With the development of satellite structure technology, more and more design parameters will affect its structural performance. It is desirable to obtain an optimal structure design with a minimum weight, including op...With the development of satellite structure technology, more and more design parameters will affect its structural performance. It is desirable to obtain an optimal structure design with a minimum weight, including optimal configuration and sizes. The present paper aims to describe an optimization analysis for a satellite structure, including topology optimization and size optimization. Based on the homogenization method, the topology optimization is carried out for the main supporting frame of service module under given constraints and load conditions, and then the sensitivity analysis is made of 15 structural size parameters of the whole satellite and the optimal sizes are obtained. The numerical result shows that the present optimization design method is very effective.展开更多
The objective of this study was to determine the overall thermal elastic behavior of composites by homogenization method. The results obtained were compared with those by other well-known methods such as mean field me...The objective of this study was to determine the overall thermal elastic behavior of composites by homogenization method. The results obtained were compared with those by other well-known methods such as mean field method , self-consistent method and etc. A good agreement is achieved and thus a reliable nwthod for predicting the effective behavior of composite is presented. It is very easy to extend this method to multi-phase composite. The materiol properties determined here include elastic modulus, Poisson ratio and thermal expansion coefficient （CTE）.展开更多
The objective of this study is to investigate the local stress fluctuation in two-phase composite by homogenization method. The composite was described by homogeneous macro structure and periodical micro structure sin...The objective of this study is to investigate the local stress fluctuation in two-phase composite by homogenization method. The composite was described by homogeneous macro structure and periodical micro structure sinudtaneously and the mechanical response of the composite can be described based on both macro and micro dimensional scales. Micro and mocro homogenization problems can be formulated. The effective material properties of the composite and the local stress field in the microstructure of the composite can be determined by solving these equntions.展开更多
In this study,a homogenization method is employed to determine the values of effective elastic modulus for BaZrO3 which is a promising candidate material for electrolyte in solid oxide fuel cell (SOFC).Comparison betw...In this study,a homogenization method is employed to determine the values of effective elastic modulus for BaZrO3 which is a promising candidate material for electrolyte in solid oxide fuel cell (SOFC).Comparison between the homogenization and the analysis data reveals that the difference becomes significant with increasing of porosity when upper 20%.The empire mechanic behavior in a typical planar fuel cell is evaluated using finite element method (FEM).Large stress gradient occurs in vicinity of the interface of the electrolyte and the cathode due to theirs mismatch of thermal expansion coefficient (TEC).Moreover,local processing results reveal that microscopic stress concentration around pore near the interface of the electrolyte and the cathode in the cell perhaps produces cracks which may lead to the fail of the electrolyte and the lower energy convention efficiency.展开更多
In this article, the analytical homogenization method of periodic discrete media（HPDM）and the numerical condensed wave finite element method（CWFEM） are employed to study the longitudinal and transverse vibrations ...In this article, the analytical homogenization method of periodic discrete media（HPDM）and the numerical condensed wave finite element method（CWFEM） are employed to study the longitudinal and transverse vibrations of framed structures. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by the HPDM compared to that by the CWFEM is illustrated in functions of frequency and scale ratio. A parametric study on the thickness of the structure is carried out where the dispersion relation and the relative error are given for three different thicknesses. The dynamics of a finite structure such as natural frequency and forced response are also investigated using the HPDM and the CWFEM.展开更多
A semi-analytical finite element method(SAFEM),based on the two-scale asymptotic homogenization method(AHM)and the finite element method(FEM),is implemented to obtain the effective properties of two-phase fiber-reinfo...A semi-analytical finite element method(SAFEM),based on the two-scale asymptotic homogenization method(AHM)and the finite element method(FEM),is implemented to obtain the effective properties of two-phase fiber-reinforced composites(FRCs).The fibers are periodically distributed and unidirectionally aligned in a homogeneous matrix.This framework addresses the static linear elastic micropolar problem through partial differential equations,subject to boundary conditions and perfect interface contact conditions.The mathematical formulation of the local problems and the effective coefficients are presented by the AHM.The local problems obtained from the AHM are solved by the FEM,which is denoted as the SAFEM.The numerical results are provided,and the accuracy of the solutions is analyzed,indicating that the formulas and results obtained with the SAFEM may serve as the reference points for validating the outcomes of experimental and numerical computations.展开更多
