Vol.10, No2, 2010, pp.149-152
UDC  620.179.17 : 669.15  669.15 : 539.431

Fatigue initiation resistance has been determined on API 5L X52 gas pipe steel using Roman Tile (RT) specimen and acoustic emission to detect fatigue initiation. Results for intact and hydrogen electrolytically charged specimens are compared. After hydrogen embrittlement fatigue initiation time is reduced for 3 times. Notch Stress Intensity (NSI) factor is applied as parameter of fatigue initiation process. Since hydrogen is localised in the area with high hydrostatic pressure, definitions of local effective stress and distance have been modified when hydrogen is absorbed, what is explained by the effect of hydrogen on the occurrence of a ductile-brittle transition.

Keywords: fatigue initiation resistance, API 5L X52 steel, Notch Stress Intensity (NSI) factor