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Transverse Direction (transverse + direction)
Selected AbstractsThe eigenvalues of isolated bridges with transverse restraints at the end abutmentsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2010Nicos Makris Abstract This paper examines the eigenvalues of multi-span seismically isolated bridges in which the transverse displacement of the deck at the end abutments is restricted. With this constraint the deck is fully isolated along the longitudinal direction, whereas along the transverse direction the deck is a simple-supported beam at the end abutments which enjoys concentrated restoring forces from the isolation bearings at the center piers. For moderate long bridges, the first natural period of the bridge is the first longitudinal period, while the first transverse period is the second period, given that the flexural rigidity of the deck along the transverse direction shortens the isolation period offered by the bearings in that direction. This paper shows that for isolated bridges longer than a certain critical length, the first transverse period becomes longer than the first longitudinal period despite the presence of the flexural rigidity of the deck. This critical length depends on whether the bridge is isolated on elastomeric bearings or on spherical sliding bearings. This result is also predicted with established commercially available numerical codes only when several additional nodes are added along the beam elements which are modeling the deck in-between the bridge piers. On the other hand, this result cannot be captured with the limiting idealization of a beam on continuous distributed springs (beam on Wrinkler foundation),a finding that has practical significance in design and system identification studies. Finally, the paper shows that the normalized transverse eigenperiods of any finite-span deck are self-similar solutions that can be represented by a single master curve and are independent of the longitudinal isolation period or on whether the deck is supported on elastomeric or spherical sliding bearings. Copyright © 2009 John Wiley & Sons, Ltd. [source] Applicability of pushover methods for the seismic analysis of single-column bent viaductsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2008Tatjana Isakovi Abstract An overview of the applicability of a typical single-mode pushover method (the N2 method) and two typical multi-mode pushover methods (the modal pushover analysis (MPA) and incremental response spectrum analysis (IRSA) methods) for the analysis of single column bent viaducts in the transverse direction is presented. Previous research, which was limited to relatively short viaducts supported by few columns, has been extended to longer viaducts with more bents. The single-mode N2 method is accurate enough for bridges where the effective modal mass of the fundamental mode is at least 80% of the total mass. The applicability of this method depends on (a) the ratio of the stiffness of the superstructure to that of the bents and (b) the strength of the bents. In short bridges with few columns, the accuracy of the N2 method increases as the seismic intensity increases, whereas in long viaducts (e.g. viaducts with lengths greater than 500,m) the method is in general less effective. In the case of the analyzed moderately irregular long viaducts, which are common in construction design practice, the MPA method performed well. For the analysis of bridges where the modes change significantly, depending on the seismic intensity, the IRSA method is in principle more appropriate, unless a viaduct is torsionally sensitive. In such cases, all simplified methods should be used with care. Copyright © 2008 John Wiley & Sons, Ltd. [source] Seismic performance evaluation of steel arch bridges against major earthquakes.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2004Part 2: simplified verification procedure Abstract The performance-based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation and demand prediction procedures for civil engineering structures under earthquake excitations are of great significance. This work presents a displacement-based seismic performance verification procedure including capacity and seismic demand predictions for steel arch bridges and investigates its applicability. Pushover analyses is employed as a basis in this method to investigate the structure's behaviors. A failure criterion for steel members accounting for the effect of local buckling is involved and an equivalent single-degree-of-freedom (ESDOF) system with a simplified bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum demand of steel arch bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi-degree-of-freedom (MDOF) time-history analyses with Level-II design earthquake record inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clarified that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the steel arch bridge in the transverse direction, while insufficient for the longitudinal direction, which confirms the conclusion drawn in other structure types about the applicability of pushover analyses. Copyright © 2004 John Wiley & Sons, Ltd. [source] Molecular Auxetic Behavior of Epitaxial Co-Ferrite Spinel Thin FilmADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Matjaz Valant Abstract In functional oxide materials so-called molecular auxetic behavior is extremely rare. Here, it is reported in the CoFe2O4 spinel structure. A CoFe2O4 epitaxial thin film under compressive axial strain also reduces its cell dimensions in the transverse direction with a Poisson's ratio of ,0.85. A hinge-like honeycomb network in the spinel structure is identified as being responsible for the negative Poisson's ratio. This phenomenon has a substantial effect on the functional properties of CoFe2O4 and enables the construction of a new class of nano-devices. [source] A spline strip kernel particle method and its application to two-dimensional elasticity problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2003K. M. Liew Abstract In this paper we present a novel spline strip kernel particle method (SSKPM) that has been developed for solving a class of two-dimensional (2D) elasticity problems. This new approach combines the concepts of the mesh-free methods and the spline strip method. For the interpolation of the assumed displacement field, we employed the kernel particle shape functions in the transverse direction, and the B3 -spline function in the longitudinal direction. The formulation is validated on several beam and semi-infinite plate problems. The numerical results of these test problems are then compared with the existing solutions obtained by the exact or numerical methods. From this study we conclude that the SSKPM is a potential alternative to the classical finite strip method (FSM). Copyright © 2003 John Wiley & Sons, Ltd. [source] Quasi-static analysis of microstrip lines with variation of substrate thickness in transverse directionINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2003S. Khoulji Abstract This article is devoted to the analysis of microstrip lines printed on dielectric substrates with transversely varying thickness using the quasi-static approximation and the method of lines. Discretization lines of varying length, according to the layer thickness, are used and only the Laplace wave equation has to be solved. The numerical results presented herein permit the illustration of the effect of arbitrarily curved substrate interfaces along the transverse direction on the characteristics of the microstrip structures under consideration. The behavior of the per unit length parameters of these structures as a function of the shape of these substrates' cross section is studied in depth. Furthermore, the effects of the finite metallization thickness and losses are also investigated in detail. The results that are obtained are consistent with those published in the literature. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 194,205, 2003. [source] Effect of EVA as compatibilizer on the mechanical properties, permeability characteristics, lamellae orientation, and long period of blown films of HDPE/clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Juliano Marini Abstract Two ethylene-vinyl acetate (EVA) resins with 19% (EVA19) and 28% (EVA28) of vinyl groups were used as compatibilizers for nanocomposites of high-density polyethylene (HDPE) and nanoclays. Two nanoclays were also used, one with a nonpolar surfactant (C15A) and another with a polar surfactant (C30B). The HDPE/EVA19/C15A formed an intercalated structure, while the HDPE/EVA28/C30B had surfactant loss. Blown films of these compositions were produced. A two-phase morphology made of HDPE and EVA/nanoclay particles was observed, which was responsible for the increase in water vapor and oxygen permeability rates of the films. The elastic modulus E along the transverse direction of the films was higher than along the machine direction due to preserved orientation given by the spiral die; the lamellae orientation was measured by small-angle X-rays diffraction. The highest E was observed in the HDPE/EVA19/C15A film due to stronger interactions. The long period of the HDPE lamellas was not affected by the presence of the EVA and nanoclay. A model was proposed to explain the improvement in elastic modulus due to the processing conditions and components' interactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Morphologies and mechanical properties of HDPE induced by small amount of high-molecular-weight polyolefin and shear stress produced by dynamic packing injection moldingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Zhanchun Chen Abstract To better understand the effect of a small amount of high-molecular-weight polyethylene (HMWPE) on the mechanical properties and crystal morphology under the shear stress field, the dynamic packing injection molding (DPIM) was used to prepare the oriented pure polyethylene and its blends with 4% HMWPE. The experiment substantiated that the further improvement of tensile strength along the flow direction (MD) of high-density polyethylene (HDPE)/HMWPE samples was achieved, whereas the tensile strength along the transverse direction (TD) still substantially exceeded that of conventional molding. Tensile strength in both flow and TDs were highly enhanced, with improvements from 23 to 76 MPa in MD and from 23 to 31 MPa in TD, besides the toughness was highly improved. So, the samples of HDPE/HMWPE transformed from high strength and brittleness to high strength and toughness. The obtained samples were characterized via SEM and TEM. For HDPE/HMWPE, the lamellae of the one shish-kebab in the oriented region may be stretched into other shish-kebab structures, and one lamella enjoys two shish or even more. This unique crystal morphology could lead to no yielding and necking phenomena in the stress,strain curves of HDPE/HMWPE samples by DPIM. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Mullitization from a Multicomponent Oxide System in the Temperature Range 1200°,1500°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000Hyunho Shin Mullitization from a multicomponent oxide system (alumina,kaolin,quartz,feldspar,talc) was analyzed as a function of firing temperature from 1200° to 1500°C based on quantitative XRD and SEM. In the present study, whisker forms of mullite grew in three characteristic stages. In the first stage (1255°,1295°C), mullitization (nucleation) took place from glass via alumina dissolution into glass under the condition of no apparent change in glass content. The reaction in this stage was rate-limited by alumina dissolution into glass. Extensive mullitization occurred in the 1295°,1335°C range (second stage) directly from glass. Unlike in the sol,gel-based binary system, alumina dissolution into glass was not shown to be the rate-controlling mechanism during this extensive mullitization stage. Finally (>1335°C, third stage), the reaction was saturated, accompanied by an apparent decrease in glass consumption rate. The impingement of mullite whiskers by other whiskers and crystals was speculated to cause mullite to grow in the transverse direction, yielding a diminished reaction rate in the final stage. Mullitization stages in this work were compared with those of the alumina,silica binary system shown in the literature. [source] Speed- and topography-dependent boundary friction characteristics of steelLUBRICATION SCIENCE, Issue 8 2010Saiko Aoki Abstract A novel tribometer that undergoes significant changes at ultra-slow (>5.0,µm,s,1) to moderate (<20,cm,s,1) sliding speeds was developed in order to study the friction-speed characteristics of steel lubricated with oil. Three different surface topographies were applied to the specimens, and the friction characteristics with an additive-free base oil (MO91) and a stearic acid-formulated oil (StA/MO91) were studied to understand the effects of surface textures on the lubrication performance of an adsorbed molecular layer formed by StA. Friction reduction behaviour of the adsorbed layer observed in the transverse direction was attributed to microscopic hydrodynamic action that maintained the load-carrying performance of the adsorbed layer. Copyright © 2010 John Wiley & Sons, Ltd. [source] Morphology and High Modulus of Laminated Ultra-Drawn Polyethylene Films with Biaxial Orientation Prepared by Microwave HeatingMACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2007Mami Azuma Abstract To improve the poor mechanical properties of uniaxially ultra-drawn films along the transverse direction, lamination of two ultrahigh molecular weight polyethylene/ethylene dimethylaminoethyl methacrylate copolymer blend films was carried out in the rectangular elongation direction by a microwave heating method. The characteristics of the successful laminated films were analyzed theoretically and experimentally. The original orientation of the crystallites for the blend films was maintained perfectly after lamination, and the preferential directions intersected each other. The Young's modulus increased symmetrically with respect to the 45 ° direction. This is the first report concerning a drastic improvement of the Young's modulus in the transverse direction for films ultra-drawn along one direction. [source] Processability and Properties of Re-Graded, Photo-Oxidized Post-Consumer Greenhouse FilmsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Francesco