A Numerical Study Of Dynamic Responses Of Aluminum Vessels Subjected To Underwater Shock

In combat operations, underwater explosion is one of the major threats to a nearby ship. The underwater shock wave can damage the equipments,hurt the crews and even seriously destroy the hull.As aluminum alloy is widely used in the shipbuilding in recent years, it is possible for aluminum alloy to become a new material for some warships.Consequently, the resistance of the aluminum alloy ship to underwater shock damage will be more and more concerned.Since there is rare research about aluminum ship subjected shock wave, in this thesis, the main content are included and organized as follows.First, characteristics of underwater explosion are described in order to elementarily recognize this phenomenon. The Geers & Hunter model that calculate loadings of underwater explosion and coupled acoustic-structure algorithm that simulate coupled fluid-solid of underwater explosion are deeply studied. In addition, Central difference method that computes the discretized finite element equations are explained either.Then, dynamic responses of circular plate and cylinder subjected to underwater shock wave are first studied by using the coupled acoustic-structure algorithm embedded in ABAQUS.Numerical results are obtained and compared to the experimental data. The results from present model are close to the observed values, which validate the accuracy and reliability of this method.Third, the comparison between aluminum and steel plate is carried out by using the same method. Not only the influence of material's density, strain rate, Young's modulus and yield strength but also charge weight and standoff distance are considered. The results indicate that density plays a key role during the resistance of material to underwater shock damage. When the shock factor is great, the strain rate could enhance the resistance of material to underwater shock damage. And there are also certain relationships between Young's modulus, yield strength and resistance of impact.Finally, the detail finite element model of a small aluminum alloy ship is established. Analysis on dynamic responses of aluminum alloy ship subjected to shock wave loading is carried using the same method. Responses of time history such as the acceleration, velocity, displacement and stress or strain are presented. The variation for peak value of responses is also obtained. Moreover, plastic deformation of ship,pressure and cavitation in fluid are studied.These results are available for aluminum alloy ship resist underwater shock damage.This thesis represents a preliminary study of the resistance of aluminum ship to underwater shock damage. Shock resistant design of aluminum ship structure and comparison between aluminum and steel ship are merit further study.