Fatigue behaviour of laser beam welded circular weld seams under multi-axial loading

With modern laser beam sources welding processes can be developed, that allow the joining of otherwise barely realisable material and geometrical constellations such as dissimilar welded, thick-walled shaft-hub joints for powertrain systems. Current design recommendations do not offer solutions to account for the cyclic strength under torsional loading for welded structures. In order to bridge the gap between cost and time consuming prototype testing and laboratory tests of basic homogeneous material samples, a test system combining axial and torsional loading was used. For this purpose application oriented test parts are designed to mimic the weld seam geometry, stiffness and heat dissipation conditions of the real structural part at its best. The dissimilar joints were realised for two material combinations: cast iron GJS-600-3 with case hardened steel 16MnCr5 and 42CrMo4 with 16MnCr5. The latter combination showed only a slightly higher cyclic strength compared to the cast iron/steel combination. A systematic optimization of the laser beam welding process leads to a fatigue behaviour under multi-axial loading conditions, where the cast iron/case hardened steel combination still met the strength specification required.