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The deflagration process of pressed HMX-based PBX cylindrical billets confined in metal tube is diagnosed by combined pressure, velocity-meter, high-speed frame photographic and radiographic diagnostic system. The reaction violence evolution is analyzed with consideration of convective flame propagation along the seam between explosive billet and tube wall, the follow-up conductive reaction on the side surface and between the end faces of explosive billets based on the observation on radical expansion and fracture of tube wall, axial length stretching and pullback to negative less than initial length which leads to the breakup of explosive column and final extinguishment of combustion after fracture. In the relatively light confinement of deflagration tube, the reaction violence growth is deformation and following fracture of tube wall. Only few cracks inside explosive billets with convective burning are observed before tube fracture. The blast overpressure record and post experiment recovery explosive specimens suggest that only few percentage of explosive mass is consumed during lightly confined deflagration. [ABSTRACT FROM AUTHOR]

A multi-channel PDV probe is designed to diagnose quantitatively the dynamic response of metal flyers in the collision region of two head-on sliding detonation waves by measuring the free surface velocity of particles normal to free surface near the collision plane. The results show typical regular reflection for W, Cu and Mach stem configuration for Sn, Pb, Ce in result of oblique colliding of two shock waves. These high spatial and time resolution velocity profiles can be used as early time stage benchmark for the validation of hydrodynamic codes and digital clue to retrace the kinetics leading to the formation of low density jet-like spiking in the collision region at late stage after colliding event. [ABSTRACT FROM AUTHOR]

The self-organization of multiple shear bands in a 304L stainless steel(304LSS) thick-walled cylinder (TWC) was numerically studied. The microstructures of material lead to the non-uniform distribution of the local yield stress, which play a key role in the formation of spontaneous shear localization. We introduced a probability factor satisfied the Gaussian distribution into the macroscopic constitutive relationship to describe the non-uniformity of local yield stress. Using the probability factor, the initiation and propagation of multiple shear bands in TWC were numerically replicated in our 2D FEM simulation. Experimental results in the literature indicated that the machined surface at the internal boundary of a 304L stainless steel cylinder provides a work-hardened layer (about 20~30μm) which has significantly different microstructures from the base material. The work-hardened layer leads to the phenomenon that most shear bands propagate along a given direction, clockwise or counterclockwise. In our simulation, periodical single direction spiral perturbations were applied to describe the grain orientation in the work-hardened layer, and the single direction spiral pattern of shear bands was successfully replicated. [ABSTRACT FROM AUTHOR]

We conducted experiments to study the ejecta from explosively shocked Pb targets. In the experiments we diagnose the ejected mass and dynamic system through use of piezoelectric pins, optical fiber probes, Asay foils, Asay windows, laser Doppler velocimetry, and high speed photography. The mass, the density distribution and the corresponding velocity distribution of micro-spall fragments of the Pb target are presented. We also study the sensitivity of Pb ejecta production to the loading rate and the peak shock stress. [ABSTRACT FROM AUTHOR]

The spall behaviors of pure iron DT2 and FeMnNi alloy are investigated experimentally. The impacts for DT2 are symmetric and with same thickness for both flyer and target plates. It is found a multiple spalling happened as the pressure exceeds the α-[variant_greek_epsilon] transition threshold (13GPa). In the asymmetrical experiments of FeMnNi alloy, a shallow spalling occurs when the impact pressure exceeds the transition pressure of 6.9GPa. Such abnormal spalling phenomena are believed to relate to the α-[variant_greek_epsilon] phase transition of iron. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]