Deanne Idar | Lewis University (original) (raw)
Papers by Deanne Idar
The initiation criterion for nitromethane and diethylenetriamine- sensitized solutions has been e... more The initiation criterion for nitromethane and diethylenetriamine- sensitized solutions has been established over a confined range of jet diameters, velocities, and failure diameters. The data were normalized with the failure diameter that was chemically modified, and they support the hypothesis that the failure diameter should be made part of the critical initiation function. The difference between physically- and chemically sensitized NM in promptness of initiation, as measured by corner turning distance, was not statistically significant. The diameter of the Viper jet has been characterized over a wide range of velocities.
Propellants, Explosives, Pyrotechnics, 1999
ABSTRACT An extensive study of the initiation of nitromethane by shaped-charge jets has been cond... more ABSTRACT An extensive study of the initiation of nitromethane by shaped-charge jets has been conducted and is reported in the paper following this one. In order to accomplish this a great deal of background information and description of the effect of temperature on failure diameter, measurement of jet diameters, material properties and experimental configuration is necessary. The collection of these data is of general interest to the field of energetic materials research, and is presented here as a separate paper.Verbesserte Charakterisierung der Eigenschaften von Nitromethan, Nitromethan-Mischungen und dem Hohlladungsstachel Eine ausführliche Studie über die Initiierung von Nitromethan durch Hohlladungsstachel ist durchgeführt worden und wird in der nachfolgenden Arbeit beschrieben. Um diese zu vervollständigen ist eine groüe Menge an Hintergrundinformation, die Beschreibung der Wirkung der Temperatur auf den Versagensdurchmesser, die Messung des Stacheldurchmessers, die Materialeigenschaften und der experimentelle Aufbau notwendig. Die Sammlung dieser Daten ist von groüem Interesse für die Forschung auf dem Gebiet der energetischen Materialien und wird in dieser separaten Arbeit vorgestellt.Caractérisation améliorée des propriétés du nitrométhane, de mélanges nitrométhane et du jet de charge creuseOn a effectué une étude détaillée sur l'initiation du nitométhane par un jet de charge creuse, que l'on décrit dans une étude faisant suite à la présente étude. Pour pouvoir compléter cette étude, on a besoin d'une grande quantité d'informations de fond, de la description de l'effet de la température sur le diamètre raté, de la mesure du diamètre de jet, des propriétés du matériau et du montage expérimental. La compilation de ces données présente un grand intérêt pour la recherche dans le domaine des matériaux énergétiques et est présentée dans cette étude séparée.
Compression measurements were conducted on plastic-bonded explosive PBX 9502 and its binder, Kel-... more Compression measurements were conducted on plastic-bonded explosive PBX 9502 and its binder, Kel-F 800™, as a function of temperature from -55 °C to +55 °C using an improved split Hopkinson pressure bar at high strain rates (~1400 s-1) and at low strain rates (~0.001 to 0.1 s-1) at ambient temperatures. PBX 9502 exhibits lower dynamic compressive strength, but is much less sensitive to strain rate and temperature, than PBX 9501. In contrast, the mechanical response of the Kel-F 800™ binder is stronger than pure (or plasticized) Estane™, but is again less strain rate and temperature dependent. The effects of longitudinal and transverse loading orientations (due to preferred orientation of TATB) and virgin versus recycled TATB on the properties of PBX 9502 are presented. .
