Development Of Steel Plate Thickness Measurement System Based On Electromagnetic Ultrasound

With the continuous development of the world economy,the demand for sheet metal is also growing.In the production process of plates,the thickness is an important production index.The need for continuous monitoring of the production line produced by the thickness of the plate is in line with the requirements.Once the monitored thickness deviates from the standard value,it needs to modify the parameters of production equipments in a timely manner,and the high-quality and high index of metal sheet is produced ultimately.In the use of metal plates,it is very important to monitor the thickness of the sheet in real time due to the existence of constant impact,extrusion,friction,natural aging and other reasons.It can not only prolong the service life of the equipment,but also reduce the threat of production safety.Electromagnetic ultrasonic testing technology has the advantages of non-contact,no coupling agent,suitable for high temperature and other complex environmental testing,and it has been widely used in industrial practice gradually.Therefore,the electromagnetic ultrasonic plate thickness measurement system is studied,to complete the precise measurement of plate thickness is of great significance.Aiming at the problem of electromagnetic ultrasonic thickness measurement in this paper,the basic principle of electromagnetic ultrasonic testing technology and electromagnetic ultrasonic transducer is studied.The mathematical model of the ultrasonic transducer is deduced by the Lorentz force and the hysteresis telescopic mechanism in exciting the ultrasound process.The corresponding boundary conditions are given.The basic principle of electromagnetic ultrasonic thickness measurement is analyzed,the electromagnetic ultrasonic thickness measurement formula is deduced,the propagation velocity of shear wave and longitudinal wave in solid is studied,and the electromagnetic ultrasonic transducer is designed to stimulate the shear wave.According to the electromagnetic ultrasonic thickness measurement of high power,high voltage,high frequency pulse demand,the hardware of electromagnetic ultrasonic thickness measurement is designed,aiming at characteristics of electromagnetic ultrasonic thickness echo signal,the receiving hardware electromagnetic ultrasonic thickness is designed,.the circuit is simulated by virtual electronic laboratory simulation software to verify the correctness of the circuit design.Influence of line spacing and excitation frequency on thickness echo signal is studied.Build experimental platform to obtain multiple sets of thickness measurement echo signal,the empirical mode decomposition algorithm is used to process the echo signals of different thickness aluminum plates,it can remove noise to improve signal to noise ratio,calculate the thickness value by using the parabolic interpolation method to extract the adjacent peak corresponding time difference,the errors are compared and analyzed.Experiments were carried out on aluminum plates of different thickness,the experimental results show that the designed ultrasonic thickness measurement circuit and the receiving circuit can meet the requirements of the thickness measurement system.Although the original thickness measurement signal is more obvious,but the echo signal noise is large,especially the excitation pulse is more messy,and it also has a strong impact on subsequent echoes resulting in the first two echo waveforms are not on the same horizontal line,it seriously affects the measurement accuracy.After the empirical mode decomposition algorithm deals with the signal,the echo signal noise is small,the excitation pulse is clear boundaries,all echoes are on the same level,the signal line is shallow,visibility is improved.Parabolic interpolation method can accurately extract the echo peak point information and accurate extraction of adjacent peak points corresponding to the time difference to improve the thickness measurement accuracy.The combination of EMD algorithm and parabolic interpolation method provides a reference for the field of data processing of electromagnetic ultrasonic nondestructive testing.