• 한국정밀공학회지
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• 제18권12호
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• pp.145-151
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• 2001

The dimensional accuracy of the cold forged part is depended on the elastic characteristics of the die. To increase the stiffness of the prestressed die, the first stress ring of the tungsten carbide alloy (WC) is considered. For the design, Lame's equation is used. Diameter ratios and interferences have been determinated by maximum inner pressure without yielding of materials. The design of the prestressed die has been compared with the conventional one. For the comparison, the FE-analysis using ANSYS has been performed. The results indicate that the prestressed die with the high stiffness can be obtained by the using the high stiffness material as the first stress ring.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.377-380
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• 2000

The dimensional accuracy of the cold forged part is depended on the elastic characteristics of the die. To obtain the high stiffness of the prestressed die, the first stress ring of the tungsten carbide material is considered. For the design, Lam 's equation is used. The design of the prestressed die has been compared with the conventional that. For the comparison, the FE-analysis using ANSYS has been performed. The results indicate that the prestressed die with the high stiffness can be obtained by the using the high stiffness material as the first stress ring.

• 한국정밀공학회지
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• 제17권10호
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• pp.77-82
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• 2000

The design of the prestressed cold extrusion die with two stress rings has been performed in this study. The cold extrusion has been simulated by the rigid-plastic FEM. The stress analysis of die has been performed for both after shrink fitting and during extrusion by using the elastic FEM and the Lame's equation. According to the variation of interferences and diameter ratios, the maximum effective stress has been evaluated. As results, interferences and diameters were determined by the minimization of the maximum effective stress of die insert. The comparison of the maximum effective stress between the proposed design and the conventional design has been discussed. It was found that the maximum effective stress in the die insert is considerably affected by the stiffness of the first stress ring.

• Journal of Welding and Joining
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• 제18권4호
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• pp.28-37
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• 2000

In this paper the LNG vessel of the Moss type which is capable of lifting 15,261 tons is investigated in the view point of the pressure vessel preliminary design using the finite element method. The Pressure vessel design is based on the equivalent stress levels due to the internal pressure. The finite element model of the spherical pressure vessel is configured using 4 noded quadrilateral shell element. The finite element analysis program NASTRAN and ANSYS 5.5are implemented. The design is compared with the three kinds of the boundary condition : first, where the equator of the pressure vessel is fixed, and where the top and is fixed, and, the bottom end is fixed, respectively. A comparison is presented between the results obtained by the finite element model and by the prototype production model. Additionally just below position(case 1 & case 2) of equator ring was carried out by using ANSYS 5.5. The results show that the vessel design based on the stress is acceptable at the preliminary design.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.45-48
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• 2007

In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the midplane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

• 한국생산제조학회지
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• 제24권2호
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• pp.231-237
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• 2015

The pin-gear drive is a special form of fixed-axle gear mechanism. A large wheel with cylindrical pin teeth is called a pinwheel. As pinwheels are rounded, they have a simple structure, easy processing, low cost, and easy overhaul compared with general gears. They are also suitable for low-speed, heavy-duty mechanical transmission and for occasions with more dust, poor lubrication, etc. This paper introduces a novel slewing ring bearing with an external pinwheel gear set (e-PGS). First, we consider the exact cam pinion profile of the e-PGS with the introduction of a profile shift. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of the e-PGS can be lowered significantly by increasing the profile shift coefficient.

• 한국전산유체공학회지
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• 제12권4호
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• pp.85-89
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• 2007

In the present work, flow analysis has been performed for side channel type double stage ring blower by solving three-dimensional Reynolds-averaged Navier-Stokes equation. Shear stress transport model is used as turbulent closure. The commercial CFD code CFX 11.0 is used for the calculations. Each of two stage is calculated separately and the second stage inlet flow is same as the first stage outlet flow so that consecutive calculation is possible. Velocity and pressure fields have been analyzed at the mid-plane between blades. The numerical results are validated with experimental data for head coefficients at different flow coefficients.

