Study Of Key Technologies On Ultrasonic Flaw For Big-caliber Steel Tube

Ultrasonic testing is one of the important technologies of nondestructive examination whose carrier implementation is ultrasonic testing instrument Ultrasonic testing instrument has been studied for many years. With the development of computer technology, Ultrasonic testing instrument becomes more and more automatic whose testing range becomes more and more wide, testing depth becomes more and more deep, sampling rate becomes more and more rapid and flaw orientation becomes more and more accurate. Based on ultrasonic pulse echo theory, this article introduces a multichannel automatic testing system used for big-caliber steel tube.The following are main achievements of this thesis:In this thesis, a three-channel automatic testing board is designed used for big-caliber steel tube in order to improve testing speed. Furthermore, this board can be flexible to build all kinds of multichannel testing device to meet the need of different complicated tests.A digital signal processing module is designed based on FPGA whose system clock is 100MHz. The module includes a parameter register circuit for initialization, a narrow pulse occurring circuit with adjustable pulse length, a data acquisition delay circuit and a data acquisition circuit. In addition, recurring to high frequency of FPGA, a high speed FIFO block is designed to get over the restrict of exterior RAM's read and write which improves the system data acquisition frequency more.Parts of the software of ultrasonic testing system for big-caliber steel tube is written which provides human-machine interactive interface, the echo pulse's wave display, standard DAC curve's fitting and the communication between the master and the slave.A USB interface circuit is designed for the data transfered between the master and the slave. The echo signal is composed and processed later to be integrated .