• Title/Summary/Keyword: Micro-Finite Element Analysis

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Methodology for numerical evaluation of fracture resistance under pinch loading of spent nuclear fuel cladding containing reoriented hydrides

  • Seyeon Kim;Sanghoon Lee
    • Nuclear Engineering and Technology
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    • v.56 no.6
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    • pp.1975-1988
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    • 2024
  • It is important to maintain cladding integrity in spent nuclear fuel management. This study proposes a numerical analysis method to evaluate the fracture resistance of irradiated zirconium alloy cladding under pinch load known to cause Mode-III failure. The mechanical behavior and fracture of the cladding under pinch loading can be evaluated by a Ring Compression Test (RCT). To simulate the fracture of hydride precipitates, zirconium matrix, and Zr/hydride interfaces under the stress field generated by RCT, a micro-structure crack propagation simulation method based on Continuum Damage Mechanics (CDM) has been proposed. Our RCT simulation model was constructed from microscopic images of irradiated cladding. In this study, we developed an automated process to generate a pixel-based finite element model by separating the hydride precipitates, zirconium matrix, and interfaces using an image segmentation method. The appropriate element size was selected to ensure the efficiency and accuracy of a crack propagation simulation. The load-displacement curves and strain energies from RCT were compared and analyzed with the simulation results of different element sizes. The finalized RCT simulation model can be used to establish the failure criterion of fuel rods under pinch loading. The advantages and limitations of the proposed method are fully discussed here.

A Study on $\mu$BGA Solder Joints Reliability Using Lead-free Solder Materials

  • Shin, Young-Eui;Lee, Jun-Hwan;Kon, Young-Wook;Lee, Chong-Won;Yun, Jun-Ho;Jung, Seug-Boo
    • Journal of Mechanical Science and Technology
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    • v.16 no.7
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    • pp.919-926
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    • 2002
  • In this study, the numerical prediction of the thermal fatigue lie? of a $\mu$BGA (Micro Ball Grid Array) solder joint was focused. Numerical method was performed using the three-dimensional finite element analysis for various solder alloys such as Sn-37%Pb, Sn-3.5%Ag, Sn-3.5%Ag-0.7%Cu and Sn-3.5%Ag-3%In-0.5%Bi during a given thermal cycling. Strain values obtained by the result of mechanical fatigue tests for solder alloys, were used to predict the solder joint fatigue life using the Coffin-Manson equation. The numerical results showed that Sn-3.5%Ag with the 50-degree ball shape geometry had the longest thermal fatigue life in low cycle fatigue. A practical correlation for the prediction of the thermal fatigue life was also suggested by using the dimensionless variable γ. Additionally Sn-3.5Ag-0.75Cu and Sn-2.0Ag-0.5Cu-2.0Bi were applied to 6$\times$8$\mu$BGA obtained from the 63Sn-37Pb Solder. This 6$\times$8$\mu$BGA were tested at different aging conditions at 130$\^{C}$, 150$\^{C}$, 170$\^{C}$ for 300, 600 and 900 hours. Thickness of the intermetallic compound layer was measured thor each condition and the activation energy thor their growth was computed. The fracture surfaces were analyzed using SEM (Scanning Electron Microscope) with EDS ( Energy Dispersive Spectroscopy).

Structural Layout Design for Concrete Structures Based on the Repeated Control Method by Using Micro Lattice Truss Model (마이크로 격자트러스모델을 이용한 반복강성제어법에 의한 콘크리트 구조형태의 최적화)

  • Choi, Ik-Chang;Ario, Ichiro
    • Journal of the Korea Concrete Institute
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    • v.20 no.6
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    • pp.705-712
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    • 2008
  • This study carried out simulation for structural layout design for concrete structures by using the models of the ground structure method. The micro lattice truss is modeled as assemblage of a number of unit cells. The progress of analysis repeat to undergo finite element analysis to feed-back results of stress to the stiffness of each member. Through the repeated this analysis, truss model is represented to form the topological materials and the structural shape with the use of the local stress condition without mathematical optimum tools. It is successful to analyse the shape-layout problem as numerical samples on the lattice truss model.

