Saturated Impulse For Ship Plates Subjected To Impulse Loading

In general,the impulse loading imposed on the ship plates is represented only by the maximum load and total impulse of the loading pulse.However,researches on saturated impulse show that the total impulse design based on the loading pulse is inaccurate.Only the part of the impulse which is no more than the value of saturated impulse has an influence on the permanent deformation.Hence,the prediction of the large deformation of ship plates is more reasonable and accurate when taking account of the effect of the saturated impulse.In this thesis,the rigid-plastic and elastoplastic methods are developed to study the mechanism of the saturation phenomenon.The main contents are as follows:(1)The rigid plastic and elastoplastic method to analyse the dynamic response of ship plates under impulse loading.The rigid-plastic method can deduce simple analytical solutions or half analytical solution with clear mechanics characteristics and physical meaning through simplifying the actual material properties.Whilst the elastoplastic method,such as the finite element analysis,should be applied when the shape and material properties play important roles in the response of structures.By comparing the rigid-plastic method and elastoplastic method,an integrated method is proposed to analyse engineering problems,which gives full play to the strengths of two methods.(2)The influence of the boundary conditions,pulse shapes and travelling plastic hinges on the saturation impulse of ship plates.Seven different boundary conditions,and five different pulse shapes are employed to investigate how the boundary conditions,pulse shapes and travelling plastic hinges affect the saturation phenomenon and its physical mechanism.(3)An equivalent method that replacing the pulse with various shapes to equivalent rectangular pulse.Saturation equivalent method is proposed based on the saturation phenomenon.Both the rigid-plastic method and the elastoplastic method are applied to test equivalent results.Besides,the saturation equivalent method is compared with two other equivalent methods which are widely used in the industrial design to reveal the physical mechanism of the equivalent method.(4)Critical P-I curves for the tensile tearing failure of the fully clamped ship plates under impulse loading based on saturation phenomenon.According to the empirical formula of blast loading and experimental results of slamming tests,tensile tearing failure P-I diagrams are drawn to improve the shock-resistant design of the ship plates under extreme working conditions such as blast and slamming.