Capacity of Fillet Welded Joints Made of Ultra High-Strength Steel

The ultimate load-bearing capacity of typical fillet welded joints made of ultra high-strength steel (UHSS) S960 has been investigated. The aim of the work has been to assess the validity of current design rules for UHSS and possibly define new design criteria. Experimental testing and nonlinear finite element analysis (FEA) were applied to define the capacity of fillet welded joints. Joint geometries and material properties were measured for both filler and base materials. In comparison with current design rules, the experimental results showed that the fillet welded joints had adequate load-carrying capacity presuming that adequate weld quality is achieved in the joint fabrication. Load-carrying capacities and rupture modes in welds defined by FEA were in agreement with experimental results. The experimental deformation capacities of some of the joints were found to be critical, but the capacities can be improved by the use of undermatched filler metals. Heat input control is essential in the fabrication of welded connections made of UHSS and thus an additional failure criteria should be considered in design codes due to the softening effect in HAZ.