In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefl...In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefly given for two-scale analysis （TSA） of the composite materials. And then a two-scale computation formulation of strains and stresses is developed by displacement solution with orthotropic material coefficients for three kinds of such composites structures, i.e., the tension column with a square cross section, the bending cantilever with a rectangular cross section and the torsion column with a circle cross section. The strength formulas for the three kinds of structures are derived and the TSM procedure is discussed. Finally the numerical results of stiffness and strength are presented and compared with experimental data. It shows that the TSM method in this paper is feasible and valid for predicting both the stiffness and the strength of the composite materials with periodic configuration.展开更多
In this paper,a stochastic second-order two-scale(SSOTS)method is proposed for predicting the non-deterministic mechanical properties of composites with random interpenetrating phase.Firstly,based on random morphology...In this paper,a stochastic second-order two-scale(SSOTS)method is proposed for predicting the non-deterministic mechanical properties of composites with random interpenetrating phase.Firstly,based on random morphology description functions(RMDF),the randomness of the material properties of the constituents as well as the correlation among these random properties are fully characterized through the topologies of the constituents.Then,by virtue of multiscale asymptotic analysis,the random effective quantities such as stiffness parameters and strength parameters along with their numerical computation formulae are derived by a SSOTS strategy combined with the Monte-Carlo method.Finally,the SSOTS method developed in this paper shows an excellent computational accuracy,and therefore present an important advance towards computationally efficient multiscale modeling frameworks considering microstructure uncertainties.展开更多
A two-scale method is proposed to simulate the essential behavior of bolted connections in structures includingelevated temperatures.It is presented,verified,and validated for the structural behavior of two plates,con...A two-scale method is proposed to simulate the essential behavior of bolted connections in structures includingelevated temperatures.It is presented,verified,and validated for the structural behavior of two plates,connectedby a bolt,under a variety of loads and elevated temperatures.The method consists of a global-scale model thatsimulates the structure(here the two plates)by volume finite elements,and in which the bolt is modelled bya spring.The spring properties are provided by a smallscale model,in which the bolt is modelled by volumeelements,and for which the boundary conditions are retrieved from the global-scale model.To ensure the small-scale model to be as computationally efficient as possible,simplifications are discussed regarding the materialmodel and the modelling of the threads.For the latter,this leads to the experimentally validated application ofa non-threaded shank with its stress area.It is shown that a non-linear elastic spring is needed for the bolt inthe global-scale model,so the post-peak behavior of the structure can be described efficiently.All types of boltedconnection failure as given by design standards are simulated by the twoscale method,which is successfullyvalidated(except for net section failure)by experiments,and verified by a detailed system model,which modelsthe structure in full detail.The sensitivity to the size of the part of the plate used in the small-scale modelis also studied.Finally,multi-directional load cases,also for elevated temperatures,are studied with the two-scale method and verified with the detailed system model.As a result,a computationally efficient finite elementmodelling approach is provided for all possible combined load actions(except for nut thread failure and netsection failure)and temperatures.The two-scale method is shown to be insightful,for it contains a functionalseparation of scales,revealing their relationships,and consequently,local small-scale non-convergence can behandled.Not presented in this paper,but the two-scale method can be used in e.g.computationally expensive two-way coupled fire-structure simulations,where it is beneficial for distributed computing and densely packed boltconfigurations with stiffplates,for which a single small-scale model may be representative for several connections.展开更多
This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of...This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of the problem by a statistical second-order two-scale （SSOTS） analysis method and the algorithm procedure based on the finite-element difference method are presented. Numerical results of coupled cases are compared with those of uncoupled cases. It shows that the coupling effects on temperature, thermal flux, displacement, and stresses are very distinct, and the micro- characteristics of particles affect the coupling effect of the random composites. Furthermore, the coupling effect causes a lag in the variations of temperature, thermal flux, displacement, and stresses.展开更多
