Research On Tubular Structure Damage Identifying Method By Using Piezoelectric Ultrasonic Waves

In the past 20 years,the tubular structure(round steel pipe,square steel pipe,etc.)has been rapidly developed at home and abroad,and widely used in modern industrial workshops,warehouses,gymnasiums,exhibition halls,meeting halls,terminals,stations,office buildings,hotels and other buildings.Because of its good performance,it is widely used at home and abroad.However,due to the impact of material transportation and human factors,the tubular structure will cause a variety of damage during transportation and installation.The existence of these defects poses a threat to the safety of the structure operation.The event of structural damage,accidents may occur and have serious effects on the economy and life as well as the surrounding environment.Therefore,it is very important to test the tubular structure before installation and after installation to determine whether it meets the requirements of safe operation.A new nondestructive testing method,ultrasonic guided wave detection using piezoelectric ceramics(PZT),has been developed and received much attention because of the shortcoming of the conventional method.Piezoelectric ceramic(PZT)is a kind of intelligent material with dual functions of sensing and driving,which is widely used in structural damage identification and health monitoring.In this paper,piezoelectric ceramic element is selected as the excitation and receiving device of the waveguide in the experimental study.This paper mainly conducts theoretical and experimental research in the following aspects:(1)In this paper summarizes the process and status quo of structural health detection using ultrasonic guided waves at home and abroad,and analyzes the development trend.The selection and development of the excitation elements of' the super-field guided wave are studied carefully,and the types and advantages of piezoelectric materials and the working principle of piezoelectric materials are analyzed.The physical and mechanical properties of piezoelectric ceramics were deeply studied,the driving mechanism of piezoelectric ceramics was analyzed,and the piezoelectric equation was introduced in detail.(2)Based on the previous research results,the propagation theory of guided waves in the tube is derived,and the dispersion equation of' circumferential guide wave and cylindrical guide wave is obtained.Three modes of guided waves in the pipe:longitudinal mode(L),torsional mode(T)and bending mode(F)are analyzed,and the displacement distribution of three modes in the pipe wall direction is obtained,in which the circumferential displacement of L mode is zero and the radial displacement of T mode is zero.(3)The experimental target and research scheme are determined.This paper mainly tests and studies the propagation characteristics of the guided wave in the steel tube under the initial stress of 0 and the loading of the steel tube and the analysis of the actual wave shape,providing theoretical and experimental basis for the selection of the healthy detection wave shape of the structural parts under the stress state in the actual engineering.Finally,the data model is analyzed by MATLAB to provide numerical theoretical basis for wave propagation in steel tube.It can be seen from the test results that before the initial stress is zero and the yield of the steel tube,the force and deformation of the components are linear,which has no influence on the mode of the guided wave.However,after the yield of the structure,the local deformation of the components increases,and the mode of the guided wave is affected at the same time.