Study On The Mobility Of Anisotropic Plate

Mobility,which is a useful tool for solving vibration and power problems of structures,reflects the velocity of the structure under external excitations.Nowadays,vibration and power problems of anisotropic structures appear in large numbers,but the study on mobility of these structures is not sufficient and the research on mobility of stiffened anisotropic plates,which are the basic elements in these structures,is not complete either.In this paper,theoretical and numerical analysis are presented to study the effect of material properties,boundary conditions and the stiffened beams on the structural mobility of an anisotropic plate.Firstly,some existing theories about mobility are reviewed.The wave equations of both isotropic and anisotropic plates are introduced,based on which the solution of point mobility and surface mobility of isotropic plate and the solution of point mobility of infinite orthotropic plate are deduced.Secondly,a finite element model is adopted to study the effect of excitational area,boundary conditions and the geometrical and material parameters of the plate on the mobility of an anisotropic plate.It indicated that both increasing excitatioal area and reducing Young's modulus can enlarge the difference between point mobility and surface mobility.Increasing the Young's modulus of an orthotropic plate can reduce more vibration of it than increasing its shear modulus.Increasing the size of the plate can reduce the fluctuation of the mobility.Changing boundary conditions can not effectively reduce the vibration of the plate.Finally,another finite element model is adopted to study the effect of the direction,location,cross-section and quantity of the stiffened beam on the mobility of a beam-stiffened anisotropic plate.It revealed that changing the direction of the stiffened beam can only slightly reduce the point mobility but may largely reduce the surface mobility and it depends a lot on the ratio of the Young's modulus of the plate in the direction of the stiffened beam to the Young's modulus of the beam.The farther away the region is from the beam-stiffened position,the less affected it is by the beam-stiffened effect.Increasing the height of the beam's cross-section can reduce more vibration of the plate than increasing the width.Comparing with a single stiffened beam,paralleled layout of two stiffened beams can further reduce the vibration transmission of the plate while crossed layout of two stiffened beams can only reduce surface mobility under high frequency excitations.This thesis can offer a good reference for the application of stiffened anisotropic plates and lay a solid foundation for further research on the vibrational performance of anisotropic plates.