We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these material...We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these materials.The model-predicted values were compared with the experimental results.The results show that when the resin dosage is lower than 10 wt%,the predicted value is lower than the measured value,and the decrease in porosity is obvious;when the resin dosage is higher than 10 wt%,the predicted value is higher than the measured value,the maximum error is 7.95%,and the decrease of porosity is not obvious.The model can predict the trend of the change of elastic modulus.The elastic modulus of resin mineral composites decreases with the increase of porosity.Therefore,the resin dosage should be controlled within 10 wt%when designing the experiments,which provides a guiding direction for the mechanical properties of resin mineral composites to be improved afterward.展开更多
Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Opt...Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Optimization(FPTO)method to achieve smooth topology design.The objective is to optimize the periodic microstructure to maximize the properties of specific materials,such as bulk modulus and shear modulus,or to achieve negative Poisson's ratio.Linear material interpolation is used to eliminate the nonlinear challenges and design dependence caused by material penalty.Furthermore,the three-field density representation technique is applied to augment length scales and solid/void characteristics.Through systematic analysis and numerical simulations,the impacts of various initial designs and optimization parameters on the optimization outcomes are investigated.The results demonstrate that the optimized periodic microstructures exhibit extreme performance with clear boundaries.The identification of appropriate optimization parameters is crucial for enhancing the extreme mechanical properties of material microstructures.It can provide valuable guidance for aerospace component design involving material microstructures and metamaterials.展开更多
The present study investigates the wavespace of Highly Contrasted Structures(HCS)and Highly Dissipative Structures(HDS)by wave-based models.The Asymptotic Homogenization Method(AHM),exploits the asymptotic Zig-Zag mod...The present study investigates the wavespace of Highly Contrasted Structures(HCS)and Highly Dissipative Structures(HDS)by wave-based models.The Asymptotic Homogenization Method(AHM),exploits the asymptotic Zig-Zag model and homogenization technique to compute the bending wavenumbers via a 6th-order equation.The General Laminate Model(GLM)employs Mindlin’s displacement field to establish displacement-constraint relationships and resolves a quadratic Eigenvalue Problem(EVP)of the dispersion relation.The Wave Finite Element(WFE)scheme formulates the Nonlinear Eigenvalue Problem(NEP)for waves in varying directions and tracks complex wavenumbers using Weighted Wave Assurance Criteria(WWAC).Two approaches are introduced to estimate the Damping Loss Factor(DLF)of HDS,with the average DLF calculated by the modal density at various angles where non-homogeneity is present.Evaluation of robustness and accuracy is made by comparing the wavenumbers and DLF obtained from AHM and GLM with WFE.WFE is finally extended to a sandwich metastructure with a non-homogeneous core,and the Power Input Method(PIM)with Finite Element Method(FEM)data is employed to assess the average DLF,demonstrating an enhanced DLF compared to layered configurations with the same material portion,indicating increased energy dissipation due to the bending-shear coupling effects.展开更多
Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing e...Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.展开更多
Asymptotic homogenization (AH) is a general method for predicting the effective coefficient of thermal expansion (CTE) of periodic composites. It has a rigorous mathematical foundation and can give an accurate solutio...Asymptotic homogenization (AH) is a general method for predicting the effective coefficient of thermal expansion (CTE) of periodic composites. It has a rigorous mathematical foundation and can give an accurate solution if the macrostructure is large enough to comprise an infinite number of unit cells. In this paper, a novel implementation algorithm of asymptotic homogenization (NIAH) is developed to calculate the effective CTE of periodic composite materials. Compared with the previous implementation of AH, there are two obvious advantages. One is its implementation as simple as representative volume element (RVE). The new algorithm can be executed easily using commercial finite element analysis (FEA) software as a black box. The detailed process of the new implementation of AH has been provided. The other is that NIAH can simultaneously use more than one element type to discretize a unit cell, which can save much computational cost in predicting the CTE of a complex structure. Several examples are carried out to demonstrate the effectiveness of the new implementation. This work is expected to greatly promote the widespread use of AH in predicting the CTE of periodic composite materials.展开更多
