Simulation on qualitative detection of defects with multi-mode total focusing method

摘要

Multi-mode total focusing method (TFM) is applied to overcome the limitation that defect type is difficult to be accurately determined with conventional ultrasonic testing. The phased array transducer connected with wedge is employed to implement electronic scan and receive the multiple reflected waves generated from defect surface. The signals are post-processed with delay-and-sum (DAS) beamforming algorithm to reconstruct images for the TTT case and obtain defect morphology for qualitative detection. The carbon steel models with 5.0 mm vertical crack and ?0.5 mm side-drilled holes (SDHs) having center-to-center spacing of 5.0 mm were detected with multi-mode TFM by simulation in this paper. The defect types were distinguished effectively from imaging results compared with conventional TFM, and the positioning and quantitative errors were no more than 8.4%. The multi-mode TFM is appropriate for the qualitative recognition of defects, especially for the cracks with gap.