CN-116008405-B - Rail fracture monitoring method based on multi-element coding ultrasonic guided wave technology

Abstract

The invention discloses a rail fracture monitoring method based on a multi-element coding ultrasonic guided wave technology, which comprises the steps of firstly forming a new multi-element coding sequence based on a traditional binary coding Barker code and a binary orthogonal complementary Golay code through series mathematical operation, modulating an ultrasonic guided wave monopulse excitation signal through the multi-element coding sequence to form a new coding excitation waveform, and monitoring rail fracture damage through the new coding excitation waveform. The multi-element coding in the multi-element coding excitation ultrasonic guided wave signal provided by the invention integrates the advantages of two basic coding methods, increases the flexibility of coding length, improves the signal-to-noise ratio gain and peak sidelobe level of the multi-element coding excitation ultrasonic guided wave signal, and improves the working efficiency of rail fracture monitoring.

Inventors

• YANG YUAN
• WANG PING
• JIA YINLIANG
• SHI YU

Assignees

• 南京航空航天大学

Dates

Publication Date

20260512

Application Date

20230113

Claims (8)

1. 1. A rail fracture monitoring method based on a multi-element coding ultrasonic guided wave technology is characterized by comprising the following steps: (1) The method comprises the steps of performing convolution operation on an A code sequence in a binary sequence Golay code and a binary sequence Barker code sequence to form a new multi-element code sequence, namely GA (m) _BK (n), and performing convolution operation on a B code sequence in the Golay code and the Barker code sequence to form a new multi-element code sequence, namely GB (m) _BK (n); (2) Performing convolution operation on the multi-element coding sequence GA (m) _BK (n) and the multi-element coding sequence GB (m) _BK (n) to form a new multi-element coding sequence, and marking the new multi-element coding sequence as GAB (m) _BK (n); (3) Modulating the waveform S (t) of the sine wave modulated by the Hanning window by binary coding sequences GA (m), GB (m) and BK (n), wherein the waveforms modulated by the binary coding sequences are respectively marked as GA_S (t), GB_S (t) and BK_S (t); (4) Modulating the waveform of the sine wave modulated by the hanning window by using a plurality of coding sequences GA (m) _BK (n) and GB (m) _BK (n), wherein the waveforms modulated by the binary coding sequences are respectively marked as GA_BK_S (t) and GB_BK_S (t); (5) Modulating the waveform S (t) of the sine wave modulated by the Hanning window by using a multi-element coding sequence GAB (m) _BK (n), and marking the waveform modulated by the multi-element coding sequence as GAB_BK_S (t), namely a multi-element coding excitation ultrasonic guided wave signal for monitoring rail fracture; (6) After the excitation Signal is boosted and amplified by a power amplifier, exciting a multi-element coding ultrasonic guided wave Signal by an ultrasonic transducer, after the excitation Signal passes through a steel rail medium, when the steel rail is broken and damaged, the multi-element coding ultrasonic guided wave is reflected by a damaged part Signal, an Echo Signal is received at the position of an excitation end of the multi-element coding ultrasonic guided wave and is marked as echo_signal (t), the Echo Signal is subjected to deconvolution operation with the GB (m) _BK (n) Signal in the step (1) to obtain an Echo Signal echo_GA_BK_signal (t), and the Echo Signal is subjected to deconvolution operation with the GA (m) _BK (n) Signal in the step (1) to obtain an Echo Signal echo_GB_BK_signal (t); (7) And respectively carrying out pulse compression on Echo signals echo_GA_BK_Signal (t) and echo_GB_BK_Signal (t) when the multi-element coding excitation ultrasonic guided wave Signal encounters rail fracture damage to respectively obtain echo_GA_BK_compression (t) and echo_GB_BK_compression (t), and then carrying out vector summation to obtain Echo signals echo_compression_Signal (t), wherein the Echo signals are returned when the multi-element coding excitation ultrasonic guided wave monitors the rail fracture damage.
