On June 30, 2020, a 0.87 gram PETN charge being pressed in the Rapid Prototyping Facility (RPF), unexpectedly initiated, resulting in destruction of the pressing fixture but no injuries or facility damage. In response, the Safety Review Board (SRB) met on Aug. 13, 2020 and Oct. 1, 2020 to review information collected following the incident, consider likely direct causes, and form recommendations.
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Society for Experimental Mechanics - SEM Annual Conference and Exposition on Experimental and Applied Mechanics 2010
The "DaMaGe-Initiated-Reaction" (DMGIR) computational model has been developed to predict the response of ideal high explosives to impulsive loading from non-shock mechanical insults. The distinguishing feature of this model is the introduction of a damage variable, which relates the evolution of damage to the initiation of a reaction in the explosive, and its growth to detonation. This model development effort treats the non-shock initiation behavior of explosives by families; rigid plastic bonded, cast, and moldable plastic explosives. Specifically designed experiments were used to study the initiation process of each explosive family with embedded shock sensors and optical diagnostics. The experimental portion of this model development began with a study of PBXN-5 to develop DMGIR model coefficients for the rigid plastic bonded family, followed by studies of the cast, and bulk-moldable explosive families, including the thermal effects on initiation for the cast explosive family. The experimental results show an initiation mechanism that is related to impulsive energy input and material damage, with well defined initiation thresholds for each explosive family. These initiation details will be used to extend the predictive capability of the DMGIR model from the rigid family into the cast and bulk-moldable families. © 2010 Society for Experimental Mechanics Inc.
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AIP Conference Proceedings
Alumina-filled epoxies are composites having constituents with highly dissimilar mechanical properties, resulting in complex behavior during shock compression and release. Two distinguishing characteristics are amplitude-dependent wave structures and high release wave velocities. Recent studies examined the effects of various compositional changes on these shock properties. As expected, the strongest effects were observed when the total alumina volume fraction was reduced in steps from a nominal 43% to 0%. In the present study, compositions prepared over the same range of alumina loadings were examined at initial temperatures that were nominally -55 °C or 70 °C. Experimental configurations were identical to previous room-temperature experiments. Laser interferometry and wave timing were used to obtain transmitted wave profiles, Hugoniot states, and release wave velocities. Initial densities were determined from thermal expansion coefficients measured for each composition. Although initial density changes are very small, significant temperature effects on shock properties were observed. © 2007 American Institute of Physics.
AIP Conference Proceedings
A strong electric field can be generated when the shock-induced depoling current from a normally poled PZT 95/5 sample is passed through a large resistive load. The portion of total depoling current that is retained on the sample electrodes to account for capacitance is governed by the dynamic dielectric properties of both unshocked and shocked material. Early studies used measured load currents from single samples to assess models for dielectric response. In more recent studies, we used shock-driven circuits in which multiple PZT 95/5 elements were displaced both parallel and perpendicular to the shock motion. This allowed both load and charging currents to be measured for individual elements that are subjected to shock compression and release at different times. In the present study, these techniques have been utilized to examine dielectric properties in PZT 95/5 samples at initial temperatures from -56 to 74 °C. Significant changes in permittivity with temperature are observed in both unshocked and shocked samples. Measured currents show a complex dielectric response which can only be partially predicted using a simple dielectric relaxation model. © 2007 American Institute of Physics.
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