Research on weld ultrasonic testing based on frequency-phase coded excitation

Weld is widely used in the industry, especially in the complicated structure. High time resolution is needed to measure the position and size of flaw in the weld more accurately. Coded excitation and pulse compression in radar field has been introduced into weld ultrasonic testing to improve the time resolution. Amplitude weighted frequency-phase coded excitation is proposed to obtain good testing results with higher time resolution and lower sidelobe. The proposed excitation signal combines amplitude weighted linear frequency modulation signal and Barker code. compared with LFM, Barker and conventional brief pulse excitation, the results of simulations and experiments demonstrate that, time resolution of the proposed excitation is higher with the same chirp bandwidth and the chirp bandwidth has less impact on the proposed excitation.