2. 2. The method for monitoring the fracture of the steel rail based on the multi-element coding ultrasonic guided wave technology according to claim 1, wherein the calculation formulas of the multi-element sequences GA (m) _BK (n) and GB (m) _BK (n) in the step (1) are as follows: GA(m)_BK(n)=GA(m)*BK(n) GB(m)_BK(n)=GB(m)*BK(n) where, is the convolution operation symbol.
3. 3. The method for monitoring the fracture of the steel rail based on the multi-element coding ultrasonic guided wave technology according to claim 1, wherein the calculation formula of the multi-element sequence GAB (m) _bk (n) in the step (2) is as follows: GAB(m)_BK(n)=GA(m)_BK(n)*GB(m)_BK(n) where, is the convolution operation symbol.
4. 4. The method for monitoring the rail breakage based on the multi-element coded ultrasonic guided wave technology according to claim 1, wherein the calculation formulas of waveforms ga_s (t), gb_s (t) and bk_s (t) modulated by the binary coding sequence in the step (3) are as follows: GA_S(t)=GA(m)·S(t) GB_S(t)=GB(m)·S(t) BK_S(t)=BK(n)·S(t) The calculation formula S (t) of the hanning window modulated sine wave is: Where, f is the center frequency of the hanning window modulated sine wave, N T is the number of cycles of the hanning window modulated sine wave, t is the hanning window modulated sine wave duration, and a is the amplitude of the hanning window modulated sine wave.
5. 5. The method for monitoring the fracture of the steel rail based on the multi-element coding ultrasonic guided wave technology according to claim 1, wherein the calculation formulas of waveforms ga_bk_s (t) and gb_bk_s (t) modulated by the multi-element coding sequence in the step (4) are as follows: GA_BK_S(t)=GA(m)_BK(n)·S(t) GB_BK_S(t)=GB(m)_BK(n)·S(t) Where, is the product operation symbol, the S (t) Hanning window modulates the waveform of the sine wave.
6. 6. The method for monitoring the fracture of the steel rail based on the multi-element encoding ultrasonic guided wave technology as claimed in claim 1, wherein the calculation formula of the multi-element encoding excitation ultrasonic guided wave monitoring steel rail signal gab_bk_s (t) in the step (5) is as follows: GAB_BK_S(t)=GAB(m)_BK(n)·S(t) where, is the sign of the product, the S (t) Hanning window modulates the waveform of the sine wave.
7. 7. The method for monitoring rail breakage based on the multi-element coded ultrasonic guided wave technology as claimed in claim 1, wherein the step (6) is realized by the following formula: Echo_signa((t)=h(x)·GAB_BK_S(t) Echo_GA_BK_Signal(t)=h(x)·GAB_BK_S(t)* -1 GB(m)_BK(n) Echo_GB_BK_Signal(t)=h(x)·GAB_BK_S(t)* -1 GA(m)_BK(n) Where, is the product operation sign, -1 is the deconvolution operation sign, and h (x) is the medium transfer function record.
8. 8. The method for monitoring the rail breakage based on the multi-element coded ultrasonic guided wave technology according to claim 1, wherein the calculation formulas of echo_ga_bk_compression (t), echo_gb_bk_compression (t) and echo_compression_signal (t) in the step (7) are as follows: Echo_GA_BK_Cmopress(t)=Echo_GA_BK_signal(t)*GA_BK_S(-t) Echo_GB_BK_CmopRess(t)=Echo_GB_BK_signal(t)*GB_BK_S(-t) Echo_Compress_Signal(t)=Echo_GA_BK_Cmo0Ress(t)+Echo_GB_BK_CmopRess(t) where, is a convolution operation symbol, ga_bk_s (-t) and gb_bk_s (-t) are mirror signal waveforms of ga_bk_s (t) and gb_bk_s (t) about the y-axis, respectively.

