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Eyad Masad - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic based model for coupling temperature dependent viscoelastic viscoplastic and viscodamage constitutive behavior of asphalt mixtures
International Journal for Numerical and Analytical Methods in Geomechanics, 2012Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Dallas N LittleAbstract:SUMMARY Based on the continuum damage mechanics, a general and comprehensive thermodynamic-based framework for coupling the temperature-dependent viscoelastic, viscoplastic, and viscodamage behaviors of bituminous materials is presented. This general framework derives systematically Schapery-type nonlinear viscoelasticity, Perzyna-type Viscoplasticity, and a viscodamage model analogous to the Perzyna-type Viscoplasticity. The resulting constitutive equations are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identifying the model parameters is discussed. Finally, the model is validated by comparing the model predictions with a comprehensive set of experimental data on hot mix asphalt that include creep-recovery, creep, uniaxial constant strain rate, and repeated creep-recovery tests in both tension and compression over a range of temperatures, stress levels, and strain rates. Comparisons between model predictions and experimental measurements show that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.
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a thermo viscoelastic viscoplastic viscodamage constitutive model for asphaltic materials
International Journal of Solids and Structures, 2011Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Chienwei Huang, Dallas N LittleAbstract:A temperature-dependent viscodamage model is proposed and coupled to the temperature-dependent Schapery’s nonlinear viscoelasticity and the temperature-dependent Perzyna’s Viscoplasticity constitutive model presented in Abu Al-Rub et al. (2009) and Huang et al. (in press) in order to model the nonlinear constitutive behavior of asphalt mixes. The thermo-viscodamage model is formulated to be a function of temperature, total effective strain, and the damage driving force which is expressed in terms of the stress invariants of the effective stress in the undamaged configuration. This expression for the damage force allows for the distinction between the influence of compression and extension loading conditions on damage nucleation and growth. A systematic procedure for obtaining the thermo-viscodamage model parameters using creep test data at different stress levels and different temperatures is presented. The recursive-iterative and radial return algorithms are used for the numerical implementation of the nonlinear viscoelasticity and Viscoplasticity models, respectively, whereas the viscodamage model is implemented using the effective (undamaged) configuration concept. Numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. The model is then calibrated and verified by comparing the model predictions with experimental data that include creep-recovery, creep, and uniaxial constant strain rate tests over a range of temperatures, stress levels, and strain rates. It is shown that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions.
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a micro damage healing model that improves prediction of fatigue life in asphalt mixes
International Journal of Engineering Science, 2010Co-Authors: Rashid Abu K Alrub, Eyad Masad, Masoud K Darabi, Dallas N LittleAbstract:Abstract The focus of the current paper is on the development and validation of a micro-damage healing model that improves the ability of an integrated nonlinear viscoelastic, viscoplastic, and viscodamage constitutive model based on continuum damage mechanics for predicting the fatigue life of asphalt paving mixtures. The model parameters of the continuum-based healing model are related to fundamental material properties. Recursive–iterative and radial return algorithms are used for the numerical implementation of viscoelasticity and Viscoplasticity models respectively, whereas the viscodamage and micro-damage healing models are implemented using the concept of the effective undamaged-healed natural configuration. Numerical algorithms are implemented into the well-known finite element code Abaqus via the user material subroutine UMAT. Finally, the model is validated by comparing its predictions with experimental data on an asphalt mix that include repeated creep-recovery tests for different loading times and rest periods in both tension and compression. The significant enhancement of the ability of the constitutive model to predict fatigue life due to inclusion of the micro-damage healing is clearly demonstrated.
Masoud K Darabi - One of the best experts on this subject based on the ideXlab platform.
