The effect of material orientation on void growth Articles uri icon

publication date

  • January 2022

start page

  • 1

end page

  • 33


  • 148

International Standard Serial Number (ISSN)

  • 0749-6419

Electronic International Standard Serial Number (EISSN)

  • 1879-2154


  • In this work, we have brought to light the effect of material orientation on void growth. For that
    purpose, we have performed finite element calculations using a cubic unit-cell model with a
    spherical void at its center and subjected to periodic boundary conditions. The behavior of the
    material is described with an elastic isotropic, plastic orthotropic constitutive model with yielding
    defined by Yld2004-18p criterion (Barlat et al., 2005). We have used the multi-point constraint
    subroutine developed by Dakshinamurthy et al. (2021) to enforce constant values of macroscopic
    stress triaxiality T and Lode parameter L in calculations that have been carried out for different
    stress states resulting from the combination of T = 0.33, 1 and 2, with L = − 1, 0 and 1 (axisymmetric tension, generalized shear and axisymmetric compression, respectively). Firstly, we have performed numerical simulations in which the loading directions are collinear with the orthotropy axes of the material, so that the principal directions of macroscopic stress and strain are parallel. Investigation of the cases for which the minor loading axis coincides either with the rolling, the transverse or the normal direction, has shown that the initially spherical void turns
    into an ellipsoid whose rate of growth and eccentricity depend on both stress state and material
    orientation. A key result is that for specific material orientations the anisotropy switches the effect of Lode parameter on void growth, reversing the trends obtained for isotropic von Mises mate rials. Secondly, we have carried out calculations using a novel strategy which consists of
    including angular misalignments within the range 0∘ ≤ θ ≤ 90∘ , so that one loading direction is parallel to one of the symmetry axes of the material, and θ is the angle formed between the other two loading directions and the second and third orthotropy axes. In fact, to the authors" knowledge, these are the first unit-cell calculations ever reported in which the material is modeled using a macroscopic anisotropic yield function with prescribed misalignment between loading and material axes and, at the same time, the macroscopic stress triaxiality and the Lode parameter are controlled to be constant during loading. The finite element calculations have shown that the misalignment between loading and material axes makes the void and the faces of the unit-cell to rotate and twist during loading. Moreover, the main contribution of this work is the identification of an intermediate value of the angle θ for which the growth rate of the void reaches an extreme value (minimum or maximum), so that the numerical results indicate that material orientation and angular misalignment can be strategically exploited to control void growth, and thus promote or delay localization and fracture of anisotropic metal products. The conclusions of this research have been shown to be valid for three different materials (aluminum alloys 2090-T3, 6111-T4 and 6013) and selected comparisons have also been performed using two additional yield criteria (CPB06ex2 and Yld2011-27p).


  • Materials science and engineering


  • anisotropy; material orientation; void growth; stress triaxiality; lode parameter; unit-cell calculations