T9074-AS-GIB-010/271 Rev 1
6.6.1.3 Round and Multi-Sided Forged or Wrought Bars Including Disc or Pancake Forgings.
6.6.1.3.1 Test Calibration, Longitudinal Wave. Sound transmission into the forging shall be confirmed by observing the first back reflection obtained from the forging. Sensitivity of the instrument shall be adjusted until the indication from the specified calibration standard is at 80 percent of full screen height. The calibration standard shall conform to the requirements of table 6-1. 6.6.1.3.2 Testing - Longitudinal Wave. Each bar or forging shall be tested using the continuous scanning method on surfaces such that all major planes shall be covered. For bars, scanning with the sound beam directed axially shall be performed only when specified.
6.6.2 Plate and Sheet.
6.6.2.1 Shear Wave Testing Technique. Shear wave testing shall be performed only when specified.
6.6.2.1.1 Test Calibration, Shear Wave. When specified, shear wave inspection shall be performed to 3-percent notch sensitivity. A calibration reference notch shall be formed in the test surface of the plate being inspected or acoustically similar test piece. An angle beam search unit, capable of transmitting a shear wave at an angle of 45 degrees in the material being tested, and a frequency of 2.25 MHz shall be used. The instrument shall be adjusted to display signals from the reference notch specified in table 6-2 at one-half and full skip distance. The amplitude of the reflected signal from the calibration standard at the half skip distance shall be adjusted to 80 percent of full screen height. The amplitude of the signal from the calibration standard at full skip distance shall be marked on the viewing screen. A line shall be drawn from the peak signal at half skip to the peak signal at full skip distance. Flaws in the plate or sheet being inspected shall be evaluated to the test sensitivity as established by this line. 6.6.2.1.2 Grid Test Procedure. When grid shear wave testing is specified, it shall be performed by scanning one major surface in two directions, causing the sound beam to travel parallel to and perpendicular to the longitudinal axis or direction of rolling of the plate. In the case of square cross-rolled plate, either direction is acceptable. The search unit shall be moved in parallel paths on a 6-inch grid. If an indication is obtained that has an amplitude 50 percent or greater of that established in 6.6.2.1.1, the adjacent area shall be scanned by the continuous scanning method sufficiently to establish the size and location of the discontinuity. 6.6.2.1.3 Continuous Scanning Procedure. When continuous shear wave testing is specified, it shall be performed by continuously scanning one major surface completely in two directions, causing the sound beam to travel parallel to, and perpendicular to the longitudinal axis or direction of rolling of the plate. The search unit shall be moved in parallel paths to accomplish continuous scanning until the entire dimension is traversed. Either full skip or 1½ skip shall be used to insure that both upper and lower surfaces and the entire interior volume are interrogated.
6.6.2.2 Longitudinal Wave Testing Technique.
6.6.2.2.1 Testing Calibration, Longitudinal Wave. A longitudinal wave search unit having a dimension of l inch square or l inch in diameter, operating at a frequency of 2.25 MHz, unless otherwise specified, shall be placed on a defect free area. (A defect-free area is defined as an area that has been evaluated at the highest ultrasonic sensitivity applicable for the test.) The ultrasonic instrument gain shall be adjusted to display the first back reflection at full screen height. This sensitivity level shall be used to evaluate the plate.
6.6.2.2.2 Test Procedures.
6.6.2.2.2.1 Continuous Method. Continuous scan method testing shall be performed by scanning one major surface 100 percent, only when specified. 6.6.2.2.2.2 Static Method. Testing shall be performed by interpreting the instrument display when the search unit has been statically placed at each intersecting grid line on one major surface of the plate. The grid pattern shall consist of not greater than 2-foot squares for all plate and sheet over ½inch to and including 2½ inches thick. For plates over 2½ inches, the grid
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