Cross-Scale Modeling for Component Scale Simulations

Matthew Nelms | 21-ERD-022

Project Overview

The objective of this exploratory research was to probe the single crystal behavior of tantalum at high strain rate conditions. The project consists of three main components, the first being crystal plasticity (CP) model development, the second being the experimental campaign to obtain hole closure measurements, and the third being molecular dynamics (MD) calculations to inform the model development. The goal was to perform a component scale calculation with explicitly resolved grain structures that mimic previously fielded polycrystal tantalum experiments. By doing this we will be able to better understand the sub-grain scale effects on metal deformation under high strain rate, weak shock, and large strain conditions.

The scientific approach was to perform cross-scale methodologies for model development and connect the newly developed models to focused experiments. The first cross-scale effort was to combine existing model forms into a new crystal plasticity formulation and assess how well it performed across a wide range of experimental platforms that traverse broad ranges of strain rate, strain, and pressure space. This included previously published efforts as well as new experiments using our recently developed hole-closure platform. The goal was to challenge the current state-of-the-art in crystal plasticity to assess both capabilities and deficiencies. Using this knowledge, an MD campaign made direct connections to crystal plasticity and developed novel framework based on what can be directly extracted from the lower length scale calculations while skipping over the usual step to go through Dislocation Dynamics. This model was directly parameterized to MD results and validated against experimental data. 

Mission Impact

The results of this project provide a robust modeling capability developed to run on next generation high performance computing platforms. The CP model is implemented with graphics processing unit (GPU) and host code portability in mind. The mechanistically driven approach will provide information at fidelities not yet achieved in the existing models to date and at scales only achievable at DOE National Laboratories. By providing an improved understanding of grain scale behavior of metals, the results can elucidate the necessary physics to include in macroscale models. The cross-component methodologies developed will provide direct support of LLNL's stewardship and modernization efforts with physically accurate models of metal strength.

Publications, Presentations, and Patents

Bertin, N., Carson, R., Bulatov, V. V., Lind, J., & Nelms, M. (2023). Crystal plasticity model of BCC metals from large-scale MD simulations. Acta Materialia, 119336.

R. Carson, N. Bertin, J. Lind, and M. Nelms,"Modelling single crystal tantalum across a dynamic range of strain rates with a new crystal plasticity model" (Presentation, SES 2022, College Station, TX, Oct 17, 2022). LLNL-PRES-841193

M. Nelms, R. Carson, N. Bertin, J. and Lind, "Modelling single crystal tantalum across a dynamic range of strain rates with a new crystal plasticity model" (Presentation, APS SCCM 2023, Chicago, IL, June 19, 2023). LLNL-PRES-850054

N. Bertin, W. Cai, S. Aubry, M. Nelms, R. Carson, A. Arsenlis, V.V. Bulatov, "Cross-scale modeling of metal plasticity: Dislocation dynamics insights from large-scale MD simulations" (Invited Presentation, Cairo Symposium on the Physics of Metal Plasticity, March 5, 2023, Cairo, Egypt, 2023).  LLNL-PRES-845545