• Structural Engineering and Mechanics
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• 제76권3호
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• pp.325-336
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• 2020

In this study, the continuous and discontinuous contact problems of functionally graded (FG) layer resting on a rigid foundation were considered. The top of the FG layer was loaded by a distributed load. It was assumed that the shear modulus and the density of the layer varied according to exponential functions along the depth whereas the the Poisson ratio remained constant. The problem first was solved analytically and the results were verified with the ones obtained from finite element (FE) solution. In analytical solution, the stress and displacement components for FG layer were obtained by the help of Fourier integral transform. Critical load expression and integral equation for continuous and discontinuous contact, respectively, using corresponding boundary conditions in each case. The finite element solution of the problem was carried out using ANSYS software program. In continuous contact case, initial separation distance and contact stresses along the contact surface between the FG layer and the rigid foundation were examined. Separation distances and contact stresses were obtained in case of discontinuous contact. The effect of material properties and loading were investigated using both analytical and FE solutions. It was shown that obtained results were compatible with each other.

• 한국지반공학회논문집
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• 제22권10호
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• pp.5-20
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• 2006

본 논문에서는 지하수위 하에서 터널이 시공되는 조건을 대상으로 응력-간극수압 연계 유한요소해석 수행시 모델링 측면에서 중요하게 다뤄져야 하는 내용을 고찰하였다. 먼저 연계해석 수행시 요구되는 지하수위 저하와 지반거동과의 관계에 대한 배경 이론을 알아보았으며, 이를 토대로 모델링 측면에서 해석결과에 영향을 미칠 수 있는 다양한 인자들을 선정하고, 선정된 영향인자에 대한 매개변수 연구를 수행하였다. 지하수위 저하가 동반되는 터널 시공조건에서의 유한요소석 모델링 결과는 지반의 불포화특성 고려여부가 가장 큰 영향을 미치는 것으로 나타났으며 본 고에서는 결과를 종합하여 연계해석 모델링시 중요하게 검토되어야 고려사항을 제시하였다.

• Steel and Composite Structures
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• 제46권3호
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• pp.353-366
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• 2023

This paper presents a finite-element analysis (FEA) of aluminum alloy rectangular hollow sections (RHSs) and square hollow sections (SHSs) with circular through-openings under three-point and four-point bending. First, a finite-element model (FEM) was developed and validated against the corresponding test results available in the literature. Next, using the validated FE models, a parametric study comprising 180 FE models was conducted. The cross-section width-to-thickness ratio (b/t) ranged from 2 to 5, the hole size ratio (d/h) ranged from 0.2 to 0.8 and the quantity of holes (n) ranged from 2 to 6, respectively. Third, results obtained from laboratory test and FEA were compared with current design strengths calculated in accordance with the North American Specifications (NAS), the modified direct strength method (DSM) and the modified Continuous strength method (CSM). The comparison shows that the modified CSM are conservative by 15% on average for aluminum alloy RHSs and SHSs with circular through-openings subject to bending. Finally, a new design equation is proposed based on the modified CSM after being validated with results obtained from laboratory test and FEA. The proposed design equation can provide accurate predictions of flexural capacities for aluminum alloy RHSs and SHSs with circular through-openings.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.458-462
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• 2005

This paper deal with the optimal lamination condition of cylindrical shell applied new composite URN300 for a study of composite empirical formula. Finite element analyses for isotropic materials considered element numbers and boundary conditions are compared with existing empirical formulas to apply FE analysis for composite. And composite tensile test is done to know the composite material applied FE analysis for composite. The results of FE analyses for isotropic materials have indicated that Optimal element number and boundary condition were 1600 and both simple support. These conditions were applied in composite FE analyses. Ply orientations and lamination patterns in FE analyses for composite were considered. Ply orientations are $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;and\;90^{\circ}$. Lamination patterns are $[\pm\theta/0/90]_{14s]$ and $[\pm\theta_{14}/0_{14}/90_{14}]_s$ in FE analysis. Lamination pattern $[\pm\theta_{14}/0_{14}/90_{14}]_s$ is the equivalent model of $[\pm\theta/0/90]_{14s}$. At the result of this study, the FE analyses for composite have indicated that the optimized ply orientation $75^{\circ}$ is and real model must use in FE analysis for accurate results.

• Structural Monitoring and Maintenance
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• 제3권4호
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• pp.377-393
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• 2016

The present work develops an expert system for detecting and predicting the crude oil types and properties at normal temperature ${\theta}=25^{\circ}C$, by evaluating the dielectric properties of the fluid transfused inside glass fiber reinforced epoxy (GFRE) composite pipelines, by using electrical capacitance sensor (ECS) technique, then used the data measurements from ECS to predict the types of the other crude oil transfused inside the pipeline, by designing an efficient artificial neural network (ANN) architecture. The variation in the dielectric signatures are employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such problem. ECS consists of 12 electrodes mounted on the outer surface of the pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes by ANSYS and MATLAB, which are combined to simulate sensor characteristic. Radial Basis neural network (RBNN), structure is applied, trained and tested to predict the finite element (FE) results of crude oil types transfused inside (GFRE) pipe under room temperature using MATLAB neural network toolbox. The FE results are in excellent agreement with an RBNN results, thus validating the accuracy and reliability of the proposed technique.

