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Anisotropic Materials (anisotropic + material)
Selected AbstractsStress Concentration Factors and Weight Functions in Thin Notched Structures of Equibiaxial Anisotropic Materials,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Michael Heinzelmann In notched structures, the influence of the notch on the structural strength of the component can be described by a stress concentration factor or,in the presence of cracks,a weight function. Numerous stress concentration factor and weight function solutions are available to the engineer, but regrettably almost exclusively for isotropic materials. In the present study, stress concentration factors and weight functions are calculated for equibiaxial anisotropic materials. The geometry under investigation is a flat plate in tension containing a central hole. The calculated results show that the elastic anisotropic material behavior can significantly influence the magnitude of both stress concentration factors and weight functions. [source] 157 nm fluorine laser ablation of wooden surfaces as an improved preparation technique for microscopyLASER PHYSICS LETTERS, Issue 1 2005M. Kopp Abstract By means of 157 nm VUV short-wavelength laserirradiation the wood layer of damaged cells near the surface as well as deeper wood regions can be removed. As this is a nonthermal laser ablation-process, oxidation of the wood surface exposed to 157 nm under N2 -atmosphere is avoided even with high power densities. By applying a mechanical pre-treatment process the wood structure is compressed and can then be removed with almost no damage. Four types of wood - spruce, pine, beech and oak - were ablated in all three main cutting directions prescribed for an anisotropic material such as wood. Several microscopic techniques were used. To measure the ablation depth LSM was applied. The surface roughness as well as the quality of the laser ablation was determined by using LV-SEM. CAM was used to measure the contact angle and thereby calculate the surface energy. Ablation can be carried out regardless of the cutting direction used to obtain clean and open surfaces free of artefacts. (© 2005 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [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] Stress Concentration Factors and Weight Functions in Thin Notched Structures of Equibiaxial Anisotropic Materials,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Michael Heinzelmann In notched structures, the influence of the notch on the structural strength of the component can be described by a stress concentration factor or,in the presence of cracks,a weight function. Numerous stress concentration factor and weight function solutions are available to the engineer, but regrettably almost exclusively for isotropic materials. In the present study, stress concentration factors and weight functions are calculated for equibiaxial anisotropic materials. The geometry under investigation is a flat plate in tension containing a central hole. The calculated results show that the elastic anisotropic material behavior can significantly influence the magnitude of both stress concentration factors and weight functions. [source] Inverse determination of the elastoplastic and damage parameters on small punch testsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2009I. PEÑUELAS ABSTRACT The small punch test (SPT) is very useful in those situations where it is necessary to use small volumes of material. The aim of this paper is to create and validate a methodology for the determination of the mechanical and damage properties of steels from the load-displacement curve obtained by means of SPTs. This methodology is based on the inverse method, the design of experiments, the polynomial curve adjustment and the evolutionary multi-objective optimization, and also allows simulating the SPTs. In order to validate the proposed methodology, the numerical results have been compared with experimental results obtained by means of normalized tests. Two dimensional axisymmetric and three-dimensional simulations have been performed in order to allow the analysis of isotropic and anisotropic materials, respectively. [source] Lagrangian finite element treatment of transient vibration/acoustics of biosolids immersed in fluidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008P. Krysl Abstract Superposition principle is used to separate the incident acoustic wave from the scattered and radiated waves in a displacement-based finite element model. An absorbing boundary condition is applied to the perturbation part of the displacement. Linear constitutive equation allows for inhomogeneous, anisotropic materials, both fluids and solids. Displacement-based finite elements are used for all materials in the computational volume. Robust performance for materials with limited compressibility is achieved using assumed-strain nodally integrated simplex elements or incompatible-mode brick elements. A centered-difference time-stepping algorithm is formulated to handle general damping accurately and efficiently. Verification problems (response of empty steel cylinder immersed in water to a step plane wave, and scattering of harmonic plane waves from an elastic sphere) are discussed for assumed-strain simplex and for voxel-based brick finite element models. A voxel-based modeling scheme for complex biological geometries is described, and two illustrative results are presented from the bioacoustics application domain: reception of sound by the human ear and simulation of biosonar in beaked whales. Copyright © 2007 John Wiley & Sons, Ltd. [source] A continued-fraction-based high-order transmitting boundary for wave propagation in unbounded domains of arbitrary geometryINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2008Mohammad Hossein Bazyar Abstract A high-order local transmitting boundary is developed to model the propagation of elastic waves in unbounded domains. This transmitting boundary is applicable to scalar and vector waves, to unbounded domains of arbitrary geometry and to anisotropic materials. The formulation is based on a continued-fraction solution of the dynamic-stiffness matrix of an unbounded domain. The coefficient matrices of the continued fraction are determined recursively from the scaled boundary finite element equation in dynamic stiffness. The solution converges rapidly over the whole frequency range as the order of the continued fraction increases. Using the continued-fraction solution and introducing auxiliary variables, a high-order local transmitting boundary is formulated as an equation of motion with symmetric and frequency-independent coefficient matrices. It can be coupled seamlessly with finite elements. Standard procedures in structural dynamics are directly applicable for evaluating the response in the frequency and time domains. Analytical and numerical examples demonstrate the high rate of convergence and efficiency of this high-order local transmitting boundary. Copyright © 2007 John Wiley & Sons, Ltd. [source] Eigen-frequencies in thin elastic 3-D domains and Reissner,Mindlin plate modelsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2002Monique Dauge Abstract The eigen-frequencies of elastic three-dimensional thin plates are addressed and compared to the eigen-frequencies of two-dimensional Reissner,Mindlin plate models obtained by dimension reduction. The qualitative mathematical analysis is supported by quantitative numerical data obtained by the p-version finite element method. The mathematical analysis establishes an asymptotic expansion for the eigen-frequencies in power series of the thickness parameter. Such results are new for orthotropic materials and for the Reissner,Mindlin model. The 3-D and R,M asymptotics have a common first term but differ in their second terms. Numerical experiments for clamped plates show that for isotropic materials and relatively thin plates the Reissner,Mindlin eigen-frequencies provide a good approximation to the three-dimensional eigen-frequencies. However, for some anisotropic materials this is no longer the case, and relative errors of the order of 30 per cent are obtained even for relatively thin plates. Moreover, we showed that no shear correction factor is known to be optimal in the sense that it provides the best approximation of the R,M eigen-frequencies to their 3-D counterparts uniformly (for all relevant thicknesses range). Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||