The performance of various testing columns in small-scale horizontal burning studies

The use of Critical Oxygen Index testing columns in the horizontal configuration is investigated. Gas analysis results from within columns of simple design indicate that they are unsuitable for burning studies because of entrainment of the external atmosphere and recirculation of combustion products. A new design of column and holder is proposed that eliminates these effects and provides a possible means of studying small-scale horizontal combustion in different oxygen/nitrogen mixtures.     

Microabrasion-corrosion of cast CoCrMo alloy in simulated body fluids

Wear and corrosion of metal-on-metal hip replacements results in wear debris and metal-ion release in vivo, which may subsequently cause pain and hypersensitivity for patients. Retrieved metal-on-metal hip replacements have revealed that two-body sliding wear and three-body abrasive wear are the predominant wear mechanisms. However, there is a lack of understanding of the combined effects of wear/corrosion, especially the effect of abrasion-corrosion.This study investigates the sliding-corrosion and abrasion-corrosion performance of a cast CoCrMo alloy in simulated hip joint environments using a microabrasion rig integrated with an electrochemical cell. Tests have been conducted in 0.9% NaCl, phosphate buffered saline solution, 25% and 50% bovine serum solutions with 0 or 1 g cm^-3 SiC at 37 °C. Experimental results reveal that under abrasion-corrosion test conditions, the presence of proteins increased the total specific wear rate. Conversely, electrochemical noise measurements indicated that the average anodic current levels were appreciably lower for the proteinaceous solutions when compared with the inorganic solutions. A severely deformed nanocrystalline layer was identified immediately below the worn surface for both proteinaceous and inorganic solutions. The layer is formed by a recrystallisation process and/or a strain-induced phase transformation that occurs during microabrasion-corrosion.     

The Mechanical Sensitiveness of Titanium/Blackpowder pyrotechnic compositions

Titanium/blackpowder compositions have been involved in a number of ignition incidents during consolidation. We report the results of a systematic study to investigate the effects of the particle size and proportion of titanium on the mechanical sensitiveness of such mixtures. Our results indicate that the compositions are sensitive to both impact and friction stimuli and that the forms of the dependence on titanium content are different. Mixtures of blackpowder with 20%–30% titanium have been shown to be particularly friction sensitive. We have also found that the sensitiveness of titanium/blackpowder compositions to mechanical forces is independent of the particle size of titanium over the range investigated in this study.     

Changes in the Mechanical Sensitiveness of Explosives as a Result of Previous Exposure to Elevated Temperatures

The ambient temperature sensitiveness of blackpowder formulations was found to be relatively unaffected by prior elevated temperature storage, whereas the results for pyrotechnic flash composition indicated that there was a significant change in sensitiveness as a result of previous temperature exposure. Both the single and double based propellants became more sensitive to friction after short term storage (1 day) but this trend was reversed at the end of 10 days. The behaviour of the nitroglycerin (NG)-containing explosives was found to depend on their NG concentration; high concentration materials became more sensitive, while lower concentration materials became less sensitive.     

Technical investigation of the explosion on 22 March 1989 at Peterborough,England

The paper presents the results of a detailed technical investigations of the cause of the fire and subsequent explosion at Peterborough on 22 March 1989 involving a vehicle containing a mixed load of explosives and detonators. Tests were done to examine the sensitivenes and thermal stability of items of the load, and the behaviour of packaged explosives using drop, vibration and fire tests. Communication testing was undertaken with boxes of detonators, and ignition tests with boxes of fuseheads provided information relating to the characteristics of the fireballs generated. From analysis of the scientific data obtained, we conclude that the initial fire resulted from ignition of fusehead combs which were being transported in unauthorized and unsafe packaging, and we suggest a mechanism for detonatino involving the functioning of strewn detonators on fire-damaged boxes of explosives.