An inverse method for the equation of state of detonation products from underwater explosion tests

Abstract

Since the information of detonation product is transmitted outward in the form of compression wave during underwater explosion, the purpose of this paper is to explore how to determine the equation of state (EOS) of detonation products using underwater explosion tests. Compared with conventional cylinder test, underwater explosion test has the advantages of simpler equipment, lower cost, less limited charge size, and wider range of calibration pressures, which makes it more suitable for the on-site testing of large or non-ideal explosives. Based on the measurable shock wave trajectory and post-shock pressure history in general underwater explosion test, an inverse method of characteristics (inverse MOC) is proposed to recover the gas-water interface from the shock and post-shock data, and a genetic algorithm is developed to determine the EOS of detonation products by the gas-water interface. Compared with virtual experimental data extracted from underwater explosion simulations, it is found that the inverse MOC can properly reproduce the position and pressure of gas-water interface. The lower limit of pressure range is close to 2 MPa, which is far lower than that of 0.1 GPa in cylinder test. Based on the inversed results of gas-water interface, it is also confirmed that the genetic algorithm can also stably optimize the parameters of JWL equation because the isentrope pressure error of eight commonly used explosives is less than 3% in the range of detonation pressure 0.01 GPa. The results show that it is by the inverse MOC and genetic algorithm that the EOS of detonation products can be properly and stably determined by the underwater explosion test data.