The mechanical behavior and progressive damage mechanism of novel aluminum matrix composites reinforced with 3D angle-interlock woven carbon fibers were investigated using a multiscale modeling approach.The mechanical...The mechanical behavior and progressive damage mechanism of novel aluminum matrix composites reinforced with 3D angle-interlock woven carbon fibers were investigated using a multiscale modeling approach.The mechanical properties and failure of yarns were evaluated using a microscale model under different loading scenarios.On this basis,a mesoscale model was developed to analyze the tensile behavior and failure mechanism of the composites.The interfacial decohesion,matrix damage,and failure of fibers and yarns were incorporated into the microscopic and mesoscopic models.The stress–strain curves and fracture modes from simulation show good agreement with the experimental curves and fracture morphology.Local interface and matrix damage initiate first under warp directional tension.Thereafter,interfacial failure,weft yarn cracking,and matrix failure occur successively.Axial fracture of warp yarn,which displays a quasi-ductile fracture characteristic,dominates the ultimate composites failure.Under weft directional tension,interfacial failure and warp yarn rupture occur at the early and middle stages.Matrix failure and weft yarn fracture emerge simultaneously at the final stage,leading to the cata-strophic failure of composites.The weft directional strength and fracture strain are lower than the warp directional ones because of the lower weft density and the more serious brittle fracture of weft yarns.展开更多
The cavitating flow in different regimes has the intricate flow structure with multiple time and space scales.The present work develops a multiscale model by coupling the volume of fluid(VOF)method and a discrete bubb...The cavitating flow in different regimes has the intricate flow structure with multiple time and space scales.The present work develops a multiscale model by coupling the volume of fluid(VOF)method and a discrete bubble model(DBM),to simulate the cavitating flow in a convergent-divergent test section.The Schnerr-Sauer cavitation model is used to calculate the mass transfer rate to obtain the macroscale phase structure,and the simplified Rayleigh-Plesset equation is applied to simulate the growing and collapsing of discrete bubbles.An algorithm for bridging between the macroscale cavities and microscale bubbles is also developed to achieve the multiscale simulation.For the flow field,the very large eddy simulation(VLES)approach is applied.Conditions from inception to sheet/cloud cavitation regimes are taken into account and simulations are conducted.Compared with the experimental observations,it is shown that the cavitation inception,bubble clouds formation and glass cavity generation are all well represented,indicating that the proposed VOF-DBM model is a promising approach to accurately and comprehensively reveal the multiscale phase field induced by cavitation.展开更多
A multiscale model was proposed to calculate the circumferential stress （CS） and wall shear stress （WSS） and analyze the effects of global and local factors on the CS, WSS and their synergy on the arterial endothe...A multiscale model was proposed to calculate the circumferential stress （CS） and wall shear stress （WSS） and analyze the effects of global and local factors on the CS, WSS and their synergy on the arterial endothelium in large straight arteries. A parameter pair [Zs, SPA] （defined as the ratio of CS amplitude to WSS amplitude and the phase angle between CS and WSS for different harmonic components, respectively） was proposed to characterize the synergy of CS and WSS. The results demonstrated that the CS or WSS in the large straight arteries is determined by the global factors, i.e. the preloads and the afterloads, and the local factors, i.e. the local mechanical properties and the zero-stress states of arterial walls, whereas the Zs and SPA are primarily determined by the local factors and the afterloads. Because the arterial input impedance has been shown to reflect the physiological and pathological states of whole downstream arterial beds, the stress amplitude ratio Zs and the stress phase difference SPA might be appropriate indices to reflect the influences of the states of whole downstream arterial beds on the local blood flow-dependent phenomena such as angiogenesis, vascular remodeling and atherosgenesis.展开更多
The increasingly harsh environment of the nuclear reactors and the insurmountableflaws of in-service materials have created an urgent need for the development of the brand-new alloys.For last decade,the high-entropy al...The increasingly harsh environment of the nuclear reactors and the insurmountableflaws of in-service materials have created an urgent need for the development of the brand-new alloys.For last decade,the high-entropy alloys(HEAs),a novel composition-design strategy,have received much attention due to their promise for the nuclearfields.The application of the multiscale modelling is to explore the irradiation performance and underlying mechanisms of HEAs.Abundant results and data deepen the understanding of the irradiation response,and accelerate the development of advanced irradiation-resistant HEAs.This review introduces the state-of-art multiscale modelling used for studying the irradiated properties of HEAs.Representative irradiation-induced microstructures and properties,as well as damage,are summarized.By strengthening the application of multiscale modelling,a rational design of high irradiation-resistant HEAs is expected.展开更多
In this paper,a multiscale model is developed for the mass functionally graded(FG)beam-fluid system to investigate its static and dynamic responses based on 3D printed porous beam free vibration tests,which are determ...In this paper,a multiscale model is developed for the mass functionally graded(FG)beam-fluid system to investigate its static and dynamic responses based on 3D printed porous beam free vibration tests,which are determined by two aspects.At the microstructural level,the gradient variation is realized by arbitrary distribution of matrix pores,and the effective moduli under specific distribution are obtained using the micromechanics homogenization theory.In the meantime,at the structural level,the mechanical responses of FG porous beams subjected to mass loading are considered in a static fluid environment.Then,the explicit expressions of local finite-element(FE)expressions corresponding to the static and dynamic responses are given in the appendices.The present results are validated against numerical and experimental results from the literature and mechanical tests of 3D printed structures,with good agreement generally obtained,giving credence to the present model.On this basis,a comprehensive parametric study is carried out,with a particular focus on the effects of boundary conditions,fluid density,and slenderness ratio on the bending and vibration of FG beams with several different gradations.展开更多
