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Orientation Distribution (orientation + distribution)

Distribution by Scientific Domains

Polymers and Materials Science	58%

Terms modified by Orientation Distribution

orientation distribution function

Selected Abstracts

In Situ SEM Observation and Analysis of Martensitic Transformation During Short Fatigue Crack Propagation in Metastable Austenitic Steel,

ADVANCED ENGINEERING MATERIALS, Issue 4 2010
Ulrich Krupp
Abstract High cycle fatigue (HCF) life of metastable austenitic steels is governed by the ability of the parent austenite phase to transform into ,, martensite via metastable , martensite. The mechanism of this strain-induced transformation is closely related to the grain size, the crystallographic orientation distribution, as well as to amplitude, and cyclic accumulation of plastic strain. Aim of the present study is to identify and to quantitatively describe the basic principles of strain-induced martensite formation by means of in situ cyclic deformation experiments in a scanning electron microscope (SEM) in combination with electron back-scattered diffraction (EBSD) and numerical modeling using a boundary element approach. It was shown that during HCF loading martensite formation is inhomogeneous and not directly linked with crack initiation. Only when the fatigue crack propagates by operating multiple slip systems, the cyclic plastic zone exhibits martensitic transformation. [source]

Pole figure analysis of mineral nanoparticle orientation in individual trabecula of human vertebral bone

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2003
Daniel Jaschouz
The spongious interior of human vertebral bone consists of interconnected trabecula with a thickness of about 0.2 mm. The texture of the bone material, a collagen-mineral nanocomposite, was studied within single trabecula by collecting two-dimensional small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) data exactly at the same specimen positions with an X-ray beam of 0.2 mm diameter. Three-dimensional information was reconstructed by combining measurements with different specimen orientations. The XRD data, and for the first time also the SAXS data, were subjected to a pole figure analysis. The method provides a quantitative description of the crystallographic orientation distribution as well as the morphological orientation distribution of the plate shaped nanoparticles, both with respect to the orientation of the investigated trabecula. As a main result it could be shown that a fibre-texture exists in the trabecula, and that the plate shaped nanoparticles are aligned with the lamellae within the trabecula. [source]

Crystallization, orientation morphology, and mechanical properties of biaxially oriented starch/polyvinyl alcohol films

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Jing Wang
Abstract Biaxially oriented starch/polyvinyl alcohol (PVA) films were prepared by stretching starch/PVA blend precursor films that were fabricated by extrusion casting via a twin-screw extruder. Investigations on crystallization, orientation morphology, and mechanical properties of extrusion cast and stretched starch/PVA films were carried out by using differential scanning calorimetry, scanning electron microscope, wide angle X-ray diffraction (WAXD), and tensile testing. The fresh extrusion-cast starch/PVA films, which were almost amorphous, can crystallize spontaneously when aged at room condition. A good compatibility between starch and PVA was obtained by extrusion-casting technology. The well-developed molecular orientation, which did not occur along the machine direction during the extruding process, was observed in stretched film samples. Stretching unaged films can induce crystallization and the orientation of crystalline structures during stretching, resulting in the changes in diffraction peaks of WAXD patterns. The effect of stretch ratio and the orientation distribution in the plane of the film on mechanical properties of stretched films was studied, and the equal biaxially oriented films were found to exhibit in-plane isotropy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Orientational analysis of planar fibre systems observed as a Poisson shot-noise process

JOURNAL OF MICROSCOPY, Issue 1 2007
SALME KÄRKKÄINEN
Summary We consider two-dimensional fibrous materials observed as a digital greyscale image. The problem addressed is to estimate the orientation distribution of unobservable thin fibres from a greyscale image modelled by a planar Poisson shot-noise process. The classical stereological approach is not straightforward, because the point intensities of thin fibres along sampling lines may not be observable. For such cases, Kärkkäinen et al. (2001) suggested the use of scaled variograms determined from grey values along sampling lines in several directions. Their method is based on the assumption that the proportion between the scaled variograms and point intensities in all directions of sampling lines is constant. This assumption is proved to be valid asymptotically for Boolean models and dead leaves models, under some regularity conditions. In this work, we derive the scaled variogram and its approximations for a planar Poisson shot-noise process using the modified Bessel function. In the case of reasonable high resolution of the observed image, the scaled variogram has an approximate functional relation to the point intensity, and in the case of high resolution the relation is proportional. As the obtained relations are approximative, they are tested on simulations. The existing orientation analysis method based on the proportional relation is further experimented on images with different resolutions. The new result, the asymptotic proportionality between the scaled variograms and the point intensities for a Poisson shot-noise process, completes the earlier results for the Boolean models and for the dead leaves models. [source]

Preferred Orientation of Bi4Ti3O12 Thick Film

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007
Yoshiaki Kinemuchi
The preferred orientation of thick films prepared by paste printing is rarely observed because of their bulky polycrystalline nature. We found that a Bi4Ti3O12 thick film with a thickness of ca. 20 ,m showed c -axis-preferred orientation. Initially, the texture of the screen-printed film was found to have a random orientation, which was attributed to the equiaxed particle shape of the raw powder synthesized by the co-precipitation method. During subsequent heating, c -axis orientation emerged in which the degree of orientation was proportional to the film density. Analysis of the orientation distribution revealed that the progress of texturing was attributed to the film deformation, indicating that anisotropic shrinkage and morphological changes in particles during heating influenced the preferred orientation. [source]

