Crack propagation: Dynamic stochasticity and scaling

Naimark, Oleg; Barannikov, V. A.; Davydova, Marina; Plekhov, O.; Uvarov, Sergey

doi:10.1134/1.1262809

Cited by 14 publications

(10 citation statements)

References 7 publications

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“…The defect distribution in the damaged zone depends on the distribution of the defect nuclei (initial pores) and on the interaction of the defects in the defect ensemble. The application of the statistical theory to the description of the evolution of the defect ensemble allows us to develop a new description of critical phenomenastructural-scaling transitions [8]. The phenomenology developed explains different stages of the damage kinetics and self-similarity of damage localization, related to the generation of collective modes of defect response in a number of different damage-failure transitions.…”

Section: Formation Of 3d Fragmentsmentioning

confidence: 99%

The effect of initial porosity of a sample under electric explosion loading

Bannikova¹,

Uvarov²,

Naimark³

2016

AIP Conference Proceedings

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Abstract. Tubular Al 2 O 3 ceramic samples were destroyed under shock wave loading using electrical explosion wire (EEW) in a liquid. The fragments were classified into two types: quasi-two-dimensional (2D) samples, the characteristic size of which, d*, was greater than (or equal to) the tube wall thickness; and three-dimensional (3D) samples of the size d* < d. The study of the influence of the initial sample porosity indicates a direct effect on the formation of 3D fragments, and the distribution of the porosity is described by the power law function with an exponent differing from that of the 3D fragments size distribution. According to the scenario, the initial defects (pores) provide conditions for multi-site fracture of ceramics under high-rate loading. The instability of fast crack propagation leads to micro-branching, which creates conditions for the formation of the 3D objects. The 3D fragments size distribution is described by the power law, which corresponds to the micro-branch distribution.

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Section: Formation Of 3d Fragmentsmentioning

confidence: 99%

The effect of initial porosity of a sample under electric explosion loading

Bannikova¹,

Uvarov²,

Naimark³

2016

AIP Conference Proceedings

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“…The description of the failure wave phenomenon was proposed by Naimark et al [8,9] after analyzing the damage localization dynamics in terms of a self-similar solution for the microshear density. This solution describes qualitative changes in the microshear density kinetics that allows defining failure waves as a specific ("slow dynamics") collective mode in the microshear ensemble that could be excited due to the pass of a shock wave.…”

mentioning

confidence: 99%

“…of mesoscopic defects and the influence of thermal and structural fluctuations involved in the damage accumulation process, the formulation of a statistical problem concerning the defect distribution function was proposed by Naimark [9] in terms of the solution to the Fokker-Plank equation in the phase space of characteristic mesodefect variables.…”

mentioning

confidence: 99%

Collective modes in the microshear ensemble as a mechanism of the failure wave

et al. 2008

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Results of theoretical and experimental study of failure wave phenomena are presented. A description of the failure wave phenomenon was proposed in terms of a self-similar solution for the microshear density. The mechanisms of failure wave generation and propagation were classified as a delayed failure with the delay time corresponding to the time of excitation of self-similar blow-up collective modes in a microshear ensemble. Experimental study of the mechanism of the failure wave generation and propagation was carried out using a fused quartz rod and included the Taylor test with high-speed framing. The results obtained confirmed the "delayed" mechanism of the failure wave generation and propagation.Introduction. The phenomenon of a failure wave in brittle materials has been the subject of intensive study during the last two decades [1-3]. The term "failure wave" was introduced by Galin and Cherepanov [4] as the limit case of damage evolution, where the number of microshears is large enough for the determination of the front with a characteristic group velocity. This front separates the structured material from the failed area. Rasorenov et al. [1] were the first to observe the phenomenon of delayed failure behind an elastic wave in glass. Such a wave was introduced by Brar and Bless in [5], where the concept of a fracture wave was discussed to explain the nature of the elastic limit. A failure wave appeared in shocked brittle materials (glasses, ceramics) as a particular failure mode in which they lose strength behind the propagating front. Generally, the interest to the failure wave phenomenon is initiated by the still open problem of physical interpretation of traditionally used material characteristics such as the Hugoniot elastic limits, dynamic strength, and relaxation mechanism of elastic precursor.Qualitative changes in silicate glasses behind the failure wave, e.g., an increase in the refractive index, allowed Gibbons and Ahrens (1971) to qualify this effect as the structural phase transformation. These results stimulated Clifton [6] to propose a phenomenological model in which the failure front was assumed to be a propagating phase boundary. According to this model, the mechanism of failure wave nucleation and propagation results from the local densification followed by shear failure around the inhomogeneities triggered by the shock.Using high-speed photography, Paliwal et al.[7] obtained real-time data on the damage kinetics during dynamic compressive failure of a transparent AlON. The results suggest that final failure of the AlON under dynamic loading was due to the formation of a damage zone with unstable propagation of the critical crack.Statistical Model. The description of the failure wave phenomenon was proposed by Naimark et al. [8,9] after analyzing the damage localization dynamics in terms of a self-similar solution for the microshear density. This solution describes qualitative changes in the microshear density kinetics that allows defining failure waves as a specific ("slow dynamics") ...

