PSI - Issue 83

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 83 (2026) 239–245

© 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Abstract In the present study, the step-loading (SL) approach introduced by Nicholas was examined as a fast method for estimating the fatigue strength of Ti-6Al-4V gyroid lattices produced by PBF-LB at four relative densities: 12.5%, 25%, 37.5%, and 50%. Step loading experiments were carried out using loading blocks of one million cycles, and the resulting fatigue-strength estimates were compared with values extracted from the corresponding S-N data at one and two million cycles. At one million cycles, the SL/S-N ratios increased from 0.86 to 0.96 as RD increased, showing that the accuracy of the SL method improved for denser lattices. At two million cycles, the ratios remained close to unity, ranging from 0.98 to 1.02. These findings indicate that the SL method can be used as an efficient tool for fatigue-strength assessment of gyroid lattices, while its accuracy is influenced by lattice relative density and by the damage accumulated during the preceding loading blocks. The fourth European Conference on the Structural Integrity of Additively Manufactured Materials (ESIAM26) Fatigue strength estimation of Ti-6Al-4V gyroid lattices via step-load testing Amir Hossein Mirzaei, Nima Razavi* Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Richard Brikelands vei 2b, 7491 Trondheim, Norway

Peer-review under responsibility of the scientific committee of the ESIAM26 organizers Keywords: Additive manufacturing; Gyroid lattices; Step-loading method; Fatigue strength.

1. Introduction Additively manufactured (AM) metallic components frequently exhibit larger scatter in fatigue performance than conventionally manufactured counterparts, because the layerwise fabrication route can introduce microstructural

* Corresponding author. E-mail address: nima.razavi@ntnu.no

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the ESIAM26 organizers 10.1016/j.prostr.2026.07.027