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Qing Chen - One of the best experts on this subject based on the ideXlab platform.
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legendre polynomial based stochastic Micromechanical Model for the unsaturated concrete repaired by edm
Archive of Applied Mechanics, 2020Co-Authors: Qing Chen, J. W. Ju, Haoxin LiAbstract:A Legendre polynomial-based stochastic Micromechanical framework is proposed to quantify the unbiased probabilistic behavior for the unsaturated concrete repaired by the electrochemical deposition method (EDM). By following the authors’ previous works, a deterministic Micromechanical Model with new multilevel homogenization scheme for the repaired unsaturated concrete is presented based on the material’s microstructures. With the stochastic descriptions for the microstructures of the repaired unsaturated concrete, the deterministic framework is extended to stochastic. The unbiased probabilistic behavior of the repaired concrete is reached by incorporating the Legendre polynomial approximations and the Monte Carlo simulations. The predictions herein are then compared with the available experimental data, existing Models and the commonly used probability density functions, which indicate that the presented stochastic Micromechanical framework is capable of characterizing the EDM healing process for unsaturated concrete considering the material’s random microstructure. Finally, the statistical effects of the deposition products and unsaturated pores are discussed.
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a multi level Micromechanical Model for elastic properties of hybrid fiber reinforced concrete
Construction and Building Materials, 2017Co-Authors: Yao Zhang, Woody J Ju, Qing ChenAbstract:Abstract There is a demand for multi scale Micromechanical Models to disclose and analyze the effects of microstructure on macro mechanical properties of hybrid fiber reinforced concrete (HFRC). This study involved presenting a multi-level Micromechanical Model that involves cement paste level, concrete level, and hybrid fiber reinforced concrete level to quantitatively predict the effective isotropic and elastic properties of HFRC under ambient temperature. For the purposes of homogenization, the volume fractions of different phases at different levels are determined by means of a modified Power’s Model. In the multi-level Micromechanical Model, hydration products of clinker, sand, coarse aggregate, and hybrid fiber are comprehensively considered. A homogenization stepping framework is presented to realize upscaling from microstructural properties to the effective elastic properties of a macrostructure for HFRC. Additionally, several substepping homogenizations are also presented to estimate the effective elastic properties of an equivalent medium with respect to the cement paste and hybrid fiber reinforced concrete. Comparisons with experimental data from extant studies are implemented level by level. Subsequently, the influences of aggregate, sand, fiber type, and hydration degree on the properties of HFRC are discussed based on a proposed multi-level Micromechanical Model. Finally, the mixture ratio of steel fiber and w/c are investigated with respect to the HFRC design to obtain anticipated elastic properties.
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a multiphase Micromechanical Model for hybrid fiber reinforced concrete considering the aggregate and itz effects
Construction and Building Materials, 2016Co-Authors: Qing Chen, Woody J Ju, Zhengwu Jiang, Yaqiong WangAbstract:Abstract Very few Micromechanical Models are available for hybrid fiber reinforced concrete (HFRC), although it has been widely applied in many structures. To quantitatively predict the effective properties of HFRC with the aggregate and interfacial transition zone (ITZ) effects, a multi-phase Micromechanical framework is proposed based on the material’s microstructures. In the proposed Model, the multi-types of fibers, aggregate, cement paste and ITZ are comprehensively considered. The volume fraction of the ITZ is analytically calculated based on the aggregate grading. Multi-level homogenization schemes are presented to predict the effective properties of HFRC. By utilizing the generalized self-consistent approach, the equivalent matrix composed by the aggregate, cement and the ITZ between them are obtained with the first and second level homogenization procedures. Through adding different types of fibers step by step into the equivalent matrix, the properties of HFRC are reached with the modifications to the Halpin-Tsai Model. To demonstrate the feasibility of the proposed Micromechanical framework, the predictions herein are compared with the experimental data, the Voigt upper bound and the Reuss lower bound. Finally, the influences of aggregate, ITZ, multi-types of fibers on the properties of HFRC are discussed based on the proposed Micromechanical Model.
