Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session E2: ERM: Thermal response, cook-off, and aging |
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Chair: Mark Mason, NAWSWD Room: Grand Ballroom II |
Monday, June 17, 2019 3:30PM - 3:45PM |
E2.00001: Prediction of Thermal Decomposition Temperatures Using Statistical Methods Ariana Beste, Brian Barnes We present development of a computational tool for the prediction of thermal decomposition onset temperatures using machine learning techniques. Our focus is on energetic materials, for which such a tool currently does not exist. Our models are trained and tested on published differential scanning calorimetry data consisting of decomposition temperatures and molecular formulas. Therefore, the models do not require any quantum mechanical calculations and may easily be transitioned to an experimentalist. We explore a variety of molecular fingerprints for encoding chemical information, and contrast their performance. We expect a complex, nonlinear relationship between molecular fingerprint and decomposition temperature and, therefore, test nonlinear methods such as Gaussian process regression, kernel ridge regression, and random forest regression, adaptive boosting of decision trees, and neural networks. We discuss the effect of outliers with particularly high or low decomposition temperatures on model performance. Due to the high dimensionality of the employed fingerprints, we analyze the utility of input reduction methods such as principal component analysis prior to model optimization. Further, we investigate the influence of specific functional groups on prediction quality. [Preview Abstract] |
Monday, June 17, 2019 3:45PM - 4:00PM |
E2.00002: Measurements of shock sensitivity in a damaged explosive using a small-scale gap test Nick Cummock, Alex Casey, Gabriel Montoya, Chris Molek, Chad Rumchik, Steven Son The shock sensitivity of an explosive is often given in terms of the input pressure versus the corresponding run-distance to complete detonation. Plotted in log-log space, these are known as Pop-plots. In this work, small cylindrical samples of less than 0.5 g of explosive are used in a small-scale gap test to determine the run-distance as a function of pressure in PBX 9501 at varying initial densities, which are compared to thermally damaged samples. In this set of experiments, the L50, or pressure input at which 50\% of the samples will initiate is determined for pellets of length equal to 6 mm and 3 mm, where the pellet length is taken as the run distance for the L50 pressure. Differences in shock sensitivity as shown by Pop-plots are shown. Further work involving isolation of the mechanisms influencing the change in shock sensitivity, such as porosity shifts, changes in particle size, and solid phase changes is considered. [Preview Abstract] |
Monday, June 17, 2019 4:00PM - 4:15PM |
E2.00003: Characterization of Solid Residue Formation in LX-17 Abnormal Thermal Environments John Reynolds, Evan Kahl, Nick Muetterties, A. J. Nelson, Harris Mason, Jonathan Crowhurst LX-17 (98 {\%} TMD) was thermally treated in the small-scale vessel cook-off reactor to understand the response to abnormal thermal environments. The cylindrical sample with 14{\%} void-space, was sealed in the reactor at room pressure heated at 0.1 \textdegree C/min heating rate until explosion at 3000 psi due to decomposition gas pressure. The LX-17 was consumed leaving a minimal amount of yellow-black-brown residue in the vessel. Standard DSC of the residue showed a shift in the decomposition temperature range (40 \textdegree C) and a reduction in the amount of heat flow (approx.$_{\mathrm{\thinspace }}$ 90{\%}) compared to LX-17. The DSC-TGA showed the residual material still produced exothermic heat flow after 425 \textdegree C with T$_{\mathrm{max}} \quad =$ 756 \textdegree C. IR of the residue exhibited evidence of C-N but little evidence of TATB, indicating the residue was significantly reacted. XPS showed the primary species are C {\&} N at a ratio of about 1 (atomic basis) and to a lesser extent, O. Detailed analysis of the C 1s, N 1s, and O 1s spectra indicated C-C, C-N, N-H, N-C, O$^{\mathrm{=}}$, OH, and H$_{\mathrm{2}}$O in the residue. Solid state $^{\mathrm{13}}$C and $^{\mathrm{1}}$H NMR corroborated the C-C, C-N and N-H structures and identified some sp$^{\mathrm{3}}$ carbon. The properties of this residue will be compared to residues produced under other thermal cook-off conditions. [Preview Abstract] |
Monday, June 17, 2019 4:15PM - 4:30PM |
E2.00004: Understanding the hygrothermal aging effects and lifetime prediction on a NASA standard initiator Juyoung Oh, Jack Yoh The NASA standard initiator utilized in airbags of automobiles or as pyrotechnics in launch vehicles such as rockets and missiles contributes to assuring ignition of the more-difficult-to ignite substances in the system. The designed performance, however, has shown to degrade due to oxidization of metal powder fuel, changes in material properties, and premature reactions in their chemical constituents, all of which contribute to so-called aging process. Earlier studies have focused on the analysis of aging mechanism of the accelerated aging samples at ad-hoc thermal conditions. However, moisture is believed to play an impacting role, and such the role of relative humidity (RH) must be understood as the samples are exposed to the environment of seasonal changes during manufacturing and storage. The current study is motivated to provide the useful insight into understanding the hygrothermal aging of the zirconium potassium perchlorate (ZPP), better known as a NASA standard initiator. The lifetime of ZPP, heated at 71 C and exposed to four different RH conditions (0, 30, 70, and 100\%), is predicted. The combustion process and changes in thermodynamic properties were analysed by utilizing the thermograms of Differential Scanning Calorimetry. [Preview Abstract] |
Monday, June 17, 2019 4:30PM - 5:00PM |
E2.00005: Synthesizing nitrogen-rich compounds and investigating their as ingredients of novel composite propellants Invited Speaker: Mateusz Szala High-nitrogen azotetrazole salts were synthesized, characterized and used as nitrogen-rich compounds for the preparation of novel composite propellants. Triaminoguanidinium and guanidinium azotetrazolate (TAGAZ, GUAZ) were selected based on the results of thermic and sensitivity measurements. Nitrocellulose was used as a traditional ingredient of propellants, while dibutyl phthalate and 3-methyl-3-nitroxymethyloxetane (NIMMO) was used as a plasticizer. The ingredients and resulting propellants were tested using differential thermal analysis coupled with a thermogravimetric method. Standard pyrostatic tests in a closed chamber were also conducted and characteristic ballistic parameters were calculated. Both of the high-nitrogen compounds that were tested could be potential ingredients of future propellants. The pressure rise rate for the tested propellants is simply correlated with TAGAZ/GUAZ content. NIMMO is an interesting new plasticizer for nitrocellulose, although it exhibit relatively high volatility during DTA-TG tests which limits its utility. Topic 2.01. \\ \\In collaboration with: Leszek Szymanczyk, Zbigniew Surma, Marcin Hara, Military University of Technology [Preview Abstract] |
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