Three different multiscale models, based on the method of cells(generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the ...Three different multiscale models, based on the method of cells(generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the following multiscale modeling strategies were employed: Concurrent modeling of all phases using the generalized method of cells, synergistic(two-way coupling in space) multiscale modeling with the generalized method of cells, and hierarchical(one-way coupling in space) multiscale modeling with the high fidelity generalized method of cells. The three models are validated against data from a hierarchical multiscale finite element model in the literature for a repeating unit cell of C/C-SiC.Furthermore, the multiscale models are used in conjunction with classical lamination theory to predict the stiffness of C/C-SiC plates manufactured via a wet filament winding and liquid silicon infiltration process recently developed by the German Aerospace Institute. Finally, un-reacted Si(or free Si) and porosity in the C matrix are included in the multiscale model, and the effect of these new phases on the stiffness and local stresses are considered.展开更多
The high temperature dielectrics of Quartz fiber-reinforced silicon dioxide ceramic （Si02/SiO2 ） composites were studied both theoretically and experimentally. A multi-scale theoretical model was developed based on ...The high temperature dielectrics of Quartz fiber-reinforced silicon dioxide ceramic （Si02/SiO2 ） composites were studied both theoretically and experimentally. A multi-scale theoretical model was developed based on the theory of dielectrics. It was realized to predict dielectric properties at higher temperature （ 〉 1200 ℃） by experimental data mining for correlative coefficients in model. The results show that the dielectrics of SiO2/SiO2, which were calculated with the theoretical model, were in agreement with experimental measured value.展开更多
To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering ...To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering method is a kind of unsupervised machine learning method,the elements with similar mechanical behavior under external loading can be included in a cluster automatically at the microscale.With this modification,the fiber random distribution model can be used for multiscale damage analysis in the framework of MMF theory.To validate the modified multiscale analysis method,progressive damage analysis of a kind of 2D twill woven composites is conducted based on different microscale models.The stress values for microscale models with fiber hexagonal and random distribution patterns are compared first.Much higher stress concentration is generated in the fiber random distribution model due to the smaller inter-fiber distance especially under longitudinal shear loading.The obtained cluster distribution results exhibit the characters of the stress distribution in the two microscale models.Thereafter,tensile and compressive responses of the 2D twill woven composite are predicted with the modified multiscale analysis method and accuracy of the method is verified through comparison with published experimental results.From the simulation results,it can be found that the matrix damage initiation from the model based on the fiber random distribution model is premature compared with that from the model based on the fiber hexagonal distribution model.Besides,under tensile loading,the damage all initiates from the fill tows and propagates to the wrap tows.However,under compressive loading,the matrix damage initiates from the wrap tows in the model based on the fiber random distribution model.展开更多
Plasma-surface interactions(PSI)play a crucial role in microelectronics fabrication;however,their multiscale nature and array of complex,often unknown interactions make computationalmodeling of PSIs extremely difficul...Plasma-surface interactions(PSI)play a crucial role in microelectronics fabrication;however,their multiscale nature and array of complex,often unknown interactions make computationalmodeling of PSIs extremely difficult.To this end,we propose a general neural master equation(NME)framework that uses master equations to describe the dynamics of a molecular process,wherein neural networks learned from atomistic simulations represent unknown transitions between different systemstates.By leveraging the physics-based structure of master equations and data-driven state transitions,the NME framework promotes generalizability and physics interpretability,and can bridge disparate length and time scales.The framework is demonstrated for multiscale modeling of Si atomic layer etching and reactive ion etching,where the learned NME-based surface kinetic models exhibit good predictive and extrapolative capabilities for predicting experimentally relevant observables as a function of process parameters.The NME-based surface kinetic models obey physical constraints,which are violated in models based on neural ordinary differential equations.The proposed NME framework for multiscale modeling of molecular processes can pave the way for the discovery of new chemistries and materials in atomic-scale plasma processes.展开更多
Propeller cavity bursting,triggered by the sharp hull wake,can significantly increase broadband noise.However,its complex multiscale nature presents substantial challenges for numerical simulations,limiting the predic...Propeller cavity bursting,triggered by the sharp hull wake,can significantly increase broadband noise.However,its complex multiscale nature presents substantial challenges for numerical simulations,limiting the prediction accuracy for propeller cavitation noise to only the first few blade-passing frequencies.To overcome this limitation,this study explores the potential of a novel Euler-Lagrange hybrid model for simulating cavity bursting and the resulting broadband noise.Focused on a benchmark test case of the INSEAN E779A propeller,the numerical results effectively reproduce the measured cavity bursting and its associated broadband pressure fluctuations,providing valuable insights for realistic simulations of propeller cavitation noise.展开更多
Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock st...Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock structural degradation.This may lead to problems in the evaluation of rock structure stability and safe life.Multiscale numerical modeling is regarded as an effective way to gain insight into factors affecting rock properties from a cross-scale view.This study compiles the history of theoretical developments and numerical techniques related to rock multiscale issues according to different modeling architectures,that is,the homogenization theory,the hierarchical approach,and the concurrent approach.For these approaches,their benefits,drawbacks,and application scope are underlined.Despite the considerable attempts that have been made,some key issues still result in multiple challenges.Therefore,this study points out the perspectives of rock multiscale issues so as to provide a research direction for the future.The review results show that,in addition to numerical techniques,for example,high-performance computing,more attention should be paid to the development of an advanced constitutive model with consideration of fine geometrical descriptions of rock to facilitate solutions to multiscale problems in rock mechanics and rock engineering.展开更多
Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational f...Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational framework combining on-lattice kinetic Monte Carlo(KMC)simulations,absorbing Markov chain models,and mesoscale cluster dynamics(CD)to investigate these interactions in Al-Mg-Zn alloys.The Markov chain model yields vacancy escape times from solute clusters and identifies a two-stage behavior of the vacancy-cluster binding energy.These binding energies are used to estimate residual vacancy concentrations in the Al matrix after quenching,which serve as critical inputs to CD simulations to predict long-term cluster evolution kinetics during natural aging.Our results quantitatively demonstrate the significant impact of quench rate on natural aging kinetics.Results provide insights to guide alloy chemistry,quench rates,and aging time at finite temperatures to control the evolution of solute clusters and eventual precipitates in aged multicomponent alloys.展开更多
Acidic electrochemical CO_(2) reduction(CO_(2) RR)mitigates CO_(2) loss and energy inefficiencies but suffers from limited selectivity.Insufficient understanding of the interfacial microenvironment and cation specific...Acidic electrochemical CO_(2) reduction(CO_(2) RR)mitigates CO_(2) loss and energy inefficiencies but suffers from limited selectivity.Insufficient understanding of the interfacial microenvironment and cation specificity hinders the development of efficient interfacial design methods.Here,we integrate ab initio-derived reaction kinetics with mass transfer modeling into a multiscale framework that reproduces the bell-shaped Faradaic efficiency profile inaccessible to the Butler-Volmer equations.Our results emphasize the role of hydrogen bonding in CO_(2) activation and reveal a potential-dependent shift in the rate-determining steps.We also demonstrate that cations inhibit competing hydrogen evolution by strengthening the interfacial electric field and disrupting the hydrogen-bond network.However,their accumulation near the outer Helmholtz plane induces strong steric effects,impeding CO_(2) supply.Furthermore,the parametric analysis highlights the critical role of strategies such as pressurization and pore-confined electrolyte control in overcoming interfacial CO_(2) transport limitations,enhancing selectivity,and broadening the operating potential window.This work advances a multiscale perspective on interfacial mass transfer and cation effects,establishing a unified framework for reaction interface design in acidic CO_(2) RR.展开更多
A multiscale nonlocal continuum model is proposed to describe the superelastic deformation of gradient nano-grained NiTi shape memory alloys(SMAs).At the mesoscopic scale,the polycrystalline aggregate is regarded as a...A multiscale nonlocal continuum model is proposed to describe the superelastic deformation of gradient nano-grained NiTi shape memory alloys(SMAs).At the mesoscopic scale,the polycrystalline aggregate is regarded as a composite,i.e.,the graininterior(GI)phase is assumed to be a cuboidal inclusion embedded in a matrix of grain-boundary(GB)phase.An intrinsic energetic length and a gradient energy are introduced into the Helmholtz free energy of the GI phase.The criterion of martensite transformation(MT)is derived based on the principle of virtual power and second law of thermodynamics.The hindering effect of GB on MT in GI phase is addressed.By deriving the analytical solution of the proposed model and introducing a scale transition rule,the overall and local stress-strain responses of the specimen at the macroscopic scale are obtained.The prediction capability of the proposed model is verified by comparing the analytical solution with the experiment.The influences of the distribution form for the grain size(GS)on the superelastic deformation of gradient nano-grained NiTi SMAs are further predicted and discussed.The analytical form and low computational cost of the proposed model make it an appropriate theoretical tool to design the gradient nano-grained SMAs with desired mechanical property.展开更多
Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to...Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to determine the mechanical properties of material if the macroscopic mechanical properties of linear elastic solids are derived from the microscopic level. Enlightened by this idea, a multiscale mechanical model for material, the virtual multi-dimensional internal bonds （VMIB） model, is proposed by incorporating a shear bond into the virtual internal bond （VIB） model. By this modification, the VMIB model associates the macro mechanical properties of material with the microscopic mechanical properties of discrete structure and the corresponding relationship between micro and macro parameters is derived. The tensor quality of the energy density function, which contains coordinate vector, is mathematically proved. From the point of view of VMIB, the macroscopic nonlinear behaviors of material could be attributed to the evolution of virtual bond distribution density induced by the imposed deformation. With this theoretical hypothesis, as an application example, a uniaxial compressive failure of brittle material is simulated. Good agreement between the experimental results and the simulated ones is found.展开更多
The financial market volatility forecasting is regarded as a challenging task because of irreg ularity, high fluctuation, and noise. In this study, a multiscale ensemble forecasting model is proposed. The original fin...The financial market volatility forecasting is regarded as a challenging task because of irreg ularity, high fluctuation, and noise. In this study, a multiscale ensemble forecasting model is proposed. The original financial series are decomposed firstly different scale components （i.e., approximation and details） using the maximum overlap discrete wavelet transform （MODWT）. The approximation is pre- dicted by a hybrid forecasting model that combines autoregressive integrated moving average （ARIMA） with feedforward neural network （FNN）. ARIMA model is used to generate a linear forecast, and then FNN is developed as a tool for nonlinear pattern recognition to correct the estimation error in ARIMA forecast. Moreover, details are predicted by Elman neural networks. Three weekly exchange rates data are collected to establish and validate the forecasting model. Empirical results demonstrate consistent better performance of the proposed approach.展开更多
In this study,the micro curing residual stresses of carbon fiber-reinforced thermoset polymer(CFRP)composites are evaluated using a multiscale modeling method.A thermochemical coupling model is developed at the macros...In this study,the micro curing residual stresses of carbon fiber-reinforced thermoset polymer(CFRP)composites are evaluated using a multiscale modeling method.A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure.Meanwhile,a representative volume element model of the composites is established at the microscale level.By introducing the information from the macroscale perspective,the curing residual stresses are calculated using the microscale model.The evolution of curing residual stresses reveals the interaction mechanism of fiber,matrix,and interphase period during the curing process.Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber.Furthermore,the curing residual stresses at different locations in the composites are calculated and discussed.Simulation results provide an important guideline for the analysis and design of CFRP composite structures.展开更多
