• 한국소음진동공학회논문집
• /
• 제15권1호
• /
• pp.96-104
• /
• 2005

The coupled vibration characteristics for the fluid-structure interaction systems are investigated through the finite element method. The present paper is focused on vibration characteristics of the cylindrical fluid-storage tank with a baffle. The tank is partially filled with an inviscid and irrotational fluid having a free surface. A baffle is assumed here to have the shape of a thin annular plate and a conical shell, attached to the cylindrical tank and positioned below the fluid surface. The liquid domain is limited by a rigid flat bottom. As the effect of free surface waves is taken into account in the analysis, the bulging and sloshing modes are studied. To demonstrate the validity of present results, they are compared with the published ones. The effect of positions and inner-to-outer radius ratio of annular baffle and setting angles of conical baffle on coupled vibration characteristics is investigated.

• Structural Engineering and Mechanics
• /
• 제91권3호
• /
• pp.291-300
• /
• 2024

This paper predicts the combined resonance behavior of the truncated conical shells (TCSs) under transverse and parametric coupled excitation. The motion governing equation is formulated in the framework of high-order shear deformation theory, von Kármán theory and Hamilton principle. The displacements and boundary conditions are characterized by a set of displacement shape functions with double Fourier series. Subsequently, the method of varying amplitude (MVA) is utilized to derive the approximate analytical solution of system response of TCSs. A comparative analysis is conducted to verify the accuracy of the current computational method. Additionally, the interaction mechanism of combined resonance, parametric resonance and primary resonance is examined. And the effect of damping coefficient, the external excitation, initial phase, axial motion speed, temperature variation, humidity variation, material properties and semi-vortex angle on the vibration mechanism are analyzed.

• 소성∙가공
• /
• 제27권5호
• /
• pp.276-280
• /
• 2018

This paper has developed a forging process for conical shells for making aluminum cylindrical large shells. An incremental forging process was applied to reduce forging loads and die cost. The preform is designed based on the crosssectional area of the final forged shape. Inner diameter of the preform for mandrel forging is constant, and outer diameter is conical so that it matches the cross-sectional area of the product. However, simulation confirmed that the larger diameter is smaller than predicted and the length is larger than predicted because in the initial stage of forging, the large diameter portion first comes into contact with the anvil at the initial stage of forging and stretches in longitudinal direction. So, it has developed a rule to design the preform considering 3-D deformation instead of plane strain deformation at the beginning stage of mandrel forging. The developed mandrel forging process can be applied to more similar products and economic benefits may be obtained.

• 한국의학물리학회지:의학물리
• /
• 제27권4호
• /
• pp.236-240
• /
• 2016

The purpose of this study is to propose a novel high sensitivity neuro-PET design. The improvement of sensitivity in neuro-PET is important because it can reduce scan time and/or radiation dose. In this study, we proposed a novel PET detector design that combined conical shape detector with cylindrical one to obtain high sensitivity. The sensitivity as a function of the oblique angle and the ratio of the conical to cylindrical portion was estimated to optimize the design of brain PET using Monte Carlo simulation tool, GATE. An axial sensitivity and misplacement rate by penetration of ${\gamma}$ rays were also estimated to evaluate the performance of the proposed PET. The sensitivity was improved by 36% at the center of axial FOV. This value was similar to the calculated value. The misplacement rate of conical shaped PET was about 5% higher than the conventional PET. The results of this study demonstrated the conical detector proposed in this study could provide subsequent improvement in sensitivity which could allow to design high sensitivity PET for brain imaging.

• Fisheries and Aquatic Sciences
• /
• 제13권2호
• /
• pp.182-189
• /
• 2010

An active stimulating device (ASD) using a rope apparatus may operated by the flow of turbulence inside a cod end, generating variable stimuli in addition to flow-related effects to minimize the by-catch of juvenile fishes. Preliminary testing involved a hydrodynamic effect inside the cod end with a rotating rope kite or conical rope array to generate variable stimuli (visual stimuli, water flow, or physical contact with fish) to change fish position. The experimental rope kite offered more choice in rotating period and range of sweeping action; adjusting the towing line or flow velocity helped to drive fish toward the net panel and encouraged escape. The conical shape of the rope array in the cod end helped to clear a path for fish by disturbing the rigging and providing more contrast between objects, preventing an optomotor response. This enabled more black porgy to be herded toward the net at an early stage of towing. Therefore, either a conical rope array or a rotating rope kite can be used as an effective ASD to prevent juvenile by-catch.

