This paper presents a study on the concur- rent topology optimization of a structure and its material microstructure. A modified optimization model is proposed by introducing microstructure orientation angles as a new...This paper presents a study on the concur- rent topology optimization of a structure and its material microstructure. A modified optimization model is proposed by introducing microstructure orientation angles as a new type of design variable. The new model is based on the assumptions that a structure is made of a material with the same microstructure, and the material may have a different orientation within the design domain of the structure. The homogenization theory is applied to link the material and structure scales. An additional post-processing technique is developed for modifying the obtained design to avoid local optima caused by the use of orientation angle variables. Numerical examples are presented to illustrate the viabil- ity and effectiveness of the proposed model. It is found that significant improvement in structural performance can be achieved by optimizing the orientation of microstructures in concurrent topology optimization of structures and materials.展开更多
Supercapacitors are electrochemical energy storage devices with great potential applications.Mean-while,the oxygen evolution reaction(OER)determines the efficiency of some electrochemical energy conversions.This study...Supercapacitors are electrochemical energy storage devices with great potential applications.Mean-while,the oxygen evolution reaction(OER)determines the efficiency of some electrochemical energy conversions.This study aims at constructing,exploring,and optimizing Ramsdellite-MnO_(2)@NiCoAl-LDH@CC(R-MNCA@CC)composites.The effect of microstructure and Al role on the performance is investigated when R-MNCA@CC was used as supercapacitor electrode material and OER catalyst.Coral-like R-MNCA@CC in-situ growth composites were synthesized by a two-step hydrothermal method.R-MNCA@CC-2(molar ratio of Ni:Co:Al is 1:1:1)performs the best with the largest specific capacitance,1,742 F/g at 1 A/g,increased by 797%and 1,489%compared to that of NiCoAl-LDH and Ramsdellite-MnO_(2).The capacitance retention rate of the R-MNCA@CC-2//AC@CC supercapacitor is 80.1%after 5,000 cycles at 0.8 A/g.The overpotential for driving an OER to reach 10 m/cm^(2)is only 276 mV,which is lower than that of commercial IrO_(2)(300 mV).Noteworthy,we propose a view that is“competing to trigger redox re-action”of electrochemical active sites in LDH during electrochemical processes derived from a discrepancy between theory and experimental results.展开更多
A visco-plastic rate-dependent homogenization theory for particle-reinforced composites was derived and the equivalent elastic constants and the equivalent visco-plastic parameters of these composites were obtained. A...A visco-plastic rate-dependent homogenization theory for particle-reinforced composites was derived and the equivalent elastic constants and the equivalent visco-plastic parameters of these composites were obtained. A framework of homogenization the- ory for particle-reinforced W-Ni-Fe composites, a kind of tungsten alloy, was established. Based on the homogenization theory and a fixed-point iteration method, a unit cell model with typical microstructnres of the composite was established by using dynamic analysis program. The effects of tungsten content, tungsten particle shape and particle size and interface strength on the mechanical properties and the crack propagation of the W-Ni-Fe composite are analyzed under quasi-static and dynamic loadings. The stress-strain curves of the composite are given and the relation between the macro-mechanical characteristics and the microstructure parameters is explored, which provides an important theoretical basis for the optimization of the W-Ni-Fe composites.展开更多
Optimal microstructure design of battery materials is critical to enhance the performance of batteries for tailored applications such as high power cells.Accurate simulation of the thermodynamics,transport,and electro...Optimal microstructure design of battery materials is critical to enhance the performance of batteries for tailored applications such as high power cells.Accurate simulation of the thermodynamics,transport,and electrochemical reaction kinetics in commonly used polycrystalline battery materials remains a challenge.Here,we combine state-of-the-art multiphase field modelling with the smoothed boundary method to accurately simulate complex battery microstructures and multiphase physics.The phase-field method is employed to parameterize complex open pore cathode microstructures and we present a formulation to impose galvanostatic charging conditions on the diffuse boundary representation.By extending the smoothed boundary method to the multiphase-field method,we build a simulation framework which is capable of simulating the coupled effects of intercalation,anisotropic diffusion,and phase transitions in arbitrary complex polycrystalline agglomerates.This method is directly compatible with voxel-based data,e.g.,from X-ray tomography.The simulation framework is used to study the reversible phase transitions in Li_(X)NiO_(2)in dense and nanoporous agglomerates.Based on the thermodynamic consistency of phase-field approaches with ab-initio simulations and the open circuit potential,we reconstruct the Gibbs free energies of four individual phases(H1,M,H_(2)and H_(3))from experimental cycling data.The results show remarkable agreement with previously published DFT results.From charge simulations,we discover a strong influence of particle morphology on the phase transition behaviour,in particular a shrinking core-like behaviour in dense polycrystalline structures and a particle-by-particle mosaic behavior in nanoporous samples.Overall,the proposed simulation framework enables the detailed study of phase transitions in intercalation materials to enhance microstructure design and fast charging protocols.展开更多
基金supported by the State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, China (Grant GZ1305)
文摘This paper presents a study on the concur- rent topology optimization of a structure and its material microstructure. A modified optimization model is proposed by introducing microstructure orientation angles as a new type of design variable. The new model is based on the assumptions that a structure is made of a material with the same microstructure, and the material may have a different orientation within the design domain of the structure. The homogenization theory is applied to link the material and structure scales. An additional post-processing technique is developed for modifying the obtained design to avoid local optima caused by the use of orientation angle variables. Numerical examples are presented to illustrate the viabil- ity and effectiveness of the proposed model. It is found that significant improvement in structural performance can be achieved by optimizing the orientation of microstructures in concurrent topology optimization of structures and materials.