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a thermodynamic framework for constitutive modeling of time and rate dependent materials part i theory
International Journal of Plasticity, 2012Co-Authors: Rashid Abu K Alrub, Masoud K DarabiAbstract:A general thermodynamic-based framework for deriving coupled temperature-dependent viscoelasticity, Viscoplasticity, viscodamage, and micro-damage healing constitutive models for constitutive modeling of time- and rate-dependent materials is presented. Principle of virtual power, Clausius–Duhem inequality, and the principle of maximum rate of dissipation are used to construct this general thermodynamic framework. A micro-damage healing natural configuration is introduced to enhance the continuum damage mechanics theories in modeling the healing phenomenon. This healing configuration can be considered as the extension of the well-known Kachanov’s effective (undamaged) configuration (Kachanov, 1958). The Viscoplasticity loading condition is defined from the microforce balance derived directly from the principle of virtual power. Moreover, for the first time, viscoelasticity, viscodamage, and micro-damage healing microforce balances are derived directly from the principle of virtual power. It is also shown that the generalized non-associative plasticity/Viscoplasticity theories can be a direct consequence of postulating the principle of virtual power. The emphasis in this paper is placed on the decomposition of thermodynamic conjugate forces into energetic and dissipative components. It is shown that this decomposition is necessary for accurate estimation of the rate of energy dissipation. The energetic components are related to the Helmholtz free energy, whereas the dissipative components are related to the rate of energy dissipation. This thermodynamic framework is used for deriving more comprehensive viscoelastic, viscoplastic, and viscodamage, and micro-damage healing constitutive models.
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thermodynamic based model for coupling temperature dependent viscoelastic viscoplastic and viscodamage constitutive behavior of asphalt mixtures
International Journal for Numerical and Analytical Methods in Geomechanics, 2012Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Dallas N LittleAbstract:SUMMARY Based on the continuum damage mechanics, a general and comprehensive thermodynamic-based framework for coupling the temperature-dependent viscoelastic, viscoplastic, and viscodamage behaviors of bituminous materials is presented. This general framework derives systematically Schapery-type nonlinear viscoelasticity, Perzyna-type Viscoplasticity, and a viscodamage model analogous to the Perzyna-type Viscoplasticity. The resulting constitutive equations are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identifying the model parameters is discussed. Finally, the model is validated by comparing the model predictions with a comprehensive set of experimental data on hot mix asphalt that include creep-recovery, creep, uniaxial constant strain rate, and repeated creep-recovery tests in both tension and compression over a range of temperatures, stress levels, and strain rates. Comparisons between model predictions and experimental measurements show that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.
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a thermo viscoelastic viscoplastic viscodamage constitutive model for asphaltic materials
International Journal of Solids and Structures, 2011Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Chienwei Huang, Dallas N LittleAbstract:A temperature-dependent viscodamage model is proposed and coupled to the temperature-dependent Schapery’s nonlinear viscoelasticity and the temperature-dependent Perzyna’s Viscoplasticity constitutive model presented in Abu Al-Rub et al. (2009) and Huang et al. (in press) in order to model the nonlinear constitutive behavior of asphalt mixes. The thermo-viscodamage model is formulated to be a function of temperature, total effective strain, and the damage driving force which is expressed in terms of the stress invariants of the effective stress in the undamaged configuration. This expression for the damage force allows for the distinction between the influence of compression and extension loading conditions on damage nucleation and growth. A systematic procedure for obtaining the thermo-viscodamage model parameters using creep test data at different stress levels and different temperatures is presented. The recursive-iterative and radial return algorithms are used for the numerical implementation of the nonlinear viscoelasticity and Viscoplasticity models, respectively, whereas the viscodamage model is implemented using the effective (undamaged) configuration concept. Numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. The model is then calibrated and verified by comparing the model predictions with experimental data that include creep-recovery, creep, and uniaxial constant strain rate tests over a range of temperatures, stress levels, and strain rates. It is shown that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions.
