Void shape effects and voids starting from cracked inclusion

Abstract

a b s t r a c tNumerical, axisymmetric cell model analyses are used to study the growth of voids in ductile metals, until the mechanism of coalescence with neighbouring voids sets in. A special feature of the present analyses is that extremely small values of the initial void volume fraction are considered, down to 10 À10 , which means that the metal undergoes huge strains before coalescence. This is accounted for in the present analyses by using remeshing techniques. The evolution of the void shape during the large deformations is a natural outcome of the numerical analysis. Also the effect of different initial void shapes is considered, as well as the effect of different spacings between the voids in the axial and transverse directions. While these first analyses are carried out for voids in a homogeneous metal, a second set of cell model studies are carried out for voids that initiate from a crack in a hard second phase particle. As the particle deforms relatively little the void growth is here dominated by strong blunting of the metal at the tip of the initial penny-shaped crack. These analyses are used to estimate how well the void shape evolution would be approximated by assuming that the presence of the particle in the material adjacent to the void can be neglected.

Characterization and micromechanical modelling of microstructural heterogeneity effects on ductile fracture of 6xxx aluminium alloys

“…Since voids nucleate by particle cracking rather than by decohesion, a freshly nucleated void is initially penny-shaped and the mode of deformation is dominated by opening and blunting of the void/crack tip [59].…”

A model for ductile damage prediction at low stress triaxialities incorporating void shape change and void rotation

“…Cell computations have been extensively used to study ductile fracture mechanisms (void growth, nucleation and coalescence -e.g. Kuna and Sun, 1996;Faleskog, 2007b, 2011;Tvergaard, 2011;Zybell et al, 2014); to reveal the influence of stress states on material ductility (e.g. Gao et al, 2010;Dunand and Mohr, 2014); and also to calibrate and validate micro-mechanically based damage models (see e.g.…”

On the role of initial void geometry in plastic deformation of metallic thin films: A molecular dynamics study

“…In the last decade, the finite element method (FEM) has been employed to study void growth and coalescence as a function of many variables, including the temperature, void configuration [9], stress triaxiality [10], crystallographic orientations [11], initial void volume fraction [12], initial void size [13], and initial void shape [14]. However, as the size of void approaches nanoscale, the continuum approximation based on which FEM is established is not valid anymore.…”