Torsional and axial tension/compression fatigue behavior of Ti-6Al-4V diamond lattices produced by Laser Powder Bed Fusion (LPBF)

The increasing importance to characterize additively manufactured lattice structures in different load regimes cannot be overemphasized due to their robust load bearing applications in lightweight structural parts or biomedical implants. This study investigates the torsional fatigue behavior of metallic diamond cell structures to check the mean stress sensitivity of these meta-materials. Consistency in results for torsional fatigue is achieved by a unique sample design that minimizes stress concentration, is self-centering and graded. In addition, axial fatigue in tension–tension, compression–compression and tension–compression is studied. The tensile mode is found to be most detrimental to fatigue life of all axial modes. An analytical local stress method (LSM) is presented to estimate the maximum local stresses that occur in the structure. By using this approach, axial tension/compression and torsion fatigue experiments almost fall together due to the similar maximum local stress. Reverse calculations from these local stress curves can provide valuable insight into torsional strength when data are available only for axial fatigue tests.