Nominal stresses and Modified Wöhler Curve Method to perform the fatigue assessment of uniaxially loaded inclined welds

Abstract

The present paper summarises an attempt of proposing a simple formula suitable for estimating the fatigue strength of welded connections whose weld beads are inclined with respect to the direction along which the fatigue loading is applied. By explicitly considering the degree of multiaxiality of the nominal stress state damaging the weld toe, such a formula is directly derived from the so-called Modified Wöhler Curve Method (MWCM). The MWCM is a bi-parametrical critical plane approach which postulates that, independently from the complexity of the assessed load history, fatigue strength can accurately be estimated by using the stress components relative to that material plane experiencing the maximum shear stress range. The accuracy and reliability of the proposed design technique were checked against a number of experimental results taken from the literature and generated by testing steel plates with inclined fillet-welded attachments. This validation exercise allowed us to prove that the devised formula can successfully be used in situations of practical interest to design against fatigue welded joints whose welds are inclined with respect to the direction along which the cyclic force is applied.