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a stochastic Micromechanical Model for multiphase composites containing spherical inhomogeneities
Acta Mechanica, 2015Co-Authors: Qing Chen, J. W. Ju, L B Wang, T Deng, Shunhua ZhouAbstract:A stochastic Micromechanical framework for multiphase composites is proposed to characterize the probabilistic behaviors of effective properties of composite materials. Based on our previous work, the deterministic Micromechanical Model of the multiphase composites is derived by introducing the strain concentration tensors. By Modeling the volume fractions and properties of constituents as stochastic, we extend the deterministic framework to stochastic to incorporate the inherent randomness of effective properties among different specimens. A new simulation framework, consisting of univariate approximation for multivariate function, Newton interpolations, and Monte Carlo simulation, is developed to quantitatively evaluate the stochastic characteristics of the effective properties of composites. Numerical examples including limited experimental validations, comparisons with existing Micromechanical Models, and the Monte Carlo simulations indicate that the proposed Models provide an accurate and computationally efficient framework in characterizing the effective properties of multiphase composites. Finally, the effects of the correlation between the constituents’ material parameters are discussed based on our proposed stochastic Micromechanical Model, which shows that the negative correlation between Young’s modulus and Poisson’s ratio of the constituents can enhance the effective properties of the composites.
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maximum entropy based stochastic Micromechanical Model for a two phase composite considering the inter particle interaction effect
Acta Mechanica, 2015Co-Authors: J. W. Ju, Qing Chen, Shunhua Zhou, Zhengwu Jiang, Yaqiong Wang, B WuAbstract:A maximum entropy-based stochastic Micromechanical framework considering the inter-particle interaction effect is proposed to characterize the probabilistic behavior of the effective properties of two-phase composite materials. Based on our previous work, the deterministic Micromechanical Model of the two-phase composites is derived by introducing the strain concentration tensors considering the inter-particle interaction effect. By Modeling the volume fractions and properties of constituents as stochastic, we extend the deterministic framework to stochastics, to incorporate the inherent randomness of effective properties among different specimens. A distribution-free method is employed to get the unbiased probability density function based on the maximum entropy principle. Further, the normalization procedures are utilized to make the probability density functions more stable. Numerical examples including limited experimental validations, comparisons with existing Micromechanical Models, commonly used probability density functions and the direct Monte Carlo simulations indicate that the proposed Models provide an accurate and computationally efficient framework in characterizing the effective properties of two-phase composites.
Woody J Ju - One of the best experts on this subject based on the ideXlab platform.
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a multi level Micromechanical Model for elastic properties of hybrid fiber reinforced concrete
Construction and Building Materials, 2017Co-Authors: Yao Zhang, Woody J Ju, Qing ChenAbstract:Abstract There is a demand for multi scale Micromechanical Models to disclose and analyze the effects of microstructure on macro mechanical properties of hybrid fiber reinforced concrete (HFRC). This study involved presenting a multi-level Micromechanical Model that involves cement paste level, concrete level, and hybrid fiber reinforced concrete level to quantitatively predict the effective isotropic and elastic properties of HFRC under ambient temperature. For the purposes of homogenization, the volume fractions of different phases at different levels are determined by means of a modified Power’s Model. In the multi-level Micromechanical Model, hydration products of clinker, sand, coarse aggregate, and hybrid fiber are comprehensively considered. A homogenization stepping framework is presented to realize upscaling from microstructural properties to the effective elastic properties of a macrostructure for HFRC. Additionally, several substepping homogenizations are also presented to estimate the effective elastic properties of an equivalent medium with respect to the cement paste and hybrid fiber reinforced concrete. Comparisons with experimental data from extant studies are implemented level by level. Subsequently, the influences of aggregate, sand, fiber type, and hydration degree on the properties of HFRC are discussed based on a proposed multi-level Micromechanical Model. Finally, the mixture ratio of steel fiber and w/c are investigated with respect to the HFRC design to obtain anticipated elastic properties.
