Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Lattice Structures and Miscellaneous I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Andrew Birnbaum, Us Naval Research Laboratory; Robert Lancaster, Swansea University; Xinghang Zhang, Purdue University; Aeriel Leonard
Wednesday 2:00 PM
March 22, 2023
Room: 23B
Location: SDCC
Session Chair: Mohsen Mohammadi, University of New Brunswick; Jordan Weaver, NIST
2:00 PM Invited
Invited: Multiscale Phenomena to Inspire Lattice Structures Design: Kavan Hazeli1; 1University of Arizona
Most of the natural structures, which have been an influential source of inspiration for hierarchical materials design do not have grain structures resembling those that are seen in metals. Therefore, designing bio-inspired metallic materials with hierarchical structures such as additively manufactured lattice structures has been lacking in benefiting the property of grain structures. This presentation demonstrates that simultaneously considering the effects of topology and microstructure on the mechanical behavior of AMLS has the potential to substantially improve key performance metrics, e.g., energy dissipation. The distinguishing feature of our approach is that the topological optimization is performed while accounting for the heterogeneous distribution of strut-level microstructure concomitant mechanical behavior leading to peak AMLS structural performance. A new set of new topologies are designed, built, and validated against experiments. The new topologies demonstrate over 50% improvement in energy absorption capacity of topologies that had been previously optimized using a homogeneous constitutive model.
2:20 PM
Single-point Laser Scanning Strategy for the SLM Fabrication of Ti-6AL-4V Micro-strut Lattices: Strut Size Dependent Mechanical Properties: Conor Okeeffe1; D Kelly1; 1Trinity College Dublin
Porous metallic scaffolds fabricated by AM offer benefits that have been identified as advantageous over their parent bulk material. The mechanical properties of the individual struts making up these lattices can be significantly different from the bulk material. For the traditional 'contour-and-hatch' laser scanning strategy, these changes have been related to features inherited from the fabrication process. However, this work has not been extended to the ‘single-point’ based strategy; which has been suggested as more suitable for the fabrication of such small feature-size lattice structures. In this approach, strut thickness is determined by melt pool thickness defined at a single exposure point for each build layer; offering the potential for a smaller minimum feature size.Here we are seeking to 1.) define this strategy for fabrication of a range of strut sizes and 2.) characterize changes in mechanical properties of the induvial struts across this range.
2:40 PM
Investigating the Influence of Grain Boundary Strengthening Assumptions on the Lattice Strain Evolution in Additively Manufactured IN718: Jason Mayeur1; 1Oak Ridge National Laboratory
Additively manufactured components have substantially different microstructures than wrought or cast components. One of the key differences between conventionally and additively manufactured metals and alloys is the grain morphology, with the former often being nearly equiaxed whereas the latter often exhibits high aspect ratio grains with multimodal size distributions. Computational modeling is often used in conjunction with experimental measurement and characterization to establish microstructure-property relationships for materials. In order for mesoscale models to provide meaningful quantitative results, these differences in microstructure must be accounted for when constructing statistically equivalent ensembles from experimental data for use as input to simulation codes. In this study, we examine different approaches for: i) creating statistical volume elements for AM materials from EBSD data and ii) representing grain boundary strengthening for heterogeneous grain morphologies and its influence on the deformation behavior of IN718 produced via laser powder bed fusion using FFT crystal plasticity simulations.
3:00 PM
Effects of Topology on the Compressive Creep Rate of Inconel 625 FCCZ Lattices: Kaitlynn Conway1; Hamid Torbati-Sarraf2; Thomas Berfield3; Garrett Pataky4; 1Sandia National Laboratories; 2Purdue University; 3University of Louisville; 4Clemson University
Metamaterials have demonstrated great specific strength properties, ideal for multifunctional opportunities within aerospace and energy generation industries. However, the high temperature properties of metamaterials are not yet well understood to begin to fully incorporate within load bearing applications. This study experimentally examined the compressive creep rates of additively manufactured Inconel 625 solid specimens and single-cell lattice metamaterial specimens to determine differences in the failure mechanisms. The initial microstructures and defects were analyzed via EBSD and XCT before high temperature testing. The lattice topology was shown to drive the compressive creep rate rather than the base material, by nearly two orders of magnitude. Rupture time was dependent on the relationship between initial load and temperature, with all lattice specimens failing in a buckling fashion.
