Papers by Keyword: Anisotropic

Abstract: Compression and collapse of unsaturated compacted loess are studied by using dry density and water content which easily controlled in engineering, the controlling range of dry density and water content are confirmed respectively. Then the deformation of compression and collapse and the frequency of engineering damager occurrence can be decreased. In addition, the mechanical characteristics of loess in different directions may differ because the loess was consolidated only under the condition of its upper weight of soil and load. The conventional mechanical experiments, including one-dimensional compress and collapse test, were conducted with the specimen of loess soil in different angle from the original horizontal plane. The test result shows that the loess is anisotropic

Abstract: Heat conduction in anisotropic materials has important applications in science and engineering. In this paper the virtual boundary element method (VBEM) is applied to solve these problems. Due to the fact of a virtual boundary outside the real boundary, the VBEM does not need to treat the singular boundary integrals, and thus, is more accurate and convenient than the traditional one. Numerical examples are presented, to demonstrate the efficiency and accuracy of this method.

Abstract: The anisotropic behavior of titanium alloy sheet TB5 cannot be accurately obtained by experimental identification of standard sheet uniaxile tensile tests. This paper describes a powerful technique allows for the identification of Hill’48 anisotropic parameters by inverse technique method based on the response surface methodology and quasi-Newton method. The identification approach takes the cylinder drawing as study object, and anisotropic parameters as optimum parameters. And the anisotropic parameters, which gained directly from experimental orthogonal test and uniform design tests, are tuned in the finite element model, that the numerically computed height and thickness of the cup matches the experimentally measured field as closely as possible. The result shows that the anisotropic parameters from the inverse identification can describe the mechanical behavior well.

Abstract: Based on the two-dimensional elasticity,the symplectic method is applied to study analytically the stress distributions of anisotropic beam.Using variation principle and introducing separation of variables, dual equations were presented.Then in the symplectic space which consists of the original variables and their dual variables,the problem can be solved via effective mathematical physics methods such as the method of sepatation of variables and eigenfunction vector expansion.So the original problems come down to solve the eigensolutions of zero eigenvalue and non-zeroes eigenvalue that describe the exponentially decaying localized solutions usually ignored by Saint-Venant's principle. Completed numerical examples are newly given to compare with established results.

Abstract: Rotational rheometer was employed to determine rheological properties of sodium alginate solutions of 3, 5 and 10wt.% concentrations. The results showed that temperature had a strong effect on the morphology of sodium alginate in aqueous solutions. To observe the anisotropic phase formation, Polarized optical microscopy (POM) experiments were performed. It revealed the presence of briefringence in 3, 5 and 10wt.% sodium alginate solutions.

Abstract: A material is radially anisotropic piezoelectric when its generalized Hooke’s law at each material point referred to a spherical coordinate system is the same everywhere. In a recent paper by Ting, the remarkable nature at the center of a sphere has been shown when a spherically uniform linear anisotropic elastic material is subjected to a uniform traction at the surface of the sphere. This paper extends elastic material for piezoelectric material, and shows that the singular problems also prevail in piezoelectric material. When a sphere of piezoelectric material is subjected to a uniform traction and electric potential at the surface of the sphere, for a certain range of material parameter, the stress, the electric field and the electric potential at the center of the sphere are infinite. When the sphere is subjected to a uniform tension, a cavitation occurs at the center of the sphere. If the applied traction is a uniform pressure, a black hole occurs at the center of the sphere. The singular problems depend only on one non-dimensional material parameter and the direction of the applied traction, while is independent of the magnitude of the traction.

Abstract: Applying KP theory combined with deformation potential we obtained the valence band structure, and based on this result we calculated the orientation-dependent effective mass which is also called conductivity effective mass in strained Si_1-xGe_x/(001)Si in this research, and furthermore ,we established the scattering rate model by using the density-of-states effective mass. On the basis of conductivity effective mass and scattering rate model, utilizing analytical method and relaxation time approximation we obtained the dependence of the value of hole mobility on stress and doping concentration in strained Si_1-xGe_x/(001)Si along different crystal orientations. Compare to the unstrained Si, the anisotropy of hole mobility is more obvious in strained Si_1-xGe_x/(001)Si, for example, It shows that under the same stress and doping concentration (Ni=1x1014cm-3, x=0.4), the value of hole mobility along [010] crystal orientation is visibly higher than other crystal orientations. This result can provide valuable references to the research of hole mobility of strained Si1-xGex materials and the design of devices.

Abstract: Based on the two-dimensional elasticity,the symplectic method is applied to study analytically the stress distributions of anisotropic beam.Using variation principle and introducing separation of variables, dual equations were presented.Then in the symplectic space which consists of the original variables and their dual variables,the problem can be solved via effective mathematical physics methods such as the method of sepatation of variables and eigenfunction vector expansion.So the original problems come down to solve the eigensolutions of zero eigenvalue and non-zeroes eigenvalue that describe the exponentially decaying localized solutions usually ignored by Saint-Venant's principle. Completed numerical examples are newly given to compare with established results.

Abstract: Anisotropic hydrogels based on acrylamide were prepared by frontal photopolymerization. First hydrophilic microgels (HM) were spreparaed by inverse emulsion photopolymerization, and secondly hydrophilic reactive microgels (HRM) with C=C double bonds were synthesis by chemical modification of the HM used N-methylolacrylamide, Last, HRM hydrogels were synthesis by frontal photopolymerization using HRM as crosslinkers. Only one direction of the HRM hydrogels show excellent fracture strength and tensile elongation but the other two directions show little fracture strength and tensile elongation. The reason of the high mechanical performance in the given direction is that the hydrogels are crosslinked by HRM as a new crosslinking agent instead of the conventional crosslinking agents and these nanoparticles can self-assemble into anisotropic structures and the structure can be stabilized by free radical polymerization. The anisotropic hydrogels could use potential materials such as artificial muscles tissue.

Abstract: Heat conduction in anisotropic materials is quite different from that in isotropic materials. Heat flux vector is commonly not perpendicular to the isothermal surface in anisotropic materials. The advantage and disadvantage of anisotropic materials were analyzed in this paper. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The technique of double skin facade has been successfully applied in many building designs. The application of combining building envelope of anisotropic materials and double skin facade was proposed to avoid its disadvantage. Basing on the combination of anisotropic materials and double skin facade in building envelope, the indoor cooling and heating load decrease in summer and winter respectively. Especially in summer, the effect of energy saving is obvious since the partial magnitude of conductive heat in the envelope made of anisotropic materials could be brought out from the cavity of double skin facade by natural or forced ventilation through it.