The overall objective within the subproject of the DFG Research Unit 5250 on “Mechanism-based characterization and modeling of permanent and bioresorbable implants with tailored functionality based on innovative in vivo, in vitro and in silico methods” is the holistic characterization of the microscopic and mechanical deformation and damage behavior under cyclic loading as well as corrosive exposure of Ti-6Al-4V lattice structures additively manufactured (AM) by means of PBF-LB/M and PBF-EB/M. The aim is to establish an extensive understanding of the mechanical and corrosive properties for the simplified 2D geometry which will then be transferred towards 3D lattice structures. To characterize the application-oriented damage behavior, in-vitro corrosion fatigue tests for 3D lattice structures will be conducted.
At first, the effect of surface roughness was investigated based on bulk Ti-6Al-4V material. The surface roughness as well as the effective bearing cross-section was quantified by computer tomography (CT). Based on this, a direct comparison and evaluation of the roughness effect was possible without taken the influence of cross-section into account. Moreover, an application-optimized instrumentation consisting of digital image correlation (DIC), quantitative acoustic emission (AE) analysis and infrared thermography (IRT) was used for lattice structures of Ti-6Al-4V. The localization of damage was detected by DIC and IRT, while the cascade-like damage evolution from strut to strut could be monitored by each measurement technique. Especially the integral AE analysis offers the possibility to be used as condition monitoring system for complex lattice AM structures and components. Moreover, selected in situ CT tests were performed on the lattice structures and analyzed by digital volume correlation (DVC) for identification of deformation hotspots as well as crack initiation and failure prediction.
Examples are presented to reveal the potential to enhance the reliability of AM lattice structures and components design based on comprehensive defect-microstructure-property relationships to be integrated in robust modelling approaches.

Acknowledgements

The authors gratefully acknowledge the funding by the German Research Foundation (DFG) for the subproject SP-3 within the Research Unit FOR 5250 “Permanent and bioresorbable implants with tailored functionality” (No. 449916462).