Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session Y5: EM.1 Detonation III |
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Chair: Ryan Wixom, Sandia National Laboratories Room: Cascade I |
Friday, July 12, 2013 9:15AM - 9:30AM |
Y5.00001: Novel Small-scale Technique for Determining Detonation Velocity Daniel Preston, Larry Hill, Bryce Tappan Measuring the local detonation velocity of an explosive has been limited to rate stick and cylinder tests. These tests traditionally used break wires, pins, and more recently PDV as a velocity diagnostic. These experimental techniques can be very accurate at measuring detonation velocities but are costly and require tens to hundreds of grams of material. This paper presents a novel small-scale technique for inferring detonation velocity from a modest sized pellet of explosive. A streak image is taken of the breakout shock on the flat output side of the pellet. Assuming a spherical shock wave, one can show that the breakout trace is of hyperbolic form. From this, one can simultaneously infer detonation velocty and apparent center. This method is ideal for energetic formulation and synthesis development due to the small amount of material required. Furthermore, this paper discusses the accuracy and limitations of this technique. [Preview Abstract] |
Friday, July 12, 2013 9:30AM - 9:45AM |
Y5.00002: Computer Simulations to Study the Effects of Explosive and Confinement Properties on the Deflagration to Detonation Transition (DDT) John Reaugh, John Curtis, Mary-Ann Maheswaran We have augmented the HERMES model (High Explosive Response to MEchanical Stimulus) by adding a modification to the CREST (Computational Reaction Evolution dependent on Entropy (S) and Time) detonation model. We have applied the combined model in ALE 3D to simulate DDT in an experimental configuration comprising an explosive confined in a tube and ignited at one end. We assess the quantitative effects of explosive properties and of tube geometry and material properties on the location of the detonation transition. For a fixed porosity, we find that the specific surface area of the explosive particles, in combination with the explosive's pressure-dependent burn rate, have strong influence on the transition to detonation. The run-to-detonation properties of the explosive powder (given by the Pop-plot) also have strong effect. In our simulations, the speed of the ignition front has less effect on the transition. The ignition front is caused by hot product gas moving through the permeable bed of explosive particles. In our single-velocity, multi-species approximation, we specify the ignition front speed as an input parameter. The results of our simulations help us identify the independent experiments that must be performed and analysed before a model for DDT can be validated. [Preview Abstract] |
Friday, July 12, 2013 9:45AM - 10:00AM |
Y5.00003: A view on the functioning mechanism of EBW detonation - Part 2: Exploding Bridgewire Output Elizabeth Lee, Rodney Drake, John Richardson This paper is the second of three looking at the initiation of PETN in an exploding bridgewire detonator. The first study examined the interactions between the fireset and bridgewire. This second study focuses on quantifying the effect of bridgewire burst energy on the output from the bridgewire at burst. A suite of experimental tests have been performed to characterise the output from the bridgewire in terms of the stimulus it would apply to the surrounding PETN in an EBW detonator. The expansion speed of the bridgewire at burst as a function of input energy has been measured using Photonic Doppler Velocimetry (PDV). This work has enabled an estimate to be made of the duration of the shock generated by the bridgewire explosion. To compliment these measurements an aquarium test was performed to measure the shock pressure, also as a function of input energy. In addition to a variable input energy, a number of bridgewire materials were studied. This suite of experimental tests has indicated a relationship between the ionisation energy of the bridgewire material and the detonator threshold energy. The results of the experimental work will be presented, together with the EBW detonator conceptual model developed as a result. [Preview Abstract] |
Friday, July 12, 2013 10:00AM - 10:15AM |
Y5.00004: Review of the concept and of the equations of the weldability window for explosive welding. Application to the explosive welding of stainless steel to carbon steel in cylindrical configuration Jose B. Ribeiro, Ricardo Mendes, Altino Loureiro Explosive cladding/welding is usually considered a solid state process in which the detonation of a certain amount of an explosive composition is used to accelerate one of the materials to be weld against the other. By this way a high velocity oblique collision is promoted and that will be responsible for the materials bonding. The conditions that should be met to achieve good welds define what is called as a weldability window or criteria. A weldability criteria based on the collision point velocity (Vc) and on the collision angle ($\beta )$ is the most used today. In the $\beta $-Vc space the weldability window is defined by four lines or limits. Despite of its widely used in explosive welding works, neither the concepts behind those limits neither the equations used to define them in the $\beta $-Vc space are particularly clear. Contradictory concepts, and equations with undefined variables or parameters, are commonly found in the literature. This paper aims to clarify those concepts and equations through an integrated description of the weldability limits and a presentation of the reviewed associated equations with the variables and parameters, including their units, clearly defined. The reviewed concepts and equations are then used for the description of the explosive welds of stainless steel to carbon steel in cylindrical configuration. [Preview Abstract] |
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