A parallel Element-Free Galerkin formulation for acoustic analyses: rationale and strategy

info:eu-repo/semantics/publishe

Adaptation de maillage en optimisation de structure

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3D Structural optimization with error control

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3D Acoustic Analysis Using an Iterative Multilevel Meshless Method

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Element-free Galerkin method formulation for acoustic analyses: Rationale and strategy

This paper deals with the numerical simulation of the acoustic wave propagation. It is well known today that the standard finite element method (FEM) is unreliable to compute approximate solutions of the Helmholtz equation for high wavenumbers due to the pollution effect, consisting mainly of the dispersion, i.e. the numerical wavelength is longer than the exact one. Unless highly refined meshes are used, FEM solutions lead to unacceptable solutions in terms of precision, while the use of very refined meshed increases the cost in terms of computational times. The paper presents an application of the Element-Free Galerkin Method (EFGM) and focuses on the dispersion analysis in two dimensions. It shows that it is possible to choose the parameters of the method in order to minimize the dispersion and to get extremely good results in comparison with the stabilized FEM. However, to lead to those very accurate results for 1-D and 2-D problems, the EFGM needs an important computational time, mainly due to the computation and the assembly of the stiffness and mass matrices. Thus, in order to reduce this computational time, it is suggested in this paper, as a first step, to take advantage from the developments of computer hardware, currently moving towards multi-processor machines, by computing and assemblying the matrices simultaneously on several processors. This is called a parallel assembly algorithm. The paper presents the numerical assessment of the CPU performance of the parallel implementation vs the sequential one.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effect of interaction of embedded crack and free surface on remaining fatigue life

Embedded crack located near free surface of a component interacts with the free surface. When the distance between the free surface and the embedded crack is short, stress at the crack tip ligament is higher than that at the other area of the cracked section. It can be easily expected that fatigue crack growth is fast, when the embedded crack locates near the free surface. To avoid catastrophic failures caused by fast fatigue crack growth at the crack tip ligament, fitness-for-service (FFS) codes provide crack-to-surface proximity rules. The proximity rules are used to determine whether the cracks should be treated as embedded cracks as-is, or transformed to surface cracks. Although the concepts of the proximity rules are the same, the specific criteria and the rules to transform embedded cracks into surface cracks differ amongst FFS codes. This paper focuses on the interaction between an embedded crack and a free surface of a component as well as on its effects on the remaining fatigue lives of embedded cracks using the proximity rules provided by the FFS codes. It is shown that the remaining fatigue lives for the embedded cracks strongly depend on the crack aspect ratio and location from the component free surface. In addition, it can be said that the proximity criteria defined by the API and RSE-M codes give overly conservative remaining lives. On the contrary, the WES and AME codes always give long remaining lives and non-conservative estimations. When the crack aspect ratio is small, ASME code gives non-conservative estimation

Parallélisation de l'assemblage pour la méthode d'approximation nodale en acoustique

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Element-Free Galerkin method applied to acoustics: multi-processors assembly algorithm

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Iterative multilevel meshless method for acoustics

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