Integration between Modeling and Experiments for Crystalline Metals: From Atomistic to Macroscopic Scales: Session IV
Program Organizers: M Arul Kumar, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Levente Balogh, Queen's University; Josh Kacher, Georgia Institute of Technology; Caizhi Zhou, Missouri University of Science and Technology; Lei Cao, University of Nevada, Reno

Wednesday 8:00 AM
October 2, 2019
Room: G132
Location: Oregon Convention Center

Session Chair: M Arul Kumar, Los Alamos National Laboratory; Philip Eisenlohr, Michigan State University

8:00 AM  Invited
ICME at the Mesoscale: Computational and Experimental Challenges and Opportunity: Stephen Niezgoda1; Pengyang Zhao1; Yunzhi Wang1; Michael Mills1; Connor Slone1; Supriyo Chakraborty1; 1Ohio State Univ
    One strategy for reducing the burden of inserting new materials and processes is the adoption of Integrated Computational Materials Engineering (ICME), which is predicated on replacing expensive experimentation with modeling and simulation. The critical question with ICME adoption is “How do we develop sufficient statistical confidence in a simulation with only limited experimental validation?” In this talk the opportunities and challenges of integrating mesoscale modeling and simulation into ICME are explored. Specifically recent advances related to i) Physics-based microstructure and mesoscale constitutive theory, ii) Computationally efficient numerical solvers for meso-mechanical constitutive models, iii) Rigorous methodologies for model verification and validation (V&V) coupled with uncertainty quantification (UQ), and iv) Advanced characterization techniques to quantify the mesoscale mechanical response of the material and the associated evolution of microstructure will be presented and put in context of the needs of ICME adoption.

8:30 AM  Invited
Micromechanics – Crystal Plasticity Links for Deformation Twinning: Yubraj Paudel1; Christopher Barrett1; Haitham El Kadiri1; 1Mississippi State University
    Current crystal plasticity finite element models show limited capability to incorporate the essential characteristics of twinning. These include rapid propagation of twins across the low-angle grain boundary (autocatalysis), localized stress-strain behavior, and twinning-induced microstructure within a single grain as seen in experimental results. A Micromechanics-based study of twinning under three point bending showed characteristic twin spacing is a function of twin height and stress relaxation is a function of twin thickness. Likewise, experimental observations on the evolution of twinning allowed us to build a strategy to incorporate a characteristic twin spacing parameter in the crystal plasticity framework. Inspired by results from molecular dynamics (MD) simulations stressing the effect of shuffles on twin nucleation and disconnection core width, we implemented an explicit twinning nucleation criterion based on hydrostatic stress gradient, volume fraction of twins inside a grain and characteristic twin spacing to determine site-specific nucleation points in complex twinning scenarios.

9:00 AM  
Multiscale Modeling of the Elasto-plastic Behavior of Architectured and Nanostructured Cu-Nb Composite Wires and Comparison with Neutron Diffraction Experiments: Tang Gu1; David McDowell1; 1Georgia Institute of Technology
    Nanostructured and architectured copper niobium composite wires are excellent candidates for the generation of intense magnetic fields (100T) as they combine both high strength and high electrical conductivity. Multi-scaled Cu-Nb wires are fabricated by accumulative drawing and bundling (a severe plastic deformation technique), leading to a multiscale, architectured, and nanostructured microstructure exhibiting a strong fiber crystallographic texture and elongated grain shape along the wire axis. This work presents a comprehensive study of the effective elasto-plastic behavior of this composite material. As the material exhibits several characteristic scales, an original strategy is proposed based on iterative scale transition steps from the nanometric grain scale to the millimetric macro-scale. The best modeling strategy is selected to estimate reliably the effective elasto-plastic behavior of Cu-Nb wires with minimum computational time. Finally, for the first time, the models are confronted to tensile tests and in-situ neutron diffraction experimental data with a good agreement.

9:20 AM  
Investigating Active Slip Planes in Tantalum using Single Crystal Experiments and Simulations: Hojun Lim1; Jay Carroll1; Joseph Michael1; Corbett Battaile1; Matthew Lane1; 1Sandia National Laboratories
    Active slip systems in body centered cubic (BCC) metals are still ambiguous and controversial. In this work, active slip planes in tantalum are investigated using single crystal experiments and simulations. Four tantalum single crystals with [100], [110], [111] and [149] orientations along the loading direction are analyzed after dynamic Taylor impact tests and quasi-static compression tests. Mechanical behaviors, deformed shapes, texture evolutions and slip traces of single crystals are analyzed and compared with crystal plasticity finite element simulations to investigate active slip systems in tantalum. Both experimental observations and modeling results support dominant dislocation slip along {112} planes in tantalum.

9:40 AM  
Mechanical Properties of Single Crystal Niobium from Uniaxial Deformation Experiments and Crystal Plasticity Modeling: Eureka Pai Kulyadi1; Jean-Francois Croteau2; Philip Eisenlohr1; Chaitanya Kale3; Kiran Solanki3; Thomas Bieler1; Di Kang1; 1Michigan State University; 2I-Cube Research ; 3Arizona State University
    One suggested method to manufacture superconducting radio frequency (SRF) cavities used in particle accelerators, is based on deep-drawing large-grain niobium (Nb) disks into required shapes. Cavity performance is limited by defects arising from deformation processes involved in the shaping process. A crystal plasticity model for plastic deformation in Nb is formulated by incorporating material specific dislocation strengthening coefficients that depend on dislocation interaction mechanisms in play and the thermally activated character of screw dislocation motion. In this study, tension and compression experiments on several Nb single crystals cut from a large-grained disk were performed at strain rates between 10-4 to 10+3 s-1. The specific selection of grains and the orientation of samples used a toolbox that calculates and visualizes the Schmid factors for each slip system based on the grain lattice orientation and anticipated loading. The results from these deformation experiments are compared to the results of the adopted model.

