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Circumferential Direction (circumferential + direction)
Selected AbstractsSemi-analytical far field model for three-dimensional finite-element analysisINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 11 2004James P. Doherty Abstract A challenging computational problem arises when a discrete structure (e.g. foundation) interacts with an unbounded medium (e.g. deep soil deposit), particularly if general loading conditions and non-linear material behaviour is assumed. In this paper, a novel method for dealing with such a problem is formulated by combining conventional three-dimensional finite-elements with the recently developed scaled boundary finite-element method. The scaled boundary finite-element method is a semi-analytical technique based on finite-elements that obtains a symmetric stiffness matrix with respect to degrees of freedom on a discretized boundary. The method is particularly well suited to modelling unbounded domains as analytical solutions are found in a radial co-ordinate direction, but, unlike the boundary-element method, no complex fundamental solution is required. A technique for coupling the stiffness matrix of bounded three-dimensional finite-element domain with the stiffness matrix of the unbounded scaled boundary finite-element domain, which uses a Fourier series to model the variation of displacement in the circumferential direction of the cylindrical co-ordinate system, is described. The accuracy and computational efficiency of the new formulation is demonstrated through the linear elastic analysis of rigid circular and square footings. Copyright © 2004 John Wiley & Sons, Ltd. [source] Scaled boundary finite-element analysis of a non-homogeneous axisymmetric domain subjected to general loadingINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2003James P. Doherty Abstract The scaled boundary finite-element method is derived for elastostatic problems involving an axisymmetric domain subjected to a general load, using a Fourier series to model the variation of displacement in the circumferential direction of the cylindrical co-ordinate system. The method is particularly well suited to modelling unbounded problems, and the formulation allows a power-law variation of Young's modulus with depth. The efficiency and accuracy of the method is demonstrated through a study showing the convergence of the computed solutions to analytical solutions for the vertical, horizontal, moment and torsion loading of a rigid circular footing on the surface of a homogeneous elastic half-space. Computed solutions for the vertical and moment loading of a smooth rigid circular footing on a non-homogeneous half-space are compared to analytical ones, demonstrating the method's ability to accurately model a variation of Young's modulus with depth. Copyright © 2003 John Wiley & Sons, Ltd. [source] Swelling effect on the dynamic behaviour of composite cylindrical shells conveying fluidINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2006M. H. Toorani Abstract This paper presents a semi-analytical investigation of a fluid,structure system. Both isotropic and composite cylindrical shells filled with or subjected to a flowing fluid have been considered in this study. The structure may be uniform or non-uniform in the circumferential direction. The hybrid finite element approach, shearable shell theory and velocity potential flow theory have been combined to establish the dynamic equations of the coupled system. The set of matrices describing their relative contributions to equilibrium is determined by exact analytical integration of the equilibrium equations. The linear potential flow theory is applied to describe the fluid effects that lead to the inertial, centrifugal and Coriolis forces. The axisymmetric, beam-like and shell modes of vibrations in both cases of uniform and non-uniform cylindrical shells are investigated. Fluid elastic stability of a structure subjected to a flowing fluid is also studied. This theory yields the high and the low eigenvalues and eigenmodes with comparably high accuracy. Reasonable agreement is found with other theories and experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Biomechanics of Diabetic BladdersLUTS, Issue 2009Chung Cheng WANG Objectives: Biomechanics is the mechanics applied to biology and we hereby review bladder biomechanics in diabetic bladder dysfunction. Methods: The important mechanical properties of bladder tissue include the stress-strain relationship, viscoelasticity and active contraction. Using biaxial mechanical testing methods, the diabetic bladders exhibited non-linear stress-strain mechanical relationships with increasing stiffness at higher stretches in both circumferential and longitudinal directions. Results: The diabetic bladders showed mechanical anisotropy with a greater compliance in the circumferential direction than in the longitudinal direction. The time-course study suggested that diuresis mainly contributed to the "early" changes of the mechanical properties with "late" changes induced by other diabetic effects. Conclusion: The biomechanical study of the urinary bladder has offered a novel understanding of the pathophysiology of diabetic cystopathy and we believe the collaboration of urology and engineering will contribute greatly to the treatment of diabetic bladder dysfunction in the future. [source] Thermal properties of biaxially deformed in situ compositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2004Youngwook P. Seo The thermal properties of biaxially blown poly(etherimide) (PEI) films containing a thermotropic liquid crystalline polymer (TLCP) were studied using differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction and dynamic mechanical thermal analysis. The effects of the compatibilizer and thermal annealing on the thermal properties of biaxially oriented TLCP films were investigated. Though the compatibilizer (poly(ester imide)) improved deformation of