T.O. 33B-1-15-56Figure 5-60. Effect of Delaminations in a Plate on Multiple Back Surface Signals.5.3.6.5.3 SurfaceWaveIndicationsinStraightBeamandAngleBeamInspections.Surface waves can be generated when using straight beam search units. This is due to the side lobe energy (see Figure5-15). Surface waves have also been observed in some inspections using angle beam search units. These surface wavescan cause signals from edges of the test part, which can be mistaken for a discontinuity. These signals (shown inFigure 5-61) are easily identified by varying the distance between the search unit and the part edge and watching thesignal move. The surface wave signal will move toward the initial pulse as the search unit is moved toward the edge.
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