The roles of inspection, flaw characterization and material properties in FFS assessment were detailed in previous hot topic articles. Local stress concentrations may also exist. The applied stresses can be either primary or secondary. Secondary stresses are those which are self equilibrating. Hence, secondary stresses cannot contribute to plastic collapse of the structure.
Applied loading is obviously primary, weld residual stresses are secondary.
The magnitude of residual stresses can have a significant impact on the FFS assessment of planar flaws. In as-welded components, the residual stresses in the vicinity of the weldment approach the yield strength of the material. In these cases the residual stresses typically dominate the FFS assessment and serve as the controlling parameter. These first level approximations can be applied if the flaws are within the plate thickness or 13 mm of the fusion boundary. Upper bound estimates or actual values of yield strength should be assumed.