A straightforward multi-scale boundary element method is proposed for global and local mechanical analysis of heterogeneous material.The method is more accurate and convenient than finite element based multi-scale met...A straightforward multi-scale boundary element method is proposed for global and local mechanical analysis of heterogeneous material.The method is more accurate and convenient than finite element based multi-scale method.The formulations of this method are derived by combining the homogenization approach and the fundamental equations of boundary element method.The solution gives the convenient formulations to compute global elastic constants and the local stress field.Finally,two numerical examples of porous material are presented to prove the accuracy and the efficiency of the proposed method.The results show that the method does not require the iteration to obtain the solution of the displacement in micro level.展开更多
A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding ...A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces.展开更多
Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA s...Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.展开更多
Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980...Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.展开更多
In this paper, a new auxiliary equation method is used to find exact travelling wave solutions to the （1＋1）-dimensional KdV equation. Some exact travelling wave solu- tions with parameters have been obtained, which...In this paper, a new auxiliary equation method is used to find exact travelling wave solutions to the （1＋1）-dimensional KdV equation. Some exact travelling wave solu- tions with parameters have been obtained, which cover the existing solutions. Compared to other methods, the presented method is more direct, more concise, more effective, and easier for calculations. In addition, it can be used to solve other nonlinear evolution equations in mathematical physics.展开更多
Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectrosc...Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+.展开更多
A modified homogeneous balance method is proposed by improving some key steps in the homogeneousbalance method.Bilinear equations of some nonlinear evolution equations are derived by using the modified homogeneousbala...A modified homogeneous balance method is proposed by improving some key steps in the homogeneousbalance method.Bilinear equations of some nonlinear evolution equations are derived by using the modified homogeneousbalance method.Generalized Boussinesq equation,KP equation,and mKdV equation are chosen as examples to illustrateour method.This approach is also applicable to a large variety of nonlinear evolution equations.展开更多
The prediction of the mechanical and electric properties of piezoelectric fibre composites has become an active research area in recent years. By means of introducing a boundary layer problem, some new kinds of two-sc...The prediction of the mechanical and electric properties of piezoelectric fibre composites has become an active research area in recent years. By means of introducing a boundary layer problem, some new kinds of two-scale finite element methods for solutions to the electric potential and the displacement for composite material in periodic struc- ture under the coupled piezoelectricity are derived. The coupled two-scale relation of the electric potential and the displacement is set up, and some finite element approximate estimates and numerical examples which show the effectiveness of the method are presented.展开更多
This paper introduces two new types of precise integration methods based on Chebyshev polynomial of the first kind for dynamic response analysis of structures, namely the integral formula method （IFM） and the homoge...This paper introduces two new types of precise integration methods based on Chebyshev polynomial of the first kind for dynamic response analysis of structures, namely the integral formula method （IFM） and the homogenized initial system method （HISM）. In both methods, nonlinear variable loadings within time intervals are simulated using Chebyshev polynomials of the first kind before a direct integration is performed. Developed on the basis of the integral formula, the recurrence relationship of the integral computation suggested in this paper is combined with the Crout decomposed method to solve linear algebraic equations. In this way, the IFM based on Chebyshev polynomial of the first kind is constructed. Transforming the non-homogenous initial system to the homogeneous dynamic system, and developing a special scheme without dimensional expansion, the HISM based on Chebyshev polynomial of the first kind is able to avoid the matrix inversion operation. The accuracy of the time integration schemes is examined and compared with other commonly used schemes, and it is shown that a greater accuracy as well as less time consuming can be achieved. Two numerical examples are presented to demonstrate the applicability of these new methods.展开更多
文摘With the development of satellite structure technology, more and more design parameters will affect its structural performance. It is desirable to obtain an optimal structure design with a minimum weight, including optimal configuration and sizes. The present paper aims to describe an optimization analysis for a satellite structure, including topology optimization and size optimization. Based on the homogenization method, the topology optimization is carried out for the main supporting frame of service module under given constraints and load conditions, and then the sensitivity analysis is made of 15 structural size parameters of the whole satellite and the optimal sizes are obtained. The numerical result shows that the present optimization design method is very effective.
