Dynamic fracture analysis and its response by shock wave caused by the non-contact underwater explosion are significant in the design of reliable marine vessels. In the USA navy, it is regulated to conduct the shock test of the marine vessels under explosion conditions in the development stage. However, the shock test is limited because of very high costs and environmental safety concerns. As analytic solutions are also limited to very simple cases of fluid-structure interaction problems, an accurate numerical simulation technique is developed and proposed in the study. A dynamic fracture of a ring-stiffened cylinder subjected to a strong acoustic wave is analyzed by two steps: macro and micro analyses by MSC/DYTRAN and MSC/NASTRAN. In the macro analysis, fluid-structure interaction of a stiffened cylinder subjected to underwater explosion load is investigated. For the validity of the macro analysis, the response of a spherical body under simple plane wave and fluid-structure interaction of the cylinder under a spherical wave by underwater explosion are analyzed and compared with the analytic solution and experimental results. In the micro analysis, the dynamic stress intensity factor of a precracked ring stiffener is determined by the pressure time history of load obtained in the macro analysis. Three numerical methods determining the dynamic stress intensity factors are proposed and discussed. Also the preprocessor which can link macro and micro analysis is developed by PCL (Patran Command Language).
To secure the integrity of marine vessels against the shock, the failure modes and their causes are thoroughly understood. In the past, the data necessary for failure modes and the physics to failure have been obtained through process of underwater shock tests. However, this process is very costly and extremely limited to certain conditions. Analytic solutions are also limited to very simple cases of fluid-structure interaction problems (Huang, 1970).
