Study On Propagation Characteristics Of Ultrasonic Guided Waves In Arch Bridge Suspender

Suspender is widely used in bridge structure,which is mainly used to connect cable and deck system,whose role is to bear the load of the bridge deck system.Because the suspender is always sunder tension,and the working environment is very bad,once the surface of the PE sheath is damaged,it is very easy to lead to the internal broken wire and rust,which will bring about security risk.,Therefore,it is very important to detect the defects of suspenders in order to ensure the normal work of the suspender.Aiming at making health detection to suspender,the characteristic of guided wave propagation has been deeply studied,the finite element simulation model of an arch bridge has been established,the experiment platform for testing is set up,the dispersion and attenuation characteristics of guided waves in the Suspender are analyzed,and the related longitudinal and torsional wave transducers are designed.The detail work is presented as follows:Chapter 1 analyses the importance of non-destructive testing of suspender,and the main technology of non-destructive testing of suspender has been introduced,the research and development status of the suspender detection and guided wave technology has been presentedChapter 2 introduces the basic theory of ultrasonic guided waves,the propagation characteristics of guided waves are analyzed.Semi-analytical finite element method is used in calculating dispersion curves and dispersion attenuation curves of guided waves in suspender,STFT and 2DFFT are used to verify the correctness of the dispersion curve.Chapter 3 introduces the method to generate guided waves by using magnetostrictive effect,and transducers for longitudinal mode guided waves and torsional mode guided waves were designed.Chapter 4 establishes the finite element model of the suspender,the propagation of guided waves in a suspender is simulated.By analysis the simulated signals,the dispersion and attenuation characteristics of longitudinal mode guided waves are verified.The defect detection ability of torsional mode guided waves is simulated by defect detection.Chapter 5 builds a magnetostrictive guided waves' s detection system,by using the system,bias magnetic field on guided waves detection is analyzed,the defect detection ability of L(0,1)mode guided waves at different frequencies is studied.By comparing the results of experiment before and after using the magnetostrictive strip,it is verified that magnetostrictive strip has great benefit to signal improvement.Chapter 6 summarizes the main work of the thesis,lists the conclusion and prospect for further research.