Status review on fatigue performance of fillet welds

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Status review on fatigue performance of fillet welds

Maddox, Stephen J.

A recent joint-industry project addressing the fatigue design of weld details in FPSO vessels focused on potential fatigue failure from weld toes in joints between the main hull, longitudinal stiffeners and transverse bulkheads. However, there is also the potential for fatigue failure in the weld itself, particularly in fillet welds that are fully load carrying. Therefore, a second phase of the project included analysis and fatigue testing of fillet welded joints under the complex stressing conditions that can arise in ships, with the aim of developing suitable design methods (1). This paper presents a critical review of current design methods, including their background and relevant experimental data, for assessing the fatigue performance of steel fillet welds with respect to failure in the weld throat. The main focus is on fillet or partial penetration welds in cruciform, T or lap joints under transverse loading failing by fatigue crack growth across the weld throat under normal stresses. The review covers the influence of residual stress, applied mean stress, joint fit-up and alignment, weld quality, the use of coated steel, the need for a plate thickness correction and calculation of the optimum weld size. Also considered are cases of fillet welds failing in shear or combined normal and shear stresses.