This paper introduced a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of c...This paper introduced a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of cement paste was investigated, in which three kinds of admixtures were taken into account including viscosity modifying admixture （VMA）, silica.fume （SF）, and shrinkage-reducing admixture （SRA）. The experimental results indicate that the dynamic elastic modulus of cement paste increases with decreasing water-cement ratio. The addition of SF increases the dynamic elastic modulus, however, the overdosage of VMA causes its reduction. SRA reduces the dynamic elastic modulus at early age without affecting it in later period. Finally, a multiscale micromechanics approach coupled with a hydration model CEMHYD3D and percolation theory is utilized to predict the elastic modulus of cement paste, and the predictive results by the model are in accordance with the experimental data.展开更多
DNA nanotubes(DNTs)with user-defined shapes and functionalities have potential applications in many fields.So far,compared with numerous experimental studies,there have been only a handful of models on the mechanical ...DNA nanotubes(DNTs)with user-defined shapes and functionalities have potential applications in many fields.So far,compared with numerous experimental studies,there have been only a handful of models on the mechanical properties of such DNTs.This paper aims at presenting a multiscale model to quantify the correlations among the pre-tension states,tensile properties,encapsulation structures of DNTs,and the surrounding factors.First,by combining a statistical worm-like-chain(WLC)model of single DNA deformation and Parsegian's mesoscopic model of DNA liquid crystal free energy,a multiscale tensegrity model is established,and the pre-tension state of DNTs is characterized theoretically for the first time.Then,by using the minimum potential energy principle,the force-extension curve and tensile rigidity of pre-tension DNTs are predicted.Finally,the effects of the encapsulation structure and surrounding factors on the tensile properties of DNTs are studied.The predictions for the tensile behaviors of DNTs can not only reproduce the existing experimental results,but also reveal that the competition of DNA intrachain and interchain interactions in the encapsulation structures determines the pre-tension states of DNTs and their tensile properties.The changes in the pre-tension states and environmental factors make the monotonic or non-monotonic changes in the tensile properties of DNTs under longitudinal loads.展开更多
Vegetation constitutes one of the fundamental types of land use on Earth.The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments,thus exert...Vegetation constitutes one of the fundamental types of land use on Earth.The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments,thus exerting notable influences on the urban microenvironment.A better understanding of the turbulent transfer of momentum and scalars around vegetation canopy could significantly contribute to improvement of the urban environment.This work develops a large-eddy simulation(LES)method that is applicable to model the flow and scalar transport over the forest canopy.We study the atmospheric flow over complex forested areas under typical weather conditions by coupling LES to the mesoscale model.Models of radiation and energy balance have been developed with explicit treatment of the vegetation canopy.By examining the flow over a forest canopy under a range of stability conditions,we found that buoyancy enhances or suppresses turbulent mixing in unstable or stable atmosphere respectively,with decreasing or increasing wind shear,respectively.From the multiscale modeling of the Beijing Olympic Forest Park,the present coupling scheme proves to better resolve the diurnal variations in wind speed,temperature,and relative humidity over complex urban terrains.The coupling scheme is superior to the traditional mesoscale model in terms of wind field simulation.This is mainly because the coupling scheme not only takes the influences of external mesoscale flow into consideration,but also resolves the heterogeneous urban surface at a fine scale by downscaling,thus better reproducing the complex flow and turbulent transport in the urban roughness sublayer.展开更多
基金co-supported by the National Natural Science Foundation of China(Nos.51765045 and 51365043)the Aeronautical Science Foundation of China(No.2019ZF056013)the Jiangxi Provincial Natural Science Foundation(No.20202ACBL204010)。
文摘The mechanical behavior and progressive damage mechanism of novel aluminum matrix composites reinforced with 3D angle-interlock woven carbon fibers were investigated using a multiscale modeling approach.The mechanical properties and failure of yarns were evaluated using a microscale model under different loading scenarios.On this basis,a mesoscale model was developed to analyze the tensile behavior and failure mechanism of the composites.The interfacial decohesion,matrix damage,and failure of fibers and yarns were incorporated into the microscopic and mesoscopic models.The stress–strain curves and fracture modes from simulation show good agreement with the experimental curves and fracture morphology.Local interface and matrix damage initiate first under warp directional tension.Thereafter,interfacial failure,weft yarn cracking,and matrix failure occur successively.Axial fracture of warp yarn,which displays a quasi-ductile fracture characteristic,dominates the ultimate composites failure.Under weft directional tension,interfacial failure and warp yarn rupture occur at the early and middle stages.Matrix failure and weft yarn fracture emerge simultaneously at the final stage,leading to the cata-strophic failure of composites.The weft directional strength and fracture strain are lower than the warp directional ones because of the lower weft density and the more serious brittle fracture of weft yarns.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52006197 and 51676174)the Natural Science Foundation of Jiangsu Province(Grant No.BK20180505)+1 种基金the National Science Foundation of Zhejiang Province(Grant Nos.LQ21E060012 and LR20E090001)the Key Research and Development Program of Zhejiang Province(Grant No.2020C01027)。
文摘The cavitating flow in different regimes has the intricate flow structure with multiple time and space scales.The present work develops a multiscale model by coupling the volume of fluid(VOF)method and a discrete bubble model(DBM),to simulate the cavitating flow in a convergent-divergent test section.The Schnerr-Sauer cavitation model is used to calculate the mass transfer rate to obtain the macroscale phase structure,and the simplified Rayleigh-Plesset equation is applied to simulate the growing and collapsing of discrete bubbles.An algorithm for bridging between the macroscale cavities and microscale bubbles is also developed to achieve the multiscale simulation.For the flow field,the very large eddy simulation(VLES)approach is applied.Conditions from inception to sheet/cloud cavitation regimes are taken into account and simulations are conducted.Compared with the experimental observations,it is shown that the cavitation inception,bubble clouds formation and glass cavity generation are all well represented,indicating that the proposed VOF-DBM model is a promising approach to accurately and comprehensively reveal the multiscale phase field induced by cavitation.
