Analysis Of Guided Wave Propagation In Layered Structures

With the continuous development of technology,the types of composite materials and their composition also show a variety of ways.The layered material structure can be superimposed on each layer of material of different properties,so that it can obtain special properties to meet the requirements of different materials under different conditions.While it can be designed by the user,resulting in its wider scope of application.Because of its wide usability,it's very important to detect and diagnose the material structure during its service,and has become the focus of the present research.Ultrasonic guided wave detection,as a branch of non-destructive examination method,has the advantage of low attenuation and far propagation distance,and has become a new and frontier research field in the field of international non-destructive examination.The research of China on this aspect started late,both in theoretical research and detection equipment development are lagging behind the world's advanced developed countries.On the basis of previous studies,the propagation characteristics of layered plate and cylinder are studied by different methods.The main contents are as follows:(1)The dispersion characteristics of the guided wave propagation in the layered plate are obtained by using strip element method.The influence of the change of the pavement angle on the dispersion characteristics in the plate is analyzed by numerical example.Then,the dispersion characteristics of single layer fiber fracture and multilayer fiber fracture are studied,and the influence of different conditions on the dispersion characteristics is analyzed.(2)On the basis of the three equations of mechanics,the dispersion equation in the single-layer isotropic cylinder is obtained by introducing the potential function and using the Bessel series.Based on this equation,the equation in the multilayered isotropic cylinder is obtained by using transfer matrix method.Finally,numerical results are used to verify the correctness of the method,and the dispersion characteristics of single layer cylinder and single layer plate,single layer cylinder andmultilayer cylinder are compared.(3)The propagation characteristics of the guided wave in the anisotropic layered cylinder is studied by using the state space method,and the dispersion equation is obtained.In this paper,the correctness of this method is verified by solving the dispersion curves of isotropic material and anisotropic material.Finally,the effect of fiber reinforcement on the dispersion characteristics of the composites under different magnification is studied.At the same time,the Bessel series method is compared with the state space method.(4)Based on the third chapter,the problem of response in the cylinder is deduced by using the formation superposition method.In this paper,the dispersion equation in the layered cylinder and the layered plate is deduced by different methods.The dispersion characteristics of different materials under different shapes are analyzed by numerical examples.Through these theoretical studies,it's expected to provide a theoretical reference for non-destructive examination techniques.