Additive Manufacturing: Mechanical Behavior of Lattice Structures Produced via AM: Additive Manufacturing of Lattices - Session III
Sponsored by: TMS: Additive Manufacturing Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: John Carpenter, Los Alamos National Laboratory; Matthew Begley, University of California, Santa Barbara; Sneha Prabha Narra, Carnegie Mellon University; Michael Groeber, Ohio State University; Isabella Van Rooyen, Pacific Northwest National Laboratory; Kyle Johnson, Sandia National Laboratories; Krishna Muralidharan, University of Arizona
Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 4
Location: MS&T Virtual
Session Chair: Kyle Johnson, Sandia National Laboratory; Matthew Begley, University of California - Santa Barbara
2:00 PM Invited
Predicting Interfacial Cracking between Solid and Lattice Support Structure during Laser Powder Bed Fusion Processing: Hai Tran1; Xuan Liang1; Albert To1; 1University of Pittsburgh
For laser powder bed fusion (L-PBF) additive manufactured (AM) metals, residual stress-induced cracking often occurs at the interface between the solid and lattice support structure, and hence it is important to characterize the as-built critical J-integral of the interface to prevent cracking to occur. For this reason, an effective method that combines printing experiments and residual stress simulation is proposed to determine the as-built critical J-integral of the interface. First, a number of rectangular block specimens with lattice supports of identical height overlaid by solids of different heights are built by L-PBF in Inconel 718 in order to determine the critical height that the block would crack. Next, the experimentally-validated modified inherent strain method is utilized to simulate residual stress and compute the critical J-integral at where the interfacial cracking occurs. The proposed method is subsequently validated using the obtained critical J-integral to predict cracking in different geometries.
2:30 PM
Residual Stress Mitigation in Lattice Structures Built by Laser Powder Bed Fusion: Anna Hayes1; Rachel Gorelik1; Krishna Muralidharan1; 1The University of Arizona
Laser powder bed fusion (LPBF) additive manufacturing offers unprecedented design freedom including the fabrication of technologically relevant lightweight, topologically optimized lattice structures. A limitation in the LPBF process however, is the lack of control over residual stress, negatively affecting mechanical properties and geometrical accuracy. In this regard, using thermomechanical modeling as the primary investigative tool and Inconel 718 as the material of choice, the effect of part geometry, strut diameter, and lattice type on developed residual stress and part distortion is examined. Particular attention is paid to heat accumulation and thermal gradients within the fabricated part and their interplay with residual stress. Using these models as the basis, recommendations are provided for LPBF processing parameters to limit residual stress within topologically optimized lattice structures, which are experimentally verified via targeted fabrication of such structures.
2:50 PM Invited
Predicting the Response of Additively Manufactured IN625 Thin-walled Elements: Arunima Banerjee1; Sara Messina2; Jeff Rossin2; Edwin Schwalbach3; William Musinski3; Paul Shade3; Marie Cox3; Mo-Rigen He1; Tresa Pollock2; Matthew Begley2; Kevin Hemker1; 1Johns Hopkins University; 2University of California, Santa Barbara; 3Air Force Research Laboratory/RXCM
Additive manufacturing has opened new pathways for the fabrication of materials and components with complex geometries. Predicting mechanical response of builds with traditional design tools is complicated by the inhomogeneity and anisotropy of the properties. This study aims to measure and understand the processing-dependent microstructure and mechanical response of thin-walled elements of Inconel 625 fabricated by powder bed printing. DIC strain mapping and finite element analysis is combined to study the effect of geometry, print conditions and location specific properties on the mechanical performance of T-shaped elements. The results indicate that plasticity is concentrated at the nodes of the elements and these nodes govern the overall deformation. Evidence of anisotropic plasticity is documented in as-built parts and EBSD analysis allows for characterization of underlying texture effects. The overarching goal of this study is to develop a methodology that allows for better design and modeling of additively manufactured thin walled structures.