Research On Propagation Of Guided Waves In Typical Steel Structures And Its Application For Damage Detection

In recent years,more and more significant accidents are caused by the damage of the engineering structure,so more and more people pay attention to the engineering structure damage detection and prevention.In many engineering environment,it is required to realize the real time and active surveillance of the structure in service.Based on ultrasonic guided wave damage detection technique has the advantages of online,real-time,nondestructive testing testing,etc.,which is commonly used detection technology in the detection of engineering structures and very mature in thin plates and simple structures.Based on the damage detection of ultrasonic guided wave technology because of its advantages,such as online,real-time,nondestructive testing,is now commonly used in engineering structure detection detection technology,detection of its simple structure and so on in the sheet is already very mature.The most of engineering structures are complex,such as structural steel.So it is very important to study the propagation characteristics of guided waves and damage detection in steel structure.This paper firstly reviewed the domestic and foreign research present situation of structural health monitoring technology,focused on an overview of structural health monitoring technology,the basic theory of guided wave,the interaction between guided wave and damage,excitation and reception of the signals,the common signal processing methods,and guided wave testing technique in damage identification and location method etc..Based on the basic theory of elastic wave,studying the guide wave propagation on the solid-liquid interface and calculate the guided wave dispersion equation of the infinite free plate and thin tube structures.Using the numerical method and MATLAB software,plotted the corresponding guided wave dispersion curves.At the same time,research based on the ABAQUS platform finite element simulation method,the choice of the simulation parameters of the mesh and step in the finite element simulation was summarized,and the structure damage and load simulation modeling was also studied.In addition,the composition of the detection system was introduced in this study.According to the shape similar principles and referring to the guided wave of the infinite thin plate,studied the guided wave propagation mechanism in the H-shape steel.And in the choice of excitation signal,thinking about the impacts of the multimode characteristics of guided waves,dispersion characteristics,the intensity of response wave,excitation signal cycles and other factors on guided wave propagation in H-shape steel.In determining the excitation signal on the basis of the analysis of guided wave propagation between excited at points and whole around and the influence of the differenct thickness of the web plate on the guided wave propagation.According to the antisymmetric mode of Lamb wave has strong sensitivity on the initial damage and micro damage detection,and the symmetry mode of Lamb wave has the advantages of small attenuation,long distance and so on.Therefore,using the method of antisymmetric mode of Lamb wave to study the ability of damage identification,using the method of symmetric mode of Lamb wave to study the localization of long distance damage.The damage localization in the H-shape steel,using the "six point and different time method",not only can realize the axial localization on the damage in H-shape steel,but also complete the circumferential localization of damage.According to the basic theory of the guided wave in infinite pipes,studied the guided wave propagation mechanism and damage localization in the fluid pipeline.Based on decreasing the guide wave mode and other factors to select the appropriate excitation signals.Select single-point excitation and multi-point received detection network in finite element simulation and experimental research.This paper considers the effect of the fluid in pipeline on guided wave propagation in the pipeline,studied the guided wave propagation mechanism and damage localization in the fluid pipeline.And for the damage localization in the fuild pipeline,the elliptical localization method was used,which can complete axial and circumferential localization of damage,but the location accuracy of circumferential is much less than the axial.In this paper,the research methods and conclusions of damage localization in Hshape steel and fuild pipeline have important reference significance to the study of the similar structures.