Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PBX 9502”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

PBX 9502 Literature Review: An Engineering Perspective

Engineering analysis for the stockpile systems requires that materials used in the stockpile be characterized properly. One of these materials is PBX 9502, an insensitive high explosive (IHE). The Los Alamos National Laboratory (LANL) is working to improve its engineering material modeling capability for PBX 9502.This effort includes the development of requirements for an engineering material model (or models), review of material models currently used for engineering simulations, and review of currently available thermal-mechanical test data. The information obtained will either help to enhance the existing models or help the development and implementation of a new model or models. This document summarizes a review of literature on PBX 9502 that was performed over the past several months. The review was focused primarily on literature dealing with the characterization of PBX 9502 from a thermo-mechanical standpoint. Literature dealing with the formulation, explosive performance, and sensitivity was not included in this report. It should be noted that, like most research of this nature, this literature review is not intended to be all-inclusive. However, it provides a detailed baseline of the information that is available and will be very useful to those seeking to expand the PBX 9502 knowledge base.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2022

Fracture toughness and crack propagation in LX-17 and PBX 9502 insensitive high explosives

High explosive materials, and in particular insensitive high explosive (IHE) materials, are of significant interest. TATB-based LX-17 and PBX 9502 are two IHE’s and mechanical properties are an important metric of performance. In this work we present, for the first time, a study of fracture as a function of temperature and displacement rate and starter crack length on billet pressed IHE materials using a standard three point bend technique. We demonstrated that the technique can yield consistent results over time by measuring samples from the same lots 4 years later and observed that the fracture toughness of LX-17 and PBX 9502 are similar. We also determined the temperature dependence for different starter crack lengths and found that the fracture toughness generally decreases with larger starter crack sizes and temperatures. For the LX-17, where a wide temperature range of -60 C to 50 C was investigated, the impact of temperature on fracture toughness between -20 C and 23 C was less than expected. For the PBX 9502 we observed the difference in fracture toughness values between -20 C and 23 C did depend on the particular lot, and also there was a tendency of the fracture toughness to scale with the tensile strength. We also investigated the effect of a lower displacement rate and observed that while the impact on the fracture toughness was relatively small, the samples surprisingly did not break (fail) after exceeding the peak load. We took advantage of this to perform x-ray computed tomography (CT) of the samples to image crack propagation in the intact samples. We observed that cracks were generally straight and unaffected by the microstructure in the LX-17, in contrast to the PBX 9502 where the direction of the cracks would frequently change and were likely influenced by the underlying microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Temperature of shocked plastic bonded explosive PBX 9502 measured with spontaneous Stokes/anti-Stokes Raman

Raman spectra and velocimetry of shocked PBX 9502 (plastic bonded explosive composed of 95% triaminotrinitrobenzene (TATB) and 5% 3M Company Kel F-800 polymer binder) are reported with the Stokes/anti-Stokes ratio used to determine temperature after the shock reflects from a lithium fluoride window. Final pressures up to 14.5 GPa were tested, but the pressure induced absorption of TATB caused the Raman signal to decrease exponentially with pressure. The reflected shock temperature could be determined to 7 GPa, with an average increase of 14.9 K/GPa. Suggestions to adapt the technique to permit thermometry at higher temperatures are discussed, as are comparisons to a recently proposed equation of state for PBX 9502.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

PBX 9502 Gas Generation Progress Report FY17

The self-ignition (“cookoff”) behavior of PBX 9502 depends on the dynamic evolution of gas permeability and physical damage in the material. The time-resolved measurement of product gas generation yields insight regarding the crucial properties that dominate cookoff behavior. We report on small-scale laboratory testing performed in FY17, in which small unconfined samples of PBX 9502 were heated in a small custom-built sealed pressure vessel to self-ignition. We recorded time-lapse video of the evolving physical changes in the sample, quasi-static long-duration pressure rise, then high-speed video and dynamic pressure rise of the cookoff event. We report the full pressure attained during the cookoff of a 1.02g sample in a free volume of 62.5 cm 3 .

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2014

PBX 9502 Multimode Damage Accumulation Cycles-to-Failure Study

In FY13, we performed a detailed cycles-to-failure study of PBX 9502 using 3- point bend specimens. In that study we examined the effect of temperature and cyclic frequency on the failure behavior of PBX 9502. We identified cycles-to-failure curves for samples tested at -20°C, ~19°C and 50°C and at cyclic frequencies of 0.0001 up to 1-Hz. We also did cyclic conditioning of parts in an effort to establish damage accumulation criteria that could then be used in predictive models. As follow-on to that work, in FY14 we have added multimode cycles-to-failure to our test suite. Work this year re-established the baseline cycles-to-failure behavior of the PBX 9502 material tested round ~19°C at 1-Hz and also looked at damage accumulation under a multimode loading environment. This fresh baseline development was performed to remove any time related or test rig related variables. The multimode loading was done because real-world applications are not mono-modal and we desire for our predictive capability to be robust and include more complex, realistic scenarios. In the following sections we briefly describe the test setup, we provide a summary of the new baseline results and we show the multimode cycles-to-failure data and how it compares to the mono-modal test data.

