The Experts below are selected from a list of 9138 Experts worldwide ranked by ideXlab platform
Rodrigue Desmorat - One of the best experts on this subject based on the ideXlab platform.
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Lode angle dependency due to Anisotropic Damage
International Journal of Damage Mechanics, 2020Co-Authors: A Mattiello, Rodrigue DesmoratAbstract:The lode angle dependency introduced by Anisotropic Damage evolution laws is analyzed in detail for initially isotropic materials. Many rupture criteria are obtained, under the proportional loading...
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Anisotropic Damage modeling of concrete materials
International Journal of Damage Mechanics, 2015Co-Authors: Rodrigue DesmoratAbstract:An Anisotropic Damage model is proposed for concrete materials. As required by thermodynamics a single Damage variable, tensorial, is considered for any loading: as a state variable it represents t...
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Intrinsic dissipation of a modular Anisotropic Damage model : application to concrete under impact
Engineering Fracture Mechanics, 2014Co-Authors: Marion Chambart, Rodrigue Desmorat, Fabrice GatuingtAbstract:Based on the mathematical proof of the positivity of the dissipation due to Anisotropic Damage, different numerical scheme to compute such a dissipation in concrete structures are proposed. The positivity of intrinsic dissipation for the considered modular Anisotropic Damage model is first checked in the case of Willam non-proportional loading test, then checked for different impact tests on concrete structures. Both the consequences of the modeling of the strain rate effect in tension (from visco-Damage) and of the Damage deactivation (micro-cracks closure) for alternated loadings are studied.
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Dynamic cracks initiation, propagation, coalescence, speed and arrest from Anisotropic Damage mechanics analysis
2010Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Marion Chambart, Daniel Guilbaud, Fédérale De LausanneAbstract:Continuous Anisotropic Damage is a quite natural modeling of material degradation when structural computations have to be performed. Loading induced Damage in quasi-brittle materials such as concrete is strongly Anisotropic [1] and strain localization in structures most often leads to an oriented cracking pattern. A five parameter Anisotropic Damage model has been proposed [6], taking advantage of the induced anisotropy. The Damage is represented by a second order tensor. Its evolution is governed by the positive strains (the extensions) in a framework independent formulation, fulfilling the second principle of thermodynamics. The mathematical properties of the model (for instance a thermodynamics potential which can be continuously differentiated) have allowed for robust computations in quasi-statics. Mesh independence is gained from nonlocal integral enhancement. In dynamics and impact applications, the so-called strain rate effect, of an apparent increase of the ultimate stress, has to be taken into account. This is simply done here in the visco-Damage framework [2, 3, 4] by considering an Anisotropic delay Damage law bounding the Damage rate at high strain rates [5]. Such a kind of evolution law regularizes the computations (with no need of non local averaging). One first presents computations of Hopkinson bar tests on concrete illustrating this feature. Then is presented the computation of Pontirolli's structural example of a blast impacted reinforced plate [7]. Such an example is quite nice to point out the possibility of continuous Anisotropic Damage modelling in dynamics: • cracks initiation by stress softening and strain localization, with no need of initial flaws in Continuum Damage Mechanics analyses, • cracks propagation as the propagation of localized Damage zones,
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Non standard thermodynamics framework for robust computations with induced Anisotropic Damage
International Journal of Damage Mechanics, 2010Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Frédéric RagueneauAbstract:Many Anisotropic Damage models have been proposed for different materials, including concrete. The main drawback of the corre- sponding analyses is that a large number of material parameters is often introduced, leading to identification difficulties but also to model complex- ity and associated numerical difficulties. It is also sometimes difficult to ensure the continuity of the stresses if the quasi-unilateral effect of micro- cracks closure and the dissymmetry tension/compression are represented. In order to solve those difficulties, one proposes to write the Damage models in a specific non standard thermodynamics framework. The dam- age states are represented by a symmetric second order tensor and the Damage rate is assumed governed by a positive second order tensor having a clear meanning: the absolute or the positive value of the plastic strain rate tensor for ductile materials, the positive part of the total strain tensor in quasi-brittle materials. Such a non standard feature makes the proof of the the positivity of the intrinsic dissipation necessary. This important proof is given in the considered framework for any Damage law ensuring (Anisotropic) Damage increase and for any case, 3D, proportional or non proportional. This extends then to induced anisotropy the isotropic case property of a positive Damage rate as a sufficient condition for the ther- modynamics second principle to be fulfilled. Altogether with the fact that the thermodynamics potential can be con- tinuously differentiated, the Anisotropic Damage model for concrete (build in this framework) allows for robust Finite Element implementation. Both space (classical nonlocal with internal length, nonlocal with internal time) and time regularizations (visco- or delay-Damage) are used and applied to quasi-static and dynamic cases. Examples on concrete and reinforced concrete structures are given.
