T.O. 33B-1-1
5-36
Table 5-3 Continued
Incident longitudinal wave angle in plastic (degrees)
Refracted shear
wave angle in test
materials (degrees)
Steel
Stainless
Steel
302
Stainless
Steel
410
Ti
150A
Al
1100-0
Al
2014-T4
Inconel
Wrought
Magne
-sium
AM 35
62
46.9
49.1
52.0
49.1
49.5
49.5
51.3
49.5
63
47.4
49.7
52.7
49.7
50.1
50.1
52.0
50.1
64
48.0
50.3
53.4
50.3
50.7
50.7
52.6
50.7
65
48.5
50.9
54.0
50.9
51.3
51.3
53.3
51.3
66
49.0
51.4
54.7
51.4
51.9
51.9
53.9
51.9
67
49.5
52.0
55.3
52.0
52.5
52.5
54.4
52.5
68
50.0
52.5
55.9
52.5
53.0
53.0
55.1
53.0
69
50.5
53.0
56.5
53.0
53.5
53.5
55.6
53.5
70
51.0
53.5
57.0
53.5
54.0
54.0
56.2
54.0
71
51.4
54.0
57.6
54.0
54.5
54.5
56.7
54.5
72
51.8
54.5
58.1
54.5
55.0
55.0
57.2
55.0
73
52.2
54.9
58.6
54.9
55.5
55.5
57.7
55.5
74
52.6
55.3
59.1
55.3
55.9
55.9
58.2
55.9
75
53.0
55.8
59.6
55.8
56.3
56.3
58.6
56.3
76
53.3
56.1
60.0
56.1
56.7
56.7
59.1
56.7
77
53.7
56.5
60.5
56.5
57.1
57.1
59.5
57.1
c. Note the serrations on the wedges in Figure 5-36 and Figure 5-38. These serve to dampen and scatter
reflected sound that does not initially enter the test part. The serrations, therefore, reduce spurious
signals.
d. The configurations of the wedges in Figure 5-36 and Figure 5-38 may be modified as required to take
care of special geometry situations. In all cases, wedges shall be fabricated to provide the proper
refracted angle for the desired mode of vibration. In addition, they shall provide for transmission of
sound into the test part at the locations required to cover the areas of suspected flaws.
e. Figure 5-37 shows how the coupling fixture is used with the wedge in Figure 5-38. A few drops of
couplant material is needed between the search unit and any wedge to ensure good sound transmission.
f. Figure 5-39 shows a typical shoe used for curved surfaces. This example may be used as a guideline for
fabrication of shoes for curved surfaces. Dimensions may be changed to accommodate the specific part
to be inspected.
