The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro...The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition,and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore,they exhibit more kinematic hardening.展开更多
Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by a...Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettahility, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.展开更多
In this paper,we study oriented surfaces of R3 in the context of Laguerre geometry.We construct Laguerre invariants on the non-Dupin developable surfaces,which determine the surfaces up to a Laguerre transformation.Fi...In this paper,we study oriented surfaces of R3 in the context of Laguerre geometry.We construct Laguerre invariants on the non-Dupin developable surfaces,which determine the surfaces up to a Laguerre transformation.Finally,we classify the Laguerre homogeneous surfaces in R3 under the Laguerre transformation groups.展开更多
Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coor...Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coordinate system transform, the scalar equation is standardized into a Helmholtz equation. Corresponding integral equations are derived for the scattering problems and boundary element method (BEM) is used to calculate the scattered fields of arbitrarily shaped obstacles with both soft and rigid boudary conditions numerically.A discussion is given on the numerical results which is mainly focused on the influence of the a-nisotropy of the media to the directivity of the scattered fields by circular cylindrical voids.展开更多
基金supported by the Danish Research Council for Technology and Production Sciences in a project entitled Plasticity Across the Scales
文摘The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition,and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore,they exhibit more kinematic hardening.
基金supported by the National Basic Research Programs of China (No. 2011CB922102)the National Natural Science Foundation of China (No. 11374141)the City University of Hong Kong Strategic Research Grant (SRG, No. 7004188)
文摘Qianlong Xuan paper, lost two hundred years ago, was reproduced by engineers in Red-Star Xuan Paper Limited Liability Company of China. Its remarkable performance and profound historical value are highly regarded by artists and the paper commands very high price in the commercial market. Ink penetrates and spreads optimally in the paper and the words exhibit clear edges with small fluctuations because of the desirable wettability and wicking. These characteristics make it stand out from three Xuan paper samples. The good wettahility, verified by contact angle measurements, is an essential prerequisite to strong wicking. Attenuated total reflectance Fourier-transform infrared spectroscopy is performed to determine the chemical structure of Qianlong Xuan paper and the relatively large hydrogen bonding ratio contributes to the hydrophilicity. The microstructure investigated by scanning electron microscopy and atomic force microscopy reveals wide fibers and a uniform fiber arrangement with good connectivity, dense network, as well as rough fiber surface. These unique properties endow Qianlong Xuan paper with strong wicking to improve the ink expression.
基金supported by National Natural Science Foundation of China (Grant No.10801006)
文摘In this paper,we study oriented surfaces of R3 in the context of Laguerre geometry.We construct Laguerre invariants on the non-Dupin developable surfaces,which determine the surfaces up to a Laguerre transformation.Finally,we classify the Laguerre homogeneous surfaces in R3 under the Laguerre transformation groups.
文摘Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coordinate system transform, the scalar equation is standardized into a Helmholtz equation. Corresponding integral equations are derived for the scattering problems and boundary element method (BEM) is used to calculate the scattered fields of arbitrarily shaped obstacles with both soft and rigid boudary conditions numerically.A discussion is given on the numerical results which is mainly focused on the influence of the a-nisotropy of the media to the directivity of the scattered fields by circular cylindrical voids.
