The purpose is to reestablish the balance laws of momentum, angular momentum and energy and to derive the corresponding local and nonlocal balance equations for micromorphic continuum mechanics and couple stress theor...The purpose is to reestablish the balance laws of momentum, angular momentum and energy and to derive the corresponding local and nonlocal balance equations for micromorphic continuum mechanics and couple stress theory. The desired results for micromorphic continuum mechanics and couple stress theory are naturally obtained via direct transitions and reductions from the coupled conservation law of energy for micropolar continuum theory, respectively. The basic balance laws and equations for micromorphic continuum mechanics and couple stress theory are constituted by combining these results derived here and the traditional conservation laws and equations of mass and microinertia and the entropy inequality. The incomplete degrees of the former related continuum theories are clarified. Finally, some special cases are conveniently derived.展开更多
A new tunnel recombination junction is fabricated for n-i-p type micromorph tandem solar cells. We insert a thin heavily doped hydrogenated amorphous silicon （a-Si：H） p^＋ recombination layer between the n a-Si：H ...A new tunnel recombination junction is fabricated for n-i-p type micromorph tandem solar cells. We insert a thin heavily doped hydrogenated amorphous silicon （a-Si：H） p^＋ recombination layer between the n a-Si：H and the p hydrogenated nanocrystalline silicon （nc-Si：H） layers to improve the performance of the n-i-p tandem solar cells. The effects of the boron doping gas ratio and the deposition time of the p-a-Si：H recombination layer on the tunnel recombination junctions have been investigated. The current-voltage characteristic of the tunnel recombination junction shows a nearly ohmic characteristic, and the resistance of the tunnel recombination junction can be as low as 1.5 Ω-cm^2 by using the optimized p-a-Si：H recombination layer. We obtain tandem solar cells with open circuit voltage Voc = 1.4 V, which is nearly the sum of the Vocs of the two corresponding single cells, indicating no Voc losses at the tunnel recombination junction.展开更多
In this work we propose to replace the GLPD hypo-elasticity law by a more rigorous generalized Hooke＇s law based on classical material symmetry characterization assumptions. This law introduces in addition to the two...In this work we propose to replace the GLPD hypo-elasticity law by a more rigorous generalized Hooke＇s law based on classical material symmetry characterization assumptions. This law introduces in addition to the two well- known Lame＇s moduli, five constitutive constants. An analytical solution is de- rived for the problem of a spherical shell subjected to axisymmetric loading con- ditions to illustrate the potential of the proposed generalized Hooke＇s law.展开更多
As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with ...As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with remarkable microstructures. After the basic governing equations are given and the reciprocal theorem is deduced, both the generalized variational prin- ciple and the generalized Hamilton principle for mixed boundary-initial value problems of micro- morphic thermoelectroelastodynamics in convolution form are established. Finally, as a primary application, steady state responses of an unbounded homogeneous isotropic micromorphic thermo- electroelastic body to external concentrated loads with mechanical, electric, and thermal origins are analyzed.展开更多
In this article,we introduce a complete set of constitutive relations and field equations for the linear reduced micromorphic model.We further investigate the internal variables and their relationship in the case of t...In this article,we introduce a complete set of constitutive relations and field equations for the linear reduced micromorphic model.We further investigate the internal variables and their relationship in the case of two-dimensional(2D)wave propagation.The dynamic response is investigated for composite materials,which is due to an external wave in two dimensions applied at the boundary of the considered domain.Analytical solutions for the model are unavailable at this stage due to dependency of the field equations on spatial and time variables in a complicated manner.A finite element approach is adopted to derive approximate solutions for the field equations,and numerical finite element solutions for the internal fields are presented in detail and discussed.展开更多
This paper presents derivation of micro and macro conservation and balance laws and the constitutive theories for the linear elastic micromorphic theory,in which elasticity is considered for microconstituents,the soli...This paper presents derivation of micro and macro conservation and balance laws and the constitutive theories for the linear elastic micromorphic theory,in which elasticity is considered for microconstituents,the solid medium,and for the interaction of microconstituents with the solid medium.The conservation and balance laws are initiated for micro deformation,followed by consistent“integral-average”definitions valid at the macro level.These permit the derivation of the conservation and balance laws at the macro level.Significant aspects of this theory are:1)microconstituent rigid rotation physics is the same in all 3M theories.The rigid rotations of the microconstituents are in fact classical rotations;hence,they do not introduce three unknown degrees of freedom at the material point and also can not be part of the strain measures.Thus,in this theory,a microconstituent has only six unknown degrees of freedom,six independent components of the symmetric part of the micro deformation gradient tensor,as opposed to Eringen’s theory,in which all nine components of the micro deformation gradient tensor are unknown degrees of freedom.2)The balance of moment of moments balance law is shown to be essential in all 3M theories and hence is considered here,due to which the Cauchy moment tensor is symmetric.This avoids a spurious constitutive theory for the moment tensor.3)In the case of nonsymmetric macro Cauchy stress tensor,the constitutive theory is needed only for the symmetric part,as the skew-symmetric part is defined by