Design, manufacturing, and fatigue performance of directed energy deposited beam-to-column connection for marine applications

Abstract Ship structures feature complex fatigue critical details. Directed energy deposition (DED) could be used to manufacture the details. When DED components are connected to the surrounding structure, the cost could be significantly reduced in comparison to dedicated additive manufacturing. This study presents the case using DED component as part of a load-bearing structure, designing and performing DED manufacturing and joining the component to the structure for I-beam, pillar, and deck connection. Design work for the structural load-bearing capacity was conducted, and based on the obtained geometry, DED manufacturing was designed. Finally, a fatigue test for the structure was performed and followed by quality and performance analysis including SEM fractography comparison to camera-based deposition monitoring. A local imperfection between the deposition layers was found as an initiation point for the fatigue cracking. After considering wall thickness reduction due to imperfection, the fatigue strength of DED component in the full-scale test was found to exceed design curve FAT 100 MPa m = 5, extracted using the previously defined small-scale coupon test data. From the fatigue strength perspective, DED hybrid components could be recommended for fatigue-critical applications.