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  • Title/Summary/Keyword: Finite Element Method, FEM

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Effective Volume of the Korea Research Institute of Standards and Science Free Air Chamber L1 for Low-Energy X-Ray Measurement

  • Chul-Young Yi;Yun Ho Kim;Don Yeong Jeong
    • Progress in Medical Physics
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    • v.33 no.1
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    • pp.1-9
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    • 2022
  • Purpose: To evaluate the effective volume of the Korea Research Institute of Standards and Science free air chamber (KRISS FAC) L1 used for the primary standard device of the low-energy X-ray air kerma. Methods: The mechanical dimensions were measured using a 3-dimensional coordinate measuring machine (3-d CMM, Model UMM 500, Carl Zeiss). The diameter of the diaphragm was measured by a ring gauge calibrator (Model KRISS-DM1, KRISS). The elongation of the collector length due to electric field distortion was determined from the capacitance measurement of the KRISS FAC considering the result of the finite element method (FEM) analysis using the code QuickField v6.4. Results: The measured length of the collector was 15.8003±0.0014 mm with a 68% confidence level (k=1). The aperture diameter of the diaphragm was 10.0021±0.0002 mm (k=1). The mechanical measurement volume of the KRISS FAC L1 was 1.2415±0.0006 cm3 (k=1). The elongated length of the collector due to the electric field distortion was 0.170±0.021 mm. Considering the elongated length, the effective measurement volume of the KRISS FAC L1 was 1.2548±0.0019 cm3(k=1). Conclusions: The effective volume of the KRISS FAC L1 was determined from the mechanically measured value by adding the elongated volume due to the electric field distortion in the FAC. The effective volume will replace the existing mechanically determined volume in establishing and maintaining the primary standard of the low-energy X-ray.

Development of Subbase Analysis Model Considering Stress Dependency (응력의존성을 고려한 보조기층 해석모델 개발)

  • Kim, Ji Hwan;Kang, Beong Joon;Lee, Jun Hwan;Choi, Jun Seong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.3D
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    • pp.331-338
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    • 2008
  • Road pavements consist of layered structure and each layer is made of various materials. The load responses of pavement structures are very sensitive to properties of subbase materials. Successful pavement design, therefore, depends on the method and the accuracy of measuring material properties, and it requires realistic description of the behavior of layered materials. Resilient modulus (MR) is widely used properties representing pavement structure materials. In this study, we collected data for mechanical characteristics of subbase materials that were used in domestic construction and adopted them to form a constitutive equation of subbase MR value. Proposed model was evaluated through the finite element analysis.

Evaluation of Fatigue Endurance on Expansion Joint Manufactured Fe-Mn Damping Alloy (Fe-Mn 제진 금속을 적용한 신축이음장치의 피로 내구성 평가)

  • Kim, Ki-Ik;Kim, Young-Jin;Ahn, Dong-Geun;Kim, Cheol-Hwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4D
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    • pp.483-489
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    • 2009
  • The endurance of expansion joint manufactured the Fe-Mn damping alloy reducing noise and vibration is analyzed into FEM (Finite Element Method) and fatigue test. The fatigue test have been performed using the expansion joint manufactured Fe-Mn damping alloy and the hydraulic actuator (25tonf). And the results of fatigue test show that the maximum strength is 237.6 MPa. Also that is 56.6 percent of Fe-Mn damping alloy yield strength (420 MPa). The loading plate size is prepared 57.7cm×23.1cm and the loading plate's set position is located on expansion joint. The expansion joint manufactured the Fe-Mn damping alloy had not presented breaking behavior against 2,000,000 times fatigue test and identified the fatigue endurance.

Impact Tensile Properties and Intergranular Fracture Behavior with Strain Rate Variations of Al-M g-X (X = Cr,Si) Alloy

