Papers by Keyword: EFG

Abstract: The aim of this paper is to introduce a virtual crack closure technique based on EFG method for thread-shape crack. The cracked component is discretized and the displacement field is determined using a coupled FE/EFG method, by which EFG nodes are arranged in the vicinity of crack tip and FE elements in the remain part in order to improve computational efficiency. Two typical parameters, nodal force and crack opening displacement attached to crack tip are calculated by means of setting up an auxiliary FE zone around crack tip. Strain energy release rate (SERR), further stress intensity factor (SIF) are determined by the two parameters. The method to calculate SIF is named as virtual crack closure technique based on EFG method. It is showed by several numerical examples that using the method presented in this paper, SIF on the crack tip can be obtained accurately.

Abstract: The PAC-technique always claims to test the micro-surrounding of the probe atoms. Typically, the samples are macroscopic and more or less homogeneous and there is no debate about the usefulness of the method: substitutional sites, trapped vacancies or phase transitions are easily seen. Even the PAC-“fingerprint” of an amorphous material is known. In case of inhomogeneous samples, perhaps made out of different constituents, the question arises whether the PAC can contribute to the understanding of such materials or not. The article will show the different ways to introduce the probe atoms into the samples and discuss then the influence of these histories on the final site of the probe in the sample. In general, diffusion tends to place the probes into grain boundaries, whereas implantation reaches the bulk. This becomes important for nano-materials with their high fraction of internal surfaces. As a second, important difference for possible experiments the spatial distribution of the probes has to be considered. Implantation leads to a Gaussian shaped depth distribution of the probes. This corresponds – in a certain region – to a 3-dimensional distribution of probes in the sample, used e.g. when doping a semiconductor. In the production of special sensors (which apply e.g. the giant magnetoresistance (GMR) effect) one needs a different package, thin films (1-2 mono-layers). To apply PAC here, the probes have to be introduced during the fabrication of such a sensor. In these cases the probes have to be placed within a plane of nano-scale thickness.

Abstract: During piercing rolling simulation, extreme mesh deformation cannot be solved by the finite element method (FEM). Re-meshing is necessary to prevent the effect of severe mesh distortion. However, the element-free method can solve this problem because the continuous body is discretized with a set of nodes, not meshes. In this paper, three-dimension rigid-plastic element-free Galerkin Method (EFG) is introduced to analyze the piercing rolling process. The approximation functions are calculated considering a moving least squares (MLS) approach. The Newton-Raphson method is used for the solution of the nonlinear system of equations. The equivalent stress, the equivalent plastic strain and the equivalent plastic strain rate obtained by EFG and rigid-plastic FEM are analyzed and compared. The simulation results of the EFG method are in agreement with those obtained by using the rigid-plastic FEM and the effectiveness of the model is verified.