Description

Rail fracture monitoring method based on multi-element coding ultrasonic guided wave technology Technical Field The invention belongs to the technical field of nondestructive testing, and particularly relates to a rail fracture monitoring method based on a multi-element coding ultrasonic guided wave technology. Background Nondestructive testing is an emerging discipline for evaluating structural anomalies and defects, i.e., whether or not there are cracks, inclusions, etc., in the internal structure, physical properties, or state of a workpiece, material, etc., to be inspected without damaging them, by utilizing changes in thermal, acoustic, electrical, optical, magnetic, etc. reactions caused by the presence of anomalies and defects in the internal structure of the material. Ultrasonic guided wave is generated by repeated reflection of ultrasonic waves at boundaries when the ultrasonic waves are confined to the boundaries of a waveguide medium such as a rod or tube, and ultrasonic guided wave monitoring provides relatively lower monitoring frequencies and longer transmission and monitoring distances than ultrasonic waves. Ultrasonic guided wave technology is widely used in rail and pipeline structure health monitoring at present. In the structural health monitoring technology based on the ultrasonic guided wave technology, the excitation energy of signals is enhanced, the monitoring distance and the resolution are improved, and the qualitative and quantitative evaluation of damage is one of key technologies for nondestructive structural health monitoring. A common measure is to increase the emission voltage, but this complicates the hardware circuitry and requires a high withstand voltage for the ultrasound transducer. The coding compression technology can indirectly improve the transmitting energy by transmitting a plurality of continuous waves on the premise of the existing circuit and the withstand voltage value of the ultrasonic transducer, and the receiving end can realize the aggregation of the energy of the received signals by continuously receiving the signals and by the pulse compression technology. Many scholars have conducted intensive research on coding compression methods, but some researchers have studied the combination of the coding compression method and the coding compression method, so that the signal-to-noise ratio and peak sidelobe level are improved, and the compression combination can still be realized only by carrying out coding and decoding twice, and some scholars have focused on how coding and decoding once are realized by coding and decoding GolayA codes and GolayB codes twice, but compared with the prior art, coding and decoding GolayA codes and GolayB codes twice are needed, the coding and decoding efficiency is only improved, and the signal-to-noise ratio and the peak sidelobe level are not improved. Disclosure of Invention The invention aims to provide a rail fracture monitoring method based on a multi-element coding ultrasonic guided wave technology, which improves the energy of the whole rail fracture monitoring system and is beneficial to improving the signal-to-noise ratio of echo signals. The invention provides a rail fracture monitoring method based on a multi-element coding ultrasonic guided wave technology, which comprises the following steps: (1) The method comprises the steps of performing convolution operation on an A code sequence in a binary sequence Golay code and a binary sequence Barker code sequence to form a new multi-element code sequence, namely GA (m) _BK (n), and performing convolution operation on a B code sequence in the Golay code and the Barker code sequence to form a new multi-element code sequence, namely GB (m) _BK (n); (2) Performing convolution operation on the multi-element coding sequence GA (m) _BK (n) and the multi-element coding sequence GB (m) _BK (n) to form a new multi-element coding sequence, and marking the new multi-element coding sequence as GAB (m) _BK (n); (3) Modulating the waveform S (t) of the sine wave modulated by the Hanning window by binary coding sequences GA (m), GB (m) and BK (n), wherein the waveforms modulated by the binary coding sequences are respectively marked as GA_S (t), GB_S (t) and BK_S (t); (4) Modulating the waveform of the sine wave modulated by the hanning window by using a plurality of coding sequences GA (m) _BK (n) and GB (m) _BK (n), wherein the waveforms modulated by the binary coding sequences are respectively marked as GA_BK_S (t) and GB_BK_S (t); (5) Modulating the waveform S (t) of the sine wave modulated by the Hanning window by using a multi-element coding sequence GAB (m) _BK (n), and marking the waveform modulated by the multi-element coding sequence as GAB_BK_S (t), namely a multi-element coding excitation ultrasonic guided wave signal for monitoring rail fracture; (6) After the excitation Signal is boosted and amplified by a power amplifier, exciting a multi-element coding ultrasonic guided w