Fatigue failure behavior of pipe bends with local wall thinning under cyclic bending condition

In this study, fatigue tests were carried out using real scale pipe bend specimens with wall thinning defects under a cyclic bending load together with a constant internal pressure of 10MPa. The wall thinning defect was located at the extrados and the intrados of the pipe bend specimens. A fully reversed cyclic in plane bending displacement was applied to the specimens. For the pipe bends with wall thinning at the extrados, an axial crack occurred at the crown of the pipe bend rather than at the extrados where the defect was located. In addition, the fatigue life was longer than that of a sound pipe bend predicted from the design fatigue curve in ASME Sec.III, and it was less dependent on the axial length of the wall thinning defect. For the pipe bends with wall thinning at the intrados, a circumferential crack occurred at the intrados. In this case, the fatigue life was much shorter than that of a sound pipe bend predicted from the design fatigue curve, and it clearly decreased with decreasing axial length of the wall thinning defect