Title: Validation of micro-mechanical FFT-based simulations using High Energy Diffraction Microscopy on Ti-7Al

Abstract

Here, a validation is reported for micromechanical simulation using a reimplementation of an elasto-viscoplastic FFT-based (EVPFFT) formulation, i.e., the Micromechanical Analysis of Stress-strain Inhomogeneities with fast Fourier transform (MASSIF) code, against experimental data obtained from synchrotron x-ray diffraction. The experimental data was collected during in-situ deformation of a titanium alloy specimen by High Energy Diffraction Microscopy (HEDM), which provided the average elastic strain tensor and orientation of each grain in a polycrystalline sample. MASSIF was used to calculate the local micromechanical fields in a Ti-7Al polycrystalline sample at different load levels. The initially attempted simulation showed that, although the effective response was calibrated to reproduce the experiment, MASSIF was not able to reproduce the micromechanical fields at the scale of individual grains. The differences between calculated and measured averages at the grain scale were related to initial residual strains resulting from the prior processing of the material, which had not been incorporated in the original calculation. Accordingly, a new simulation was instantiated using information on the measured residual strains to define a set of eigenstrains, calculated via an Eshelby approximation. This initialization significantly improved the correlation between calculated and simulated fields for all strain and stress components, for measurements performedmore » within the elastic regime. For the measurements at the highest load, which was past plastic yield, the correlations deteriorated because of plastic deformation at the grain level and the lack of an accurate enough constitutive description in this deformation regime.« less

Authors:

Tari, Vahid ^[1]; Lebensohn, Ricardo A.  ^[2];

• Search DOE PAGES for author "Lebensohn, Ricardo A."
• Search DOE PAGES for ORCID "0000-0002-3152-9105"

Pokharel, Reeju  ^[2];

• Search DOE PAGES for author "Pokharel, Reeju"
• Search DOE PAGES for ORCID "0000-0002-0563-6142"

Turner, Todd J. ^[3]; Shade, Paul A. ^[3]; Bernier, Joel V. ^[4]; Rollett, Anthony D. ^[1]

---

+ Show Author Affiliations

1. Carnegie Mellon Univ., Pittsburgh, PA (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Air Force Research Lab. (AFRL), Wright-Patterson AFB, OH (United States)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Thu May 31 00:00:00 EDT 2018

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOD High Performance Computing Modernization Program (HPCMP); USDOE-USDOD Joint Munitions Program (JMP); Air Force Research Laboratory (AFRL); National Science Foundation (NSF)

OSTI Identifier:

1440443

Alternate Identifier(s):

OSTI ID: 1694056; OSTI ID: 1838254

Report Number(s):

LA-UR-17-31124; LLNL-JRNL-824240
Journal ID: ISSN 1359-6454

Grant/Contract Number:  

AC52-06NA25396; ACI-1548562; AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 154; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Validation; Synchrotron radiation; Micromechanical modelling; Residual stresses; Polycrystal plasticity