QQ-N-286G the end scan procedure, still using the specified � inch grid lines if their use results in an acceptable signal presentation (the 41 degree transducers typically provide enough 45 degree sound energy to perform the required inspections).
A) Center scan. The catch transducer shall be placed in position R1 or R2 (see figure 2) for the center scan depending on the ease of fixturing and the ability to penetrate highly
attenuative material. The transducers for the center scan shall be fixtured and locked in position during scanning. The fixture shall be adjustable to compensate for different sizes and to
peak the signal during initial set up. With the transducers aligned and locked into place, the transmitted signal shall be set between 80 and 90% full screen height. The transducers shall be scanned along the entire length of the bar, rod or forging. Changes in material attenuation will be shown by gradual change in signal amplitude and will occur gradually along the length of the form - either highest or lowest in the center and gradually increasing or decreasing as the fixture is scanned toward the bar ends. Gradual changes in signal amplitude shall be compensated for with the instrument gain control to maintain 50 to 90% signal along the entire length of the bar, rod or forging.
B) End scan. The end of the bar, rod or forging shall be scanned with a similar technique. For end scans, fixturing is not practical and an indexing system shall be used to track transducer positions. As illustrated in figure 3, the end of the form shall be marked at � inch increments across the diameter. One side of the form shall be similarly marked in � inch increments for a length of one diameter. The transducers are initially placed nose to nose at the corner of the form and an 80 to 90% full screen height signal is obtained. The transducers shall then be indexed one mark at a time simultaneously and the signal is read for each index position.
It is mandatory to hold the transducers at their index positions and then read the signal - do not peak the signal for the
maximum signal amplitude. Changes in attenuation due to the changing sound path and changes in material attenuation will be shown by a gradual change in signal amplitude while the transducers are indexed. Gradual changes in signal amplitude shall be compensated for with the instrument gain control to maintain a 50 to 90% signal along the entire scan length.
4.3.3.3 Procedure for other ultrasonic inspections. The following paragraphs describe the requirements for ultrasonic inspection of rod, bar, ring, hollow round products, disc and pancake forgings and plate. Sheet, strip, and wire are specifically excluded from these requirements. Unless otherwise specified below, inspection shall be in accordance with NAVSEA T9074-AS-GIB-010/271 or MIL-STD-2132.
(a) Ring and hollow round products. In addition to the circumferential scan required by NAVSEA T9074-AS-GIB-010/271 or MIL-STD-2132, products shall be inspected with a longitudinal wave test in the radial and axial directions.
(b) Plate. Calibration shall be performed on a flat bottomed hole in lieu of the plate back reflection specified in NAVSEA T9074- AS-GIB-010/271 or MIL-STD-2132. For plate thicknesses up to and including 4 inches, a � inch diameter hole shall be used. For plate thicknesses greater than 4 inches, a � inch diameter hole shall be used. The hole shall be drilled into the test piece or into a separate defect-free specimen of the same size (within
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