The results of the field tests at Stupp are summarized in table 12. There were four field specimens tested, with all three inspection methods accepting all four specimens.
Figure 120. Field specimen FG40M-TF1-Curved-FCM: Top view of joint. |
Figure 121. Field specimen FG40M-TF1-Curved-FCM: Side view of joint. |
Figure 122. Radiographic image of field specimen FG40M-TF1-Curved-FCM: Section B-C. |
Figure 123. P-scan images of field specimen FG40M-TF1-Curved-FCM: From TSC side of centerline between 0 and 228.6 mm (0 and 9 inches). |
Figure 124. P-scan images of field specimen FG40M-TF1-Curved-FCM: From BSC side of centerline between 0 and 228.6 mm (0 and 9 inches). |
Figure 125. P-scan images of field specimen FG40M-TF1-Curved-FCM: From TSC side of centerline between 228.6 and 457.2 mm (9 and 18 inches). |
Figure 126. P-scan images of field specimen FG40M-TF1-Curved-FCM: From BSC side of centerline between 228.6 and 457.2 mm (9 and 18 inches). |
Figure 127. P-scan images of field specimen FG40M-TF1-Curved-FCM: From TSC side of centerline between 457.2 and 685.8 mm (18 and 27 inches). |
Figure 128. P-scan images of field specimen FG40M-TF1-Curved-FCM: From BSC side of centerline between 457.2 and 685.8 mm (18 and 27 inches). |
Figure 129. P-scan images of field specimen FG40M-TF1-Curved-FCM: From TSC side of centerline between 685.8 and 993.8 mm (27 and 39.125 inches). |
Figure 130. P-scan images of field specimen FG40M-TF1-Curved-FCM: From BSC side of centerline between 685.8 and 993.8 mm (27 and 39.125 inches). |
Figure 132. Field specimen FG1A-TF2-BottF-FCM: Side view of joint. |
Figure 133. P-scan images of field specimen FG1A-TF2-BottF-FCM: From TSC side of centerline using 60-degree probe. |
Figure 134. P-scan images of field specimen FG1A-TF2-BottF-FCM: From TSC side of centerline using 70-degree probe. |
Figure 135. P-scan images of field specimen FG1A-TF2-BottF-FCM: From BSC side of centerline using 70-degree probe. |
Figure 136. Field specimen G3VHW-CF1-BottF: Top view of joint. |
Figure 137. Field specimen G3VHW-CF1-BottF: Radiographic image of section A-B. |
Figure 138. Field specimen G3VHW-CF1-BottF: P-scan images from TSC side of centerline using 70-degree probe. |
Figure 139. Field specimen G5VHW-CF1-BottF: Top view of joint. |
Figure 140. Field specimen G5VHW-CF1-BottF: Side view of joint. |
Figure 141. Field specimen G5VHW-CF1-BottF: Radiographic image of section B-C. |
Figure 142. P-scan images of field specimen G5VHW-CF1-BottF: From TSC side of centerline using 45-degree probe. |
Figure 143. P-scan images of field specimen G5VHW-CF1-BottF: From BSC side of centerline using 45-degree probe. |
Figure 144. P-scan images of field specimen G5VHW-CF1-BottF: From BSC side of centerline using 70-degree probe. |
For comparison, the laboratory and field specimens with rejectable defects were grouped according to plate thickness in 25.4-mm (1-inch) increments (tables 13 and 14). These groupings summarized the results and helped determine the relationship between the effectiveness of each inspection method with respect to the plate thickness. The first column of each table shows the thickness range of the grouped plates. The second column shows the total number of specimens inspected. The third column indicates the number of specimens accepted with no rejectable defects by all three inspection methods. The fourth column shows the number of specimens rejected with rejectable defects by at least one inspection method. The fifth column identifies the rejected specimen. The sixth column shows the number of rejectable defects found. The seventh, eighth, and ninth columns indicate the inspection methods that rejected the particular specimen. The checkmark () stands for "Rejected," indicating that the specimen was rejected by the employed inspection method; X stands for "Accepted," indicating that the specimen was accepted by the employed inspection method; and DWC stands for "Detected/Within Code," indicating that the employed inspection method identified an indication that was within code requirements. Table 13 shows that the three inspection methods produced consistent results in the laboratory. In table 14, there are 8 field specimens with thicknesses ranging from 0 to 50.8 mm (0 to 2 inches) that contained 12 rejectable defects. RT rejected all eight specimens, while UT rejected only three specimens. Note that UT identified defects in the five remaining specimens, but found that the defects were acceptable. In addition, 5 specimens with thicknesses ranging from greater than 50.8 to 101.6 mm (2 to 4 inches) containing 8 rejectable defects also were identified. RT rejected only two specimens, while UT rejected all five specimens. Note that FG36K-TF2-TopF-FCM was not rejected by AUT since the defect was located at the curvature region of the width transition and the P-scan system was not configured to inspect this type of region.