Paolo La Mantia Abstract Summary: The recycling of post-consumer plastics leads, in general, to secondary materials having properties worse than those of the reclaimed material and certainly worse than those of the same virgin polymer. This is because of the degradation undergone by the objects during their use and because of the thermo-mechanical degradation undergone during the reprocessing operations. The change of the molecular architecture is responsible for this worsening of properties. The use of stabilizing systems can slow the degradation during the melt processing but cannot give any improvement of the final properties of the material. In order to enhance the properties of the recycled plastics, some rebuilding of the molecular structure is necessary. The use of suitable additives can enlarge the molecular weight distribution or can create branching and cross-linking during the melt processing of the photo-oxidized PE. The processability in film blowing and the mechanical properties of these secondary materials are reported in this work. The rheological behavior, the filmability and most of the mechanical properties of the secondary PE with the rebuilt molecular structure are better than those of the post-consumer material and similar to those of the virgin polymer. TS in the machine and in the transverse direction for all the samples extruded at 50 rpm. [source] Magnetically tunable microstrip linear resonator on polycrystalline ferrite substrateMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007Rajeev Pourush Abstract A low cost conventional half-wave microstrip linear resonator has been designed at 2 GHz central frequency and fabricated photolithographically by depositing metallic films on prepared LiMnTi polycrystalline ferrite substrate. Resonator characteristics have been examined by keeping it in the low biasing magnetic field values (from 0 to 298 Guass) applied in transverse direction of wave propagation and normal to ground plane. Tunability of 339 MHz (17%) was achieved which is the best reported so far for such a structure for low magnetic field values with a minimum insertion loss of 10.68 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2868,2870, 2007; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.22858 [source] VSOP polarization observations of the BL Lacertae object OJ 287MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001D. C. Gabuzda VLBI total intensity and linear polarization images of the BL Lacertae object OJ 287 have been obtained at using a global ground array and the HALCA orbiting antenna, and at two weeks earlier using the VLBA. In the ground-based 6-cm images, the source is dominated by a core,jet double structure the components of which are essentially unresolved. The baselines to the orbiting antenna resolve both of these compact components. In the VSOP images, the ground-based ,core' breaks up into several distinct components, demonstrating that this region is dominated by the contribution of bright, optically thin knots of jet emission. A very similar structure is observed in the 1.3-cm image. The magnetic field in the core is transverse, becomes longitudinal in the inner jet, then makes a sharp transition to a region of transverse field further from the core. This suggests that the field in the outer jet has become highly ordered in the transverse direction owing to the action of a shock; the physical nature of the extended region of longitudinal field closer to the core is not clear. The availability of nearly simultaneous observations with comparable resolution at widely spaced frequencies enabled detection of a ,90° rotation in polarization position angle for the core, owing to the transition from the optically thick (6 cm) to the optically thin (1.3 cm) regime. [source] Mapping of stress distribution in woven-fabric compositesPOLYMER COMPOSITES, Issue 8 2008E. Shady Mapping of the stress distribution in composite materials, both at the fiber/matrix interface and in the composite constituents, is important to understand the material mechanical response. Stress mapping can help predict composite behavior under certain stresses especially failure or delamination. In this work, two analytical models were proposed to map the stress distribution at fiber, matrix and fiber/matrix interface utilizing the concept of stress superposition. The first model dealt with the fiber in the longitudinal direction considering axisymmetric conditions. The second model addressed the fiber stress distribution in the transverse direction. Experimental data from four-point flexural tests of woven fabric composites was processed using the Graphical Integrated Numerical Analysis (pcGINA) to obtain the maximum stress in the target laminate and this value was used as the input for the two analytical models. The value for the maximum interfacial shear stress was calculated using the models and results were compared to pull-out fiber test values obtained from literature. Good agreement was observed between the model calculations and the literature data. