Estimating fatigue lifetime of steel weldments locally damaged by variable amplitude multiaxial stress fields

The present investigation aims to prove that the so-called Modified Wöhler Curve Method applied along with the Theory of Critical Distances (formalised in the form of the Point Method) can successfully be used also to estimate fatigue lifetime of steel welded joints subjected to both uniaxial and proportional/non-proportional multiaxial variable amplitude load histories. The accuracy and reliability of our fatigue life estimation technique was systematically checked by reanalysing approximately 500 experimental results taken from the literature and generated by testing welded samples having not only different geometries but also different absolute dimensions. Such an extensive validation exercise allowed us to fully confirm the robustness of our design methodology as well as to show that, when the method itself is formalised for a probability of survival equal to 97.7%, the obtained estimates fully complies, from a statistical point of view, with the recommendations of the available standard codes.