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a micro damage healing model that improves prediction of fatigue life in asphalt mixes
International Journal of Engineering Science, 2010Co-Authors: Rashid Abu K Alrub, Eyad Masad, Masoud K Darabi, Dallas N LittleAbstract:Abstract The focus of the current paper is on the development and validation of a micro-damage healing model that improves the ability of an integrated nonlinear viscoelastic, viscoplastic, and viscodamage constitutive model based on continuum damage mechanics for predicting the fatigue life of asphalt paving mixtures. The model parameters of the continuum-based healing model are related to fundamental material properties. Recursive–iterative and radial return algorithms are used for the numerical implementation of viscoelasticity and Viscoplasticity models respectively, whereas the viscodamage and micro-damage healing models are implemented using the concept of the effective undamaged-healed natural configuration. Numerical algorithms are implemented into the well-known finite element code Abaqus via the user material subroutine UMAT. Finally, the model is validated by comparing its predictions with experimental data on an asphalt mix that include repeated creep-recovery tests for different loading times and rest periods in both tension and compression. The significant enhancement of the ability of the constitutive model to predict fatigue life due to inclusion of the micro-damage healing is clearly demonstrated.
Rashid Abu K Alrub - One of the best experts on this subject based on the ideXlab platform.
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a thermodynamic framework for constitutive modeling of time and rate dependent materials part i theory
International Journal of Plasticity, 2012Co-Authors: Rashid Abu K Alrub, Masoud K DarabiAbstract:A general thermodynamic-based framework for deriving coupled temperature-dependent viscoelasticity, Viscoplasticity, viscodamage, and micro-damage healing constitutive models for constitutive modeling of time- and rate-dependent materials is presented. Principle of virtual power, Clausius–Duhem inequality, and the principle of maximum rate of dissipation are used to construct this general thermodynamic framework. A micro-damage healing natural configuration is introduced to enhance the continuum damage mechanics theories in modeling the healing phenomenon. This healing configuration can be considered as the extension of the well-known Kachanov’s effective (undamaged) configuration (Kachanov, 1958). The Viscoplasticity loading condition is defined from the microforce balance derived directly from the principle of virtual power. Moreover, for the first time, viscoelasticity, viscodamage, and micro-damage healing microforce balances are derived directly from the principle of virtual power. It is also shown that the generalized non-associative plasticity/Viscoplasticity theories can be a direct consequence of postulating the principle of virtual power. The emphasis in this paper is placed on the decomposition of thermodynamic conjugate forces into energetic and dissipative components. It is shown that this decomposition is necessary for accurate estimation of the rate of energy dissipation. The energetic components are related to the Helmholtz free energy, whereas the dissipative components are related to the rate of energy dissipation. This thermodynamic framework is used for deriving more comprehensive viscoelastic, viscoplastic, and viscodamage, and micro-damage healing constitutive models.
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thermodynamic based model for coupling temperature dependent viscoelastic viscoplastic and viscodamage constitutive behavior of asphalt mixtures
International Journal for Numerical and Analytical Methods in Geomechanics, 2012Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Dallas N LittleAbstract:SUMMARY Based on the continuum damage mechanics, a general and comprehensive thermodynamic-based framework for coupling the temperature-dependent viscoelastic, viscoplastic, and viscodamage behaviors of bituminous materials is presented. This general framework derives systematically Schapery-type nonlinear viscoelasticity, Perzyna-type Viscoplasticity, and a viscodamage model analogous to the Perzyna-type Viscoplasticity. The resulting constitutive equations are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identifying the model parameters is discussed. Finally, the model is validated by comparing the model predictions with a comprehensive set of experimental data on hot mix asphalt that include creep-recovery, creep, uniaxial constant strain rate, and repeated creep-recovery tests in both tension and compression over a range of temperatures, stress levels, and strain rates. Comparisons between model predictions and experimental measurements show that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.