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Real-time monitoring of fluorescence anisotropy and temperature during processing of biaxially stretched polypropylene film,POLYMER ENGINEERING & SCIENCE, Issue 4 2004Anthony J. Bur An optical sensor based on fiber optics has been developed to measure fluorescence anisotropy and temperature during processing of biaxially stretched polypropylene films. The sensor, containing optical fibers, polarizing elements and lenses, was mounted above the polypropylene film as it was processed in a tenter frame oven stretching machine. Fluorescence observations were made using the fluorescent dye, bis (di-tert butylphenyl) perylenedicarboximide (BTBP), which was doped into the resin at very low concentrations. To monitor biaxial stretching, fluorescence anisotropy measurements were carried out with light polarized in the machine and the transverse directions corresponding to the directions of biaxial stretching. Fluorescence based temperature measurements were obtained from the ratio of fluorescence intensities at 544 nm and 577 nm. A matrix of experiments involving three levels of stretch ratio in both the machine and transverse directions was undertaken. We observed significant differences between anisotropy in the machine and transverse directions that we attributed to the sequential stretching operation, i.e., the film was stretched in the machine direction first, followed by stretching in the transverse direction, and to film temperature and strain rate for each stretching operation. The result was uniformly higher anisotropies in the machine direction. Film temperature obtained from fluorescence corresponded to oven thermocouple measurements within 2°C. Polym. Eng. Sci. 44:805,813, 2004. © 2004 Society of Plastics Engineers. [source] Comparison of analytical and numerical methods for homogenization of nanotube-reinforced polymersPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Ina Schmidt Carbon nanotubes are increasingly getting impact as reinforcing material for polymer based nanocomposites. Hence, new modeling strategies are necessary to calculate the behavior of these materials. In the last years some attempts have been made using and developing classical micromechanical models. On the other hand numerical homogenization methods are available to tackle this problem. Examples for both types of modeling strategies are presented with focus on the nanotube geometry. The nanotubes are modeled as hollow tubes as well as as isotropic and transversely isotropic cylinders. As expected the results of numerical and analytical methods are identical for isotropic cylinder inclusions. Small deviations occur for transversely isotropic cylinders in transverse direction. In the case of hollow tube inclusions, the analytical models lead to lower stiffness values in transverse direction and for shear. The largest deviations occur for longitudinal shear with magnitudes smaller than 10%. In contrast the effort to get numerical results is enormous, so that the analytical models are still useful. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Properties of uniaxially stretched polypropylene filmsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2008Farhad Sadeghi Abstract Polypropylene (PP) films have been prepared through two different cast extrusion processes: one using a machine direction orientation (MDO) unit and the other stretching the films at the die under high cooling conditions (lab unit). Films for two PP resins different in molecular structure have been prepared using both processing techniques. The effect of the resin structure and the processing conditions on the film properties has been examined. It was found that the MDO unit generated a highly oriented fibrillar crystalline structure with a distribution of elongated thick fibrils while extrusion under high cooling conditions generated an oriented row nucleated lamellar structure. The films showed distinctive tensile responses in stretching, with a strong solid-elastic response for the oriented MDO films and a steady strain hardening after yielding for the sample obtained from lab unit cast extrusion. It was found that the strength in the transverse direction (TD) was particularly very low for the oriented MDO films made of the bimodal PP. The oxygen permeability was reduced with increasing draw ratio (DR) for the MDO films. The haze property for the MDO samples reduced to a plateau for DR up to 5 while clarity improved continuously with DR. Des films de polypropylène ont été préparés dans deux procédés d'extrusion différents: l'un utilise une unité MDO (orientation dans la direction de la machine) et l'autre l'étirement des films à la filière dans des conditions de refroidissement intense (unité de laboratoire). Des films de polypropylène (PP) venant de deux résines de structure moléculaire différente ont été préparés à l'aide de ces deux techniques de mise en forme. L'effet de la structure de la résine et des conditions de mise en ,uvre sur les propriétés des films a été examiné. On a trouvé que l'unité MDO donne une structure cristalline fibrillaire hautement orientée avec une distribution de fibrilles épaisses allongées, tandis que l'extrusion sous refroidissement intense donne une structure lamellaire nucléée orientée en rangée. Les films montrent des réponses en contraintes à l'étirement distinctes, avec une forte réponse élastique solide pour les films MDO orientés et un écrouissage stable après déformation irréversible pour l'échantillon obtenu par extrusion avec l'unité de laboratoire. On a trouvé que la tenacité dans la direction transverse était particulièrement faible pour les films MDO orientés faits de PP bimodal. La perméabilité à l'oxygène a été réduite avec l'augmentation du rapport d'étirage pour les films MDO. La propriété de perte de transparence légère pour les échantillons MDO montre un plateau pour un rapport d'étirage allant jusqu'à 5 tandis que la clarté s'améliore continuellement avec le rapport d'étirage. [source] Properties of blends of linear and branched polypropylenes in film blowingTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2008Yunli Fang Abstract The effect of blending a long-chain branched polypropylene (LCB-PP) with a linear polypropylene (L-PP) on the processability and properties of blown films was investigated. The rheological data revealed that blending an LCB-PP with an L-PP improved the elongational properties and the bubble stability, but a severe drop in the mechanical strength was observed for the blends. The most deteriorating effect was the reduction in the elongation at break in tensile tests carried out in the transverse direction (TD), where no yielding behaviour was observed for the blends. On a étudié l'effet du mélange d'un polypropylène ramifié à chaînes longues (LCB-PP) avec un polypropylène linéaire (L-PP) sur la processabilité et les propriétés des films soufflés. Les données rhéologiques révèlent que le mélange d'un LCB-PP avec un L-PP améliore les propriétés d'élongation et la stabilité des bulles, mais une chute importante de la force mécanique a été observée pour les mélanges. L'effet le plus détériorant est la réduction de l'élongation à la rupture dans les essais de traction dans la direction transverse, où aucun comportement plastique n'a été observé pour les mélanges. [source] Origin and propagation of spontaneous excitation in smooth muscle of the guinea-pig urinary bladderTHE JOURNAL OF PHYSIOLOGY, Issue 2 2001Hikaru Hashitani 1The origin and propagation of waves of spontaneous excitation in bundles of smooth muscle of the guinea-pig bladder were examined using intracellular recording techniques and visualization of the changes in the intracellular calcium concentration ([Ca2+]i). 2Bladder smooth muscle cells exhibited spontaneous transient increases in [Ca2+]i which originated along a boundary of each smooth muscle bundle and then spread to the other boundary with a conduction velocity of 2.0 mm s,1. 3Spontaneous increases in [Ca2+]i were always preceded by action potentials. Nifedipine (10 ,M) abolished increases in both [Ca2+]i and action potentials. Caffeine (10 mM), ryanodine (50 ,M) and cyclopiazonic acid (10 ,M) reduced the amplitude of the associated increases in [Ca2+]i without preventing the generation of action potentials. 4Spontaneous action potentials had conduction velocities of 40 mm s,1 in the axial direction and 1.3 mm s,1 in the transverse direction. The electrical length constants of the bundles of muscle were 425 ,m in the axial direction and 12.5 ,m in the transverse direction. 5Neurobiotin, injected into an impaled smooth muscle cell, spread more readily to neighbouring cells located in the axial direction than those located in the transverse direction. The spread of neurobiotin was inhibited by 18,-glycyrrhetinic acid (18,-GA, 40 ,M), a gap junction blocker. 6Immunohistochemistry for Connexin 43 showed abundant punctate staining on the smooth muscle cell membranes. 