S. Valliappan - One of the best experts on this subject based on the ideXlab platform.
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Analysis of random Anisotropic Damage mechanics problems of rock mass
Rock Mechanics and Rock Engineering, 1990Co-Authors: Zhang Wohua, S. ValliappanAbstract:Probabilistic analysis of random Anisotropic Damage mechanics problems is proposed in Parts of I and II. In Part I, based on the measured characteristics of random crack distribution on the surface of a rock specimen, a probabilistic law of Damage variables for rock mass was presented as a Beta distribution by using the Monte-Carlo statistical simulation method. In part II, statistical estimation of a Damage state and properties of random Damaged rock mass are evaluated by Rosenblueth's point estimate method. Two stability problems involving randomly Damaged rock mass have been analyzed using the finite element method, to illustrate the statistical estimation method.
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Analysis of random Anisotropic Damage mechanics problems of rock mass
Rock Mechanics and Rock Engineering, 1990Co-Authors: Zhang Wohua, S. ValliappanAbstract:A probabilistic analysis method of random Anisotropic Damage mechanics problems is proposed in parts I and II. In part I, based on the measured characteristics of random crack distribution on the surface of a rock specimen, a probabilistic distribution law of Damage variables for rock mass is presented as a Beta distribution by using the Monte-Carlo statistical simulation method. In part II, statistical estimation of a Damage state and properties of random Damaged rock mass are evaluated by Rosenblueth's point estimate method. Combining with the F. E. method, rock mechanics problem for random Damaged state have been analyzed.
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Finite element analysis of Anisotropic Damage mechanics problems
Engineering Fracture Mechanics, 1990Co-Authors: S. Valliappan, V. Murti, Zhang WohuaAbstract:Abstract Elastic constitutive relationships for Anisotropic Damage mechanics have been developed in this paper. Implementation of these constitutive equations in the finite element analysis is explained. Validation of these relations is provided in the form of comparison of numerical results with the available experimental results. The application of these relationships to an Anisotropic Damaged foundation problem is discussed.
Frédéric Ragueneau - One of the best experts on this subject based on the ideXlab platform.
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Non standard thermodynamics framework for robust computations with induced Anisotropic Damage
International Journal of Damage Mechanics, 2010Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Frédéric RagueneauAbstract:Many Anisotropic Damage models have been proposed for different materials, including concrete. The main drawback of the corre- sponding analyses is that a large number of material parameters is often introduced, leading to identification difficulties but also to model complex- ity and associated numerical difficulties. It is also sometimes difficult to ensure the continuity of the stresses if the quasi-unilateral effect of micro- cracks closure and the dissymmetry tension/compression are represented. In order to solve those difficulties, one proposes to write the Damage models in a specific non standard thermodynamics framework. The dam- age states are represented by a symmetric second order tensor and the Damage rate is assumed governed by a positive second order tensor having a clear meanning: the absolute or the positive value of the plastic strain rate tensor for ductile materials, the positive part of the total strain tensor in quasi-brittle materials. Such a non standard feature makes the proof of the the positivity of the intrinsic dissipation necessary. This important proof is given in the considered framework for any Damage law ensuring (Anisotropic) Damage increase and for any case, 3D, proportional or non proportional. This extends then to induced anisotropy the isotropic case property of a positive Damage rate as a sufficient condition for the ther- modynamics second principle to be fulfilled. Altogether with the fact that the thermodynamics potential can be con- tinuously differentiated, the Anisotropic Damage model for concrete (build in this framework) allows for robust Finite Element implementation. Both space (classical nonlocal with internal length, nonlocal with internal time) and time regularizations (visco- or delay-Damage) are used and applied to quasi-static and dynamic cases. Examples on concrete and reinforced concrete structures are given.
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Anisotropic Damage modelling of biaxial behaviour and rupture of concrete structures
Computers and Concrete, 2008Co-Authors: Frédéric Ragueneau, Rodrigue Desmorat, Fabrice GatuingtAbstract:This paper deals with Damage induced anisotropy modeling for concrete-like materials. A thermodynamics based constitutive relationship is presented coupling Anisotropic Damage and elasticity, the main idea of the model being that Damage anisotropy is responsible for the dissymmetry tension/compression. A strain written Damage criterion is considered (Mazars criterion extended to anisotropy in the initial model). The biaxial behavior of a family of Anisotropic Damage model is analyzed through the effects of yield surface modifications by the introduction of new equivalent strains.