3:20 PM
Toughness Amplification in Bioinspired Nanoarchitectured Materials: Zainab Patel1; Lucas Meza1; 1University of Washington
Natural materials display high strength and toughness due to material interactions at the micro- and nanoscale, but it has been challenging to quantify materials at these length scales experimentally. This work demonstrates a strategy to study microscale toughness in a novel nanoarchitected material. We use two-photon lithography to create polymeric microscale bouligand-style beams with sub-micron features in a single-edge notch three-point bend setup and use in-situ nanomechanical testing to analyze their fracture characteristics. Using the J-integral method, we quantify the crack growth resistance as a function of architecture and density. Specimens demonstrate delayed crack initiation, higher normalized J toughness, and a significant enhancement in energy dissipation with increasing twist angles providing fundamental insight into the effect of architectural tortuosity on fracture processes. This combined understanding of the effect of architecture and specimen length scale on toughness is crucial to developing new methods to engineer tough, lightweight materials at the macroscale.
3:40 PM Break
4:00 PM Invited
Topological Homogenization of Metamaterial Variability: Benjamin White1; Anthony Garland1; Brad Boyce1; 1Sandia National Laboratories
Lattices contain thousands or even millions of complex features, each with imperfections in shape and material constituency. While the role of these defects on the mean properties of metamaterials has been well studied, little attention has been paid to the stochastic properties of metamaterials, a crucial next step for high reliability aerospace or biomedical applications. In this work we show that it is precisely the large quantity of features that serves to homogenize the heterogeneities of the individual features, thereby reducing the variability of the collective structure and achieving effective properties that can be even more consistent than the monolithic base material. The variability in yield strength and modulus was observed to exponentially decrease with feature count (to the power −0.5), a scaling trend that we show can be predicted using an analytic model or a finite element beam model. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
4:20 PM
New Insights on Dislocation Barrier Effect of the Cellular Subgrain Feature in Directed Energy Deposited SS 316L: Janith Wanni1; Ajith Achuthan1; 1Clarkson University
The studies of local deformation under uniaxial tensile loading of the directed energy deposited stainless steel 316L have shown that cellular subgrain feature introduces barrier effect. The barrier effect manifests as a microscopic surface texture and slip band refinement producing exceptional mechanical properties. With the objective of deriving a comprehensive understanding of the mechanism responsible for the barrier effect, an extensive nanoindentation study was performed. The variations of nano-hardness and load-depth behavior across a representative region on the specimen surface is investigated. The results show that these characteristics have a bi-modal distribution consistent with the cellular subgrain feature morphology. The material behavior in the cell interior exhibits lower strength and higher plasticity compared to the behavior exhibited by the regions around the cell walls. A relationship between the bulk mechanical response of the material and the local mechanical responses of cell interior and cell walls was derived.
4:40 PM
Interlocking Metasurfaces: An Additive Enabled Joining Technology: Ophelia Bolmin1; Benjamin Young1; Philip Noell1; Brad Boyce1; 1Sandia National Laboratories
Interlocking metasurfaces (ILMs) are architected arrays of mating features that enable joining of surfaces. While ILM topology and materials have previously been restricted to microfabrication techniques, recent advances in additive manufacturing technology open up a new design space for ILMs. In this talk, we demonstrate how AM enables the rapid exploration of the design space across scales. Several designs are manufactured in polymers and metals. The performance of selected designs is simulated and experimentally characterized under static loading and in vibration. The designs create robust mechanical attachment solutions that can enable the assembly of additively manufactured parts. <br>Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.
5:00 PM
Interlocking Metasurfaces: Stronger than the Sum of their Parts: Benjamin Young1; Ophelia Bolmin1; Brad Boyce1; Philip Noell1; 1Sandia National Laboratories
Advances in additive manufacturing technologies and limitations in build space have spurred an increased interest in modular architectures. Traditional joining techniques can run into complications when used to join complex printed structures, such as lattices. In this work, we experimentally characterize the performance of different array configurations of interlocking metasurfaces (ILMs). ILMs are architected arrays of latching features that create non-permanent joints that can be directly integrated into the components to be joined. These ILMs can be intelligently architected to form structurally robust joints. Understanding the mechanical behavior of these interlocking surfaces will clarify the design space that ILM’s occupy, and their strengths and weaknesses as a versatile joining technology.<br>Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.