T9074-AS-GIB-010/271 Rev 1
APPENDIX B REQUIREMENTS FOR ULTRASONIC CHARACTERIZATION AND SIZING INSPECTION OF EMBEDDED AND SURFACE CONNECTED DISCONTINUITIES B.1 SCOPE. This appendix provides the requirements and describes the techniques for ultrasonic characterization and through-wall dimensioning of embedded and surface breaking discontinuities in the T m range of 0.25 inch to 4.5 inches. This process is only applicable to evaluating single discontinuities in wrought ferrous base metals and low alloy steel welds. B.1.1 Certification. In addition to the basic certification requirements specified in Chapter 1, nondestructive test inspectors and Examiners employing ultrasonic characterization and crack tip diffraction sizing techniques (UTCS) shall be trained and certified at a NAVSEA approved facility. Inspection personnel shall have a minimum of three years shear wave experience prior to certification. An approved facility must have training and test mock-ups with cracks similar to the defects in the component under evaluation. In addition, all inspection personnel are limited to performing UTCS on components/configurations on which they have been tested/certified. The extent of certification shall be specified on the certification record. Inspectors or Examiners involved in the performance of ultrasonic characterization and sizing inspections shall be recertified with a practical examination if they have not performed these inspection techniques for a period of more than 6 months. B.1.2 Procedure. Ultrasonic characterization and sizing procedures shall be approved by NAVSEA. Procedures used to implement these inspection techniques shall be qualified on samples that contain either service-induced or artificially induced cracks. Additional techniques, not described herein, shall require NAVSEA approval.
B.2 DEFINITIONS.
B.2.1 Absolute Arrival Time Technique (AATT). The absolute arrival time technique (AATT) uses tip signals from 45, 60, and 70-degree angled shear waves and high-angle longitudinal waves for sizing planar discontinuities. The half-skip AATT technique is used to evaluate all discontinuities when possible. B.2.2 Collateral Echo 1 (CE-1). The signal resulting from a shear wave which is mode converted to a longitudinal wave on the back surface of a component and then reflected from a discontinuity or notch face back to the search unit as a longitudinal wave. B.2.3 Collateral Echo 2 (CE-2). The signal resulting from an indirect shear wave which is mode converted to an ID creeping wave on the opposite surface of a component, reflected from a discontinuity or notch face, and mode converted back to a shear wave. B.2.4 Creeping Wave. A creeping wave is a longitudinal wave traveling nearly parallel to and along the metal surface. It can be generated on the probe-side surface of a material through the use of a high angle (usually 70 degrees or higher) longitudinal wave designed wedge. A creeping wave can also be generated on the surface opposite the probe through mode conversion of approximately 33-degree shear waves impinging on the back surface. Specialized transducers and wedges specifically designed to generate creeping waves are used for sizing applications. B.2.5 Echo Dynamics. The manner in which ultrasonic signals travel, peak, and diminish relative to transducer movement as the sound beam travels along a discontinuity. B.2.6 High-Angle Longitudinal Wave (HAL)Technique. The high-angle longitudinal wave technique is used to size discontinuities that are within ½ inch of the inspection surface. The HAL technique is an AATT that makes use of high-angle longitudinal waves to locate the discontinuity tip. This method measures the remaining ligament of material above the discontinuity.
B-1
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