Effect of Surface Roughness on Fatigue Crack Initiation in Additive Manufactured components with Integrated Capillary for SHM Application

Additive Manufacturing is considered as one of the most promising manufacturing technologies currently studied, but the unrepeatable material behaviour and lack of proper process control still form major challenges to become widely used in aeronautical applications. Structural Health Monitoring (SHM) systems can ensure safe operation by monitoring the structural integrity of the additive manufactured components. In that perspective, a SHM strategy for additive manufactured components is proposed whereby capillaries are integrated during the production of the component. Being pressurized at a pressure different than the ambient conditions and by continuously monitoring the capillary pressure, one can derive the presence of fatigue cracks that have breached the capillary: the crack forming the connection between the outside and the capillary network. However, fatigue strength and fatigue crack initiation must not be altered by the presence of the capillaries of the SHM system. The current work analyses the effect of the presence of printed and drilled capillaries on the fatigue strength and initiation location in conventional and additive manufactured Ti6Al4V samples. All samples are tested using 4point bending tests. Despite the fact that additive manufactured samples without capillary outperformed conventional material in terms of fatigue strength, it was observed that the presence of printed capillaries reduced the fatigue strength of the specimen. Analysis has shown that the capillary surface roughness leads to stress concentrations which alter the fatigue initiation location to the capillary surface and reduce its fatigue strength.

Jaar van publicatie:2017

Trefwoorden:Fatigue, Additive Manufacturing, Ti-6Al-4V, eSHM, surface roughness