Investigation of a New Shock Factor to Assess an Air-Backed Structure Subjected to a Spherical Wave Caused by an Underwater Explosion

Abstract

As a complex process, an underwater explosion is affected by different factors. Shock factors are variables used to characterize the severity of a shock based on scaling laws, which are conventionally used to designate the effect of an underwater explosion on a target. To reveal the mechanism involved in the dynamic response of an air-backed plate induced by underwater explosion, this study established a new shock factor to explain the dynamic mechanism of an underwater explosion. The shock factor was defined as the total energy impacting a structure that is subjected to a spherical wave. To validate the effectiveness of the shock factor, both numerical and centrifugal modeling were adopted. The numerical results indicate that changes in the standoff distances, defined as the distance between explosives and the upstream surface of a structure, and the eccentric distances, defined as the distance between explosives and the centroid of the structure wet surface, have almost no influence on the strain energy, kinetic energy, or total energy of the air-backed plate, at constant shock factor. Then the centrifugal test results were used to assess the dynamic responses under different explosive weights, standoff distances, and water depths. The results show that both near- and far-field underwater explosions were effectively assessed using shock factors. The shock factor with clear physical significance unifies the effects of explosive weight, explosive position, and structure dimension. The shock environment could be simply evaluated by the shock factor when subjected to an underwater explosion, which could also be useful in designing model tests based on scaling laws.