Papers by Keyword: Orientation Distribution Function

Abstract: Graphite is a versatile material which is also used in various load bearing applications such as thrust bearings and dies for mechanical pressing such as hot pressing. Natural graphite has anisotropic layered structure which reduces its (compressive) strength in axes which are not parallel to c-axis. To increase strength, isotropy is introduced in graphite structure by breaking down its layers and minimizing grain size. We performed an in-depth characterization of relative aniostropy in graphite using pole figure density mapping. Locally available graphite samples were characterized by XRD and pole figures/3-D orientation distribution function (ODF). SEM and hardness testing were also performed to substantiate the pole density method. Results show that it is possible to characterize (qualitative/quantitative) isotropy or lack thereof in graphite by correlating it with the distribution of crystallinity/pole density mapping of (002) poles and 3D ODF figures.

Abstract: The variation of microstructure of Ti-IF steel of extra deep drawing grade, which having a 83%cold-rolled deformation under simulated batch annealing process at temperature ranging from 480°C to 750°C, was studied by using optical microscopy, X-ray diffraction (XRD) and metallographic micro-hardness tester. The evolution of texture during the recrystallization process was analyzed by Orientation Density Function (ODF). The results show that, the recrystallization temperature of experimental steel is 620-630°C, and the recrystallization process can be accomplished within 1h at660°C. Four major textures after cold rolling are observed as follows,{001}<110>, {111}<110>, {111}<112> and {112}<110>, respectively. At the early stage of recrystallization annealing, texture evolves from {111} toγ-{111}, which is quite beneficial to achieve high deep drawing performance,the texture {001}<110> and {112}<110> change marginally. as the annealing temperature rises up to 720°C, texture {001}<110> and {112}<110> change into fiber textureγ-{111}. After annealing,{111}<112> and {111}<110> textures become the two main types.

Abstract: The effect of cold rolling and annealing treatments in two temperatures, 800°C and 900°C on texture formation in duplex steel (X60MnAl30-9) was examined. Texture measurements were carried out using X-ray diffraction and Schulz reflection technique. The mechanical properties i. e. 0.2% proof stress, ultimate tensile strength and elongation were measured for each experimental conditions. It was found that ferrite was characterized by the orientations of a fibre which could be found in cold rolling state and also after the annealing in both temperatures. The weak orientations close to g fibre were observed after the annealing. The cold rolling texture of austenite was a typical texture of cold rolled fcc metals. No significant changes in texture of austenite after the annealing treatments were found.

Abstract: This paper described the application of a diffraction system based on X-ray area detector on pole figure measurement as well as corresponding computation of orientation distribution functions and the principle of rapid measurement texture. The impact of calculates the orientation distribution function on the conditions of the two-dimensional X-ray diffraction was analyzed; this was illustrated by an example of deep drawing steel sheets texture measurement. ̙̈́˰͇̱̓˰̶̴̿̾ͅ˰̸̱̈́̈́˰̷̱̹͂̿̈́̈́̾˰̸̵̈́˰͇̈́̿˽̴̵̹̹̱̼̽̾̓̿̾˰̴̵̵̳̈́̈́̿͂˰̈́̿˰̸̵̈́˰̵̱̹̱̀̀͂̿̀͂̈́˰̂θ position then fix it, reduce the sample rotation; the texture determination time can be significantly reduced. Reduce the Measuring range of angle χ˰̴̱̾ φ˰̴̵̿̓˰̾̿̈́˰̶̶̵̱̳̈́˰̸̵̈́ calculation of orientation distribution function, it also can significantly reduce the measurement of diffraction data. Several technical problems appeared on the on-line determination of texture based on an X-ray two-dimensional detector system and the possibility to improve the measurement speed and accuracy in the industrial production applications were then discussed.

