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Static Problems (static + problem)
Selected AbstractsVolume of a liquid drop detaching from a sphereHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010Kenji Katoh Abstract A theoretical and experimental study is conducted to investigate the detached volume from a pendant drop on the surface of a sphere. Observation of drop detachment by high-speed video camera reveals that the movement of the upper part of the neck of the drop is quite slow compared to that of the detaching lower part. The surface profile of the upper part was calculated approximately as a static problem using the axisymmetric Laplace equation. Using the drop profile, the system energy, including the work done by the solid,liquid wetting behavior, was calculated. Based on the condition of minimum energy, the volume of the detached part V was calculated. The volume V increases with the sphere diameter and approaches the value for the pendant drop attached to a plate. In addition, V is strongly dependent on the wettability between the sphere and the liquid and decreases with the receding contact angle. The detached volume of the water drop was measured for spheres of porous brick of various diameters. The experimental and theoretical results were found to be in good agreement. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20305 [source] Variational h -adaption in finite deformation elasticity and plasticityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2007J. Mosler Abstract We ropose a variational h -adaption strategy in which the evolution of the mesh is driven directly by the governing minimum principle. This minimum principle is the principle of minimum potential energy in the case of elastostatics; and a minimum principle for the incremental static problem of elasto-viscoplasticity. In particular, the mesh is refined locally when the resulting energy or incremental pseudo-energy released exceeds a certain threshold value. In order to avoid global recomputes, we estimate the local energy released by mesh refinement by means of a lower bound obtained by relaxing a local patch of elements. This bound can be computed locally, which reduces the complexity of the refinement algorithm to O(N). We also demonstrate how variational h -refinement can be combined with variational r -refinement to obtain a variational hr -refinement algorithm. Because of the strict variational nature of the h -refinement algorithm, the resulting meshes are anisotropic and outperform other refinement strategies based on aspect ratio or other purely geometrical measures of mesh quality. The versatility and rate of convergence of the resulting approach are illustrated by means of selected numerical examples. Copyright © 2007 John Wiley & Sons, Ltd. [source] An advanced boundary element method for solving 2D and 3D static problems in Mindlin's strain-gradient theory of elasticityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2010G. F. Karlis Abstract An advanced boundary element method (BEM) for solving two- (2D) and three-dimensional (3D) problems in materials with microstructural effects is presented. The analysis is performed in the context of Mindlin's Form-II gradient elastic theory. The fundamental solution of the equilibrium partial differential equation is explicitly derived. The integral representation of the problem, consisting of two boundary integral equations, one for displacements and the other for its normal derivative, is developed. The global boundary of the analyzed domain is discretized into quadratic line and quadrilateral elements for 2D and 3D problems, respectively. Representative 2D and 3D numerical examples are presented to illustrate the method, demonstrate its accuracy and efficiency and assess the gradient effect on the response. The importance of satisfying the correct boundary conditions in gradient elastic problems is illustrated with the solution of simple 2D problems. Copyright © 2010 John Wiley & Sons, Ltd. [source] Four-node semi-EAS element in six-field nonlinear theory of shellsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2006J. Chró, cielewski Abstract We propose a new four-node C0 finite element for shell structures undergoing unlimited translations and rotations. The considerations concern the general six-field theory of shells with asymmetric strain measures in geometrically nonlinear static problems. The shell kinematics is of the two-dimensional Cosserat continuum type and is described by two independent fields: the vector field for translations and the proper orthogonal tensor field for rotations. All three rotational parameters are treated here as independent. Hence, as a consequence of the shell theory, the proposed element has naturally six engineering degrees of freedom at each node, with the so-called drilling rotation. This property makes the element suitable for analysis of shell structures containing folds, branches or intersections. To avoid locking phenomena we use the enhanced assumed strain (EAS) concept. We derive and linearize the modified Hu,Washizu principle for six-field theory of shells. What makes the present approach original is the combination of EAS method with asymmetric membrane strain measures. Based on literature, we propose new enhancing field and specify the transformation matrix that accounts for the lack of symmetry. To gain knowledge about the suitability of this field for asymmetric strain measures and to assess the performance of the element, we solve typical benchmark examples with smooth geometry and examples involving orthogonal intersections of shell branches. Copyright © 2006 John Wiley & Sons, Ltd. [source] A refined semi-analytic design sensitivity based on mode decomposition and Neumann seriesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005Maenghyo Cho Abstract Among various sensitivity evaluation techniques, semi-analytical method (SAM) is quite popular since this method is more advantageous than analytical method (AM) and global finite difference method (GFD). However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the pseudo load vector calculated by differentiation using the finite difference scheme. In the present study, an iterative refined semi-analytical method (IRSAM) combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes and the error of SAM caused by numerical difference scheme is alleviated by using a Von Neumann series approximation considering the higher order terms for the sensitivity derivatives. In eigenvalue problems, the tendency of eigenvalue sensitivity is similar to that of displacement sensitivity in static problems. Eigenvector is decomposed into rigid body mode and pure deformation mode. The present iterative SAM guarantees that the eigenvalue and eigenvector sensitivities converge to the reliable values for the wide range of perturbed size of the design variables. Accuracy and reliability of the shape design sensitivities in static problems and eigenvalue problems by the proposed method are assessed through the various numerical examples. Copyright © 2004 John Wiley & Sons, Ltd. [source] Development of a packaging material using antistatic ionomer part 2: charge distributions of potassium ionomerPACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2007Nobuyuki Maki Abstract Generally, plastics and plastic films are low in moisture absorption and high in electric insulation. They are inherently easy to be charged with static and can cause a variety of static troubles. We developed a functional packaging material to solve these static problems, by using potassium ionomer. We reported good antistatic performance (e.g. short static decay time, and excellent ash test) of potassium ionomer films in a previous paper. However, a mechanism underlying the antistatic property of potassium ionomer has not yet been fully elucidated. In this study, we measured the space charge distributions of potassium ionomer using the pulsed electro-acoustic method. As a result of the space charge measurements, we found characteristic charge distribution of potassium ionomer film. On the basis of the existence of this characteristic charge distribution, we speculate that the space electric charge distribution of a potassium ionomer film under a direct current electric field shows apparent electric charge movement. Copyright © 2006 John Wiley & Sons, Ltd. [source] Development of a packaging material using non-bleed-type antistatic ionomerPACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2004Nobuyuki Maki Abstract Generally, plastics and plastic films are low in moisture absorption and high in electric insulation. They are inherently vulnerable to static charge build-up, which can result in a variety of problems. We have developed a functional packaging material to solve these static problems, by using a potassium salt of ethylene ionomer, which is a non-bleed-type antistatic agent. Good antistatic performance was shown by evaluating a variety of electric characteristics (e.g. the static decay time, ash test and saturated electrostatic charge and half-life) and surface resistivity. In addition, antistatic performance was achieved on the mLLDPE (non-treated) side in a multilayer structure. This means that the use of potassium ionomer on any layers in a multilayer structure provides antistatic performance, leading to the expectation of developing a wide variety and diversity of packaging materials. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||