Acceptance levels of misalignment of welded joints under different quality categories

Abstract

To enable rapid fatigue assessment of welded joints containing misalignment, the quantitative relationships between the acceptance level of misalignment and the fatigue strength were investigated based on fracture mechanics. The procedure for obtaining the tolerance limits of the stress magnification factor (km) due to misalignment across different crack quality categories was first presented. Extensive parametric analyses and discussions were carried out for different weld types (full penetration and partial penetration), characterized crack types (through-width and semi-elliptical cracks), and loading patterns. A comparison of the calculated values of the stress magnification factor with those in the current standard, BS 7910, revealed that, in most cases, the calculated values exceeded the acceptable limits provided by the code. Parametric equations for the stress magnification factor were subsequently proposed based on multiple regression analysis, and statistical analysis was conducted to verify the goodness of fit of these formulas. Finally, the fatigue strength curves required for different survival probabilities were compared with the test data of welded joints to assess the applicability of the quality category approach considering the misalignment. On this basis, the tolerance limits of axial and angular misalignments were given for welded joints of different quality categories.