Experimental Investigation of the Effect of Time Delays on Fragmentation in Homogenous Models

摘要

The effect of delay blasting on fragmentation is studied in this paper. The optimum delay sequence for fragmentation was determined. Homogeneous two dimensional transparent polymeric models were employed so that high speed photography in conjunction with dynamic photoelasticity could record the full field state of stress associated with explosive loadings. The transparent material also allowed observation of the initiation and extension of cracks. Two ranges of delays were selected for study. Short delays were used to investigate the effect of interaction of stress waves from the second hole with the stress waves from the first hole. In a second series, utilizing relatively long delays, cracks from the first hole were allowed to propagate a finite distance before the second explosion was set off. This was done to investigate the effect of interaction of stress waves from the second hole with the cracks from the first hole. It was found that there was a significant increase in fragmentation when the second hole was initiated as the cracks resulting from the first detonation reached it.