the balance of angular momenta.4)The smoothing weighting functionφ^((α))for the microconstituent,as advocated by Eringen and used to multiply the balance of linear momenta of the micro deformation physics,has no thermodynamic,physical or mathematical basis;hence,it is not used in the present work.5)In contrast with published works of Eringen and others,all constitutive tensors of rank two are always symmetric,hence always permitting the use of the representation theorem in deriving constitu tive theories,ensuring the mathematical consistency of the resulting theories.6)Conservation of micro inertia,necessary in Eringen’s theories to provide closure to the mathematical model,is neither needed nor used in the present work.The linear micromorphic theory derived here is compared with Eringen’s theory to identify differences,discuss and evaluate these for their validity based on thermodynamic and mathematical principles to ultimately determine the thermodynamic and mathematical consistency of the published micromorphic theories.展开更多
In this paper,we consider the derivation of constitutive theories for a linear micromorphic polymeric solid medium in which the microconstituents,the solid medium and the interaction of the microconstituents with the ...In this paper,we consider the derivation of constitutive theories for a linear micromorphic polymeric solid medium in which the microconstituents,the solid medium and the interaction of the microconstituents with the solid medium have mechanisms of elasticity,dissipation and rheology.Thermodynamically and mathematically consistent conservation and balance laws derived by Surana et al.in a recent paper for linear micromorphic solids are utilized in the present work.The conjugate pairs in the entropy inequality,in conjunction with the axiom of causality,are used in establishing constitutive tensors and the initial choice of argument tensors.These are modified or augmented to incorporate a more comprehensive ordered rate mechanism of dissipation and rheology for the microconstituents,the medium,and the interaction of the microconstituents with the solid medium.The constitutive theories presented in the paper provide spectra of viscosities and relaxation times.Constitutive theories and the material coefficients are derived using the representation theorem based on integrity.Simplified forms of the constitutive theories are also presented.It is shown that the complete mathematical model,consisting of the conservation and balance laws and the constitutive theories,has closure without the use of the conservation of microinertia law advocated and used by Eringen and another additional balance law also used by Eringen to obtain six equations needed for closure;both of these laws are outside the thermodynamic framework.展开更多
Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two...Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.展开更多
In this paper,the micromorphic theory and the second gradient theory are proposedwhere the micromorphic model can be reduced to the second gradient model with the vanishing relative deformation between macrodeformatio...In this paper,the micromorphic theory and the second gradient theory are proposedwhere the micromorphic model can be reduced to the second gradient model with the vanishing relative deformation between macrodeformation gradient and microdeformation.Analytical solutions for the simple shear problem in the case of a general small strain isotropic elasticity micromorphic model and the second gradient model are presented,respectively.Besides,uniaxial tension of a constrained layer with two different boundary conditions is also analytically solved.Finally,the micromorphic theory is implemented numerically within a two-dimensional plane strain finite element framework by developing two isoparametric elements.展开更多
文摘The purpose is to reestablish the balance laws of momentum, angular momentum and energy and to derive the corresponding local and nonlocal balance equations for micromorphic continuum mechanics and couple stress theory. The desired results for micromorphic continuum mechanics and couple stress theory are naturally obtained via direct transitions and reductions from the coupled conservation law of energy for micropolar continuum theory, respectively. The basic balance laws and equations for micromorphic continuum mechanics and couple stress theory are constituted by combining these results derived here and the traditional conservation laws and equations of mass and microinertia and the entropy inequality. The incomplete degrees of the former related continuum theories are clarified. Finally, some special cases are conveniently derived.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB202604)the Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. 1KGCX2-YW-383-1)the National High Technology Research and Development Program of China (Grant No. SQ2010AA0521758001)
文摘A new tunnel recombination junction is fabricated for n-i-p type micromorph tandem solar cells. We insert a thin heavily doped hydrogenated amorphous silicon （a-Si：H） p^＋ recombination layer between the n a-Si：H and the p hydrogenated nanocrystalline silicon （nc-Si：H） layers to improve the performance of the n-i-p tandem solar cells. The effects of the boron doping gas ratio and the deposition time of the p-a-Si：H recombination layer on the tunnel recombination junctions have been investigated. The current-voltage characteristic of the tunnel recombination junction shows a nearly ohmic characteristic, and the resistance of the tunnel recombination junction can be as low as 1.5 Ω-cm^2 by using the optimized p-a-Si：H recombination layer. We obtain tandem solar cells with open circuit voltage Voc = 1.4 V, which is nearly the sum of the Vocs of the two corresponding single cells, indicating no Voc losses at the tunnel recombination junction.
文摘In this work we propose to replace the GLPD hypo-elasticity law by a more rigorous generalized Hooke＇s law based on classical material symmetry characterization assumptions. This law introduces in addition to the two well- known Lame＇s moduli, five constitutive constants. An analytical solution is de- rived for the problem of a spherical shell subjected to axisymmetric loading con- ditions to illustrate the potential of the proposed generalized Hooke＇s law.
