• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.923-926
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• 2007

In this paper, the vibration of a rotating shaft with a thin rigid disk is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. A spectral element model is developed by using the variation method for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element. The result of vibration analysis by finite element method is compared to the result of this research.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.826-830
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• 2008

In this paper, the vibration of a rotating shaft with a thin rigid disk on bearing supports is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. And flexible supports are used to analyse the bearings. A spectral element model is developed for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element. The result of vibration analysis by finite element method is compared to the result of this research.

• 대한기계학회논문집A
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• 제33권3호
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• pp.231-236
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• 2009

Recently, The Hydroforming technology has recognized general technique in manufacture industry. Especially automotive industry, It has applied to increase strength, and decrease weight, cost and part number. The rigid axle suspension type is widely used for truck and bus in commercial vehicles due to simplicity. To develop the hydroforming rigid axle, it is necessary to estimate of the characteristics of front suspension from the design process. In this study, the characteristics estimation of the hydroforming rigid axle is preformed using Finite Element Analysis and apply to shape optimization.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.503-515
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• 2022

The multi-rigid-body matrix method (MRBMM) is a generalized modeling method for obtaining the displacements, forces, and dynamic characteristics of a compliant mechanism without performing inner-force analysis. The method discretizes a compliant mechanism of any type into flexure hinges and rigid bodies by implementing a multi-body mass-spring model using coordinate transformations in a matrix form. However, in this method, the deformations of bodies that are assumed to be rigid are inherently omitted. Consequently, it may yield erroneous results in certain mechanisms. In this paper, we present a multi-compliant-body matrix-method (MCBMM) that considers a rigid body as a compliant element, while retaining the generalized framework of the MRBMM. In the MCBMM, a rigid body in the MRBMM is segmented into a certain number of body nodes and flexure hinges. The proposed method was verified using two examples: the first (an XY positioning stage) demonstrated that the MCBMM outperforms the MRBMM in estimating the static deformation and dynamic mode. In the second example (a bridge-type displacement amplification mechanism), the MCBMM estimated the displacement amplification ratio more accurately than several previously proposed modeling methods.

• 한국기계가공학회지
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• 제17권3호
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• pp.22-27
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• 2018

One problem of the Discrete Element Method is the assumption of a spherical particle shape, which reduces the computing time but significantly limits the application of the DEM to analysis. This limitation can be overcome by a recently developed rigid-rod model. However, the rigid-rod model has an essential problem related with friction: it always contains friction error because of the bumpy surface. To overcome this issue, we suggest a superposed rigid-rod model in this paper. The superposed rigid-rod model is notably consistent with the theoretical value in terms of the velocity and angular velocity after the collision. The estimated error is negligible(less than 2%). Then, the developed model is applied to hopper discharging. The developed model shows no problem in the discharging flow from the hopper.

• 한국자동차공학회논문집
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• 제4권5호
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• pp.16-25
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• 1996

In the present work a rigid-plastic finite element formulation using dynamic explicit time integration scheme is proposed for numerical analysis of auto-body panel stamping processes. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. A damping scheme is proposed in order to achieve a stable solution procedure in dynamic sheet forming problems. In order to improve the drawbacks of the conventional membrane elements, BEAM(abbreviated from Bending Energy Augmented Membrane) elements are employed. Rotational damping and spring about the drilling direction are introduced to prevent a zero energy mode. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and the direct trial-and-error method. Computations are carried out for analysis of complicated auto-body panel stamping processes such as forming of an oilpan, a fuel tank and a front fender. The numerical results of explicit analysis are compared with the implicit results with good agreements and it is shown that the explicit scheme requires much shorter computational time, especially when the problem becomes more complicated. It is thus shown that the proposed dynamic explicit rigid-plastic finite element method enables an effective computation for complicated autobody panel stamping processes.

• 한국정밀공학회지
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• 제17권4호
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• pp.226-232
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• 2000

This paper develops a finite element model for studying the crashworthiness analysis of a mid-size truck. A simulation for a truck frontal crash to a rigid barrier using the model is performed with PAM-CRASH installed in super computer SP2. Full vehicle model is composed of 86467 shell elements, 165 beam elements and 98 bar elements, and 86769 nodes. The model uses four material model such as elastic, elastic-plastic(steel), rigid and elastic-plastic(rubber) material model which are in PAM-CRASH. Frame and suspension system are modeled with 28774 shell elements and 31412 nodes. Cab is modeled with 34680 shell elements and 57 beam elements, and 36254 nodes. Bumper is modeled with 2262 shell elements, and 2508 nodes. Axle, steering shaft, etc are modeled using beam or bar elements. Mounting parts are modeled using rigid bodies. Bodies are interconnected using nodal constrains or joint options. To verify the developed model, frontal crash test with 30mph velocity to a rigid barrier is carried out. In the crash test, vehicle pulse at lower part of b-pillar is measured, and deformed shapes of frame and driver seat area are photographed. Those measured vehicle pulse and photographed pictures are compared those from the simulation to verify the developed finite element model.

• 한국강구조학회 논문집
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• 제11권3호통권40호
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• pp.271-279
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• 1999

보와 기둥과의 반강접에 관한 최근 연구로서 기둥 면과 T-stub 플랜지 사이에 격리재를 설치하는 개량된 T-stub 요소를 개발하고 있다. 개량된 T-stub에 대한 비탄성 해석을 수행하였으며, 그 결과를 실험값과 비교 분석하였다. 비탄성 해석 방법은 기둥 면과 격리재 사이에 간격요소(gap element)를 적용하고, 고력볼트에 초기 응력을 부여하여 실험값과 잘 일치하는 결과를 보인다. 실무에서의 설계와 해석에 적용할 수 있는 약산식으로서 T-stub의 초기 강성도와 압축하중에 의한 소성내력에 관한 설계식을 제시한다.

• Structural Engineering and Mechanics
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• 제21권6호
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• pp.677-698
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• 2005

In engineering practice, tubular connections are usually assumed pinned or rigid. Recent research showed that tubular joints may exhibit non-rigid behavior under axial or bending loads. This paper is concerned with establishing a new classification for tubular joints and investigating the effect of joint rigidity on the global behavior of CHS (Circular Hollow Section) lattice girders. Parametric formulae for predicting tubular joint rigidities are proposed, which are based on the finite element analyses through systematic variation of the main geometric parameters. Comparison with test results proves the reliability of these formulae. By considering the deformation patterns of respective parts of Vierendeel lattice girders, the boundary between rigid and semirigid tubular connections is built in terms of joint bending rigidity. In order to include characteristics of joint rigidity in the global structural analysis, a type of semirigid element which can effectively reflect the interaction of two braces in K joints is introduced and validated. The numerical example of a Warren lattice girder with different joint models shows the great effect of tubular joint rigidities on the internal forces, deformation and secondary stresses.

• 대한기계학회논문집
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• 제13권3호
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• pp.317-322
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• 1989

본 연구에서는 Liu의 매트릭스를 강소성 유한요소법에 도입하여 통상의 소성가공 공정중에 있는 피가공물의 3차원 변형을 실용적인 수준에서 해석 가능케 하는 강소성 유한요소법을 도입하여 통상의 소성가공 공정중에 있는 피가공물의 3차원 변형을 실용적인 수준에서 해석 가능케 하는 강소성 유한요소법을 제안하고 실례를 통하여 제안한수법에 의하여 얻어진 해의 안정성과 계산효율을 검토한다.