Research on TFM Imaging of Main Pipe Weld of Compound Steel Based on FMC/SMC

摘要

Main pipe weld of compound steel with welding layer of coarse-grained austenitic stainless steel leads to the reduction of image resolution and signal-to-noise ratio (SNR) using phased array ultrasonic testing (PAUT). Total focusing method (TFM) can be employed to improve imaging quality, but computational efficiency is influenced significantly by element number. It is very important to balance quality and efficiency of TFM imaging by reasonably choosing array element. Focusing on 75 mm thickness main pipe weld of compound steel having a Φ2 mm side-drilled hole in 65 mm, the TFM imaging were compared with data acquisition modes of full matrix capture (FMC) and sparse matrix capture (SMC). The results showed that, with the increasement of element number, the quality of TFM images were both improved. When the element number was 8, compared with FMC-TFM image, the array performance indicator (API) of SMC-TFM image decreased 20% and SNR differed by 0.75dB, while API and SNR were almost the same with 48 elements. The detection result was up to element number and location, so SMC could be utilized to ensure imaging quality and improve computational efficiency in practical inspection.