Tables 15 and 16 compare the results of the RT and AUT inspections. The tables are arranged to illustrate: (1) the total number of specimens inspected within each 25.4-mm (1-inch) thickness increment, (2) the total number of specimens that were rejected by at least one inspection technique, (3) the number of specimens rejected by each inspection method, and (4) the number of specimens accepted with identifiable indications.
Table 13. Consolidating the results of laboratory testing using laboratory specimens with rejectable defects.
Thickness Range (inch) |
Total No. of Laboratory Specimens |
No. of Laboratory Specimens Accepted |
No. of Laboratory Specimens Rejected by at Least One Technique |
Rejected Laboratory Specimen |
Ind. No. |
Rejected by RT |
Rejected by UT |
Rejected by AUT |
---|---|---|---|---|---|---|---|---|
0-1 |
6 |
0 |
6 |
S033 (0.5" thick) |
1 |
|||
2 |
||||||||
S034 (0.5" thick) |
1 |
|||||||
2 |
X1 |
|||||||
S125 (1" thick) |
1 |
|||||||
2 |
||||||||
3 |
||||||||
S126 (1" thick) |
1 |
|||||||
2 |
||||||||
3 |
||||||||
4 |
DWC |
|||||||
S135 (1" thick) |
1 |
|||||||
2 |
||||||||
3 |
||||||||
S136 (1" thick) |
1 |
|||||||
2 |
||||||||
>1-2 |
4 |
2 |
2 |
S132 (1.5" thick) |
1 |
|||
S133 (1.5" thick) |
1 |
1AUT is not configured to detect transverse crack.
DWC: Detected/Within Code
Table 14. Consolidating the results of field testing using field specimens with rejectable defects.
Thickness Range (inch) |
Total No. of Field Specimens |
No. of Field Specimens Accepted |
No. of Field Specimens Rejected by at Least One Technique |
Rejected Field Specimen |
Ind. No. |
Rejected by RT |
Rejected by UT |
Rejected by AUT |
---|---|---|---|---|---|---|---|---|
0-1 |
5 |
3 |
2 |
G5G-TF1-TopF (1" thick) |
1 |
DWC |
DWC |
|
2 |
DWC |
DWC |
||||||
TP2 (1" thick) |
1 |
|||||||
2 |
||||||||
3 |
||||||||
4 |
||||||||
>1-2 | 23 |
17 |
6 |
FG26G-TF2-BottF-FCM (1.75" thick) |
1 |
DWC |
DWC |
|
FG16D-TF1-BottF-FCM (2" thick) |
1 |
DWC |
DWC |
|||||
AWS-FCM-02-6A (1.5" thick) |
1 |
|||||||
FG1A-TF2-BottF-FCM (2" thick) |
1 |
|||||||
G3VHW-CF1-BottF (1.75" thick) |
1 |
DWC |
DWC |
|||||
G5VHW-CF1-BottF (1.75" thick) |
1 |
DWC |
DWC |
|||||
>2-3 | 13 |
9 |
4 |
FG36K-TF2-TopF-FCM (3" thick) |
1 |
X* |
||
2 |
X |
|||||||
FG37K-TF3-BottF-FCM (3" thick) |
1 |
X |
||||||
FG38K-TF2-TopF-FCM (3" thick) |
1 |
|||||||
2 |
X |
|||||||
FG40M-TF1-Curved-FCM (3" thick) |
1 |
X |
||||||
2 |
X |
|||||||
3-4 |
3 |
2 |
1 |
G2G-CF1-BottF-FCM (3.15" thick) |
1 |
X |
*AUT is not configured to detect transverse defects or inspect width transition regions.