the TLCP phase (poly ester amide) and adhesion between the matrix and the TLCP phase, which improved mechanical properties, it did not significantly affect the thermal properties of the in situ composite films. The film degradation behavior corroborated the role of the compatibilizer. Since a relatively small amount of TLCP (10 wt%) was added to the matrix and the matrix PEI was amorphous, the effect of annealing on the TLCP structure was not obvious. By the same token, while the effect of the deformation in the circumferential direction (a change in the blow-up ratio) was manifest in mechanical property improvements, its effect on the thermal properties was not obvious. All films showed similar thermal expansion behaviors, regardless of the thermal history and of the compatibilizer addition. Thus, there is an optimum amount of the compatibilizer required to obtain optimal mechanical properties for in situ composite films without causing a deterioration of their thermal properties. Polym. Eng. Sci. 44:1419,1428, 2004. © 2004 Society of Plastics Engineers. [source] Effect of vibration extrusion on the structure and properties of high-density polyethylene pipesPOLYMER INTERNATIONAL, Issue 2 2009Chen Kaiyuan Abstract BACKGROUND: The axial strength of a plastic pipe is much higher than its circumferential strength due to the macromolecular orientation during extrusion. In this work, a custom-made electromagnetic dynamic plasticating extruder was adopted to extrude high-density polyethylene (HDPE) pipes. A vibration force field was introduced into the whole plasticating and extrusion process by axial vibration of the screw. The aim of superimposing a vibration force field was to change the crystalline structure of HDPE and improve the molecular orientation in the circumferential direction to obtain high-circumferential-strength pipes. RESULTS: Through vibration extrusion, the circumferential strength of HDPE pipes increased significantly, and biaxial self-reinforcement pipes could be obtained. The maximum increase of bursting pressure and tensile yield strength was 34.2 and 5.3%, respectively. According to differential scanning calorimetry and wide-angle X-ray diffraction measurements, the HDPE pipes prepared by vibration extrusion had higher crystallinity, higher melting temperature, larger crystal sizes and more perfect crystals. CONCLUSION: Vibration extrusion can effectively enhance the mechanical properties of HDPE pipes, especially the circumferential strength. The improvement of mechanical properties of HDPE pipes obtained by vibration extrusion can be attributed to the higher degree of crystallinity and the improvement of the molecular orientation and of the crystalline morphology. Copyright © 2008 Society of Chemical Industry [source] Numerical Investigation of Turbulent Flow around a Rotating Stepped Cylinder for Corrosion StudyTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2003Kyung-Soo Yang Abstract Direct numerical simulation has been carried out for turbulent flow set up by a rotating cylinder with two backward-facing steps axisymmetrically mounted in the circumferential direction. This flow geometry creates a qualitatively similar flow pattern as observed near a sudden pipe expansion or a plane backward-facing step, characterized by flow separation and reattachment. A region of intense turbulence intensity and high wall-shear-stress fluctuations is formed in the recirculating region downstream of the step, where high mass-transfer capacity was also experimentally observed. Since corrosion is frequently mass-transfer controlled, our findings put forward this apparatus as a useful tool for future corrosion research. On a effectué une simulation numérique directe de l'écoulement turbulent créé par un cylindre rotatif ayant deux contractions axisymétriques dans la direction circonférentielle. Cette géométrie crée un profil d'écoulement qualitativement similaire à celui qu'on observe près d'une expansion de conduite soudaine ou d'une contraction planaire, caractérisés par la séparation et le ré-attachement de l'écoulement. Une région d'intense turbulence et de fortes fluctuations de contraintes de cisaillement pariétal se forment dans la région en recirculation en aval de la contraction, où une grande capacité de transfert de matière a également été observée expérimentalement. Étant donné que la corrosion dépend souvent du transfert de matière, nos résultats font la promotion de cet appareillage en tant qu'outil utile pour la recherche future sur la corrosion. [source] Prediction of Leakage Flow in a Shrouded Centrifugal Blood PumpARTIFICIAL ORGANS, Issue 9 2010Ji-Bin Teo Abstract This article proposes a phenomenological model to predict the leakage flow in the clearance gap of shrouded centrifugal blood pumps. A good washout in the gap clearance between the rotating impeller surfaces and volute casing is essential to avoid thrombosis. However, excessive leakage flow will result in higher fluid shear stress that may lead to hemolysis. Computational fluid dynamics (CFD) analysis was performed to investigate the leakage flow in a miniaturized shrouded centrifugal blood pump operating at a speed of 2000 rpm. Based on an analytical model derived earlier, a phenomenological model is proposed to predict the leakage flow. The leakage flow rate is found to be proportional to h,, where h is the gap size and the exponent , ranges from 2.955 to 3.15 for corresponding gap sizes of 0.2,0.5 mm. In addition, it is observed that , is a linear function of the gap size h. The exponent , compensates for the variation of pressure difference along the circumferential direction as well as inertia effects that are dominant for larger gap clearances. The proposed model displays good agreement with computational results. The CFD analysis also showed that for larger gap sizes, the total leakage flow rate is of the same order of magnitude as the operating flow rate, thus suggesting low volumetric efficiency. [source] | ||||||||||||||||