Effect of weld toe geometry on fatigue life of lap fillet welded ultra-high strength steel joints

The effect of arc weld toe geometry on pulsating bending fatigue performance was studied using as-welded and toe machined welded joints of an ultra-high strength steel with a tensile strength grade of 980 MPa. Weld toe machining significantly improved the fatigue strength of the welded joints even when the radius of the machined toe was 0.5 mm, although this is smaller than the minimum size described in the document, International Institute of Welding (IIW) Recommendations on Post Weld Improvement of Steel and Aluminium Structures, which applies to welded joints of steel with plate thicknesses from 6 mm to 50 mm. The fatigue cracks of the as-welded joints initiated along the bottom of the ripple pattern in the weld metal near the weld toe. A fatigue life prediction based on the fracture mechanics approach for the as-welded and the toe machined joints suggested that consideration of the microscopic geometry of the weld ripple pattern is important for improving the accuracy of fatigue life predictions of as-welded joints.