Research On Wheel Internal Defect Detection Technology Based On Laser Ultrasound

At present,high-speed trains have gradually become the core technical equipment of China's intercity rail transit.In order to meet the operational requirements of large passenger capacity,rapid boarding and landing,and quick start and quick stop,it is essential to conduct safety inspections on their parts and components.Wheels are an important component of high-speed rail vehicles,Therefore,this paper aims at the defect detection technical requirements of high-speed rail wheels at a speed of 400 kilometers per hour,and uses laser ultrasonic detection technology to study the detection of 0.5mm-level internal defects.Firstly,the theory of laser thermoelastic excitation ultrasonic wave is summarized.Combined with the characteristics of laser thermoelastic effect,the theory of laser thermoelastic effect ultrasonic wave is sorted out and deduced.Secondly,the two methods of laser ultrasonic testing and piezoelectric wafer excited ultrasonic testing were simulated using COMSOL finite element simulation software.Through the analysis of the numerical simulation of laser ultrasound,the distribution of the temperature field and stress field inside the material during laser excitation,as well as the propagation process of ultrasound inside the material and the changes in sound pressure at various points,etc.are obtained;The analysis of the numerical simulation results in the propagation of ultrasonic waves within the specimen and the change curve of the sound pressure signal.At the same time,through-hole defects of different sizes were added to the simulation models of the two detection methods of laser ultrasound and piezoelectric ultrasound respectively.It is expected that the size and position of the defects will be determined by analyzing the changes in the sound pressure signal.Then by comparing the numerical simulation results of the above two detection methods,the advantages and disadvantages of the two methods in detecting small defects and the main factors affecting the detection of small defects are analyzed.The results show that the laser absorption rate of the material,the ultrasonic The nature of propagation and the reception and processing of ultrasound signals are the main factors that affect the assessment of defects.Finally,this paper uses the AOS advanced ultrasonic phased array full focus imaging platform,and uses the TFM imaging algorithm to test the defects of different sizes on the defect sample,and analyzes the echo signal.The correctness of the simulation work was verified through experiments.At the same time,it was verified that the use of advanced ultrasonic phased array all-focus imaging platform can realize the detection of 0.5mm through hole defects,and within a certain error range,the location of the defects can be located.