Research And Design Of Rail Structural Health Monitoring System Based On Piezoelectric Ultrasound Guided Wave

Effective monitoring of the rail structure is important to ensure the serviceability and the safety of the rail.Based on the actual demands,this paper uses the ultrasonic guided wave detection method to study and design the rail structure health monitoring system.The main contents of this paper are as follows:(1)This paper takes rail damage monitoring as the research object,researches deeply on the schemes of previous scholars,and puts forward some improvements and proposes the requirements,performance,parameter indexes and realization scheme of the being designed system,selects ultrasonic guided wave method for rail damage detection,puts forward the requirement and realization scheme of the system.Then,the system is developed of child modules taking the design concepts of high performance and low power consumption into account.A circuit which takes JN5148 as a main control chip and wireless transmission chip with functions such as conditioning,display and storage is devised.The piezoelectric ceramic plate ultrasonic probes are selected to monitor the state of the rail structure.Simultaneously,Zigbee wireless transmission technology is adopted to realize wireless transmission of data,and the circuits of each node of wireless transmission system are designed.The hardware and software design on the detector,end device,router and coordinator were detailed and conducted in this paper.(2)In order to solve the measurement difficulties in damage detection caused by the dispersion of ultrasonic guided waves in complex rail structures,the propagation characteristics of guided wave at rail waist are analyzed from the aspects of guided wave mode number,mode aliasing and system crosstalk by theoretical analysis and finite element simulation,and the appropriate monitoring frequency and propagation distance were selected.Experiments show that the guided wave response signal at rail waist is easy to extract features under the excitation frequency and propagation distance,and is less affected by modal aliasing and crosstalk.(3)According to the propagation characteristics of ultrasonic guided waves with different propagation distances at different excitation frequencies in rail waist,a sensor array suitable for rail waist damage monitoring is designed,and the excitation frequencies of monitoring signals are determined.Combined with time reversal theory,a scattering signal enhancement and damage localization method based on time reversal principle is proposed.Starting from the idea of superimposing and amplifying the damage scattering signal,the method enhances and amplifies the damage scattering signal by time reversal focusing,and improves the signal-to-noise ratio.The method is validated by finite element simulation analysis and experimental results and the results show that the method can effectively improve the energy of damage scattering signal,and the positioning error of the rail waist damage is less than 5%.