T9074-AS-GIB-010/271 Rev 1
Table 6-1. Calibration Hole Size for Longitudinal Test.
Diameter of Flat Bottomed Hole (FBH) (Inches ±0.005)
Section Thickness (Inches)
Less than ½
1 ⁄ 1 ⁄ 3 ⁄
32
½ to less than 1½ 1½ to less than 2½ 2½ to less than 3½ 3½ to less than 4½ 4½ to less than 5½ 5½ to less than 6½
16
32
⅛
5 ⁄ 3 ⁄ 7 ⁄
32
16
32
6½ and over
¼
NOTES: 1.
All flat bottomed holes shall have bottoms parallel to the entrant or to the tangent of
the entrant surface. 2.
The calibration standard shall be wide enough to permit sound transmission to the
flat bottomed hole without side effects. 3.
The calibration standard material shall be acoustically similar and within ⅛ inch of the T m to be inspected and shall be ultrasonically sound. The surface finish shall be in accordance with 6.3.2 and entrant surface curvature shall be similar to the test specimen. 4. Flat bottomed holes for test standards shall be drilled to a depth of one-half the thickness or 1 inch, whichever is less. A shallower flat bottomed hole may be used as long as the hole can be resolved from the back wall. 5. The test frequency shall be the same as the calibration frequency. 6. The couplant used for calibration shall be the same as that used for inspection. 7. The use of distance amplitude correction curves is permitted for calibration.
6.6.1.1 Ring Forgings.
6.6.1.1.1 Shear Wave Tests of Ring Forgings.
6.6.1.1.1.1 Test Calibration, Shear Wave. The calibration standard for ring forgings with wall thicknesses not greater than 20 percent of the outside diameter shall have two notches cut axially, one on the inside surface and one on the outside surface of the test standard. They shall be located so that their sides are smooth and parallel to the axis of the forging and readily distinguishable individual ultrasonic indications are obtained from each notch. Shear wave inspection shall be performed at 3 percent notch sensitivity. The dimensions of the notch shall comply with table 6-2, except that available V-shaped calibration notches that were fabricated to meet the requirements of MIL-STD-2132 are acceptable for use. Scan until the notch indication from the inside diameter appears at the farthest position to the left at which it is readable. Move the search unit away from the inside diameter notch until the indication from this notch reappears along the horizontal trace. Mark these two positions on the face of the scope. Scan until the notch indication from the outside diameter is produced at maximum amplitude between these two marks. The amplitude of this notch indication shall be marked on the face of the scope. When the test instrument incorporates distance-amplitude controls, it is recommended that they be used where possible to equalize these indication amplitudes to form an ARL of not less than 50 percent of full screen height. If this is not possible, or if the instrument is not equipped with a distance amplitude correction circuit, a distance amplitude curve shall be constructed on the screen with the lowest point at not less than 20 percent full screen height. Ring forgings with wall thicknesses exceeding 20 percent of their diameters cannot be inspected by circumferential shear wave scan where both inside and outside notches must be monitored. Alternate ultrasonic inspection methods for these forgings shall be specified.
6-5
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