Finite element analysis to determine the role of porosity in dynamic localization and fragmentation: Application to porous microstructures obtained from additively manufactured materials Articles uri icon

publication date

  • August 2021

start page

  • 102999

end page

  • 103030

volume

  • 143

International Standard Serial Number (ISSN)

  • 0749-6419

Electronic International Standard Serial Number (EISSN)

  • 1879-2154

abstract

  • In this paper, we have performed a microstructurally-informed finite element analysis on the
    effect of porosity on the formation of multiple necks and fragments in ductile thin rings subjected
    to dynamic expansion. For that purpose, we have characterized by X-ray tomography the porous
    microstructure of 4 different additively manufactured materials (aluminium alloy AlSi10Mg,
    stainless steel 316L, titanium alloy Ti6Al4V and Inconel 718L) with initial void volume fractions
    ranging from ≈0.0007% to ≈ 2%, and pore sizes varying between ≈ 6 μm and ≈110 μm. Threedimensional
    analysis of the tomograms has revealed that the voids generally have nearly
    spherical shape and quite homogeneous spatial distribution in the bulk of the four materials
    tested. The pore size distributions quantified from the tomograms have been characterized using a
    Log-normal statistical function, which has been used in conjunction with a Force Biased Algorithm
    that replicates the experimentally observed random spatial distribution of the voids, to
    generate ring expansion finite element models in ABAQUS/Explicit (2016) which include actual
    porous microstructures representative of the materials tested. We have modeled the materials
    behavior using von Mises plasticity, and we have carried out finite element calculations for both
    elastic perfectly-plastic materials, and materials which show strain hardening, strain rate hardening
    and temperature softening effects. Moreover, we have assumed that fracture occurs when a
    critical value of effective plastic strain is reached. The finite element calculations have been
    performed for expansion velocities ranging from 50 m/s to 500 m/s. A key point of this investigation
    is that we have established individualized correlations between the main features of the
    porous microstructure (i.e. initial void volume fraction, average void size and maximum void
    size) and the number of necks and fragments formed in the calculations. In addition, we have
    brought out the effect of the porous microstrucure and inertia on the distributions of neck and
    fragment sizes. To the authors" knowledge, this is the first paper ever considering actual porous
    microstructures to investigate the role of material defects in multiple localization and dynamic
    fragmentation of ductile metallic materials.

keywords

  • additive manufacturing; finite elements; fragmentation; multiple necking; porosity; printed metals