10:00 AM Break

10:20 AM  Invited
Comparison between Experiments and Modeling for Slip Transfer Across Grain Boundaries: Thomas Bieler1; Harsha Phukan1; Yang Su1; Chelsea Edge1; Sarra Haouala2; Martin Crimp1; Philip Eisenlohr1; Carl Boehlert1; Javier Seguardo2; Jonathan Molina2; Javier LLorca2; Marcos Pea-Ortega3; Reza Alizadeh2; 1Michigan State University; 2IMDEA Materiales; 3Universidad Polytechnica Madrid
    The ability to simulate heterogeneous deformation in crystal plasticity based polycrystal simulations requires practical methods to introduce heterogeneous deformation mechanisms into the constitutive laws used to govern deformation. Although crystal plasticity models are effective for simulation of polycrystal deformation, the ability to simulate heterogeneous deformation near grain boundaries is rarely convincing. One approach to improve crystal plasticity models is to introduce the ability to distinguish between grain boundaries that block slip transfer (Hall-Petch effect) and those that do allow slip transfer. To this end, multicrystal samples of pure aluminum, tin, and titanium have been prepared to characterize slip transfer and grain boundary sliding in a nearly columnar geometry and to build a corresponding computational description of the specimen. Progress in introducing simple methods to restrict slip transfer appropriately and their ability to simulate thoroughly characterized regions of microstructure in research programs at IMDEA and MSU will be summarized.

10:50 AM  Invited
More than Crystal Plasticity: Multiphysics in DAMASK: Philip Eisenlohr1; Aritra Chakraborty1; Pratheek Shanthraj2; Martin Diehl3; Darren Pagan4; Thomas Bieler1; 1Michigan State University; 2University of Manchester; 3Max-Planck-Institut fr Eisenforschung GmbH; 4Cornell University
    Decomposing the total deformation gradient into elastic, eigenstrain, and plastic components opens the door to concurrently couple various mechanisms and associated transport phenomena to the standard crystal plasticity solution of mechanical equilibrium. The talk highlights recent advances in implementing staggered solution schemes for heat and mass transport as well as phase field damage that allows concurrent coupling to the solution of mechanical equilibrium for arbitrary elastic, eigenstrain, and plastic material behavior with DAMASK. Examples to demonstrate these capabilities include the variation of the internal stress field during thermal cycling of polycrystalline hexagonal Ti and the stress-driven mass redistribution in plastically relaxing Sn films under thermal stress.

11:20 AM  
In-situ Mapping of Spatially Resolved Stress Fields Associated with Twinning in Bulk HCP Crystals: M Arul Kumar1; Laurent Capolungo1; Rodney McCabe1; Wenjun Liu2; Jon Tischler2; Carlos Tome1; 1Los Alamos National Laboratory; 2Argonne National Laboratory
    Deformation twinning in a crystal is associated with significant lattice reorientation and localized shear in the narrow twin domain; hence heterogeneity in stresses is developed at and in the vicinity of twins. These stresses strongly influence further twin growth and de-twinning processes but are extremely difficult to characterize experimentally. In this study, an in-situ synchrotron experiment with differential-aperture X-ray microscopy technique is performed to measure the 3D stresses in the vicinity of a tensile-twin in hexagonal close packed magnesium and titanium with a spatial resolution of 0.5micron. The measured local stress aids to characterize the dynamic processes involved with twinning, which are: the selected grain deforms elastically before twinning, and the twin formation splits the grain into two non-interacting fragments. Under further straining twin grows heterogeneously and it well correlates with the measured local stresses. This work significantly advances the understanding of twinning and also guide the modeling tool development.

11:40 AM  
Modeling of Two-phase Polycrystals using a Gradient Crystal Plasticity Theory Including Dissipative Hardening and Energetic Micro-stress: Paul Christodoulou1; Avery Samuel1; Ricardo Lebensohn2; Frank Zok1; Irene Beyerlein1; 1University of California, Santa Barbara; 2Los Alamos National Laboratory
    The goal of this work is to understand the combined dissipative and energetic effects of Geometrically-Necessary Dislocations (GNDs) on the mechanical response of FCC/BCC systems in quasi-static loading. To this end, a dissipative hardening effect, involving the calculation of the GND density fields tied to a material length parameter and strength, is implemented in a previously-developed elasto-viscoplastic (EVP) Fast Fourier Transform (FFT)- based formulation which included energetic GND effects. Separate and combined effects of GNDs on energetic and dissipative hardening are studied. This formulation is applied to simple FCC polycrystal laminates, then FCC polycrystals, and finally FCC/BCC two-phase systems. This final set of simulations is compared to experimental quasi-static compression testing of FCC/BCC two-phase metals to understand the role of grain size and grain shape in the anisotropic mechanical response of these materials.