Micro-mechanics based cohesive zone modeling of full scale ductile plate tearing: From initiation to steady-state

Abstract

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Parameter window for assisted crack tip flipping: Studied by a shear extended Gurson model

“…The crack subsequently flips its orientation to the other side (−45 • ) when the twisting motion is reversed. This has to do with the combined effect of the rate at which damage develops (driven by f 0 and k ω ), the extent of the fracture process zone, and the thinning region immediately in front of the crack (determined by the strain hardening, N ) (also discussed in Nielsen and Hutchinson, 2012;Andersen et al, 2019). In the reference case (with N = 0.05), thinning of the plate takes place early due to the low strain hardening and the initial damage thereafter develops to propagate a slant crack some distance before the reversed twisting motion assists the crack to flip.…”

“…, where ω(σ) ∈ [0, 1]. In relation to plate tearing it is important to realize that; i) Both models put equal weight on plane strain conditions (dominating the fracture process zone, see Andersen et al, 2019), ii) The conditions in the acute angle corner where the flip initiates are the same on both sides of the plate due to the 180-degree rotational symmetry.…”

Effect of damage-related microstructural parameters on plate tearing at steady state

“…The mode I tearing problem considered here is similar to that investigated in Nielsen and Hutchinson (2012); Andersen et al (2018b), where large-scale 3D steady-state plate tearing is boiled down to an approximate 2D plane strain setup. The elastic unloading domain above and below the thinning region essentially restricts the deformation in the FPZ such that a plane strain condition can be assumed near the crack tip (an assumption supported in a recent full 3D study by Andersen et al, 2018a). Thus, in the 2D plane strain setup, a cross section in the x 1 x 2 -plane with an initial aspect ratio of H 0 /W 0 is imagined to be cut from the plate, and loaded in tension along the x 2 -direction to mimic a far-field mode I loading (see Fig.…”

“…The current approach to ductile plate tearing in the literature, based on Gurson-like porous plasticity finite element (FE) models with a homogeneous material distribution in the entire fracture process zone (FPZ), cannot provide an unambiguous answer to the above question. For a sufficiently fine discretized plate with a homogenized porosity distribution, the crack propagates in a 45 • orientated shear band for a wide range of material properties (Mathur et al, 1996;Felter and Nielsen, 2017;Andersen et al, 2018a). In fact, lowering the initial porosity and/or increasing the hardening capacity of the plate material while keeping the mesh unchanged can lead to a shift from slant to flat crack propagation.…”

Cohesive GTN model for ductile fracture simulation

“…The CZM is thus fully determined by the data of some mechanical surface parameters as cohesive energy and toughness [16,18,19]. It is worth noting that the particular case of the simulation of tearing of ductile metal plates with the help of cohesive zone models has recently given rise to several papers [20][21][22][23]. As pointed out by [23], cohesive zone modeling is often combined in practical situations with shell modeling.…”