The use of cyclic ΔJρ as a parameter for fatigue initiation of X52 steel

The concept of ΔJ cyclic has been extended to fatigue initiation emanating from notch. The parameter is then named ΔJρ. Validation of this parameter is made by fatigue tests made on Roman tile specimens made in X52 pipe steel. Here, fatigue initiation is detected by acoustic emission. It has been found that the fatigue initiation decreases after hydrogen absorption. This can be explained by interaction of hydrogen and plasticity as can be seen for tensile and fracture behaviour of X52 steel after introduction of hydrogen.