• Title, Summary, Keyword: FEM

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Tuning Fork Modal Analysis and Sound Pressure Calculation Using FEM and BEM

  • Jarng, Soon-Suck;Lee, Je-Hyung
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.3E
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    • pp.112-118
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    • 2002
  • An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method (FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the trend of the change of the modal frequencies was examined with the variation of the tuning fork length and width. An formula for the natural frequencies-tuning fork length relationship were derived from the numerical analysis results. Finally the BEM was used for the sound pressure field calculation from the structural displacement data.

Surface Temperature in Sliding Systems Using the En Finite Element Analysis (FFT-FEM을 이용한 윤활 기구에서 표면온도에 관한 연구)

  • 조종두;안수익
    • Tribology and Lubricants
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    • v.16 no.3
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    • pp.218-222
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    • 2000
  • Finite element equations by using fast Fourier transformation were formulated for studying temperatures resulting from frictional heating in sliding systems. The equations include the effect of velocity of moving components. The program developed by using FFT-FEM that combines Fourier transform techniques and the finite element method, was applied to the sliding bearing system. Numerical prediction obtained by FFT-FEM was in an excellent agreement of experimental temperature measurements.

Combination of Different Numerical Methods for Efficient Thermal Stress Analysis of Casting Process (주조공정에서의 효율적인 열응력 해석을 위한 이종해석기법의 연계)

  • Kwak, Si-Young;Lim, Chae-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.1051-1057
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    • 2010
  • This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.

Design of a LTCC Front End Module with Power Detecting Function (전력 검출 기능을 포함하는 LTCC 프런트 엔드 모듈 설계)

  • Hwang, Mun-Su;Koo, Jae-Jin;Koo, Ja-Kyung;Lim, Jong-Sik;Ahn, Dal;Yang, Gyu-Yeol;Kim, Jun-Chul;Kim, Dong-Su;Park, Ung-Hee
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.8
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    • pp.844-853
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    • 2008
  • This paper describes the design of a FEM(Front End Module) having power detection function for mobile handset application. The designed FEM consists of a MMIC(Monolithic Microwave Integrated Circuits) power amplifier chip, SAW Tx filter and duplexer, diode power detector and stripline matching circuit. An LTCC(Low Temperature Co-fired Ceramics) technology is adopted for miniaturized FEM. The frequency band is $824{\sim}869$ MHz which is the uplink Tx band of the CDMA mobile system. The size of designed FEM is $7.0{\times}5.5{\times}1.5\;mm^3$, which is an ultra-small size even though the power detector circuit is included. All sub-components of FEM have been developed and measured in advance before being integrated into FEM. The measured output power and gain are 27 dBm and 27 dB, respectively. In addition, the measured ACPR characteristics are 46.59 dBc and 55.5 dBc at 885 kHz and 1.98 MHz offset, respectively.

Detection of Methicillin-Resistant Staphylococcus aureus by In Vitro Enzymatic Amplification of MecA and FemA Gene (메티실린 내성 황색 포도상 구균에서 mecA, femA 유전자의 임상적 의의)

  • Park, Jung-Eun;Kim, Taek-Sun;Park, Su-Sung;Kim, Eun-Ryoung;Kim, Il-Su;Ann, Il-Young;Kim, Young-Jin;Kim, Jae-Jong;Kang, Sung-Ok;Park, Han-Ho
    • Pediatric Infection and Vaccine
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    • v.3 no.2
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    • pp.133-138
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    • 1996
  • Purpose : In the treatment of MRSA infection, rapid detection of MRSA is extremely important. The mecA gene codes the new drug resistant polypeptides called PBP2' which mediates the clinically relevant resistance to all beta-lactam antibiotics. The identical mecA gene has been found in coagulase-negative staphylococcus with the methicillin-resistant phenotype. On the other hand, the femA gene was absent from coagulase negative staphylococcus strains with the methicillin resistant phenotype. This study is aimed at early detection and definite diagnosis of MRSA. Methods : A total of 24 MRSA strains were studied. All strains were tested for antimicrobial susceptibility and purified DNA. We amplified both mecA and femA genes by PCR in 24 strains. Results : In MRSA all the 16 strains (100%) carried femA gene and 11 strains (68.7%) carried mecA gene. In contrast, in methicillin sensitive staphylococcus all the 8 strains (100%) carried femA and only 3 strains (37.5%) were detected mecA. Conclusions : As results, there are difference in the phenotype and genotype of methicillin resistance by PCR of mecA and femA. Such disparities between methicillin resistance and the presence of mecA gene suggest the presence of control gene of the mecA.

