Production Assessment of Hybrid Directed Energy Deposition Manufactured Sample with Integrated Effective Structural Health Monitoring channel (eSHM)

Additively manufactured components are questioned for their fatigue performance and therefore not adopted for safety critical applications so far. The components might contain material imperfections and residual stresses due to the high temperature gradients during the printing process. These stresses alter the component's structural integrity and are one of the main sources of component deformation and cracking. The effective Structural Health Monitoring system (eSHM), developed and patented by the Vrije Universiteit Brussel, fully exploits the flexibility offered by the 3D printing process by integrating a smart continuous monitoring technology inside additively manufactured parts. The system is based on the detection of pressure changes in 3D-curved internal channels embedded in the fatigue critical regions of the component. The pressure is continuously monitored at the channel extremities by externally mounted pressure sensors. The system is capable of detecting the presence and finding the location of a fatigue crack. This paper proposes an assessment of the production of a fatigue sample with integrated eSHM-system using the MiCLAD in-house hybrid Directed Energy Deposition machine developed by the Additive Manufacturing Research Group of the VUB. It has the particularity to allow the combination of both additive and subtractive milling operations for the production of a part. Different printing strategies are presented and compared in terms of final geometry and internal channel roughness, known to be crucial to avoid undesired fatigue initiation and to obtain an accurate detection and localization of the fatigue crack. The encountered difficulties during the production process are identified and solutions are proposed.