• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.122-129
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• 2012

This study investigates structural and vibration analyses according to the thickness of bicycle frame tube. The model of bicycle frame has the dimension as length of 862mm, width of 100mm and hight of 402.5mm. There are 3 kinds of models with tubes of top, down and seat at bicycle frame as thicknesses of 10, 15 and 20mm. The maximum displacement and stress occur at the center part of seat stay and at the installation part of rear wheel respectively. Maximum displacements become 0.031936, 0.029159 and 0.027984mm in cases of thicknesses of 10, 15 and 20mm respectively. In case of thickness of 20mm among 3 cases, maximum displacement becomes lowest. But maximum stresses become 10.019, 8.5492 and 9.2511MPa in cases of thicknesses of 10, 15 and 20mm respectively. In case of thickness of 15mm among 3 cases, maximum stress becomes lowest. There is no resonance at practical driving conditions and natural frequency remains almost unchanged along the change of thickness. In case of the displacement due to vibration mode, the displacement difference at thickness between 15mm and 20mm becomes 1/2 times than that between 10mm and 15mm. Design at bicycle frame tube becomes most economical and durable effectively in case of thickness of 15mm among 3 cases.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.189-198
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• 2017

Purpose: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. Materials and Methods: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. Results: Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. Conclusion: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.280-283
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• 2011

This study investigates the durability of car body and the safety of passenger inside car body in the case of the impact contact at passenger and car body. In case of front impact contact, maximum von Mises equivalent stress and principal stress become 3240.7MPa and 1634MPa respectively at the rear part of car body and the neck of dummy. And maximum total deformation occurred with 14.145mm at the hand of dummy. In case of side impact contact, maximum von Mises equivalent stress and principal stress become 7687.9MPa and 1690.7MPa respectively at the front part of car body and the lap of dummy. And maximum total deformation occurred with 16.414 mm at the foot of dummy. In case of rear impact contact, maximum von Mises equivalent stress and principal stress become 2366.6MPa and 1447MPa respectively at the front part of car body and the neck of dummy. And maximum total deformation occurred with 7.548mm at the rear part of car body. As the maximum von-Mises stress at side impact is shown with more than 700MPa as over two times at front or rear impact the danger of car body is increased. The great possibility of damage is shown at neck and hand of dummy with more than total displacement of 10mm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1551-1561
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• 2012

Boat or yacht hulls are mainly built using FRP composite materials. FRP boat hull manufacturing has been restricted since 2000 under international regulations on ocean environment safety. FRP composite materials cannot be recycled and require more than 100 years to biodegrade. Therefore, alternatives to FRP have been proposed by many boat builders. Steel, aluminum, and FRP are commonly used as boat hull materials. Their design specifications are proposed as Korean register of shipping. However, the design specifications for inexpensive materials for a small boat have not yet been studied. Small shipbuilders manufacture and sell HDPE canoes or HDPE kayaks. In this study, a hull form was designed based on actual boats. The thickness of an HDPE boat hull was determined based on ISO 12215-5 structural design specifications.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.251-251
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• 2021

최근 기후변화로 인한 집중호우의 영향으로 홍수 시 댐으로의 유입량이 설계 당시보다 증가하여 댐의 안전성 확보가 필요하다(감사원, 2003). 이에 건설교통부(2003)는 기후변화와 댐 노후화에 대비하여 치수능력증대사업을 추진하여 댐의 홍수배제능력을 확보하였고, 환경부(2020)에서는 40년 이상 경과된 댐을 대상으로 스마트 안전관리체계 구축을 통한 선제적 보수보강, 성능개선 및 자산관리로 댐의 장수명화를 목적으로 댐의 국가안전대진단을 추진하고 있다. 이에 본 연구에서는 댐 시설(여수로)의 노후도 평가 시 활용 될 수 있는 여수로 표면손상 원인규명에 대하여 3차원 수치모형(FLOW-3D 및 COMSOL Multiphysics)을 통해 검토하고자 한다. 연구대상 댐은 𐩒𐩒댐으로 지형 및 여수로를 구축하였으며, 계획방류량(200년 빈도) 및 최대방류량(PMF) 조건에서 모의를 수행하였다. 수치모의 계산의 정확도 검토를 위하여 Baffle의 설치를 통하여 시간에 따른 유량의 변화를 설계 값과 비교하였고 오차가 1.0% 이내를 만족하는 것을 확인하였다. 여수로 표면손상의 다양한 원인 중 기존연구(USBR, 2019)를 통하여 공동침식(Cavitation Erosion) 및 수력잭킹(Hydraulic Jacking)에 초점을 두었으며 방류조건 별 공동지수(Cavitation Index)산정을 통하여 공동침식 위험 구간을 확인하였다. 이음부의 균열 및 공동으로 인한 표층부 콘크리트의 탈락현상을 가속화시키는 수력잭킹 검토를 위하여 국부모형을 구축하였고 음압력(Negative Pressure), 정체압력(Stagnation Pressure), 양압력(Uplift Pressure)의 분포를 확인하였다. 최종적으로 COMSOL Multiphysics를 통하여 압력분포에 따른 구조해석을 수행하여 폰 미세스(Von Mises) 등가응력 및 변위를 검토하여 콘크리트의 탈락가능성을 확인하였다. 본 연구는 여수로 공동부 및 균열부에서의 손상메커니즘을 확인할 수 있는 기초적인 연구이지만 향후에는 다양한 지형조건 및 흐름조건에서의 압력분포 분석 및 유체-구조물 상호작용(Fluid-Structure Interaction, FSI)모의를 수행한다면 구조물 노후도 및 잔존수명 평가에 필요한 손상한계함수 도출이 가능할 것으로 기대된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.2
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• pp.95-101
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• 2020

The wind turbine blades should be designed to possess a high stiffness and should be fabricated with a light and high strength material because they serve under extreme combination of lift and drag forces, converting kinetic energy of wind into shaft work. The goal of this study is to understand the basic knowledge required to curtail the process time consumed during the construction of small wind turbine blades using carbon fiber reinforced polymer (CFRP) prepeg composites. The configuration of turbine rotor was determined using the QBlade freeware program. The fluid dynamics module simulated the loads exerted by the wind of a specific speed, and the stress analysis module predicted the distributions of equivalent von Mises stress for representing the blade structures. It was suggested to modify the shape of test specimen from ASTM D638 to decrease the variance in measured tensile strengths. Then, a series of experiments were performed to confirm that the bladder compression molded CFRP prepreg can provide sufficient strength to small wind turbine blades and decrease the cure time simultaneously.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.43-50
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• 2021

A Leg Mating Unit (LMU) is a device utilized during the float-over installation of offshore structures that include hyperelastic pads and mating part. The hyperelastic pads absorb the loads, whereas the mating part works as guidance between topside and supporting structures during the mating sequence of float-over installation. In this study, the design optimization of an LMU for the float-over installation of floating-type offshore structures is conducted to enhance the performance and to satisfy the requirements defined by classification society regulations. The initial dimensions of the LMU are referred to the dimensions of those used in fixed-type float-over installation because only the location and the number of LMUs are known. The two-parameter Mooney-Rivlin model is adopted to describe the hyperelastic pads under given material parameters. Geometric variables, such as the thickness, height, and width of members, as well as configuration variables, such as the angle and number of members, are defined as design variables and are parameterized. A sampling-based design sensitivity analysis based on latin hypercube sampling method is performed to filter the important design variables. The design optimization problem is formulated to minimize the total mass of the LMU under maximum von Mises stress and reaction force constraints.