Underwater Card Gap Test Method For The Determination Of The Experimental Study And The Approximate Calculation Of The Explosive Shock Sensitivity

A new method was developped to test the shock sensitivity of explosives, called Underwater Card Gap Experiment (UCGE). Its characteristic is the combination of underwater explosion method and shock sensitivity experiments (small scale gap test).Firstly, the underwater explosion energy of six explosives (TNT, PETN, RDX, passivated RDX, 8701 and expanded ammonium nitrate explosive) are obtained under the condition that non card gap is used. The standard values are used to decide whether the detonation process happens or not in the UCGE afterwards.Secondly, Bruceton up-and-down method is applied in UCGE. With the card gap of polyethylene, experiments are carried on to test the shock sensitivity of six explosives at 50% detonation probability. The results of thickness of card gap are found to show the sequence of the shock sensitivity (from high to low):PETN > RDX > 8701 > desensitized RDX > TNT > expanded ammonium nitrate explosive.The contrast between experimental results and literatures and results got by traditional gap test indicates that the experimental results are believable. It also demonstrates the feasibility that traditional gap test can be placed by UCGE to a certain extent. Further more, the impact of charge density towards the shock sensitivity is investigated. The results are in agreement with that of other methods, showing that the bigger the charge density, the lower the shock sensitivity.Finally, shock wave attenuation laws in gap medium are studied and original parameters of card gap in experimental condition are calculated according to the basic hypothesis of approximate calculation. With the reference of critical pressure values of shock wave in relative literatures, the characteristics of two attenuation models are analyzed.