The traditional study of underwater explosions (UNDEX) with respect to ship damage became of interest during World War II when torpedo explosions near a ship created more damage than a direct hit. Following the war, many full scale ship shock trials were conducted that provided much of the empirical data that is used in the field today. However, one type of shock phenomena became of interest in the late 1960s that potentially could be more damaging than a typical underwater explosion; an implosion. Crude implosion experiments were conducted in the late 1960s. Although these experiments collected data on pressure waves, more emphasis was placed on the acoustical properties associated with an implosion event. Today, one of the Navy's concerns is about the potential for the implosion of a pressure vessel in close proximity to a submarine hull. A computational approach is desired that will predict the source strength of an implosion. This thesis will cover the basic principals of underwater shock phenomena, including explosions and implosions. Drawing from previous experiments and computational simulations, a detailed investigation of the implosion event will be made using, DYSMAS, a coupled Eulerian-Lagrangian solver. DYSMAS will be used to compare the characteristics of implosion and explosion events. / US Navy (USN) author.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 143-145). Also available online.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 93-94). Also available online.

Thesis (M.S.)--Naval Postgraduate School, 1962. / Thesis Advisor(s): Cunningham, W. P. "1962." Description based on title screen as viewed on January 22, 2009. Includes bibliographical references (p. 32). Also available in print.

Approved for public release; distribution is unlimited. / The USS Winston S. Churchill (DDG-81) shock trial was conducted in May and June of 2001 off the coast of Naval Station Mayport, Florida. Because the USS Winston S. Churchill best represented the new line of Flight II-A Arleigh Burkes, it was chosen to undergo ship shock trials for its class. These trials are necessary in order to evaluate the vulnerability and survivability of the hull and the mission essential equipment in a "combat shock environment". However, shock trials are very expensive, require extensive planning and coordination, and represent a potential hazard to the marine environment and its mammals. Computer modeling and simulation are showing themselves to be a plausible alternative in investigating the dynamic response of a ship under these shock trials conditions. This thesis investigates the use of computer ship and fluid modeling, coupled with underwater explosion simulation and compares it to actual shock trial data from the USS Winston S. Churchill. Of particular concern in this study is the amount of fluid that must be modeled to accurately capture the structural response of a full ship finite element model. Four fluid meshes were constructed and used to study the ship's response to an underwater explosion. Each simulation data was analyzed to determine which mesh best represented the actual ship shock trial results. / Lieutenant, United States Navy

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 69-70). Also available online.

Approved for public release; distribution is unlimited. / During World War II many surface combatants were damaged or severely crippled by close-proximity underwater explosions from ordnance that had actually missed their target. Since this time all new classes of combatants have been required to conduct shock trial tests on the lead ship of the class in order to test the survivability of mission essential equipment in a severe shock environment. While these tests are extremely important in determining the vulnerabilities of a surface ship, they require an extensive amount of preparation, manhours, and money. Furthermore, these tests present an obvious danger to the crew on board, the ship itself, and any marine life in the vicinity. Creating a virtual shock environment by use of a computer to model the ship structure and the surrounding fluid presents a valuable design tool and an attractive alternative to these tests. This thesis examines the accuracy of shock simulation using the shock trials conducted on USS WINSTON S. CHURCHILL (DDG 81) in 2001. Specifically, all three explosions that DDG 81 was subjected to are simulated and the resulting predictions compared with the actual shock trial data. The effects of fluid volume size, mesh density, mesh quality, and shot location are investigated. / Lieutenant, United States Navy

Thesis (Mechanical Engineer and M.S. in Mechanical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Young S. Shin. Includes bibliographical references (p. 161-162). Also available online.

