Papers by Keyword: Anisotropy

Abstract: Thermal conductivity was the main thermal parameter that greatly influenced temperature distribution of materials especially in coatings. Some materials such as plasma-sprayed coatings that had a lamellar microstructure displayed the anisotropy of thermal conductivity. Thermal conductivities of isotropy and anisotropy metallic ceramic coatings were calculated and analyzed using Markworth method and parallel plate model, respectively. The influence of anisotropy on heat transfer and temperature distribution of coatings using finite element analysis and Gaussian heat source modal applied locally was investigated. Results showed that in anisotropic coatings the ratio of transverse and vertical thermal conductivity had a maximum value when metal volume fraction was 50%. The temperatures on the edge of heat sources (Th) had a maximum value, and the highest temperatures of substrate (Ts) had a minimum value with the same fraction. The value decreased by 79°C compared to that in the isotropy coatings. The highest temperatures of coatings (Tc) decreased expectedly with metal volume fraction rised. The maximum width of heat affected zone (HAZ) of coating and substrate was 4.52 mm at the metal content of 40%. The minimum HAZ depth was 0.27mm which was very small at the content of 50%, compared with 1.25 mm in isotropic coatings. It revealed that anisotropic conductive properties caused more heat transfer to outer regions and provided better protection for substrate.

Abstract: The MTS810 and SHPB are used to experimentally study the quasi-static and dynamic mechanical properties of three-dimensional E-glass fiber-reinforced composite. Stress-strain curves along the plane and thickness direction are obtained under varying strain rates, ranging from 10-3 to 103s-1. Experimental results show that strain rate has a significant effect on the material response. It is found that the compressive strength and the modulus increase with increasing strain rate, the failure strain, however, decreases slightly. But, the effect of strain rate in-plane and through thickness directions is different. A higher strain rate sensitive modulus and failure is found in the thickness direction, while a higher strain rate sensitive failure strength is found in the in-plane direction.

Abstract: Abstract. The regular grain orientation of granular materials is a common phenomenon in nature. Based on the research of grain shape effect on mechanical property of granular materials, two kinds of idealized shape grain (kind of long rod and square) assemblies with different grain orientation were studied by simulated biaxial compression test using Discrete Element Method. The significant orientation which can be computed as the mean value of all grain orientation is introduced to represent the orientation regularity of granular materials. In order to study the anisotropy, the mobilized friction angle and volumetric strain of assemblies with different significant orientation were obtained under both vertical and horizontal loading. The results show that the regular orientation of grains influences the movement such as motion and rotation obviously; with the increasing of significant orientation, peak mobilized friction angle of long rod grain assembly gradually increases under horizontal loading, and decreasing under vertical loading.

Abstract: Disturbed state concept theory (DSC) utilizes constitutive models to depict material responses. The response is gained by weight-averaging reference responses. DSC also can superpose disturbance factor on reference responses to reach actual response values. Suitable constitutive models give reference responses and DSC revises them to be acceptable outputs. Disturbance factor is independent to constitutive model. On DSC application on seepage problem, combination of DSC and Biot’s consolidation is forwarded by introducing disturbance factor into equilibrium function and extended cam-bridge model provides reference response. On DSC application on anisotropy, anisotropic disturbance factor is applied on to obtain stress anisotropy. Hierarchical single surface model is utilized to provide reference response for further anisotropic revision. Detailed formula derivation for DSC-seepage or for DSC-anisotropy is accomplished. On both applications, the key combination of DSC and other theory depends on the introduction of disturbance factor into equilibrium equation. Outcomes of DSC show readjustment of parameters of disturbance factor guaranties quantity of response descriptions. DSC takes into account of outside effects without changing inside. Existing models and existing methods can be used to describe newly responses.

Abstract: The effect of anisotropy of friction angle in natural deposited soil on the stability of soil slopes was studied in this paper. Stability analysis was performed on a uniform soil slope with anisotropic friction angle. Spencer’s method was used, and the variation of friction angle was assumed to be linear to the change of direction of the slip surface. It was shown that 7-10 percent of change in safety factor might achieve within a 10m-highed anisotropic soil slope. It was also found from the analysis that that frictional anisotropy had no obvious effect on the location of critical slip surface.

Abstract: Relationship between the chemical reactivity and the orientation of SiC substrates was investigated. Thermal etching of 4H-SiC in the mixed gas of oxygen and chlorine was carried out as the chemical reaction. The etching rate did not change monotonously with the increase of the off angle in 4H-SiC (000-1) C substrate. By the use of such tendency in the thermal etching, the three dimensional structure with the specific pyramidal plane was able to be obtained.

Abstract: The sub-trenches in 4H-SiC Si- and C-faces could be disappeared by the thermal treatment in chlorine ambience at 900-1000oC. The surface morphologies of the thermally treated trench-sidewalls were unchanged. It is considered that the sub-trench is selectively removed because thermally Cl2 etching rate of the (0001) Si- and (000-1) C-face are different to the (11-20) and (1-100).

Abstract: The channel mobility in 3C-SiC n-MOSFETs is investigated by current-voltage and Hall-effect measurements. For comparison, these techniques are also applied to 3C-SiC bulk rods. It turns out that the channel mobility depends on the orientation of the crystal and channel length. The observed results are traced back to the influence of Si-terminated stacking faults (Si-SFs), to the resistance of the drain/source contact and to the warping of the wafer caused by the special growth technique.

Abstract: The inflow performance prediction is very important to completion optimization of slanted wells. A reservoir/wellbore coupling model for slanted wells in anisotropic parallelepiped reservoirs considering wellbore pressure drop is presented based on source function method and superposition principle and solution methodology is described. On this basis, the inflow behavior of a slanted well in an anisotropic, infinite slab reservoir with impermeable top and bottom boundaries is investigated. Potential drop in the wellbore can cause flux difference, which is greatest under isotropic, and decreases with vertical anisotropy. Well productivity decreases with vertical anisotropy and the decrease is more significant for larger inclination angles than for smaller ones. Well inclination angle has a greater influence on inflow performance of wells in higher-anisotropy reservoirs than in lower-anisotropy ones and should be determined cautiously in the reservoir engineering design.

Abstract: With ShapeMetriX3D rock non-contact measuring technology, structural planes’ distribution of MiaoGou iron mine slope is got. Then, the Mont-Carlo method is used to create equivalent fracture network, with that scale effects and anisotropic properties of rock mass are studied by RFPA2D, considering different scales and directions in statistical window. The results show that both deformation modulus and the strength of the rock mass’s REV are 2.5 m. Furthermore, the strength ratio of filler to rock (K) and the strength of the rock mass fit the logarithmic relationship in rough, while the elastic modulus ratio of filler to rock (M) and the strength of the rock mass fit the linear relationship in rough. The strength of no joints rock mass is much stronger than three times of the strength of jointed rock mass, but the rock mass elastic modulus of no joints is less than 1.6 times of the elastic modulus of jointed rock mass. The research results are directive and have reference value for the study of anisotropy mechanical parameters of rock mass engineering.