42 ENGINEERING↗
DOE OSTI2022

An Investigation into the Surface Skidding Response of PBX 9501 and PBX 9502

While polymer-bonded explosives, PBX, have reduced sensitivity to ignition from mechanical shock or heating compared to conventional explosives, the investigation of the mechanical ignition mechanisms for PBX remains vital to assessing the safety during machining and general handling. Under frictional heating, hot spot generation due to high melting point contaminants in the interface is a suspected source for increased probability of detonation. Here, to investigate such frictional heating, samples of PBX 9501 and PBX 9502 were impacted and skidded against a tangentially moving target and thermally imaged. Temporally resolved temperature and forces were simultaneously measured with and without 300 µm silica grit at the frictional interface. A trend of increasing temperature was observed as the speed and tangential force on the sample increased. Grit particles in the frictional interface were found to act as frictional heat concentration spots owing to the grit's protrusion from the surface and lesser susceptibility to melting compared to the PBX. The coefficient of friction between PBX 9501 and the skidding surface was observed to be largely constant for forces and speeds at the lower end of the test range. In contrast, at high tangential speeds, the coefficient was found to be significantly lower.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermal Expansion of PBX 9502

Shock-to-detonation transition experiments for PBX 9502 cover a wide range of temperatures from -196 C to 250 C. The initial density is typically determined from the measured density at room temperature and the coefficient of thermal expansion. Here we combine the fits for the volumetric coefficient of thermal expansion by Skidmore et al. [2003] and for the density by Cady [see Dallman and Wackerle, 1993, fig. 2] to cover the full temperature range of the shock initiation experiments.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

TATB ratchet growth and hydrostatically-confined PBX 9502

The explosive TATB (1,3,5-triamino-2,4,6-trinitirobenzene) is formulated with various polymeric binders to create plastic-bonded explosives like PBX 9502 (95 wt% TATB and 5 wt% Kel-F binder). TATB crystals are graphitic and plate-like in nature and single crystals exhibit anisotropic thermal expansion where the direction normal to the platelet surface grows 10-20 times more than the in-plane platelet direction. Compactions of TATB, with and without binder, exhibit irreversible volume expansion, also known as ratchet growth, when thermal cycled to hot or cold temperatures. Specifically, when TATB-based compactions return to ambient after a temperature excursion away from room temperature, the volume of the specimen is slightly larger. Repeated thermal cycles can reduce the density by 1 to 2%. Axial confinement on a cylindrical specimen has previously been shown by us to suppress growth in the confining direction but then increase growth in the unconfined directions (likely due to creep effects). In the work presented here, PBX 9502 specimens were placed in cup assemblies where they were embedded in Sylgard (an incompressible silicon resin) to provide hydrostatic confinement when the assemblies were placed under different axial loads. The loaded cup assemblies were thermally cycled 10 times to hot and cold temperatures. Finally, results show that increasing the hydrostatic confining pressure causes a decrease in the PBX 9502 volume expansion that occurs.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

FY18 J23X PSDT Final Report: Shock Initiation of PBX 9502 Lot HOL88H891-008

This report details a series of plate impact experiments on the insensitive explosive PBX 9502 (95% TATB, 5% Kel-F 800) with lot number HOL88H891-008. This is a ’virgin’ lot (no recycled material used), for which many detonation performance measurements are available; the addition of these 1-D shock initiation experiments will aid model calibration efforts for this material. Samples were machined from isostatically-pressed billets with anominal density of 1.89 g/cc. The evolution of the shock to a detonation was characterized by 9 embedded magnetic particle velocity gauges, and 116 embedded magnetic time of arrival gauges (AKA shock trackers). Pho-ton Doppler velocimetry (PDV) with a LiF window was used at the back surface of the samples to capture the wave profile exiting the sample. Six experiments were performed, covering a pressure range of 10.8–18.6 GPa and run distances to detonation of 2.7–12.2+ mm. The shock initiation of this lot is found to be consistent with Pop plots reported for other lots of PBX 9502. All data have been uploaded to the LANL Small Scale Database for use by the research community.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

