The System and Method of Ultrasonic Testing Based on Linear-Frequency-Modulation Technique

摘要

In the traditional ultrasonic testing, there is a conflict between the propagation distance and the time resolution. Aiming to solve the problem, a real-time ultrasonic testing system is developed based on linear-frequency-modulation (LFM) technique. The system is smaller in size, compared with the system which is composed of waveform generator and so on. Since the system is open, it can be easily updated according to requirements. The signal generation part is based on direct-digital-synthesizer technique and the signal processing part is based on pulse-compression technique. There are dual channels for data acquisition, one for the echo and another one for the reference signal. Therefore, the coefficient of the matched filter is variable. Ultrasonic time-of-flight-diffraction (TOFD) testing the system is accomplished, and the distance resolution and the signal-to-noise ratio are better than the conventional pulse-echo system. And the flaws in the test sample can be detected by the system.