The Research On Ship's Stiffened Plate Large Plastic Deformation And Strain Field Subjected To Underwater Explosion Impact Loads

In the sea combat,naval ships could be subject to the attack from different weapons,when it was protecting the rights and interests of our country,and a major type is the underwater explosive pressure.In some conditions,underwater explosive pressure can lead to the ship lose its combat capability or even sink,which is dangerous to the people and equipment on it.So it is important to calculate the response of the naval ship when it is withstanding the underwater explosive pressure.Due to its excellent mechanical properties,stiffened plates are largely used in ships and large aircrafts and so on,especially in ship,it is widely used in the bottom of ship,the side of ship and the superstructure of ship and so on,so it has an indispensable engineering significance to study the plastic large deformation of stiffened plates when it is suffering from the underwater explosive pressure.Considering the importance of stiffened plates' strength,this paper is studying its dynamic plastic response when it is withstanding the underwater explosive pressure.First,it is solved by theoretical derivation,and it is assumed the material of beams and plates used in this theory is rigid-plastic,then deriving it by the principle of virtual velocities.At last,it is verified by some underwater explosion experiments and proved this method has some practical value.Then the nonlinear finite element software ABAQUS is used to simulate the response of whole ship model.First,it is also used the underwater explosion experiments to test the reliability of ABAQUS.Then many work conditions are calculated according to different shock factors,and the objects of these work conditions include the stiffened plates in bow,midship,stern.According to the analysis of them in different pressure of underwater explosion,some data of large plastic deformation and strain can be obtained,at the same time,the characteristics of response and the weaknesses of stiffened of plates can also be received.Based on the plasticity dynamics theory,a mechanical model is proposed to calculate the rigid plastic beams' residual strain field by using the law of plastic hinges motion.It is derived respectively both how to calculate the strain caused by moment only and how to calculate the strain caused by moment and membrane force.And this paper also simulates the strain field of rectangular plates with different length-width ratio and thickness,some data about the strain distribution can be obtained by analyzing the simulated results.The purpose of thesis is giving a theoretical method to calculate the dynamic plastic response of stiffened plates,especially under the shock wave pressure and bubble pressure,and study the plastic response of stiffened plates from the total ship model by finite element simulation,and to calculate the residual strain field of simple beams and plates,some calculation models and simulations are given,all of these results can give some reference value to the studies of naval ships' large plastic deformation and residual strength.