文摘The objective of this study was to determine the overall thermal elastic behavior of composites by homogenization method. The results obtained were compared with those by other well-known methods such as mean field method , self-consistent method and etc. A good agreement is achieved and thus a reliable nwthod for predicting the effective behavior of composite is presented. It is very easy to extend this method to multi-phase composite. The materiol properties determined here include elastic modulus, Poisson ratio and thermal expansion coefficient （CTE）.
基金Funded by National High-Tech Foundation(State 863 Plan)(No.2003AA305920)
文摘The objective of this study is to investigate the local stress fluctuation in two-phase composite by homogenization method. The composite was described by homogeneous macro structure and periodical micro structure sinudtaneously and the mechanical response of the composite can be described based on both macro and micro dimensional scales. Micro and mocro homogenization problems can be formulated. The effective material properties of the composite and the local stress field in the microstructure of the composite can be determined by solving these equntions.
基金the support by the Medicine and Engineering Project
文摘In this study,a homogenization method is employed to determine the values of effective elastic modulus for BaZrO3 which is a promising candidate material for electrolyte in solid oxide fuel cell (SOFC).Comparison between the homogenization and the analysis data reveals that the difference becomes significant with increasing of porosity when upper 20%.The empire mechanic behavior in a typical planar fuel cell is evaluated using finite element method (FEM).Large stress gradient occurs in vicinity of the interface of the electrolyte and the cathode due to theirs mismatch of thermal expansion coefficient (TEC).Moreover,local processing results reveal that microscopic stress concentration around pore near the interface of the electrolyte and the cathode in the cell perhaps produces cracks which may lead to the fail of the electrolyte and the lower energy convention efficiency.
文摘In this article, the analytical homogenization method of periodic discrete media（HPDM）and the numerical condensed wave finite element method（CWFEM） are employed to study the longitudinal and transverse vibrations of framed structures. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by the HPDM compared to that by the CWFEM is illustrated in functions of frequency and scale ratio. A parametric study on the thickness of the structure is carried out where the dispersion relation and the relative error are given for three different thicknesses. The dynamics of a finite structure such as natural frequency and forced response are also investigated using the HPDM and the CWFEM.
基金Project supported by the National Council of Humanities,Sciences,and Technologies of Mexico(Nos.CF-2023-G-792 and CF-2023-G-1458)the National Council for Scientific and Technological Development of Brazil(No.09/2023)the Research on Productivity of Brazil(No.307188/2023-0)。
文摘A semi-analytical finite element method(SAFEM),based on the two-scale asymptotic homogenization method(AHM)and the finite element method(FEM),is implemented to obtain the effective properties of two-phase fiber-reinforced composites(FRCs).The fibers are periodically distributed and unidirectionally aligned in a homogeneous matrix.This framework addresses the static linear elastic micropolar problem through partial differential equations,subject to boundary conditions and perfect interface contact conditions.The mathematical formulation of the local problems and the effective coefficients are presented by the AHM.The local problems obtained from the AHM are solved by the FEM,which is denoted as the SAFEM.The numerical results are provided,and the accuracy of the solutions is analyzed,indicating that the formulas and results obtained with the SAFEM may serve as the reference points for validating the outcomes of experimental and numerical computations.
基金Funded by Demonstration Platform for the Production and Application of Key Materials for High-grade CNC Machine Tools(No.2020-370104-34-03-043952)。
文摘We proposed a microscopic mechanical model for the effective elastic modulus of resin mineral composites based on the Mori-Tanaka method and equivalent inclusion theory to predict the elastic modulus of these materials.The model-predicted values were compared with the experimental results.The results show that when the resin dosage is lower than 10 wt%,the predicted value is lower than the measured value,and the decrease in porosity is obvious;when the resin dosage is higher than 10 wt%,the predicted value is higher than the measured value,the maximum error is 7.95%,and the decrease of porosity is not obvious.The model can predict the trend of the change of elastic modulus.The elastic modulus of resin mineral composites decreases with the increase of porosity.Therefore,the resin dosage should be controlled within 10 wt%when designing the experiments,which provides a guiding direction for the mechanical properties of resin mineral composites to be improved afterward.