In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,th...In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.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 considers the bending behaviors of composite plate with 3-D periodic configuration.A second-order two-scale(SOTS)computational method is designed by means of construction way.First,by 3-D elastic composite ...This paper considers the bending behaviors of composite plate with 3-D periodic configuration.A second-order two-scale(SOTS)computational method is designed by means of construction way.First,by 3-D elastic composite plate model,the cell functions which are defined on the reference cell are constructed.Then the effective homogenization parameters of composites are calculated,and the homogenized plate problem on original domain is defined.Based on the Reissner-Mindlin deformation pattern,the homogenization solution is obtained.And then the SOTS’s approximate solution is obtained by the cell functions and the homogenization solution.Second,the approximation of the SOTS’s solution in energy norm is analyzed and the residual of SOTS’s solution for 3-D original in the pointwise sense is investigated.Finally,the procedure of SOTS’s method is given.A set of numerical results are demonstrated for predicting the effective parameters and the displacement and strains of composite plate.It shows that SOTS’s method can capture the 3-D local behaviors caused by3-D micro-structures well.展开更多
The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elasti...The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspon- dence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale （SOTS） computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calcu- lating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement ap- proximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.展开更多
The purpose of this paper is to solve nonselfadjoint elliptic problems with rapidly oscillatory coefficients. A two-order and two-scale approximate solution expression for nonselfadjoint elliptic problems is considere...The purpose of this paper is to solve nonselfadjoint elliptic problems with rapidly oscillatory coefficients. A two-order and two-scale approximate solution expression for nonselfadjoint elliptic problems is considered, and the error estimation of the twoorder and two-scale approximate solution is derived. The numerical result shows that the presented approximation solution is effective.展开更多
In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to ...In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.展开更多
Convex feasibility problems are widely used in image reconstruction,sparse signal recovery,and other areas.This paper is devoted to considering a class of convex feasibility problem arising from sparse signal recovery...Convex feasibility problems are widely used in image reconstruction,sparse signal recovery,and other areas.This paper is devoted to considering a class of convex feasibility problem arising from sparse signal recovery.We rst derive the projection formulas for a vector onto the feasible sets.The centralized circumcentered-reection method is designed to solve the convex feasibility problem.Some numerical experiments demonstrate the feasibility and e ectiveness of the proposed algorithm,showing superior performance compared to conventional alternating projection methods.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configur...This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configuration for the structure with random distribution is briefly characterized.Secondly,the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell.Then,the statistical prediction algorithm based on the proposed two-scale model is described in detail.Finally,some numerical experiments are proposed,which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.展开更多
The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titani...The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.展开更多
The Geometrical Optics(GO)approach and the FAST Emissivity Model(FASTEM)are widely used to estimate the surface radiative components in atmospheric radiative transfer simulations,but their applications are limited in ...The Geometrical Optics(GO)approach and the FAST Emissivity Model(FASTEM)are widely used to estimate the surface radiative components in atmospheric radiative transfer simulations,but their applications are limited in specific conditions.In this study,a two-scale reflectivity model(TSRM)and a two-scale emissivity model(TSEM)are developed from the two-scale roughness theory.Unlike GO which only computes six non-zero elements in the reflectivity matrix,The TSRM includes 16 elements of Stokes reflectivity matrix which are important for improving radiative transfer simulation accuracy in a scattering atmosphere.It covers the frequency range from L-to W-bands.The dependences of all TSRM elements on zenith angle,wind speed,and frequency are derived and analyzed in details.For a set of downwelling radiances in microwave frequencies,the reflected upwelling brightness temperature(BTs)are calculated from both TSRM and GO and compared for analyzing their discrepancies.The TSRM not only includes the effects of GO but also accounts for the small-scale Bragg scattering effect in an order of several degrees in Kelvins in brightness temperature.Also,the third and fourth components of the Stokes vector can only be produced from the TSRM.For the emitted radiation,BT differences in vertical polarization between a TSEM and FASTEM are generally less than 5 K when the satellite zenith angle is less than 40°,whereas those for the horizontal component can be quite significant,greater than 20 K.展开更多
