Combustion in Cracks of PBX 9501


Book Description

Recent experiments involving the combustion of PBX 9501 explosive under confined conditions reveal the importance of crack and flaws in reaction violence. Experiments on room temperature confined disks of pristine and thermally damaged PBX 9501 reveal that crack ignition depends on hot gases entering existing or pressure induced cracks rather than on energy release at the crack tip. PBX 9501 slot combustion experiments show that the reaction propagation rate in the slot does not depend on the external pressure. We have observed 1500 d s in long slots of highly-confined PBX 9501. We present experiments that examine the combustion of mechanically and thermally damaged samples of PBX 9501.




Convective Burning in Gaps of PBX 9501


Book Description

Impact or thermal ignition of high explosives results in deformation that can lead to fracture. Fracture, combined with high pressure, dramatically increases the available surface area and potentially changes the mode of combustion. Recent impact and cook-off experiments on PBX 9501 (HMX, octahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocine, with a binder) have shown complex cracking patterns caused by impact or pressurization. Fast reactive waves have been observed to propagate through the cracks at about 500 m/s. We present experiments that investigate the propagation of fast reactive waves in cracks of PBX 9501, focusing on the reactive wave velocity and on the interplay of pressure and crack size. Experiments at initial pressures of 6.0 MPa reveal monotonic reactive wave propagation velocities of around 7 m/s for a 100 micrometer slot. We observe reactive wave velocities as high as 100 m/s in experiments at initial pressures of 17.2 MPa and various slot widths. Similar experiments at lower pressure exhibit oscillatory reactive wave propagation in the slot with periodic oscillations whose frequencies vary with combustion vessel pressure. This is the first reported observation of oscillatory combustion in cracks of an energetic material such as PBX 9501. Threshold pressure experiments for combustion propagation into closed-end slots of PBX 9501 find that combustion propagates into 2 mm, 1 mm, 100 micrometer, 50 micrometer, and 25 micrometer slots at approximately 0.1, 0.2, 0.9, 1.6, and 1.8 MPa, respectively.




Shock Wave Science and Technology Reference Library, Vol. 5


Book Description

Los Alamos National Laboratory is an incredible place. It was conceived and born amidst the most desperate of circumstances. It attracted some of the most brilliant minds, the most innovative entrepreneurs, and the most c- ative tinkerers of that generation. Out of that milieu emerged physics and engineering that beforehand was either unimagined, or thought to be f- tasy. One of the ?elds essentially invented during those years was the science of precision high explosives. Before 1942, explosives were used in munitions and commercial pursuits that demanded proper chemistry and con?nement for the necessary e?ect, but little else. The needs and requirements of the Manhattan project were of a much more precise and speci?c nature. Spatial and temporal speci?cations were reduced from centimeters and milliseconds to micrometers and nanoseconds. New theory and computational tools were required along with a raft of new experimental techniques and novel ways of interpreting the results. Over the next 40 years, the emphasis was on higher energy in smaller packages, more precise initiation schemes, better and safer formulations, and greater accuracy in forecasting performance. Researchers from many institutions began working in the emerging and expanding ?eld. In the midst of all of the work and progress in precision initiation and scienti?c study, in the early 1960s, papers began to appear detailing the ?rst quantitative studies of the transition from de?agration to detonation (DDT), ?rst in cast, then in pressed explosives, and ?nally in propellants.













Shock Compression of Condensed Matter - 2001


Book Description

This collection of 336 papers discusses recent research on the response of inert and energetic materials to high-pressure environments produced by rapid loading phenomena. This includes theoretical, computational (modeling/simulation) and experimental studies of inert and energetic materials, as well as ballistic and material synthesis studies and advances in experimental techniques. All papers have been peer-reviewed.










Observation of the Behaviour of Confined PBX 9501 Following a Simulated Cookoff Ignition


Book Description

The response of small confined disks of PBX 9501 to cookoff has been investigated with high-speed photography through a transparent toughened-glass window, observing both the ignition and propagation of reaction. External strain gauges and microwave interferometry have been used to measure the expansion of the confining ring. The results show that when reaction starts, cracks propagate from the ignition site and that these cracks may be effective in leading to the fast transfer of ignition to other sites within the charge.