基金supported by the financial support from the National Natural Science Foundation of China(No.52172356)Hunan Provincial Natural Science Foundation of China(No.2022JJ10012)。
文摘Topology optimization stands as a pivotal technique in realizing periodic microstructure design.A novel approach is proposed,integrating the energy-based homogenization method with the Floating Projection Topology Optimization(FPTO)method to achieve smooth topology design.The objective is to optimize the periodic microstructure to maximize the properties of specific materials,such as bulk modulus and shear modulus,or to achieve negative Poisson's ratio.Linear material interpolation is used to eliminate the nonlinear challenges and design dependence caused by material penalty.Furthermore,the three-field density representation technique is applied to augment length scales and solid/void characteristics.Through systematic analysis and numerical simulations,the impacts of various initial designs and optimization parameters on the optimization outcomes are investigated.The results demonstrate that the optimized periodic microstructures exhibit extreme performance with clear boundaries.The identification of appropriate optimization parameters is crucial for enhancing the extreme mechanical properties of material microstructures.It can provide valuable guidance for aerospace component design involving material microstructures and metamaterials.
基金supported by the Natural Sciences and Engineering Research Council of Canada-Discovery Grant(individual)Program(No.NSEC-DG#355433-2009)funded by the LabEx CeLyA(Centre Lyonnais d’Acoustique,No.ANR-10-LABX-0060)of Universite?de Lyon。
文摘The present study investigates the wavespace of Highly Contrasted Structures(HCS)and Highly Dissipative Structures(HDS)by wave-based models.The Asymptotic Homogenization Method(AHM),exploits the asymptotic Zig-Zag model and homogenization technique to compute the bending wavenumbers via a 6th-order equation.The General Laminate Model(GLM)employs Mindlin’s displacement field to establish displacement-constraint relationships and resolves a quadratic Eigenvalue Problem(EVP)of the dispersion relation.The Wave Finite Element(WFE)scheme formulates the Nonlinear Eigenvalue Problem(NEP)for waves in varying directions and tracks complex wavenumbers using Weighted Wave Assurance Criteria(WWAC).Two approaches are introduced to estimate the Damping Loss Factor(DLF)of HDS,with the average DLF calculated by the modal density at various angles where non-homogeneity is present.Evaluation of robustness and accuracy is made by comparing the wavenumbers and DLF obtained from AHM and GLM with WFE.WFE is finally extended to a sandwich metastructure with a non-homogeneous core,and the Power Input Method(PIM)with Finite Element Method(FEM)data is employed to assess the average DLF,demonstrating an enhanced DLF compared to layered configurations with the same material portion,indicating increased energy dissipation due to the bending-shear coupling effects.
基金National Natural Science Foundation of China （90405016, 10676028） 973 Program （2006CB601205）+1 种基金 863 Project （2006AA04Z 122） Aeronautical Science Foundation （04B53080, 2006ZA 53006） and 111 Project （B07050）
文摘Sensitivity analysis and topology optimization of microstructures using strain energy-based method is presented. Compared with homogenization method, the strain energy-based method has advantages of higher computing efficiency and simplified programming. Both the dual convex programming method and perimeter constraint scheme are used to optimize the 2D and 3D microstructures. Numerical results indicate that the strain energy-based method has the same effectiveness as that of homogenization method for orthotropic materials.
