On the weld root fatigue strength and improvement techniques for non-load-carrying transverse attachment joints with single-sided fillet welds and made of mild and ultra-high-strength steels

Abstract

The present study experimentally and numerically investigates the fatigue strength of non-load-carrying transverse attachment joints prepared with single-sided fillet weld. Constant amplitude fatigue tests are carried out on specimens made of S355 and S1100 steel grades to obtain the fatigue strength of these joints. In addition, the study evaluates fatigue life improvement technique for these joints comprising the use of a curved plate edge shape in the attachment, which results in varying weld penetration and weaved weld root shape. Numerical analyses are carried out to determine the applicability of the effective notch stress concept in assessing the fatigue strength of the studied joints. The experimental results show that the weld root to the base plate is the critical fatigue failure mechanism, and characteristic design fatigue strengths of FAT97.7% = 109 MPa and FAT97.7% = 97 MPa (with a slope parameter of m = 3) in the nominal stress system for the S355 and S1100 grades with a straight root geometry are obtained, respectively. Using a curved plate edge shape and varying weld penetration, the fatigue strength could be improved by up to 25% for the S1100 grade. The numerical analyses reveal that the effective notch stress modeling technique of the fictitious notch radius significantly affects the stress concentration factors, while the fillet-type modeling technique at the weld root showed more accurate results than the keyhole shape.