The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Sergio Oller - One of the best experts on this subject based on the ideXlab platform.
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delamination in laminated plates using the 4 noded quadrilateral qlrz plate element based on the refined zigzag theory
Composite Structures, 2014Co-Authors: A Eijo, Eugenio Onate, Sergio OllerAbstract:Abstract A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displacement between consecutive layers in fracture mode II and III is the more important advantage of this element, denoted QLRZ [1] . A continuum Isotropic Damage model [2] is used to model the mechanical behavior of the plies. The material non-lineal problem is solved with the modified Newton–Raphson method. The RZT plate theory, the QLRZ finite element and the Isotropic Damage model are described in this work. Also, the implicit integration algorithm is presented. The performance of the numerical model is analyzed by studying the delamination in a rectangular plate for two different laminates, using the 3D analysis as the reference solution.
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a numerical model of delamination in composite laminated beams using the lrz beam element based on the refined zigzag theory
Composite Structures, 2013Co-Authors: A Eijo, Eugenio Onate, Sergio OllerAbstract:A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum Isotropic Damage model [2]. The modified Newton–Raphson method is used for solving the non-linear problem. The RZT theory, the LRZ finite element and the Isotropic Damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.
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Coupled plastic-Damaged model
Computer Methods in Applied Mechanics and Engineering, 1996Co-Authors: Bibiana Luccioni, Sergio Oller, Romano DanesiAbstract:A constitutive model that couples plasticity and Damage is presented. The model is thermodynamically consistent and comes from a generalization of classical plasticity theory and Isotropic Damage theory of Kachanov. Coupling between plasticity and Damage is achieved through a simultaneous solution of the plastic and the Damage problem. After a description of the model, a numerical algorithm for the integration of the resulting constitutive equations is presented. It is an Euler Backward type of algorithm that is particularly suitable to solve plain stress non-linear problems with a 2D finite element program. The consistent stiffness matrix is also derived. The paper is completed with some application examples that show that the model presented accurately reproduces the behaviour of elastic-plastic-Damaged materials.
Claudia Comi - One of the best experts on this subject based on the ideXlab platform.
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two phase Damage modeling of concrete affected by alkali silica reaction under variable temperature and humidity conditions
International Journal of Solids and Structures, 2012Co-Authors: Claudia Comi, Beatrice Kirchmayr, Rossella PignatelliAbstract:Abstract In the present work the concrete affected by alkali–silica reaction (ASR) is represented as a two-phase material made of a solid skeleton and a wet expanding gel, which exerts a pressure capable of severely damaging the concrete surrounding the reactive sites. Both the effects of temperature and humidity conditions on the kinetic of the chemical reaction and on the final value of the consequent expansion are included in the proposed model. The mechanical degradation induced by the ASR is described by a phenomenological Isotropic Damage model. The constitutive model, implemented in a finite element code, is used for the analyses of structures made of reactive concrete in the presence of temperature and moisture gradients. Firstly the temperature and humidity fields are obtained through uncoupled heat and moisture transport analyses and then the chemo-mechanical analysis is performed starting from the values of temperature and humidity preliminary calculated.
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a chemo thermo Damage model for the analysis of concrete dams affected by alkali silica reaction
Mechanics of Materials, 2009Co-Authors: Claudia Comi, Roberto Fedele, U PeregoAbstract:A chemo-thermo-Damage model is proposed to simulate the swelling and the deterioration of local stiffness and strength in concrete due to the alkali-aggregate reaction (AAR). Concrete affected by AAR is conceived as a two-phase heterogeneous material constituted by the expanding gel and by the homogenized concrete skeleton. The micro-cracking produced by the gel expansion is taken into account by means of an Isotropic Damage model based on the definition of two scalar Damage variables, one for stress states of prevailing tension and the other for compression. The developed model is validated on the basis of multiaxial accelerated laboratory tests performed on small specimens of reactive concrete, and documented in the recent literature. The model has been implemented in the finite-element code Abaqus and has been used to simulate the response of two concrete gravity dams subjected to service loading and to chemo-physical deterioration. The obtained results show that the developed model can be used to predict the Damage evolution within the dams and the consequent progressive reduction of their bearing capacity.
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fracture energy based bi dissipative Damage model for concrete
International Journal of Solids and Structures, 2001Co-Authors: Claudia Comi, U PeregoAbstract:An Isotropic Damage model for concrete is presented. The main features of the model are: limited number of constitutive parameters required; independent modelling of tension and compression behaviour by means of two Damage variables and two separate activation criteria (bi-dissipative model); independent definition of tension and compression fracture energies by means of constitutive parameters which do not affect the pre-peak behaviour; consistent modelling of the unilateral effect upon transition from tension to compression. To overcome the problem of mesh dependence in the softening regime, the effectiveness of a fracture energy based regularisation strategy is shown and the conditions for its correct application are defined. Comparisons of numerical simulations with experimental tests reveal the good accuracy and the robustness of the proposed model.
U Perego - One of the best experts on this subject based on the ideXlab platform.
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a chemo thermo Damage model for the analysis of concrete dams affected by alkali silica reaction
Mechanics of Materials, 2009Co-Authors: Claudia Comi, Roberto Fedele, U PeregoAbstract:A chemo-thermo-Damage model is proposed to simulate the swelling and the deterioration of local stiffness and strength in concrete due to the alkali-aggregate reaction (AAR). Concrete affected by AAR is conceived as a two-phase heterogeneous material constituted by the expanding gel and by the homogenized concrete skeleton. The micro-cracking produced by the gel expansion is taken into account by means of an Isotropic Damage model based on the definition of two scalar Damage variables, one for stress states of prevailing tension and the other for compression. The developed model is validated on the basis of multiaxial accelerated laboratory tests performed on small specimens of reactive concrete, and documented in the recent literature. The model has been implemented in the finite-element code Abaqus and has been used to simulate the response of two concrete gravity dams subjected to service loading and to chemo-physical deterioration. The obtained results show that the developed model can be used to predict the Damage evolution within the dams and the consequent progressive reduction of their bearing capacity.
