Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session E01: Cylinder Tests and ModelingRecordings Available
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Chair: Trevor Willey, Lawrence Livermore Natl Laboratory Room: Anaheim Marriott Platinum 5 |
Monday, July 11, 2022 2:00PM - 2:15PM |
E01.00001: Cylinder Expansion (CYLEX) Test Simulations Gerrit T Sutherland The Cylinder Expansion Test (CYLEX) measures the velocity of a copper cylinder which contains a detonated explosive. Variations in the CYLEX test method include: cylinder (tube) length/diameter (l/d) ratio, supporting methods for the tube ends, explosive booster strength, and placement locations for the photonic Doppler velocimetry (PDV) probes. CTH hydrocode simulations were performed to determine the effect of tube (l/d) ratio on wall velocity histories at differing probe locations, effect of booster strength, effect of fixed versus free supporting methods, and estimation of pressure-temperature states in the detonation product gas near the PDV measurement point. Simulation results showed the following. First, a (l/d) ratio of 12 was sufficient to allow the velocity histories to be measured by multiple PDV probes. Second, booster strength did not affect velocity histories for Composition B explosive. Third, the tube confinement method did not affect the velocity histories. Finally, the time period at which the detonation product gas was at a high temperature or pressure was small compared to the time required for the products to reach a relative volume expansion of 7. This expansion corresponds to a one-inch CYLEX expansion of ≈19-mm. |
Monday, July 11, 2022 2:15PM - 2:30PM |
E01.00002: Effect of Initial Temperature on the Detonation Performance of the TATB-Based Explosive PBX 9502 Eric K Anderson, Mark Short, Stephen J Voelkel, Carlos Chiquete, Scott I Jackson When heated, common high explosives expand and decrease in density, with possible implications for the detonation timing and acceleration of confining materials. Here, we report on the effect of elevated initial temperatures on detonation performance as measured in a series of new and previously reported rate-stick and cylinder expansion (CYLEX) test experiments for the 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) based insensitive high explosive PBX 9502. Specifically, PBX 9502 rate stick and CYLEX tests at both ambient (25 °C) and elevated (75 °C) initial temperatures are examined. Detonation velocities, front shapes, and confiner motion are compared. At 75 °C, the density of PBX 9502 is in the range of 1.860-1.870 g/cc as compared to 1.885-1.895 g/cc, which, in the absence of other effects, would tend to decrease detonation velocity and product energy. However, we find that except for very large charges, the performance of the thermally elevated PBX 9502 charges is very similar to that of the higher density ambient charges. Furthermore, the 75 °C PBX 9502 outperforms low density ambient PBX 9502, despite having an even lower density when heated. We show that this higher-than-expected performance of low-density heated explosive is not solely attributable to the increase in charge diameter as it is heated, and the detonation front shapes suggest that faster reaction kinetics of the elevated temperature explosive plays an important role. |
Monday, July 11, 2022 2:30PM - 2:45PM |
E01.00003: PETN Rate Stick and Cylinder Expansion Test Assemblies at the 3 mm Scale Ritchie I Chicas, Eric K Anderson, Carlos Chiquete, Scott I Jackson The explosive pentaerythritol tetranitrate (PETN) is commonly used for detonators, detonating fuses, and booster assemblies. It has a spatially small reaction zone (measured in microns) that is advantageous for these applications and supports detonation function at very small scales. However, the small reaction zone and scale of typical applications requires performance testing at small scales to generate data for model calibration. Here we discuss the construction and fielding of 3-mm-diameter rate sticks and cylinder expansion (CYLEX) tests for PETN with a density of 1.65 g/cc. These small tests utilized similar assembly and diagnostic techniques as the larger versions typically fielded for other explosives except in the details of how they were implemented. Specifically, the rate sticks were constructed from 3 mm pellets bonded together in a precision fixture, and utilized ionization wires or a streak camera measurement to record the detonation velocity. A mirror destruct technique was also utilized to measure the front curvature (the first such measurements for the explosive). For the CYLEX test, the standard confiner dimensions (which are designed for a 25.4 mm charge diameter) were scaled to the 3 mm charge diameter, and rather than using shorting wires to measure detonation velocity, PDV was used to measure both detonation velocity and confiner motion. To manufacture the confiner, a combination of electron discharge machining (EDM) and conventional machining was used. In spite of the small scale of these tests and diagnostic differences, all tests yielded full data return. Most notably, given the thin wall of the CYLEX test (0.3 mm), wall expansion records did not exhibit any sign of early wall failure. The corresponding products equation of state model reduction is found to scale consistently with prior PETN results at other densities and test spatial scales. |
Monday, July 11, 2022 2:45PM - 3:00PM |
E01.00004: Observations on aluminum reactions in the cylinder test using low-temperature insensitive explosive formulations Bryce C Tappan, Joseph P Lichthardt, Larry G Hill, Amanda L Duque, Patrick Bowden, Von Whitley The reaction of particulate aluminum metal in detonation products is a complex, multivariable process involving the chemistry of the parent explosive and binder system as well as the particle size and amount of aluminum in the formulation. This chemistry dictates both the availability of oxidizing species available for aluminum combustion as well as reaction zone temperature and length and the conditions in the following flow. Most formulations investigated that are designed to burn aluminum very quickly to provide enhanced metal-pushing ability, sometimes called combined effects explosives, are usually formulated with high-power nitramines such as RDX, HMX and CL-20, but little investigation has been performed on lower-energy insensitive formulations. To this end, formulations have been produced using TATB, DAAF and NTO as the principle crystalline explosive ingredient. In CYLEX testing, TATB formulated with Al and the binder KelF-800 (PBX 9502-Al), showed no indication of aluminum reaction when H-2 aluminum (~3.5 µm diameter) was used. However, interestingly, when 80 nm aluminum was used, roughly 25-50% aluminum participation was observed via cylinder wall velocity records, which is a distinct divergence from aluminum particle size effects observed in nitramine formulations. Formulations with isotopically substituted TATB-d6 were also evaluated, however failed to detonate in the same CYLEX configuration, indicating a relationship in the kinetic isotope effect in failure diameter in addition to the previously observed decrease in detonation velocity. As a comparison to the TATB formulations DAAF and NTO were selected as additional insensitive explosive ingredients of study with either similar calculated detonation temperatures or oxygen balance (O.B.); TATB = 2483. 9 K, O.B. -55.8, DAAF; 3055.9 K O.B. = -52.8%, NTO; 2319.1 K, O.B. = -24.6%. |
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