Calculating Dynamic Characteristics Of Ship Stiffness Plate Structure By Finite Dynamic Element Method

During dump design of ship structure, it has significance to evaluate the frequency of ship board structures for prevent the sympathetic vibration between structures and motivation source. When using finite element method (FEM), the elements should be small enough to get higher order internal characteristics which satisfy the appeal of engineering. Thus it can result a large amount of DOF, and the model property of elements meaningless. Finite dynamic element method (DEM) established on the theoretical basis of finite element corrects the shape functions of FEM. Shape functions with frequency are adopted which replace the static ones to resolve dynamic property problems of structures. Based on DEM theory, this paper calculated the frequency and response of ship stiffened plate structure, and compared them with the ones acquired from FEM.What this paper does is as following:First, on the basis of Przemieniecki finite dynamic element concept, those are respectively calculated as follow: dynamic shape functions, dynamic stiffness and mass matrices of Timoshenko beam element and QUAD4 rectangle plate element.Second, procedure of stiffened plate structure's dynamic property using DEM is programed.Third, an new storage arithmetic of stiffness s matrix is provided.Fourth, this paper solves the frequency of stiffened plate structure, and compares the results with the ones acquired from FEM and ANSYS. The advantages that DEM needs less elements and can provide higher precision are revealed.Fifth, for plate element, using bubble function, starting with energy functional, a uniform DEM expression is deduced. This expression is more pithiness, more efficient.Last, this paper attempts to solve dynamic response with DEM. Get it from FEM and DEM, and compares the results.Via the analysis of plate, beam and stiffened plate structure's dynamic property adopting FEM and DEM, The advantages of DEM are revealed. With fewer elements, DEM can get equal precision to FEM. That is to say, when the amount of elements is equal, DEM has higer precision.