Significant progress has been made in mixed boundary-value problems associated with three-dimensional（3D） crack and contact analyses of advanced materials featuring more complexities compared to the conventional iso...Significant progress has been made in mixed boundary-value problems associated with three-dimensional（3D） crack and contact analyses of advanced materials featuring more complexities compared to the conventional isotropic elastic materials.These include material anisotropy and multifield coupling,two typical characteristics of most current multifunctional materials.In this paper we try to present a state-of-the-art description of 3D exact/analytical solutions derived for crack and contact problems of elastic solids with both transverse isotropy and multifield coupling in the latest decade by the potential theory method in the spirit of V.I.Fabrikant.whose ingenious breakthrough brings new vigor and vitality to the old research subject of classical potential theory.We are particularly interested in crack and contact problems with certain nonlinear features.Emphasis is also placed on the coupling between the temperature field（or the like） and other physical fields（e.g.,elastic,electric,and magnetic fields）.We further highlight the practical significance of 3D contact solutions,in particular in applications related to modern scanning probe microscopes.展开更多
Stretchable electronics represents a direction of recent development in next-generation semiconductor devices.Such systems have the potential to offer the performance of conventional wafer-based technologies,but they ...Stretchable electronics represents a direction of recent development in next-generation semiconductor devices.Such systems have the potential to offer the performance of conventional wafer-based technologies,but they can be stretched like a rubber band,twisted like a rope, bent over a pencil,and folded like a piece of paper.Isolating the active devices from strains associated with such deformations is an important aspect of design.One strategy involves the shielding of the electronics from deformation of the substrate through insertion of a compliant adhesive layer. This paper establishes a simple,analytical model and validates the results by the finite element method.The results show that a relatively thick,compliant adhesive is effective to reduce the strain in the electronics,as is a relatively short film.展开更多
The symplectic approach proposed and developed by Zhong et al. in 1990s for elasticity problems is a rational analytical method, in which ample experience is not needed as in the conventional semi-inverse method. In t...The symplectic approach proposed and developed by Zhong et al. in 1990s for elasticity problems is a rational analytical method, in which ample experience is not needed as in the conventional semi-inverse method. In the symplectic space, elasticity problems can be solved using the method of separation of variables along with the eigenfunction expansion technique, as in traditional Fourier analysis. The eigensolutions include those corresponding to zero and nonzero eigenvalues. The latter group can be further divided into α-and β-sets. This paper reformulates the form of β-set eigensolutions to achieve the stability of numerical calculation, which is very important to obtain accurate results within the symplectic frame. An example is finally given and numerical results are compared and discussed.展开更多
We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric bias...We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric biasing field. By adopting the linearized theory for incremental fields, which is established on the basis of a general nonlinear theory for electroelasticity, the appropriate equations governing the perturbed infinitesimal elastic and electric fields are derived particularly when the material is subjected to a uniform equibiaxial stretch and a uniform electric displacement. A general solution to the governing equations is presented, which is concisely expressed in terms of four quasi-harmonic functions. By adopting the potential theory method, exact contact solutions for three common perfectly conducting rigid indenters of fiat-ended circular, conical and spherical geometries can be derived, and some explicit relations that are of practical importance are outlined.展开更多
Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mecha...Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mechanics may be seen as the symbol of modem mechanics, which differs greatly from current physics, the two often being mixed up by people and even sci- entists. In this short paper, I will first try to give an illustration on the differences between （modem） mechanics and physics, in my personal view, and then focus on some important current research activities in continuum mechanics, attempting to identify its path to the near future. We can see that continuum mechanics, while having a dominating impact on engineering design in the 20th century, also plays a pivotal role in modem science, and is much closer to physics, chemistry, biology, etc. than ever before.展开更多
Tuning band gaps in soft materials by post-buckling deformation is becoming an appealing means to manipulate elastic waves. As one of the most favorable topologies, two- dimensional soft structures with circular holes...Tuning band gaps in soft materials by post-buckling deformation is becoming an appealing means to manipulate elastic waves. As one of the most favorable topologies, two- dimensional soft structures with circular holes have been extensively studied. Based on the contrarian thinking, this paper starts from the two-dimensional soft structures with criss-crossed elliptical holes, which is close to the post-buckling configuration of soft structures with circular holes, and then proposes to tune the band gaps through elongating or stretching rather than compressing. Influences of the loading magnitude and loading pattern （i.e., uniaxial and biaxial elongations） on the band gaps are studied via the nonlinear finite element simulations. Effects of the geometric parameters （the major-to-minor half-axis ratio and the porosity of the structure） are also discussed. It is shown that, compared with the traditional circular hole case, the band gaps of the unloaded structure with criss-crossed elliptical holes are much richer, and they could be reversely and continuously tuned by tensile loadings. In particular, the deformation is very robust and is insensitive to small geometric imperfections, which is always necessary for triggering the post-buckling deformations. The present work provides a useful reference to the manipula- tion of elastic waves in periodic structures as well as the design of soft phononic crystals/acoustic devices.展开更多