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a multiphase Micromechanical Model for hybrid fiber reinforced concrete considering the aggregate and itz effects
Construction and Building Materials, 2016Co-Authors: Qing Chen, Woody J Ju, Zhengwu Jiang, Yaqiong WangAbstract:Abstract Very few Micromechanical Models are available for hybrid fiber reinforced concrete (HFRC), although it has been widely applied in many structures. To quantitatively predict the effective properties of HFRC with the aggregate and interfacial transition zone (ITZ) effects, a multi-phase Micromechanical framework is proposed based on the material’s microstructures. In the proposed Model, the multi-types of fibers, aggregate, cement paste and ITZ are comprehensively considered. The volume fraction of the ITZ is analytically calculated based on the aggregate grading. Multi-level homogenization schemes are presented to predict the effective properties of HFRC. By utilizing the generalized self-consistent approach, the equivalent matrix composed by the aggregate, cement and the ITZ between them are obtained with the first and second level homogenization procedures. Through adding different types of fibers step by step into the equivalent matrix, the properties of HFRC are reached with the modifications to the Halpin-Tsai Model. To demonstrate the feasibility of the proposed Micromechanical framework, the predictions herein are compared with the experimental data, the Voigt upper bound and the Reuss lower bound. Finally, the influences of aggregate, ITZ, multi-types of fibers on the properties of HFRC are discussed based on the proposed Micromechanical Model.
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a multi phase Micromechanical Model for unsaturated concrete repaired using the electrochemical deposition method
International Journal of Solids and Structures, 2013Co-Authors: Qing Chen, Woody J Ju, Shuai Zhou, Zhengwu JiangAbstract:Abstract Most concrete structures repaired using the electrochemical deposition method (EDM) are not fully saturated in reality. To theoretically illustrate the deposition healing process by micromechanics and quantitatively describe the effective properties of unsaturated concrete during the EDM healing process, a multi-phase multi-level Micromechanical framework is proposed based on the microstructure of unsaturated concrete and the EDM’s healing mechanism. In the proposed Model, the volume fractions of water and deposition products, the water effect (including further hydration and viscosity in pores) and the shapes of pores in the concrete are comprehensively considered. Moreover, multi-level homogenization procedures are employed to predict the effective properties of unsaturated concrete repaired using the EDM. For the first-level homogenization of this Model, a modified function is presented to correct the Mori–Tanaka (M–T) method, which is used to predict the effective properties of equivalent inclusions composed of deposition products and water. To demonstrate the feasibility of the proposed Micromechanical Model, predictions obtained via the proposed multi-phase Micromechanical Model are compared with the experimental data, including results from extreme states during the EDM healing process. Finally, the influences of equivalent aspect ratios and deposition product properties on the healing effectiveness of EDM are discussed based on the proposed Micromechanical Model.
Baoshan Huang - One of the best experts on this subject based on the ideXlab platform.
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predicting concrete coefficient of thermal expansion with an improved Micromechanical Model
Construction and Building Materials, 2014Co-Authors: Changjun Zhou, Baoshan HuangAbstract:Abstract The coefficient of thermal expansion (CTE) is a very important property of cement concrete. Concrete CTE represents the thermal expansion and/or contraction sensitivity of concrete, which highly relates to thermal cracks in concrete infrastructures, such as concrete dams and concrete pavements. The values of concrete CTE can be measured through laboratory testing or predicted using empirical Models. While laboratory testing is time- and labor-consuming, the current concrete CTE prediction Models are mainly based on empirical relationships. In this study, an improved Micromechanical Model was proposed to predict concrete CTE based on thermal mechanical analysis in which concrete was seen as a composite material. The original Model developed by the authors can be found elsewhere. The improved CTE Model was validated using a hierarchical approach with CTE measurements of cement paste, mortar, and concrete. The result indicates that the improved Model was able to provide a better prediction on CTE values than the original Model. Factors affecting concrete CTE were investigated utilizing the developed CTE prediction Model. It was found that aggregate type was a major factor affecting concrete CTE, whereas water cement ratio did not have a significant effect on concrete CTE.
