The boundary element method for elasticity problems with concentrated loads based on displacement singular elements

The boundary element method (BEM) has been implemented in elasticity problems very successfully because of its high accuracy. However, there are very few investigations about BEM with concentrated loads. The displacement at the concentrated load point is infinite and traditional elements will lead inaccurate results near the concentrated load point. This paper proposes two types of displacement singular elements to approximate the displacement near concentrated load point, and high accuracy can be obtained without refinement. The second type of displacement singular element is a general element type, which can work well for both problems with or without boundary concentrated loads. Numerical examples have been studied and compared with results obtained by traditional BEM and finite element method (FEM) to show the necessary of the proposed methods

Research on high frequency vibro-acoustic response of typical structure based on finite element method

Finite element method (FEM) is used to calculate coupling loss factor (CLF), which is an important parameter in statistical energy analysis(SEA). The results are in good agreement with the one of wave method, and the relative error of the two methods is calculated. The influence of side length of the plate, internal loss factor (ILF), concentrated mass and boundary conditions on the calculation accuracy of CLF is studied by FEM. It is found that, with the increase of the side length the results of CLF become more reliable. In the low frequency band, the influence of concentrated mass and boundary conditions on CLF is obvious, while the influence can be neglected in the high frequency band. In order to ensure the accuracy of CLF, ILF should be much larger than CLF, but ILF can’t be increased indefinitely

Limit-point buckling analyses using solid, shell and solid–shell elements

In this paper, the recently-developed solid-shell element SHB8PS is used for the analysis of a representative set of popular limit-point buckling benchmark problems. For this purpose, the element has been implemented in Abaqus/Standard finite element software and the modified Riks method was employed as an efficient path-following strategy. For the. benchmark problems tested, the new element shows better performance compared to solid elements and often performs as well as state-of-the-art shell elements. In contrast to shell elements, it allows for the accurate prescription of boundary conditions as applied to the actual edges of the structure.Agence Nationale de la Recherche, France (ANR-005-RNMP-007

Scale effects in orthotropic composite assemblies as micropolar continua: A comparison between weak-and strong-form finite element solutions

The aim of the present work was to investigate the mechanical behavior of orthotropic composites, such as masonry assemblies, subjected to localized loads described as micropolar materials. Micropolar models are known to be effective in modeling the actual behavior of microstructured solids in the presence of localized loads or geometrical discontinuities. This is due to the introduction of an additional degree of freedom (the micro-rotation) in the kinematic model, if compared to the classical continuum and the related strain and stress measures. In particular, it was shown in the literature that brick/block masonry can be satisfactorily modeled as a micropolar continuum, and here it is assumed as a reference orthotropic composite material. The in-plane elastic response of panels made of orthotropic arrangements of bricks of different sizes is analyzed herein. Numerical simulations are provided by comparing weak and strong finite element formulations. The scale effect is investigated, as well as the significant role played by the relative rotation, which is a peculiar strain measure of micropolar continua related to the non-symmetry of strain and work-conjugated stress. In particular, the anisotropic effects accounting for the micropolar moduli, related to the variation of microstructure internal sizes, are highlighted

A non-hybrid method for the PDF equations of turbulent flows on unstructured grids

In probability density function (PDF) methods of turbulent flows, the joint PDF of several flow variables is computed by numerically integrating a system of stochastic differential equations for Lagrangian particles. A set of parallel algorithms is proposed to provide an efficient solution of the PDF transport equation, modeling the joint PDF of turbulent velocity, frequency and concentration of a passive scalar in geometrically complex configurations. An unstructured Eulerian grid is employed to extract Eulerian statistics, to solve for quantities represented at fixed locations of the domain (e.g. the mean pressure) and to track particles. All three aspects regarding the grid make use of the finite element method (FEM) employing the simplest linear FEM shape functions. To model the small-scale mixing of the transported scalar, the interaction by exchange with the conditional mean model is adopted. An adaptive algorithm that computes the velocity-conditioned scalar mean is proposed that homogenizes the statistical error over the sample space with no assumption on the shape of the underlying velocity PDF. Compared to other hybrid particle-in-cell approaches for the PDF equations, the current methodology is consistent without the need for consistency conditions. The algorithm is tested by computing the dispersion of passive scalars released from concentrated sources in two different turbulent flows: the fully developed turbulent channel flow and a street canyon (or cavity) flow. Algorithmic details on estimating conditional and unconditional statistics, particle tracking and particle-number control are presented in detail. Relevant aspects of performance and parallelism on cache-based shared memory machines are discussed.Comment: Accepted in Journal of Computational Physics, Feb. 20, 200