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Anisotropic Damage modelling of biaxial behaviour and rupture of concrete structures
Computers & Concrete, 2008Co-Authors: Frédéric Ragueneau, Rodrigue Desmorat, Fabrice GatuingtAbstract:This paper deals with Damage induced anisotropy modelling for concrete-like materials. A thermodynamics based constitutive relationship is presented coupling Anisotropic Damage and elasticity. The biaxial behaviour of such a model is analysed through the effects of yield surface modifications by the introduction of new equivalent strains.
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Thermodynamics framework for robust computations with induced Anisotropic Damage
2007Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Frédéric RagueneauAbstract:Many Anisotropic Damage models have been proposed for different materials, including concrete. The main drawback of the corresponding analyses is that a large number of material parameters is often introduced, leading to identification difficulties but also to models complexity and associated numerical difficulties. It is also sometimes difficult to ensure the continuity of the stresses if the quasi-unilateral effect of microcracks closure and the dissymmetry tension/compression are represented. One considers here an Anisotropic Damage model with a restricted number of material parameters (5 including the Young's modulus and Poisson's ratio of the initially isotropic material) and built in the thermodynamics framework. The large dissymmetry tension/compression response of concrete is due to the loading induced Damage anisotropy. A non standard thermodynamics framework is used with Damage states represented by a symmetric second order tensor and with a Damage rate governed by the positive part of the strain tensor. The proof of the positivity of the intrinsic dissipation is given for any Damage law ensuring (Anisotropic) Damage increase – in terms of positive principal values of the Damage rate tensor. This extends then to induced anisotropy the isotropic case property of a positive Damage rate. Altogether with the fact that the thermodynamics potential can be continuously differentiated , the considered Anisotropic Damage model allows for robust Finite Element implementation. Both space and time regularizations are used and applied to quasi-static and dynamic cases. Examples on concrete and reinforced concrete structures are given, with the consideration of either nonlocal Mazars criterion or of Mazars criterion regularized with viscous Damage.
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Nonlocal Anisotropic Damage model and related computational aspects for quasi-brittle materials
Engineering Fracture Mechanics, 2007Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Frédéric RagueneauAbstract:Abstract A three-dimensional Damage model with induced Damage anisotropy is proposed for quasi-brittle materials such as concrete. The thermodynamics framework is used, considering then a single second-order tensorial Damage variable whatever the intensity and the sign of the loading. The quasi-unilateral conditions of micro-cracks closure are written on the hydrostatic stress only. Altogether with the consideration of Damage laws ensuring a Damage rate proportional to the positive part of the strain tensor this is sufficient to model a strongly different behavior due to Damage in tension and in compression. A proof of the positivity of the intrinsic dissipation due to such an induced Anisotropic Damage is given. An efficient scheme for the implementation of the Damage model in commercial Finite Element codes is then detailed and numerical examples of structural failures are given. Plain concrete, reinforced and pre-stressed concrete structures are computed up to high Damage level inducing yielding of the reinforcement steels. Local and nonlocal computations are performed. A procedure for the control of rupture is proposed. It is a key point making the computations with Anisotropic Damage truly efficient.
Zhang Wohua - One of the best experts on this subject based on the ideXlab platform.
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Effects of symmetrisation of net-stress tensor in Anisotropic Damage models
International Journal of Fracture, 2001Co-Authors: Zhang Wohua, Chen Yun-minAbstract:In Anisotropic Damage mechanics, matrix symmetrisation scheme or treatment in net-stress space is used for mathematical convenience without a strong physical basis. Two different symmetrisation schemes for Anisotropic Damage model have been compared with the non-symmetrised models proposed for this study. The effects of these symmetrisation schemes are assessed in this paper by deriving the corresponding explicit form of various key parameters for Anisotropic Damage modelling. It is found that in most cases the symmetrisation process markedly influences the resultant parameters that may lead to spurious results. Hence such a symmetrisation treatment of an Anisotropic Damage model should be carefully examined. A numerical analysis of a direct shear experiment is also presented to support the assessment of the effects of the symmetrisation schemes considered.
