The influence of charge geometry on the response of partially confined right circular stainless steel cylinders subjected to blast loading

- Internal blast tests on steel cylinders were performed.
- Aspect ratio and charge mass were varied to obtain a range of cylinder responses.
- Finite element simulations were performed to understand the loading.
- Concept of lateral effective charge mass used to develop empirical relationship between deflection and charge dimensions.

This article presents an experimental and numerical investigation into the effect of charge geometry on the structural response of right circular cylinders. Thin-walled, seamless 304 stainless steel cylinders were subjected to internal blast loads that were generated by detonating bare cylindrical plastic explosive charges. Charge diameter, charge mass and aspect ratio were varied. Partial confinement was created by closing one end of the cylinder and leaving the other end free to vent to air. The axial impulse, maximum diametric deflection and axial shortening increased with increasing aspect ratio when the charge diameter was kept constant. When the charge mass was kept constant, the long charges caused larger diametric deflections than their mass equivalent shorter charges. The shorter charges transferred more axial impulse to the ballistic pendulum than their mass equivalent longer charges. The concept of effective charge mass (axial and lateral) was used to interpret the results and developed to provide an empirical equation relating deflection to the charge dimensions. Numerical simulations were performed which gave good agreement with the experimental data and predicted similar trends. The model revealed that the longer charges produced more diametric deflections than their mass equivalent shorter charges because a high pressure (above 50 MPa) zone, that covered a larger area and had a longer duration, developed at the cylinder wall in the case of longer charges. The insights from the model are in good agreement with the simple concept of lateral effective charge mass developed herein. When compared to spherical charge detonations in similar steel cylinders, the cylindrical charge detonations produced pressure waves which are more directional, have lower peak pressures and dissipate more gradually. The cylinders exhibited a more pronounced secondary bulge at the clamped boundary for cylindrical charge detonations.