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fracture energy based bi dissipative Damage model for concrete
International Journal of Solids and Structures, 2001Co-Authors: Claudia Comi, U PeregoAbstract:An Isotropic Damage model for concrete is presented. The main features of the model are: limited number of constitutive parameters required; independent modelling of tension and compression behaviour by means of two Damage variables and two separate activation criteria (bi-dissipative model); independent definition of tension and compression fracture energies by means of constitutive parameters which do not affect the pre-peak behaviour; consistent modelling of the unilateral effect upon transition from tension to compression. To overcome the problem of mesh dependence in the softening regime, the effectiveness of a fracture energy based regularisation strategy is shown and the conditions for its correct application are defined. Comparisons of numerical simulations with experimental tests reveal the good accuracy and the robustness of the proposed model.
A Eijo - One of the best experts on this subject based on the ideXlab platform.
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delamination in laminated plates using the 4 noded quadrilateral qlrz plate element based on the refined zigzag theory
Composite Structures, 2014Co-Authors: A Eijo, Eugenio Onate, Sergio OllerAbstract:Abstract A numerical method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated plate/shell structures is presented. The originality of this method is the use of 4-noded quadrilateral plate finite elements whit only seven variables per node to discretize the plate/shell geometry. The ability to capture the relative displacement between consecutive layers in fracture mode II and III is the more important advantage of this element, denoted QLRZ [1] . A continuum Isotropic Damage model [2] is used to model the mechanical behavior of the plies. The material non-lineal problem is solved with the modified Newton–Raphson method. The RZT plate theory, the QLRZ finite element and the Isotropic Damage model are described in this work. Also, the implicit integration algorithm is presented. The performance of the numerical model is analyzed by studying the delamination in a rectangular plate for two different laminates, using the 3D analysis as the reference solution.
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a numerical model of delamination in composite laminated beams using the lrz beam element based on the refined zigzag theory
Composite Structures, 2013Co-Authors: A Eijo, Eugenio Onate, Sergio OllerAbstract:A method based on the Refined Zigzag Theory (RZT) to model delamination in composite laminated beam structures is presented. The novelty of this method is the use of one-dimensional finite elements to discretize the geometry of the beam. The key property of this beam element, named LRZ [1], is the possibility to capture the relative displacement between consecutive layers which occurs during delamination. The fracture mode that the LRZ element is capable to predict is mode II. In order to capture the relative displacement using the LRZ element it is necessary to adapt the RZT theory as presented in this paper. The mechanical properties of the layers are modeled using a continuum Isotropic Damage model [2]. The modified Newton–Raphson method is used for solving the non-linear problem. The RZT theory, the LRZ finite element and the Isotropic Damage model are described in the paper. Also, the implicit integrations algorithm is presented. The performance of the LRZ element is analyzed by studying the delamination in a beam for two different laminates, using the plane stress solution as a reference.
K Y Yuan - One of the best experts on this subject based on the ideXlab platform.
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new strain energy based thermo elastoviscoplastic Isotropic Damage self healing model for bituminous composites part ii computational aspects
International Journal of Damage Mechanics, 2017Co-Authors: S Hong, K Y YuanAbstract:This paper is the second in a series implementing initial strain–energy-based thermo-elastoviscoplastic Isotropic Damage–self-healing formulations for bituminous composites to compare the model predictions with experimental measurements. Computational algorithms based on the two-step operator splitting methodology are systematically developed and employed for numerical simulations. The elastic Damage self-healing predictor and the viscoplastic corrector coupled with the Arrhenius-type temperature term via the net stress concept in conjunction with the hypothesis of strain equivalence are entirely considered as numerical implementation of the models. Several numerical examples of one-dimensional driver problems are first presented to show the effect of temperature and rest period for healing. Experimental validation of the proposed formulations against monotonic constant–strain test under different temperatures and controlled-strain cyclic tension test is presented. Qualitative and quantitative agreement b...
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new strain energy based thermo elastoviscoplastic Isotropic Damage self healing model for bituminous composites part i formulations
International Journal of Damage Mechanics, 2017Co-Authors: S Hong, K Y YuanAbstract:New initial strain energy-based thermo-elastoviscoplastic Isotropic Damage–self-healing formulations for bituminous materials are developed and implemented for numerical predictions of experimental...
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New Strain Energy-Based Coupled Elastoplastic Damage-Healing Formulations Accounting for Effect of Matric Suction during Earth-Moving Processes
Journal of Engineering Mechanics, 2013Co-Authors: K Y YuanAbstract:AbstractInnovative initial elastic strain energy–based coupled elastoplastic hybrid Isotropic Damage and healing models for partially saturated soils have been developed and implemented for numerical simulation of two-dimensional earth-pushing processes. A class of elastoplastic constitutive Damage-healing models, based on a continuum thermodynamic framework, is proposed within an initial elastic strain energy–based formulation. In particular, the change of effective stress caused by matric suction in the formulation is considered, and the governing incremental Damage and healing evolutions are coupled and characterized through the effective stress concept in conjunction with the hypothesis of strain equivalence. Further, plastic flow is introduced by means of an additive split of the stress tensor. In this innovative formulation, two characteristic energy norms of the tensile and compressive strain tensors, respectively, are introduced for the corresponding Damage and healing mechanisms. By incorporating...