5 The given values are the average of three tested samples. The given values are the average of three tested samples. In order to help in identification of failure mechanism, fracture surface was carefully examined using stereoscope and scanning electron microscope. Low magnification photographs of fracture surface of 16" pipe side of the spool are shown in Fig. 5. Crack initiation zones and fracture propagation directions are highlighted with arrows. It is obvious that multi-cracks were initiated at the outer surface, where smooth fracture surface can be seen, then propagated toward inner surface. In other words, crack suspected initiation zones at the outer surface appeared relatively smooth and associated with beach marks and a propagating ductile crack. Crack termination zones at the inner surface had a rough texture associated with the final fracture. Figure 5. Low magnification photographs of fracture surface of 16" pipe side of spool. Crack initiation zones and fracture propagation directions are highlighted with arrows. Note beach marks at crack suspected initiation zones. Table 3. Results of tensile test of circumferential welded joints together with the specified values for ASME-SA213, 316L stainless steel. Table 4. Results of impact test of circumferential welded joint together with the specified values for ASME-SA213, 316L stainless steel.
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