Multi-Mode TFM Imaging with Artifacts Filtering Using CIVA UT Forwards Models

TFM (Total Focusing Method) is an advanced post-processing imaging algorithm of ultrasonic array data that shows great potential in defect detection and characterization. This technique can be performed using several propagation modes (direct or over skip imaging) and several types of waves (longitudinal or transverse) allowing the imaging of extended defects of complex geometry. However, non physical indications can be observed, leading to misinterpretation. These imaging artifacts are due to the coexistence of several contributions involving several mode of propagation and interactions with possible defects and / or the geometry of the part. In several configurations, a simple time of flight criterion is not sufficient for their identification. This paper presents tools based on the forward CIVA UT models which allow to analyze and to filter these artifacts, without any tuning parameters. The performances achieved are compared to those of conventional TFM on simulated and experimental data.