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Additive manufacturing: Toward holistic design

Scripta Materialia

Jared, Bradley H.; Aguilo, Miguel A.; Beghini, Lauren L.; Boyce, Brad B.; Clark, Brett W.; Cook, Adam W.; Kaehr, Bryan J.; Robbins, Joshua R.

Additive manufacturing offers unprecedented opportunities to design complex structures optimized for performance envelopes inaccessible under conventional manufacturing constraints. Additive processes also promote realization of engineered materials with microstructures and properties that are impossible via traditional synthesis techniques. Enthused by these capabilities, optimization design tools have experienced a recent revival. The current capabilities of additive processes and optimization tools are summarized briefly, while an emerging opportunity is discussed to achieve a holistic design paradigm whereby computational tools are integrated with stochastic process and material awareness to enable the concurrent optimization of design topologies, material constructs and fabrication processes.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI

Topology Optimization of Cellular Structure

Robbins, Joshua R.; Owen, Steven J.; Clark, Brett W.; Voth, Thomas E.

This paper presents an end-to-end design process for compliance minimization based topological optimization of cellular structures through to the realization of a final printed product. Homogenization is used to derive properties representative of these structures through direct numerical simulation of unit cell models of the underlying periodic structure. The resulting homogenized properties are then used assuming uniform distribution of the cellular structure to compute the final macro-scale structure. A new method is then presented for generating an STL representation of the final optimized part that is suitable for printing on typical industrial machines. Quite fine cellular structures are shown to be possible using this method as compared to other approaches that use nurb based CAD representations of the geometry. Finally, results are presented that illustrate the fine-scale stresses developed in the final macro-scale optimized part and suggestions are made as to incorporate these features into the overall optimization process.

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TYPE Journal Article YEAR 2015
OSTI

Wave propagation and dispersion in elasto-plastic microstructured materials

International Journal of Solids and Structures

Dingreville, Rémi; Robbins, Joshua R.; Voth, Thomas E.

A Mindlin continuum model that incorporates both a dependence upon the microstructure and inelastic (nonlinear) behavior is used to study dispersive effects in elasto-plastic microstructured materials. A one-dimensional equation of motion of such material systems is derived based on a combination of the Mindlin microcontinuum model and a hardening model both at the macroscopic and microscopic level. The dispersion relation of propagating waves is established and compared to the classical linear elastic and gradient-dependent solutions. It is shown that the observed wave dispersion is the result of introducing microstructural effects and material inelasticity. The introduction of an internal characteristic length scale regularizes the ill-posedness of the set of partial differential equations governing the wave propagation. The phase speed does not necessarily become imaginary at the onset of plastic softening, as it is the case in classical continuum models and the dispersive character of such models constrains strain softening regions to localize. © 2014 Elsevier Ltd. All rights reserved.

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TYPE Conference Poster YEAR 2014
ScopusOSTI

LDRD final report : mesoscale modeling of dynamic loading of heterogeneous materials

Robbins, Joshua R.; Dingreville, Remi P.; Voth, Thomas E.; Furnish, Michael D.

Material response to dynamic loading is often dominated by microstructure (grain structure, porosity, inclusions, defects). An example critically important to Sandia's mission is dynamic strength of polycrystalline metals where heterogeneities lead to localization of deformation and loss of shear strength. Microstructural effects are of broad importance to the scientific community and several institutions within DoD and DOE; however, current models rely on inaccurate assumptions about mechanisms at the sub-continuum or mesoscale. Consequently, there is a critical need for accurate and robust methods for modeling heterogeneous material response at this lower length scale. This report summarizes work performed as part of an LDRD effort (FY11 to FY13; project number 151364) to meet these needs.

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TYPE SAND Report YEAR 2013
OSTIDOI
Results 26–50 of 69
Results 26–50 of 69