Fatigue Behavior of Line Pipes Subjected to Severe Mechanical Damage

Abstract

Fatigue behavior of electrically resistance welded (ERW) line pipes with a gouge in a dent was experimentally investigated. After denting and machining a gouge, fluctuating internal pressure was applied to line pipes. The fatigue behavior differed above and below the threshold Q(Qth), as a function of defect size and fracture toughness. When Q < Qth, ductile crack growth was observed with a consequent decrease in fatigue life. On the contrary, fatigue crack growth was observed when Q ≧ Qth. Fatigue life was predictable with an experimentally based power law equation incorporating dent depth, gouge depth, and hoop stress amplitude when Q ≧ Qth.

The effect of dents in pipelines—guidance in the pipeline defect assessment manual

“…8). Short fatigue lives have been attributed to a combination of fatigue crack growth and crack growth due to ductile tearing [37]. Experiments have shown that the fatigue life can be increased by dressing the gouge to remove any cracking and hardened layer at the base of the gouge, to leave a dent containing a smoothly profiled metalloss defect (see Fig.…”

“…8). The total number of published full scale fatigue tests of smooth dents containing 'gouges' is approximately 81 [10,19,20,28,30,36,37,41,42]. All of these 'gouges' have been machined notches or slots.…”

Fatigue assessment of an electrical resistance welded oil pipeline

“…It is interesting to determine how well the failure could have been predicted by existing modeling tools. As mentioned in Section 1, Hagiwara et al [15] proposed using the parameter Q, a function of defect size and fracture toughness incorporating dent depth, gouge depth and stress amplitude, to explain fatigue behavior. When QϽQ th fatigue life N f is less than 1000 cycles, and requires immediate repair or replacement.…”

“…ERW line pipes generally also have large residual stresses. The effects of residual stress of ERW line pipes on fatigue behavior with a severe artificial defect was examined in fatigue tests carried out by Hagiwara et al [15] on 20-30 cm diameter line pipes. By the parameter Q, a function of defect size and fracture toughness, fatigue behavior could be explained well.…”

Fatigue life prediction of 2524‐T3 and 7075‐T62 thin‐sheet aluminium alloy with an initial impact dent under block spectrum loading

“…In fact, the presence of an impact dent always leads to a deterioration in the fatigue limits and lifetimes of metallic sheets, and it is significant to investigate the fatigue characteristics of post-impacted sheets. So far, there seems to be a great deal of investigations on the effects of the aforementioned factors on the fatigue behavior of metallic sheets, [19][20][21][22][23][24][25][26][27] and it can be concluded that the residual stress 19,22,24,25,[27][28][29] and stress concentration 21,26,27 caused by the LVI are the primary factors affecting the fatigue behavior of metallic sheets. However, only a few studies [30][31][32] on quantitative models for fatigue life prediction of post-impacted sheets have been carried out.…”