SIMULATION OF EXPANSION AND FRAGMENTATION OF A CYLINDRICAL SHELL SUBJECTED TO INTERNAL DETONATION BY THE SMOOTHED PARTICLE HYDRODYNAMICS METHOD

The elastic-viscoplastic behavior and failure of ductile metal shells under internal detonation have an application to military and scientic elds of research. It is an important issue in a variety of circumstances, like structure protection, weapon eectiveness and safety application. After starting detonation in a fully charged shell, pressure waves are generated and transferred to the shell wall. The amount of this pressure wave is several times greater than the ultimate strength of the material, and is close to the CJ pressure of the explosive. Simulation of the process of fragmentation is very complex and challengeable. It involves many dynamic processes, such as detonation wave generation in explosives, interaction of the shock wave with the shell, expansion of the shell at a high strain rate, and eventually failure and fragmentation of the shell case. So, using a theoretical method is very sophisticated and, in some cases, impossible. Also, experimental testing is dangerous and requires expensive equipment to capture the dynamic properties of the shell. Therefore, identication and use of numerical methods that have the ability to realistically simulate this process have priority. In this research, expansion, fragmentation and post failure behavior of OFHC copper cylindrical shells under internal detonation of a C4 charge, have been simulated by a smoothed particle hydrodynamic method (SPH). The main advantage of this method, in comparison to conventional methods, such as the element deletion method, is realistic simulation of the fragmentation process due to complete satisfaction of the mass conservation law in the problem domain. Spatial distribution and approximate number and velocity of the fragments are obtained by implementation of the SPH method. Also, the leakage of detonation through case fragment products was simulated. Comparison of the expansionary deformation proles obtained from simulation with the experiments showed that the average dierence is less than 8%. The fracture radius of the shell and the velocity of fragments are compared with theoretical relations and good agreement between them has been observed.