The effect of sample thickness, strain rate, and temperature on the mechanical response of Adipre... more The effect of sample thickness, strain rate, and temperature on the mechanical response of Adiprene-LlOO is presented. The compressive stress-strain response of Adiprene-L100 was found to depend on both the applied strain rate; 0.001 I E
Polymer Engineering and Science, 2006
Compression measurements were conducted on three explosive formulation binders, extruded Estane, ... more Compression measurements were conducted on three explosive formulation binders, extruded Estane, plasticized Estane, and plasticized hydroxyl-terminated polybutadiene, as a function of temperature and strain rate. The mechanical response of the Estane was found to exhibit the strongest dependency on strain rate and temperature and higher flow strength for similar test conditions of the three materials tested. Plasticized Estane was less sensitively dependent on strain rate and temperature, followed by the plasticized HTPB. The visco-elastic recovery of all three binders is seen to dominate the mechanical behavior at temperatures above the glass transition temperature (Tg). There is a pronounced shift in the apparent Tg to higher temperatures as the strain rate is increased. Two distinct behaviors are observed in the binders below the Tg. At low strain rates, the binders exhibit a yield behavior, followed by a drop in the flow stress, which may or may not recover. At high strain rates, the load drop does not occur and the flow stresses either gradually increase, as in plasticized HTPB, or it levels out as seen in the Estane-based binders. POLYM. ENG. SCI., 46:812–819, 2006. © 2006 Society of Plastics Engineers
High-strain-rate (2000 s-1) compression measurements utilizing a specially-designed Split-Hopkins... more High-strain-rate (2000 s-1) compression measurements utilizing a specially-designed Split-Hopkinson-Pressure Bar have been obtained as a function of temperature from -55 to +50 °C for the plastic-bonded explosive PBX 9501. The PBX 9501 high-strain-rate data was found to exhibit similarities to other energetic, propellant, and polymer-composite materials as a function of strain rate and temperature. The high-rate response of the energetic was found to exhibit increased ultimate compressive fracture strength and elastic loading modulus with decreasing temperature. PBX 9501 exhibited nearly invariant fracture strains of ~1.5 percent as a function of temperature at high-strain rate. The maximum compressive strength of PBX 9501 was measured to increase from ~55 MPa at 50 °C to 150 MPa at -55 °C. Scanning electron microscopic observations of the fracture mode of PBX 9501 deformed at high-strain revealed predominantly transgranular cleavage fracture of the HMX crystals.
Accurate temperature measurements in dynamic systems have been pursued for decades and have usual... more Accurate temperature measurements in dynamic systems have been pursued for decades and have usually relied on optical techniques. These approaches are generally hampered by insufficient information regarding the emissivity of the system under study. We are developing NRS techniques to measure temperature in dynamic systems and overcome these limitations. Many neutron resonances have narrow intrinsic Breit-Wigner widths such that the resonance is substantially broadened by the atomic motion even at room temperature. Thus, accurate measurement of the Doppler contribution allows one to infer the material temperature, and for the conditions achieved using standard high explosives, the probe itself is not perturbed by the high temperature and pressure. Experiments are conducted using a pulsed spallation source at LANSCE with time-of-flight measurement of the neutron spectra. In initial experiments, we have demonstrated that measurements with ten percent accuracy are possible. We have fielded dynamic tests, most of which were neutron-flux limited. An overview of the approach and the status of our experimental campaign are discussed.
Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable... more Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.
Thermochimica Acta, 2002
Impact or thermal ignition of high explosives (HE) results in deformation that can lead to damage... more Impact or thermal ignition of high explosives (HE) results in deformation that can lead to damage. Fractures or defects, combined with sufficient pressure, dramatically increase the available surface area and potentially changes even the mode of combustion. Recent impact and cookoff experiments on PBX 9501, (HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, with a plasticized, Estane-based binder), have shown complex cracking patterns caused by impact or pressurization. Fast reactive waves have been observed to propagate through the cracks at hundreds of meters per second. We present experiments that examine the combustion of mechanically and thermally damaged samples of PBX 9501. Mechanically damaged samples, damaged by quasi-static compression, exhibit large, $200 mm stress fracture accompanied by extensive rubblization. Combustion experiments determine a 1:4 AE 0:6 MPa critical pressure for the onset of violent convective combustion, consistent with connected porosity of 25 mm. Thermally damaged samples, damaged by heating in a 180 8C oven for 30 min, exhibit 2-20 mm cracks distributed throughout the sample. Combustion experiments indicate a 9:2 AE 0:4 MPa critical pressure for the onset of violent convective combustion in the thermally damaged sample, consistent with connected porosity of 4 mm. Below the critical pressure, the burn rate and pressure exponent of thermally damaged PBX 9501 are close to those of the pristine material. #
