Data Acquisition And Source Localization Technology Of Steel Bridge Crack Acoustic Emission Signal

The transportation industry is continuously evolving,and steel bridges are progressively becoming an fundamental element of modern urban transport construction,owing to their high strength,rigidity,and lightweight.However,due to factors such as heavy loads,corrosion,and vibration,cracks in steel bridges are inevitable and can lead to structural damage and failure if not detected in time,resulting in severe traffic accidents.Acoustic emission testing,as a form of non-destructive testing,can detect small cracks in steel bridges in real-time and quickly,providing an effective guarantee for the safe use of steel bridges.This paper analyzes the hardware and software requirements for crack detection based on the need for acoustic emission detection on steel bridges and designs an acoustic emission data acquisition system.Source localization function using the processed acoustic emission signal.The details of the study are as follows:1.An acoustic emission data acquisition system based on the DSP chip TMS320F28335 was designed.The system comprises a conditioning and amplification module(including voltage bias and amplification functions),an A/D conversion module,a DSP control module,and a LABVIEW host computer module.The system follows the subsequent workflow: the acoustic emission signal reaches the threshold voltage value and triggers the sampling,and the DSP control transmits the acquired acoustic emission signal data to the LABVIEW host computer program using serial communication.The system has a sampling resolution of 12 bits,a sampling frequency of 2MHz for both channels.2.The wavelet noise reduction method was used to reduce the noise of the collected acoustic emission signals.Considering the characteristics of the cracked acoustic emission signal of the steel bridge,the maximum and minimum threshold(which can retain the high-frequency part of the acoustic emission signal)and the soft threshold function(no distortion of the signal at the threshold point)were chosen as the wavelet thresholds in this paper.After comparing the root-mean-square error and signal-to-noise ratio of different wavelet bases,the 2-layer decomposition wavelet base of Sym5 is finally chosen as the optimal wavelet base.3.The propagation wave speed of the acoustic emission signal is determined.This paper uses a combination of theoretical calculations,COMSOL finite element simulations,and practical experimental methods to determine the propagation velocity of the acoustic emission signal in a steel plate(a simple steel bridge structure)to be 5000m/s.4.The local localization cracked steel plate acoustic emission signal source was carried out.This paper used the two-dimensional time difference localization method and the Geiger iterative algorithm to localize the acoustic emission source using the time difference obtained after wavelet noise reduction.The localization results show that both methods can be used to localize acoustic emission sources in the two-dimensional plane in steel bridges under the consideration of random errors and systematic errors.