In this investigation a method is suggested for determining the dynamic, elastic response of a thin hemispherical shell subjected to a head-on attack by the initial shock wave of an underwater explosion. The shell which is fastened to the end of a fixed, semi-infinite tube of the same radius is surrounded by a high density fluid similar to water, and the internal cavity of the shell is filled with a low density fluid similar to air. The initial shock wave moves through the high density fluid. In the neighborhood of the obstacle, the shock front propagates in the direction of the axis of the semi-infinite tube and makes initial contact with the obstruction at the tip of the hemisphere at time equal to 0+. The following basic assumptions are used to define the mathematical model for the physical problem. The shock wave is considered to be a plane pressure pulse with exponential decay, the surrounding fluid is treated as if it were an acoustic medium, and the low density fluid is assumed to exert a constant pressure over the interior surface of the shell. The thin, hemispherical shell is regarded as being constructed of an isotropic, homogeneous, Hookean material of constant thickness. This shell experiences only small displacements. Moreover, in this model, the hemispherical shell is attached to a rigid, semi-infinite tube in such a way that the normal and in-plane displacements of the middle surface of the shell and the slope of the middle surface of the shell in the longitudinal direction are all zero at the shell-tube connection. The investigation for the solution to this axisymmetric problem, in which the mathematical formulations on the displacements of the shell and the velocity potential of the fluid are coupled, is begun with the separation of the displacements of the middle surface of the shell into two parts, ( )_M and ( )_B displacements. These are then shown to be analogous to the "membrane" and "pure bending" displacements familiar in the theory of static shells. The governing equations and the determinative conditions for the ( )_M displacements are found to be independent of the ( )_B displacements, while in the ( )_B formulation the ( )_M displacements are found to appear only in the determinative conditions. An approximate solution which is valid for small time and in which Poisson's ratio and the in-plane inertia term are assumed to be zero is obtained for the ( )_M displacements. A complementary solution for the ( )_B displacements which is valid in the neighborhood of the shell-tube connection is determined by using geometric and kinematic approximations in the ( )_B formulation. Approximate solutions for the displacements of the middle surface of the shell are then formulated by combining the ( )_M and ( )_B expressions above with the assumptions (valid only for the stated small time range) that the ( )_B contribution to the in-plane displacement is negligible over the entire shell and that the ( )_B contribution to the normal displacement is negligible except in the region near the shell-tube connection. Numerical results are calculated for a steel shell immersed in sea water and these results are presented in the form of tables and plots. / Ph. D.

Underwater explosions (UNDEX) generate high-energy shock waves that pose significant risks to military personnel during training exercises and combat scenarios. The primary objective of this research is to develop a surrogate modeling framework using engineering materials to investigate the biomechanical response of lung tissue during UNDEX events. A representative lung surrogate was designed to mimic the mechanical behavior of human lungs, utilizing thermoplastic elastomers (TPE) and polyurethane foam to replicate the elastic and porous nature of lung tissue and alveolar sacs. Material characterization tests were conducted to simulate quasi-static deformation through uniaxial tensile tests and dynamic loading conditions using dynamic mechanical analysis (DMA). The viscoelastic response of the surrogate material across a wide range of temperatures and frequencies is presented. A series of UNDEX experimental tests were conducted on the surrogates using the Virginia Tech Shockwave Generator (SWG), with targeted overpressures ranging from 10 to 20 psi. The surrogates were instrumented with sensors to record changes in principal strains and internal pressures. The results were analyzed to evaluate strain and pressure trends, impulse, and potential injury mechanisms. A linear relationship was observed between shockwave impulse, peak pressure, and principal strains, while no significant differences in internal pressure dynamics were observed within the tested blast overpressure ranges. / Master of Science / Underwater explosions create powerful shockwaves that can damage ship structures, affect marine life and harm military personnel during combat scenarios. However, the effects of these shock waves on the human body are not well understood. This study aims to fill that gap by studying representative models that replicate human lungs to help us better understand how they respond in dynamic conditions. Lung models were fabricated from commercially available materials that mimic the soft and elastic nature of the human lungs. The selected materials were extensively tested to understand its behavior under both static and dynamic conditions. Additionally, blast experiments were simulated using a shockwave generator to subject the models to controlled shock waves with pressures ranging from 10 to 20 psi. Pressure and strain sensors were mounted on the models to observe the dynamic changes that occur during exposure to shockwaves. Overall, the use of lung models as an alternative to live tissue is demonstrated and the experimental results were analyzed and discussed by evaluating injury mechanisms.