基金Project supported by the State Key Laboratory of Materials Processing and Die & Mould Technology (No. 2011-P01)the National Natural Science Foundation of China (No. 11072082)
文摘As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with remarkable microstructures. After the basic governing equations are given and the reciprocal theorem is deduced, both the generalized variational prin- ciple and the generalized Hamilton principle for mixed boundary-initial value problems of micro- morphic thermoelectroelastodynamics in convolution form are established. Finally, as a primary application, steady state responses of an unbounded homogeneous isotropic micromorphic thermo- electroelastic body to external concentrated loads with mechanical, electric, and thermal origins are analyzed.
文摘In this article,we introduce a complete set of constitutive relations and field equations for the linear reduced micromorphic model.We further investigate the internal variables and their relationship in the case of two-dimensional(2D)wave propagation.The dynamic response is investigated for composite materials,which is due to an external wave in two dimensions applied at the boundary of the considered domain.Analytical solutions for the model are unavailable at this stage due to dependency of the field equations on spatial and time variables in a complicated manner.A finite element approach is adopted to derive approximate solutions for the field equations,and numerical finite element solutions for the internal fields are presented in detail and discussed.
文摘This paper presents derivation of micro and macro conservation and balance laws and the constitutive theories for the linear elastic micromorphic theory,in which elasticity is considered for microconstituents,the solid medium,and for the interaction of microconstituents with the solid medium.The conservation and balance laws are initiated for micro deformation,followed by consistent“integral-average”definitions valid at the macro level.These permit the derivation of the conservation and balance laws at the macro level.Significant aspects of this theory are:1)microconstituent rigid rotation physics is the same in all 3M theories.The rigid rotations of the microconstituents are in fact classical rotations;hence,they do not introduce three unknown degrees of freedom at the material point and also can not be part of the strain measures.Thus,in this theory,a microconstituent has only six unknown degrees of freedom,six independent components of the symmetric part of the micro deformation gradient tensor,as opposed to Eringen’s theory,in which all nine components of the micro deformation gradient tensor are unknown degrees of freedom.2)The balance of moment of moments balance law is shown to be essential in all 3M theories and hence is considered here,due to which the Cauchy moment tensor is symmetric.This avoids a spurious constitutive theory for the moment tensor.3)In the case of nonsymmetric macro Cauchy stress tensor,the constitutive theory is needed only for the symmetric part,as the skew-symmetric part is defined by the balance of angular momenta.4)The smoothing weighting functionφ^((α))for the microconstituent,as advocated by Eringen and used to multiply the balance of linear momenta of the micro deformation physics,has no thermodynamic,physical or mathematical basis;hence,it is not used in the present work.5)In contrast with published works of Eringen and others,all constitutive tensors of rank two are always symmetric,hence always permitting the use of the representation theorem in deriving constitu tive theories,ensuring the mathematical consistency of the resulting theories.6)Conservation of micro inertia,necessary in Eringen’s theories to provide closure to the mathematical model,is neither needed nor used in the present work.The linear micromorphic theory derived here is compared with Eringen’s theory to identify differences,discuss and evaluate these for their validity based on thermodynamic and mathematical principles to ultimately determine the thermodynamic and mathematical consistency of the published micromorphic theories.
文摘In this paper,we consider the derivation of constitutive theories for a linear micromorphic polymeric solid medium in which the microconstituents,the solid medium and the interaction of the microconstituents with the solid medium have mechanisms of elasticity,dissipation and rheology.Thermodynamically and mathematically consistent conservation and balance laws derived by Surana et al.in a recent paper for linear micromorphic solids are utilized in the present work.The conjugate pairs in the entropy inequality,in conjunction with the axiom of causality,are used in establishing constitutive tensors and the initial choice of argument tensors.These are modified or augmented to incorporate a more comprehensive ordered rate mechanism of dissipation and rheology for the microconstituents,the medium,and the interaction of the microconstituents with the solid medium.The constitutive theories presented in the paper provide spectra of viscosities and relaxation times.Constitutive theories and the material coefficients are derived using the representation theorem based on integrity.Simplified forms of the constitutive theories are also presented.It is shown that the complete mathematical model,consisting of the conservation and balance laws and the constitutive theories,has closure without the use of the conservation of microinertia law advocated and used by Eringen and another additional balance law also used by Eringen to obtain six equations needed for closure;both of these laws are outside the thermodynamic framework.
文摘Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner structure.It is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner structure.In this work,the kinematics including the objective Eringen tensors is introduced.Balance laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean transformation.The concept of material force and the balance law of pseudomomentum are generalized for MMT.An axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic solid.Applications of MMT in micro/nanoscale are discussed.
基金supported by the National Natural Science Foundation of China (No. 10772096)
文摘In this paper,the micromorphic theory and the second gradient theory are proposedwhere the micromorphic model can be reduced to the second gradient model with the vanishing relative deformation between macrodeformation gradient and microdeformation.Analytical solutions for the simple shear problem in the case of a general small strain isotropic elasticity micromorphic model and the second gradient model are presented,respectively.Besides,uniaxial tension of a constrained layer with two different boundary conditions is also analytically solved.Finally,the micromorphic theory is implemented numerically within a two-dimensional plane strain finite element framework by developing two isoparametric elements.
