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