基金The project supported by the National Natural Science Foundation of China (10132020 and 10472027)The English text was polished by Yunming Chen.
文摘A multiscale model was proposed to calculate the circumferential stress （CS） and wall shear stress （WSS） and analyze the effects of global and local factors on the CS, WSS and their synergy on the arterial endothelium in large straight arteries. A parameter pair [Zs, SPA] （defined as the ratio of CS amplitude to WSS amplitude and the phase angle between CS and WSS for different harmonic components, respectively） was proposed to characterize the synergy of CS and WSS. The results demonstrated that the CS or WSS in the large straight arteries is determined by the global factors, i.e. the preloads and the afterloads, and the local factors, i.e. the local mechanical properties and the zero-stress states of arterial walls, whereas the Zs and SPA are primarily determined by the local factors and the afterloads. Because the arterial input impedance has been shown to reflect the physiological and pathological states of whole downstream arterial beds, the stress amplitude ratio Zs and the stress phase difference SPA might be appropriate indices to reflect the influences of the states of whole downstream arterial beds on the local blood flow-dependent phenomena such as angiogenesis, vascular remodeling and atherosgenesis.
基金appreciate the supports from National Natural Science Foundation of China(U2267252,12172123,and 12072109)Natural Science Foundation of Hunan Province(2022JJ20001 and 2021JJ40032)+2 种基金The science and technology innovation Program of Hunan Province(2022RC1200)Natural Science Foundation of Changsha City(kq2202139)the support from the National Science Foundation(DMR-1611180 and 1809640).
文摘The increasingly harsh environment of the nuclear reactors and the insurmountableflaws of in-service materials have created an urgent need for the development of the brand-new alloys.For last decade,the high-entropy alloys(HEAs),a novel composition-design strategy,have received much attention due to their promise for the nuclearfields.The application of the multiscale modelling is to explore the irradiation performance and underlying mechanisms of HEAs.Abundant results and data deepen the understanding of the irradiation response,and accelerate the development of advanced irradiation-resistant HEAs.This review introduces the state-of-art multiscale modelling used for studying the irradiated properties of HEAs.Representative irradiation-induced microstructures and properties,as well as damage,are summarized.By strengthening the application of multiscale modelling,a rational design of high irradiation-resistant HEAs is expected.
基金supported by the National Key Research and Development Program of China(No.2020YFA0711700)the National Natural Science Foundation of China(No.12322206,No.52378158,No.12302205)ZJU-ZCCC Institute of Collaborative Innovation(No.ZDJG2021002).
文摘In this paper,a multiscale model is developed for the mass functionally graded(FG)beam-fluid system to investigate its static and dynamic responses based on 3D printed porous beam free vibration tests,which are determined by two aspects.At the microstructural level,the gradient variation is realized by arbitrary distribution of matrix pores,and the effective moduli under specific distribution are obtained using the micromechanics homogenization theory.In the meantime,at the structural level,the mechanical responses of FG porous beams subjected to mass loading are considered in a static fluid environment.Then,the explicit expressions of local finite-element(FE)expressions corresponding to the static and dynamic responses are given in the appendices.The present results are validated against numerical and experimental results from the literature and mechanical tests of 3D printed structures,with good agreement generally obtained,giving credence to the present model.On this basis,a comprehensive parametric study is carried out,with a particular focus on the effects of boundary conditions,fluid density,and slenderness ratio on the bending and vibration of FG beams with several different gradations.
基金NASA’s Transformational Tools and Technologies (TTT)the Theodore von Kármán Fellowship (GS069)+3 种基金the Theodore von Kármán Fellowship (GS069)the Alexander von Humboldt Fellowship for funding this workthe support of the Ministry of Innovation, Science, and Research of the state of North RhineWestphaliaprovided by the German Research Foundation (DFG) in the framework of CRC/Transregio 40 ‘Fundamental Technologies for the Development of Future Space-Transport-System Components under High Thermal and Mechanical Loads’ (TPD3)
文摘Three different multiscale models, based on the method of cells(generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the following multiscale modeling strategies were employed: Concurrent modeling of all phases using the generalized method of cells, synergistic(two-way coupling in space) multiscale modeling with the generalized method of cells, and hierarchical(one-way coupling in space) multiscale modeling with the high fidelity generalized method of cells. The three models are validated against data from a hierarchical multiscale finite element model in the literature for a repeating unit cell of C/C-SiC.Furthermore, the multiscale models are used in conjunction with classical lamination theory to predict the stiffness of C/C-SiC plates manufactured via a wet filament winding and liquid silicon infiltration process recently developed by the German Aerospace Institute. Finally, un-reacted Si(or free Si) and porosity in the C matrix are included in the multiscale model, and the effect of these new phases on the stiffness and local stresses are considered.