Propellants Explosives Pyrotechnics, 1999
ABSTRACT The experimental hypervelocity jet initiation threshold criteria for neat nitromethane a... more ABSTRACT The experimental hypervelocity jet initiation threshold criteria for neat nitromethane and homogeneous- and heterogeneous-sensitized nitromethane mixtures have been determined over a range of failure diameters, jet velocities from 2–9 mm/μs, and jet diameters in two test configurations. These criteria were used to define detonation and failure conditions in nitromethane and the nitromethane mixtures as a function of contact- and bow-shock conditions. These data were compared with data reported by others in the literature on bare solid explosives. A favorable comparison of threshold values is achieved by normalization of the criteria with the failure diameters. The effect on the initiation of the confinement proximity to the jet axis was also investigated. Experimental results have shown that high impedance boundaries near the jet axis induced conditions that allowed initiation to occur at lower jet velocities than those determined by the criteria. Tests also were performed on both homogeneous and heterogeneous nitromethane mixtures, having the same failure diameters, to determine if the same or similar jet penetration distances were required for initiation. The results, within experimental error, do not show any definitive differences in initiation conditions between the two types of mixtures.Kriterien für den Initiierungsgrenzwert von Nitromethan und Nitromethanmischungen bei Übergeschwindigkeit des HohlladungsstachelsDie experimentellen Kriterien der Initiierungsgrenzwerte von reinem Nitromethan und homogenen und heterogenen sensibilisierten Nitromethanmischungen bei Hohllandungsstachel mit Übergeschwindigkeit wurden bestimmt in einem Bereich der Versagensdurchmesser (Stachelgeschwindigkeit 2–9 mm/μs) und der Stacheldurchmesser bei zwei Testkonfigurationen. Diese Kriterien wurden verwendet zur Definition der Detonations– und Versagensbedingungen bei Nitromethan und Nitromethanmischungen als Funktion von ebener und schräger Stoßeinwirkung. Diese Daten wurden verglichen mit Daten aus der Literatur an reinen festen Explosivstoffen. Ein brauchbarer Vergleich der Grenzwerte wird erreicht durch Anpassung der Kriterien an die Versagensdurchmesser. Die Wirkung der Initiierung auf die Verdämmung nahe der Stachelachse wurde ebenfalls untersucht. Die experimentellen Ergebnisse haben gezeigt, daß eine starke Grenzflächenkopplung nahe der Stachelachse Bedingungen erzeugt, die eine Initiierung bei niedrigeren Stachelgeschwindigkeiten erlauben als bei den durch die Kriterien bestimmten. Untersuchungen wurden auch durchgeführt sowohl an homogenen und heterogenen Nitromethanmischungen, mit denselben Versagensdurchmessern, um zu bestimmen, ob dieselben oder ähnliche Eindringtiefen des Stachels erforderlich waren für die Initiierung. Die Ergebnisse zeigen innerhalb der experimentellen Meßunsicherheit keine entscheidenden Unterschiede der Initiierungsbedingungen bei den beiden Mischungsarten.Critères pour le seuil d'initiation du nitrométhane et des mélanges nitrométhane avec jet de charge creuse hypervéloceLes critères expérimentaux des seuils d'initiation du nitrométhane pur et de mélanges nitrométhane sensibilisés homogènes et hétérogènes avec jet de charge creuse hypervéloce ont été déterminés pour un domaine de diamètres ratés (vitesse de jet 2 à 9 mm/μs) et des diamètres de jet dans deux configurations de test. Ces critères ont été utilisés en vue de la définition des conditions de détonation et de défaillance pour le nitrométhane et les mélanges nitrométhane en fonction d'un choc plan ou incliné. Ces données ont été comparées à des données provenant de la littérature sur les explosifs solides. Une comparison favorable des seuils peut être obtenue par adaptation des critères aux diamètres ratés. L'effet de l'initiation sur le confinement à proximité de l'axe du jet a également été étudié. Les résultats expérimentaux ont montré qu'un fort couplage de la surface limite à proximité de l'axe du jet créait des conditions permettant une initiation à des vitesses de jets plus faibles que celles déterminées par les critères. Des études ont également été effectuées tant sur des mélanges nitrométhane homogènes qu'hétérogènes, avec les mêmes diamètres ratés, en vue de déterminer si l'on avait besoin des mêmes profondeurs de pénétration de jets ou de profondeurs semblables pour l'initiation. En tenant compte de l'erreur expérimentale, les résultats ne montrent pas de différences significatives des conditions d'initiation entre les deux types de mélange.
Several microstructural mechanisms have been suggested for ignition in explosives subjected to im... more Several microstructural mechanisms have been suggested for ignition in explosives subjected to impact by low-velocity projectiles. The shear-impact experiment, previously employed by Asay, et al. to dynamically study strain behavior, is engaged in this study to damage samples of PBX 9501 at various densities. Impact is achieved by using a gas gun projectile to drive a plunger which is in contact with the explosive. Various plunger shapes are utilized to produce different levels of shear in the sample. The experiment is designed to create damage by producing displacement in only two dimensions. Post-test analysis involving microscopy of polished surfaces reveals insightful patterns in consolidation and cracking, shear band development, and HMX phase transformation associated with ignition and subsequent quenching. Analysis of the samples in cross-section suggests the degree to which the assumption of two-dimensionality is valid.