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a thermo viscoelastic viscoplastic viscodamage constitutive model for asphaltic materials
International Journal of Solids and Structures, 2011Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Chienwei Huang, Dallas N LittleAbstract:A temperature-dependent viscodamage model is proposed and coupled to the temperature-dependent Schapery’s nonlinear viscoelasticity and the temperature-dependent Perzyna’s Viscoplasticity constitutive model presented in Abu Al-Rub et al. (2009) and Huang et al. (in press) in order to model the nonlinear constitutive behavior of asphalt mixes. The thermo-viscodamage model is formulated to be a function of temperature, total effective strain, and the damage driving force which is expressed in terms of the stress invariants of the effective stress in the undamaged configuration. This expression for the damage force allows for the distinction between the influence of compression and extension loading conditions on damage nucleation and growth. A systematic procedure for obtaining the thermo-viscodamage model parameters using creep test data at different stress levels and different temperatures is presented. The recursive-iterative and radial return algorithms are used for the numerical implementation of the nonlinear viscoelasticity and Viscoplasticity models, respectively, whereas the viscodamage model is implemented using the effective (undamaged) configuration concept. Numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. The model is then calibrated and verified by comparing the model predictions with experimental data that include creep-recovery, creep, and uniaxial constant strain rate tests over a range of temperatures, stress levels, and strain rates. It is shown that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions.
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a micro damage healing model that improves prediction of fatigue life in asphalt mixes
International Journal of Engineering Science, 2010Co-Authors: Rashid Abu K Alrub, Eyad Masad, Masoud K Darabi, Dallas N LittleAbstract:Abstract The focus of the current paper is on the development and validation of a micro-damage healing model that improves the ability of an integrated nonlinear viscoelastic, viscoplastic, and viscodamage constitutive model based on continuum damage mechanics for predicting the fatigue life of asphalt paving mixtures. The model parameters of the continuum-based healing model are related to fundamental material properties. Recursive–iterative and radial return algorithms are used for the numerical implementation of viscoelasticity and Viscoplasticity models respectively, whereas the viscodamage and micro-damage healing models are implemented using the concept of the effective undamaged-healed natural configuration. Numerical algorithms are implemented into the well-known finite element code Abaqus via the user material subroutine UMAT. Finally, the model is validated by comparing its predictions with experimental data on an asphalt mix that include repeated creep-recovery tests for different loading times and rest periods in both tension and compression. The significant enhancement of the ability of the constitutive model to predict fatigue life due to inclusion of the micro-damage healing is clearly demonstrated.
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nonlocal constitutive model for impact damage in metals
2004Co-Authors: George Z Voyiadjis, Rashid Abu K Alrub, Anthony N PalazottoAbstract:Summary As soon as material failure dominates a deformation process, the material increasingly displays strain softening and the finite element computation is mesh dependent with non-physical description in the localized regions. Gradient-enhanced constitutive equations with length scale measures are presented to alleviate these inconsistencies. Numerical simulations are performed to study the effect of including length scale parameters on the dynamic localization of plastic flow in shear bands for impact-damage related problems. INTRODUCTION The motivation for this study stems out from the experimental tests of specimens made of ductile and heterogeneous materials loaded at low- and high-speed impacts. In many of these tests the intensive nonlinearity induced in the material is attributed to the Viscoplasticity and viscodamage morphologies. These experiments indicate that the failure mechanisms occur at localized zones of Viscoplasticity and viscodamage where numerous interactions of defects take place. Finite element codes that implement classical plasticity and damage theories also indicate that in problems involving shear localization the simulations are sensitive to the mesh size and alignment [1]. Although it has been shown that the Viscoplasticity theory regularizes the solution by introducing implicitly length-scale through the viscous parameter, the numerical results still show mesh dependence for large deformations. In order to be able to capture such localized deformation zones using computational models, we aim here to introduce explicit and implicit length-scale measures in plasticity and damage governing equations through the use of the gradient-dependent theory and Viscoplasticity theory coupled to the rate-dependent damage theory.
Dallas N Little - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic based model for coupling temperature dependent viscoelastic viscoplastic and viscodamage constitutive behavior of asphalt mixtures
International Journal for Numerical and Analytical Methods in Geomechanics, 2012Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Dallas N LittleAbstract:SUMMARY Based on the continuum damage mechanics, a general and comprehensive thermodynamic-based framework for coupling the temperature-dependent viscoelastic, viscoplastic, and viscodamage behaviors of bituminous materials is presented. This general framework derives systematically Schapery-type nonlinear viscoelasticity, Perzyna-type Viscoplasticity, and a viscodamage model analogous to the Perzyna-type Viscoplasticity. The resulting constitutive equations are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identifying the model parameters is discussed. Finally, the model is validated by comparing the model predictions with a comprehensive set of experimental data on hot mix asphalt that include creep-recovery, creep, uniaxial constant strain rate, and repeated creep-recovery tests in both tension and compression over a range of temperatures, stress levels, and strain rates. Comparisons between model predictions and experimental measurements show that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.
