• Structural Engineering and Mechanics
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• 제55권4호
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• pp.839-856
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• 2015

A multi-contact tooth meshing model for helical gear pairs considering bearing and shaft deformations is proposed. First, to easily incorporate into the system model, the complicated Harris' bearing force-displacement relationship is simplified applying a linear least square curve fit. Then, effects of shaft and bearing flexibilities on the helical gear meshing behavior are implemented through transformation matrices which contain the helical gear orientation and spatial displacement under loads. Finally, true contact lines between conjugated teeth are approximated applying a modified meshing equation that includes the influence of tooth flank displacement on the tooth contact induced by shaft and bearing displacements. Based on the model, the bearing's force-displacement relation is examined, and the effects of shaft deformation and external load on the multi-contact tooth mesh load distribution are also analyzed. The advantage of this work is, unlike previous works to search true contact lines through time-consuming iterative strategy, to determine true contact lines between conjugated teeth directly with presentation of deformations of bearings and shafts.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.720-723
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• 2004

Lever mechanisms are usually employed to enlarge output displacement in precision stages. In this study, theoretical analysis of a lever is presented including bending effect and relation between dimension parameters and an objective function. The objective function is chosen as multiplication of magnification ratio and forcedisplacement transmission. Through theoretical analysis, this study presents optimal values for the parameters and the analysis is verified by finite element method.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.481-492
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• 2022

Cycloidal ball planetary transmission (CBPT) has many applications as precision reducer, such as precision machinery and automation drive systems etc. The traditional analytical model of CBPT cannot accurately describe the change of the normal force of meshing points, and thus cannot describe the precise transmission process of meshing pairs. In the paper, a method for deriving the normal force equation is put forward by using the non-linear relationship between force and deformation in elastic mechanics. The two-point contact analytical models of all the meshing pairs are established to obtain the micro-displacement analytical model of CBPT under axial pre-tightening. Then, the non-real-time two-point contact analytical models of all the meshing pairs are further constructed to obtain the normal force expression to determine the critical compression coefficients. Experimental investigations are performed to verify the analytical model using the critical compression coefficients.

• 대한기계학회논문집
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• 제15권2호
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• pp.557-566
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• 1991

The metal V-belt behavior of a continuously variable transmission was investigated analytically and experimentally. Numerical results showed that nondimensional belt radial displacement increased in the radial inward direction for the driven pulley, while that of the driver pulley increased for the first 90 degrees of the active are and decreased with the increasing torque load. Experimental results for the belt radial displacement were in good agreement with the theoretical results. However, the absolute magnitude of the belt radial displacement was so small that the change in the belt displacement could not be measured in the experimental range except for the inlet region of the driven pulley, where the radial inward displacement was observed due to the effect of bending moment. The speed ratio-axial force relationship derived from the belt behavior analysis also showed god agreement with the experiment.

• 한국항만학회지
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• 제8권1호
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• pp.17-22
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• 1994

The wave interaction with flexible membrane such as PVC and fabrics is studied to prove its applicability to portable breakwaters. To obtain the wave exciting force acting on flexible membrane, eigen-function expansion method is employed. The effect of flexible is involved in body boundary condition in which x-directional displacement of membrane is obtained by solving the linear membrane equation. Displacement of membrane is assumed to be small compared to wavelength, therefore the tensile force of membrane remains constant. As the numerical examples, transmission and reflection coefficients according to the change of tensile forces are investigated. The hydrodynamic force on membrane, the dynamic tension in the mooring lines and the vertical displacement profile of membrane are also calculated. It is suggested that the flexible membrane can be used to engineering material for the future coastal/ocean applications.

• 대한토목학회논문집
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• 제33권5호
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• pp.1947-1955
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• 2013

본 논문의 목적은 얕은 기초 하중을 받는 입상체 내의 응력의 분포와 변위를 측정하는 광탄성 기법의 적용 방안을 제시하는 데 있다. 광탄성 측정기법은 입자 집합체의 힘 전달을 시각화하기 위해 사용 되었다. 실내 모형시험은 스틸 프레임으로 경계면을 만들고 폴리카보네이트 탄성중합체로 만들어진 이차원 원형 입자들을 적층하여 구성하였다. 광탄성 시트를 원형 입자에 코팅함으로써 힘 전달의 패턴을 밝은 빛의 줄무늬 형태로 확인할 수 있었고, 광탄성 측정 기법을 통해 접촉되어 있는 입자들에서의 주 응력차의 크기, 방향 또한 측정 할 수 있었다. 변위장은 디지털 이미지 해석 기법을 사용하여 측정 하였다. 하중 재하 초기 상태와 파괴 근처의 상태에서 서로 다른 접촉력의 분포를 정량적으로 분석하였다. 파괴 이전 단계에서 관측된 광탄성 패턴과 변위장은 접촉력 사슬의 좌굴 발생 이후 즉시 사라짐을 확인하였다.