Thermochimica Acta, 2000
Various plastic bonded explosives (PBXs) contain about 5-wt% polymer, plasticizer, and stabilizer... more Various plastic bonded explosives (PBXs) contain about 5-wt% polymer, plasticizer, and stabilizer as binder. The glass-transition temperature (T g ) determines, in part, if the binder will reduce or increase the sensitivity of the PBX to impact. A soft binder reduces the impact sensitivity; however, too soft a binder compromises the mechanical strength below that desirable for dimensional stability. Glass transitions were measured by temperature modulated DSC for PBXs before and after pressing. Pressing temperature was 90°C. The T g of Estane, a polyester/polyurethane used in some PBX binders, was investigated. Only small changes were observed in the low temperature T g of the soft segments but larger changes were seen in the higher temperature transitions due to the relaxation of the hard segments. The T g of Kel F 800, a binder used in insensitive PBX 9502, was observed near ambient temperature. The PBX 9502 had a lower T g than the neat polymer. Mechanical strength will be measured for the samples.
ABSTRACT Predicting the degree of violence of high explosive (HE) reactions for a given event is ... more ABSTRACT Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.
Synchro-ballistic use of rotating-mirror streak cameras allows for detailed recording of high-spe... more Synchro-ballistic use of rotating-mirror streak cameras allows for detailed recording of high-speed events of known velocity and direction. After an introduction to the synchro-ballistic technique, this paper details two diverse applications of the technique as applied in the field of high-explosives research. In the first series of experiments detonation-front shape is recorded as the arriving detonation shock wave tilts an obliquely mounted mirror, causing reflected light to be deflected from the imaging lens. These tests were conducted for the purpose of calibrating and confirming the asymptotic detonation shock dynamics (DSD) theory of Bdzil and Stewart. The phase velocities of the events range from ten to thirty millimeters per microsecond. Optical magnification is set for optimal use of the film's spatial dimension and the phase velocity is adjusted to provide synchronization at the camera's maximum writing speed. Initial calibration of the technique is undertaken using a cylindrical HE geometry over a range of charge diameters and of sufficient length-to- diameter ratio to insure a stable detonation wave. The final experiment utilizes an arc-shaped explosive charge, resulting in an asymmetric denotation-front record. The second series of experiments consists of photographing a shaped-charge jet having a velocity range of two to nine millimeters per microsecond. To accommodate the range of velocities it is necessary to fire several tests, each synchronized to a different section of the jet. The experimental apparatus consists of a vacuum chamber to preclude atmospheric ablation of the jet tip with shocked-argon back lighting to produce a shadow-graph image.
ABSTRACT The Modified Steven test geometry has been used with several different target designs to... more ABSTRACT The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.
Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed ... more Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.
Low amplitude impact tests on pristine and damaged, `baseline' and `aged' PBX 9501 specimens were... more Low amplitude impact tests on pristine and damaged, `baseline' and `aged' PBX 9501 specimens were performed to determine the critical impact-velocity threshold for violent reactions. HE damage was achieved by a single impact ranging in velocity from 36.9 to 54.4 m/s. External blast gauge and ballistic pendulum data were used to evaluate reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. Test results show that the damaged threshold 1) is lower than the pristine threshold and 2) is invariant to PBX 9501 lot-to-lot and age variables. .
Low amplitude impact tests on pristine and damaged, ‘baseline’ and ‘aged’ PBX 9501 specimens were... more Low amplitude impact tests on pristine and damaged, ‘baseline’ and ‘aged’ PBX 9501 specimens were performed to determine the critical impact-velocity threshold for violent reactions. HE damage was achieved by a single impact ranging in velocity from 36.9 to 54.4 m/s. External blast gauge and ballistic pendulum data were used to evaluate reaction violence relative to a steady-state detonation. Strain
The initiation criterion for nitromethane and diethylenetriamine- sensitized solutions has been e... more The initiation criterion for nitromethane and diethylenetriamine- sensitized solutions has been established over a confined range of jet diameters, velocities, and failure diameters. The data were normalized with the failure diameter that was chemically modified, and they support the hypothesis that the failure diameter should be made part of the critical initiation function. The difference between physically- and chemically sensitized NM in promptness of initiation, as measured by corner turning distance, was not statistically significant. The diameter of the Viper jet has been characterized over a wide range of velocities.
