Mamtimin Gheni

Effect of Mesh Size of Finite Element Analysis in Modal Analysis for Periodic Symmetric Struts Support

Meshing for finite element analysis accuracy plays a very important part in numerical simulation of Periodic Symmetric Struts Support (PSSS). Different accuracy can be obtained by different element sizes or types. Three element types and eight element sizes are used for comparing the accuracy of modal analysis in this paper. Comparing with the mutual relations of different accuracy, the scientific basis is provided for selecting the correct mesh size and improves the efficiency of numerical calculation in modal analysis.

Shape Optimization of Metal Welded Bellows Seal Based on the Turing Reaction-Diffusion Model Coupled with FEM

In this paper, the Turing reaction-diffusion model coupled with Finite Element Method (FEM) is implemented first by considering the biomechanical model iBone (Imitation Bone). Then the shape optimization of Metal Welded Bellows Seal (MWBS) is conducted based on the biomechanical bone forming process by considering the osteoclasts and osteoblasts process. The MWBS mass and shape is changed by changing the initial boundary condition, then some reasonable results are obtained by keeping the required forming value, and the new S type wave of metal welded bellow of mechanical seal are obtained. Finally, the strength evaluations are conducted for new optimized S type model and original V and S type models by using the FEM software.

Shape Optimization and Strength Evaluation of Metal Welded Bellows Wave of Mechanical Seal

In this paper, the iBone (Imitation Bone) model which is coupled with Turing reaction-diffusion system and FEM, is used. The numerical simulation of bone forming process by considering the osteoclasts and osteoblasts process are conducted. The bone mass is increased with increase of the initial load value, then fibula and femur bones are obtained respectively by keeping the required bone forming value. The new S shape wave of metal welded bellow of mechanical seal are designed based on the the optimization results through this method. The S shape and V shape both were analyzed with FEM method. The same boundary conditions were given for two types of wave. The results are shown that the stresses mainly concentrated on the welded area. It is interesting that the value of the stresses of the two types of wave basically same. However, compressibility of the two types of wave is very different at the same computation stage. The compressibility of S shape wave was higher than V shape.

Study on Self-Consistent Mesh Generating Method of Hexahedron Element Based on the Local Waveform Method with Damping

Three-dimensional finite element method (FEM) is widely used as an effective numerical simulation technique to solve the complex engineering problem. In the FEM simulation technique at first it needs to discrete the problem. However, the almost all of the engineering problem have very complicated structure and shape, so that the mesh generation also have much difficulty. Furthermore, the correct generation of mesh is one of the most significant issues that directly affect to the accuracy of the FEM simulation. Though in extensive commercial software have an excellent automatic mesh generating system, however the problem of hexahedral automatic mesh generation and its adaptation are not enough to solve for practical applications, because for the mesh generation of complex shape is very difficult and still intensive labor work by hand. In this paper we present a new method to generate an appropriate mesh using existing regular hexahedral mesh and hexahedron mesh generation technique. This technique based on the wave transmits theory with damp named Waveform Mesh Generating (WMG) method. The results shown that the complex shaped FEM discrete hexahedral mesh model generated when shape of the side apply to regular mesh side as a waveform constraint.

Fracture Mechanics Parameters Governing Delaminated Interfaces in IC Packages Subjected to Unsteady Thermal Stress

In a delaminated interface, the stress field near a crack t ip will always be in a mixed-mode state. It was assumed that the initial defects wer e generated at the corner of an epoxy molding die pad. A three-dimensional (3-D) finite element analysis was carried out to evaluate the strain energy release rate (SERR) of the delaminated inter face in IC packages subjected to non-uniform thermal stresses. The SERR was evaluated by a modifie d crack-closure integral (MCCI) and a virtual crack extension method (VCEM). A stress-i ntensity factor (SIF) was discussed using 3-D and 2-D VCEM. The VCEM evaluated the SIF of t he in erface crack under mixed-mode loading accurately. Since K1 value is smaller than K2 value, the growth of delamination is governed by the K2 value. Introduction Since an IC package is a structure with silicon chip and leadfram e packed together by resin, high stresses often arise in the interface due to large mismatch i n the coefficient of thermal expansion between the two dissimilar materials. Delamination may be generat d at he interface in a heat cycle test or a reflow soldering process. In a reflow process the IC package is heated up to a temperature of 200°C or more at the time of solder mounting. At this time, the int rface delamination is generated from interface defects such as a reflow crack and voids in the IC packages. The interface delamination causes fatal damage on the packages. Therefore, in st ructural design and material selection of the packages, it is very important to evaluate the str ength of the interface quantitatively. The stress conditions near the crack tip are always in a mixed mode, and a numerical analysis is required for the delaminating interface. In the case of homogeneous materials, K1 and K2 which are the stress-intensity factors (SIF) of a mixed-mode state are separately evaluated from GI and GII which are the strain energy release rates (SERR). However both K1 and K2 contain GI and GII of dissimilar materials. Therefore, K1 and K2 cannot be evaluated from GI and GII alone. The modified crack-closure integral (MCCI) evaluates only the SERR and is used as the simplest evaluation method of the S ERR under a mixed mode state such as a dissimilar material interface crack or a slant crack. Although the MCCI is considered to be a very effective technique from the view point of ease in progr amming, the inaccuracy of the Key Engineering Materials Online: 2003-07-15 ISSN: 1662-9795, Vols. 243-244, pp 393-398 doi:10.4028/www.scientific.net/KEM.243-244.393

