Isabel Huther is a mechanical doctor-engineer and fatigue technical referent at Cetim. She's been working for Cetim since 1996 in the field of component and structure fatigue (testing and design). Fields of competence: • Fatigue material data (testing analysis), • Structure design and calculations for welded joints, • Linear elastic fracture mechanics (testing and analytical calculations). Technical competences: • Training course on component and structure fatigue and linear elastic fracture mechanics • Technical Referent COFRAC for fatigue tests (HCF, LCF) and fracture mechanics (KIC, da/dN) • Contribute to International Institute of Welding works in welded joint fatigue
Preload application techniques are often used to assess the structural integrity of mechanical systems. Generally, these procedures are performed after the fabrication but before the commissioning of such equipment, without any verification of the preload impact on fatigue behaviour.
These approaches are often imposed by standards such as ASTM or DNV that define applicable preload conditions but neither technical justification nor quantification of the positive or negative impacts are usually given.
Following initial researches on a preloading influence on welded S355 longitudinal stiffeners where a benefit effect was highlighted (Huther, Lefebvre, Abdellaoui, & Leray, 2022), the present work described in this paper focuses on two aspects in order to extend the initial conclusions in:
- Completing the previous work for loaded welds of structural steel S355 on transverse stiffeners where the crack can initiate:
- at the weld toe in a case of angle butt weld,
- and at the root in the case of fillet weld without complete penetration.
- Verifying if the benefit is greater on a high-strength steel (S690): meaning that the use of a steel with better tensile properties leads to delay the crack initiation phase.
As described in the former study, a pre-loading in the range 1.56 times the YS (local) can increase the fatigue life if the level of pre-loading is sufficient enough to imply a decrease of the residual stresses due to the welding operation thanks to plastic deformation.