It is well known that when “Low” explosives are deflagrated in a material, radial cracks are produced from the inner surface of the charge hole. The growing directions of these radial cracks could not be predicted normally, but it might be useful if we could control such growing directions. Therefore, in this paper, the possibility to control the directions of radial cracks has been discussed by using the results of the stress analysis which was undertaken by using the finite element method and also those of the experiments.
As the results, it was concluded both theoretically and experimentally that for the case that the material was broken by the quasi-static gas pressure of “Low” explosives, in other words, “Low” explosives of which rate of deflagration was less than about 300m/s were used, the direction of the radial cracks could be controlled by using a specially designed cartridge of which sectional shape was shown in Fig. 1 (a). Namely, the cement mortar block was separated clearly into two parts, as if it was cut out with a knife, by the explosion of a specially designed cartridge of the “Low” explosives of which rate of deflagration was about 100m/s, and no radial cracks towards the undesired directions were observed. Furthermore, the reason why the directions of the cracks were controlled was clarified by the results of the stress analysis.
