Publications

Littlewood, David J.; Foster, John E.; Seleson, Pablo D.

Abstract not provided.

Merewether, Mark T.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Gampert, Scott G.; Xavier, Patrick G.; Plews, Julia A.

Sierra/SolidMechanics (Sierra/SM) is a Lagrangian, three-dimensional code for finite element analysis of solids and structures. It provides capabilities for explicit dynamic, implicit quasistatic and dynamic analyses. The explicit dynamics capabilities allow for the efficient and robust solution of models with extensive contact subjected to large, suddenly applied loads. For implicit problems, Sierra/SM uses a multi-level iterative solver, which enables it to effectively solve problems with large deformations, nonlinear material behavior, and contact. Sierra/SM has a versatile library of continuum and structural elements, and a large library of material models. The code is written for parallel computing environments enabling scalable solutions of extremely large problems for both implicit and explicit analyses. It is built on the SIERRA Framework, which facilitates coupling with other SIERRA mechanics codes. This document describes the functionality and input syntax for Sierra/SM.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

Presented in this document is a small portion of the tests that exist in the Sierra / SolidMechanics (Sierra / SM) verification test suite. Most of these tests are run nightly with the Sierra / SM code suite, and the results of the test are checked versus the correct analytical result. For each of the tests presented in this document, the test setup, a description of the analytic solution, and comparison of the Sierra / SM code results to the analytic solution is provided. Mesh convergence is also checked on a nightly basis for several of these tests. This document can be used to confirm that a given code capability is verified or referenced as a compilation of example problems. Additional example problems are provided in the Sierra / SM Example Problems Manual. Note, many other verification tests exist in the Sierra / SM test suite, but have not yet been included in this manual.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.

Presented in this document are tests that exist in the Sierra/SolidMechanics example problem suite, which is a subset of the Sierra/SM regression and performance test suite. These examples showcase common and advanced code capabilities. A wide variety of other regression and verification tests exist in the Sierra/SM test suite that are not included in this manual.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

This document is a user's guide for capabilities that are not considered mature but are available in Sierra/SolidMechanics (Sierra/SM) for early adopters. The determination of maturity of a capability is determined by many aspects: having regression and verification level testing, documentation of functionality and syntax, and usability are such considerations. Capabilities in this document are lacking in one or many of these aspects.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

Accurate and efficient constitutive modeling remains a cornerstone issues for solid mechanics analysis. Over the years, the LAME advanced material model library has grown to address this challenge by implement- ing models capable of describing material systems spanning soft polymers to stiff ceramics including both isotropic and anisotropic responses. Inelastic behaviors including (visco)plasticity, damage, and fracture have all incorporated for use in various analyses. This multitude of options and flexibility, however, comes at the cost of many capabilities, features, and responses and the ensuing complexity in the resulting imple- mentation. Therefore, to enhance confidence and enable the utilization of the LAME library in application, this effort seeks to document and verify the various models in the LAME library. Specifically, the broader strategy, organization, and interface of the library itself is first presented. The physical theory, numerical implementation, and user guide for a large set of models is then discussed. Importantly, a number of verifi- cation tests are performed with each model to not only have confidence in the model itself but also highlight some important response characteristics and features that may be of interest to end-users. Finally, in looking ahead to the future, approaches to add material models to this library and further expand the capabilities are presented.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

This document covers Sierra/SolidMechanics capabilities specific to Goodyear use cases. Some information may be duplicated directly from the Sierra/SolidMechanics User's Guide but is reproduced here to provide context for Goodyear-specific options.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

This is an addendum to the Sierra/SolidMechanics 4.48 User's Guide that documents additional capabilities available only in alternate versions of the Sierra/SolidMechanics (Sierra/SM) code. These alternate versions are enhanced to provide capabilities that are regulated under the U.S. Department of State's International Traffic in Arms Regulations (ITAR) export-control rules. The ITAR regulated codes are only distributed to entities that comply with the ITAR export-control requirements. The ITAR enhancements to Sierra/SM in- clude material models with an energy-dependent pressure response (appropriate for very large deformations and strain rates) and capabilities for blast modeling. Since this is an addendum to the standard Sierra/SM user's guide, please refer to that document first for general descriptions of code capability and use.

Computational Mechanics

Alleman, Coleman A.; Foulk, James W.; Mota, Alejandro M.; Lim, Hojun L.; Littlewood, David J.

The heterogeneity in mechanical fields introduced by microstructure plays a critical role in the localization of deformation. To resolve this incipient stage of failure, it is therefore necessary to incorporate microstructure with sufficient resolution. On the other hand, computational limitations make it infeasible to represent the microstructure in the entire domain at the component scale. In this study, the authors demonstrate the use of concurrent multiscale modeling to incorporate explicit, finely resolved microstructure in a critical region while resolving the smoother mechanical fields outside this region with a coarser discretization to limit computational cost. The microstructural physics is modeled with a high-fidelity model that incorporates anisotropic crystal elasticity and rate-dependent crystal plasticity to simulate the behavior of a stainless steel alloy. The component-scale material behavior is treated with a lower fidelity model incorporating isotropic linear elasticity and rate-independent J2 plasticity. The microstructural and component scale subdomains are modeled concurrently, with coupling via the Schwarz alternating method, which solves boundary-value problems in each subdomain separately and transfers solution information between subdomains via Dirichlet boundary conditions. In this study, the framework is applied to model incipient localization in tensile specimens during necking.

Multiscale Modeling and Simulation

Costa, Timothy B.; Bond, Stephen D.; Littlewood, David J.

