Recent developments in local concepts of fatigue assessment of welded joints

Probabilistic framework for fatigue life assessment of notched components under size effects

Very high cycle fatigue measuring techniques

The notch stress approach for fatigue assessment of welded joints is based on the highest elastic stress at the weld toe or root. In order to avoid arbitrary or infinite stress results, a rounded shape with a reference radius, instead of the actual sharp toe or root, is usually assumed. Different proposals for reference radii exist, e.g. Radaj proposed a fictitious radius of 1 mm to consider micro-structural support effects for steel. The present guideline reviews different proposals for reference radii together with associated S-N curves. Detailed recommendations are given for the numerical analysis of the notch stress by the finite or boundary element method. Several aspects are discussed, such as the structural weakening by keyhole-shaped notches and the consideration of multiaxial stress states. Regarding the fatigue strength, appropriate S-N curves are presented for different materials. Finally, four examples illustrate the application of the approach, as well as the variety of structures that can be analysed and the scatter of results obtained from different models.

IIW recommendations for the fatigue assessment of welded structures by notch stress analysis: IIW-2006-09

In the literature, allowable stresses (FAT-values) for the fatigue design of welded joints are established according to the notch stress concept with the reference radii rref = 1.00 mm for thick connections (t ≥ 5 mm) and 0.05 mm for thin connections (t < 5 mm). However, it is not clear for which strength hypothesis they are valid. As local equivalent stresses may be calculated by the principal stress or von Mises hypotheses, it is necessary to distinguish between the applied hypotheses. The FAT-values according to the principal stress and von Mises hypotheses are compiled for steel, aluminium and magnesium for the reference radii rref = 1.00 and 0.05 mm. The allowable stresses are derived from normal as well as from shear stresses. However, the values derived from pure normal loading (axial or bending) and from pure torsion are not compatible when the principle stress or the von Mises hypotheses are applied. Therefore, in case of biaxial loading, the stated incompatibility between the values obtained from different loading modes should be overcome by the Gough-Pollard relationship.

A Consideration of Allowable Equivalent Stresses for Fatigue Design of Welded Joints According to the Notch Stress Concept with the Reference Radii r ref = 1.00 and 0.05 mm

New method for evaluation of the Manson–Coffin–Basquin and Ramberg–Osgood equations with respect to compatibility

Fatigue assessment of laser welded thin sheet aluminium

Transferability of Material Data for the Example of a Randomly Loaded Forged Truck Stub Axle

A study of compatibility between two classical fatigue curve models based on some selected structural materials

Multiaxial fatigue behaviour of laserbeam-welded thin steel and aluminium sheets under proportional and non-proportional combined loading

Heinz Kaufmann

Papers

New method for evaluation of the Manson–Coffin–Basquin and Ramberg–Osgood equations with respect to compatibility

Fatigue assessment of laser welded thin sheet aluminium

Transferability of Material Data for the Example of a Randomly Loaded Forged Truck Stub Axle

A study of compatibility between two classical fatigue curve models based on some selected structural materials

Multiaxial fatigue behaviour of laserbeam-welded thin steel and aluminium sheets under proportional and non-proportional combined loading