Propellants, Explosives, Pyrotechnics, 1999
ABSTRACT An extensive study of the initiation of nitromethane by shaped-charge jets has been cond... more ABSTRACT An extensive study of the initiation of nitromethane by shaped-charge jets has been conducted and is reported in the paper following this one. In order to accomplish this a great deal of background information and description of the effect of temperature on failure diameter, measurement of jet diameters, material properties and experimental configuration is necessary. The collection of these data is of general interest to the field of energetic materials research, and is presented here as a separate paper.Verbesserte Charakterisierung der Eigenschaften von Nitromethan, Nitromethan-Mischungen und dem Hohlladungsstachel Eine ausführliche Studie über die Initiierung von Nitromethan durch Hohlladungsstachel ist durchgeführt worden und wird in der nachfolgenden Arbeit beschrieben. Um diese zu vervollständigen ist eine groüe Menge an Hintergrundinformation, die Beschreibung der Wirkung der Temperatur auf den Versagensdurchmesser, die Messung des Stacheldurchmessers, die Materialeigenschaften und der experimentelle Aufbau notwendig. Die Sammlung dieser Daten ist von groüem Interesse für die Forschung auf dem Gebiet der energetischen Materialien und wird in dieser separaten Arbeit vorgestellt.Caractérisation améliorée des propriétés du nitrométhane, de mélanges nitrométhane et du jet de charge creuseOn a effectué une étude détaillée sur l'initiation du nitométhane par un jet de charge creuse, que l'on décrit dans une étude faisant suite à la présente étude. Pour pouvoir compléter cette étude, on a besoin d'une grande quantité d'informations de fond, de la description de l'effet de la température sur le diamètre raté, de la mesure du diamètre de jet, des propriétés du matériau et du montage expérimental. La compilation de ces données présente un grand intérêt pour la recherche dans le domaine des matériaux énergétiques et est présentée dans cette étude séparée.
Compression measurements were conducted on plastic-bonded explosive PBX 9502 and its binder, Kel-... more Compression measurements were conducted on plastic-bonded explosive PBX 9502 and its binder, Kel-F 800™, as a function of temperature from -55 °C to +55 °C using an improved split Hopkinson pressure bar at high strain rates (~1400 s-1) and at low strain rates (~0.001 to 0.1 s-1) at ambient temperatures. PBX 9502 exhibits lower dynamic compressive strength, but is much less sensitive to strain rate and temperature, than PBX 9501. In contrast, the mechanical response of the Kel-F 800™ binder is stronger than pure (or plasticized) Estane™, but is again less strain rate and temperature dependent. The effects of longitudinal and transverse loading orientations (due to preferred orientation of TATB) and virgin versus recycled TATB on the properties of PBX 9502 are presented. .
The effect of sample thickness, strain rate, and temperature on the mechanical response of Adipre... more The effect of sample thickness, strain rate, and temperature on the mechanical response of Adiprene-LlOO is presented. The compressive stress-strain response of Adiprene-L100 was found to depend on both the applied strain rate; 0.001 I E
Polymer Engineering and Science, 2006
Compression measurements were conducted on three explosive formulation binders, extruded Estane, ... more Compression measurements were conducted on three explosive formulation binders, extruded Estane, plasticized Estane, and plasticized hydroxyl-terminated polybutadiene, as a function of temperature and strain rate. The mechanical response of the Estane was found to exhibit the strongest dependency on strain rate and temperature and higher flow strength for similar test conditions of the three materials tested. Plasticized Estane was less sensitively dependent on strain rate and temperature, followed by the plasticized HTPB. The visco-elastic recovery of all three binders is seen to dominate the mechanical behavior at temperatures above the glass transition temperature (Tg). There is a pronounced shift in the apparent Tg to higher temperatures as the strain rate is increased. Two distinct behaviors are observed in the binders below the Tg. At low strain rates, the binders exhibit a yield behavior, followed by a drop in the flow stress, which may or may not recover. At high strain rates, the load drop does not occur and the flow stresses either gradually increase, as in plasticized HTPB, or it levels out as seen in the Estane-based binders. POLYM. ENG. SCI., 46:812–819, 2006. © 2006 Society of Plastics Engineers
High-strain-rate (2000 s-1) compression measurements utilizing a specially-designed Split-Hopkins... more High-strain-rate (2000 s-1) compression measurements utilizing a specially-designed Split-Hopkinson-Pressure Bar have been obtained as a function of temperature from -55 to +50 °C for the plastic-bonded explosive PBX 9501. The PBX 9501 high-strain-rate data was found to exhibit similarities to other energetic, propellant, and polymer-composite materials as a function of strain rate and temperature. The high-rate response of the energetic was found to exhibit increased ultimate compressive fracture strength and elastic loading modulus with decreasing temperature. PBX 9501 exhibited nearly invariant fracture strains of ~1.5 percent as a function of temperature at high-strain rate. The maximum compressive strength of PBX 9501 was measured to increase from ~55 MPa at 50 °C to 150 MPa at -55 °C. Scanning electron microscopic observations of the fracture mode of PBX 9501 deformed at high-strain revealed predominantly transgranular cleavage fracture of the HMX crystals.
