, and several test results that are important for an optimum design are discussed.

Lamport, J. E.↗
NASA NTRS1995

Differential neutron energy spectra measured on spacecraft low Earth orbit

Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the (sup 6) Li(n.x)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%.

Benton, E. V.↗
NASA NTRS2012

Validation of a Crystal Plasticity Model Using High Energy Diffraction Microscopy

High energy diffraction microscopy is used to measure the crystallographic orientation and evolution of lattice strain in an Al Li alloy. The relative spatial arrangement of the several pancake-shaped grains in a tensile sample is determined through in situ and ex situ techniques. A model for crystal plasticity with continuity of lattice spin is posed, where grains are represented by layers in a finite element mesh following the arrangement indicated by experiment. Comparison is drawn between experiment and simulation.

Beaudoin, A. J.↗
NASA NTRS1988

The Cosmic Ray Nuclei Experiment on the Spacelab-II mission

The Cosmic Ray Nuclei Experiment flown on the Spacelab-II mission was designed to measure the elemental composition of individual cosmic ray nuclei (Li to Ni) from 40 Gev/amu to several TeV/amu. The detector utilizes plastic scintillation counters for charge measurement, and gas Cerenkov and transition radiation detectors for energy measurements. The data analysis is in progress and results on the energy spectra are expected in the near future.

Grunsfeld, John Mace↗
NASA NTRS2012

Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

Hales, S. J.↗
NASA NTRS1991

Microstructural evolution during aging of an Al-Cu-Li-Ag-Mg-Zr alloy

Alloys in the Al-Cu-Li Ag-Mg subsystem were developed that exhibit desirable combinations of strength and ductility. These Weldalite (trademark) alloys, are unique for Al-Cu-Li alloys in that with or without a prior cold stretching operation, they obtain excellent strength-ductility combinations upon natural and artificial aging. This is significant because it enables complex, near-net shape products such as forgings and super plastically formed parts to be heat treated to ultra-high strengths. On the other hand, commercial extrusions, rolled plates and sheets of other Al-Cu-Li alloys are typically subjected to a cold stretching operation before artificial aging to the highest strength tempers to introduce dislocations that provide low-energy nucleation sites for strengthening precipitates such as the T(sub 1) phase. The variation in yield strength (YS) with Li content in the near-peak aged condition for these Weldalite (trademark) alloys and the associated microstructures were examined, and the results are discussed.

Kumar, K. S.↗