基金supported by the National Natural Science Foundation of China (Grants 11332004, 11572071)the Program for Changjiang Scholars and Innovative Research Team in Dalian University of Technology (PCSIRT)+2 种基金111 Project (Grant B14013)the CATIC Industrial Production Projects (Grant CXY2013DLLG32)the Fundamental Research Funds for the Central Universities (Grant DUT15ZD101)
文摘Asymptotic homogenization (AH) is a general method for predicting the effective coefficient of thermal expansion (CTE) of periodic composites. It has a rigorous mathematical foundation and can give an accurate solution if the macrostructure is large enough to comprise an infinite number of unit cells. In this paper, a novel implementation algorithm of asymptotic homogenization (NIAH) is developed to calculate the effective CTE of periodic composite materials. Compared with the previous implementation of AH, there are two obvious advantages. One is its implementation as simple as representative volume element (RVE). The new algorithm can be executed easily using commercial finite element analysis (FEA) software as a black box. The detailed process of the new implementation of AH has been provided. The other is that NIAH can simultaneously use more than one element type to discretize a unit cell, which can save much computational cost in predicting the CTE of a complex structure. Several examples are carried out to demonstrate the effectiveness of the new implementation. This work is expected to greatly promote the widespread use of AH in predicting the CTE of periodic composite materials.
基金Supported by the National Natural Science Foundation of China(51105195,51075204)the Aeronautical Science Foundation of China(2011ZB52024)
文摘A straightforward multi-scale boundary element method is proposed for global and local mechanical analysis of heterogeneous material.The method is more accurate and convenient than finite element based multi-scale method.The formulations of this method are derived by combining the homogenization approach and the fundamental equations of boundary element method.The solution gives the convenient formulations to compute global elastic constants and the local stress field.Finally,two numerical examples of porous material are presented to prove the accuracy and the efficiency of the proposed method.The results show that the method does not require the iteration to obtain the solution of the displacement in micro level.
基金Project supported by the Desenvolvimento e Aplicaoes de Mtodos Matemticos de Homogeneizaao(CAPES)(No.88881.030424/2013-01)the Homogeneizao Reiterada Aplicada a Meios Dependentes de Múltiplas Escalas con Contato Imperfeito Entre as Fases(CNPq)(Nos.450892/2016-6and 303208/2014-7)the Caracterizacin de Propiedades Efectivas de Tejidos Biolgicos Sanos y Cancerosos(CONACYT)(No.2016–01–3212)
文摘A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces.
基金financially supported by the National Key R&D Program of China(No.2021YFB3801901)the National Natural Science Foundation of China(No.22075188 and U19A2095)supported by State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology。
文摘Poly(lactic acid)(PLA),a bio-based polymer,is considered to be a sustainable alternative to conventional petroleum-based plastics.However,owing to its widespread use and relatively slow degradation rate in water,PLA still poses potential environmental pollution risks after being discarded.The efficient chemical recycling of PLA represents an attractive approach to addressing both resource reuse and environmental pollution challenges caused by its waste.Hydrolysis is the predominant method of industrial recycling.However,because PLA is insoluble in water,efficient heterogeneous hydrolysis requires high-temperature and high-pressure conditions.In this study,an efficient homogenous hydrolysis method capable of simultaneously dissolving PLA and calcium hydroxide(Ca(OH)_(2))was developed.Suitable solvents for this method were screened,and it was found that PLA hydrolysis using dioxane and 1,4,7,10,13-Pen-taoxacyclopentadecane as solvents achieved conversion rates of 93%and 90%,respectively,within 2 h at room temperature.Notably,the hydrolysis product,calcium lactate,precipitated as a solid from the solvent and therefore self-separated from the reaction solution.The solvent,acid/base conditions,water content,and depolymerization kinetics were investigated.Compared with previously reported hydrolysis methods,the enhanced efficiency observed in this study can be attributed to the concurrent solvation of PLA and Ca(OH)_(2),which maintains homogeneity throughout the reaction process.Additionally,this method facilitates closed-loop recycling of PLA and is compatible with the highly selective recovery of PLA from various types of PLA products.
基金the Foundation for the University by Educational Department of Liaoning (05L337)Key Laboratory of Rare Earth Chemistry and Physics, Chinese Academy of Sciences
文摘Y2O3： Er^3＋, Yb^3＋ nanoparticles were synthesized by a homogeneous precipitation method without and with different concentrations of EDTA 2Na. Upconversion luminescence spectra of the samples were studied under 980 nm laser excitation. The results of XRD showed that the obtained Y2O3：Er^3＋,Yb^3＋ nanoparticles were of a cubic structure. The average crystallite sizes calculated were in the range of 28-40 nm. Green and red upconversion emission were observed, and attributed to ^2H11/2,^4S3/2→^4I15/2 and ^4F9/2→^4I15/2 transitions of the ion, respectively. The ratio of the intensity of green emission to that of red emission drastically changed with a change in the EDTA 2Na concentration. In the sample synthesized without EDTA, the relative intensity of the green emission was weaker than that of the red emission. The relative intensities of green emission increased with the increased amount of EDTA 2Na used. The possible upconversion luminescence mechanisms were discussed.
