Anisotropic ductile fracture: experiments, modeling, and numerical simulations

The continuous hot rolling process induces anisotropy in the plastic yield and flow and results in an anisotropic ductile fracture. In this study, experiments, including uniaxial in -plane tension tests and shear tests of butterfly specimens along different material orien-tations, were performed, and microscopic observations were used to determine the dif-ferences in damage mechanisms. The Yld91 anisotropic yield stress was introduced into the extended isotropic Gurson-Tvergaard-Needleman (GTN) model, and the associated flow rule (AFR) and non-associated flow rule (NAFR) were adopted to formulate two anisotropic GTN models. Anisotropic GTN models were implemented in finite element software via user subroutines, and were used to predict the fracture initiation of Al2024-T351. For different plastic flow rules, the anisotropic parameters were calibrated using the anisotropic stress and Lankford coefficients. An inverse analysis with a two-stage optimization algorithm was adopted to calibrate the damage-related parameters. More-over, an extended isotropic GTN model was adopted for comparison. The prediction ac-curacy of the proposed anisotropic GTN models was evaluated by analyzing the load responses and displacements at fracture for various specimens and material orientations. The good conformation between the experimental results and numerical predictions ver-ifies the predictive ability of the proposed models to a certain degree. In addition, some suggestions and conclusions are provided for the formulation of an advanced anisotropic GTN model with enhanced accuracy.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study investigates the anisotropy in plastic yield and flow and anisotropic ductile fracture induced by the continuous hot rolling process. Anisotropic GTN models are proposed based on the Yld91 anisotropic yield stress, and different flow rules are employed. The models are implemented in finite element software and used to predict fracture initiation in Al2024-T351. The accuracy of the proposed anisotropic GTN models is evaluated through load responses and displacements, showing good agreement with experimental results and verifying their predictive ability. Suggestions for an advanced anisotropic GTN model are also provided.