A particle nonlinear two-scale kp-εp turbulence model is proposed for simulating the anisotropic turbulent two-phase flow. The particle kinetic energy equation for two-scale fluctuation, particle energy transfer rate...A particle nonlinear two-scale kp-εp turbulence model is proposed for simulating the anisotropic turbulent two-phase flow. The particle kinetic energy equation for two-scale fluctuation, particle energy transfer rate equation for large-scale fluctuation, and particle turbulent kinetic energy dissipation rate equation for small-scale fluctuation are derived and closed. This model is used to simulate gas-particle flows in a sudden-expansion chamber. The simulation is com- pared with the experiment and with those obtained by using another two kinds of tow-phase turbulence model, such as the single-scale k-ε two-phase turbulence model and the particle two-scale second-order moment （USM） two-phase turbulence model. It is shown that the present model gives simulation in much better agreement with the experiment than the single-scale k-ε two-phase turbulence model does and is almost as good as the particle two-scale USM turbu-lence model.展开更多
A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concepts of particle large-scale fluctuation due to turbulence and particle small-scale flu...A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concepts of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision and through a unified treatment of these two kinds of fluctuations. The proposed model is used to simulate gas-particle flows in a channel and in a downer. Simulation results are in agreement with the experimental results reported in references and are near the results obtained using the sin- gle-scale second-order moment two-phase turbulence model superposed with a particle collision model （USM-θ model） in most regions.展开更多
We study the hyperbolic–parabolic equations with rapidly oscillating coefficients. The formal second-order two-scale asymptotic expansion solutions are constructed by the multiscale asymptotic analysis. In addition, ...We study the hyperbolic–parabolic equations with rapidly oscillating coefficients. The formal second-order two-scale asymptotic expansion solutions are constructed by the multiscale asymptotic analysis. In addition, we theoretically explain the importance of the second-order two-scale solution by the error analysis in the pointwise sense. The associated explicit convergence rates are also obtained. Then a second-order two-scale numerical method based on the Newmark scheme is presented to solve the equations. Finally, some numerical examples are used to verify the effectiveness and efficiency of the multiscale numerical algorithm we proposed.展开更多
The dynamic vibration absorber with inerter and grounded stiffness(IGDVA)is used to control a two-scale system subject to a weak periodic perturbation.The vibration suppression effect is remarkable.The amplitude of th...The dynamic vibration absorber with inerter and grounded stiffness(IGDVA)is used to control a two-scale system subject to a weak periodic perturbation.The vibration suppression effect is remarkable.The amplitude of the main system coupled with absorber is significantly reduced,and the high frequency vibration completely disappears.First,through the slow-fast analysis and stability theory,it is found that the stability of the autonomous system exerts a notable regulating effect on the vibration response of the non-autonomous system.After adding the dynamic vibrator absorber,the center in the autonomous system changes to an asymptotically stable focus,consequently suppressing the vibration in the non-autonomous system.Further research reveals that the parameters of the absorber affect the real parts of the eigenvalues of the autonomous system,thereby regulating the stability of the system.Transitioning from a qualitative standpoint to a quantitative approach,a comparison of the solutions before and after the introduction of the dynamic absorber reveals that,when the grounded stiffness ratio and the mass ratio of the dynamic absorber are not equal,the high-frequency part in the analytical solution disappears.As a result,this leads to a reduction in the amplitude of the trajectory,achieving a vibration reduction effect.展开更多
A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluc...A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The proposed model is used to simulate gas-particle downer reactor flows. The computational results of both particle volume fraction and mean velocity are in agreement with the experimental results. After analyzing effects of empirical coefficient on prediction results, we can come to a conclusion that, inside the limit range of empirical coefficient, the predictions do not reveal a large sensitivity to the empirical coefficient in the downer reactor, but a relatively great change of the constants has important effect on the prediction.展开更多
基金The project supported by the Special Funds for Major State Basic Research Project (2005CB321704)the National Natural Science Foundation of China (10590353 and 90405016)The English text was polished by Yunming Chen
文摘In this paper, a two-scale method （TSM） is presented for identifying the mechanics parameters such as stiffness and strength of composite materials with small periodic configuration. Firstly, a formulation is briefly given for two-scale analysis （TSA） of the composite materials. And then a two-scale computation formulation of strains and stresses is developed by displacement solution with orthotropic material coefficients for three kinds of such composites structures, i.e., the tension column with a square cross section, the bending cantilever with a rectangular cross section and the torsion column with a circle cross section. The strength formulas for the three kinds of structures are derived and the TSM procedure is discussed. Finally the numerical results of stiffness and strength are presented and compared with experimental data. It shows that the TSM method in this paper is feasible and valid for predicting both the stiffness and the strength of the composite materials with periodic configuration.
