The corresponding theoretical SDH AIM is shown in Figure 6 (b). 30º and 70º steering angle guidelines (from the midpoint of the active aperture) were added. A schematic diagram of this coordinate system is shown in Figure 1.įigure 6: (a) Empirical SDH amplitude map and (b) theoretical SDH AIM for pulse-echo TT mode. The second validation experiment was conducted on a test block that contains FBHs, which simulate the scattering response of directional flaws.įor the results presented in this paper, the x-axis is defined positive to the right of the first transducer element, and the z-axis is defined positive below the surface of the test sample. The first validation experiment was conducted on a test block that contains small-diameter side-drilled holes (SDHs), which simulate the scattering response of nondirectional flaw scatterers. Results obtained from two validation experiments are presented in this section. To examine the acoustic model’s accuracy, we conducted validation experiments to compare experimentally obtained TFM amplitude maps with a theoretically calculated TFM AIM. įigure 5: The composite amplitude lines of SDHs present in the NAVSHIPS test block. In addition, by calculating and applying the time of flights of multiple acoustic modes, multi-mode TFM that can provide additional information about the specimen being inspected. Since every point is electronically focused, TFM can provide better resolution compared to conventional phased array ultrasound inspection techniques. By applying appropriate transmission and reception delays to A-scan data collected in a full matrix capture (FMC) dataset, TFM can electronically focus on every location within an inspection region. The total focusing method (TFM) is a synthetic aperture beam forming technique that has been under active development in the NDT industry over the past decade. The results also indicate that the model can be used to guide the selection of the optimal TFM inspection mode. Results from the validation experiments show good agreement between the empirical TFM amplitude maps and theoretical AIM. The accuracy of this new acoustic model was tested and validated by experiments using test blocks that contain side-drilled holes and flat-bottom holes. For complicated acoustic paths that involve multiple interface interactions and wave-mode conversions, a knowledge of the Acoustic Influence Map (AIM) enables an inspector to refine the scan plan to maximize the signal-to-noise ratio of the resultant TFM image and increase the probability of flaw detection. In this paper, we introduce a newly developed semi-analytical model to predict the total focusing method (TFM) amplitude sensitivity map for both nondirectional and directional flaws.
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