Three-dimensional fiber orientation in vibration welded joints of glass fiber reinforced polyamide-6

POLYMER COMPOSITES, Issue 9 2008
Musa R. Kamal
A technique was developed to obtain the three-dimensional distribution of fiber orientation in vibration-welded joints of polyamide-6 (PA-6) reinforced with 30 wt% glass fibers. The heat-affected zone (HAZ) of fiber-reinforced PA-6 was successfully revealed by polishing and etching the vibration welded joints. Examination with the polarized light microscope in the reflection mode showed detailed microstructure domains, including the bulk crystalline zone and the HAZ. Experimental elliptical fiber cross-section images were used to obtain second order orientation tensors, thus providing a quantitative description of the three-dimensional fiber orientation distribution. The fibers in the HAZ were reoriented towards the squeeze flow direction, when compared with the bulk phase. Low welding pressure does not necessarily produce a more favorable fiber orientation in the tensile direction than high welding pressure. High welding pressure and low amplitude promote fiber reorientation in both the squeeze flow and tensile (weld thickness) directions. Overall, it was found that, at 30% fiber content, vibration-welded joints of injection molded fiber-reinforced PA-6 are weaker than vibration-welded joints in unreinforced injection molded samples. The fibers in the former do not undergo sufficient reorientation to influence weld strength in the tensile direction. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source]

Fiber orientation control of short-fiber reinforced thermoplastics by ram extrusion

POLYMER COMPOSITES, Issue 5 2003
Yukio Sanomura
In this study we examine the fiber orientation distribution, fiber length and Young's modulus of extruded short-fiber reinforced thermoplastics such as polypropylene. Axial orientation distributions are presented to illustrate the influence of extrusion ratio on the orientation state of the fibrous phase. Fibers are markedly aligned parallel to the extrusion direction with increasing extrusion ratio. The orientation state of extruded fiber-reinforced thermoplastics (FRTP) is almost uniform throughout the section. The control of fiber orientation can be easily achieved by means of ram extrusion. Experimental results are also presented for Young's modulus of extruded FRTP in the extrusion direction. Young's modulus follows a linear trend with increasing extrusion ratio because the degree of the molecular orientation and the fiber orientation increases. The model proposed by Cox, and Fukuda and Kawada describes the effect of fiber length and orientation on Young's modulus. The value of the orientation coefficient is calculated by assuming a rectangular orientation distribution and calculating the fiber distribution limit angle given by orientation parameters. By comparing the predicted Young's modulus with experimental results, the validity of the model is elucidated. The mean fiber length linearly decreases with increasing extrusion ratio because of fiber breakage due to plastic deformation. There is a small effect on Young's modulus due to fiber breakage by ram extrusion. [source]

Processing of short-fiber reinforced polypropylene.

POLYMER ENGINEERING & SCIENCE, Issue 1 2000

An experimental investigation of the processing of glass fiber reinforced polypropylene is presented. Final fiber orientation distribution, fiber distribution in filament sections, rheological properties, final fiber length distribution and surface morphology were analyzed. This analysis was done taking into account the quantity of fibers and their interactions and flow conditions. The final fiber orientation increased when shear rate increased and fiber concentration decreased. Moreover, inhomogeneities in fiber distribution increased as the concentration of fibers decreased. The density profile showed a significant variation with fiber concentration, but it was not dependent on the shear rate applied. The viscosity showed a linear dependence with shear rate. The average fiber length and the breadth of this distribution decreased with the increasing fiber concentration and extrusion rate. The extruded filament surface showed minor roughness when the shear rate increased or when the fiber concentration decreased. The results of this experimental characterization give useful information to determine the influence of the processing variables on the final properties of short-fiber reinforced polypropylene and constitutes the first part of a more ambitious project that also includes the development of a modeling strategy of the processing behavior for short-fiber composites. [source]

Transformations for monoclinic crystal symmetry in texture analysis

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2009
Siegfried Matthies
Monoclinic crystals can be described in two settings: in the first setting the C2 rotation axis is parallel to the z axis and in the second setting it is parallel to the y axis. Transformations of lattice parameters, Miller and zone indices, and atomic coordinates is straightforward; the situation is far more complex for texture analysis with orientation distributions and corresponding representations. This article gives explicit transformations that need to be applied, not only for texture analysis but also for calculations of physical properties of materials with preferred orientation. In texture research the relationship between the Cartesian crystal coordinate system and the unit cell must be unambiguously defined and a uniform convention is desirable. [source]

Evaluation of equatorial orientation distributions

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2006
W. Ruland
Two conflicting methods reported in the literature [Kratky (1933). Kolloid Z.64, 213,222; Leadbetter & Norris (1979). Mol. Phys.38, 669,686] for the relationship between axial orientation distributions and equatorial intensity profiles are analyzed. Both methods are in common use by their respective proponents for the evaluation of scattering patterns with preferred orientation under rotational symmetry. The correctness of these methods is assessed, and the consequences of the findings are discussed. [source]