Accurate temperature measurements in dynamic systems have been pursued for decades and have usual... more Accurate temperature measurements in dynamic systems have been pursued for decades and have usually relied on optical techniques. These approaches are generally hampered by insufficient information regarding the emissivity of the system under study. We are developing NRS techniques to measure temperature in dynamic systems and overcome these limitations. Many neutron resonances have narrow intrinsic Breit-Wigner widths such that the resonance is substantially broadened by the atomic motion even at room temperature. Thus, accurate measurement of the Doppler contribution allows one to infer the material temperature, and for the conditions achieved using standard high explosives, the probe itself is not perturbed by the high temperature and pressure. Experiments are conducted using a pulsed spallation source at LANSCE with time-of-flight measurement of the neutron spectra. In initial experiments, we have demonstrated that measurements with ten percent accuracy are possible. We have fielded dynamic tests, most of which were neutron-flux limited. An overview of the approach and the status of our experimental campaign are discussed.
Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable... more Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.
Thermochimica Acta, 2002
Impact or thermal ignition of high explosives (HE) results in deformation that can lead to damage... more Impact or thermal ignition of high explosives (HE) results in deformation that can lead to damage. Fractures or defects, combined with sufficient pressure, dramatically increase the available surface area and potentially changes even the mode of combustion. Recent impact and cookoff experiments on PBX 9501, (HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, with a plasticized, Estane-based binder), have shown complex cracking patterns caused by impact or pressurization. Fast reactive waves have been observed to propagate through the cracks at hundreds of meters per second. We present experiments that examine the combustion of mechanically and thermally damaged samples of PBX 9501. Mechanically damaged samples, damaged by quasi-static compression, exhibit large, $200 mm stress fracture accompanied by extensive rubblization. Combustion experiments determine a 1:4 AE 0:6 MPa critical pressure for the onset of violent convective combustion, consistent with connected porosity of 25 mm. Thermally damaged samples, damaged by heating in a 180 8C oven for 30 min, exhibit 2-20 mm cracks distributed throughout the sample. Combustion experiments indicate a 9:2 AE 0:4 MPa critical pressure for the onset of violent convective combustion in the thermally damaged sample, consistent with connected porosity of 4 mm. Below the critical pressure, the burn rate and pressure exponent of thermally damaged PBX 9501 are close to those of the pristine material. #
Propellants Explosives Pyrotechnics, 1999
ABSTRACT The experimental hypervelocity jet initiation threshold criteria for neat nitromethane a... more ABSTRACT The experimental hypervelocity jet initiation threshold criteria for neat nitromethane and homogeneous- and heterogeneous-sensitized nitromethane mixtures have been determined over a range of failure diameters, jet velocities from 2–9 mm/μs, and jet diameters in two test configurations. These criteria were used to define detonation and failure conditions in nitromethane and the nitromethane mixtures as a function of contact- and bow-shock conditions. These data were compared with data reported by others in the literature on bare solid explosives. A favorable comparison of threshold values is achieved by normalization of the criteria with the failure diameters. The effect on the initiation of the confinement proximity to the jet axis was also investigated. Experimental results have shown that high impedance boundaries near the jet axis induced conditions that allowed initiation to occur at lower jet velocities than those determined by the criteria. Tests also were performed on both homogeneous and heterogeneous nitromethane mixtures, having the same failure diameters, to determine if the same or similar jet penetration distances were required for initiation. The results, within experimental error, do not show any definitive differences in initiation conditions between the two types of mixtures.Kriterien für den Initiierungsgrenzwert von Nitromethan und Nitromethanmischungen bei Übergeschwindigkeit des HohlladungsstachelsDie experimentellen Kriterien der Initiierungsgrenzwerte von reinem Nitromethan und homogenen und heterogenen sensibilisierten Nitromethanmischungen bei Hohllandungsstachel mit Übergeschwindigkeit wurden bestimmt in einem Bereich der Versagensdurchmesser (Stachelgeschwindigkeit 2–9 mm/μs) und der Stacheldurchmesser bei zwei Testkonfigurationen. Diese