Novel specimen geometries for fatigue testing of additive manufactured metals under axial, torsion, and combined axial-torsion loadings

Abstract

Using the geometric freedom offered by additive manufacturing, a plate-type specimen geometry for axial fatigue testing, a hollow cylindrical specimen for torsion testing, and two thin-walled circular cross section specimens for torsion or axial-torsion fatigue testing are proposed. The proposed geometries reduce the stress concentration at the gage-to-grip transition area, improve the uniformity of the shear stress distribution throughout the wall thickness, and increase buckling resistance during the compression part of the loading cycle. Some preliminary fatigue test results conducted with the proposed specimens are presented and the results are compared with the conventional ASTM tubular specimen.