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3. Service crack in segment A1

3.1. Section

Fig. 3 shows a section through a SCC in segment A1.The thickness of the pipe was 8 mm, and the ver- tical depth of the crack was about 4 mm, about half of the pipe thickness. The crack path zigzaged at the beginning. The crack propagated along an angle about 45 to the surface as shown by the arrow at A. There was a vertical crack propagation after the first sloping crack (arrow B). The crack propagated alongthe three-dimension strain field ahead of the crack tip. When the crack changed direction, there was a fine branch (e.g. at arrows C, D, E) along the original direction of cracking. The fine branches did not keep growing. When the crack was sufficiently deep, there was crack branching (arrow F) and two cracks propagated. The long crack was about 5.5 mm in length, and the short one was about 4.6 mm in length. Before the arrow at F, the crack was more open.

Fig. 1. Slow and fast potentiodynamic scans for X65 in 1 N Na₂CO₃+1 N NaHCO₃ solution at 70 ^oC.

Fig. 2. Loading procedures for JQ1 and JQ2 LIST tests, (a) JQ1;(b) JQ2.

Fig. 3. Cross section of segment ‘‘C’’.