Impact analysis of composite plate by multiscale modeling (멀티스케일 모델링에 의한 복합재료 평판의 충격해석)

  • Ji Kuk Hyun;Paik Seung Hoon;Kim Seung Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.04a
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    • pp.67-70
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    • 2004
  • An investigation was performed to study the impact damage of the laminated composite plates caused by a low- velocity foreign object with multi-scale modeling based on the concepts of Direct Numerical Simulation (DNS)[4]. In the micro-scale part, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. A micro-scalemodel was developed for predicting the initiation of the damage and the extent of the final damage as a function of material properties, laminate configuration and the impactor's mass, etc. Anda macro-scale model was developed for description of global dynamic behavior. The connection betweenmicroscopic and macroscopic is implemented by the tied interface constraints of LS-DYNA contact card. A transient dynamic finite element analysis was adopted for calculating the contact force history and the stresses and strains inside the composites during impact resulting from a point-nose impactor. The low-velocity impact events such as contact force, deformation, etc. are simulated in the macroscopic sense and the impact damages, fiber-breakage, matrix cracking and delamination etc. are examined in the microscopic sense.

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Remote-controlled micro locking mechanism for plate-type nuclear fuel used in upflow research reactors

  • Jin Haeng Lee;Yeong-Garp Cho;Hyokwang Lee;Chang-Gyu Park;Jong-Myeong Oh;Yeon-Sik Yoo;Min-Gu Won;Hyung Huh
    • Nuclear Engineering and Technology
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    • v.55 no.12
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    • pp.4477-4490
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    • 2023
  • Fuel locking mechanisms (FLMs) are essential in upward-flow research reactors to prevent accidental fuel separation from the core during reactor operation. This study presents a novel design concept for a remotely controlled plate-type nuclear fuel locking mechanism. By employing electromagnetic field analysis, we optimized the design of the electromagnet for fuel unlocking, allowing the FLM to adapt to various research reactor core designs, minimizing installation space, and reducing maintenance efforts. Computational flow analysis quantified the drag acting on the fuel assembly caused by coolant upflow. Subsequently, we performed finite element analysis and evaluated the structural integrity of the FLM based on the ASME boiler and pressure vessel (B&PV) code, considering design loads such as dead weight and flow drag. Our findings confirm that the new FLM design provides sufficient margins to withstand the specified loads. We fabricated a prototype comprising the driving part, a simplified moving part, and a dummy fuel assembly. Through basic operational tests on the assembled components, we verified that the manufactured products meet the performance requirements. This remote-controlled micro locking mechanism holds promise in enhancing the safety and efficiency of plate-type nuclear fuel operation in upflow research reactors.

Influence of microthread design on marginal cortical bone strain developement: A finite element analysis (임플란트 경부 미세나사 디자인이 치밀골의 스트레인에 미치는 영향)

  • Chun, Seung-Geun;Cho, Jin-Hyun;Jo, Kwang-Heon
    • The Journal of Korean Academy of Prosthodontics
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    • v.48 no.3
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    • pp.215-223
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    • 2010
  • Purpose: The present study was aimed to evaluate the level of cortical bone strain during the placement of an implant. The primary concern was to investigate if the extent of overloading area near the marginal bone could be affected by microthread fabricated at the cervical 1/3 of an implant. Materials and methods: Three dimensional finite element analysis was used to simulate the insertion of 3 implants. Control model was $4.1{\times}10$ mm implant (Submerged model, Dentis Co,, Daegu, Korea) equipped with a main thread only. Type I was with main thread and microthread, and Type II had similar thread pattern but was of tapered body. A PC-based finite element software (DEFORM 3D ver 5, SFTC, Columbus, OH, USA) was used to calculate a total of 3,600 steps of analysis, which simulated the whole insertion. Results: Results showed that the strain field in the marginal bone within 1 mm of the implant wall was higher than 4,000 micro-strain in the control model. The size of bone overloading was 1-1.5 mm in Type I, and greater than 2 mm in Type II implants. Conclusion: These results indicate that the marginal bone may be at the risk of resorption on receiving the implant for all 3 implant models studied. Yet, the risk was greater for Type I and Type II implants, which had microthread at the cervical 1/3.