基金the National Defense 973 (Grant No.513180303) and National Defense Basic Scientific Research (Grant No. A2220061080)the Na-tional Defense Foundation (Grant No. 5142040205BQ0154).
文摘The high temperature dielectrics of Quartz fiber-reinforced silicon dioxide ceramic （Si02/SiO2 ） composites were studied both theoretically and experimentally. A multi-scale theoretical model was developed based on the theory of dielectrics. It was realized to predict dielectric properties at higher temperature （ 〉 1200 ℃） by experimental data mining for correlative coefficients in model. The results show that the dielectrics of SiO2/SiO2, which were calculated with the theoretical model, were in agreement with experimental measured value.
基金the support of the National Natural Science Foundation of China(No.11572086)the Fundamental Research Funds for the Central Universities+2 种基金the Scientific Research Innovation Program of Jiangsu Province College of China(No.KYLX16_0185)the Scientific Research Foundation of Graduate School of Southeast University of China(No.YBJJ1760)the China Scholarship Council of China(No.201706090076)。
文摘To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering method is a kind of unsupervised machine learning method,the elements with similar mechanical behavior under external loading can be included in a cluster automatically at the microscale.With this modification,the fiber random distribution model can be used for multiscale damage analysis in the framework of MMF theory.To validate the modified multiscale analysis method,progressive damage analysis of a kind of 2D twill woven composites is conducted based on different microscale models.The stress values for microscale models with fiber hexagonal and random distribution patterns are compared first.Much higher stress concentration is generated in the fiber random distribution model due to the smaller inter-fiber distance especially under longitudinal shear loading.The obtained cluster distribution results exhibit the characters of the stress distribution in the two microscale models.Thereafter,tensile and compressive responses of the 2D twill woven composite are predicted with the modified multiscale analysis method and accuracy of the method is verified through comparison with published experimental results.From the simulation results,it can be found that the matrix damage initiation from the model based on the fiber random distribution model is premature compared with that from the model based on the fiber hexagonal distribution model.Besides,under tensile loading,the damage all initiates from the fill tows and propagates to the wrap tows.However,under compressive loading,the matrix damage initiates from the wrap tows in the model based on the fiber random distribution model.
基金supported in part by the U.S.Department of Energy,Office of Science,Office of Fusion Energy Sciences under Award No.DE-SC0024472 and Award No.DE-SC0024474.
文摘Plasma-surface interactions(PSI)play a crucial role in microelectronics fabrication;however,their multiscale nature and array of complex,often unknown interactions make computationalmodeling of PSIs extremely difficult.To this end,we propose a general neural master equation(NME)framework that uses master equations to describe the dynamics of a molecular process,wherein neural networks learned from atomistic simulations represent unknown transitions between different systemstates.By leveraging the physics-based structure of master equations and data-driven state transitions,the NME framework promotes generalizability and physics interpretability,and can bridge disparate length and time scales.The framework is demonstrated for multiscale modeling of Si atomic layer etching and reactive ion etching,where the learned NME-based surface kinetic models exhibit good predictive and extrapolative capabilities for predicting experimentally relevant observables as a function of process parameters.The NME-based surface kinetic models obey physical constraints,which are violated in models based on neural ordinary differential equations.The proposed NME framework for multiscale modeling of molecular processes can pave the way for the discovery of new chemistries and materials in atomic-scale plasma processes.
基金supported by the National Natural Science Foundation of China(Project Nos.52479085 and 123B2032).
文摘Propeller cavity bursting,triggered by the sharp hull wake,can significantly increase broadband noise.However,its complex multiscale nature presents substantial challenges for numerical simulations,limiting the prediction accuracy for propeller cavitation noise to only the first few blade-passing frequencies.To overcome this limitation,this study explores the potential of a novel Euler-Lagrange hybrid model for simulating cavity bursting and the resulting broadband noise.Focused on a benchmark test case of the INSEAN E779A propeller,the numerical results effectively reproduce the measured cavity bursting and its associated broadband pressure fluctuations,providing valuable insights for realistic simulations of propeller cavitation noise.
基金National Natural Science Foundation of China,Grant/Award Numbers:52192691,52192690。
文摘Rock is geometrically and mechanically multiscale in nature,and the traditional phenomenological laws at the macroscale cannot render a quantitative relationship between microscopic damage of rocks and overall rock structural degradation.This may lead to problems in the evaluation of rock structure stability and safe life.Multiscale numerical modeling is regarded as an effective way to gain insight into factors affecting rock properties from a cross-scale view.This study compiles the history of theoretical developments and numerical techniques related to rock multiscale issues according to different modeling architectures,that is,the homogenization theory,the hierarchical approach,and the concurrent approach.For these approaches,their benefits,drawbacks,and application scope are underlined.Despite the considerable attempts that have been made,some key issues still result in multiple challenges.Therefore,this study points out the perspectives of rock multiscale issues so as to provide a research direction for the future.The review results show that,in addition to numerical techniques,for example,high-performance computing,more attention should be paid to the development of an advanced constitutive model with consideration of fine geometrical descriptions of rock to facilitate solutions to multiscale problems in rock mechanics and rock engineering.