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Micromechanical Model for predicting coefficient of thermal expansion of concrete
Journal of Materials in Civil Engineering, 2013Co-Authors: Changjun Zhou, Baoshan HuangAbstract:AbstractThermal cracking of Portland cement concrete (PCC) decreases rideability and accelerates deterioration of concrete pavements. Coefficient of thermal expansion (CTE) is one of the most important parameters to evaluate the thermal sensitivity of PCC. The AASHTO mechanistic-empirical pavement design guide (MEPDG) requires CTE as a basic input for concrete pavement design, which has increased interest in studies related to concrete CTE in the United States. Several test methods have been developed and used to determine concrete CTE. Nevertheless, concrete CTE testing is time-consuming. Most of the currently available concrete CTE prediction Models are empirical and do not reflect the microstructure of PCC. This paper developed a Micromechanical Model based on thermal mechanical analysis to predict concrete CTE. Concrete CTE data found in the literature validated the applicability of the developed Model. Factors affecting concrete CTE were examined using the proposed Model. The Model has the potential ...
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dynamic modulus prediction of hma mixtures based on the viscoelastic Micromechanical Model
Journal of Materials in Civil Engineering, 2008Co-Authors: Baoshan HuangAbstract:Dynamic modulus (|E*|) of hot-mix asphalt (HMA) mixtures is one of the fundamental engineering properties measured by the simple performance tester and has also been incorporated as a basic input into the American Association of State Highway and Transportation Officials Mechanistic-Empirical Design Guide for flexible pavements. Although direct laboratory testing and empirical equations (such as the Witczak Model and the Hirsch Model) provide two ways to obtain the values of dynamic modulus of HMA mixtures, a predictive Model based on the microstructure of HMA mixtures is more desirable. This paper presents a viscoelastic Micromechanical Model to predict the dynamic modulus of HMA mixtures based on the elastic-viscoelastic correspondence principle. In this Model, HMA mixtures are treated as a composite by embedding the mastic (or asphalt binder)-coated aggregate particles into the equivalent medium of HMA mixtures. Using the proposed Model, a solution was obtained to predict the elastic modulus of HMA mixtures. Based on the elastic-viscoelastic correspondence principle, a viscoelastic equation was derived to predict the complex modulus and subsequently the dynamic modulus of HMA mixtures. The developed equations had the capability of taking into account both aggregate gradation and air void size distribution. Laboratory experiments were conducted to verify the developed Model. The dynamic modulus values of mastics and HMA mixtures were obtained through direct laboratory testing. The dynamic modulus of mastic was then used to predict the dynamic modulus of laboratory-prepared HMA mixtures with the newly developed Model. Laboratory test results showed that a discrepancy exists between the calculated and measured dynamic moduli. The reason for the discrepancy between measured and predicted dynamic moduli and the factors affecting the dynamic modulus were also explored in the paper.
Anastasia Muliana - One of the best experts on this subject based on the ideXlab platform.
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a Micromechanical Model for predicting thermal properties and thermo viscoelastic responses of functionally graded materials
International Journal of Solids and Structures, 2009Co-Authors: Anastasia MulianaAbstract:Abstract This study introduces a Micromechanical Model for predicting effective thermo-viscoelastic behaviors of a functionally graded material (FGM). The studied FGM consists of two constituents with varying compositions through the thickness. The microstructure of the FGM is idealized as solid spherical particles spatially distributed in a homogeneous matrix. The mechanical properties of each constituent can vary with temperature and time, while the thermal properties are allowed to change with temperature. The FGM Model includes a transition zone where the inclusion and matrix constituents are not well defined. At the transition zone, an interchange between the two constituents as inclusion and matrix takes place such that the maximum inclusion volume contents before and after the transition zone are less than 50%. A Micromechanical Model is used to determine through-thickness effective thermal conductivity, coefficient of thermal expansion, and time-dependent compliance/stiffness of the FGM. The material properties at the transition zone are assumed to vary linearly between the two properties at the bounds of the transition zone. The Micromechanical Model is designed to be compatible with finite element (FE) scheme and used to analyze heat conduction and thermo-viscoelastic responses of FGMs. Available experimental data and analytical solutions in the literature are used to verify the thermo-mechanical properties of FGMs. The effects of time and temperature dependent constituent properties on the overall temperature, stress, and displacement fields in the FGM are also examined.
