Simulation of ductile crack growth using computational cells: numerical aspects

Two modes of plastic flow localization commonly occur in the ductile fracture of structural metals undergoing damage and failure by the mechanism involving void nucleation, growth and coalescence. The first mode consists of a macroscopic localization, usually linked to the softening effect of void nucleation and growth, in either a normal band or a shear band where the thickness of the band is comparable to void spacing. The second mode is coalescence with plastic strain localizing to the ligaments between voids by an internal necking process. The ductility of a material is tied to the strain at macroscopic localization, as this marks the limit of uniform straining at the macroscopic scale. The question addressed is whether macroscopic localization occurs prior to void coalescence or whether the two occur simultaneously. The relation between these two modes of localization is studied quantitatively in this paper using a three-dimensional elastic-plastic computational model representing a doubly periodic array of voids within a band confined between two semi-infinite outer blocks of the same material but without voids. At sufficiently high stress triaxiality, a clear separation exists between the two modes of localization. At lower stress triaxialities, the model predicts that the onset of macroscopic localization and coalescence occur simultaneously.

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“…where E 11 , E 22 and E 33 are the logarithmic strains in the outer blocks defined in terms of the stretches as…”

Section: Methodsmentioning

confidence: 99%

On localization and void coalescence as a precursor to ductile fracture

Tekoğlu

Hutchinson

Pardoen

2015

Phil. Trans. R. Soc. A.

129

110

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“…The elastic-plastic inputs into the extended Gurson Model are the Young's modulus, E , the Poisson's ratio, ν , and the intrinsic stress-strain response of the Gurson model (e.g., [4,7]), the present study employs data from a mode I fracture test and a round bar tensile test to identify intrinsic uniaxial stress-strain behavior, 0 f and D .…”

Section: Outline Of the Calibration Protocolmentioning

confidence: 99%

“…When properly calibrated for a specific structural alloy, the Gurson model [1] and some of its close relatives, such as the Rousselier model [2], have shown considerable promise for characterizing mode I crack growth [3][4][5][6][7][8]. In addition, the models have been used to simulate transitions from mode I crack growth to mixed mode shear cracking in the cup-cone fracture process of round tensile bars [9,10] and in threedimensional through-cracks in thin plates [11].…”

Section: Introductionmentioning

confidence: 99%

Calibration procedures for a computational model of ductile fracture

Xue

Pontin

Zok

et al. 2010

Engineering Fracture Mechanics

131

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“…Because of the absence of a material length scale in the failure criterion, the predictions of the numerical simulations are inherently mesh-size dependent [Needleman and Tvergaard 1994;Gullerud et al 2000]. The mesh size, coupled with the failure strain, dictate the amount of localized deformation that occurs along the fracture plane (closely analogous to the critical displacement in cohesive zone formulations).…”

Section: 3mentioning

confidence: 99%

Dynamic shear rupture of steel plates

Nahshon

Pontin

Evans

et al. 2007

JOMMS

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Metallic sandwich panels with prismatic cores offer the potential for superior blast resistance relative to monolithic plates of equivalent areal density. However, under sufficiently high impulse, severe plastic strains can occur at the junctions of the face sheets and the core members shortly after arrival of the pressure wave but prior to significant deformation elsewhere. The potential consequence is localized shear rupture with minimal plastic dissipation. To characterize this failure mode, a combined experimentalnumerical protocol has been used to ascertain the plastic strain for dynamic shear rupture of ductile metals. The experimental component involves firing cylindrical projectiles through plates of the targeted materials and monitoring changes in projectile velocity during penetration. With appropriate combinations of plate thickness and projectile velocity, penetration occurs through propagation of an annular shear crack. In parallel, a numerical model of dynamic deformation and rupture has been employed to infer the critical strain through comparisons with projectile velocity change measurements. Experiments and analyses have been performed on both 304 stainless steel and superaustenitic AL6XN. Effects of mesh size on the resolution of the predicted strain distribution and the plastic dissipation associated with penetration are addressed.

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Simulation of ductile crack growth using computational cells: numerical aspects

Cited by 114 publications

References 32 publications

On localization and void coalescence as a precursor to ductile fracture

On localization and void coalescence as a precursor to ductile fracture

Calibration procedures for a computational model of ductile fracture

Dynamic shear rupture of steel plates

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