Numerical study on deformation and ignition process of impacting granular HMX explosive in drop hammer test

Two-dimensional numerical simulation of the impact process for drop hammer on granular HMX was carried out by using ANSYS/AUTODYN software. The temperature rise generated in particles was estimated via the principle converted from plastic work to heat energy based on the calculated values of stress and plastic work. The HMX particles was geometrical shapes and round, assuming that the particles had elastic-plastic deforming properties. Particle stack form had two kinds of situations of regular and irregular arrangement. The initial velocity of the drop weight was calculated through setting the drop height and the formula of free fall. For different drop heights and the calculation of different yield stress values of sample particle material, the temperature rise changes in particles under drop hammer impact were obtained. The results showed that the regular arrangement produces low temperature (37.2℃) rise, whereas the irregular arrangement produces higher temperature (142.9℃) rise. In irregular arrangement, the local plastic deformation work of particles can lead to higher temperature rise, causing particle ignition. At the same time, considering the uncertainty of the yield stress value of HMX, the calculation of temperature rise is performed taking the smaller yield stress value(0.13 GPa), while the other calculation conditions are the same, and the temperature rise obtained is 83.2℃, which got 59.7℃ lower than the yield stress value of 0.26 GPa.