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Yoshitaka Umeno - One of the best experts on this subject based on the ideXlab platform.
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velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials a continuum model study
Scientific Reports, 2017Co-Authors: Atsushi Kubo, Yoshitaka UmenoAbstract:Velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials: A continuum model study
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velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials a continuum model study
Scientific Reports, 2017Co-Authors: Atsushi Kubo, Yoshitaka UmenoAbstract:Experiments of Crack Propagation in rubbers have shown that a discontinuous jump of Crack Propagation velocity can occur as energy release rate increases, which is known as the “mode transition” phenomenon. Although it is believed that the mode transition is strongly related to the mechanical properties, the nature of the mode transition had not been revealed. In this study, Dynamic Crack Propagation on an elastomer was investigated using the finite element method (FEM) with a hyperviscoelastic material model. A series of pure shear test was carried out numerically with FEM simulations and Crack velocities were measured under various values of tensile strain. As a result, our FEM simulations successfully reproduced the mode transition. The success of realising the mode transition phenomenon by a simple FEM model, which was achieved for the first time ever, helped to explain that the phenomenon occurs owing to a characteristic non-monotonic temporal development of principal stress near the Crack tip.
Jean-françois Molinari - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Crack Propagation with a variational phase-field model: limiting speed, Crack branching and velocity-toughening mechanisms
International Journal of Fracture, 2017Co-Authors: Jeremy Bleyer, Clément Roux-langlois, Jean-françois MolinariAbstract:We address the simulation of Dynamic Crack Propagation in brittle materials using a regularized phase-field description, which can also be interpreted as a damage-gradient model. Benefiting from a variational framework, the Dynamic evolution of the mechanical fields are obtained as a succession of energy minimizations. We investigate the capacity of such a simple model to reproduce specific experimental features of Dynamic in-plane fracture. These include the Crack branching phenomenon as well as the existence of a limiting Crack velocity below the Rayleigh wave speed for mode I Propagation. Numerical results show that, when a Crack accelerates, the damaged band tends to widen in a direction perpendicular to the Propagation direction, before forming two distinct macroscopic branches. This transition from a single Crack Propagation to a branched configuration is described by a well-defined master-curve of the apparent fracture energy $$\varGamma $$Γ as an increasing function of the Crack velocity. This $$\varGamma (v)$$Γ(v) relationship can be associated, from a macroscopic point of view, with the well-known velocity-toughening mechanism. These results also support the existence of a critical value of the energy release rate associated with branching: a critical value of approximately 2$$G_c$$Gc is observed i.e. the fracture energy contribution of two Crack tips. Finally, our work demonstrates the efficiency of the phase-field approach to simulate Crack Propagation Dynamics interacting with heterogeneities, revealing the complex interplay between heterogeneity patterns and branching mechanisms.
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Dynamic Crack Propagation in a heterogeneous ceramic microstructure, insights from a cohesive model
Acta Materialia, 2015Co-Authors: S.m. Taheri Mousavi, N. Richart, Cyprien Wolff, Jean-françois MolinariAbstract:A 2D plane-strain Dynamically propagating Crack under tensile loading is simulated with cohesive elements. Information of the main Crack is extracted from a diffuse Crack network with the use of graph properties. Micro-transgranular fracture properties are calibrated by comparing the Crack path transgranular fracture percentage of numerical simulations with experimental data. Results show that although weaker grain boundaries cause more deflections in the Crack path and consequently increase the Crack length and roughness, the overall toughness is decreased due to reduction of transgranular fracture. The main Crack failure mode transition at grain boundaries is compared to static (Hutchinson and Suo, 1992) and Dynamic (Xu et al., 2003) classical analytical predictions. It is observed that in many cases, before the arrival of a transgranular fracture at a grain boundary, a micro-daughter Crack starts to propagate on the interface. The Crack tip extension through this daughter Crack/mother Crack mechanism complicates the interpretation of the main Crack speed in Dynamic regime. Yet, the Dynamic analysis brings a more accurate prediction of the Crack path in microstructures compared to the static one when the data are segregated according to this mechanism.
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A rate-dependent cohesive model for simulating Dynamic Crack Propagation in brittle materials
Engineering Fracture Mechanics, 2005Co-Authors: Fenghua Zhou, Jean-françois Molinari, Tadashi ShioyaAbstract:Numerical investigations are conducted to simulate high-speed Crack Propagation in pre-strained PMMA plates. In the simulations, the Dynamic material separation is explicitly modeled by cohesive elements incorporating an initially rigid, linear-decaying cohesive law. Initial attempts using a rate-independent cohesive law failed to reproduce available experimental results as numerical Crack velocities consistently overestimate experimental observations. As proof of concept, a phenomenological rate-dependent cohesive law, which bases itself on the physics of microCracking, is introduced to modulate the cohesive law with the macroscopic Crack velocity. We then generalize this phenomenological approach by establishing a rate-dependent cohesive law, which relates the traction to the effective displacement and rate of change of effective displacement. It is shown that this new model produces numerical results in good agreement with experimental data. The analysis demonstrates that the simulation of high-speed Crack Propagation in brittle structures necessitates the use of rate-dependent cohesive models, which account for the complicated rate-process of Dynamic fracture at the propagating Crack tip.