Preferred Void Orientation in Uniaxially Pressed PBX 9502

Ultra- and small-angle neutron scattering techniques were used to study the morphology of voids in directions parallel and perpendicular to the compaction plane of a uniaxially pressed cylinder of PBX 9502. Two-dimensional scattering patterns from samples cut parallel to the compaction plane had circular equal-intensity contours, implying that along this view the voids are circular or randomly oriented. Identical measurements of samples cut perpendicular to the compaction plane produced elliptical equal-intensity contours, indicating preferred orientation of voids. Analysis of the two dimensional scattering patterns confirmed that the voids are non-spherical with an average aspect ratio of 1.20, flattened so that the larger dimensions of the voids lie within the compaction plane. Model analysis of the combined ultra- and small-angle neutron scattering curves revealed that the PBX 9502 porosity is interconnected, in the form of aggregates comprised of non-spherical, primary voids. The volume dimension was found to be the same in both directions, indicating that the aggregate is randomly oriented throughout the sample, and that it is the primary voids that are preferentially oriented. Furthermore, void interfaces with the surrounding matrix were found to be rough or polydisperse, with a common roughness dimension or polydispersity in all directions.

42 ENGINEERING↗
DOE OSTI2019

Thermal Cycling and Ratchet Growth of TATB and PBX 9502

The irreversible volume expansion, or ratchet growth, of TATB and PBX 9502 (95 weight% TATB) compactions has been quantified over a wide range of thermal cycles. While the precise TATB texture distributions of these specimen sets are likely different from each other, we believe they are consistent within each set, as the expansion data show reproducibility and consistency. These data provide a baseline characterization of the ratchet growth phenomenon in these materials. The increased expansion that comes with changes in the temperature range of the cycles is quantified, repeated hot cycles growing far more than cold. For thermal cycles above ambient where the temperature range is increased in subsequent cycles, the growth of a given cycle is shown to be dictated by previously-established growth trajectories, and the specimen will grow according to the growth potential associated with the temperature range of the present cycle. Alternating hot-cold cycles greatly enhances the cold-cycle contributions as compared to the growth of cold cycles alone. These “rules” of ratchet growth are first established, then observed to hold true for more complex sequences of hot and cold cycles. Finally, a simple equation is used to parameterize the response of individual data sets.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2023

The reactive flow evolution of the polymer-bonded explosive PBX 9502: Experiments and model validation in extreme pressure regimes

The shock-to-detonation transition properties of the triaminotrinitrobenzene based PBX 9502 high explosive (HE) are experimentally and computationally explored in extremely high input pressure conditions. These include both slightly sub-Chapman–Jouguet and overdriven input pressure conditions, namely, ∼25 and ∼31 GPa, respectively. Our experiments capture the transient buildup of a shock-induced reaction via measurement of HE and polymethyl methacrylate window interface particle velocity profiles for a variety of sample thicknesses for this insensitive HE. These observations necessitate extremely thin explosive samples, and the high rates of reaction provide a considerable challenge to optical diagnostics. Samples at these thicknesses also provide an opportunity for evaluation of potential micro-structure effects on the resulting shock-to-detonation-transition measurements. To address this, the thin samples are also characterized via x-ray micro-computed tomography. Finally, a pair of previously established continuum-level detonation performance modeling approaches for PBX 9502 were used to analyze the experiments. The employed model variants crucially differ in their definition of each model’s empirical reaction rate functional form, utilization of shock state quantities, and local flow variable dependencies. As a result, the present experiments provide a novel platform to evaluate the quantitative and qualitative consequences stemming from these modeling choices in a challenging initiation scenario, largely beyond the chosen calibration range of either model. This new experimental information will provide a platform for both improved physics and model parameterizations for this well-studied explosive.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Thermal Expansion of LX-17, PBX 9502 and Ultrafine TATB

A large quantity of linear strain and LCTE data from -55°C to 75°C on LX-17, PBX 9502 and ultrafine TATB (ufTATB) is presented. Axial and diametral measurements are blended to give final densities, which agree with the liquid immersion values of Baytos, et. al. The nominal densities at 21, -55 and 75°C in g cm -3 are: LX-17 1.90, 1.920, 1.874; PBX 9502 1.89, 1.907, 1.867; ufTATB 1.80, 1.822, 1.778. Data taken radially show more thermal expansion than that taken transversely in cut-up parts; both must be combined to get the density. There is no difference between virgin and recycled TATB. Rachet growth data is presented, both at low pressure and at higher pressure, where the swelling is diminished. A Kel-F strain curve is presented and the theoretical maximum densities are computed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Anisotropy in the Ratchet Growth of PBX 9502