  • Chang-Suk Han;Min-Gyu Chun;Sung-Soon Park;Seung-In Lim
    • Korean Journal of Materials Research
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    • v.34 no.7
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    • pp.330-340
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    • 2024
  • Al-Mg-Si alloys are light weight and have excellent corrosion resistance, and are attracting attention as a liner material for high-pressure hydrogen containers in hydrogen fuel cell vehicles. Because it has excellent plastic hardening properties, it is also applied to car body panel materials, but it is moderate in strength, so research to improve the strength by adding Si-rich or Cu is in progress. So far, the authors have conducted research on the intergranular fracture of alloys with excessive Si addition from the macroscopic mechanical point of view, such as specimen shape. To evaluate their impact tensile properties, the split-Hopkinson bar impact test was performed using thin plate specimens of coarse and fine grain alloys of Al-Mg-X (X = Cr,Si) alloy. The effect of the shape of the specimen on the characteristics was studied through finite element method (FEM) analysis. As a result, it was found that the intergranular fracture of the alloy with excessive Si depended on the specimen width (W)/grain size (d), which can be expressed by the specimen size and grain size. As W/d decreases, the intergranular fracture transforms into a transgranular fracture. As the strain rate increases, the fracture elongation decreases, and the fracture surface of the intergranular fracture becomes more brittle. It was confirmed that intergranular fracture occurred in the high strain rate region even in materials with small grain sizes.

Development and Verification of FEM Analysis Model for Precast Claddings-UHPC Ribs in Apartment Buildings (공동주택 PC외피-UHPC리브 시스템의 유한요소해석 모델 제작과 검증)

  • Jin, Su-Min;Jo, Hyerim;An, Hyo-Seo;Na, Geum-Ok;Yoo, Young-Jong;Kim, Hyung-Geun;Lee, Kihak
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.6
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    • pp.295-303
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    • 2024
  • The precast concrete (PC) method allows for simple assembly and disassembly of structures; however, ensuring airtight connections is crucial to prevent energy loss and maintain optimal building performance. This study focuses on the analytical investigation of the shear capacity of precast ultra-high-performance concrete (UHPC) ribs combined with standard concrete PC cladding walls. Five specimens were tested under static loading conditions to evaluate their structural performance and the thermal behavior of the UHPC rib shear keys. Test results indicated that the specimens exhibited remarkable structural performance, with shear capacity approximately three times greater than that of standard concrete. Numerical models were subsequently developed to predict the shear capacity of the shear keys under various loading conditions. A comparison between the experimental results and finite element (FE) models showed a maximum strength difference of less than 10% and a rib displacement error of up to 1.76 mm. These findings demonstrated the efficiency of the FE model for the simulation of the behavior of structures.

Evaluation for Progressive Collapse Resistance of a RC Flat Plate System Using the Static and Dynamic Analysis (정적 및 동적 해석을 통한 철근콘크리트 무량판 구조의 연쇄 붕괴 저항 성능 평가)

  • Lee, Seon-Woong;Shin, Sung-Woo
    • Journal of the Korea Concrete Institute
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    • v.23 no.2
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    • pp.245-252
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    • 2011
  • Currently, the design guidelines for the prevention of progressive collapse are not available in Korea due to the lack of study efforts in progressive collapse resistance evaluation of RC flat plate system. Therefore, in this study, three types of analysis were conducted to evaluate the progressive collapse resistance of a RC flat plate system. A linear static analysis was carried out by comparing the demand-capacity ratio (DCR) differences of the systems using the alternate load path method, which is the guideline of GSA. A dynamic behavior was investigated by checking the vertical deflection after removal of the column using the linear dynamic analysis. Lastly, a maximum load factor was investigated using the nonlinear static analysis. The finite element (FE) analyses were conducted using various parameters to analyze the results obtained using effective beam width (EB) model and plate element FEM (PF) model. This study results showed that the strength contributions of the slab in the EB models are underestimated compared to those obtained from the PF models. Therefore, a detailed FE analysis considering the slab element is required to thoroughly estimate the progressive collapse resisting capacity of flat plate system. The scenario of the corner column (CC) removal is the most dangerous conditions where as the scenario of the inner column (IC) removal is the least dangerous conditions based on the consideration of various parameters. The analysis results will allow more realistic evaluations of progressive collapse resistance of RC flat plate system.

Modeling of Hemodynamics in Stenosed Artery (협착 동맥혈관의 혈류유동 모델링)