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Analysis of random Anisotropic Damage mechanics problems of rock mass
Rock Mechanics and Rock Engineering, 1990Co-Authors: Zhang Wohua, S. ValliappanAbstract:Probabilistic analysis of random Anisotropic Damage mechanics problems is proposed in Parts of I and II. In Part I, based on the measured characteristics of random crack distribution on the surface of a rock specimen, a probabilistic law of Damage variables for rock mass was presented as a Beta distribution by using the Monte-Carlo statistical simulation method. In part II, statistical estimation of a Damage state and properties of random Damaged rock mass are evaluated by Rosenblueth's point estimate method. Two stability problems involving randomly Damaged rock mass have been analyzed using the finite element method, to illustrate the statistical estimation method.
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Analysis of random Anisotropic Damage mechanics problems of rock mass
Rock Mechanics and Rock Engineering, 1990Co-Authors: Zhang Wohua, S. ValliappanAbstract:A probabilistic analysis method of random Anisotropic Damage mechanics problems is proposed in parts I and II. In part I, based on the measured characteristics of random crack distribution on the surface of a rock specimen, a probabilistic distribution law of Damage variables for rock mass is presented as a Beta distribution by using the Monte-Carlo statistical simulation method. In part II, statistical estimation of a Damage state and properties of random Damaged rock mass are evaluated by Rosenblueth's point estimate method. Combining with the F. E. method, rock mechanics problem for random Damaged state have been analyzed.
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Finite element analysis of Anisotropic Damage mechanics problems
Engineering Fracture Mechanics, 1990Co-Authors: S. Valliappan, V. Murti, Zhang WohuaAbstract:Abstract Elastic constitutive relationships for Anisotropic Damage mechanics have been developed in this paper. Implementation of these constitutive equations in the finite element analysis is explained. Validation of these relations is provided in the form of comparison of numerical results with the available experimental results. The application of these relationships to an Anisotropic Damaged foundation problem is discussed.
Fabrice Gatuingt - One of the best experts on this subject based on the ideXlab platform.
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Intrinsic dissipation of a modular Anisotropic Damage model : application to concrete under impact
Engineering Fracture Mechanics, 2014Co-Authors: Marion Chambart, Rodrigue Desmorat, Fabrice GatuingtAbstract:Based on the mathematical proof of the positivity of the dissipation due to Anisotropic Damage, different numerical scheme to compute such a dissipation in concrete structures are proposed. The positivity of intrinsic dissipation for the considered modular Anisotropic Damage model is first checked in the case of Willam non-proportional loading test, then checked for different impact tests on concrete structures. Both the consequences of the modeling of the strain rate effect in tension (from visco-Damage) and of the Damage deactivation (micro-cracks closure) for alternated loadings are studied.
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Dynamic cracks initiation, propagation, coalescence, speed and arrest from Anisotropic Damage mechanics analysis
2010Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Marion Chambart, Daniel Guilbaud, Fédérale De LausanneAbstract:Continuous Anisotropic Damage is a quite natural modeling of material degradation when structural computations have to be performed. Loading induced Damage in quasi-brittle materials such as concrete is strongly Anisotropic [1] and strain localization in structures most often leads to an oriented cracking pattern. A five parameter Anisotropic Damage model has been proposed [6], taking advantage of the induced anisotropy. The Damage is represented by a second order tensor. Its evolution is governed by the positive strains (the extensions) in a framework independent formulation, fulfilling the second principle of thermodynamics. The mathematical properties of the model (for instance a thermodynamics potential which can be continuously differentiated) have allowed for robust computations in quasi-statics. Mesh independence is gained from nonlocal integral enhancement. In dynamics and impact applications, the so-called strain rate effect, of an apparent increase of the ultimate stress, has to be taken into account. This is simply done here in the visco-Damage framework [2, 3, 4] by considering an Anisotropic delay Damage law bounding the Damage rate at high strain rates [5]. Such a kind of evolution law regularizes the computations (with no need of non local averaging). One first presents computations of Hopkinson bar tests on concrete illustrating this feature. Then is presented the computation of Pontirolli's structural example of a blast impacted reinforced plate [7]. Such an example is quite nice to point out the possibility of continuous Anisotropic Damage modelling in dynamics: • cracks initiation by stress softening and strain localization, with no need of initial flaws in Continuum Damage Mechanics analyses, • cracks propagation as the propagation of localized Damage zones,
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Non standard thermodynamics framework for robust computations with induced Anisotropic Damage
International Journal of Damage Mechanics, 2010Co-Authors: Rodrigue Desmorat, Fabrice Gatuingt, Frédéric RagueneauAbstract:Many Anisotropic Damage models have been proposed for different materials, including concrete. The main drawback of the corre- sponding analyses is that a large number of material parameters is often introduced, leading to identification difficulties but also to model complex- ity and associated numerical difficulties. It is also sometimes difficult to ensure the continuity of the stresses if the quasi-unilateral effect of micro- cracks closure and the dissymmetry tension/compression are represented. In order to solve those difficulties, one proposes to write the Damage models in a specific non standard thermodynamics framework. The dam- age states are represented by a symmetric second order tensor and the Damage rate is assumed governed by a positive second order tensor having a clear meanning: the absolute or the positive value of the plastic strain rate tensor for ductile materials, the positive part of the total strain tensor in quasi-brittle materials. Such a non standard feature makes the proof of the the positivity of the intrinsic dissipation necessary. This important proof is given in the considered framework for any Damage law ensuring (Anisotropic) Damage increase and for any case, 3D, proportional or non proportional. This extends then to induced anisotropy the isotropic case property of a positive Damage rate as a sufficient condition for the ther- modynamics second principle to be fulfilled. Altogether with the fact that the thermodynamics potential can be con- tinuously differentiated, the Anisotropic Damage model for concrete (build in this framework) allows for robust Finite Element implementation. Both space (classical nonlocal with internal length, nonlocal with internal time) and time regularizations (visco- or delay-Damage) are used and applied to quasi-static and dynamic cases. Examples on concrete and reinforced concrete structures are given.