基金partially supported by China Postdoctoral Science Foundation(2018M643573)National Natural Science Foundation of Shaanxi Province(2019JQ-048)+2 种基金National Natural Science Foundation of China(51739007,61971328,11301392 and 11961009)of ChinaShanghai Peak Discipline Program for Higher Education Institutions(ClassⅠ)–Civil EngineeringFundamental Research Funds for the Central Universities(No.22120180529)。
文摘In this paper,a stochastic second-order two-scale(SSOTS)method is proposed for predicting the non-deterministic mechanical properties of composites with random interpenetrating phase.Firstly,based on random morphology description functions(RMDF),the randomness of the material properties of the constituents as well as the correlation among these random properties are fully characterized through the topologies of the constituents.Then,by virtue of multiscale asymptotic analysis,the random effective quantities such as stiffness parameters and strength parameters along with their numerical computation formulae are derived by a SSOTS strategy combined with the Monte-Carlo method.Finally,the SSOTS method developed in this paper shows an excellent computational accuracy,and therefore present an important advance towards computationally efficient multiscale modeling frameworks considering microstructure uncertainties.
基金supported by the China Scholarship Council (Grant No.2018-0861-0211).
文摘A two-scale method is proposed to simulate the essential behavior of bolted connections in structures includingelevated temperatures.It is presented,verified,and validated for the structural behavior of two plates,connectedby a bolt,under a variety of loads and elevated temperatures.The method consists of a global-scale model thatsimulates the structure(here the two plates)by volume finite elements,and in which the bolt is modelled bya spring.The spring properties are provided by a smallscale model,in which the bolt is modelled by volumeelements,and for which the boundary conditions are retrieved from the global-scale model.To ensure the small-scale model to be as computationally efficient as possible,simplifications are discussed regarding the materialmodel and the modelling of the threads.For the latter,this leads to the experimentally validated application ofa non-threaded shank with its stress area.It is shown that a non-linear elastic spring is needed for the bolt inthe global-scale model,so the post-peak behavior of the structure can be described efficiently.All types of boltedconnection failure as given by design standards are simulated by the twoscale method,which is successfullyvalidated(except for net section failure)by experiments,and verified by a detailed system model,which modelsthe structure in full detail.The sensitivity to the size of the part of the plate used in the small-scale modelis also studied.Finally,multi-directional load cases,also for elevated temperatures,are studied with the two-scale method and verified with the detailed system model.As a result,a computationally efficient finite elementmodelling approach is provided for all possible combined load actions(except for nut thread failure and netsection failure)and temperatures.The two-scale method is shown to be insightful,for it contains a functionalseparation of scales,revealing their relationships,and consequently,local small-scale non-convergence can behandled.Not presented in this paper,but the two-scale method can be used in e.g.computationally expensive two-way coupled fire-structure simulations,where it is beneficial for distributed computing and densely packed boltconfigurations with stiffplates,for which a single small-scale model may be representative for several connections.
基金supported by the Special Funds for the National Basic Research Program of China(Grant No.2012CB025904)the National Natural ScienceFoundation of China(Grant Nos.90916027 and 11302052)
文摘This paper focuses on the dynamic thermo-mechanical coupled response of random particulate composite materials. Both the inertia term and coupling term are considered in the dynamic coupled problem. The formulation of the problem by a statistical second-order two-scale （SSOTS） analysis method and the algorithm procedure based on the finite-element difference method are presented. Numerical results of coupled cases are compared with those of uncoupled cases. It shows that the coupling effects on temperature, thermal flux, displacement, and stresses are very distinct, and the micro- characteristics of particles affect the coupling effect of the random composites. Furthermore, the coupling effect causes a lag in the variations of temperature, thermal flux, displacement, and stresses.
