• Composites Research
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• 제34권1호
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• pp.30-34
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• 2021

This paper present a three-dimensional unit cell finite element analysis to predict the pull-out behavior of a single stitch in a composite laminate. The stitching process used for this study correspond to the I-fiber stitching method that has been studied by the Composite Structures Lab (CSL) as a new through-thickness reinforced method. A total of six cases were analyzed, which were divided in two groups by the stitching yarn used, 6k and 12k. Each group of cases have three different thickness according to the amount of plies; 16 plies, 32 plies and 64 plies. The finite element analysis used the cohesive zone method to characterize the single stitch reinforcement in the interface. Due to the complexity of the load vs displacement curves taken from the experimental results, a bilinear and trilinear bridging laws were implemented in the models. The cohesive parameters used for each case showed a good agreement with the experimental data and can be used for future studies.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.248-251
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• 2000

The fabrication and characteristics of HTS race-track type field coil for generators was carried out. Field coils are composed of 3 pancake coils wound by 37-filamental Bi-2223/Ag-alloy tapes. The winding machine is horizontal type. The critical currents (I$_c$) of the superconducting tapes were measured with variation of bending strain and external magnetic fields. I$_c$ of both whole field coils and 3 pancake coils were measured as a function of temperature. At 77K under the self-field, I$_c$ of whole field coils was 12A, while in the case of middle pancake coil, I$_c$ was 15A. The distribution of magnetic field B was obtained, using 3-D FEM. Our simulation showed that maximums of B${\bot}$A in x-y plane were locally distributed in both the upper and the lower coils. In addition, the fabrication processes and the characteristics of field coil are described.

• Tribology and Lubricants
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• 제23권6호
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• pp.283-287
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• 2007

Permanent-magnet (PM) passive bearings use the repulsive forces between the rotor and the stator magnets for the bearing function. It is desirable that the stiffness of the bearing is maximized with the given volume of the magnet. The stiffness is affected by the magnet strength, the number of layers, and the magnetization patterns. Previously, finite-element method (FEM) has been used to maximize the stiffness of the bearing. In this paper, we used the equivalent current sheet method to calculate the stiffness. The validity of this approach is checked against FEM results. The optimized bearing is applied to a micro flywheel energy storage system.

• 한국지반공학회논문집
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• 제17권6호
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• pp.5-14
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• 2001

본 연구에서는 사면안정 확보를 위해 설치된 억지말뚝과 보강사면의 안전율을 산정할 수 있는 간편설계 법을 제안하였다. 억지말뚝-지반간 상호작용은 하중전이법으로, 사면의 안전율은 Bishop의 간편법을 이용하여 산정하였다. 말뚝 간격에 따른 군말뚝 효과를 고려하기 위해 실내모형실험 및 유한요소해석을 수행하였으며 이 결과를 토대로 군말뚝 상호작용계수를 제안하였다. 제안된 군말뚝 상호작용계수는 말뚝중심간격이 좁아질수록 감소하였으며, 두부조건이 자유단인 경우가 다른 구속조건에 비해 큰 폭으로 감소하였다. 개발된 억지말뚝의 설계기법은 본 연구에서 수행한 원심모형실험, 현장시험 및 기존 유한요소해석결과와 비교.분석하였다. 본 해석프로그램은 3차원 유한요소해석에 비해 쉽고 간단하면서도 말뚝-지반간 상호작용에 의해 매우 복잡한 거동을 나타내는 억지말뚝을 비교적 적절히 설계 할 수 있음을 알 수 있었다.

• 대한치과기공학회지
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• 제30권2호
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• pp.79-86
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• 2008

The purpose of this study was to investigate the effect retention element formed by metal surface treatment method on the bond strength of indirect composite resin and metal. The metal specimens were cast from Ni-Cr alloy($Rexillium^{(R)}$ III). They were divided into 5 groups by applied retention element: $50{\mu}m$ aluminium oxide sandblasting group, $250{\mu}m$ aluminium oxide sandblasting group, 0.2mm retention crystal group, 10% $H_{2}SO_{4}$ solution etching group, $110{\mu}m$ $Rocatec^{TM}$ Plus system group. Total 50 metal specimens were veneered with Sinfony indirect composite resin system. Specimens were tested for shear bond strength on an Instron universal testing machine and fracture mode of fractured specimens were analyzed by SEM and EDS. 1. 0.2 mm retention crystals were most effective in improving the resin-metal shear bond strength (p<0.05). 2. Sandblasting by $250{\mu}m$ aluminium oxide were more effective than sandblasting by $50{\mu}m$ aluminium oxide in improving the resin-metal shear bond strength(p<0.05). 3. Fracture mode of resin-metal fractured surface were cohesive failure mode in 0.2mm retention crystal, mixed failure mode in sandblasted specimens, etched specimens and the specimens sandblasted with $110{\mu}m$ $Rocatec^{TM}$ Plus system.