• 한국생산제조학회지
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• 제21권1호
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• pp.95-101
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• 2012

An internal type roller ring gear(RRG) system composed of either a pin or a roller ring gear and its conjugated cam pinion can improve the gear endurance from that of a conventional gear system by reducing the sliding contact, while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection conditions obtained when the profile shift coefficient is introduced. Then, we investigated contact stresses and surface pitting life to fmd characteristics for surface fatigue by varying the shape design parameters. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• Composites Research
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• 제37권1호
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• pp.15-20
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• 2024

수소탱크의 잔류응력은 내구도와 직접적인 관련이 있기 때문에 안전을 위해 이를 줄이는 것이 매우 중요하다. Type II~IV 수소탱크는 섬유에 수지를 함침시켜 라이너에 감는 필라멘트 와인딩 공법으로 제작하게 된다. 필라멘트 와인딩에서 잔류응력은 경화조건, 섬유 인장 등에 영향을 받게 되는데, 본 연구에서는 탄소섬유 필라멘트 와인딩 공정을 이용한 Type III 수소탱크 제작 시 경화조건이 잔류응력에 미치는 영향을 분석하였다. 먼저 에폭시 수지의 경화거동을 시차주사열량계를 이용하여 분석하였다. 이를 통해 경화온도를 140℃로 설정하였다. 같은 경화시간 동안 140℃에 먼저 도달하는 2-stage 경화조건과, 보다 늦게 도달하는 4-stage 경화조건으로 각각 시편을 경화시켰다. 경화 후 복합재 부분의 잔류응력을 ring slitting 법으로 측정하였고, 이 실험값을 수치해석적인 값과 비교하였다. 그 결과, 경화조건 최적화에 따른 유의미한 잔류응력의 차이가 발생함을 확인하였다.

• Investigative Magnetic Resonance Imaging
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• 제18권1호
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• pp.7-16
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• 2014

목적: 심첨형 비후성 심근병증 환자에서 스트레스 부하 관류 자기공명영상을 통한 관류 결손의 빈도와 양상을 평가하고, 이를 좌심실 비대의 정도와 지연 조영 증강과 비교해 보고자 한다. 대상과 방법: 2008년 1월부터 2012년 12월까지 심초음파 및 심전도로 심첨형 비후성 심근병증을 진단받고, 스트레스 부하 관류, 영화 영상 및 지연 조영 증강 영상을 포함하는 심장 자기공명영상을 시행한 26명의 환자를 대상으로 하였다. 영화 영상에서 이완기 말에 416개 분절의 좌심실 벽 두께를 분석하였고 비후된 분절의 수와 연속하여 비후된 벽 분절의 수를 조사하였다. 또한 모든 환자에서 관류 결손과 지연 조영 증강의 유무를 평가하였다. 자기공명영상에서 관류 결손이 있을 경우, 산발형 혹은 고리형의 2가지 형태로 분류하였다. 단변량 분석을 통해 전체 관류 결손과 고리형 관류 결손에 대한 독립 변수를 산출하였다. 결과: 심첨형 비후성 심근병증의 76.9%(20명)에서 스트레스 부하 관류 자기공명영상시 관류 결손을 보였으며 이중 60% (12명)이 고리형 관류 결손을 보였다. 전체 관류 결손에 대한 독립 변수는 최대 좌심실 벽 두께와 비후된 분절의 수 였고 (p < 0.05), 고리형 관류 결손에 대한 독립 변수는 3개 이상의 연속한 비후된 분절의 수가 추가되었다. 그러나 지연 조영 증강은 관류결손과는 유의한 상관관계가 없었다. 결론: 심첨형 비후성 심근병증 환자의 4분의 3에서(75%) 관류 결손을 보였으며, 대부분이 고리형 관류 결손 형태를 보였다. 좌심실 벽의 비후 정도와 분포는 관류 결손의 형태와 관련이 있었지만 지연 조영 증강과는 유의한 상관성이 없었다. 따라서 심첨형 비후성 심근병증 환자군에서 관류 결손의 임상적 의미는 비심첨형 비후성 심근병증 환자군에서 보이는 관류결손과는 임상적 의의가 다를 것으로 보이며, 이에 대한 추후의 비교연구가 필요할 것으로 여겨진다.