Research On Ultrasonic Guided Wave Damage Detection Based On Steel Rod Spectral Element

The bridge is an important infrastructure related to national economy and people’s livelihood.For existing and newly built bridges,in order to discover and deal with structural diseases in a timely manner,reduce losses,and protect the lives and property safety of the people,it has become a very real time to effectively detect,monitor,and evaluate the health status of service structures.Urgent task.In the field of detection and monitoring,traditional steel component detection or monitoring methods have low efficiency and cannot meet the needs of large-scale,real-time and efficient monitoring and detection.In view of the increasingly urgent practical needs,this article mainly studies steel rods based on ultrasonic guided waves The main research work and results of the damage detection method are as follows:(1)The dispersion characteristics of ultrasonic guided waves propagating in steel rods are discussed.Aiming at the situation that the frequency equation of each mode belongs to the transcendental equation and cannot obtain an accurate analytical solution,the frequency equation of each mode is solved in MATLAB by numerical methods,the dispersion curves of the phase velocity and the group velocity are drawn,and the poise is further studied.The effect of the loose ratio and diameter on the speed of the guided wave propagating in the steel rod.(2)The spectral element method was used to simulate the propagation of guided waves in healthy rods and damaged rods,and the influence of the damage on the propagation of guided waves was obtained.Five-cycle sinusoidal pulse signal modulated by Hanning window is selected as the excitation signal.Compared with the healthy rod,the damaged rod receives more signals reflected by the touch damage in the acceleration response,and the rod is further studied.The influence of diameter,damage depth,damage location and rod length on the propagation of guided waves in the rod.(3)Based on the virtual instrument(VI)developed by NI on the virtual instrument platform LABVIEW,it cooperates with the multifunctional data acquisition equipment to realize the generation of excitation signals and the reception of sensor signals,and the appropriate type of piezoelectric sheet is selected as the actuator and sensor.After selecting the appropriate sampling frequency and signal filter,the waveform of the guided wave passing through the defective steel rod is obtained;according to the spectrum diagram of the waveform,it can be seen that the center frequency of the guided wave after the defective steel rod remains unchanged Change;comparing the actual group velocity of guided wave propagation with the theoretical group velocity of the steel rod dispersion equation,we can find that the theoretically calculated group velocity can be used for the actual guided wave propagation velocity;After the group velocity,the damage location and actual damage location are estimated based on the time of the wave packet reflected from the defect in the received signal,and the results verify the effectiveness of using guided waves to detect defects in the steel rod.