7These results suggested that spontaneous action potentials and associated calcium waves occur almost simultaneously along the boundary of bladder smooth muscle bundles and then propagate to the other boundary probably through gap junctions. [source] The Characteristics of Polyethylene Film for Stretch and Cling Film ApplicationsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004C.M. Small Part I. A range of polyethylene films were prepared from metallocene linear low density polyethylene (m-LLDPE), linear low density polyethylene (LLDPE) and ultra low density polyethylene (ULDPE) resins, containing 0 and 8% polyisobutylene (PIB). FTIR, DSC and mechanical analysis techniques were used to investigate the effect of co-monomer type, density and melt flow index (MFI) on the mechanical performance, orientation and crystallinity of these films. The study established that co-monomer type and MFI were the greatest factors influencing mechanical performance and crystallinity. Crystallinity was found to be the most influential factor governing PIB migration in these films and this in turn was related to polymer type, density and MFI, High MFI, octene co-monomer films exhibited the highest orientation, tear resistance and tack strength and would therefore be suitable for stretch film applications. Ultra low-density polymers gave relatively low tack strength and poor overall mechanical performance. Part II. A range of ethyl vinyl acetate (EVA)/m-LLDPE/EVA co-extruded films was manufactured, with vinyl acetate (VA) co-monomer content of 6, 12 and 18% and PIB content from 0,20%. The films were aged at 45d,C for up to 28 days, to enable tack (cling) development. The results show that film tack strength improved significantly with ageing. Increased VA concentration in the surface layer also showed significant improvement in film tack strength. The film tensile strength, elongation and tear properties in both machine direction (MD) and transverse direction (TD) were not significantly affected by increase in PIB concentration. However, increased VA content showed slight improvement in MD mechanical performance of the films, TD properties were relatively unaffected. Films with 12 to 18% VA in the surface layers produced high surface tack film and the mechanical performance of these films were comparable to mono-layer polyethylenes. These films are suitable for stretch wrap applications and have reduced the overall concentrations of tack additives, though high VA films were more difficult to process. [source] Biomechanical models for clinical data analysis of pressure-volume relationship in the human eyeACTA OPHTHALMOLOGICA, Issue 2009S BAUER Purpose To develop mechanical models describing the pressure-volume relationship for the human eye and to compare the results obtained with clinical data in order to find out which mechanical characteristics affect this relationship most significantly. Methods The fibrous coat is treated as a connected elastic shell consisting of two spherical segments with different radii and mechanical characteristics. The dependence of the intraocular pressure on the volume is analyzed using three different models in which the sclera and the cornea are modeled (1) by soft shells; (2) by transversally isotropic shells with small tension modules in the transverse direction; and (3) by 3D elastic solids. The models are studied analytically and numerically, the latter using FEM ANSYS software. Results The results are obtained over a wide range of parameters using all three models. Conclusion The models proposed predict a generally nonlinear relationship between the intraocular pressure and volume. The parameters of both the sclera and the cornea affect this relationship, the role of the sclera being more important. In the first approximation the simple soft shell model is in good agreement with the clinical data. [source] Core loss estimation in three-phase transformer using vector hysteresis model and classical loss model incorporated in 2D magnetodynamicsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2003O. Deblecker This paper deals with the computation of the magnetic field and core loss in a three-phase three-limb transformer at no-load. The computational algorithm consists of the vector hysteresis model incorporated in 2D magneto-dynamics via the differential reluctivity tensor. The hysteretic nonlinearity is handled by a simple iteration scheme. The eddy-current losses in the laminated steel core are accounted for by considering an additional conductivity matrix in the FE equations. The magnetisation-dependant vector Preisach model with an analytical expression for the distribution function is adopted for describing the hysteretic constitutive law in the rolling and transverse directions of the laminations. The parameters and mean field term are fitted on the basis of a set of BH-symmetric (quasistatic) loops. Numerical results are presented that confirm the effectiveness of the proposed method for the no-load simulation of the transformer in the transient and the steady-states. [source] Predicting the J integral fracture toughness of Al 6061 using the small punch testFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9 2007E. BUDZAKOSKA ABSTRACT The 6000 series aluminium alloys (Al,Mg,Si systems) are commonly used