J-C Constitutive Relation at Low Strain Rates for DNAN-Based Aluminium Explosives

The drop response problem of the explosive charge is a typical low-velocity impact ignition problem, which exhibits the characteristics of low strain rate, long pulse width, and small pulse, and it is significantly different from the high-velocity impact ignition. In order to study the dynamic mechanical characteristics of a typical underwater weapon warhead charge drop conditions, the dynamic compression test of DNAN-based aluminum explosives was carried out by using the split Hopkinson pressure bar(SHPB), and the normal strain rate loading was achieved by the incident wave shaping technique. The stress-strain curves of DNAN-based aluminum explosives at five low strain rates, 80, 180, 28, 360, and 440 s−1 were obtained under the conditions of normal temperature and normal pressure. The Johnson-Cook(J-C) constitutive model was used to fit the parameters of the test data and verified by numerical simulation. The results show that the elastic modulus, yield strength, yield strain, failure stress, and failure strain of DNAN-based aluminum explosives all increase with the increase in strain rate; using the fitted J-C constitutive parameters can well restore the dynamic mechanical behaviors of DNAN-based aluminum explosives at low strain rate in numerical simulation, and it can provide strong data support for the related numerical simulation calculation of the drop safety.