Research On On-site Ultrasonic Thickness Measurement Technology Based On Dry Coupling

For the rapid and high-precision measurement of the thickness of large parts(especially large thin-walled parts),the traditional thickness measurement technology represented by three coordinates can ensure the thickness measurement efficiency and accuracy,but there are shortcomings such as secondary clamping error,time-consuming and labor-consuming.The technology of on-site ultrasonic thickness measurement based on dry coupling can solve the above problems,so it is necessary to study it.The research content of this paper is as follows:The first chapter is the introduction,which mainly describes the research background and significance of this paper,as well as the research status of ultrasonic thickness measurement at home and abroad,and discusses the research content of this paper.In the second chapter,the algorithm of ultrasonic thickness measurement is studied.Firstly,the simulation model of echo waveform is established,then the wavelet threshold method is used to denoise the echo waveform,the envelope signal is extracted based on Hilbert transform,then the envelope feature is extracted by autocorrelation operation,and finally the peak value recognition and thickness calculation are carried out for the autocorrelation signal.In the third chapter,on the basis of the analysis of the dry coupled ultrasonic echo,the hardware systems such as the knife handle clamping mechanism,the dry coupled probe mechanism,the ultrasonic excitation circuit,the ultrasonic echo conditioning and sampling circuit are designed respectively,and the hardware circuits are integrated in the knife handle clamping mechanism to realize the wireless transmission of on-site thickness measurement and measurement data.In the fourth chapter,the software system of on-site ultrasonic thickness measurement based on dry coupling is designed,including the lower computer and upper computer program mainly based on FPGA and STM32,and the five modules of measurement control,parameter control,accuracy calibration,waveform display and thickness calculation of upper computer software are described.In the fifth chapter,the calibration experiment and thickness measurement experiment are carried out for the parts with different materials and thickness,and the experimental results are compared with the calibration experiment and error source analysis.The experimental results show that the thickness measurement accuracy and real-time performance of the system meet the actual requirements.The sixth chapter summarizes the whole work and discusses the direction of further research.