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Dynamic Crack Propagation with cohesive elements a methodology to address mesh dependency
International Journal for Numerical Methods in Engineering, 2004Co-Authors: Fenghua Zhou, Jean-françois MolinariAbstract:In this paper, two brittle fracture problems are numerically simulated: the failure of a ceramic ring under centrifugal loading and Crack branching in a PMMA strip. A three-dimensional finite element package in which cohesive elements are Dynamically inserted has been developed. The cohesive elements' strength is chosen to follow a modified weakest link Weibull distribution. The probability of introducing a weak cohesive element is set to increase with the cohesive element size. This reflects the physically based effect according to which larger elements are more likely to contain defects. The calculations illustrate how the area dependence of the Weibull model can be used to effectively address mesh dependency. On the other hand, regular Weibull distributions have failed to reduce mesh dependency for the examples shown in this paper. The ceramic ring calculations revealed that two distinct phenomena appear depending on the magnitude of the Weibull modulus. For low Weibull modulus, the fragmentation of the ring is dominated by heterogeneities. Whereas many Cracks were generated, few of them could propagate to the outer surface. Monte Carlo simulations revealed that for highly heterogeneous rings, the number of small fragments was large and that few large fragments were generated. For high Weibull modulus, signifying that the ring is close to being homogeneous, the fragmentation process was very different. Monte Carlo simulations highlighted that a larger number of large fragments are generated due to Crack branching. Copyright (C) 2003 John Wiley Sons, Ltd.
Timon Rabczuk - One of the best experts on this subject based on the ideXlab platform.
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phase field modeling of fluid driven Dynamic Cracking in porous media
Computer Methods in Applied Mechanics and Engineering, 2019Co-Authors: Xiaoying Zhuang, Shuwei Zhou, Timon RabczukAbstract:Abstract A phase field model for fluid-driven Dynamic Crack Propagation in poroelastic media is proposed. Therefore, classical Biot poroelasticity theory is applied in the porous medium while arbitrary Crack growth is naturally captured by the phase field model. We also account for the transition of the fluid property from the intact medium to the fully broken one by employing indicator functions. We employ a staggered scheme and implement our approach into the software package COMSOL Multiphysics. Our approach is first verified through three classical benchmark problems which are compared to analytical solutions for Dynamic consolidation and pressure distribution in a single Crack and in a specimen with two sets of joints. Subsequently, we present several 2D and 3D examples of Dynamic Crack branching and their interaction with pre-existing natural fractures . All presented examples demonstrate the capability of the proposed approach of handling Dynamic Crack Propagation, branching and coalescence of fluid-driven fracture.
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phase field modeling of quasi static and Dynamic Crack Propagation comsol implementation and case studies
Advances in Engineering Software, 2018Co-Authors: Timon Rabczuk, Shuwei Zhou, Xiaoying ZhuangAbstract:Abstract The phase-field model (PFM) represents the Crack geometry in a diffusive way without introducing sharp discontinuities. This feature enables PFM to effectively model Crack Propagation compared with numerical methods based on discrete Crack model, especially for complex Crack patterns. Due to the involvement of “phased field”, phase-field method can be essentially treated a multifield problem even for pure mechanical problem. Therefore, it is supposed that the implementation of PFM based on a software developer that especially supports the solution of multifield problems should be more effective, simpler and more efficient than PFM implemented on a general finite element software. In this work, the authors aim to devise a simple and efficient implementation of phase-field model for the modelling of quasi-static and Dynamic fracture in the general purpose commercial software developer, COMSOL Multiphysics. Notably only the tensile stress induced Crack is accounted for Crack evolution by using the decomposition of elastic strain energy. The width of the diffusive Crack is controlled by a length-scale parameter. Equations that govern body motion and phase-field evolution are written into different modules in COMSOL, which are then coupled to a whole system to be solved. A staggered scheme is adopted to solve the coupled system and each module is solved sequentially during one time step. A number of 2D and 3D examples are tested to investigate the performance of the present implementation. Our simulations show good agreement with previous works, indicating the feasibility and validity of the COMSOL implementation of PFM.
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a computational library for multiscale modeling of material failure
Computational Mechanics, 2014Co-Authors: Hossein Talebi, Mohammad Silani, Pierre Kerfriden, Stéphane Bordas, Timon RabczukAbstract:We present an open-source software framework called PERMIX for multiscale modeling and simulation of fracture in solids. The framework is an object oriented open-source effort written primarily in Fortran 2003 standard with Fortran/C++ interfaces to a number of other libraries such as LAMMPS, ABAQUS, LS-DYNA and GMSH. Fracture on the continuum level is modeled by the extended finite element method (XFEM). Using several novel or state of the art methods, the piece software handles semi-concurrent multiscale methods as well as concurrent multiscale methods for fracture, coupling two continuum domains or atomistic domains to continuum domains, respectively. The efficiency of our open-source software is shown through several simulations including a 3D Crack modeling in clay nanocomposites, a semi-concurrent FE-FE coupling, a 3D Arlequin multiscale example and an MD-XFEM coupling for Dynamic Crack Propagation.