Kriterien wurden verwendet zur Definition der Detonations– und Versagensbedingungen bei Nitromethan und Nitromethanmischungen als Funktion von ebener und schräger Stoßeinwirkung. Diese Daten wurden verglichen mit Daten aus der Literatur an reinen festen Explosivstoffen. Ein brauchbarer Vergleich der Grenzwerte wird erreicht durch Anpassung der Kriterien an die Versagensdurchmesser. Die Wirkung der Initiierung auf die Verdämmung nahe der Stachelachse wurde ebenfalls untersucht. Die experimentellen Ergebnisse haben gezeigt, daß eine starke Grenzflächenkopplung nahe der Stachelachse Bedingungen erzeugt, die eine Initiierung bei niedrigeren Stachelgeschwindigkeiten erlauben als bei den durch die Kriterien bestimmten. Untersuchungen wurden auch durchgeführt sowohl an homogenen und heterogenen Nitromethanmischungen, mit denselben Versagensdurchmessern, um zu bestimmen, ob dieselben oder ähnliche Eindringtiefen des Stachels erforderlich waren für die Initiierung. Die Ergebnisse zeigen innerhalb der experimentellen Meßunsicherheit keine entscheidenden Unterschiede der Initiierungsbedingungen bei den beiden Mischungsarten.Critères pour le seuil d'initiation du nitrométhane et des mélanges nitrométhane avec jet de charge creuse hypervéloceLes critères expérimentaux des seuils d'initiation du nitrométhane pur et de mélanges nitrométhane sensibilisés homogènes et hétérogènes avec jet de charge creuse hypervéloce ont été déterminés pour un domaine de diamètres ratés (vitesse de jet 2 à 9 mm/μs) et des diamètres de jet dans deux configurations de test. Ces critères ont été utilisés en vue de la définition des conditions de détonation et de défaillance pour le nitrométhane et les mélanges nitrométhane en fonction d'un choc plan ou incliné. Ces données ont été comparées à des données provenant de la littérature sur les explosifs solides. Une comparison favorable des seuils peut être obtenue par adaptation des critères aux diamètres ratés. L'effet de l'initiation sur le confinement à proximité de l'axe du jet a également été étudié. Les résultats expérimentaux ont montré qu'un fort couplage de la surface limite à proximité de l'axe du jet créait des conditions permettant une initiation à des vitesses de jets plus faibles que celles déterminées par les critères. Des études ont également été effectuées tant sur des mélanges nitrométhane homogènes qu'hétérogènes, avec les mêmes diamètres ratés, en vue de déterminer si l'on avait besoin des mêmes profondeurs de pénétration de jets ou de profondeurs semblables pour l'initiation. En tenant compte de l'erreur expérimentale, les résultats ne montrent pas de différences significatives des conditions d'initiation entre les deux types de mélange.
Several microstructural mechanisms have been suggested for ignition in explosives subjected to im... more Several microstructural mechanisms have been suggested for ignition in explosives subjected to impact by low-velocity projectiles. The shear-impact experiment, previously employed by Asay, et al. to dynamically study strain behavior, is engaged in this study to damage samples of PBX 9501 at various densities. Impact is achieved by using a gas gun projectile to drive a plunger which is in contact with the explosive. Various plunger shapes are utilized to produce different levels of shear in the sample. The experiment is designed to create damage by producing displacement in only two dimensions. Post-test analysis involving microscopy of polished surfaces reveals insightful patterns in consolidation and cracking, shear band development, and HMX phase transformation associated with ignition and subsequent quenching. Analysis of the samples in cross-section suggests the degree to which the assumption of two-dimensionality is valid.
Thermochimica Acta, 2000
Various plastic bonded explosives (PBXs) contain about 5-wt% polymer, plasticizer, and stabilizer... more Various plastic bonded explosives (PBXs) contain about 5-wt% polymer, plasticizer, and stabilizer as binder. The glass-transition temperature (T g ) determines, in part, if the binder will reduce or increase the sensitivity of the PBX to impact. A soft binder reduces the impact sensitivity; however, too soft a binder compromises the mechanical strength below that desirable for dimensional stability. Glass transitions were measured by temperature modulated DSC for PBXs before and after pressing. Pressing temperature was 90°C. The T g of Estane, a polyester/polyurethane used in some PBX binders, was investigated. Only small changes were observed in the low temperature T g of the soft segments but larger changes were seen in the higher temperature transitions due to the relaxation of the hard segments. The T g of Kel F 800, a binder used in insensitive PBX 9502, was observed near ambient temperature. The PBX 9502 had a lower T g than the neat polymer. Mechanical strength will be measured for the samples.
