Improved effective notch strain approach for fatigue reliability assessment of load-carrying fillet welded cruciform joints in low and high cycle fatigue

An improved effective notch strain (ENSN) approach is developed for the fatigue reliability assessment of load-carrying fillet welded cruciform joints in low and high cycle fatigue regions. The ENSN approach is improved in the ENSN estimation using an analytical approach, and the improvement is verified using some published experiments performed in the low cycle fatigue regime. The cruciform joint is modelled as a correlated two-component series-system, and various sources of uncertainties are considered. The fillet weld geometry uncertainty is modelled by correlated position variations of geometrical control points. To avoid iterative calls of the finite element analysis in the fatigue reliability assessment, response surface models are constructed, and they are used to approximate the influence of position changes. A critical fatigue notch factor is proposed to represent the fatigue resistance for a given fatigue loading and material, which allows a direct reliability approximation. The critical fatigue notch factor for an ice-induced fatigue loading is derived. The ENSN approach is more reasonable to be used for this type of fatigue loading than the high cycle fatigue approach. A cruciform joint subjected to ice-induced fatigue loading is assessed to demonstrate the application of the fatigue reliability assessment procedures.