This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building.The window Reynolds nu...This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building.The window Reynolds number(Re_(w))was specified to characterize the indoor flow and dispersion.The indicators of RRC(ratio of relative change)or DR(K_DR)(difference ratio of dimensionless concentration)<5%were applied to quantitatively determine the critical Rew for indoor flow and turbulent diffusion.The results show that the critical Re(Re_(crit)) value is position-dependent,and Re_(crit) at the most unfavorable position should be suggested as the optimal value within the whole areas of interest.Thus Re(H,orit)=27,000 is recommended for the outdoor flows;while Re_(w,crit)=15,000 is determined for the indoor flows due to the lower part below the window showing the most unfavorable.The suggested Re_(w,crit)(=15,000)for indoor airflow and cross ventilation is independence of the window size.Moreover,taking K_DR≤5% as the indicator,the suggested Re_(w,crit) for ensuring indoor pollutant diffusion enter the independence regime should also be 15,000,indicating that indoor passive diffusion is completely determined by the flow structures.The contours of dimensionless velocity(U/U_(0))and concentration(K)against the increasing Re(w) further confirmed this critical value.This study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.展开更多
The elastic modulus of asphalt concrete(AC) is an important material parameter for pavement design.The prediction and determination of elastic modulus,however,largely depends on laboratory tests which cannot reflect e...The elastic modulus of asphalt concrete(AC) is an important material parameter for pavement design.The prediction and determination of elastic modulus,however,largely depends on laboratory tests which cannot reflect explicitly the influence of the microstructure of AC.To this end,a micromechanical model based on stepping scheme is adopted.Consideration is given to the influence of interfacial debonding and interlocking effect between the aggregates and asphalt mastic using the concept of effective bonding.Tests on asphalt mixture with various microstructures are conducted to verify the proposed approach.It is shown that the prediction is generally in agreement with experimental results.Parameters affecting the elastic modulus of AC are also discussed in light of the proposed method.展开更多
基金supported by the National Natural Science Foundation of China(Grant 11321202)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant 20130101110120)
文摘Significant progress has been made in mixed boundary-value problems associated with three-dimensional（3D） crack and contact analyses of advanced materials featuring more complexities compared to the conventional isotropic elastic materials.These include material anisotropy and multifield coupling,two typical characteristics of most current multifunctional materials.In this paper we try to present a state-of-the-art description of 3D exact/analytical solutions derived for crack and contact problems of elastic solids with both transverse isotropy and multifield coupling in the latest decade by the potential theory method in the spirit of V.I.Fabrikant.whose ingenious breakthrough brings new vigor and vitality to the old research subject of classical potential theory.We are particularly interested in crack and contact problems with certain nonlinear features.Emphasis is also placed on the coupling between the temperature field（or the like） and other physical fields（e.g.,elastic,electric,and magnetic fields）.We further highlight the practical significance of 3D contact solutions,in particular in applications related to modern scanning probe microscopes.
基金supported by NSF(DMI-0328162 and ECCS-0824129)the National Natural Science Foundation of China (10820101048)Ministry of Education of China,and the National Basic Research Program of China(2007CB936803).
文摘Stretchable electronics represents a direction of recent development in next-generation semiconductor devices.Such systems have the potential to offer the performance of conventional wafer-based technologies,but they can be stretched like a rubber band,twisted like a rope, bent over a pencil,and folded like a piece of paper.Isolating the active devices from strains associated with such deformations is an important aspect of design.One strategy involves the shielding of the electronics from deformation of the substrate through insertion of a compliant adhesive layer. This paper establishes a simple,analytical model and validates the results by the finite element method.The results show that a relatively thick,compliant adhesive is effective to reduce the strain in the electronics,as is a relatively short film.
基金the National Natural Science Foundation of China (Nos. 10725210 and 10432030) the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20060335107)the Program for New Century Excellent Talents in University, MOE, China (No. NCET-05-05010)
文摘The symplectic approach proposed and developed by Zhong et al. in 1990s for elasticity problems is a rational analytical method, in which ample experience is not needed as in the conventional semi-inverse method. In the symplectic space, elasticity problems can be solved using the method of separation of variables along with the eigenfunction expansion technique, as in traditional Fourier analysis. The eigensolutions include those corresponding to zero and nonzero eigenvalues. The latter group can be further divided into α-and β-sets. This paper reformulates the form of β-set eigensolutions to achieve the stability of numerical calculation, which is very important to obtain accurate results within the symplectic frame. An example is finally given and numerical results are compared and discussed.
