Papers by Keyword: Orientation Distribution Function (ODF)

Abstract: Based on the principle of maximum entropy method (MEM), the particle swarm optimization (PSO) with inertia weight factor is efficiently applied for the orientation distribution function (ODF) representation on textured materials in this article. By this optimized algorithm with a faster rate of convergence, more appreciable calculation results have been obtained for complete orientation distributions (C-ODF) of the designated deep-drawing IF steel sheets with macro cubic-orthogonal symmetry. With reference to data processing, there need no more assumptions except that the system entropy approaches maximum. The calculation results are irrelevant to the sample compositions, texture components or their initial orientation distributions derived from three pole figures.

Abstract: A strong basal plane texture of AZ31 magnesium alloy was obtained by severe hot-rolling with three passes falling temperature. The effects of annealing time and annealing temperature on the evolution of texture at different layers were studied by means of X-ray texture analysis. The results showed that the orientation density of basal plane texture component was reduced greatly tending to dispersion with increasing annealing time and temperature. The hard orientation can be greatly weakened by softening annealing, the best basal plane orientation was obtained when the annealing time is 60min and the annealing temperature is 150~300°C. A texture gradient along thickness direction with annealing has been found in the sheet. The texture gradient was the lowest when the annealing time is 60min and the annealing temperature is 300°C.

Abstract: The exoskeleton of the crustacean Homarus americanus, the American lobster, is a biological multiphase composite consisting of a crystalline organic matrix (chitin), crystalline biominerals (calcite), amorphous calcium carbonate and proteins. One special structural aspect is the occurrence of pronounced crystallographic orientations and resulting directional anisotropic mechanical properties. The crystallographic textures of chitin and calcite have been measured by wide-angle Bragg diffraction, calculating the Orientation Distribution Function (ODF) from pole figures by using the series expansion method according to Bunge. A general strong relationship can be established between the crystallographic and the resulting mechanical and physical properties.

Abstract: Dental enamel is the most highly mineralised and hardest biological tissue in human body [1]. Dental enamel is made of hydroxylapatite (HAP) - Ca5(PO4)3(OH), which is hexagonal (6/m). The lattice parameters are a = b = 0.9418 nm und c = 0.6875 nm [1]. Although HAP is a very hard mineral, it can be dissolved easily in a process which is known as enamel demineralization by lactic acid produced by bacteria. Also the direct consumption of acid (e.g. citric, lactic or phosphoric acid in soft drinks) can harm the dental enamel in a similar way. These processes can damage the dental enamel. It will be dissolved completely and a cavity occurs. The cavity must then be cleaned and filled. It exists a lot of dental fillings, like gold, amalgam, ceramics or polymeric materials. After filling other dangers can occur: The mechanical properties of the materials used to fill cavities can differ strongly from the ones of the dental enamel itself. In the worst case, the filling of a tooth can damage the enamel of the opposite tooth by chewing if the interaction of enamel and filling is not equivalent, so that the harder fillings can abrade the softer enamel of the healthy tooth at the opposite side. This could be avoided if the anisotropic mechanical properties of dental enamel would be known in detail, hence then another filling could be searched or fabricated as an equivalent opponent for the dental enamel with equal properties. To find such a material, one has to characterise the properties of dental enamel first in detail for the different types of teeth (incisor, canine, premolar and molar). This is here exemplary done for a human incisor tooth by texture analysis with the program MAUD from 2D synchrotron transmission images [2,3,4].

Abstract: The crystal plasticity finite element method (CPFEM) is probably the method with the best potential to directly incorporate crystal anisotropy and its evolution into forming simulations. However, when it comes to the simulation of bulk materials, the representation of the crystal orientation distribution function (ODF), i.e. of the statistical texture, within the CPFEM framework becomes a key issue for the efficiency of the approach. In this work two different approaches for sampling the ODF are compared. The first is the so called Texture-Component-CPFEM, where the discretisation is based on the representation of the ODF by texture components. The second approach is based on the representation of the ODF by series expansion and uses a direct mapping of the ODF represented in the form of C-coefficients to individual orientations as needed by the CPFEM. Both methods are compared using the textures of Aluminum hot band as well as cold rolled material.

Abstract: For multi crystal materials, particularly multi-crystal metallic materials, it is unavoidable to make its crystal orientation change during the process. For instance, improving the property of soft magnetic materials should rely on the Cubic texture {100} <001>, but the property of the deep-draw sheet materials is closely related to its texture. Besides the material's composition, the crystal and the microstructure, the texture also takes a very important role in the properties of the materials [1, 2]. The positive pole figure analytic method is comparatively simple and intuitional. This is unquestionable in the texture analysis of cold-rolled samples, as in drawing sheet materials. It shows that the material orientation of isotropy or multiple weak textured materials is coexistent. The ODF analysis can be a good method for resolving this. In the study, the serial ODF analysis is used to analyze the property of nickel based alloys of drawing sheet materials considering different deformation amount, annealing temperature and annealing time in layers. In practice, it can be applied to production techniques.

Abstract: . Equal channel angular pressing (ECAP) is useful method to obtain the ultra-fine grained and the high hardened metal. The microstructure, the hardness, and the texture of the 1050 Al sheets by ECAP are changed by a severe shear deformation. The change of the microstructure, the hardness, and the texture were investigated on the 1050 Al sheets that were prepared by ECAP and annealing.