Void behaviors from low to high triaxialities: Transition from void collapse to void coalescence

Liu, Zhigang; Wong, W.H.; Guo, T.F.

doi:10.1016/j.ijplas.2016.05.008

Cited by 86 publications

(46 citation statements)

References 67 publications

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“…Upon shock at t 0 , the material slice B1 is firstly compressed in uniaxial(1D) manner, and 11 22 33 p p p   , resulting in non-zero shear stress  according to Eq. (9). At this instant, the shear stress sharply builds up to the peak value, similar to the press, as shown in Fig.…”

Section: Thermodynamic Characteristics Under Compression and Releasesupporting

confidence: 54%

Shock responses of nanoporous aluminum by molecular dynamics simulations

Xiang

Cui

Yang

et al. 2017

International Journal of Plasticity

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Abstract:We present systematic investigations on the shock responses of nanoporous aluminum (np-Al) by nonequilibrium molecular dynamics simulations. The dislocation nucleation sites are found to concentrate in low latitude region near the equator of the spherical void surfaces. We propose a continuum wave reflection theory and a resolved shear stress model to explain the distribution of dislocation nucleation sites. The simulations reveals two mechanisms of void collapse: the plasticity mechanism and the internal jetting mechanism. The plasticity mechanism, which leads to transverse collapse of voids, prevails under relatively weaker shocks; while the internal jetting mechanism, which leads to longitudinal filling of the void vacuum, plays more significant role as the shock intensity increases. In addition, an abnormal thermodynamic phenomenon (i.e., arising of temperature with pressure dropping) in shocked np-Al is discovered. This phenomenon is incompatible with the conventional Rankine-Hugoniot theory, and is explained by the nonequilibrium processes involved in void collapse. The influences of void collapse on spall fracture of np-Al is studied. Under the same loading velocity, the spall strength of np-Al is found to be lower than that of single-crystal Al; but the spall resistance is higher in np-Al than in single-crystal Al. This is explained by the combined influences of thermal dissipation and stress attenuation during shock wave propagation in np-Al.

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Section: Thermodynamic Characteristics Under Compression and Releasesupporting

confidence: 54%

Shock responses of nanoporous aluminum by molecular dynamics simulations

Xiang

Cui

Yang

et al. 2017

International Journal of Plasticity

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“…Therefore, even if a proper calibration of the GTN model can crudely reproduce the coalescence stage, a different model is more suitable to describe and to predict this physical process (Brocks et al, 1995;Benzerga and Leblond, 2010;Besson, 2010). In this context, different coalescence modes compete depending on the loading conditions and the micromechanical structure as recently studied by Pineau et al (2016); Cortese et al (2016); Liu et al (2016); Brünig et al (2018); Roth et al (2018). The most investigated mode is by internal necking: the onset of coalescence is reached when plastic flow localises inside the intervoid ligament oriented normal to the main loading direction.…”

Section: Introduction and Motivationsmentioning

confidence: 99%

A micromechanics-based non-local damage to crack transition framework for porous elastoplastic solids

Leclerc

Nguyễn

Pardoen³

et al. 2020

International Journal of Plasticity

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The failure process of ductile porous materials is simulated by representing the damage nucleation, growth and coalescence stages up to crack initiation and propagation using a physically-based constitutive model. In particular, a non-local damage to crack transition framework is developed to predict the fracture under various loading conditions while minimising case-dependent calibration process. The formulation is based on a discontinuous Galerkin method, making it computationally efficient and scalable. The initial stable damage process is simulated using an implicit non-local damage model ensuring solution uniqueness beyond the onset of softening relying on the Gurson-Tvergaard-Needleman (GTN) model. Once the coalescence criterion is satisfied, which can physically arise before or during the softening stage, a cohesive band is introduced. Within the cohesive band, a void coalescencebased governing law is solved, accounting for the stress triaxiality state and material history, in order to capture the near crack tip failure process in a micromechanically sound way. Two coalescence models are then successively considered and compared. First, with a view to model verification towards literature results, a numerical coalescence model detects crack initiation at loss of ellipticity of a local model, and the crack opening is governed by ad-hoc parameters of the GTN model. Alternatively, the Thomason criterion is used to detect crack nucleation during the softening stage while the Thomason coalescence model governs the crack opening process. This latter model is able to reproduce slant and cup-cone failure modes in plane-strain and axisymmetric specimens, respectively.

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“…A multi-point constraint (MPC) user subroutine available in the implicit FE solver Abaqus/Standard was used to control the macroscopic loading of the unit cell. Details regarding this numerical procedure may be found elsewhere [48][49][50][51].…”

Section: Micromechanical Modellingmentioning

confidence: 99%

A Numerical Study on Ductile Failure of Porous Ductile Solids With Rate-Dependent Matrix Behavior

Dæhli

Morin

Benallal

et al. 2019

Journal of Applied Mechanics

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This work examines the effects of loading rate on the plastic flow and ductile failure of porous solids exhibiting rate-dependent behavior relevant to many structural metals. Two different modeling approaches for ductile failure are employed and numerical analyses are performed over a wide range of strain rates. Finite element unit cell simulations are carried out to evaluate the macroscopic mechanical response and ductile failure by void coalescence for various macroscopic strain rates. The unit cell results are then used to assess the accuracy of a rate-dependent porous plasticity model, which is subsequently used in strain localization analyses based on the imperfection band approach. Strain localization analyses are conducted for (i) proportional loading paths and (ii) non-proportional loading paths obtained from finite element simulations of axisymmetric and flat tensile specimens. The effects of strain rate are most apparent on the stress–strain response, whereas the effects of strain rate on ductile failure is found to be small for the adopted rate-dependent constitutive model. However, the rate-dependent constitutive formulation tends to regularize the plastic strain field when the strain rate increases. In the unit cell simulations, this slightly increases the strain at coalescence with increasing strain rate compared to a rate-independent constitutive formulation. When the strain rate is sufficiently high, the strain at coalescence becomes constant. The strain localization analyses show a negligible effect of strain rate under proportional loading, while the effect of strain rate is more pronounced when non-proportional loading paths are assigned.

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Void behaviors from low to high triaxialities: Transition from void collapse to void coalescence

Cited by 86 publications

References 67 publications

Shock responses of nanoporous aluminum by molecular dynamics simulations

Shock responses of nanoporous aluminum by molecular dynamics simulations

A micromechanics-based non-local damage to crack transition framework for porous elastoplastic solids

A Numerical Study on Ductile Failure of Porous Ductile Solids With Rate-Dependent Matrix Behavior

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