Simulation of Fracture Using a Mesh-Dependent Fracture Criterion in the Discrete Element Method

Dimaki, Andrey V.; Shilko, Evgeny V.; Psakhie, S. G.; Popov, Valentin L.

doi:10.22190/fume171229010d

Cited by 9 publications

(7 citation statements)

References 18 publications

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“…Note that parameters σ c and σ t used in the model for describing unlinking processes should be chosen mesh-dependent to provide mesh-independent macroscopic behavior 16 (see details below in the Section "Methods"). However, their ratio a = σ c /σ t is mesh-independent, and it is only this ratio which enters into the right part of the macroscopic criteria (3) for various wear modes.…”

Section: Discussionmentioning

confidence: 99%

“…The criterion suggested in 36 was validated in 37 by comparison with existing exact analytical solutions of adhesive problems and by direct comparison with specially designed experiments allowing observation of propagation of an adhesive crack. Later, the authors of the paper 16 implemented this criterion in the method of Movable Cellular Automata and showed that, indeed, the introduction of the mesh-dependent "local fracture criterion" guarantees the mesh-independent behavior of the material. The immediate implication of this "mesh dependency" of local fracture criteria is that dimensional parameters of these criteria do not rigorously correspond to macroscopic material property.…”

Section: Keystones Of the Model Of Element-element Interactionmentioning

confidence: 99%

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Role of Adhesion Stress in Controlling Transition between Plastic, Grinding and Breakaway Regimes of Adhesive Wear

Dimaki

Shilko

Dudkin

et al. 2020

Sci Rep

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A discrete-element based model of elastic-plastic materials with non-ideal plasticity and with an account of both cohesive and adhesive interactions inside the material is developed and verified. Based on this model, a detailed study of factors controlling the modes of adhesive wear is performed. Depending on the material and loading parameters, we observed three main modes of wear: slipping, plastic grinding, cleavage, and breakaway. We find that occurrence of a particular mode is determined by the combination of two dimensionless material parameters: (1) the ratio of the adhesive stress to the pure shear strength of the material, and (2) sensitivity parameter of material shear strength to local pressure. the case study map of asperity wear modes in the space of these parameters has been constructed. Results of this study further develop the findings of the widely discussed studies by the groups of J.-f. Molinari and L. pastewka.Adhesive wear is a complex, multiscale and still poorly understood phenomenon 1-3 . This kind of wear occurs in contact pairs where materials of interacting bodies are characterized by equal or similar values of hardness with the possible transfer of material from one surface to the opposite one. Since the publication of Rabinowicz from 1958 4 , it is known that adhesive wear is controlled by the relation of material parameters including elastic modulus, hardness and specific surface energy 4,5 . In a series of recent works by Aghababaei, Molinari et al., it was shown that adhesive wear may develop in two ways: 1) formation and evolution (growth or fragmentation) of wear particles or 2) plastic deformation of micro contacts accompanied by smoothing of asperities 6,7 . These studies together with works by other research groups 8-11 created a solid basis for a theoretical understanding of wear modes and opened possibilities for a new interpretation of classical concepts. In particular, the adhesive wear mode criterion by Rabinowicz was critically revised and details were disclosed of how the wear process occurs in both regimes of debris formation and plastic smoothing.The above mentioned fundamental results revealing the features of asperity fracture and wear were obtained using pseudo molecular dynamics (MD) simulation at the mesoscale, so the question remained whether these conclusions are universal and applicable to real materials. A particular problem of meso MD models consists in the difficulty of separating the plastic and adhesive properties of material as in meso molecular dynamics both of them are determined by the same interaction potential. On the mesoscopic scale, it may be necessary, firstly, to decouple strength from adhesion parameters of the material and, secondly to take into account more complex material properties such as yield stress and strain hardening, both strongly dependent on features of internal structure at lower scales (grain structure, grain boundaries, inclusions of other phases, etc.). This substantiates the need for a detailed theoretical analysis of wear r...