• 한국생산제조학회지
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• 제22권6호
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• pp.931-936
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• 2013

Recently, the use of large-electron-beam polishing for polishing complex metal surfaces has been proposed. In this study, the temperature induced by a large electron beam was predicted using the heat transfer theory. A finite element (FE) model of a continuous wave (CW) electron beam was constructed assuming Gaussian distribution. The temperature distribution and melting depth of an SUS304 sample were predicted by changing electron-beam polishing process parameters such as energy density and beam velocity. The results obtained using the developed FE model were compared with experimental results for verifying the melting depth prediction capability of the developed FE model.

• 대한기계학회논문집A
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• 제30권5호
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• pp.568-575
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• 2006

The present paper provides plastic limit load solutions of axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3-D) finite element (FE) limit analysis using elastic-perfectly-plastic behavior. As a loading condition, axial tension, global bending moment, internal pressure, combined tension and bending and combined internal pressure and bending are considered for circumferential through-wall cracked pipes, while only internal pressure is considered for axial through-wall cracked pipes. Especially, more emphasis is given for through-wall cracked pipes subject to combined loading. Comparisons with existing solutions show a large discrepancy in short through-wall crack (both axial and circumferential) for internal pressure. In the case of combined loading, the FE limit analyses results show thickness effect on limit load solutions. Furthermore, the plastic limit load solution for circumferential through-wall cracked pipes under bending is applied to derive plastic $\eta\;and\;{\gamma}$-factor of testing circumferential through-wall cracked pipes to estimate fracture toughness. Being based on detailed 3-D FE limit analysis, the present solutions are believed to be meaningful fur structural integrity assessment of through-wall cracked pipes.

• 한국정밀공학회지
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• 제32권6호
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• pp.509-515
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• 2015

Recent trends to reduce the size of mobile electronics products have driven miniaturization of various components, including screw parts for assembling components. Considering that the size reduction of screws may degenerate their joining capabilities, the size reduction should not be limited to the thread region but should be extended to its head region. The screw head is usually manufactured by forging in which a profiled punch presses a billet so that plastic deformation occurs to form the desired shape. In this study, finite element (FE) analysis was performed to simulate the forging process of a subminiature screw; a screw head of 1.7 mm diameter is formed out of a 0.82 mm diameter billet. The FE analysis result indicates that this severe forging condition leads to a generation of folding defects. FE analyses were further performed to find appropriate punch design parameters that minimize the amount of folding defects.

• Steel and Composite Structures
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• 제26권3호
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• pp.361-373
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• 2018

This paper presents the development of finite element (FE) models to simulate the behavior of diagonally stiffened steel plate shear wall systems (SPSWs) with differently shaped openings subjected to a cyclic load. This walling system has the potential to be used for shear elements that resist lateral loads in steel-framed buildings. A number of $\text\tiny{^1/_2}$-scale one-story buildings that were un-stiffened, stiffened and stiffened with opening SPSWs are modeled and simulated using the finite element method based on experimental data from previous research. After validating the finite element (FE) models, the effects of infill plate thickness on the cyclic behavior of steel shear walls are investigated. Furthermore, triple diagonal stiffeners are added to the steel infill plates of the SPSWs, and the effects are studied. Moreover, the effects of a number of differently shaped openings applied to the infill plate are studied. The results indicate that the bearing capacity and shear resistance are affected positively by increasing the infill plate thickness and by adding triple diagonal stiffeners. In addition, the cyclic behavior of SPSWs is improved, even with an opening in the SPSWs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.824-830
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• 2003

The Power Flow Finite Element Method(PFFEM) offers very promising results in predicting the vibration responses of system structures, and the first PFFEM software, PFADS has been developed in Seoul National University for the vibration predictions and analysis of coupled system structures in medium-to-high frequency ranges. PFFEM is numerical method which solves energy governing equation using finite element technique for complicated structures where the exact solutions are not available. Through the upgrades, the current version PFADS R3 could cover the general beam and plate structures including various kinds of beam-plate rigid joints, spring-damper connection and rigid body connection within beam and plate in addition. This software is composed of three parts; translator, model converter and solver. The translator makes its own FE-model from bulk data of commercial FE software, and the model converter is used to convert FE-model to PFFE-model automatically. The solver calculates vibrational energy density and intensity for PFFE-model by solving global matrix equations of PFFEM. For the applications of PFADS R3, two vehicle models and a container model are examined with respect to major parameters, and reliable results are obtained.