Fracture Mechanics Based Analysis of the Fatigue Life of Defective Welded Joints

This work was motivated by the endeavour to experimentally determine the influence of crack position on the fatigue life of weldments. Plates were cut from a pipe of X52 pipeline steel - 830mm in diameter and 10mm in wall thickness - and their contact edges were then prepared for single-bevel butt welds. The plates were then welded by manual arc welding, and separate specimens - 10mm in width and 5mm in thickness - were cut from the weldment perpendicularly to the weld bead. The electro-spark method was then used to produce blunt crack discontinuities for the initiation of fatigue cracks. The cracked weldment specimens then underwent cyclic loading at reference force level F-max = 5.5kN and stress asymmetry ratio R = F-min/F-max = 0.1. The test results made it possible to quantify the effects of the size and position of crack-like discontinuities on weld fatigue life.