Table 15. Assessing the detectability and rejectability of three inspection methods in the laboratory.
Thickness Range (inch) |
No. of Laboratory Specimens With Rejectable Defects |
No. of Specimens Rejected by AUT |
No. of Specimens Accepted by AUT Within Code |
---|---|---|---|
0-1 |
6 |
6 (100%) |
0 |
1-2 |
2 |
2 (100%) |
0 |
Table 16. Assessing the detectability and rejectability of three inspection methods in the field.
Thickness Range (inch) |
Total No. of Field Specimens |
No. of Field Specimens With Rejectable Defects |
No. of Specimens Rejected by RT |
No. of Specimens Rejected by AUT |
No. of Specimens Accepted by RT Within Code |
No. of Specimens Accepted by AUT Within Code |
---|---|---|---|---|---|---|
0-1 |
5 |
2 |
2 (100%) |
1 (50%) |
0 |
1 |
>1-2 |
23 |
6 |
6 (100%) |
2 (33%) |
0 |
4 |
2-3 |
13 |
4 |
2 (50%) |
4 (100%) |
0 |
0 |
3-4 |
3 |
1 |
0 (0%) |
1 (100%) |
0 |
0 |
To supplement field testing and establish the importance of the code-prescribed transducer articulation, specimen S033 was tested at a series of fixed angles (0 degrees, 2.5 degrees, 5 degrees, 7.5 degrees, and 10 degrees). The angles were measured with respect to a line normal to the weld centerline. The main purpose of articulating the transducer is to obtain the highest possible amplitude echo from a given defect. To accomplish this, the transducer must be articulated so that the direction of the shear wave propagating within the specimen is perpendicular to a plane of the defect. As mentioned earlier, specimen S033 (shown in figures 7 through 10) contained manufactured crack-like defects oriented along the centerline in the weld bevels.
The testing is performed by the P-scan system using a test frame (Figure 145) and a series of wedges designed to keep the transducer at a fixed angle during scanning (Figure 146). Figure 146 shows an angled wedge attached to a vertical sliding bar which is oriented transverse to the weld axis. The transducer is placed against the angled wedge, holding the articulation angle fixed relative to the weld axis. As the sliding bar is advanced along the length of the weld, the transducer is held at the fixed angle of interest.
The maximum echo
amplitudes from the defect were determined from the P-scan images and were
plotted against the transducer articulation angles (Figure 147). The abscissa
in Figure 147 represents the transducer articulation angles, and the ordinate
represents the indication rating (d). The indication rating of negative dB is
indicative of a high-amplitude echo and the indication rating of positive dB is
indicative of a low-amplitude echo. It is evident from Figure 147 that the
amplitude of the echo decreases from a high value of -4 dB to a low value of
+14 dB as the articulation angle increases from 0 to 10 degrees, respectively.
The 0-degree articulation angle, which produces the highest indication rating
of -4 dB, reveals that the direction of the incident traveling wave is aligned
normal to the plane of the crack thus reflecting the highest amount of
ultrasonic energy. For articulation angles other than 0 degrees, the incident
traveling wave is no longer perpendicular to the plane of the crack, leading to
less ultrasonic energy reflection. The difference in the echo amplitude between
the articulation angles of 0 degrees and 2.5 degrees, 2.5 degrees and
5 degrees, 5 degrees and 7.5 degrees, 7.5 degrees and 10 degrees are
5 dB, 6 dB, 5 dB, and 2 dB, respectively. The 2-dB to 6‑dB
difference in the echo amplitude is significant in rejecting or accepting a
weld based on the indication rating criteria set forth in the UT
acceptance-rejection criteria in tables 6.3 and 6.4 in the AASHTO/AWS
D1.5M/D1.5: 2002 Bridge Welding Code.(1) Therefore, a rejectable
defect may be misrepresented as an acceptable indication if articulation of the
transducer is eliminated.
Figure 145. Transducer articulation testing: Test setup. |
Figure 146. Transducer articulation testing: Various articulation angle wedges. |
Figure 147. Influence of transducer articulation angle on the maximum amplitude of the reflected signal. |
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