as medium-strength structural materials; in particular, the 6061 (Al,1Mg,0.6Si) alloy is widely utilized as a general-purpose structural material due to its excellent formability and corrosion-resisting capabilities. The objective of this study was to obtain a correlation between the small punch (SP) test estimated equivalent fracture strain (,qf) and fracture toughness (J1C) property for 6061 aluminium, and determine its viability as a non-destructive fracture toughness test technique for remaining life assessment of in-service components. Samples of 6061-T6 aluminium were cut from bulk plate, in both the longitudinal and transverse directions, for the as-received condition as well as subjected to three different over-ageing heat-treatment schedules. A strong linear correlation between valid J1C and SP estimated biaxial fracture strain ,qf is presented for aluminium 6061 at room temperature. [source] A Silicon Carbonitride Ceramic with Anomalously High PiezoresistivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008Ligong Zhang The piezoresistive behavior of a silicon carbonitride ceramic derived from a polymer precursor is investigated under a uniaxial compressive loading condition. The electric conductivity has been measured as a function of the applied stress along both longitudinal and transverse directions. The gauge factor of the materials was then calculated from the data at different stress levels. The results show that the material exhibits an extremely high piezoresistive coefficient along both directions, ranging from 1000 to 4000, which are much higher than any existing ceramic material. The results also reveal that the gauge factor decreases significantly with increasing applied stress. A theoretical model based on the tunneling,percolation mechanism has been developed to explain the stress dependence of the gauge factor. The unique piezoresistive behavior is attributed to the unique self-assembled nanodomain structure of the material. [source] Real-time monitoring of fluorescence anisotropy and temperature during processing of biaxially stretched polypropylene film,POLYMER ENGINEERING & SCIENCE, Issue 4 2004Anthony J. Bur An optical sensor based on fiber optics has been developed to measure fluorescence anisotropy and temperature during processing of biaxially stretched polypropylene films. The sensor, containing optical fibers, polarizing elements and lenses, was mounted above the polypropylene film as it was processed in a tenter frame oven stretching machine. Fluorescence observations were made using the fluorescent dye, bis (di-tert butylphenyl) perylenedicarboximide (BTBP), which was doped into the resin at very low concentrations. To monitor biaxial stretching, fluorescence anisotropy measurements were carried out with light polarized in the machine and the transverse directions corresponding to the directions of biaxial stretching. Fluorescence based temperature measurements were obtained from the ratio of fluorescence intensities at 544 nm and 577 nm. A matrix of experiments involving three levels of stretch ratio in both the machine and transverse directions was undertaken. We observed significant differences between anisotropy in the machine and transverse directions that we attributed to the sequential stretching operation, i.e., the film was stretched in the machine direction first, followed by stretching in the transverse direction, and to film temperature and strain rate for each stretching operation. The result was uniformly higher anisotropies in the machine direction. Film temperature obtained from fluorescence corresponded to oven thermocouple measurements within 2°C. Polym. Eng. Sci. 44:805,813, 2004. © 2004 Society of Plastics Engineers. [source] Orthotropic elastic constants for polyimide filmPOLYMER ENGINEERING & SCIENCE, Issue 2 2001Seo Hyun Cho The orthotropic constants of polyimide film have been characterized using the theory of elasticity of an anisotropic material. Experimental techniques coupled with the mechanics of orthotropic materials are used to determine all 9 independent orthotropic elastic constants (3 tensile moduli, 3 shear moduli, and 3 Poisson's ratios) and 3 coefficients of thermal expansion. Vibrational holographic interferom-etry is used to determine the orthotropic axes of symmetry. For this polyimide film, the two principal axes coincided with the machine and transverse directions. It is also used to evaluate the 2 in-plane Poisson's ratios by measuring residual stresses in 2-D and 1-D square membranes. Using other instruments such as a high pressure gas dilatometry apparatus, a tensile tester, a pressure-volume-temperature apparatus, a thermornechanical analyzer, and a torsion pendulum, the 7 other orthotropic constants and the 3 coefficients of thermal expansion are determined. [source] | |||||||||||||||||||