The influence of particle shape, volume fraction and distribution on post-necking deformation and fracture in uniaxial tension of AA5754 sheet materials

Abstract

a b s t r a c tFinite element analysis was performed over a small particle field, edge constraint plane strain post-necking model. The aim is to understand the roles of particle shape, volume fraction and distribution over the post-necking deformation and fracture of AA5754-O sheet materials. For models containing one single particle, the post-necking deformation decreases when the particle varies from circular to elliptical. The inter-particle spacing, the major parameter of distribution to determine whether a pair of particles belongs to a stringer or not, was varied for models with two particles of circular or elliptical shape. The general trend is that the post-necking deformation and fracture strains decrease with decreasing spacing between particles. There is considerable difference in terms of both fracture topographies and strains for models containing 16 particles when distributions varied from random/uniform to stringer distributions. The post-necking deformation and fracture strains monotonically decrease with particle volume fractions for models with 4-64 particles of random or stringer distribution. This indicates that the post-necking behavior for AA5754-O alloys where the matrix material is rather ductile is not solely controlled by a single or pair of particles although they may become initiation places of damage. Multiple damaging sources such as stringers or large particles can act cooperatively and speed up the damaging propagation of the material, and therefore produce small post-necking deformation and early fracture. The center clustering of particles can be beneficial for post-necking behavior and bendability of sheet materials.

A parametric finite element study and an analytical model of particle distributions on post-necking deformation and failure mode in AA5754 aluminum alloy sheets

“…1) where the emphasis will be put on the edge constrained plane strain post-necking model (thesubject of the current paper) and its later modification (Hu et al 2009). …”

“…The post-necking model domain (RD × ND) proposed in Hu et al (2008a) was later modified to the RD × ND cross section (Hu et al 2009) due to the following reasons. Firstly, the RD ×ND post-necking model was developed under the assumption of relatively large width (w)/thickness (t) ratio (r ) of typically greater than 12 where the failure normally follow one of the two conjugated localized necking band initiated at the onset of localized necking which is actually observed in tensile tests of AA5754 sample with w × t = 12 × 1 mm 2 .…”

“…The properties of the particles are chosen to be the same as that of previous works (Hu et al 2008a;Hu et al 2009). Linear elasticity is assumed for equivalent stress values less than σ 0 p = 0.8 GPa, with Young's modulus (E) as 210 GPa and Poisson's ratio (ν) as 0.28.…”

“…models, since a real random distribution of isolated particles and stringers is not possible for a very small number of particles. More importantly, an analytical model has been put forward in the end of this paper which shed lights on deeper insights and more understandings of the previous (Hu et al 2009) and current results.…”

“…The number of particles considered is in the order of several thousands or more, and therefore one can generate statistically sound, real random distribution of stringers or isolated particles. Recently, a parametric study of small virtual particle field containing 1-64 particles had been performed (Hu et al 2009), but from another perspective. Instead of having sound statistics and near sample scale thickness dimension, that study focused on more realistic representation of particle shapes with smooth particle/matrix boundaries by fine triangular quadratic finite element meshes which limit studies of models containing large number of particles.…”