Title: Anisotropic plasticity model forms for extruded Al 7079: Part II, validation

Abstract

This is the second part of a two-part contribution on modeling of the anisotropic elastic-plastic response of aluminum 7079 from an extruded tube. Part I focused on calibrating a suite of yield and hardening functions from tension test data; Part II concentrates on evaluating those calibrations. Here, a rectangular validation specimen with a blind hole was designed to provide heterogeneous strain fields that exercise the material anisotropy, while at the same time avoiding strain concentrations near sample edges where Digital Image Correlation (DIC) measurements are difficult to make. Specimens were extracted from the tube in four different orientations and tested in tension with stereo-DIC measurements on both sides of the specimen. Corresponding Finite Element Analysis (FEA) with calibrated isotropic (von Mises) and anisotropic (Yld2004-18p) yield functions were also conducted, and both global force-extension curves as well as full-field strains were compared between the experiments and simulations. Specifically, quantitative full-field strain error maps were computed using the DIC-leveling approach proposed by Lava et al. The specimens experienced small deviations from ideal boundary conditions in the experiments, which had a first-order effect on the results. Therefore, the actual experimental boundary conditions had to be applied to the FEA in order to makemore » valid comparisons. The predicted global force-extension curves agreed well with the measurements overall, but were sensitive to the boundary conditions in the nonlinear regime and could not differentiate between the two yield functions. Interrogation of the strain fields both qualitatively and quantitatively showed that the Yld2004-18p model was clearly able to better describe the strain fields on the surface of the specimen compared to the von Mises model. These results justify the increased complexity of the calibration process required for the Yld2004-18p model in applications where capturing the strain field evolution accurately is important, but not if only the global force-extension response of the elastic–plastic region is of interest.« less

Authors:

Jones, E. M. C.; Corona, E.; Jones, A. R.; Scherzinger, W. M.; Kramer, S. L. B.

Publication Date:

Mon Mar 01 00:00:00 EST 2021

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1961700

Alternate Identifier(s):

OSTI ID: 1738930; OSTI ID: 1809270

Report Number(s):

SAND-2020-13626J
Journal ID: ISSN 0020-7683; S0020768320304601; PII: S0020768320304601

Grant/Contract Number:  

NA0003525; AC04-94AL85000

Resource Type:

Published Article

Journal Name:

International Journal of Solids and Structures

Additional Journal Information:

Journal Name: International Journal of Solids and Structures Journal Volume: 213 Journal Issue: C; Journal ID: ISSN 0020-7683

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; anisotropic plasticity; verifi cation and validation; Yld2004-18p; von Mises; Al 7079; digital image correlation; finite element analysis; DIC-leveling approach