基金supported by the National Natural Science Foundation of China(Grants 11471262,11202032)the Basic Research Project of National Defense(Grant B 1520132013)supported by the State Key Laboratory of Science and Engineering Computing and Center for high performance computing of Northwestem Polytechnical University
文摘In this paper,a statistical second-order twoscale（SSOTS） method is developed to simulate the dynamic thcrmo-mechanical performances of the statistically inhomogeneous materials.For this kind of composite material,the random distribution characteristics of particles,including the shape,size,orientation,spatial location,and volume fractions,are all considered.Firstly,the repre.sentation for the microscopic configuration of the statistically inhomogeneous materials is described.Secondly,the SSOTS formulation for the dynamic thermo-mechanical coupled problem is proposed in a constructive way,including the cell problems,effective thermal and mechanical parameters,homogenized problems,and the SSOTS formulas of the temperatures,displacements,heat flux densities and stresses.And then the algorithm procedure corresponding to the SSOTS method is brought forward.The numerical results obtained by using the SSOTS algorithm are compared with those by classical methods.In addition,the thermo-mechanical coupling effect is studied by comparing the results of coupled case with those of uncoupled case.It demonstrates that the coupling effect on the temperatures,heat flux densities,displacements,and stresses is very distinct.The results show that the SSOTS method is valid to predict the dynamic thermo-mechanical coupled performances of statistically inhomogeneous materials.
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supported by National Natural Science Foundation of China(GrantNo.90916027)the Special Funds for National Basic Research Program of China(Grant No.2010CB832702)+1 种基金Foundation of Guizhou Science and Technology Department(Grant No.[2013]2144)the State Key Laboratory of Science and Engineering Computing
文摘This paper considers the bending behaviors of composite plate with 3-D periodic configuration.A second-order two-scale(SOTS)computational method is designed by means of construction way.First,by 3-D elastic composite plate model,the cell functions which are defined on the reference cell are constructed.Then the effective homogenization parameters of composites are calculated,and the homogenized plate problem on original domain is defined.Based on the Reissner-Mindlin deformation pattern,the homogenization solution is obtained.And then the SOTS’s approximate solution is obtained by the cell functions and the homogenization solution.Second,the approximation of the SOTS’s solution in energy norm is analyzed and the residual of SOTS’s solution for 3-D original in the pointwise sense is investigated.Finally,the procedure of SOTS’s method is given.A set of numerical results are demonstrated for predicting the effective parameters and the displacement and strains of composite plate.It shows that SOTS’s method can capture the 3-D local behaviors caused by3-D micro-structures well.
基金Project supported by the National Natural Science Foundation of China(No.11471262)
文摘The correspondence principle is an important mathematical technique to compute the non-ageing linear viscoelastic problem as it allows to take advantage of the computational methods originally developed for the elastic case. However, the correspon- dence principle becomes invalid when the materials exhibit ageing. To deal with this problem, a second-order two-scale （SOTS） computational method in the time domain is presented to predict the ageing linear viscoelastic performance of composite materials with a periodic structure. First, in the time domain, the SOTS formulation for calcu- lating the effective relaxation modulus and displacement approximate solutions of the ageing viscoelastic problem is formally derived. Error estimates of the displacement ap- proximate solutions for SOTS method are then given. Numerical results obtained by the SOTS method are shown and compared with those by the finite element method in a very fine mesh. Both the analytical and numerical results show that the SOTS computational method is feasible and efficient to predict the ageing linear viscoelastic performance of composite materials with a periodic structure.
基金Project supported by the National Natural Science Foundation of China(No.10590353)the Science Research Project of National University of Defense Technology(No.JC09-02-05)
文摘The purpose of this paper is to solve nonselfadjoint elliptic problems with rapidly oscillatory coefficients. A two-order and two-scale approximate solution expression for nonselfadjoint elliptic problems is considered, and the error estimation of the twoorder and two-scale approximate solution is derived. The numerical result shows that the presented approximation solution is effective.
