ADVANCED MATERIALS & PROCESSES | OCTOBER 2024 20 and shall be placed with a tight fight of less than 0.02 in. gap prior to welding.” Inspection strategy: During testing, the probe was positioned on the part so the signals covered the opposite corner and upper tip of the non-fused portion of the joint. The height from the corner to the upper tip represents the non-fused section of the weldment. The percentage of non-fused area is this height divided by the thickness of the plate. Shear waves were used to generate the S-scan (Fig. 3). These results were tested and compared with different TFM modes using various phased array probes (Table 1). RESULTS AND DISCUSSION Probe selection is crucial as it directly affects resolution and therefore sizing capabilities. The best resolution was obtained using the A32 probe. However, its large footprint could be problematic under real conditions such as a variable weld profile or uneven contact surface. The 2T TFM wave set resulted in better resolution compared to PAUT. Unfortunately, the 4T TFM data was useless due to the location and geometry of the fusion edge reflector. In general, PAUT and TFM penetration measurements were similar, though data acquisition was faster when using PAUT, which is a critical factor (Fig. 4, Tables 2 and 3). TABLE 1 — TEST PLAN Technique Probe Wedge Number of elements Angle range, ° FD PAUT – SW 5L16 A10 SA10 N55S 16 40-75 9 TFM – 2T/3T/4T 5L16 A10 SA10 N55S N/A N/A N/A PAUT – SW 5L32 A31 SA31 N55S 32 49-75 9 TFM – 2T/3T 5L32 A31 SA31 N55S N/A N/A N/A PAUT – SW 5L64 A32 SA32 N55S 32 0-80 9 TFM – 2T/3T 5L64 A32 SA32 N55S N/A 0-80 N/A Fig. 4 — From top, S-scan vs. TFM 2T image at scan position 115 mm with probe 5L16 A10. TABLE 2 — PAUT VS. TFM, SCAN POSITION 115 MM, PROBE 5L16 A10 Scan type Sectorial scan FMC TFM 2T Non-fused distance, mm 2.85 2.15 Penetration, % 68.5 76.1 TABLE 3 — CASE STUDY TEST RESULTS Probe and mode* Scan position, mm Non-fused distance, mm Penetration, % A10 – PAUT 29 2.16 76.1 A10 – TFM 2T 29 2.01 77.8 A10 – TFM 4T 29 Not possible Not possible A31 – PAUT 29 2.34 76.1 A31 – TFM 2T 29 1.98 78 A32 – PAUT 29 2.49 72.3 A32 – TFM 2T 29 1.89 79 A10 – PAUT 115 2.85 68.5 A10 – TFM 2T 115 2.15 76.1 A10 – TFM 4T 115 Not possible Not possible A31 – PAUT 115 2.91 67.6 A31 – TFM 2T 115 2.28 74.6 A32 – PAUT 115 3.04 66.2 A32 – TFM 2T 115 2.33 74.1 *Technique validation should be done using a demonstration block and metallography.
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