基金Great appreciation for the support of the funding of the Key R&D Program of Zhenjiang(GY201816)Student Innovation Project of Jiangsu University(22A030).
文摘Supercapacitors are electrochemical energy storage devices with great potential applications.Mean-while,the oxygen evolution reaction(OER)determines the efficiency of some electrochemical energy conversions.This study aims at constructing,exploring,and optimizing Ramsdellite-MnO_(2)@NiCoAl-LDH@CC(R-MNCA@CC)composites.The effect of microstructure and Al role on the performance is investigated when R-MNCA@CC was used as supercapacitor electrode material and OER catalyst.Coral-like R-MNCA@CC in-situ growth composites were synthesized by a two-step hydrothermal method.R-MNCA@CC-2(molar ratio of Ni:Co:Al is 1:1:1)performs the best with the largest specific capacitance,1,742 F/g at 1 A/g,increased by 797%and 1,489%compared to that of NiCoAl-LDH and Ramsdellite-MnO_(2).The capacitance retention rate of the R-MNCA@CC-2//AC@CC supercapacitor is 80.1%after 5,000 cycles at 0.8 A/g.The overpotential for driving an OER to reach 10 m/cm^(2)is only 276 mV,which is lower than that of commercial IrO_(2)(300 mV).Noteworthy,we propose a view that is“competing to trigger redox re-action”of electrochemical active sites in LDH during electrochemical processes derived from a discrepancy between theory and experimental results.
基金supported by the National Natural Science Foundation of China (Grant No. 11032002 and 91016013)the program for New Century Excellent Talents in University+1 种基金National Basic Research Program of China (Grant No. 2010CB832706)the project of State Key Laboratory of Explosion Science and Technology (Beijing Institute of Technology)(Grant No. ZDKT10-03a)
文摘A visco-plastic rate-dependent homogenization theory for particle-reinforced composites was derived and the equivalent elastic constants and the equivalent visco-plastic parameters of these composites were obtained. A framework of homogenization the- ory for particle-reinforced W-Ni-Fe composites, a kind of tungsten alloy, was established. Based on the homogenization theory and a fixed-point iteration method, a unit cell model with typical microstructnres of the composite was established by using dynamic analysis program. The effects of tungsten content, tungsten particle shape and particle size and interface strength on the mechanical properties and the crack propagation of the W-Ni-Fe composite are analyzed under quasi-static and dynamic loadings. The stress-strain curves of the composite are given and the relation between the macro-mechanical characteristics and the microstructure parameters is explored, which provides an important theoretical basis for the optimization of the W-Ni-Fe composites.
基金funded by the German Research Foundation (DFG) under Project ID 390874152 (POLiS Cluster of Excellence)Support by the Helmholtz association though the MTET programme (no. 38.02.01) is gratefully acknowledged.
文摘Optimal microstructure design of battery materials is critical to enhance the performance of batteries for tailored applications such as high power cells.Accurate simulation of the thermodynamics,transport,and electrochemical reaction kinetics in commonly used polycrystalline battery materials remains a challenge.Here,we combine state-of-the-art multiphase field modelling with the smoothed boundary method to accurately simulate complex battery microstructures and multiphase physics.The phase-field method is employed to parameterize complex open pore cathode microstructures and we present a formulation to impose galvanostatic charging conditions on the diffuse boundary representation.By extending the smoothed boundary method to the multiphase-field method,we build a simulation framework which is capable of simulating the coupled effects of intercalation,anisotropic diffusion,and phase transitions in arbitrary complex polycrystalline agglomerates.This method is directly compatible with voxel-based data,e.g.,from X-ray tomography.The simulation framework is used to study the reversible phase transitions in Li_(X)NiO_(2)in dense and nanoporous agglomerates.Based on the thermodynamic consistency of phase-field approaches with ab-initio simulations and the open circuit potential,we reconstruct the Gibbs free energies of four individual phases(H1,M,H_(2)and H_(3))from experimental cycling data.The results show remarkable agreement with previously published DFT results.From charge simulations,we discover a strong influence of particle morphology on the phase transition behaviour,in particular a shrinking core-like behaviour in dense polycrystalline structures and a particle-by-particle mosaic behavior in nanoporous samples.Overall,the proposed simulation framework enables the detailed study of phase transitions in intercalation materials to enhance microstructure design and fast charging protocols.
