Experimental And Numerical Research On Damage Of Stiffened Cylindrical Shells Based On Underwater Explosion Shock Wave And Bubble Impluse

With the development of anti-submarine technology in modern naval warfare,submarines are seriously threatened by underwater weapons in the execution of tasks.However,due to the complexity of underwater explosion load and submarine structure,the existing research on damage characteristics of submarine structure under underwater explosion load is still insufficient,which seriously restricts the improvement of impact resistance of modern submarines.Underwater explosion experiment is the most reliable research method.In this paper,the safety of submarine in underwater explosion is taken as the engineering background,and the submarine reinforced cylindrical shell structure are taken as the research object.The damage characteristics of the stiffened cylindrical shell structure under the underwater explosion shock wave(UESW)and bubble load(BL)are studied by using scaled model experiment and numerical simulation method.In this paper,firstly,aiming at the response of cylindrical shell structure under UESW and BL,the research status at home and abroad is reviewed through theory,numerical method and experiment,respectively.The damage problem of cylindrical shell structure is mainly introduced,and the coupling mechanism of explosion load,hydrostatic pressure,cavitation secondary loading are analyzed.The deficiencies of the experimental and numerical studies on the damage characteristics of stiffened cylindrical shells under UESW and BL are discussed,and the research route and structure framework of this paper are determined.Secondly,the theory of underwater detonation and the principle of shock wave and bubble pulsation are discussed.The reflection of single-layer and transmission of double-layer cylindrical shells for UESW considering hydrostatic pressure is deduced theoretically.Based on the transmission theory of shock wave,an experimental method for simulating the deep-water explosion environment is designed.The local damage of stiffened cylindrical shells with different forms and thicknesses is studied according to the similarity theory of underwater explosion base on the shrinkage model and experimental scheme of submarine cabin structure damage experiment taking hydrostatic pressure into account.Aiming at the overall damage of stiffened cylindrical shells,the construction method and experimental scheme of shrinkage model of submarine overall structure damage experiment are put forward based on the principle of cycle ratio similarity.The safety protection scheme of data measurement system,cables and instruments in underwater explosion experiment,the hoisting of experimental model and launching of underwater explosion experiment are also discussed.The operation flow of the experiment is analyzed and the solutions are given to provide technical support for the subsequent underwater explosion experiments.Thirdly,based on the scaling model of local damage experiments,the numerical models of single-layer and double-layer stiffened cylindrical shells are established.Based on the arbitrary Lagrangian Euler method,the numerical simulation of the whole process of shock wave phase and bubble pulsation phase of stiffened cylindrical shells subjected to underwater non-contact explosion is carried out.The different forms of shock wave in cylindrical shells are summarized.The propagation law of structures and adjacent waters,the action mechanism of explosion bubble load on stiffened cylindrical shells and the damage mode of stiffened cylindrical shells are analyzed.The coupling characteristics of dynamic response and cavitation effect of stiffened cylindrical shells under shock wave load are analyzed.The plastic damage law of ribs of single-layer and double-layer cylindrical shells is analyzed,and the influence of inner and outer ribs on the anti-explosion performance of cylindrical shells is discussed.The effects of various factors and structural parameters of underwater explosion on the structural response of stiffened cylindrical shells are summarized.Fourthly,the damage of single-layer and double-layer stiffened cylindrical shell models subjected to underwater contact explosion shock wave is numerically simulated.By analyzing the shape of impact cracks and their generation and tearing process of different stiffened cylindrical shell structures,the influence of stiffeners on the damage mode of cylindrical shell structures is explored,and the impact factors of underwater explosion and structural parameters on the damage mode of stiffened cylindrical shell structures are discussed.On the basis of shock wave damage break,the movement process of bubbles in the vicinity of the break is simulated numerically.And the bubble pulsating jet state near the break and its secondary damage characteristics to the structure of the break are analyzed under the different pressure between inside and outside of the cylindrical shell.Fifthly,a series of experimental studies on local structural responses and damage characteristics of stiffened cylindrical shells with different forms and thicknesses under UESW and BL are carried out.Aiming at the mid-field and near-field underwater explosion,the influence of hydrostatic pressure on structural response and damage mode is explored.Based on the numerical study of local damage,the free-field pressure load and shell wall pressure load experimental data are analyzed,and the mechanism of underwater explosion load on stiffened cylindrical shells and the propagation law in the nearby flow field are studied,and the cavitation secondary loading characteristics of stiffened cylindrical shells are discussed.The damage modes and response laws of stiffened cylindrical shells are explored by experimental data such as velocity,plastic damage and strain.The free-field pressure,wall pressure and acceleration signals are processed by HHT method,and the time-frequency characteristics of shock wave load,cavitation secondary load and BL as well as the energy dissipation mechanism of each load in the propagation process are analyzed.The validity of the numerical method is verified by comparing with the experimental results.Finally,the fluid-structure interaction process of the overall model of underwater explosion bubble and stiffened cylindrical shell is numerically simulated,and the interaction mechanism is summarized.The shape of explosion bubble,damage characteristics and damage modes from different conditions are analyzed,and the influence of underwater explosion and structural parameters on the overall response of stiffened cylindrical shell structure is discussed.The overall damage characteristics of stiffened cylindrical shells subjected to underwater explosion bubbles are experimentally studied.The pressure signals and strain data of free field are analyzed.The whip-like motion and the failure modes of stiffened cylindrical shells subjected to explosion bubbles are explored.The effectiveness of bubble loads on the overall longitudinal strength damage of stiffened cylindrical shells is verified,and the numerical method is validated.