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a meshfree method based on the local partition of unity for cohesive Cracks
Computational Mechanics, 2007Co-Authors: Timon RabczukAbstract:We will present a meshfree method based on the local partition of unity for cohesive Cracks. The Cracks are described by a jump in the displacement field for particles whose domain of influence is cut by the Crack. Particles with partially cut domain of influence are enriched with branch functions. Crack Propagation is governed by the material stability condition. Due to the smoothness and higher order continuity, the method is very accurate which is demonstrated for several quasi static and Dynamic Crack Propagation examples.
Atsushi Kubo - One of the best experts on this subject based on the ideXlab platform.
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velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials a continuum model study
Scientific Reports, 2017Co-Authors: Atsushi Kubo, Yoshitaka UmenoAbstract:Velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials: A continuum model study
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velocity mode transition of Dynamic Crack Propagation in hyperviscoelastic materials a continuum model study
Scientific Reports, 2017Co-Authors: Atsushi Kubo, Yoshitaka UmenoAbstract:Experiments of Crack Propagation in rubbers have shown that a discontinuous jump of Crack Propagation velocity can occur as energy release rate increases, which is known as the “mode transition” phenomenon. Although it is believed that the mode transition is strongly related to the mechanical properties, the nature of the mode transition had not been revealed. In this study, Dynamic Crack Propagation on an elastomer was investigated using the finite element method (FEM) with a hyperviscoelastic material model. A series of pure shear test was carried out numerically with FEM simulations and Crack velocities were measured under various values of tensile strain. As a result, our FEM simulations successfully reproduced the mode transition. The success of realising the mode transition phenomenon by a simple FEM model, which was achieved for the first time ever, helped to explain that the phenomenon occurs owing to a characteristic non-monotonic temporal development of principal stress near the Crack tip.
Peter Andrew Mataga - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Crack Propagation in piezoelectric materials part ii vacuum solution
Journal of The Mechanics and Physics of Solids, 1996Co-Authors: Peter Andrew MatagaAbstract:Abstract In Part I of this work, antiplane Dynamic Crack Propagation in piezoelectric materials was studied under the condition that Crack surfaces behaved as though covered with a conducting electrode. Piezoelectric surface wave phenomena were clearly seen to be critical to the behavior of the moving Crack. Closed form results were obtained for stress and electric displacement intensities at the Crack tip in the subsonic Crack speed range; the major result is that the energy release rate vanishes as the Crack speed approaches the surface (Bleustein-Gulyaev) wave speed. In this paper, an alternative assumption is made that between the growing Crack surfaces there is a permeable vacuum free space, in which the electrostatic potential is nonzero. By coupling the piezoelectric equations of the solid phase with the electric charge equation in the vacuum region, a closed form solution is again obtained. In contrast to the electrode case of Part I, this case allows both applied charge and applied traction loading. In addition, the work of Part I is extended to examine piezoelectric Crack Propagation over the full velocity range of subsonic, transonic and supersonic speeds. Several aspects of the results are explored. The energy release rate in this case does not go to zero when the Crack propagating velocity approaches the surface wave speed, even if there is only applied traction loading. When the Crack exceeds the Bleustein-Gulyaev wave speed, the character of the Crack-tip singularities of the physical fields depends on both speed regime and type of loading. At the other extreme, the quasi-static limit of the Dynamic solution furnishes a set of new static solutions. The general permeability assumptions made here allow for fully coupled conditions that are ruled out by the a priori interfacial assumptions made in previously published solutions.
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Dynamic Crack Propagation in piezoelectric materials part i electrode solution
Journal of The Mechanics and Physics of Solids, 1996Co-Authors: Peter Andrew MatagaAbstract:Abstract An analysis is performed for the transient response of a semi-infinite, anti-plane Crack propagating in a hexagonal piezoelectric medium. The mixed boundary value problem is solved by transform methods together with the Wiener-Hopf and Cagniard-de Hoop techniques. As a special case, a closed form solution is obtained for constant speed Crack Propagation under external anti-plane shear loading with the conducting electrode type of electric boundary condition imposed on the Crack surface (a second type of boundary condition is considered in Part II of this work). In purely elastic, transversely isotropic elastic solids, there is no antiplane mode surface wave. However, for certain orientations of piezoelectric materials, a surface wave will occur—the BleusteindashGulyaev wave. Since surface wave speeds strongly influence Crack Propagation, the nature of antiplane Dynamic fracture in piezoelectric materials is fundamentally different from that in purely elastic solids, exhibiting many features only associated with the indashplane modes in the elastic case. For a general distribution of Crack face tractions, the Dynamic stress intensity factor and the Dynamic electric displacement intensity factor are derived and discussed in detail for the electrode case. As for inplane elastoDynamic fracture, the stress intensity factor and energy release rate go to zero as the Crack Propagation velocity approaches the surface wave speed. However, the electric displacement intensity does not vanish.
