Void growth and coalescence in anisotropic plastic solids

• Published in: International journal of solids and structures Vol. 48; no. 11; pp. 1696 - 1710
• Main Authors: Keralavarma, S.M., Hoelscher, S., Benzerga, A.A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-06-2011; Elsevier
• Subjects: A. Ductile fracture; A. Voids and inclusions; Anisotropy; Applied sciences; Axisymmetric; B. Finite element analysis; B. Porous metal plasticity; C. Anisotropy; C. Constitutive behavior; Cracks; Elasticity. Plasticity; Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Physics; Plastic flow; Solid mechanics; Stress-strain relationships; Structural and continuum mechanics; Triaxiality; Voids; A. Ductile fracture; C. Anisotropy; B. Finite element analysis; C. Constitutive behavior; B. Porous metal plasticity; A. Voids and inclusions; Plastic anisotropy; Constitutive equation; High strain; Localized mode; Modeling; Periodic structure; Finite element method; Cavity; Dimensional analysis; Penny-shaped cracks; Damaging; Representative volume element; Plastic flow; Anisotropic material; Spheroid; Calibration; Cavitation; Axial symmetry; Triaxial stress; Orthotropic material; Spatial distribution; Periodic medium; Transverse isotropy; Porosity; Effective medium model
• ISSN: 0020-7683; 1879-2146
• DOI: 10.1016/j.ijsolstr.2011.02.020

Large strain finite element calculations of unit cells subjected to triaxial axisymmetric loadings are presented for plastically orthotropic materials containing a periodic distribution of aligned spheroidal voids. The spatial distribution of voids and the plastic flow properties of the matrix are assumed to respect transverse isotropy about the axis of symmetry of the imposed loading so that a two-dimensional axisymmetric analysis is adequate. The parameters varied pertain to load triaxiality, matrix anisotropy, initial porosity and initial void shape so as to include the limiting case of penny-shaped cracks. Attention is focussed on comparing the individual and coupled effects of void shape and material anisotropy on the effective stress–strain response and on the evolution of microstructural variables. In addition, the effect of matrix anisotropy on the mode of plastic flow localization is discussed. From the results, two distinct regimes of behavior are identified: (i) at high triaxialities, the effect of material anisotropy is found to be persistent, unlike that of initial void shape and (ii) at moderate triaxialities the influence of void shape is found to depend strongly on matrix anisotropy. The findings are interpreted in light of recent, microscopically informed models of porous metal plasticity. Conversely, observations are made in relation to the relevance of these results in the development and calibration of a broader set of continuum damage mechanics models.