Review of the Definition of Weld Penetration, Depth of Fusion and Throat Thickness on Fillet Welds

In this study, definitions of Weld Penetration (WP), Depth of Fusion (DOF) and Throat Thickness (TT) in fillet welds according to related standards are reviewed. WP, DOF and TT are crucial dimensions for welded joints since these values determine the weld quality. In AWS A3.0, ISO2553, Eurocode EN 1993-1-8 and DIN EN ISO 17659, these terms are defined, explained and shown in figures. Each standard makes its own definition related with WP, DOF and TT. Moreover, when looking at these standards, it is seen that definitions are always made in terms of unit of length. In some studies, assessment of fusion or penetration (FOP) rate on fillet welds is performed as the ratio of the maximum FOP depth to the material thickness. Depth assessment taking into consideration unit of length is not ideal for accurate evaluation of FOP rates especially on fillet welds. Method taking into consideration unit of area will be more suitable as it allows accurate assessment of FOP rates in welded joints. In this review, it is also suggested that the evaluation of FOP rate on fillet welds should be determined in terms of unit of area rather than length.