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a thermo viscoelastic viscoplastic viscodamage constitutive model for asphaltic materials
International Journal of Solids and Structures, 2011Co-Authors: Masoud K Darabi, Eyad Masad, Rashid Abu K Alrub, Chienwei Huang, Dallas N LittleAbstract:A temperature-dependent viscodamage model is proposed and coupled to the temperature-dependent Schapery’s nonlinear viscoelasticity and the temperature-dependent Perzyna’s Viscoplasticity constitutive model presented in Abu Al-Rub et al. (2009) and Huang et al. (in press) in order to model the nonlinear constitutive behavior of asphalt mixes. The thermo-viscodamage model is formulated to be a function of temperature, total effective strain, and the damage driving force which is expressed in terms of the stress invariants of the effective stress in the undamaged configuration. This expression for the damage force allows for the distinction between the influence of compression and extension loading conditions on damage nucleation and growth. A systematic procedure for obtaining the thermo-viscodamage model parameters using creep test data at different stress levels and different temperatures is presented. The recursive-iterative and radial return algorithms are used for the numerical implementation of the nonlinear viscoelasticity and Viscoplasticity models, respectively, whereas the viscodamage model is implemented using the effective (undamaged) configuration concept. Numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. The model is then calibrated and verified by comparing the model predictions with experimental data that include creep-recovery, creep, and uniaxial constant strain rate tests over a range of temperatures, stress levels, and strain rates. It is shown that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions.
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a micro damage healing model that improves prediction of fatigue life in asphalt mixes
International Journal of Engineering Science, 2010Co-Authors: Rashid Abu K Alrub, Eyad Masad, Masoud K Darabi, Dallas N LittleAbstract:Abstract The focus of the current paper is on the development and validation of a micro-damage healing model that improves the ability of an integrated nonlinear viscoelastic, viscoplastic, and viscodamage constitutive model based on continuum damage mechanics for predicting the fatigue life of asphalt paving mixtures. The model parameters of the continuum-based healing model are related to fundamental material properties. Recursive–iterative and radial return algorithms are used for the numerical implementation of viscoelasticity and Viscoplasticity models respectively, whereas the viscodamage and micro-damage healing models are implemented using the concept of the effective undamaged-healed natural configuration. Numerical algorithms are implemented into the well-known finite element code Abaqus via the user material subroutine UMAT. Finally, the model is validated by comparing its predictions with experimental data on an asphalt mix that include repeated creep-recovery tests for different loading times and rest periods in both tension and compression. The significant enhancement of the ability of the constitutive model to predict fatigue life due to inclusion of the micro-damage healing is clearly demonstrated.
Abdelkader Hachemi - One of the best experts on this subject based on the ideXlab platform.
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non linear material modeling of fiber reinforced polymers based on coupled viscoelasticity Viscoplasticity with anisotropic continuous damage mechanics
Composite Structures, 2015Co-Authors: Dmytro Vasiukov, Stephane Panier, Abdelkader HachemiAbstract:Abstract A meso-scale material modeling of the fiber-reinforced polymer composites is presented. This model is based on coupled anisotropic viscoelasticity–Viscoplasticity with anisotropic continuous damage mechanics. The constitutive equations are derived for three-dimensional statement and integrated implicitly by using return-mapping algorithm. Viscoelasticity model implies time dependent material properties. Viscoplasticity model is based on modified Hoffman criterion with combination of the Perzyna model. Anisotropic damage model is based on extended three-dimensional damage model. Developed material model is implemented in ABAQUS/Standard and is applied for modeling glass and carbon fiber laminate composite plates with various stacking sequences. Obtained results are in high agreement with already published experimental data.
