Influence of residual welding stresses on fatigue crack growth under compressive loading

Fatigue cracks have been grown in large as-welded BS4360 50 D structural steel specimens cut from massive plates. Notches and fatigue cracks were made to gape open by tensile residual stresses which rearranged and remained high perpendicular to the discontinuity tips. When specimens were cycled under applied compression crack growth rates were observed which were up to 90% as fast as those produced in stress relieved control samples under pulsating tension. Crack deceleration and arrest was associated with the proximity of the neutral axis and a reduction in residual tensile stress magnitude ahead of the crack tip which led to general crack closure under applied load.