Multi-Scale Modeling and Multi-Objective Design Framework for Location-Specific Material Behavior in Additively Manufactured Components

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Additive manufacturing (AM) processes for metallic materials, namely powder-bed fusion, and various powder-feed and wire-feed systems, are bringing dramatic changes to the manufacturing industry. The unprecedented agility achieved through layer-by-layer material addition is enabling near net-shape production of complex components. Despite this promise and progress, the qualification and acceptance of AM parts have been compromised by the lack of consistency in material behavior and life-limiting properties, e.g., undesirable ductility and fatigue behavior. These inconsistencies are often attributed to subtle, yet characteristic variations in the microstructure (morphology and defect structure), possibly a consequence of small perturbations in the AM process parameters. By implementing a multi-pronged approach incorporating innovative methods of integrated computational materials engineering (ICME), such as physics-based multi-scale modeling, multi-objective design, and materials characterization and testing, this research will address this shortcoming by developing a robust framework for location specific material properties and behavior in structures fabricated by AM processes. Ultimately, it will provide guidance on the links between process parameters and product performance and life, paving the acceptance of AM parts in critical applications. The research will promote the sciences associated with ICME; advance the national health, prosperity, and welfare by establishing the provenance of AM manufacturing; and secure the national defense by enabling near on-demand, net-shape production of critical parts in theaters. Collaborative partnerships with Sandia National Laboratories and JHU/Applied Physics Laboratory will be a strength of this research. Graduate students on this project will undergo multi-disciplinary training in state-of-the-art techniques in multi-scale modeling, design optimization, materials characterization and modern manufacturing processes. The collaboration with Sandia and JHU/APL will also provide them exposure to the most advance technological advancements that will help their professional career development. Two specific developmental modules will be realized for AM processed metals and alloys with polycrystalline-polyphase microstructures. They are: (i) development and implementation of parametrically homogenized constitutive/damage models (PHCMs) with explicit representation of microstructural descriptors in the form of representative aggregate microstructural parameters or (RAMPs), and (2) development of PHCM-based robust design methods for location-specific material design in structures designed, e.g., by topology optimization. Furthermore, PHCM-based simulations readily estimate the effect of variations in the microstructure on structure-scale variables like stresses, strains, strength, and even ductility or fatigue life. This will facilitate sensitivity analysis in location-specific material design in AM processed structures that have been conceptualized by design methods like topology optimization. A multi-objective function framework will be incorporated for identifying a Pareto front, defining the achievable cross-property space. The outcome of the detailed material design undertaking will be a structural-scale layout of the microstructure (in terms of RAMPs) for a robust, site-dependent distribution of macro-scale properties. This will guide the selection of AM processes parameters and routes to improve structure-material performance and life.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.