System Analysis and Design for Vibration-Based Power Generation using Piezoelectric Materials (압전 재료를 이용한 진동에너지 변환 전력발생 시스템 해석 및 설계)

  • Keum, Myoung-Hun;Kim, Kyung-Ho;Lee, Seung-Yep;Ko, Byoung-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.6
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    • pp.717-725
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    • 2004
  • A power generation systems are proposed to convert ambient mechanical vibration into electrical energy using cantilever-type piezoelectric materials. The vibration-based power device can be used for self-powered systems without batteries. This paper presents the theoretical analysis for the coupled equations of piezoelectric and structural motions and investigates the dynamic characteristics of the self-power system using transfer function method. The theoretical model is verified by the finite element analysis of the resonance frequency, the dynamic response of the structure and the sensor sensibility. Experimental results measured using a prototype system agree with the theoretical predictions. The system is shown to produce 34.5 ㎼ in average. Finally, we perform the optimal design for system variables to maximize output power.

Structural Analysis of a Cavitary Region Created by Femtosecond Laser Process

  • Fujii, Takaaki;Goya, Kenji;Watanabe, Kazuhiro
    • Journal of Power System Engineering
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    • v.19 no.3
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    • pp.5-10
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    • 2015
  • Femtosecond laser machining has been applied for creating a sensor function in silica glass optical fibers. Femtosecond laser pulses make it possible to fabricate micro structures in processed regions of a very thin glass fiber line because femtosecond laser pulses can extremely minimize thermal effects. With the laser machining to optical fiber using a single shot of 210-fs laser at a wavelength of 800 nm, it was observed that a processed region surrounded a thin layer which seemed to be a hollow cavity monitored by scanning electron microscopy (SEM). This study aims at a theoretical investigation for the processed region by using a numerical analysis in order to embed sensing function to optical fibers. Numerical methods based finite element method (FEM) has been used for an optical waveguide modeling. This report suggests two types modeling and describes a comparative study on optical losses obtained by the experiment and the numerical analysis.

System Analysis and Design for a Vibration Converted Power Generator using Piezo Materials (압전 재료를 이용한 진동에너지 변환 전력발생 시스템 해석 및 설계)

  • 금명훈;이승엽;고병식;김경호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.1059-1066
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    • 2003
  • A power generation system are proposed to convert ambient mechanical vibration into electrical energy using cantilever-type piezoelectric materials. The vibration-based power device can be used for self-powered systems without batteries. This paper presents the theoretical analysis for the coupled equations of piezoelectric and structural motions and investigates the dynamic characteristics of the self-power system using transfer function method. The theoretical model is verified by the finite element analysis of the resonance frequency, the dynamic response of the structure and the sensor sensibility. Experimental results measured using a prototype system agrees with the theoretical predictions. The system is shown to produce 2.53㎼ in average. Finally, we perform the optimal design for system variables to maximize output power.

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Optimum Design of Micro-Cantilever Sensor for measuring CO gas (CO 가스측정을 위한 마이크로 캔틸레버 센서의 최적화 설계)

  • Son, H.J.;Na, D.S.;Peak, K.K.;Park, B.H.;Kwon, K.H.;Nahm, S.;Ju, B.K.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.412-413
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    • 2005
  • This paper describes resonant frequency of the structural behavior of micro-cantilever beam simulated by FEM (Finite Element Method). The resonant characteristics and the sensitivity of cantilever-shaped SOI resonant were measured for the application of chemical sensor. The resonant frequency of the fabricated micro-cantilever system was found to be 5.59kHz when the size of cantilever is $500{\mu}m$ long, $100{\mu}m$ wide and $1{\mu}m$ thick. Generation of resonant frequency measured by Modal Analysis is resulted in length of cantilever. The length was found to be a dominant factor for the selection of required resonant frequency range. On the other side, the width had influenced very little on either the magnitude of resonant frequency or the sensitivity.

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