TWI Industrial Member Report Summary 32/1977
By T R Gurney
A fracture mechanics analysis has been made of the effect of semi-elliptical and continuous defects at the toes of fillet welded joints, on their fatigue strength. It is shown that, for a given joint geometry and fatigue strength, the critical defect size reduces rapidly with plate thickness or, alternatively, that with a fixed size of defect fatigue strength decreases with increasing plate thickness. It is suggested that this may in part account for the size effect often found in fatigue testing. It is also suggested that the proposed new fatigue design rules may not be relevant to joints in thick plate.