Ultrasonic peening of X70 and X100 steel pipe fatigue test specimens

The aim with this report is to describe the ultrasonic peening treatment of X70 and X100 steel pipe fatigue test specimens carried out at CSM Laboratories in Rome.
A description of the ultrasonic peening equipment, ultrasonic peening procedure and time requirement for the treatment are briefly presented.
Special consideration has been taken to inter-pass weld toe at weld face and weld spatter adjacent to weld root areas in the treated specimens.
Based on previous fatigue test of UP treated welds we assess the potential fatigue life extension for the treated specimens.
IIW Fatigue Recommendations classification of this detail is FAT 71. Our conservative estimate is that the specimens could be classified as FAT 151 after UP treatment. These two FAT values are stress ranges expressed as Design Curves, mean value minus two standard deviations, at 2. 106 cycles.
Consideration is taken to the fact that the specimens are manufactured on X70 respective X100 steel pipe, high-strength steel pipe.

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