TATB-based compactions and composites are known to undergo “ratchet growth”, an irreversible volume increase that occurs upon heating or cooling of a specimen. Ratchet growth likely arises because the coefficient of thermal expansion of the TATB crystals is strongly anisotropic, but the exact mechanism is not well-understood. TATB crystals in solid, plastic-bonded, explosive PBX 9502 parts can have a preferred crystallographic orientation (texture) caused by the compaction process. As a result, the irreversible strain associated with PBX 9502 ratchet growth is anisotropic. The present paper relates the magnitude of ratchet growth to the crystalline anisotropy of the TATB crystals. The crystalline anisotropy is measured by x-ray diffraction and the ratchet growth is measured by a digital image-correlation technique.

36 MATERIALS SCIENCE↗
DOE OSTI2017

SURFplus Model Calibration for PBX 9502

The SURFplus reactive burn model is calibrated for the TATB based explosive PBX 9502 at three initial temperatures; hot (75 C), ambient (23 C) and cold (-55 C). The CJ state depends on the initial temperature due to the variation in the initial density and initial specific energy of the PBX reactants. For the reactants, a porosity model for full density TATB is used. This allows the initial PBX density to be set to its measured value even though the coeffcient of thermal expansion for the TATB and the PBX differ. The PBX products EOS is taken as independent of the initial PBX state. The initial temperature also affects the sensitivity to shock initiation. The model rate parameters are calibrated to Pop plot data, the failure diameter, the limiting detonation speed just above the failure diameters, and curvature effect data for small curvature.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2015

PBX 9502 Stockpile-Returned Hemi Tension Directionality Study

This work is a continuation of work started in FY12 to evaluate whether the coring direction in PBX 9502 main charges affects the mechanical properties data. In FY13 we performed the compression and thermal expansion portions of the testing.1 In FY14 we have performed the quasi-static tension and compressive creep parts of the study. This paper focuses on the tensile results while a companion paper details the compressive creep results.2 In an effort to obtain mechanical properties samples that would better characterize the density distribution within a main charge and, to a lesser extent, to more thoroughly describe the mechanical behavior of material that has been in the field for long period of time, the LLNL PBX 9502 Core Surveillance coring pattern had been changed between cycles 29 and 30. Where the orientation of the tensile and compression samples tested in surveillance prior to cycle 30 had been cored in the tangential direction, the new coring diagram has both the tension and compression samples being oriented in the hoop direction. Prior to this study, the authors were not aware of any work that systematically demonstrated the effect on tensile properties of samples cored in these distinct directions. The results from this study will inform us of if and how we should trend the data taken before and after the coring pattern change.

42 ENGINEERING↗
DOE OSTI2019

PBX 9502 Gas-Generation Throughout Long-Duration Thermal Exposure and Cookoff

When energetic materials are subjected to thermal insult, an event may follow in which the explosive exothermically reacts in an undesirable fashion. This event is known as cookoff, or self-ignition, and understanding how different explosives behave during this event is critical for explosives safety. To further our understanding of how PBX 9502 (95% TATB, 5% Kel-F 800) behaves at cookoff, small scale laboratory experiments were conducted to study the pressure rise created by unconfined samples as they were heated to self-ignition. Collected data included high speed video of deflagration, sample temperature, a time-lapse of thermal damage and expansion, quasi-static pressure during heating, and the dynamic pressure during cookoff. These data provide evidence that this composition remains impermeable through thermal evolution, until internal void pressure overcomes the mechanical strength of the material and drives macro-scale cracking. Previous work reported that PBX 9502 exhibits a pressure-dependent cookoff behavior [1], the cause of which is not entirely understood. The results reported here contribute to an understanding of the underlying behavior which gives rise to the observed pressure dependence.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Multiscale numerical investigation of ratchet growth damage effects in PBX 9502

This paper presents results of numerical experiments conducted on the high explosive PBX 9502 to investigate how recently observed grain-scale damage mechanisms of ratchet growth affect uniaxial compression measurements. Simulations are multiscale in the sense of directly resolving grains, pores, cracks, and grain-interfaces based upon scanning electron microscope (SEM) images of damaged and undamaged samples. The combined finite-discrete element method (FDEM) is utilized to resolve both grain-scale microfracture and elastoplastic deformation of solid grains. Pristine (undamaged) and damaged microstructures are compared in simulation of unconfined compression tests of the same material from the literature. Here, the simulation results show the observed microscale mechanisms of damage, specifically microfracture predominantly around and sometimes through grains and crack-associated pore growth, can well-explain the effective degradation of strength and stiffness observed in the laboratory measurements.

36 MATERIALS SCIENCE↗