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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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89 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Impact Testing and Analysis of Modified Metal Slugs

This report summarizes initial results from a series of gun experiments which were conducted at the DICE facility. The target of these experiments was a modified metal slug composed of a tantalum/tungsten alloy (Ta-10W). The general geometry of the slug was a right circular cylinder with a through-hole cut normal to the cylinder's axis. In all experiments, hardened steel impactors were used, the desired impact velocity was 200 m/s, the slug was preheated to a target temperature of 175° C, photon doppler velocimetry (PDV) was used to measure the projectile velocity before and after impact, and the impact event was recorded with high-speed video. In two of the impacts the slug was oriented perpendicular to the projectile, while in the remaining two it was tilted 8° from normal. Initial high-speed speed video results showed slug failure in the tilted impact case, while the slug survived normal impacts. Recovery fixtures were used to preserve impacted slugs for future postmortem analysis. Discussions are included regarding improvements to potential future experiments involving these slugs.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2025

Impact Testing of Heat Source Exemplars

This report details the heat source impact testing performed at the Shock Thermodynamics Applied Research Facility (STAR). The purpose of these tests were to measure the impact behavior of a heated Ta-10W tantalum/tungsten alloy heat source exemplar. Each exemplar resembled a cylinder with a rectangular through-hole orthogonal to the cylinder axis-of-symmetry. In each test, the exemplar was impacted by a hardened steel impactor accelerated using the STAR air gun. The exemplars were impacted perpendicular to the through-hole and at an an angle to the cylindrical axis-of-symmetry. The exemplar bar stock source, impact angle, and impact velocity were varied throughout the testing series. High-speed video was used to measure dynamic impact behavior while photon doppler velocimetry (PDV) and shorting pins were used to measure the impact velocity. Foam support structures were used to thermally isolate the exemplar and provide a support structure which was non-perturbative to the impact event. Soft-catch techniques were used to minimize secondary impacts and enable recovery for detailed post-shot analysis. Results indicate positive correlation between exemplar fracture and the variables of impact velocity and impact angle. Exemplar fracture occurred consistently along a single corner of the through-hole.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Characterizing IHE Response to Multiple Shock Loading

The response of high explosives to shock loading is traditionally measured with a steady loading pressure. In many accident scenarios involving fragment impact, however, a loading duration that is shorter than the build up to detonation may occur. Fragments passing through multiple materials before reaching a high explosive charge may produce loading that is comprised of more than one shock wave. Additionally, the build up to detonation in high explosive corner turning loads the explosive a short duration pressure pulse, since rarefactions can often rapidly overtake the reactive wave. For these reasons, we have studied the response of the insensitive high explosive (IHE) materials PBX 9502 and LX-17 to complex loadings of varied intensity and duration. We refer to a single loading of limited duration as a “thin pulse”, whereas more complex scenarios were studied with an impactor that produces a double shock in the explosive. The following report presents experimental data and analyses of thin pulse shock initiation and double shock experiments designed to guide development of models of Insensitive High Explosives (IHEs) under controlled one-dimensional conditions relevant to accident scenarios and corner turning. Thin pulse shock initiation data on PBX 9502 and LX-17 were obtained under varied pulse duration, pressed density, and temperature conditions in order to probe various parameters essential for the development of a physics-based Cheetah reactive flow hotspot model. In situ pressure gauges provide insight into the degree of reaction in the explosive that are not obtainable with optical PDV measurements or distance measurements such as run to detonation. Double shock data was obtained to inform a Composition Aware Cheetah model which can be applied to any TATB-based IHEs. This model supports efforts to find a new IHE formulation and potentially incorporate new binders into IHE formulations. Simulations of each experiment are included to demonstrate the utility of these focused experiments to developing models of HE behavior. One-dimensional gas gun experiments are essential for characterizing shocked HE behavior and informing HE models.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Photo Doppler Velocimetry and Gamma/Neutron Yield Measurements of Godiva-IV Critical Assembly

The purpose of this experiment was to collect data for a dynamic benchmark of the Godiva-IV burst assembly. Data were taken using two different measurement systems. The gamma & neutron flux was measured using a calibrated, high-dynamic-range scintillator detector, the MHD-240. The measurement will be used to determine the total fission yield and alpha throughout the burst and shutdown sequence of Godiva-IV. The Photon Doppler Velocimetry (PDV) measurement detected the surface motion of the burst assembly as a function of time. The combined data will be used in a multi-physics simulation of the Godiva-IV burst assembly.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Revisiting the Kinematics of the Cylinder Test