• 한국강구조학회 논문집
• /
• 제12권4호통권47호
• /
• pp.417-428
• /
• 2000

최근 복합재료는 토목뿐만 아니라 건축, 항공, 선박산업분야에서 널리 사용되고 있다. 두 가지 이상의 다른 재료들로 구성된 복합재료는 역학적 특성에서 단일재료보다 매우 유리한 장점을 가지고 있다. 쉘 구조물은 직선구조물과 비교해 볼 때 곡선형상 때문에 하중에 효과적으로 저항하는 이점이 있다. 이러한 쉘 구조물에 복합재료를 사용함으로서 보다 높은 강성과 낮은 중량을 가진 경제적인 쉘 구조물을 설계할 수 있다. 본 논문의 목적은 전단변형효과를 고려한 원뿔형 쉘을 해석하여 복합재료의 이점을 규명하고 자유경계의 효과를 고찰하는데 있다. 본 논문은 원뿔형 쉘의 미분방정식을 해결하기 위해서 유한 차분법을 사용하였다.

• 한국강구조학회 논문집
• /
• 제14권4호
• /
• pp.519-527
• /
• 2002

쉘 구조물은 지붕 구조물, 굴뚝 구조물, 압력구조물, 선박구조물, 항공구조물 등에 널리 사용되는 구조물이다. 본 논문은 전단변형 효과를 고려한 비등방성 복합성층 원뿔형 쉘의 자유진동에 관하여 연구하였다. 복합재료는 2개 또는 이상의 재료들로 구성되어 구조적인 효율성을 증진시키도록 구성된 재료이다. 이러한 복합재료로 구성된 구조물의 거동은 매우 복잡하기 때문에 해석해를 구하기가 거의 불가능하다. 따라서 본 연구에서는 이러한 복합재료로 구성된 원뿔형 쉘의 자유진동을 해결하는데 유한차분법을 사용하였다. 중심각, 정점각 및 다른 기하학적 파라미터의 진동에 대한 효과를 연구하였고, 진동모드 형상을 예시함으로서 진동모드에 관한 물리적 및 공학적인 이해를 증진시키고자 하였다.

• 대한기계학회논문집A
• /
• 제21권8호
• /
• pp.1195-1208
• /
• 1997

Bellows is a component in piping systems which absorbs mechanical deformation with flexibility. Its geometry is an axial symmetric shell which consists of two toroidal shells and one annular plate or conical shell. In order to analyze bellows, this study presents the finite element analysis using a conical frustum shell element. A finite element analysis is developed to analyze various bellows. The validity of the developed program is verified by the experimental results for axial and lateral stiffness. The formula for calculating the natural frequency of bellows is made by the simple beam theory. The formula for fatigue life is also derived by experiments. The shape optimal design problem is formulated using multiple objective optimization. The multiple objective functions are transformed to a scalar function by weighting factors. The stiffness, strength and specified stiffness are considered as the multiple objective function. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, and the manufacturing conditions. Geometric parameters of bellows are the design variables. The recursive quadratic programming algorithm is selected to solve the problem. The results are compared to existing bellows, and the characteristics of bellows is investigated through optimal design process. The optimized shape of bellows is expected to give quite a good guideline to practical design.

• Composites Research
• /
• 제29권6호
• /
• pp.358-362
• /
• 2016

원추형 복합재 튜브는 우주 항공, 비행체, 잠수함 등 큰 구조물뿐만 아니라 자전거 프레임, 낚시대, 골프채 등 레저용품에도 적용이 되면서 정적-동적 거동에서의 기계적 물성 예측의 중요한 연구 분야로 대두되고 있다. 일반적으로 원추형 복합재 튜브의 기계적 물성 예측은 진동, 굽힘, 좌굴에 관하여 많은 연구가 진행되었지만, 복합재료의 섬유 배향 각이 일정하다고 가정하고 기계적 거동을 분석한 것이 대부분이기 때문에 섬유 배향 각이 원추형 복합재 튜브 구조물의 기계적 물성에 어떠한 영향을 미치는지에 대한 연구가 필요하다. 이에 본 연구에서는 섬유 배향 각을 고려한 원추형 복합재료 튜브의 정적 거동에 따른 기계적 물성을 예측하기 위해 수식을 도출하고, 자전거 프레임에 적용하기 위한 다양한 설계 파라메터의 영향을 고찰하였다.

• 한국정밀공학회지
• /
• 제33권11호
• /
• pp.911-918
• /
• 2016

A conical roll-shaping process was proposed for fabrication of a metallic spiral blade applied to a small-scale wind turbine system. A spiral blade has continuously different curvatures, with a range of 100 to 350 mm radius. To fabricate this complex shape, we developed a conical roll-shaping process having two main conical rollers for feeding a blank sheet, and two cylindrical side rollers for control of local bending. For clear understanding of the process parameters, numerical analyses were conducted using a commercial code, Pam-Stamp. This study optimized the effects of process parameters, such as gap and angle between the main rollers and side rollers, and also the movement of side rollers. In order to increase the forming efficiency, a central rotation point was also calculated by the analytical approach. This developed rolling process can thus be utilized in a sheet metal forming process for obtaining spirally curved sheet metal shapes.