In many applications the resolution of small-scale heterogeneities remains a significant hurdle to robust and reliable predictive simulations. In particular, while material variability at the mesoscale plays a fundamental role in processes such as material failure, the resolution required to capture mechanisms at this scale is often computationally intractable. Multiscale methods aim to overcome this difficulty through judicious choice of a subscale problem and a robust manner of passing information between scales. One promising approach is the multiscale finite element method, which increases the fidelity of macroscale simulations by solving lower-scale problems that produce enriched multiscale basis functions. In this study, we present the first work toward application of the multiscale finite element method to the nonlocal peridynamic theory of solid mechanics. This is achieved within the context of a discontinuous Galerkin framework that facilitates the description of material discontinuities and does not assume the existence of spatial derivatives. Analysis of the resulting nonlocal multiscale finite element method is achieved using the ambulant Galerkin method, developed here with sufficient generality to allow for application to multiscale finite element methods for both local and nonlocal models that satisfy minimal assumptions. We conclude with preliminary results on a mixed-locality multiscale finite element method in which a nonlocal model is applied at the fine scale and a local model at the coarse scale.

Littlewood, David J.

Abstract not provided.

Foulk, James W.; Alleman, Coleman A.; Mota, Alejandro M.; Lim, Hojun L.; Littlewood, David J.; Bergel, Guy L.; Popova, Evdokia P.; Montes de Oca Zapiain, David M.

The heterogeneity in mechanical fields introduced by microstructure plays a critical role in the localization of deformation. To resolve this incipient stage of failure, it is therefore necessary to incorporate microstructure with sufficient resolution. On the other hand, computational limitations make it infeasible to represent the microstructure in the entire domain at the component scale. In this study, the authors demonstrate the use of concurrent multi- scale modeling to incorporate explicit, finely resolved microstructure in a critical region while resolving the smoother mechanical fields outside this region with a coarser discretization to limit computational cost. The microstructural physics is modeled with a high-fidelity model that incorporates anisotropic crystal elasticity and rate-dependent crystal plasticity to simulate the behavior of a stainless steel alloy. The component-scale material behavior is treated with a lower fidelity model incorporating isotropic linear elasticity and rate-independent J 2 plas- ticity. The microstructural and component scale subdomains are modeled concurrently, with coupling via the Schwarz alternating method, which solves boundary-value problems in each subdomain separately and transfers solution information between subdomains via Dirichlet boundary conditions. Beyond cases studies in concurrent multiscale, we explore progress in crystal plastic- ity through modular designs, solution methodologies, model verification, and extensions to Sierra/SM and manycore applications. Advances in conformal microstructures having both hexahedral and tetrahedral workflows in Sculpt and Cubit are highlighted. A structure-property case study in two-phase metallic composites applies the Materials Knowledge System to local metrics for void evolution. Discussion includes lessons learned, future work, and a summary of funded efforts and proposed work. Finally, an appendix illustrates the need for two-way coupling through a single degree of freedom.

Vasenkov, Alex V.; Littlewood, David J.

Abstract not provided.

Littlewood, David J.; Alleman, Coleman A.; Bergel, Guy L.; Foulk, James W.; Mota, Alejandro M.; Lim, Hojun L.

Abstract not provided.

Alleman, Coleman A.; Foulk, James W.; Lim, Hojun L.; Mota, Alejandro M.; Littlewood, David J.

Abstract not provided.

Littlewood, David J.; Foster, John E.; Seleson, Pablo D.

Abstract not provided.

Littlewood, David J.; Foster, John E.; Seleson, Pablo D.

Abstract not provided.

Plews, Julia A.; Crane, Nathan K.; de Frias, Gabriel J.; Le, San L.; Littlewood, David J.; Merewether, Mark T.; Mosby, Matthew D.; Pierson, Kendall H.; Porter, V.L.; Shelton, Timothy S.; Thomas, Jesse D.; Tupek, Michael R.; Veilleux, Michael V.; Xavier, Patrick G.

Accurate and efficient constitutive modeling remains a cornerstone issues for solid mechanics analysis. Over the years, the LAME advanced material model library has grown to address this challenge by implementing models capable of describing material systems spanning soft polymers to s ti ff ceramics including both isotropic and anisotropic responses. Inelastic behaviors including (visco) plasticity, damage, and fracture have all incorporated for use in various analyses. This multitude of options and flexibility, however, comes at the cost of many capabilities, features, and responses and the ensuing complexity in the resulting implementation. Therefore, to enhance confidence and enable the utilization of the LAME library in application, this effort seeks to document and verify the various models in the LAME library. Specifically, the broader strategy, organization, and interface of the library itself is first presented. The physical theory, numerical implementation, and user guide for a large set of models is then discussed. Importantly, a number of verification tests are performed with each model to not only have confidence in the model itself but also highlight some important response characteristics and features that may be of interest to end-users. Finally, in looking ahead to the future, approaches to add material models to this library and further expand the capabilities are presented.

Alleman, Coleman A.; Foulk, James W.; Lim, Hojun L.; Littlewood, David J.; Mota, Alejandro M.

Abstract not provided.

Littlewood, David J.

Abstract not provided.

D'Elia, Marta D.; Bochev, Pavel B.; Perego, Mauro P.; Littlewood, David J.

Abstract not provided.

Littlewood, David J.; D'Elia, Marta D.; Perego, Mauro P.; Bochev, Pavel B.

Abstract not provided.

Lifflander, Jonathan; Hollman, David S.; Wilke, Jeremiah J.; Markosyan, Aram H.; Littlewood, David J.; Rizzi, Francesco N.; Bennett, Janine C.

Abstract not provided.

Foulk, James W.; Alleman, Coleman A.; Battaile, Corbett C.; Lim, Hojun L.; Littlewood, David J.; Mota, Alejandro M.

Abstract not provided.

Littlewood, David J.; D'Elia, Marta D.; Perego, Mauro P.; Bochev, Pavel B.

Abstract not provided.