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“…The thermodynamic and mechanical features of the elastic-plastic transition were studied in [1][2][3][4][5][6][7]. In [1], we proposed a method to estimate the energy stor age rate in a material using the results of infrared scan ning.…”

Section: Introductionmentioning

confidence: 99%

“…As a result, the most impor tant sign of a plastic flow was found to be the localiza tion of plastic deformation, which is accompanied by the localization and intensification of heat sources in a material. When calculating the intensity of heat sources in a material and determining the total energy consumed for its deformation, one can perform an integral estimation of the energy stored in an ensemble of mesodefects in order to determine the current stage of its evolution.The thermodynamic and mechanical features of the elastic-plastic transition were studied in [1][2][3][4][5][6][7]. In [1], we proposed a method to estimate the energy stor age rate in a material using the results of infrared scan ning.…”

mentioning

confidence: 99%

Elastic-plastic transition in iron: Structural and thermodynamic features

et al. 2009

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Any correspondence concerning this service should be sent to the repository Administrator : archiveouverte@ensam.eu INTRODUCTIONThe structural evolution of metallic materials dur ing plastic deformation has been extensively studied for the last hundred years. As a result, the most impor tant sign of a plastic flow was found to be the localiza tion of plastic deformation, which is accompanied by the localization and intensification of heat sources in a material. When calculating the intensity of heat sources in a material and determining the total energy consumed for its deformation, one can perform an integral estimation of the energy stored in an ensemble of mesodefects in order to determine the current stage of its evolution.The thermodynamic and mechanical features of the elastic-plastic transition were studied in [1][2][3][4][5][6][7]. In [1], we proposed a method to estimate the energy stor age rate in a material using the results of infrared scan ning. In [2], this process was considered from the for mal points of the mechanics of continua using an additionally introduced structure sensitive tensor variable, which describes the growth of mesoscopic defects. The wave character of heat dissipation in steel during the elastic-plastic transition was first experi mentally detected in [3]. The authors of [4] experi mentally studied the propagation of deformation localization waves in fcc metal single crystals (copper, nickel). Then, researchers used speckle interferometry and detected wave deformation processes in a wide range of plastic and quasi plastic materials. Kiselev [5] suggested a mathematical model for the propagation of localized plasticity waves in crystals; it is based on the double cross slip of screw dislocation segments.In this work, we continue the study of the energy dissipation [1, 2] during the elastic-plastic transition by infrared scanning. We determine the main thermo physical features of this transition at various strain rates and study the temperature kinetics of the sample and the dependence of the heat wave velocity on the number of waves and the strain rate. EXPERIMENTALWe investigated the elastic-plastic transition in iron subjected to uniaxial quasi static tension. The chemical composition of iron is given in the table.The experiment was carried out under isothermal conditions. The strain rate was varied from 10 -4 to 2 × 10 -3 s -1. To obtain reliable results, we analyzed two series of samples that were made from the same batch of armco iron and subjected to the same mechanical and heat treatment.After mechanical treatment, the samples were annealed in an oxygen free atmosphere at 800°C for 8 h. The oxygen free atmosphere was created by simulta neous annealing of the iron samples under study and additional copper samples with a developed surface.The geometry of the iron samples is shown in Fig. 1 Abstract-The structural and thermo...

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Crack propagation: Dynamic stochasticity and scaling

Cited by 14 publications

References 7 publications

The effect of initial porosity of a sample under electric explosion loading

The effect of initial porosity of a sample under electric explosion loading

Collective modes in the microshear ensemble as a mechanism of the failure wave

Elastic-plastic transition in iron: Structural and thermodynamic features

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