Developing a Crystal Plasticity Model for Metallic Materials Based on the Discrete Element Method
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Developing a Crystal Plasticity Model for Metallic Materials Based on the Discrete Element Method Agnieszka Truszkowska1,2, Qin Yu1, Peter Alex Greaney3, T. Matthew Evans2, Jamie J. Kruzic4 1
School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, USA 2 School of Civil and Construction Engineering, Oregon State University, Corvallis, USA 3 Department of Mechanical Engineering, University of California Riverside, Riverside, USA 4 School of Mechanical and Manufacturing Engineering, UNSW Sydney, Sydney, Australia ABSTRACT Failure of metallic materials due to plastic and/or creep deformation occur by the emergence of necking, microvoids, and cracks at heterogeneities in the material microstructure. While many traditional deformation modeling approaches have difficulty capturing these emergent phenomena, the discrete element method (DEM) has proven effective for the simulation of materials whose properties and response vary over multiple spatial scales, e.g., bulk granular materials. The DEM framework inherently provides a mesoscale simulation approach that can be used to model macroscopic response of a microscopically diverse system. DEM naturally captures the heterogeneity and geometric frustration inherent to deformation processes. While DEM has recently been adapted successfully for modeling the fracture of brittle solids, to date it has not been used for simulating metal deformation. In this paper, we present our progress in reformulating DEM to model the key elastic and plastic deformation characteristics of FCC polycrystals to create an entirely new crystal plasticity modeling methodology well-suited for the incorporation of heterogeneities and simulation of emergent phenomena. INTRODUCTION Improving the accuracy and predictive power of solid deformation models will require inclusion of the underlying micromechanical phenomena of deformation and failure. Such micromechanistic models could help address outstanding issues in the mechanics of materials, such as estimating a material’s lifespan [1]. The discrete element method (DEM), originally developed for granular mechanics [2], has potential to provide a robust framework for such models. DEM is inherently heterogeneous in structure and local properties and the simulated elements are distinct entities. Like other discrete methods [3], DEM can readily model the emergence of discontinuities, such as cracks, in a material, which can be challenging for continuum methods, requiring increased complexity and computational cost [4]. Finally, the DEM formulation is similar to molecular dynamics, thus creating possibilities for straightforward implementation of atomistic findings in a macroscale deformation model. In this regard, DEM can serve as a mesoscale modeling method between atomistic and macroscopic whereby each element represents a domain of material consisting of many atoms while maintaining varying levels of local and micromechanical heterogeneity. To date, DEM has been successful in modeling various plasticity and dam
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