The cylinder expansion experiment is a well-established performance test for condensed explosives that is utilized routinely to determine pressure-energy-volume relationships for detonation products. The modern cylinder test employs optical interferometric techniques to measure velocity, as opposed to older realizations where streak cameras were commonplace. Despite their widespread use, questions sometimes remain as to what kind of data the velocity diagnostics in a cylinder test provide along with how to interpret such measurements and relate them to physical quantities of interest. Here in this study, equations are derived that fully describe the kinematics of the cylinder wall during expansion. These equations are then applied to experimental as well as synthetic data generated via a hydrodynamic simulation in order to verify the mathematical framework developed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Response of PETN detonators to elevated temperatures

In the present study, commercially available detonators with pentaerythritol tetranitrate (PETN) were subjected to elevated temperatures. The detonators were thermally ignited over a range of heating rates to measure ignition delay time and assess detonator violence. The violence of the detonator was quantified by measuring the velocity of the detonator closure disc (or “flyer”). The maximum flyer velocity of a thermally ignited detonator was comparable in magnitude to that obtained by initiating a room temperature pristine detonator with an exploding bridge wire (under the same confinement); however, the high flyer velocity was not an indication of deflagration to detonation transition (DDT) in the thermally ignited detonator. The detonator responded more violently than a thermally ignited detonator when initiated at 95% of the ignition delay time. Furthermore, inoperability thresholds were also measured by varying the detonator temperature and the threshold was found to be sensitive at detonator temperatures below the melting point of PETN.

42 ENGINEERING↗
DOE OSTI2020

Spall and subsequent recompaction of copper under shock loading

Research was undertaken to study spall and subsequent recompaction of oxygen-free high-thermal-conductivity copper using a single-stage large-bore light gas gun capable of planar impacts. Gun experiments were conducted that produced an initial spall in the target with a subsequent recompaction of the spall damage/layer by the use of layered impactors. Symmetric spall experiments at similar conditions were also conducted as a control to the recompaction experiments. Photonic Doppler velocimetry was used to obtain the velocity history of the target’s back surface; these velocity histories were analyzed, and the results were compared to numerical simulations. After recovery of selected samples, the microstructure was analyzed using optical imaging microscopy and electron backscatter diffraction. Recompaction waves were clearly observed in the time-resolved data obtained at the back surface of the targets. Two different series of experiments were performed to understand the effect of damage morphology on the stress required for spall recompaction. In the initial series, the peak pressure of the first shock was systematically increased to alter the amount of damage in the material. While in the second series, the peak pressure of the second shock was increased, keeping the magnitude of the first shock relatively constant to understand the effect of peak stress on the recompaction process. Findings clearly show that recompaction results in a perturbed band of the microstructure at the location of the expected spall plane in all cases except where the peak stress of the second shock is lower than the critical value.

, recompaction↗
DOE OSTI2022

LANL FY21 NCSP Highlights [Slides]

This presentation highlights the activities of Los Alamos National Laboratory (LANL) in fiscal year 2021.These include the celebration of the tenth anniversary of NCERC operations, a large experiment campaign (IER 488 - MUSiC: Measurements of Uranium Subcritical and Critical), preparation for FY22 experiments, the completion of several ongoing experiments, and a control system upgrade project.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Dynamic Properties of FeCrMnNi, a High Entropy Alloy

High entropy alloys (HEAs) represent a new class of materials that potentially possess an ideal combination of high strength and ductility and may be candidate materials that can withstand high amounts of damage before failure, especially under extreme conditions. To this end, a series of shock/spall loading experiments were conducted on an Fe/Cr/Mn/Ni HEA to assess not only its equation of state (EOS) but also its resistance to damage and failure. A single-stage light gas gun was used to conduct a series of flyer plate symmetric impact experiments coupled with recovery of the samples for post-mortem microstructural analysis to obtain fundamental understanding regarding the damage morphology. Our results show that the measured EOS for this alloy was in reasonable agreement with an estimated Hugoniot value. Additionally, the spall strength of these alloys was found to vary between 1.4 and 1.9 GPa within the same plate but was comparable to other iron-based conventional alloys. DOE/NV/03624--1059

36 MATERIALS SCIENCE↗
DOE OSTI2022

Dominant wave analysis

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PDV, ejecta physics, signal analysis↗