基金supported by the National Natural Science Foundation of China (No.10461005)the Ph.D.Programs Foundation of Ministry of Education of China (No.20070128001)the High Education Science Research Program of Inner Mongolia (No.NJZY08057)
文摘In this paper, a new auxiliary equation method is used to find exact travelling wave solutions to the （1＋1）-dimensional KdV equation. Some exact travelling wave solu- tions with parameters have been obtained, which cover the existing solutions. Compared to other methods, the presented method is more direct, more concise, more effective, and easier for calculations. In addition, it can be used to solve other nonlinear evolution equations in mathematical physics.
基金financially supported by the Science and Technology Research Project of Department of Education of Liaoning Province,China(No.L2011063)
文摘Nanocrystalline Gd3Ga5O12:Eu3+ with cubic phase was prepared by a urea homogeneous precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the samples. The effects of the initial solution pH value and urea content on the structure of the sample were studied. The XRD results show that pure phase Gd3Ga5O12 can be obtained at pH =6 and pH =8 of the initial solution. The average crystallite size can be calculated as in the range of 24~33 nm. The average crystallite size decreases with increasing molar ratio of urea to metal ion. The results of excitation spectra and emission spectra show that the emission peaks are ascribed to 5D0→7FJ transitions of Eu3+, and the magnetic dipole transition originated from 5D0 →7F1 of Eu3+ is the strongest; the broad excitation bands belong to change transfer band of Eu?O and the host absorption of Gd3Ga5O12. An efficient energy transfer occurs from Gd3+ to Eu3+.
基金Supported by the National Natural Science Foundation of China under Grant No. 11071209the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province under Grant No. 10KJBll0011
文摘A modified homogeneous balance method is proposed by improving some key steps in the homogeneousbalance method.Bilinear equations of some nonlinear evolution equations are derived by using the modified homogeneousbalance method.Generalized Boussinesq equation,KP equation,and mKdV equation are chosen as examples to illustrateour method.This approach is also applicable to a large variety of nonlinear evolution equations.
基金supported by the National Natural Science Foundation of China(Nos.10801042 and 11171257)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20104410120001)
文摘The prediction of the mechanical and electric properties of piezoelectric fibre composites has become an active research area in recent years. By means of introducing a boundary layer problem, some new kinds of two-scale finite element methods for solutions to the electric potential and the displacement for composite material in periodic struc- ture under the coupled piezoelectricity are derived. The coupled two-scale relation of the electric potential and the displacement is set up, and some finite element approximate estimates and numerical examples which show the effectiveness of the method are presented.
基金Hunan Provincial Natural Science Foundation Under Grant No.02JJY2085
文摘This paper introduces two new types of precise integration methods based on Chebyshev polynomial of the first kind for dynamic response analysis of structures, namely the integral formula method （IFM） and the homogenized initial system method （HISM）. In both methods, nonlinear variable loadings within time intervals are simulated using Chebyshev polynomials of the first kind before a direct integration is performed. Developed on the basis of the integral formula, the recurrence relationship of the integral computation suggested in this paper is combined with the Crout decomposed method to solve linear algebraic equations. In this way, the IFM based on Chebyshev polynomial of the first kind is constructed. Transforming the non-homogenous initial system to the homogeneous dynamic system, and developing a special scheme without dimensional expansion, the HISM based on Chebyshev polynomial of the first kind is able to avoid the matrix inversion operation. The accuracy of the time integration schemes is examined and compared with other commonly used schemes, and it is shown that a greater accuracy as well as less time consuming can be achieved. Two numerical examples are presented to demonstrate the applicability of these new methods.
