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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Rate-Dependent Dynamic Cylindrical Cavity Expansion Equations for Conical- and Ogival-Nosed Projectiles

The dynamic cylindrical cavity expansion of rate-dependent materials was previously derived by Warren to examine the effects of strain-rate sensitivity on the radial stress acting on a perforating projectile. However, the equations presented were largely analytical and were not further applied to predict the ballistic performance of ductile target plates. The current work expands on Warren’s derivation to model the dynamics of conical and ogival geometries, and the rate-dependent model is compared to prior experimental results of 7.62-mm APM2 rounds impacting 6061-T6511 aluminum alloy plates. The results show that including rate effects improves the ballistic performance prediction, even for a marginally strain-rate sensitive material such as Al6061-T651. However, existing semi-empirical variations of the cavity expansion model can provide the same degree of accuracy if target material rate-sensitivity parameters are not readily available.

36 MATERIALS SCIENCE↗
DOE OSTI2019

State-selective and total cross sections for electron capture from the K-shell of multi-electron atoms by fully stripped projectiles

Capture of a K-shell electron by bare fast ions H{sup +}, He{sup 2+} and Li{sup 3+} from multi-electron atomic targets (carbon, nitrogen, oxygen, neon and argon) is theoretically studied by means of the four-body boundary-corrected first Born approximation. In a wide impact energy interval ranging from 100 to 40 000 keV/amu, extensive tables of the obtained state-selective cross sections Q{sub nlm} are presented for each individual final hydrogen-like state described by the usual quantum numbers {n,l,m}. The total cross sections Q{sub nl}, Q{sub n} and Q{sub tot} for capture summed over the quantum numbers m, {l,m} and {n,l,m}, respectively, are also reported. Theoretical cross sections Q{sub tot} are found to compare favorably with the corresponding experimental data. The maximal value of the principal quantum number n has been taken to be n=4, which satisfies the relationship n≥Z{sub P}, where Z{sub P} is the nuclear charge of the projectile. The tabulated state-selective cross sections Q{sub nlm} for single-electron capture by swift nuclei from multi-electron atoms are the first results in the literature on the theory of four-body collisions. The present data for the examined capture processes are of notable interest for many fundamental and applied problems in various interdisciplinary fields ranging from fusion research, plasma physics, astrophysics to radiotherapy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Investigating the relationship between radial pre-stress magnitude and ballistic projectile dwell in heavy confined ceramic targets

A series of bare silicon carbide ceramic armour disks were manufactured with high-strength steel containment to induce varying magnitudes of radial pre-stress. The induced radial stresses, ranging from 0 to 900 MPa, were measured via neutron diffraction and verified by comparison with numerical calculations. Four targets of each configuration, referred to as slip-fit, moderate pre-stress, and high pre-stress, were subject to ballistic testing with hemispherical-nose, tungsten heavy alloy long rod projectiles to determine the interface defeat transition velocity. In-situ diagnostics were unsuccessful in aiding the identification of interface defeat, necessitating a reliance on post-mortem assessment. A transition velocity of approx. 1000 m/s was identified for the unstressed target, increasing to approx. 1200 m/s for the pre-stressed configurations. No performance effect was discernible between the moderate (372 MPa) and high (899 MPa) pre-stress configurations, suggesting that an optimal performance may be achieved for lower pre-stress levels (i.e., <372 MPa). Additionally, the test results were compared with four semi-analytical predictions of interface defeat performance and good agreement was found, albeit with significant range in the model predictions.

42 ENGINEERING↗
DOE OSTI2017

High-velocity projectile impact induced 9R phase in ultrafine-grained aluminium

Aluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations reveal the formation mechanisms of the 9R phase in aluminium. This study sheds lights on a deformation mechanism in metals with high stacking fault energies.

42 ENGINEERING↗
DOE OSTI2014

Feasibility of Isotope Harvesting at a Projectile Fragmentation Facility: 67Cu

The work presented here describes a proof-of-principle experiment for the chemical extraction of 67Cu from an aqueous beam stop at the National Superconducting Cyclotron Laboratory (NSCL). A 76 MeV/A 67Cu beam was stopped in water, successfully isolated from the aqueous solution through a series of chemical separations involving a chelating disk and anion exchange chromatography, then bound to NOTA-conjugated Herceptin antibodies, and the bound activity was validated using instant thin-layer chromatography (ITLC). The chemical extraction efficiency was found to be 88 ± 3% and the radiochemical yield was ≥95%. These results show that extraction of radioisotopes from an aqueous projectile-fragment beam dump is a feasible method for obtaining radiochemically pure isotopes.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2011

Detection of atomic and molecular mega-electron-volt projectiles using an x-ray charged coupled device camera

We show that an x-ray charge coupled device (CCD) may be used as a particle detector for atomic and molecular mega-electron-volt (MeV) projectiles of around a few hundred keV per atomic mass unit. For atomic species, spectroscopic properties in kinetic energy measurements (i.e., linearity and energy resolution) are found to be close to those currently obtained with implanted or surface barrier silicon particle detectors. For molecular species, in order to increase the maximum kinetic energy detection limit, we propose to put a thin foil in front of the CCD. This foil breaks up the molecules into atoms and spreads the charges over many CCD pixels and therefore avoiding saturation effects. This opens new perspectives in high velocity molecular dissociation studies with accelerator facilities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Half-life measurements of isomeric states populated in projectile fragmentation

The half-lives of excited isomeric states observed in {sup 195}Au, {sup 201}Tl and {sup 215}Rn are reported for the first time. Delayed {gamma}-rays were correlated with nuclei produced in the projectile fragmentation of relativistic {sup 238}U ions, unambiguously identified in terms of their atomic number (Z) and mass-to-charge ratio (A/Q) after traversing an in-flight separator. The observation of a long-lived isomeric state in {sup 195}Au with t{sub 1/2} = 16{sub -4}{sup +8}{mu}s is presented. Two shorter-lived isomeric states were detected in {sup 201}Tl and {sup 215}Rn with t{sub 1/2} = 95{sub -21}{sup +39} and 57{sub -12}{sup +21} ns respectively. In total 24 isomeric states were identified in different nuclei from Pt to Rn (A {approx} 200) during the current study, the majority of which were previously reported. The wealth of spectroscopic data provides the opportunity to determine the isomeric ratios over a wide range of Z, A and angular momentum (I h) of the reaction products. In particular, high-spin states with I Greater-Than-Or-Equivalent-To 18 h provide a robust test of theoretical models of fragmentation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