• 대한기계학회논문집
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• 제8권3호
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• pp.201-209
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• 1984

본 연구는 Kim과 Chiu가 사용한 연속체 관점에서 유도된 액체-기체상의 2상유 동모델(Two Phase Flow:TPF)을 이용하여 초기 집단연소수(group combustion number)의 크기, 즉 액적들의 초기 분포상태에 따른 연소상태를 예측 분류한다. 또한 이때 예 측된 대표적인 연소상태에서 형성되는 화염의 성질을 비교 검토한다.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.492-500
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• 2002

This paper presents a study of the effect of varying the roll gap of oval pass in round-oval-round pass sequence on the interracial slip of workpiece, entrance and exit velocities, stresses and roll load that the workpiece experiences during rolling, by applying analytical method, finite element simulation and verification through hot bar rolling tests. The results have shown that the roll gap variation of oval pass affects the interfacial slip of workpiece along the groove contact and the specific roll pressure. The optimum conditions in terms of minimum interfacial slip and minimum specific roll pressure, which might influence the maximum groove life, is obtained when the subsequent round pass is completely filled.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.943-948
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• 2019

In this study, investigation of spent fuel was performed using six group delayed neutron parameters. Three used fuels (F1, F2, and F11) which are burnt over the years in the core of Missouri University of Science and Technology Reactor (MSTR), were investigated. F16 fresh fuel was used as plutonium free fuel element and compared with irradiated used fuels to develop burnup and Pu discrimination method. The fast fission factor of the MSTR was calculated to be 1.071 which was used for burnup calculations. Burnup values of F2 and F11 fuel elements were estimated to be 1.98 g and 2.7 g, respectively. $^{239}Pu$ conversion was calculated to be 0.36 g and 0.50 g for F2 and F11 elements, respectively.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권6호
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• pp.705-719
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• 2017

Progressive Collapse Method (PCM) has been broadly applied to predict moment-carrying capacity of a hull girder, however accuracy of PCM has not been much studied. Accuracy of PCM is known to be dependent on how Load-Shortening and -Elongation (LSE) curve of a structural units are well predicted. This paper presents a new procedure to determine LSE datum based on box girder Finite Element Analyses (FEAs) instead of using finite element model of stiffened panels. To verify reliability of FEA results, the simple box girder collapse test results are compared with FEA results of same box girders. It reveals one frame-based box girder model is sufficiently accurate in terms of ultimate strengths of the box girders. After extracting LSE data from the box girders, PCM-based moment-carrying capacities are compared with those from FEAs of the box girders. PCM results are found to be equivalent to FEAs in terms of moment-carrying capacity if accurate LSE data are secured. The new procedure is applied to well-known 1/3 scaled frigate full section. Very excellent moment-carrying capacity of frigate hull section is obtained from PCM with LSE data from box girder FEAs.

• 한국기계가공학회지
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• 제19권12호
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• pp.34-41
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• 2020

Ready-mixed concrete is unconsolidated concrete typically transported to construction sites by using mixer trucks. A proper rotation of concrete is necessary to prevent its solidification in mixer trucks during transport: in accordance with the manufacturing method and quality inspection prescribed in KSF4009, this movement is maintained after the manufacturing of concrete in professional production plants and the addition of water, solid materials, and admixtures. Unfortunately, mixer truck parts wear out over long periods of time. In order to improve the wear resistance of the main part of mixer trucks, we used a steel plate with good wear resistance or partially added a reinforcement plate. In this study, we first tested the properties of concrete (as required for the DEM), and then carried out mixing and discharge simulations to define the actual operating conditions of mixer trucks. For each condition, we calculated the amount and location of wear. The reliability of our results was finally verified by comparing them with the measurement values. Overall, this study provided basic data for an optimal design of mixer trucks: one that would reduce the vehicles' weight and production costs.