T.O. 33B-1-1
5-45
Figure 5-48. Surface Wave Inspection
5.3.3.3.3
Surface Wave Familiarization.
a. Use a miniature angle-beam block. Attach a 2.25 MHz surface wave search unit to the ultrasonic
instrument.
b. Position the search unit at P-1 as shown in Figure 5-49. Adjust the sweep and gain to obtain a signal
from corner C.
Figure 5-49. Surface Wave Familiarization.
c. Moisten a finger with oil and move it across the surface from the search unit toward corner C. Note that
the corner signal is damped until the finger moves beyond the corner.
d. Move the search unit away from corner C toward corner B as shown in Figure 5-49. Note that the
corner C signal moves to the right along the time base.
e. Position the search unit at P-2 as shown in Figure 5-49. Orient the search unit perpendicular to edge
AC. Adjust the sweep and gain to obtain a signal from edge AC.
f. Rotate the search unit and note that the signal from the edge decreases as the search unit is rotated away
from the normal to the edge. This illustrates that surface waves should always be directed
perpendicular to the expected plane of cracks (see Figure 5-50).
