Analysis And Research On The Hydroelastic Free Vibration Of Stiffened Rectangular Plate

Stiffened plate is widely used in aeronautic, marine, architectural and mechanical fields.Toward high-speed ship , taken as complex architecture above water,forcasting the local vibration exactly can reduce the storage of the frequencies ,and then the stiffness of the structure is decreased,sequentially,the weight of the structure can be cut down.In most cases, stiffened plate of high-speed ship works in the fluid or its surface contacts with fluid .So it is necessary to study the hydroelastic vibration of the stiffened plate which contacts with water by one side or both sides to prevent the local vibration and enhance the effectiveness of structures.This thesis is mainly concerned with the hydroelastic free vibration of stiffened rectangular plate which contacts with water by one side or both sides. On the basis of structure finite element method and 2-dimensional fluid boundary element method deduced by simple Green's function , the hydroelastic vibration of the stiffened plate which contacts with water by one side or both sides can be solved . In the thesis,added mass matrix can be achieved by the approximate calculating method'-1'and the fluid boundary element method respectively. The intercross method is applied to get the frequencies and mode shapes of hydroelastic free vibration . Finally the theoretical developments made in this thesis are confirmed by comparing them to the results got by ANSYS.According to the above theories ,the author composed and debugged more than 6000 lines computational programs in FORTRAN and MATLAB .It can be used to calculate the free vibration of plate,beam ,grillages or stiffened plate structure respectively and plot the corresponding mode shapes .Moreover ,the program can calculate the frequencies and plot the mode shapes of the plate(or stiffened rectangular plate) contacted with water by one side or both sides.Conclusions can be drawn as the following: (1)The numerical results of programs prove that stiffened plate simulated by plate-beam model is reasonable.The programs can be used to analyse the hydroelastic vibration of stiffened rectangularplate. (2) Discerning the mode of plate from the stiffened plate is practical to prevent and control the vibration of the stiffened plate. (3)The approximate formula^ guarantees very good accuracy for low modes. (4)Considering the interaction between fluid and structure ,it is more reasonable to apply the intercross method to calculate the mode and frequencies of the stiffened rectangular plates contacting with water.