基金Supported in part by Natural Science Foundation of Guangxi(2023GXNSFAA026246)in part by the Central Government's Guide to Local Science and Technology Development Fund(GuikeZY23055044)in part by the National Natural Science Foundation of China(62363003)。
文摘In this paper,we consider the maximal positive definite solution of the nonlinear matrix equation.By using the idea of Algorithm 2.1 in ZHANG(2013),a new inversion-free method with a stepsize parameter is proposed to obtain the maximal positive definite solution of nonlinear matrix equation X+A^(*)X|^(-α)A=Q with the case 0<α≤1.Based on this method,a new iterative algorithm is developed,and its convergence proof is given.Finally,two numerical examples are provided to show the effectiveness of the proposed method.
基金Supported by the Natural Science Foundation of Guangxi Province(Grant Nos.2023GXNSFAA026067,2024GXN SFAA010521)the National Natural Science Foundation of China(Nos.12361079,12201149,12261026).
文摘Convex feasibility problems are widely used in image reconstruction,sparse signal recovery,and other areas.This paper is devoted to considering a class of convex feasibility problem arising from sparse signal recovery.We rst derive the projection formulas for a vector onto the feasible sets.The centralized circumcentered-reection method is designed to solve the convex feasibility problem.Some numerical experiments demonstrate the feasibility and e ectiveness of the proposed algorithm,showing superior performance compared to conventional alternating projection methods.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金Project supported by the China Postdoctoral Science Foundation(Grant Nos.2015M580256 and 2016T90276)
文摘This paper discusses a statistical second-order two-scale（SSOTS） analysis and computation for a heat conduction problem with a radiation boundary condition in random porous materials.Firstly,the microscopic configuration for the structure with random distribution is briefly characterized.Secondly,the SSOTS formulae for computing the heat transfer problem are derived successively by means of the construction way for each cell.Then,the statistical prediction algorithm based on the proposed two-scale model is described in detail.Finally,some numerical experiments are proposed,which show that the SSOTS method developed in this paper is effective for predicting the heat transfer performance of porous materials and demonstrating its significant applications in actual engineering computation.
基金financially supported by the National Key R&D Program of China (No. 2017YFB0703100)the National Natural Science Foundation of China (NSFC) under Grant Nos. 51822103, 51671068 and 51731009the Fundamental Research Funds for the Central Universities (No. HIT.BRETIV.201902)
文摘The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.
基金funded by the National Key Research and Development Program(Grant No.2022YFC3004200)the National Key Research and Development Program of China(Grant No.2021YFB3900400)+1 种基金Hunan Provincial Natural Science Foundation of China(Grant No.2021JC0009)the National Natural Science Foundation of China(Grant No.U2142212).
文摘The Geometrical Optics(GO)approach and the FAST Emissivity Model(FASTEM)are widely used to estimate the surface radiative components in atmospheric radiative transfer simulations,but their applications are limited in specific conditions.In this study,a two-scale reflectivity model(TSRM)and a two-scale emissivity model(TSEM)are developed from the two-scale roughness theory.Unlike GO which only computes six non-zero elements in the reflectivity matrix,The TSRM includes 16 elements of Stokes reflectivity matrix which are important for improving radiative transfer simulation accuracy in a scattering atmosphere.It covers the frequency range from L-to W-bands.The dependences of all TSRM elements on zenith angle,wind speed,and frequency are derived and analyzed in details.For a set of downwelling radiances in microwave frequencies,the reflected upwelling brightness temperature(BTs)are calculated from both TSRM and GO and compared for analyzing their discrepancies.The TSRM not only includes the effects of GO but also accounts for the small-scale Bragg scattering effect in an order of several degrees in Kelvins in brightness temperature.Also,the third and fourth components of the Stokes vector can only be produced from the TSRM.For the emitted radiation,BT differences in vertical polarization between a TSEM and FASTEM are generally less than 5 K when the satellite zenith angle is less than 40°,whereas those for the horizontal component can be quite significant,greater than 20 K.
