Research On Key Problem Of Ultrasonic On-machine Thickness Measurement System

Thin-walled parts have the characteristics of light weight and strong load-bearing capacity,and are more and more favored by factories and enterprises in the manufacturing industry.When thin-walled parts are used in high-precision fields such as aerospace,the machining accuracy of the parts will be strictly required to ensure the machining quality of the parts.In ensuring the quality of parts processing,thickness is an important indicator for testing whether thin-walled parts are qualified.In factories,manual hand-held thickness gauges are usually used for thickness measurement.At this time,not only labor costs are added,but also the processing of parts is reduced.Efficiency is not conducive to the assembly line operation of the product.At this time,it is very necessary to have a thickness measurement device for the on-machine inspection of parts.Combining the advantages of ultrasonic thickness measurement,the development of a tool holder-type on-machine ultrasonic thickness measurement device has become a guarantee for the quality inspection of thin-walled parts.However,due to the size and power consumption requirements of the device,the difficulty of device development is increased.Among them,ensuring that the excitation of the transducer is in the best working state and the high-precision extraction of the thickness of the echo information have become two of the research Important key issues.This article is an in-depth study of these two key issues,and finally improves the thickness measurement performance of the device.The main contents are as follows:(1)The principle of ultrasound propagation and the propagation of ultrasound in multi-layer media are studied,and the principle of thickness measurement of ultrasonic pulse reflection method is explained in detail,which lays a theoretical foundation for the research of on-machine ultrasonic thickness measurement devices.Then,the functions of each module are explained in terms of the hardware and software of the ultrasonic thickness measurement device,and two key problems in the on-machine ultrasonic thickness measurement device are revealed.One is the study of transducer excitation mode,and the other is the study of high-precision extraction of thickness information in ultrasonic echo.(2)For the first key issue,in the current tool holder-type on-machine ultrasonic thickness measurement device,there is the problem of ultrasonic instability.Therefore,combining with the theory of ultrasound and focusing on the needs of the subject,first the type of ultrasonic pulse wave is selected,then the appropriate transducer excitation pulse is selected,then the type of pulse signal generation circuit is selected,and the component parameters is determined in the pulse excitation circuit,finally the circuit design of pulse excitation is completed in ultrasonic transmission.(3)For the second key issue,due to the low measurement accuracy of the current on-machine ultrasonic thickness measurement device,the different advantages of FGPA and computer are used to realize the ultrasonic thickness measurement process step by step.First the reception of the ultrasonic echo signal is realized in the FPGA master control device,and then the data is sent to the computer,and due to the flexibility of the computer PC operating system,the data fitting can be completed in the Qt5 software,finally the high-precision extraction of the thickness information in the echo signal is studied achieve.