۱٫ Introduction

۲٫ Specimen description and experimental set-up

۳٫ Experimental tests

۴٫ Fatigue life assessment

۵٫ Discussion and conclusions

References

In the present work, the Fatemi-Socie approach is adopted in order to analyze the fatigue endurance of welded joints under multiaxial loads. This critical plane criterion has already been successfully applied to plain or notched components, however, it is not spread in the assessment of welded joints, yet. This work is focused on the practical implementation issues related to this particular application, which has not been discussed in the literature. The described procedure is adopted for the assessment of one hundred experimental tests and some preliminary results are shown. The specimen under investigation is a pipe-to-plate fillet joint made out of structural steel (S355JR). The tests were performed under both uniaxial and multiaxial, i.e. combined in-phase and out-of-phase bending and torsion, load conditions with a constant amplitude at the laboratories of the University of Pisa, Italy.

Introduction

The fatigue life assessment of notched components under multiaxial loads is a problem of wide practical interest since most of the components in real applications show geometrical details that produce local stress concentrations. Also, many actual applications are characterized by the presence of multiple independent loads, which produce a multiaxial non-proportional state of stress/strain. Even when a single load is applied, we can generally observe a multiaxial state of stress/strain in the volume of material surrounding a notch, even though in this case it is usually proportional. For the sake of simplicity experimental tests are often performed applying a constant amplitude uniaxial load and often times simple plain (un-notched) specimens are used in those investigations. Based on this fact, there is need to develop a procedure able to relate, in terms of fatigue damage, the actual multiaxial state of stress with the endurable (often uniaxial) stress state that is known from experiments, in order to estimate the fatigue life of real components.