Optimal design of a novel cylindrical sandwich panel with double arrow auxetic core under air blast loading

The increasing threat of explosions on the battle field and the terrorist action requires the development of more effective blast resistance materials and structures.Curved structure can support the external loads effectively by virtue of their spatial curvature.In review of the excellent energy absorption property of auxetic structure,employing auxetic structure as core material in curved sandwich shows the potential to improve the protection performance.In this study,a novel cylindrical sandwich panel with double arrow auxetic(DAA) core was designed and the numerical model was built by ABAQUS.Due to the complexity of the structure,systematic parameter study and optimal design are conducted.Two cases of optimal design were considered,case1 focuses on reducing the deflection and mass of the structure,while case2 focuses on reducing the deflection and increasing the energy absorption per unit mass.Parameter study and optimal design were conducted based on Latin Hypercube Sampling(LHD)method,artificial neural networks(ANN) metamodel and the nondominated sorting genetic algorithm(NSGA-Ⅱ).The Pareto front was obtained and the cylindrical DAA structure performed much better than its equal solid panel in both blast resistance and energy absorption capacity.Optimization results can be used as a reference for different applications.

Influence of the spatial distribution of underground tunnel group on its blasting vibration response

The spatial distribution of underground tunnels is significant to the stress redistribution in the surrounding rock masses and blast wave propagation.The field blasting tests were first carried out to study the propagation of blast-induced seismic waves through under-ground tunnels of the Xiluodu Hydropower Station in China.The results show that the peak horizontal particle vibration velocity can be used as a safety criterion for underground tunnels.The effects of in situ stresses and spatial distributions of the tunnel group on the vibra-tion velocities distribution is afterward investigated by numerical simulation.The results show that there is a significant amplification of the blasting vibrations in the adjacent tunnels,which depends on their vertical positions during the excavation of a tunnel.The peak vibration velocity decreases as the lateral separation between tunnels increases.When the separation between the tunnels exceeds the width of three tunnels,the impact of the blast waves on each part of the adjacent tunnel tends to be stable on the whole.In terms of the size of the tunnel,the blasting vibration velocity in the upper part of the straight wall on the front-blast side increases as the width increases(and then levels off),while the blasting vibration velocity in the lower part decreases as the width increases(and then levels off).Finally,a generalized formula of blasting vibration velocity considering the spatial distribution is established,which can well predict the vibration velocity of particles in underground tunnels.