• Steel and Composite Structures
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• 제21권5호
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• pp.1105-1119
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• 2016

In this study, it is presented that a new developed approach for equivalent area-distributed loading (EADL) induced from a single concentrated force. For the purpose, a full scale 3D steel formwork system was constructed in laboratory conditions. A developed load transmission platform was put on the formwork system and loaded step by step on the mass center. After each load increment, displacement was measured in several crictical points of the system. The developed platform which was put in to slab of formwork to equivalently distribute the load from a point to the whole slab was constituted using I profiles. A 3D finite element model of the formwork system was analyzed to compare numerical displacement results with experimental ones. In experimental tests,difference among the displacements obtained from reference numerical model (model applied EADL) and main numerical model (model applied single load using a load cell via load transmission platform) is about %13 in avarage. Difference among the displacements obtained from experimental results and main numerical model under 30 kN single load is about %11 in avarage. The results revealed that the displacements obtained experimentally and numerically are dramatically closed to each other. It is highlighted from the study that the developed approach is reliable and useful to get EDL.

• 한국음향학회지
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• 제32권4호
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• pp.361-368
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• 2013

진동하는 현의 성질을 나타내는 방법으로 반대 방향으로 진행하는 파가 현과 전송선로에 존재한다는 사실에 기초하여 현은 전송선로에 비유되어왔다. 이러한 비유에서 현의 강역(rigid end)과 변위는 각각 전송선로의 개방회로와 전류로 나타내어졌다. 그러나, 본 연구에서 강역과 변위는 각각 단락회로와 전압에 해당됨이 전송선로의 이론으로부터 밝혀졌고 이를 회로시뮬레이션으로 확인하였다. 이러한 발견에 기초하여 전송선로, 구분적 선형 전류원, 스위치들로 구성된 전송선로 기반 탄현 모델을 제안하였다. 임의로 선택된 지점에서의 전압과 전송선로 끝 극소 부분 양단에서 계산된 전압이 현의 성질을 지배하는 파동방정식의 차분형식(difference form)으로 구한 해당 지점에서 변위와 강역에서의 힘과 일치함을 보임으로서 제안한 모델이 정당함을 증명하였다. 또한, 제안된 모델의 현악기 및 관악기 모델링의 적용성을 제시하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제18권3호
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• pp.470-487
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• 1996

The purpose of this study was to investigate the dynamic response of the mandible to impact and provide insight into the fracture mechanism of the mandible, by 3-dimensional finite element method. The finite element model of the mandible was developed and calculated using NASTRAN/XL (MSC co. U.S.A.) and the linear dynamic transient analysis was performed according to the impulsive force direction, force type and impulse time to the mandible. At first, the load was applied on the mandibular symphysis, body, angle and subcondylar area in the horizontal mandibular plane and the computed stress-time histories at 14 locations of the mandible were obtained. Secondly, the impulsive force was directed to the symphyseal area with changing the force magnitude and impulse time, and calculated the node displacement at 8 locations of mandible. The conclusions from from this study were as follows. 1. The appearance of impulsive energy transmission was different to the direction of impulse to the mandible. 2. The impulsive stress and deformation were larger in lingual or medial side than buccal or lateral in the mandible. 3. The velocity, appearance of energy transmission and the fracture pattern in mandible were affected rather impulse time than force. 4. The horizontal impact to the one side of mandible did not have effect on the stress and displacement of contralateral mandible. From the above results, fracture pattern in symphysis can be showed as simple or comminuted, multiple or associated in body and angle and solitary in subcondyle area.

• 대한조선학회논문집
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• 제49권4호
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• pp.287-295
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• 2012

Hydrodynamic performance of a movable submerged breakwater was analyzed using energy dissipation model. Based on two-dimensional boundary element method the equation of motion including a viscous dissipation term proportional to velocity squared was solved by Newton-Raphson method. Energy dissipation coefficients as well as reflection and transmission coefficients of a submerged flat plate were calculated with various plate lengths and thickness. Both real and imaginary components of body displacement and forces were used to solve the motion of breakwater accurately. The effect of the magnitude of dissipation coefficient on the body displacement was evaluated. The results from the potential theory with no dissipation term were found to be an overestimate in resonance frequency.