Effective Adaptation of Hexahedral Mesh using Local Refinement and Error Estimation

3-D finite element method (FEM) is widely used as an effecti v numerical simulation technique. In the simulation technique, accuracy is one of the most signi ficant issues. In case of FEM, the accuracy is affected by number of freedom and shape of each ele ment. Generally, a fine mesh can provide more accurate result than a coarse one, and needs more time of calculation and more computer resources (memory, CPU time and disk space). Recently te trahedral automatic mesh generation and adaptive mesh generation become advanced and practical. He xahedral mesh generation and its adaptation are not enough to use for practical applic ations, because its mesh generation is very difficult and still intensive labor work by hand. In recent years local mesh refinement for a tetrahedral element is widely used in order to avoid failure of mesh regeneration. Therefore one of the best ways to control quality of a hexahedral me sh is applying local mesh refinement to existing hexahedral mesh. In this study we present a method to generate an appropriate mesh for users demand using existing hexahedral mesh and hexahedron me sh and hexahedral automatic local refinement technique.

Dynamics and Numerical Modeling of Sandy Desert Morphology Caused by Aeolian Transport of Sand Particles

Wind caused the much sediment fluxes leading to both erosion and deposits in the sandy desertification area, and the much kind of beautiful sandy desert morphologies are formed. This is really crucial to the development of the dynamic behaviour of aeolian transport of sand particles. The sand desert morphologies are representing significant information archives for understanding the desertification problem. Dynamics and numerical modeling provides an essential tool for studying the aeolian transport of sand particle and morphology of sand desert such as ripple and dune. In this study, the mathematical models based on the dynamics are analyzed by considering the several keys as saltation, creep, suspension, avalanche and its threshold condition etc. for sand morphology forming processes. Then due to sand flow field real characteristics, the establishing process of stream flow field are analyzed, and the implication relationships as well as the coupling process between uniform stream flow field and the sand flow field are analyzed. Finally, the sand flow field models is discretized, and different kinds of sandy desert morphology are simulated by considering the sand particle size and mass in fixed, semi-fixed and free sand flow field area.

Numerical Study on Aeolian Sand Ripples Forming and Moving Process in Desert Highway

In this paper, the sand break into highway problem in desert, which is caused by the sand flow blown by wind, is studied. The mathematical models are introduced by considering the fixed, semi-fixed and free sand desert fields based on the fluid dynamics and the sand particle dynamics. Different kinds of numerical models are made by changing the desert highway height, wind flow direction and its uniformity. The weak coupling method is used due to spatial relationships between air flow field and the sand flow field. Finally, by coupling the airflow field and sand flow field with desert highway, the numerical simulations of sand forming process on desert highway are conducted. The numerical results shown, that the wind blown sand breaks into highway easier when wind direction perpendicular highway and if the highway height higher than the range size of the sand surface the wind blown sand break into highway is more difficult.

Experimental Study on Embryo Skeletal Development to Postnatal Growth Process of Rabbit Thighbone

Bone forming phenomenon is an exquisitely genetic programmed and dynamic process that occur from early embryo skeletal development to postnatal growth and culminating in the formation of highly variable and complex but perfect optimized structures. In this study the high resolution imaging techniques such as computerized tomography (CT) is used to obtain quantitative information about the progressive changes in three-dimensional (3D) skeletal morphology and density of rabbit thighbone during early embryo skeletal development to postnatal growth. Then the changes of the thighbone volume, shape and density during the bone growth process are evaluated by using the 3D images reconstruction method, and the growing direction of the thighbone structure is also evaluated. The effects of genetic and environmental complications to optimized skeletal patterns of bone are discussed.

Study on the Gear Modeling in SPH Analysis

This article presents the gear modeling method in dynamic mechanical analysis using SPH (Smoothed Particle Hydrodynamics) analysis method. The parameter equations of the transition curve of gear root and the other parts of gear are decided. The 3D discrete particles model is established based on the parameter equations. The SPH pre-process program of global and local dividing is developed. The error between the divided discrete particles and theoretical profiles of the gear has been analyzed. The analysis results show that this modeling method is a relatively better method and the correct SPH discrete particles can be divided by this method.