Ultrasonic fatigue response of vertically and horizontally printed Ti-6al-4v and Inconel 718.

Abstract

This study investigates the effect of build orientation (vertical vs. horizontal) on the me-chanical behaviour and ultrasonic fatigue testing (UFT) performance of additively manufac-tured Ti‑6Al‑4V and Inconel 718 specimens. Additive manufacturing (AM) is known to introduce anisotropic microstructures, with orientation, defects, and process conditions sig-nificantly influencing fatigue strength [1]. In particular, layer orientation affects both ten-sile and fatigue properties [2]. Five specimens per alloy were produced in each orientation and tested using UFT at 20 kHz. System calibration was supported by Digital Image Corre-lation (DIC) and laser measurements to reduce data scatter in the high-cycle regime [3]. Mechanical properties including Young’s modulus, Poisson’s ratio, and stress–strain re-sponse were determined for both orientations. Combining Finite Element Analysis (FEA), DIC, and analytical/statistical methods enhanced confidence in interpreting deformation and stress behaviour. Results showed orientation-dependent differences. Horizontally built specimens generally exhibited longer fatigue lives and greater stiffness along the loading axis, consistent with prior findings [2]. While the combined methods were effective in as-sessing global stress behaviour, further work is needed to resolve layer-induced effects con-tributing to anisotropy.