| Abstract Scope |
In actual pipeline systems, repeated pumping is applied to transport resources. During this operation, internal pressure fluctuations can cause fatigue cracks to initiate inside the pipe. This may lead to a Pressure Reversal phenomenon, where failure occurs at pressures lower than the material’s fracture strength due to stress cycling. In this study, we evaluated the Pressure Reversal susceptibility of the ERW weld zone. To simulate this phenomenon, a 3-point bending fatigue test with slight plastic deformation was performed for 20 cycles. Without hydrogen charging, no cracks occurred, indicating resistance. However, after hydrogen charging, cracks formed within a few cycles, confirming hydrogen’s detrimental effect. Fracture surface analysis showed that hydrogen promoted dislocation motion and induced localized plastic deformation near the crack tip, suggesting that hydrogen embrittlement was primarily caused by the HELP mechanism. In summary, hydrogen exposure significantly reduced the Pressure Reversal resistance of the ERW weld zone. |