Abstract: Nonwoven fabrics are web structures of randomly-oriented fibres, bonded by means of mechanical, thermal or chemical techniques. This paper focuses on nonwovens manufactured with polymer-based fibres and bonded thermally. During thermal bonding of such fibres, as a hot calender with an engraved pattern contacts the fibre web, bond spots are formed by melting of the polymer material. As a result of this bonding process, a pattern of bond points connected with randomly oriented polymer-based fibres form the nonwoven web. Due to their manufacturing-induced composite microstructure and random orientation of fibres, nonwovens demonstrate a complex mechanical behaviour. Two distinct modelling approaches were introduced to simulate the non-trivial mechanical response of thermally bonded nonwovens based on their planar density. The first modelling approach was developed to simulate the mechanical behaviour of high-density nonwovens, and the respective fabric was modelled with shell elements with thicknesses identical to those of the bond points and the fibre matrix having distinct anisotropic mechanical properties. Random orientation of individual fibres was introduced into the model in terms of the orientation distribution function in order to determine the material’s anisotropy. The second modelling approach was introduced to simulate low-density nonwovens, and it treated the nonwoven media as a structure composed of fibres acting as truss links between bond points.

Abstract: Present work describes the evolution of microstructure and texture in W-26Ni-26Fe-13Co and W-28Ni-12Fe-10Co alloys during cold rolling. These alloys consist of two phases i.e. W-base (bcc) and matrix (fcc) in sintered and cold rolled conditions. Microchemistry obtained by electron Probe Micro Analyser (EPMA) clearly indicates that the extent of alloying is very less in W phase. The matrix phase mainly consists of Ni, Fe Co and W. The development of texture in both the W and matrix during cold rolling has been described in terms of α, γ and β fibres for bcc and fcc phases, respectively.

Abstract: Even anisotropic superplastic flow, which is a result of an elongated grain shape and texture, can lead to extreme elongations to fracture (superplasticity). Therefore, to identify the mechanisms of deformation present during superplastic flow alone, the effects of the microstructure should be eliminated first. Using an Al 5083 alloy, in which an equi-axed microstructure is present from the beginning, it is shown that grain boundary sliding, accompanied by grain rotations, is the rate controlling mechanism.

Abstract: Having a unique microstructure, nonwoven fabrics possess distinct mechanical properties, dissimilar to those of woven fabrics and composites. This paper aims to introduce a methodology for simulating a dynamic response of core/sheath-type thermally bonded bicomponent fibre nonwovens. The simulated nonwoven fabric is treated as an assembly of two regions with distinct mechanical properties. One region - the fibre matrix – is composed of non-uniformly oriented core/sheath fibres acting as link between bond points. Non-uniform orientation of individual fibres is introduced into the model in terms of the orientation distribution function in order to calculate the structure’s anisotropy. Another region – bond points – is treated in simulations as a deformable bicomponent composite material, composed of the sheath material as its matrix and the core material as reinforcing fibres with random orientations. Time-dependent anisotropic mechanical properties of these regions are assessed based on fibre characteristics and manufacturing parameters such as the planar density, core/sheath ratio, fibre diameter etc. Having distinct anisotropic mechanical properties for two regions, dynamic response of the fabric is modelled in the finite element software with shell elements with thicknesses identical to those of the bond points and fibre matrix.

Abstract: In this study, the orientation distribution function (ODF), which can be calculated from the pole figure data, was examined and tried in order to characterize the bulky morphology of primary solid phase of semi-solid slurry instead of erroneous 2D observation for the characterization of microstructure. Al-15wt%Cu alloys were electromagnetically stirred during the continuous cooling in the specially designed electromagnetic (EM) stirrer, which generates a rotating magnetic field, and the samples were prepared by interrupt-quenching semi-solid slurry at a solid-liquid region. Owing to EM stirring the temperature distribution of melt inside a crucible became uniformed compared with the case of unstirred melt and the normal dendritic structure was transformed to one consisting of the spherical and rosette shaped primary solid phase due to the fragmentation of the dendrites. Also by the effect of EM stirring the <110>//ND texture were still strongly developed, but the advancement of the orientations to lead <110>//ND texture became weaker, and the orientations to lead <100>//ND and <111>//ND texture were more strongly advanced in comparison with the unstirred case. Therefore the advancement of the texture became weak and so the tendency to random orientation was appeared due to the EM stirring. Therefore it was thought that the extent of random orientation could be valued for the characterization of bulky morphology of primary solid phase of semi-solid slurry.

Abstract: The mathematical method of the texture function restoration according to diffraction experiment is offered. The texture function is represented as superposition of standard texture functions with the identical dispersions, located on a regular three-dimensional grid in orientation space. Applicability of the method is shown by model examples and in an example of a cold rolled texture of a copper sheet.