Blast Loading on Plain and Perforated Tubes with High Explosives
Upadhyay, Anil Kumar
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According to the assessments of the United Nations, there are more than 100 million mines lying buried in various conflict zones of many countries in the world. As per their assessment, many thousand casualties happen every year. Most of the demining operations are generally carried out after the conflicts end. This task is one of the most challenging and always a risky operation. There are various demining equipment available world-wide to perform this job in addition to the manual demining of minefield by trained soldiers. Explosive loading on machine components of service vehicles during military operations is a complex process. The complexity stems from unpredictable detonation, complicated component geometry and geographical terrain, debris effects etc. Consequently, the damage on structural components becomes highly unpredictable. There are too many other environmental parameters contributing to the final damage. In this context, both high explosive loading and material response behave like independent random variables. Blast loading on tubes and plates is vital in the design of combat and demining equipment of real life situations. Therefore, study of plain circular tubes (PCT), perforated circular tubes (PRCT) and plates subjected to blast loading due to explosion of high explosives such as TNT, RDX and TETRYL has been considered in the present thesis. Due to various design constraints, it is extremely difficult to design these components for desired service life for high quantum of blast load. This thesis explains the uses of perforations for handling this inevitable and extreme condition of loading on the target components. It is pertinent to note that the various blast parameters such as time of sight, overpressure, impulse etc. available in the literature are not reliable for close range of explosion of high explosive for scaled distance in order of 0.40 m/kg1/3. Therefore, it is essential to establish and quantify some of these parameters for close range blast, which will be useful for real life design problems. Accordingly, the present thesis covers experimental and numerical study of plain circular tube (PCT) and perforated circular tube (PRCT) under blast loading of high explosive. iv CONWEP code has been used for numerical simulation of PCT and PRCT subjected to blast loading. Some important blast parameters have been established in this research. It has been shown that there is approximately 58 % reduction in blast impact on the tube due to use of perforation. Square and hexagonal pattern of perforation has been studied. Theory of strong explosion has been discussed in the present thesis. Non-dimensional time and length scale has been proposed in place of scaled distance. Also, simplified empirical formula has been proposed for estimation of time of sight for close range blast covering scaled distance 0.40 m/kg1/3 - 0.45 m/kg1/3.