  • Kim, Seong-Jong;Park, Young-Ran;Kim, Shagn-Jin;Kang, Hyung-Sub;Kim, Jin-Shang;Oh, Sung-Hoon;Kang, Sung-Jun;Kim, Gi-Beum
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.5
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    • pp.2285-2290
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    • 2012
  • This study is about atherosclerosis which occupies the highest rate in many diseases people have and we have studied about atherosclerosis for abdominal aorta. Atherosclerosis is the phenomenon which blood vessel gets narrower, harder and thicker due to the stenosis of colesterol in blood vessel. If it becomes worse, arteries will be hard and blood can't flow smoothly, and even it can reach to death. In this study, the geometric models of the considered stenotic blood flow are two different types of constriction of cross-sectional area of blood vessel; 20 and 45% of constriction in each elastic wall and rigid wall. We have modeled by using finite element method to observe the changes of velocity and pressure. In case of the diameter of blood vessel decreased 45% in elastic wall model, the values of velocity and pressure were higher than the case of 20% and in case of the diameter of blood vessel decreased 45% in rigid wall model, the values of velocity and pressure were higher than the case of 20%. In cases of elastic wall models of the diameters of blood vessels decreased each of 20% and 45%, recirculation zones appeared. This results show understanding of hemodynamic properties depending on stenosed blood vessels.

Evaluation of near surface Vs distribution by using SPT uphole method (SPT 업홀기법을 이용한 지반의 2차원 전단파 속도 분포 도출)

  • Kim, Dong-Soo;Bang, Eun-Seo;Kim, Jong-Tae
    • 한국지구물리탐사학회:학술대회논문집
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    • 2005.09a
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    • pp.93-116
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    • 2005
  • SPT-Uphole tomography method was introducedand verified in this paper. In SPT-Uphole method, SPT (Standard Penetration Test) which is common in site investigation, was used as a source and several surface geophones in line were used as receivers. Shear wave velocity (Vs) distribution map which has triangular shape around the boring point can be obtained by tomography inversion. The factors for obtaining reliable result of SPT-Uphole tomography are exact travel time information and accurate inversion method. To establish of the SPT-Uphole tomography procedure, the most reliable method for obtaining exact travel time information and verification of tomography inversion method were studied by using theoretical travel time information and finite element method (FEM) analysis. finally, SPT-Uphole tomography method was performed at the weathered soil site in Kimje. By comparing with several boring data including SPT-N value, feasibility of this method was verified in the field.

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A Practical Analysis Method for the Design of Piled Raft Foundations (말뚝지지 전면기초의 실용적 근사해석법 개발)

  • Song, Young Hun;Song, Myung Jun;Jung, Min Hyung;Park, Yung Ho
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.1
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    • pp.83-91
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    • 2017
  • In case of estimation of settlement for the piled-raft foundation, it is necessary to consider interaction among raft, piles and soil. But, simple analytic methods usually are not applicable to considering this complicated interaction. In this study, a computer-based approximate analytic method, HDPR, was developed in consideration of above mentioned interaction in order to analysis of settlement for the piled-raft foundation. The finite element method was applied to raft analysis by means of the Mindlin plate theory, and soil and piles were modeled as springs which were connected with their raft. The linear spring which can consider multi layered soil and the non-linear spring were applied to soil springs and pile springs, respectively. The raft-piles-soil interaction was reflected to each spring. In order to verify the developed analytic method, it was compared and analyzed with 3D FEM analysis, existing approximate analytic method and site monitoring data. As a result, the developed analytic method showed reasonable results of settlement estimations of raft and piles for each case. From a practical point of view, it is confirmed that this analytic method is able to apply for analysis and design of the piled-raft foundation.

Novel Intensity-Based Fiber Optic Vibration Sensor Using Mass-Spring Structure (질량-스프링 구조를 이용한 새로운 광세기 기반 광섬유 진동센서)

  • Yi, Hao;Kim, Hyeon-Ho;Choi, Sang-Jin;Pan, Jae-Kyung
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.6
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    • pp.78-86
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    • 2014
  • In this paper, a novel intensity-based fiber optic vibration sensor using a mass-spring structure, which consists of four serpentine flexure springs and a rectangular aperture within a proof mass, is proposed and its feasibility test is given by the simulation and experiment. An optical collimator is used to broaden the beam which is modulated by the displacement of the rectangular aperture within the proof mass. The proposed fiber optic vibration sensor has been analyzed and designed in terms of the optical and mechanical parts. A mechanical structure has been designed using theoretical analysis, mathematical modeling, and 3D FEM (Finite Element Method) simulation. The relative aperture displacement according to the base vibration is given using FEM simulation, while the output beam power according to the relative displacement is measured by experiment. The simulated sensor sensitivity of 15.731μW/G and detection range of ±6.087G are given. By using reference signal, the output signal with 0.75% relative error shows a good stability. The proposed vibration sensor structure has the advantages of a simple structure, low cost, and multi-point sensing characteristic. It also has the potential to be made by MEMS (Micro-Electro-Mechanical System) technology.