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Anisotropic Damage modelling of biaxial behaviour and rupture of concrete structures
Computers and Concrete, 2008Co-Authors: Frédéric Ragueneau, Rodrigue Desmorat, Fabrice GatuingtAbstract:This paper deals with Damage induced anisotropy modeling for concrete-like materials. A thermodynamics based constitutive relationship is presented coupling Anisotropic Damage and elasticity, the main idea of the model being that Damage anisotropy is responsible for the dissymmetry tension/compression. A strain written Damage criterion is considered (Mazars criterion extended to anisotropy in the initial model). The biaxial behavior of a family of Anisotropic Damage model is analyzed through the effects of yield surface modifications by the introduction of new equivalent strains.
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PLASTICITY-Damage VERSUS Anisotropic Damage FOR IMPACT ON CONCRETE STRUCTURES
2008Co-Authors: Marion Chambart, Rodrigue Desmorat, Fabrice Gatuingt, Didier Combescure, Daniel GuilbaudAbstract:Impact problem on Reinforced Concrete structures are usually computed if the Finite Elements method is used with complex plasticity-Damage models. An alternative is to extend Anisotropic Damage model to high strain rates applications by introducing a visco or delay-Damage law. The advantages of such an approach are to represent the tensile strain rate effect encountered in concrete and to regularize the solution for a quite largerange of strain rates. Impact problems on reinforced concrete (RC) structures are usually computed with models coupling plasticity and isotropic Damage [1,2]. The induced Damage anisotropy observed for quasi-brittle materials such as concrete is often reproduced considering different variables for tension and compression (not consistent with the thermodynamic framework). Introducing viscosity for both Damage and plasticity evolutions enables to reproduce the strength enhancement due to rate effects. Such kinds of models present the main advantage to describe precisely each phenomenon locally observed (different rate effects in traction and compression, compaction under confined loadings ...) but require a large number of parameters. Anisotropic Damage is quite relevant to describe the micro-cracking pattern and the failure conditions of quasi-brittle materials and structures [3,4]. In concrete, a state of micro-cracks orthogonal to the loading direction in tension and parallel to it in compression is easily described by a second order Damage variable (Fig. 1). Based on Mazars and coworkers [5, 6] idea of a Damage rate governed by the positive extensions, an induced Anisotropic Damage model has been proposed [7]. As long as the confinement remains weak, this modelisation is an alternative to complex plasticity-Damage models to deal with impact problems. A visco-or delay-Damage is introduced in ttension to reproduce the strain rate effect experimentally observed and extend this model to high loading rates problems. Different viscosity laws are proposed, directly identified from dynamic tensile test to fit to the rate effect. This Anisotropic delay-Damage model introduces only few parameters (7 including elasticity parameters E and υ) compared to the ones mentioned higher. The efficiency of such an approach is illustrated with its application on impacted RC beams. The same computations are perfomed with a plasticity-Damage model [1] and the Anisotropic delay-Damage one and the results are compared. XXII ICTAM, 25-29 August 2008, Adelaide, Australia Figure 1: Crack pattern and Damage growth with the Anisotropic Damage model Figure 2 : Rate effect in tension for the Anisotropic delayDamage model