基金supported by NSF grant#1905421with computing resources provided by GM Global Technical Center and Stampede3 at TACC(ACCESS allocation DMR190035,NSF grants#2138259,#2138286,#2138307,#2137603,#2138296).The authors thank Prof.Dane Morgan from the University of Wisconsin-Madison for insightful discussions.
文摘Prediction of solute clustering kinetics in aged multicomponent alloys requires a quantitative understanding of complex vacancy-cluster interactions across multiple scales.Here,we develop an integrated computational framework combining on-lattice kinetic Monte Carlo(KMC)simulations,absorbing Markov chain models,and mesoscale cluster dynamics(CD)to investigate these interactions in Al-Mg-Zn alloys.The Markov chain model yields vacancy escape times from solute clusters and identifies a two-stage behavior of the vacancy-cluster binding energy.These binding energies are used to estimate residual vacancy concentrations in the Al matrix after quenching,which serve as critical inputs to CD simulations to predict long-term cluster evolution kinetics during natural aging.Our results quantitatively demonstrate the significant impact of quench rate on natural aging kinetics.Results provide insights to guide alloy chemistry,quench rates,and aging time at finite temperatures to control the evolution of solute clusters and eventual precipitates in aged multicomponent alloys.
基金supported by the National Natural Science Foundation of China(52394202 and 52476056)key project of the Joint Fund for Innovation and Development of Chongqing Natural Science Foundation(CSTB2022NSCQ-LZX0013)+1 种基金the Innovative Research Group Project of the National Natural Science Foundation of China(52021004)the Natural Science Foundation of Chongqing,China(CSTB2024NSCQ-MSX0915).
文摘Acidic electrochemical CO_(2) reduction(CO_(2) RR)mitigates CO_(2) loss and energy inefficiencies but suffers from limited selectivity.Insufficient understanding of the interfacial microenvironment and cation specificity hinders the development of efficient interfacial design methods.Here,we integrate ab initio-derived reaction kinetics with mass transfer modeling into a multiscale framework that reproduces the bell-shaped Faradaic efficiency profile inaccessible to the Butler-Volmer equations.Our results emphasize the role of hydrogen bonding in CO_(2) activation and reveal a potential-dependent shift in the rate-determining steps.We also demonstrate that cations inhibit competing hydrogen evolution by strengthening the interfacial electric field and disrupting the hydrogen-bond network.However,their accumulation near the outer Helmholtz plane induces strong steric effects,impeding CO_(2) supply.Furthermore,the parametric analysis highlights the critical role of strategies such as pressurization and pore-confined electrolyte control in overcoming interfacial CO_(2) transport limitations,enhancing selectivity,and broadening the operating potential window.This work advances a multiscale perspective on interfacial mass transfer and cation effects,establishing a unified framework for reaction interface design in acidic CO_(2) RR.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.12072296,12322203 and 12202294)Sichuan Science and Technology Program(Grant No.2024NSFSC1346)are greatly appreciated。
文摘A multiscale nonlocal continuum model is proposed to describe the superelastic deformation of gradient nano-grained NiTi shape memory alloys(SMAs).At the mesoscopic scale,the polycrystalline aggregate is regarded as a composite,i.e.,the graininterior(GI)phase is assumed to be a cuboidal inclusion embedded in a matrix of grain-boundary(GB)phase.An intrinsic energetic length and a gradient energy are introduced into the Helmholtz free energy of the GI phase.The criterion of martensite transformation(MT)is derived based on the principle of virtual power and second law of thermodynamics.The hindering effect of GB on MT in GI phase is addressed.By deriving the analytical solution of the proposed model and introducing a scale transition rule,the overall and local stress-strain responses of the specimen at the macroscopic scale are obtained.The prediction capability of the proposed model is verified by comparing the analytical solution with the experiment.The influences of the distribution form for the grain size(GS)on the superelastic deformation of gradient nano-grained NiTi SMAs are further predicted and discussed.The analytical form and low computational cost of the proposed model make it an appropriate theoretical tool to design the gradient nano-grained SMAs with desired mechanical property.
基金Project supported by the National Basic Research Program of China (973 Project) (No. 2002CB412704).
文摘Only two macroscopic parameters are needed to describe the mechanical properties of linear elastic solids, i.e. the Poisson＇s ratio and Young＇s modulus. Correspondingly, there should be two microscopic parameters to determine the mechanical properties of material if the macroscopic mechanical properties of linear elastic solids are derived from the microscopic level. Enlightened by this idea, a multiscale mechanical model for material, the virtual multi-dimensional internal bonds （VMIB） model, is proposed by incorporating a shear bond into the virtual internal bond （VIB） model. By this modification, the VMIB model associates the macro mechanical properties of material with the microscopic mechanical properties of discrete structure and the corresponding relationship between micro and macro parameters is derived. The tensor quality of the energy density function, which contains coordinate vector, is mathematically proved. From the point of view of VMIB, the macroscopic nonlinear behaviors of material could be attributed to the evolution of virtual bond distribution density induced by the imposed deformation. With this theoretical hypothesis, as an application example, a uniaxial compressive failure of brittle material is simulated. Good agreement between the experimental results and the simulated ones is found.