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Section: Discussionmentioning

confidence: 99%

Section: Keystones Of the Model Of Element-element Interactionmentioning

confidence: 99%

Role of Adhesion Stress in Controlling Transition between Plastic, Grinding and Breakaway Regimes of Adhesive Wear

Dimaki

Shilko

Dudkin

et al. 2020

Sci Rep

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show abstract

“…The benefit of the dynamic calculations becomes much more significant for any kind of nonlinearity, e.g., nonlinear constitutive behavior, microstructural inhomogeneity, nonlinear loading history, and the like. Among the numerical problems, namely, those where the explicit dynamic approach has a distinct advantage over the static one, there are contact problems in which it is quite difficult to make the implicit solution converge [4]. The drawback of the dynamic simulations is the conditional stability of the numerical scheme, which places strong restrictions on the time step value so that too many computational steps would be necessary to achieve a reasonable degree of straining at quasistatic loading rates.…”

Section: Introductionmentioning

confidence: 99%

Microstructure-Based Simulations of Quasistatic Deformation Using an Explicit Dynamic Approach

et al. 2019

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Microstructure-based simulations of the deformation processes require substantial computational resources due to the necessity of using detailed meshes with a large number of elements. An approach that considerably reduces the computational costs implies simulation of quasistatic deformation within a dynamic approach involving a solution of the motion equations rather than the equilibrium equations. It enables a transition from implicit to explicit time integration providing a significant gain in the computational capacity. In this paper, we show that the explicit dynamic approach can be successfully used in the microstructure-based simulations of quasistatic deformation, considerably reducing the computational costs without losing the information and solution accuracy. The following conditions have to be met to ensure a close agreement between the dynamic and static solutions: (i) the load velocity in the dynamic calculations must be smoothly increased to its amplitude value and then kept constant to minimize the acceleration term appearing in the equation of motion and (ii) the constitutive model employed must describe a quasi-rate-independent response. An examination of the mesh convergence and the strain-rate dependence for a polycrystalline aluminum model has supported this conclusion.

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“…As shown in Ref. [37], when applying a local mesh-independent fracture criterion, for example, the fracture criterion (3)-the magnitudes of the "ultimate" local stresses at which asperities detach from the surface or subsurface cracks nucleate are automaton-size-dependent. Therefore, the automaton size determines the quantitative characteristics of the damage and wear of the surface layer.…”

mentioning

confidence: 99%

“…Therefore, the automaton size determines the quantitative characteristics of the damage and wear of the surface layer. A promising way to eliminate this technical dependence is to apply the mesh-dependent (scaled) formulation of fracture criterion, which was first introduced and verified for adhesive contacts [38,39] and described for the particular case of the discreteelement method [37]. Use of the mesh-dependent criterion should provide more-accurate estimates of the wear characteristics, while the above-discussed regularities of the influence of coefficient  remain the same.…”

mentioning

confidence: 99%

Acoustic emission characterization of sliding wear under condition of direct and inverse transformations in low-temperature degradation aged Y-TZP and Y-TZP-AL2O3

et al. 2018

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In this research, results of the investigation of the sliding friction and wear of yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) and Y-TZP-Al 2 O 3 samples preliminarily subjected to low-temperature degradation are reported. The investigation was carried out using a pin-on-disk tribometer with simultaneous recording of acoustic emission (AE) and vibration acceleration. The sliding wear process was found to be determined by dynamic direct and inverse Y-TZP transformations detected by monoclinic and tetragonal X-ray diffraction peak ratios. The AE signals generated under direct and inverse transformations can be used to characterize wear and friction mechanisms as well as direct and inversed sliding-induced phase transformations. The AE signal energy grows with the friction coefficient and the inverse transformation degree. Reduction of the AE signal energy indicates establishing the mild wear stage caused by effective stress-induced direct martensitic transformation. The AE signal median frequency increases in the case of lower friction. Numerical studies of wear subsurface fracture under conditions of stress-induced martensitic transformation were used to elucidate the role played by the phase transformation in Y-TZP and Y-TZP-Al 2 O 3. Martensitic transformation in Y-TZP was described with use of the non-associated dilatant plasticity model. Simulation results particularly show that increase in the value of dilatancy coefficient from 0 to 0.2 is accompanied by 25%−30% reduce in characteristic length and penetration depth of sliding-induced subsurface cracks. As shown the AE may be an effective tool for in-situ monitoring the subsurface wear of materials experiencing both direct and inverse transformations.

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Simulation of Fracture Using a Mesh-Dependent Fracture Criterion in the Discrete Element Method

Cited by 9 publications

References 18 publications

Role of Adhesion Stress in Controlling Transition between Plastic, Grinding and Breakaway Regimes of Adhesive Wear

Role of Adhesion Stress in Controlling Transition between Plastic, Grinding and Breakaway Regimes of Adhesive Wear

Microstructure-Based Simulations of Quasistatic Deformation Using an Explicit Dynamic Approach

Acoustic emission characterization of sliding wear under condition of direct and inverse transformations in low-temperature degradation aged Y-TZP and Y-TZP-AL2O3

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