基金supported by the National Natural Science Foundation of China(10832009 and 11090333)the Fundamental Research Funds for Central Universities(2011XZZX002)
文摘We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric biasing field. By adopting the linearized theory for incremental fields, which is established on the basis of a general nonlinear theory for electroelasticity, the appropriate equations governing the perturbed infinitesimal elastic and electric fields are derived particularly when the material is subjected to a uniform equibiaxial stretch and a uniform electric displacement. A general solution to the governing equations is presented, which is concisely expressed in terms of four quasi-harmonic functions. By adopting the potential theory method, exact contact solutions for three common perfectly conducting rigid indenters of fiat-ended circular, conical and spherical geometries can be derived, and some explicit relations that are of practical importance are outlined.
基金Project supported by the National Natural Science of Foundation of China(Nos.11321202 and 11272281)
文摘Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mechanics may be seen as the symbol of modem mechanics, which differs greatly from current physics, the two often being mixed up by people and even sci- entists. In this short paper, I will first try to give an illustration on the differences between （modem） mechanics and physics, in my personal view, and then focus on some important current research activities in continuum mechanics, attempting to identify its path to the near future. We can see that continuum mechanics, while having a dominating impact on engineering design in the 20th century, also plays a pivotal role in modem science, and is much closer to physics, chemistry, biology, etc. than ever before.
基金The work was supported by the National Natural Science Foundation of China （11532001, 11621062）. Partial support from the Fundamental Research Funds for the Central Universities （No. 2016XZZX001-05） is also acknowledged. The work was also supported by the Shenzhen Scientific and Technological Fund for R ＆ D （No. JCYJ20170816172316775）.
文摘Tuning band gaps in soft materials by post-buckling deformation is becoming an appealing means to manipulate elastic waves. As one of the most favorable topologies, two- dimensional soft structures with circular holes have been extensively studied. Based on the contrarian thinking, this paper starts from the two-dimensional soft structures with criss-crossed elliptical holes, which is close to the post-buckling configuration of soft structures with circular holes, and then proposes to tune the band gaps through elongating or stretching rather than compressing. Influences of the loading magnitude and loading pattern （i.e., uniaxial and biaxial elongations） on the band gaps are studied via the nonlinear finite element simulations. Effects of the geometric parameters （the major-to-minor half-axis ratio and the porosity of the structure） are also discussed. It is shown that, compared with the traditional circular hole case, the band gaps of the unloaded structure with criss-crossed elliptical holes are much richer, and they could be reversely and continuously tuned by tensile loadings. In particular, the deformation is very robust and is insensitive to small geometric imperfections, which is always necessary for triggering the post-buckling deformations. The present work provides a useful reference to the manipula- tion of elastic waves in periodic structures as well as the design of soft phononic crystals/acoustic devices.
基金This work was supported by Shanghai Sailing Program(No.18YF1417600),Scientific and Innovative Action Plan of Shanghai(No.20dz 1204008)the National Natural Science Foundation of China(No.51536006).
文摘This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building.The window Reynolds number(Re_(w))was specified to characterize the indoor flow and dispersion.The indicators of RRC(ratio of relative change)or DR(K_DR)(difference ratio of dimensionless concentration)<5%were applied to quantitatively determine the critical Rew for indoor flow and turbulent diffusion.The results show that the critical Re(Re_(crit)) value is position-dependent,and Re_(crit) at the most unfavorable position should be suggested as the optimal value within the whole areas of interest.Thus Re(H,orit)=27,000 is recommended for the outdoor flows;while Re_(w,crit)=15,000 is determined for the indoor flows due to the lower part below the window showing the most unfavorable.The suggested Re_(w,crit)(=15,000)for indoor airflow and cross ventilation is independence of the window size.Moreover,taking K_DR≤5% as the indicator,the suggested Re_(w,crit) for ensuring indoor pollutant diffusion enter the independence regime should also be 15,000,indicating that indoor passive diffusion is completely determined by the flow structures.The contours of dimensionless velocity(U/U_(0))and concentration(K)against the increasing Re(w) further confirmed this critical value.This study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.
基金supported by the National Natural Science Foundation of China (Nos. 10725210 and 50808159)the National Basic Re-search Program (973) of China (No. 2009CB623204)
文摘The elastic modulus of asphalt concrete(AC) is an important material parameter for pavement design.The prediction and determination of elastic modulus,however,largely depends on laboratory tests which cannot reflect explicitly the influence of the microstructure of AC.To this end,a micromechanical model based on stepping scheme is adopted.Consideration is given to the influence of interfacial debonding and interlocking effect between the aggregates and asphalt mastic using the concept of effective bonding.Tests on asphalt mixture with various microstructures are conducted to verify the proposed approach.It is shown that the prediction is generally in agreement with experimental results.Parameters affecting the elastic modulus of AC are also discussed in light of the proposed method.
基金Project supported by the National Natural Science Foundation of China(Nos.11532001,11621062,and 11872329)the Fundamental Research Funds for the Central Universities(No.2016XZZX001-05)+1 种基金the Shenzhen Scientific and Technological Fund for R&D(No.JCYJ20170816172316775),China
