Research On Broken Rail Monitoring System Of Heavy Haul Railway Based On Ultrasonic Guided Wave

The annual growth of heavy haul railway transportation in China puts forward higher requirements for the health monitoring of railway line infrastructure,and the on-line monitoring of track fracture is one of the important measures to ensure the safe operation of heavy haul railway lines.When ultrasonic guided wave propagates in the rail,it can cover the whole cross section of the rail,with fast propagation speed and long propagation distance.Using ultrasonic guided wave detection technology for long-distance rail breaking monitoring can detect the complete fracture and incomplete fracture of the rail in time.According to the demand of long-distance rail breaking on-line monitoring of heavy haul railway in China,based on ultrasonic guided wave detection technology,this paper designs a real-time rail breaking monitoring system for the jointless track of heavy haul railway,which can monitor the rail breaking of heavy haul railway all-weather online.The main research work of this paper includes:Based on the Semi Analytical Finite Element(SAFE)theory,firstly,the dispersion curve and modal vibration modes of ultrasonic guided wave in U78 Cr V(one of the common rail material of heavy haul railway in China)heavy rail are solved,and then the guided wave mode suitable for rail full section detection and the excitation way of the selected mode are selected according to the vibration characteristics of each mode.Finally,according to the excitation way,through the three-dimensional finite element simulation of ANSYS,the mode is preliminarily verified from the two aspects of the group velocity and the phase velocity by using FFT and the wavelet transform,and the similarity between the rail section and the guided wave mode shape is compared to verify that the excitation way determined in this paper can excite the selected mode.The broken rail monitoring equipment is designed,and the ultrasonic guided wave excitation circuit and receiving circuit are integrated into one equipment.The equipment takes STM32 and FPGA as the core control unit,and the FPGA drives the DA module and the AD module to complete the excitation and acquisition of ultrasonic signals respectively.STM32 receives the ultrasonic guided wave signal from the internal FIFO of FPGA,analyzes and processes the signal,and drives the display screen to display the equipment status and rail status in real time.Finally,STM32 interacts with the computer acquisition system through the 4G module.According to the system requirements,combined with the hardware system designed in this paper,the design of embedded software system and the computer acquisition system is completed,and the expected function of the system is realized.The embedded software system includes the program design of FPGA and STM32,and the computer acquisition system includes the design of the human-computer interaction interface and the source code,and the development software is Visual Studio.For the broken rail monitoring system designed in this paper,the performance of the equipment and the overall function of the system are comprehensively tested in the rail of track and railway site respectively.The test results show that the rail breaking monitoring system designed in this paper has met the expected requirements.Finally,according to the excitation way proposed in the paper,the attenuation test is carried out on the ring railway test line.The test shows that the excitation way and guided wave mode selected in the paper are suitable for the long-distance track breaking monitoring of heavy haul railway in China.