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a concurrent Micromechanical Model for predicting nonlinear viscoelastic responses of composites reinforced with solid spherical particles
International Journal of Solids and Structures, 2007Co-Authors: Anastasia MulianaAbstract:Abstract A concurrent Micromechanical Model for predicting nonlinear viscoelastic responses of particle reinforced polymers is developed. Particles are in the form of solid spheres having micro-scale diameters. The composite microstructures are idealized by periodically distributed cubic particles in a matrix medium. Each particle is assumed to be fully surrounded by polymeric matrix such that contact between particles can be avoided. A representative volume element (RVE) is then defined by a single particle embedded in the cubic matrix. A spatial periodicity boundary condition is imposed to the RVE. One eighth unit-cell Model with four particle and polymer subcells is generated due to the three-plane symmetry of the RVE. The solid spherical particle is Modeled as a linear elastic material. The polymeric matrix follows nonlinear viscoelastic behaviors of thermorheologically simple materials. The homogenized Micromechanical relation is developed in terms of the average strains and stresses in the subcells and traction continuity and displacement compatibility at the subcells’ interfaces are imposed. A stress–strain correction scheme is also formulated to satisfy the linearized Micromechanical and the nonlinear constitutive relations. The Micromechanical Model provides three-dimensional (3D) effective properties of homogeneous composite responses, while recognizing microstructural geometries and in situ material properties of the heterogeneous medium. The Micromechanical formulation is designed to be compatible with general displacement based finite element (FE) analyses. Experimental data and analytical Micromechanical Models available in the literature are used to verify the capability of the above Micromechanical Model for predicting the overall composite behaviors. The proposed microModel is also examined in terms of computational efficiency and accuracy.
Klaus Hackl - One of the best experts on this subject based on the ideXlab platform.
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a Micromechanical Model for martensitic phase transformations in shape memory alloys based on energy relaxation
Zamm-zeitschrift Fur Angewandte Mathematik Und Mechanik, 2009Co-Authors: Thorsten Bartel, Klaus HacklAbstract:We develop a Micromechanical Model for single-crystalline materials undergoing diffusionless solid-to-solid phase transitions. It is based on the specification of laminated microstructures on the materials' microscale and hence is designed to approximate the rank-1-convex hull of the underlying energy-density for the phase-mixture. In order to capture the hysteretic behavior of such materials like shape-memory-alloys we also account for dissipation by means of evolution equations for the inelastic internal variables. In this context, we derive different evolution-laws from inelastic potentials via least-action principles. Several material-point computations emphasize the characteristics of the presented Model.
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a Micromechanical Model for pretextured polycrystalline shape memory alloys including elastic anisotropy
Continuum Mechanics and Thermodynamics, 2008Co-Authors: Klaus Hackl, R HeinenAbstract:We present a Micromechanical Model for polycrystalline shape-memory alloys which is capable of reproducing important aspects of the material behavior such as pseudoelasticity, pseudoplasticity, tension–compression asymmetry and the influence of texture inhomogeneities which may occur from the production process of components or specimens. Our Model is based on the optimization of the material’s free energy density and uses a dissipation ansatz which is homogeneous of first order. Considering the full anisotropic material properties of both the austenite and the martensite phase, we compute the evolution of the orientation distributions of austenite and martensite as internal variables of our Model.
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a Micromechanical Model for polycrystalline shape memory alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Klaus Hackl, Martin Schmidtbaldassari, W ZhangAbstract:We develop an energy-based Model for polycrystalline shape-memory alloys which allows to predict all relevant features such as pseudoelasticity and the shape-memory effect. The theory is based on orientation-distribution of martensite-variants and the minimization of total elastic strain energy and dissipation due to phase-transformation. Applications in a two-dimensional context are given.