基金supported by the Humanities and Social Sciences Youth Foundation of the Ministry of Education of PR of China under Grant No.11YJC870028the Selfdetermined Research Funds of CCNU from the Colleges’Basic Research and Operation of MOE under Grant No.CCNU13F030+1 种基金China Postdoctoral Science Foundation under Grant No.2013M530753National Science Foundation of China under Grant No.71390335
文摘The financial market volatility forecasting is regarded as a challenging task because of irreg ularity, high fluctuation, and noise. In this study, a multiscale ensemble forecasting model is proposed. The original financial series are decomposed firstly different scale components （i.e., approximation and details） using the maximum overlap discrete wavelet transform （MODWT）. The approximation is pre- dicted by a hybrid forecasting model that combines autoregressive integrated moving average （ARIMA） with feedforward neural network （FNN）. ARIMA model is used to generate a linear forecast, and then FNN is developed as a tool for nonlinear pattern recognition to correct the estimation error in ARIMA forecast. Moreover, details are predicted by Elman neural networks. Three weekly exchange rates data are collected to establish and validate the forecasting model. Empirical results demonstrate consistent better performance of the proposed approach.
基金Supported by the National Key Research and Development Program of China(Grant No.2017YFB1102800)the National Natural Science Foundation of China(Grant Nos.11872310 and 51761145111).
文摘In this study,the micro curing residual stresses of carbon fiber-reinforced thermoset polymer(CFRP)composites are evaluated using a multiscale modeling method.A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure.Meanwhile,a representative volume element model of the composites is established at the microscale level.By introducing the information from the macroscale perspective,the curing residual stresses are calculated using the microscale model.The evolution of curing residual stresses reveals the interaction mechanism of fiber,matrix,and interphase period during the curing process.Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber.Furthermore,the curing residual stresses at different locations in the composites are calculated and discussed.Simulation results provide an important guideline for the analysis and design of CFRP composite structures.
基金Funded by the National Natural Science Foundation of China(No.51309090)the National Science Foundation for Postdoctoral Scientists of China(No.2013M531268)the Jiangsu Planned Projects for Postdoctoral Research Funds(No.1302101C)
文摘This paper introduced a nondestructive testing method to evaluate the dynamic elastic modulus of cement paste. Moreover, the effect of water-cement ratio and conventional admixtures on the dynamic elastic modulus of cement paste was investigated, in which three kinds of admixtures were taken into account including viscosity modifying admixture （VMA）, silica.fume （SF）, and shrinkage-reducing admixture （SRA）. The experimental results indicate that the dynamic elastic modulus of cement paste increases with decreasing water-cement ratio. The addition of SF increases the dynamic elastic modulus, however, the overdosage of VMA causes its reduction. SRA reduces the dynamic elastic modulus at early age without affecting it in later period. Finally, a multiscale micromechanics approach coupled with a hydration model CEMHYD3D and percolation theory is utilized to predict the elastic modulus of cement paste, and the predictive results by the model are in accordance with the experimental data.
基金Project supported by the National Natural Science Foundation of China(Nos.12172204,11772182,11272193,and 10872121)the Program of Shanghai Municipal Education Commission(No.2019-01-07-00-09-E00018)the Natural Science Foundation of Shanghai of China(No.22Z00142)。
文摘DNA nanotubes(DNTs)with user-defined shapes and functionalities have potential applications in many fields.So far,compared with numerous experimental studies,there have been only a handful of models on the mechanical properties of such DNTs.This paper aims at presenting a multiscale model to quantify the correlations among the pre-tension states,tensile properties,encapsulation structures of DNTs,and the surrounding factors.First,by combining a statistical worm-like-chain(WLC)model of single DNA deformation and Parsegian's mesoscopic model of DNA liquid crystal free energy,a multiscale tensegrity model is established,and the pre-tension state of DNTs is characterized theoretically for the first time.Then,by using the minimum potential energy principle,the force-extension curve and tensile rigidity of pre-tension DNTs are predicted.Finally,the effects of the encapsulation structure and surrounding factors on the tensile properties of DNTs are studied.The predictions for the tensile behaviors of DNTs can not only reproduce the existing experimental results,but also reveal that the competition of DNA intrachain and interchain interactions in the encapsulation structures determines the pre-tension states of DNTs and their tensile properties.The changes in the pre-tension states and environmental factors make the monotonic or non-monotonic changes in the tensile properties of DNTs under longitudinal loads.
基金supported by the Beijing Natural Science Foundation(Grant No.8184074)the National Natural Science Foundation of China(Grant Nos.41705006&41805011)the Beijing Young Scholars Program。
文摘Vegetation constitutes one of the fundamental types of land use on Earth.The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments,thus exerting notable influences on the urban microenvironment.A better understanding of the turbulent transfer of momentum and scalars around vegetation canopy could significantly contribute to improvement of the urban environment.This work develops a large-eddy simulation(LES)method that is applicable to model the flow and scalar transport over the forest canopy.We study the atmospheric flow over complex forested areas under typical weather conditions by coupling LES to the mesoscale model.Models of radiation and energy balance have been developed with explicit treatment of the vegetation canopy.By examining the flow over a forest canopy under a range of stability conditions,we found that buoyancy enhances or suppresses turbulent mixing in unstable or stable atmosphere respectively,with decreasing or increasing wind shear,respectively.From the multiscale modeling of the Beijing Olympic Forest Park,the present coupling scheme proves to better resolve the diurnal variations in wind speed,temperature,and relative humidity over complex urban terrains.The coupling scheme is superior to the traditional mesoscale model in terms of wind field simulation.This is mainly because the coupling scheme not only takes the influences of external mesoscale flow into consideration,but also resolves the heterogeneous urban surface at a fine scale by downscaling,thus better reproducing the complex flow and turbulent transport in the urban roughness sublayer.
