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  • 2.5D Green's Functions for Elastodynamic Problems in Layered Acoustic and Elastic Formations
  • Abstract This paper presents analytical solutions, together with explicit expressions, for the steady state response of homogeneous three-dimensional layered acoustic and elastic formations subjected to a spatially sinusoidal harmonic line load. These formulas are theoretically interesting in themselves and they are also useful as benchmark solutions for numerical applications. In particular, they are very important in formulating three-dimensional elastodynamic problems in layered fluid and solid formations using integral transform methods and/or boundary elements, avoiding the discretization of the solid-fluid interfaces. The proposed Green's functions will allow the solution to be obtained for high frequencies, for which the conventional boundary elements' solution…
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  • A Meshless Local Petrov-Galerkin (MLPG) Formulation for Static and Free Vibration Analyses of Thin Plates
  • Abstract A meshless method for the analysis of Kirchhoff plates based on the Meshless Local Petrov-Galerkin (MLPG) concept is presented. A MLPG formulation is developed for static and free vibration analyses of thin plates. Local weak form is derived using the weighted residual method in local supported domains from the 4th order partial differential equation of Kirchhoff plates. The integration of the local weak form is performed in a regular-shaped local domain. The Moving Least Squares (MLS) approximation is used to constructed shape functions. The satisfaction of the high continuity requirements is easily met by MLS interpolant, which is based on…
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  • On the Equivalence Between Least-Squares and Kernel Approximations in Meshless Methods
  • Abstract Meshless methods using least-squares approximations and kernel approximations are based on non-shifted and shifted polynomial basis, respectively. We show that, mathematically, the shifted and non-shifted polynomial basis give rise to identical interpolation functions when the nodal volumes are set to unity in kernel approximations. This result indicates that mathematically the least-squares and kernel approximations are equivalent. However, for large point distributions or for higher-order polynomial basis the numerical errors with a non-shifted approach grow quickly compared to a shifted approach, resulting in violation of consistency conditions. Hence, a shifted polynomial basis is better suited from a numerical implementation point of…
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  • Steady Heat Conduction Analysis in Orthotropic Bodies by Triple-reciprocity BEM
  • Abstract The boundary element method (BEM) is useful in solving the steady heat conduction problem of orthotropic bodies without heat generation. However, for cases with arbitrary heat generation, a number of internal cells are necessary. In this paper, it is shown that the problem of steady heat conduction in orthotropic bodies with heat generation can be solved without internal cells by the triple-reciprocity BEM. In this method, the distribution of heat generation is interpolated using integral equations. In order to solve the problem, the values of heat generation at internal points and on the boundary are used. Furthermore, a new interpolation…
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  • A Pure Contour Formulation for the Meshless Local Boundary Integral Equation Method in Thermoelasticity
  • Abstract A new meshless method for solving stationary thermoelastic boundary value problems is proposed in the present paper. The moving least square (MLS) method is used for the approximation of physical quantities in the local boundary integral equations (LBIE). In stationary thermoelasticity, the temperature and displacement fields are uncoupled. In the first step, the temperature field, described by the Laplace equation, is analysed by the LBIE. Then, the mechanical quantities are obtained from the solution of the LBIEs, which are reduced to elastostatic ones with redefined body forces due to thermal loading. The domain integrals with temperature gradients are transformed to…
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  • SGBEM-FEM Alternating Method for Analyzing 3D Non-planar Cracks and Their Growth in Structural Components1
  • Abstract An efficient and highly accurate, Symmetric Galerkin Boundary Element Method - Finite Element Method - based alternating method, for the analysis of three-dimensional non-planar cracks, and their growth, in structural components of complicated geometries, is proposed. The crack is modeled by the symmetric Galerkin boundary element method, as a distribution of displacement discontinuities, as if in an infinite medium. The finite element method is used to perform the stress analysis for the uncracked body only. The solution for the structural component, containing the crack, is obtained in an iteration procedure, which alternates between FEM solution for the uncracked body, and…
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  • Lateral Plastic Collapse of Cylinders: Experiments and Modeling
  • Abstract Large plastic collapse of an identical pair of cylinders of various geometries having the same length and volume is studied under lateral compressive load. Superplastic material is employed as a representative material to simulate the classical engineering material behavior under high strain rate. The effects of the strain rate and the geometry of cylinders on the plastic collapse are taken into account. The experimental study is conducted using a structure in which one cylinder is superplastic and the other is steel (referred to as deformable and non-deformable situation "DND''). The actual structure (DND) and that one investigated experimentally by Abdul-Latif…
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  • Numerical Solution of Plane Elasticity Problems with the Cell Method
  • Abstract The aim of this paper is to present a methodology for solving the plane elasticity problem using the Cell Method. It is shown that with the use of a parabolic interpolation in a vectorial problem, a convergence rate of 3.5 is obtained. Such a convergence rate compares with, or is even better than, the one obtained with FEM with the same interpolation – depending on the integration technique used by the FEM application. The accuracy of the solution is also comparable or better.
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  • Modeling of Nonlinear Rate Sensitivity by Using an Overstress Model
  • Abstract Negative, zero or positive rate sensitivity of the flow stress can be observed in metals and alloys over a certain range of strain, strain rate and temperature. It is believed that negative rate sensitivity is an essential feature of dynamic strain aging, of which the Portevin-Le Chatelier effect is one other manifestation. The viscoplasticity theory based on overstress (VBO), one of the unified state variable theories, is generalized to model zero (rate independence) and negative as well as positive rate sensitivity in a consistent way. The present model does not have the stress rate term in the evolution law for…
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