文摘A particle nonlinear two-scale kp-εp turbulence model is proposed for simulating the anisotropic turbulent two-phase flow. The particle kinetic energy equation for two-scale fluctuation, particle energy transfer rate equation for large-scale fluctuation, and particle turbulent kinetic energy dissipation rate equation for small-scale fluctuation are derived and closed. This model is used to simulate gas-particle flows in a sudden-expansion chamber. The simulation is com- pared with the experiment and with those obtained by using another two kinds of tow-phase turbulence model, such as the single-scale k-ε two-phase turbulence model and the particle two-scale second-order moment （USM） two-phase turbulence model. It is shown that the present model gives simulation in much better agreement with the experiment than the single-scale k-ε two-phase turbulence model does and is almost as good as the particle two-scale USM turbu-lence model.
基金The project supported by the Special Funds for Major State Basic Research,China(G-1999-0222-08)the Postdoctoral Science Foundation(2004036239)
文摘A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concepts of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision and through a unified treatment of these two kinds of fluctuations. The proposed model is used to simulate gas-particle flows in a channel and in a downer. Simulation results are in agreement with the experimental results reported in references and are near the results obtained using the sin- gle-scale second-order moment two-phase turbulence model superposed with a particle collision model （USM-θ model） in most regions.
基金Project supported by the National Natural Science Foundation of China(Grant No.11471262)the National Basic Research Program of China(Grant No.2012CB025904)the State Key Laboratory of Science and Engineering Computing and the Center for High Performance Computing of Northwestern Polytechnical University,China
文摘We study the hyperbolic–parabolic equations with rapidly oscillating coefficients. The formal second-order two-scale asymptotic expansion solutions are constructed by the multiscale asymptotic analysis. In addition, we theoretically explain the importance of the second-order two-scale solution by the error analysis in the pointwise sense. The associated explicit convergence rates are also obtained. Then a second-order two-scale numerical method based on the Newmark scheme is presented to solve the equations. Finally, some numerical examples are used to verify the effectiveness and efficiency of the multiscale numerical algorithm we proposed.
基金Project supported by the National Natural Science Foundation of China(Nos.12172233 and U1934201)。
文摘The dynamic vibration absorber with inerter and grounded stiffness(IGDVA)is used to control a two-scale system subject to a weak periodic perturbation.The vibration suppression effect is remarkable.The amplitude of the main system coupled with absorber is significantly reduced,and the high frequency vibration completely disappears.First,through the slow-fast analysis and stability theory,it is found that the stability of the autonomous system exerts a notable regulating effect on the vibration response of the non-autonomous system.After adding the dynamic vibrator absorber,the center in the autonomous system changes to an asymptotically stable focus,consequently suppressing the vibration in the non-autonomous system.Further research reveals that the parameters of the absorber affect the real parts of the eigenvalues of the autonomous system,thereby regulating the stability of the system.Transitioning from a qualitative standpoint to a quantitative approach,a comparison of the solutions before and after the introduction of the dynamic absorber reveals that,when the grounded stiffness ratio and the mass ratio of the dynamic absorber are not equal,the high-frequency part in the analytical solution disappears.As a result,this leads to a reduction in the amplitude of the trajectory,achieving a vibration reduction effect.
基金Project supported by China Post-Doctoral Science Foundation(No.2004036239)
文摘A two-scale second-order moment two-phase turbulence model accounting for inter-particle collision is developed, based on the concept of particle large-scale fluctuation due to turbulence and particle small-scale fluctuation due to collision. The proposed model is used to simulate gas-particle downer reactor flows. The computational results of both particle volume fraction and mean velocity are in agreement with the experimental results. After analyzing effects of empirical coefficient on prediction results, we can come to a conclusion that, inside the limit range of empirical coefficient, the predictions do not reveal a large sensitivity to the empirical coefficient in the downer reactor, but a relatively great change of the constants has important effect on the prediction.