ABSTRACT Predicting the degree of violence of high explosive (HE) reactions for a given event is ... more ABSTRACT Predicting the degree of violence of high explosive (HE) reactions for a given event is desirable for risk assessments and a goal for computational models. Historically, different types of low amplitude impact tests on HE specimens have been performed to determine the critical impact-velocity threshold for high explosive violent reactions (HEVR). Additionally, the energy release relative to a steady-state detonation is also desirable for assessing the potential outcome of an accidental event. Traditionally, blast gauge measurements have been used to measure the overpressure of the HEVR event at a defined distance. This paper summarizes the use of this active technique coupled with a passive technique to derive average energy release curves for Modified Steven tests. A classic ballistic pendulum design was employed with the traditional blast gauge method. Calibration of the ballistic pendulum involved three elements. First, two mechanical measurements were related to the actual peak swing of the pendulum. Second, the general nature of the swing versus energy release curve was estimated. Two different approaches were used to estimate the momenta as a function of HE energy release using the Gurney relationships for an unsymmetrical sandwich. Finally, both techniques were simultaneously benchmarked with PBX 9501 calibration charges. Test results demonstrate the utility of using coupled diagnostic methods for low amplitude insult testing. Each set of data was fit to derive a working curve for the determination of the average energy release for HEVR event based on mass relative to a steady-state detonation. These tests results and working curve derivations are presented.
Synchro-ballistic use of rotating-mirror streak cameras allows for detailed recording of high-spe... more Synchro-ballistic use of rotating-mirror streak cameras allows for detailed recording of high-speed events of known velocity and direction. After an introduction to the synchro-ballistic technique, this paper details two diverse applications of the technique as applied in the field of high-explosives research. In the first series of experiments detonation-front shape is recorded as the arriving detonation shock wave tilts an obliquely mounted mirror, causing reflected light to be deflected from the imaging lens. These tests were conducted for the purpose of calibrating and confirming the asymptotic detonation shock dynamics (DSD) theory of Bdzil and Stewart. The phase velocities of the events range from ten to thirty millimeters per microsecond. Optical magnification is set for optimal use of the film's spatial dimension and the phase velocity is adjusted to provide synchronization at the camera's maximum writing speed. Initial calibration of the technique is undertaken using a cylindrical HE geometry over a range of charge diameters and of sufficient length-to- diameter ratio to insure a stable detonation wave. The final experiment utilizes an arc-shaped explosive charge, resulting in an asymmetric denotation-front record. The second series of experiments consists of photographing a shaped-charge jet having a velocity range of two to nine millimeters per microsecond. To accommodate the range of velocities it is necessary to fire several tests, each synchronized to a different section of the jet. The experimental apparatus consists of a vacuum chamber to preclude atmospheric ablation of the jet tip with shocked-argon back lighting to produce a shadow-graph image.
ABSTRACT The Modified Steven test geometry has been used with several different target designs to... more ABSTRACT The Modified Steven test geometry has been used with several different target designs to investigate the mechanical loading behavior of PBX 9501 to a low velocity impact. A 2 kg. mild steel spigot projectile is launched via a new powder driven gun design, from {approximately} 20 to 105 m/s, at lightly confined, steel targets. Brief descriptions of the gun design and operation are given. The threshold velocity to reaction for various target designs, different PBX 9501 lots, and different high explosive (HE) thicknesses are reported and compared. Various diagnostics have been employed to evaluate the pressure profile and timing, and target strain behavior relative to projectile impact. The violence of reaction, as measured by both passive and active techniques, is reported relative to a steady state detonation in PBX 9501. Experimental results suggest slightly different ignition mechanisms dominate based on (HE) thickness, resulting in delayed reactions from {approximately} 0.2- to 2.8-ms after impact. Post-test analyses of the PBX 9501 are briefly summarized.
Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed ... more Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.
Low amplitude impact tests on pristine and damaged, `baseline' and `aged' PBX 9501 specimens were... more Low amplitude impact tests on pristine and damaged, `baseline' and `aged' PBX 9501 specimens were performed to determine the critical impact-velocity threshold for violent reactions. HE damage was achieved by a single impact ranging in velocity from 36.9 to 54.4 m/s. External blast gauge and ballistic pendulum data were used to evaluate reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. Test results show that the damaged threshold 1) is lower than the pristine threshold and 2) is invariant to PBX 9501 lot-to-lot and age variables. .
Low amplitude impact tests on pristine and damaged, ‘baseline’ and ‘aged’ PBX 9501 specimens were... more Low amplitude impact tests on pristine and damaged, ‘baseline’ and ‘aged’ PBX 9501 specimens were performed to determine the critical impact-velocity threshold for violent reactions. HE damage was achieved by a single impact ranging in velocity from 36.9 to 54.4 m/s. External blast gauge and ballistic pendulum data were used to evaluate reaction violence relative to a steady-state detonation. Strain