Studies On Shock Environment For Equipments On Surface Ship And Anti-Shock Characteristics Of Structures

Modern warship inevitably encounters shock damage due to water explosion in a naval battle. With the quick development of guided missile, laser-bomb and weapon in water, and with the obviously increasing of mass and explosion time of bomb, shock environment for equipments, anti-shock characteristics of structures and equipments of warship should be deeply studied in detail, which will assure the safety and the normally work of ship structure and increase vital force and battle effectiveness of warship.However, it is a very complex nonlinear dynamic process that warship is shocked by underwater explosion. The process that the structure of warship is attacked by huge shock load within very short time belongs to big deformation and strong nonlinear problem due to interaction between the fluid and the hull. The underwater explosion includes many parameters, such as the type of detonator, the mass of detonator, the distance, the environment of underwater and the structural properties of the warship. For the complication of underwater explosion, it is very difficult to build an explicit numerical model for describe the problem of underwater explosion by using analytical method. In the same time experiments of underwater explosion are not often carried out for that it is a kind of very expensive devastating experiment. In addition, the experimental results are limited for generalization because there are some uncertainty and strongly nonlinear in the underwater explosion problem. Therefore, with the development of technology of nonlinear finite element (NFEM) method and the improvement of computer, the numerical simulation strategy will take on a more and more important role in dealing with the underwater explosion problem.The paper adopts a compositive research method including analytical method, numerical simulation strategy and model experiment method studying the shock environment of equipment on warship and the anti-shock properties of the warship structure. The paper presents a numerical simulation method applied to the problem of underwater explosion of ship on the basis of studying visualized NFEM. A serial of processes from detonator explosion, the spread of shock wave, to the dynamic response of the structure under shock wave are numerical simulated in the paper. Based on the simulation results, the paper concludes the structural damage deformation and mechanics of damage of the typical warship. The shock environment of equipment on the warship is predicted in the paper and the prediction equations of shock environment of equipments on surface ship are deduced. In addition, the paper discusses the new type shock resistance structures, and gives four new type shock resistance structures, which show favorable energy absorption behavior. Finally, the model experiment is carried out, and the experimental results validate the numerical simulation results.The main research contents of the paper are as follows:(1)The numerical simulation method of explosion of detonator and the spread of explosion load are built based on studying the theory of shock wave. The paper obtains the properties of underwater load and the spread rule by simulating the underwater loads with the MSC.DYTRAN software,and realize the simulation of the whole process of underwater explosion. In the same time, some key technologies in simulation are discussed including the reasonable determination the range of water, element size, the boundary condition of fluid, parameters of detonator and water,and adopts the parameter of element size which is dimensionless, to obtain the best element size in order to solve the problem about the explicit for simulation results. Simultaneously, the effects of different sea bottom which include soil, sandstone,rock, and rigid bottom to shock wave are studied in detail. The experimental results show that the presented method can preferably simulates the spread process of shock wave.(2)The paper calculates numerically the dynamic response of warship under explosion load, and concludes the properties of the dynamic response about structure and equipments. Furthermore the effect trend of mass of detonator and the distance of explosion to the dynamical response are given, and the effect rules are concluded. In addition, some factors such as bomb in different angle with the shipside and the different sea floor condition including infinite water depth and the rigid boundary are considered, and the effect principals are given.(3)The properties of the dynamic response of main equipments including displacement, velocity and acceleration are analyzed based on studying the dynamic response of the structure. And the shock spectrums of main equipments on the warship are plotted. The paper concludes the relationship among explosion shock factor, location parameters of equipment and shock environment of equipments. Finally, the prediction equations of shock environment of equipments on surface ship are deduced. The example results show that the predict method is convent, quick and correct.(4)The paper analyzes deeply the structural damage deformation and mechanics of damage of the typical warship. Furthermore, the paper presents new type double-bottom structures, which satisfy the requirement of warship design and have the excellence on energy absorption, the density of material, the technics of manufacture. The prosperities of shock resistance of new type double-bottom structures are simulated. The paper also analyzes the properties of shock resistance of the warship with the longitudinal flitch filled within foam and the effect of single floor shock isolator and double floors shock isolator. (5)The shock resistance model experiment of warship structure and equipment is carried out on basis of the numerical simulation about shock environment of surface ship and the theoretical research on structural anti-shock . Through analyzing the experimental results, the paper obtains the spread rule of underwater explosion load. In the same time the experiment results validate the effectiveness of shock resistance of cap-structure and semi-tube-structure. The stainless steel wire isolator shows favorable shock resistance property.