Modeling the effects of aluminum and ammonium perchlorate addition on the detonation of the high explosives C_4H_8O_8N_8 (HMX) and C_3H_6O_6N_6(RDX)

Metalized high explosives effectively tailor the explosion impulse at lowered detonation pressures of common high performance explosives such as C_3H_6O_6N_6 (RDX) and C_4H_8O_8N_8 (HMX). The presence of aluminum (Al) with and without ammonium perchlorate (AP) allows the subsequent burning for longer and sustained reactions of enhanced blast explosives. The modeling of reaction rate laws for three explosives with varied amounts of Al, AP, RDX, and HMX is reported. The model validation included the rate stick test for understanding the explosive reaction of the three samples and the large-scale gap test for determining their ignition sensitivity. The experimental results confirmed the accuracy of the model in simulating the shock sensitivity and the size effects before detonation failure. The effect of enhanced blast of these explosives in the presence of Al and AP is also reported

Modeling the shock-induced multiple reactions in a random bed of metallic granules in an energetic material

An investigation of shock–particle interactions in reactive flows is performed using an Eulerian hydrodynamic method with a hybrid particle level-set algorithm to handle the material interface dynamics. The analysis is focused on the meso- to macro-scale numerical modeling of a granular metalized explosive containing randomly distributed metal particles intended to enhance its blast effect. The reactive flow model is used for the cyclotrimethylene-trinitramine (RDX) component, while thermally induced deflagration kinetics describes the aerobic reaction of the metal particles. The complex interfacial algorithm, which uses aligned level sets to track deforming surface between multi materials and to generate the random shape of granule elements, is described for aluminized and copperized RDX. Then, the shock-induced collapse of metal particles embedded in the condensed phase domain of a high explosive is simulated. Both aluminized and copperized RDX are shown to detonate with a shock wave followed by the burning of the metal particles. The energy release and the afterburning behavior behind the detonating shock wave successfully identified the precursor that gave rise to the development of deflagration of the metal particles

Neural crest stem cells undergo multilineage differentiation in developing peripheral nerves to generate endoneurial fibroblasts in addition to Schwann cells

Neural crest stem cells (NCSCs) persist in peripheral nerves throughout late gestation but their function is unknown. Current models of nerve development only consider the generation of Schwann cells from neural crest, but the presence of NCSCs raises the possibility of multilineage differentiation. We performed Cre-recombinase fate mapping to determine which nerve cells are neural crest derived. Endoneurial fibroblasts, in addition to myelinating and non-myelinating Schwann cells, were neural crest derived, whereas perineurial cells, pericytes and endothelial cells were not. This identified endoneurial fibroblasts as a novel neural crest derivative, and demonstrated that trunk neural crest does give rise to fibroblasts in vivo, consistent with previous studies of trunk NCSCs in culture. The multilineage differentiation of NCSCs into glial and non-glial derivatives in the developing nerve appears to be regulated by neuregulin, notch ligands, and bone morphogenic proteins, as these factors are expressed in the developing nerve, and cause nerve NCSCs to generate Schwann cells and fibroblasts, but not neurons, in culture. Nerve development is thus more complex than was previously thought, involving NCSC self-renewal, lineage commitment and multilineage differentiation

Simulating Thermal Explosion of Octahydrotetranitrotetrazine-based explosives: Model Comparison with Experiment

The authors compare two-dimensional model results with measurements for the thermal, chemical and mechanical behavior in a thermal explosion experiment. Confined high explosives are heated at a rate of 1 C per hour until an explosion is observed. The heating, ignition, and deflagration phases are modeled using an Arbitrarily Lagrangian-Eulerian code (ALE3D) that can handle a wide range of time scales that vary from a structural to a dynamic hydro time scale. During the pre-ignition phase, quasi-static mechanics and diffusive thermal transfer from a heat source to the HE are coupled with the finite chemical reactions that include both endothermic and exothermic processes. Once the HE ignites, a hydro dynamic calculation is performed as a burn front propagates through the HE. Two octahydrotetranitrotetrazine (HMX)-based explosives, LX-04 and LX-10, are considered, whose chemical-thermal-mechanical models are constructed based on measurements of thermal and mechanical properties along with small scale thermal explosion measurements. The present HMX modeling work shows very first violence calculations with thermal predictions associated with a confined thermal explosion test. The simulated dynamic response of HE confinement during the explosive phase is compared to measurements in larger scale thermal explosion tests. The explosion temperatures for both HE's are predicted to within 1 C. Calculated and measured wall strains provide an indication of vessel pressurization during the heating phase and violence during the explosive phase

The Lantern Vol. 5, No. 1, December 1936

• All of Us • Public Dance • In Tibet, of All Places • Thoughts • Subterranean Conflict on the Campus • Out, Out Into Fragrance and Sweetness • My Soul Steals Out to Meet You In the Night • Bored Young Lady • Guay Shin\u27s Prayer • On Playing Ping-Pong • The Love-Life of One Cat and the Death of Another • My Lady • Danger! Germs Working! • The Wolves • Letters from India • With Apologies to Hamlet • The Dreamhttps://digitalcommons.ursinus.edu/lantern/1015/thumbnail.jp

The Lantern Vol. 5, No. 3, May 1937

• Dedication • Dr. McClure: An Ursinus Man • Roar, O Wind! • To the Ladies! • The Futility of Dying • The Symbolism of the British Crown • Oh! • It Might Have Been • Treat Yourself? • Three Writers • Hawaii in June • On Being a Twin • Black Magic • Triangle • Who Longs? • A Son Passes • Sing an Old-Fashioned Song • Questioning • An Argument About a Fish • That Morning Eye-Opener • Scoop for the Sun • The Dead Do Not Die Once • Give Us Timehttps://digitalcommons.ursinus.edu/lantern/1010/thumbnail.jp

Laser-generated shock wave attenuation aimed at microscale pyrotechnic device design

To meet the rising demand for miniaturizing the pyrotechnic device that consists of donor/acceptor pair separated by a bulkhead or a thin gap, the shock initiation sensitivity in the microscale gap test configuration is investigated. For understanding the shock attenuation within a gap sample (304 stainless steel) thickness of 10∼800 μm, the laser-generated shock wave in water confinement is adopted. The shock properties are obtained from the free surface velocity by making use of a velocity interferometer system for any reflector (VISAR). Analytical models for plasma generation in a confined geometry and for evolution and decay of shock waves during the propagation are considered. The shape and amplitude of the laser-driven initial pressure load and its attenuation pattern in the gap are effectively controlled for targeting the microscale propagation distance and subsequent triggering pressure for the acceptor charge. The reported results are important in the precise controlling of the shock strength during the laser initiation of microscale pyrotechnic devices

A direction sensitive detonation model for granular to continuum scale for shock initiation of pentaerythritol tetranitrate single crystal in multi-dimensions

Experiments have shown that the shock sensitivity of a single crystal pentaerythritol tetranitrate (PETN) has a strong dependence on the crystal orientation. The ignition and growth (I & G) model has been widely used in studies of the shock initiation of energetic materials while the model is independent of the direction of compression, and thus it is impossible to address anisotropic sensitivity of such material. In this paper, we base our new model in the recently proposed reactive flow concept that incorporates an anisotropic ignition mechanism that depends on both strain and strain rate which are given in the general tensor notation. A multi-dimensional simulation is performed in order to illustrate the strain dependence of the initiation of a PETN pellet. The model is applicable to any anisotropic energetic material subjected to a shock impact, not limited to single crystal PETN