Papers by Keyword: Anisotropy

Abstract: Sapphire has high mechanical strength at high temperatures and high pressure. Thus, micro devices made of sapphire are expected to be used in extreme environments such as aerospace, defense and marine. Then, the machining technology is required for manufacturing of 3 dimensional shapes. The paper discusses the micro cutting process of sapphire to determine the applicable cutting parameters in planing and milling. First, the critical stress at which crack initiation occurs is measured in the indentation test with detecting AE signal. The critical stress of sapphire is beyond 22.6 GPa, which is much higher than those of glasses. Then, the critical depths of cut, maximum depths of cut in which crack-free surfaces were finished, were measured in cutting of r crystal plane. The critical depth of cut is maximized when the cutting is performed in a crystal axis direction. In milling of sapphire, adhesion of chip onto the surface finish should be considered as well as brittle fracture. In milling of r crystal plane, the surface finish is improved better than those of the other crystal planes. Adhesion of material can also be controlled by supplying lubrication.

Abstract: A problem of identification of a single defect (a crack, a cavity or an inclusion) in an anisotropic, linear elastic body using boundary measurements is considered. An analytical solution of the problem of ellipsoidal defect identification in an infinite elastic solid is presented in the conditions when arbitrary constant stresses are applied at the infinity and the loads and displacements are known on a closed surface, containing the defect inside. The problem is solved using reciprocity gap functional method. The obtained analytical solution is used for solving the problem of ellipsoidal defect identification in a bounded elastic body by means of the results of one static test. It is assumed that the loads and displacements are measured on the external boundary of the body. Numerical examples illustrating efficiency of the developed method are considered. Stability of the results relative to the noise in the data and variation of the defect shape is studied.

Abstract: It is difficulty to make physical experiment for compressive experiment of rock with a natural interlayer I Natural interlayer affect greatly on mechanical property of rock. In this paper, Rock Failure Process Analysis Code RFPA is used to simulate influence of natural interlayer to compressive strength of rock by numerical simulation under compression. Through numerical simulation complete stress strain curve and peak load can be obtained for compressive experiment of rock with a natural interlayer. RFPA can be effectively used to investigate anisotropy of compression for rock with natural interlayer under different confining pressure. Numerical simulation show that anisotropy of compressive strength of rock with a natural interlayer varies with inclination of natural interlayer, as the confining pressure increase, the compressive strength, the plasticity and ductility increase for rock with a natural interlayer. That provides new method to analyze and investigate mechanical behavior for multilayer composite material such as rock mass with a natural interlayer，finally Index of Anisotropy for rock with a natural interlayer are put forward

Abstract: The three-dimensional roughness characteristics of the tensile granite joint surfaces are studied. Firstly, the tensile granite joints are prepared by splitting cubic granite blocks, and the triangular networks of the joint surfaces are established based on the topographic data collected by laser scanner. Then, the roughness characteristics of the two-dimensional profiles in different positions and different directions are studied. It proves that the roughness of the tensile granite joint surface is position and direction depended, and the roughness parameters based on the profiles are inadequate to characterize the roughness of the three-dimensional joint surfaces. Some new roughness parameters to characterize the three-dimensional joint surfaces are finally calculated on the basis of the triangular networks, these parameters can reflect the spatial and anisotropic characteristics of the joint surfaces. The results in this paper will lay the foundation for further study of the roughness characteristics and mechanical properties of the tensile rock joints.

Abstract: The development of stress-induced anisotropy in clay which was not only decided by the maximum stress endured before, but mainly lied on the stress route that reaching the maximum stress point of clay. The development or disappearance means of stress-induced anisotropy of normally consolidated clay, anisotropic consolidation clay and over-consolidated clay with different stress history are analyzed by experiments. Additionally, the effect of stress-induced anisotropy on deformation is also analyzed.

Abstract: Anisotropy of CP-Ti sheet in cold deep drawing was investigated by means of experiments. The as-received blank showed remarkable anisotropy due to the existence of the spilt basal texture. Deformation intensified the anisotropy in the distributions of wall thickness and ears, and mechanical properties after drawing. The micro-mechanism causing anisotropy of CP-Ti was analyzed. Then, methods for the improvements of anisotropy were brought out as profile optimization of the initial blank and heat treatment on the finished part at 650 °C for 1 hour.

Abstract: As the matter of fact, the soil in all models of the base is considered as a homogeneous isotropic body, ttherefore, existing models of isotropic elastic strata near the buildings does not allow to consider the actual properties of soils: their small-layered structure, the inclination of layers, anisotropy and heterogeneity, in addition it does not take into account the location of objects relative to the plane of the strike of the inclined layers. This article describes the anisotropic (transtropic) calculated elastic model of a complex system of "ground-foundation-structure basis", which most adequately reflects the characteristics of deformation and taking into account the diversity of the elastic properties in different directions relative to the plane of small fibers.

Abstract: The velocities of shear waves propagating along radial direction of birch and elmwood specimens are measured in order to study the effect of anisotropy on shear wave velocity. The relationship between the shear wave velocity and the oscillation direction is examined by rotating an ultrasonic sensor. The results indicate that the effect of anisotropy on shear wave velocity in birch and elmwood specimens is similar to Japanese magnolia specimen. When the oscillation direction of the shear wave corresponds to the certain anisotropic direction of the wood specimen, the shear wave velocity decreases sharply and the relationship between shear wave velocity and rotation angle tends to become discontinuous. The intrinsic birefringence due to the anisotropy of birch and elmwood woods is observed. Their texture anisotropies are strong. In an isotropic nylon, on the contrary, the value of shear wave velocity was similar to a circular ring. This investigation is significant meanings in architectural and civil engineering field.

Abstract: The optical properties of single crystals of the hexagonal manganites RMnO₃ (R = Ho, Tm, Yb) have been investigated by spectroscopic ellipsometry in the spectral range 0.6-5.0 eV. The measurements show a strong anisotropy of the diagonal elements of the dielectric tensor. It has been demonstrated that the optical absorption edge for the polarization Ec was determined by the intense band of O(2p)Mn (3d) transition centered near 1.6 eV, whereas this band for the polarization Ec was strongly suppressed and shifted toward higher energies by 0.15-0.20 eV. The spectral dependences of the ε₁(E) and ε₂(E) for HoMnO₃, TmMnO₃ and YbMnO₃ single crystals were qualitatively similar. The broad absorption band at E<1.0 eV clearly appears at the energies below the fundamental absorption edge of all of study compounds. It is possible, the origin of the near-infrared ε₂(E) absorption is associated with 4f-4f transitions of R³⁺ ions.

Abstract: The influence of powder particle size on behaviour of hot plastic deformation, structure and magnetic properties of Nd–Fe–B die-upset magnets have been examined. It was found, that powder particle size strongly affected plastic properties of material during hot deformation process. Precursors made of powder with the smallest particles (d < 32 μm) shown bigger plastic resistance than those made of powder with the larger ones (32 – 88 or 88 – 350 μm). For the same pressing force and temperature, applied within hot plastic deformation process, precursors made of the smallest particle powder allowed to obtain only 56 % deformation, while the another, made of larger particle powder: 65% deformation.