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Structural identification of Humber Bridge for performance prognosis

  • Rahbari, R.;Niu, J.;Brownjohn, J.M.W.;Koo, K.Y.
    • Smart Structures and Systems
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    • v.15 no.3
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    • pp.665-682
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    • 2015
  • Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

Prediction of Cutting Stress by 2D and 3D-FEM Analysis and Its Accuracy (2차원과 3차원 FEM 해석에 의한 절단응력의 해석 및 정도)

  • 장경호;이상형;이진형;강재훈
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.16 no.3
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    • pp.261-269
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    • 2003
  • Steel bridges, which have been damaged by load and corrosion, need repair or strengthening. In general, before the repair welding procedure, cutting procedure carry out. Therefore, the investigating of the behavior of stress generated by cutting is so important for safety of structure. Residual stress produced by gas cutting was analyzed using 2D and 3D thermal elasto plastic FEM. According to the results, the magnitude of temperature was analyzed by 2D FEM is smaller than that was analyzed using the 3D FEM program at the start and end edge of flange. And the magnitude and distribution of residual stress of perpendicular to the cutting line was analyzed by the 2D FEM program was similar to that was analyzed by the 3D FEM program. Therefore, it is possible to predict of cutting stress by 2D and 3D FEM.

Ring-Rolling Design of a Large-Scale Ti-6Al-4V alloy (대형 Ti-6Al-4V 합금의 Ring-Rolling 공정설계)

  • Yeom, J.T.;Jung, E.J.;Kim, J.H.;Lee, D.G.;Park, N.K.;Choi, S.S.;Lee, C.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.373-376
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    • 2006
  • The ring rolling design for a large-scale Ti-6Al-4V alloy ring was performed with a calculation method and FEM simulation. The ring rolling design includes geometry design and optimization of process variables. The calculation method was to determine geometry design such as initial billet and blank size, and final rolled ring shape. A commercial FEM code, SHAPE was used to simulate the effect of process variables in ring rolling on the distribution of the internal state variables such as strain, strain rate and temperature. In order to predict the forming defects during ring rolling, the process-map approach based on Ziegler's instability criterion was used with FEM simulation. Finally, an optimum process design to obtain sound Ti-6Al-4V rings without forming defects was suggested through combined approach of Ziegler's instability map and FEM simulation results.

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Incremental Sheet Forming of Complex Geometry Shape and Its Optimization Using FEM Analysis (복잡한 형상제품의 인크리멘탈 성형과 FEM을 이용한 공정 최적화)

  • Nguyen, D.T.;Park, J.G.;Lee, H.J.;Kim, Y.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.207-212
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    • 2009
  • In order to optimize the press formability of incremental sheet forming for complex shape (e.g human face), a combination of both CAM and FEM simulation, is implemented and evaluated from the histories of stress and strain value by means of finite element analysis. Here, the results, using ABAQUS/Explicit finite element code, are compared with fracture limit curve (FLC) in order to predict and optimize the press formability by changing parameters of tool radius and tool down-step according to the orthogonal array of Taguchi's method. Firstly, The CAM simulation is used to create cutter location data (CL data). This data are then calculated, modified and exported to the input file format required by ABAQUS through using MATLAB programming. The FEM results are implemented for negative incremental sheet forming and then investigate by experiment.

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TUNING Fork Analysis and Design by FEM AND BEM (FEM과 BEM을 사용한 소리굽쇠 특성 해석 및 설계)

  • Jarng, Soon-Suck;Kwon, You-Jung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1201-1204
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    • 2003
  • An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method(FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the trend of the change of the modal frequencies was examined with the variation of the tuning fork length and width. An formula for the natural frequencies-tuning fork length relationship were derived from the numerical analysis results. Finally the BEM was used fur the sound pressure field calculation from the structural displacement data.

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