Theory And Test Research On Shock Vibration Bending Moment Of Ships Subjected To Underwater Explosion Load

Ship hull vibration and impact dynamic bending moment subjected to the underwater explosion load and wave impact load, together with still water bending moment and wave bending moment can endanger longitudinal strength of a ship. There is already much research about the dynamic responses of ship hulls subjected to the underwater explosion loads, which mostly focus on ship hull vibration or ship hull whipping motion, but there is just a little research about the impact dynamic bending moment and calculation methods are still rather raw. With the increasing focus on the impact dynamic bending moment subjected to the underwater explosion load during the ship design process, there is great significance value about the topic in this paper both from the engineering and the academic view. The impact dynamic bending moment is analyzed mainly by means of theoretical analysis, numerical simulations and model tests, and ship shock trails are scarce. So impact dynamic bending moment is analyzed theoretically based on ship shock trail in the paper. The calculation method is verified with ship test. And then how the explosion conditions, hull dimensional parameters and hull inherent parameters affect impact dynamic bending moment is analyzed in details below.Firstly, the ship shock trial is briefly introduced, and general arrangement of measurement of a ship shock trial is analyzed particularly. Data preprocessing methods are described, and a large amount of data is preprocessed, picked, filtered by Inverse Fourier Transform. The spectral analysis is applied to the date, and analysis of a large amount of strain dates is carried out for distribution law from transvers,vertical and longitudinal ship. Finally how characteristics of dynamic bending moment of the trial changing with the impulsive factor and collapse distance is analyzed detailedly.Secondly, based on the research status, one kind of engineering calculation method of impact dynamic bending moment which is based on ship hull model and modal superposition is been put forward, considering the influence of added water mass, varying buoyancy effects and ship damping. And the conception of impact dynamic bending moment is defined in the paper and several calculation methods are summarized. The Taylor's flat theory dealing with the problem of fluid-structure interaction of underwater explosion is applied and its limitation is discussed. Then a method of ship pressure underwater explosion based on ship shock trail is given in this paper and the calculation value is validated with the experiment value.Thirdly, this part mainly regards with influences by several parameters of the impact dynamic bending moment. Considering the superposition of the impact dynamic bending moment and wave bending moment, the influence of wave surface to the impact dynamic bending moment is analyzed quantitatively, which is more reasonable for the bending moment of ship on the sea. Then the modal composition of impact dynamic bending moment is analyzed.Also the impact dynamic bending moment induced by shock wave and bubble pulsating load respectively is calculated. At least, the influences of total ship hull damping to the impact dynamic bending moment is considered.Finally, the engineering calculation of the impact dynamic bending moment in regard to some kinds of ships is carried out and rules of ships' moment is analyzed when the traditional impulsive factor and standard displacement varies respectively. The impact dynamic bending moment is calculated based on the new impulsive factor compared with traditional impulsive factor. The empirical formula about the moment is presented according to impact dynamic bending moment of all kinds of ships finally, which is convenient for engineering application.