Fatigue strength behaviour of stud-arc welded joints in load-carrying ship structures

The application of stud-arc welding to cyclic loaded primary ship structures was investigated. Thereby M8- and M12 studs were welded on the bulb of Holland profiles using the drawn stud-arc welding with ceramic ferrules. Several fatigue tests were performed, varying the stiffener size, the stud diameter, its position on the bulb, the welding position, weld parameters, residual stress state and the static load in the stud. The obtained fatigue strength is above FAT 80 and only slightly affected by these factors. Hence, the investigated stud-arc welding can be applied at Holland profiles in primary ship structures, provided the quality criteria are met. In order to transfer the results to other geometries and load situations, the applicability of the effective notch stress approach was investigated. The corresponding finite element calculations using idealized weld shapes and a reference weld toe radius of 1 mm showed an insignificant influence of the weld geometry on the notch stress. The determined notch stresses for each test series was above the design S-N curve FAT 225 for the notch stress approach and make it also applicable to stud-arc welding. Further computations were performed using the real weld profile and the stress-averaging approach by Neuber, showing similar results.