Ultrasonic phased array phase coherence imaging of an austenitic stainless steel weldolet

Ultrasound detection and evaluation of defects in austenitic stainless steel weldolet showing structural signal is difficult because of the low flaw-to-grain noise ratio. In this paper, the technique of directivity correction phase coherence imaging (DC-PCI) is proposed to improve the signal-to-noise ratio (SNR). The technology combined with phase coherence imaging (PCI) and directivity correction factor which based on total focusing method (TFM). To verify the effectiveness of the technology, a new simulation model was proposed. The results show that the SNR of the DC-PCI method is improved by 19.01 compared with TFM. This experiment prepared two weldolet specimen with the same structure, the materials of 304 stainless steel and 20# steel, respectively. The full matrix capture (FMC) is acquired using a probe and post-processed using different imaging methods. The results show that for 304 stainless steel weldolet specimen, the SNR of PCI is improved by 4.66 dB on average compared with TFM, and the SNR of DC-PCI is improved by 12.79 dB on average compared with TFM. For 20# steel weldolet specimen, the SNR of the PCI is increased by an average of 5.16 dB compared with TFM, and the SNR of the DC-PCI is increased by an average of 12.62 dB compared with TFM.