• 동력기계공학회지
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• 제21권6호
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• pp.40-45
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• 2017

The objective of this study is the finite element-transfer stiffness coefficient method, which is the combination of the modeling technique of finite element method and the transfer technique of transfer stiffness coefficient method, is applied in the static analyses of two dimensional curved beam structures. To confirm the effectiveness of the applied method, two computational models are selected and analyzed by using finite element method, finite element-transfer stiffness coefficient method and exact solution. The computational results of the static analyses for two computational models using finite element-transfer stiffness coefficient method are equal to those using finite element method. When the element partition number of curved beam structure is increased, the computational results of the static analyses using both methods approach the exact solution. We confirmed that the finite element-transfer stiffness coefficient method is superior to finite element method when the number of the curved beam elements is increased from the viewpoints of the computational speed and the utility of computer memory.

• 한국철도학회논문집
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• 제18권1호
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• pp.33-42
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• 2015

궤도 안전을 위한 핵심 용품인 레일체결장치의 구성품 중 레일패드 또는 베이스플레이트 패드의 정적 수직강성은 궤도 전체의 강성 결정 시 중요 인자이며, 패드 제품의 제조과정에서 품질관리 기준이 된다. 패드의 정적 수직강성 확인은 시험을 통해 가능하며, 시험방법으로는 철도분야에 널리 사용되고 있는 EN 13146-9 및 이를 부합화한 KRS TR 0014 규격이 있다. 본 논문에서는 상기 규격의 정적 수직강성 시험방법 중 예비하중 단계, 하중 제거 수준 및 하중 유지시간 관련 문제점 개선을 위해, 패드 관련 국내외 시험규격을 분석한 후 시험방법 안을 제시하였고, 철도현장에 사용되고 있는 패드 4종을 이용하여 시험방법 안을 적용한 정적 수직강성 시험을 수행하였다. 또한 시험방법 안의 적합성을 판단하기 위하여 시험결과에 대한 유효성 평가를 수행하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.468-472
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• 2005

In this paper, the static and dynamic stiffness of the air bearing stage for micro-micro machine tool are examined experimentally. For stiffness and precision concerns, air bearing stages are adapted for 3-axis micro-milling machine which is size of $200x200\;mm^2$. The air bearings in the stage are preloaded by permanent magnets to achieve desired bearing clearance and stiffness for vertical direction. As the stiffness of the air bearing is primary interests, static stiffness test were performed on XY stage in Z direction and Z column in Y direction. Dynamic test were performed on XY stage and Z column, respectively. Both static and dynamic tests were performed in different air pressure conditions. The vertical stiffness of XY stage is about 9 N/ pm where Y stiffness of Z column is much smaller as $1\;N/{\mu}m$ because of the large moment generated by Y force on the column.

• 한국정밀공학회지
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• 제29권10호
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• pp.1050-1055
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• 2012

The bearing coupling section of machine tools is the most important factor to determine their static/dynamic stiffness. To ensure the proper performance of machine tools, the static/dynamic stiffness of the rotating system has to be predicted on the design stage. Various parameters of the bearing coupling section, such as the spring element, node number and preload influence the characteristics of rotating systems. This study focuses on the prediction of the static and dynamic stiffness of the rotating system with the bearing coupling section using the finite element (FE) model. MATRIX 27 in ANSYS has been adopted to describe the bearing coupling section of machine tools because the MATRIX 27 can describe the bearing coupling section close to the real object and is applicable to various machine tools. The FE model of the bearing couple section which has the sixteen node using MATRIX 27 was constructed. Comparisons between finite element method (FEM) predictions and experimental results were performed in terms of the static and dynamic stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1170-1176
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• 2006

This study aims to investigate numerically the static and dynamic stiffness characteristics of porous air bearing and to estimate appropriate permeability values of porous medium. In particular, a new roughness model is proposed and implemented into the commercial CFD code (FLUENT Ver.6.2). The predicted results are extensively compared with experimental data for static cases. The roughness model is also validated through comparison with the results from open literature. For the dynamic cases, the deforming and re-meshing technique is used for describing fluid-solid interactions. It is found that the predictions for static stiffness are in good agreement with experimental data and the dynamic stiffness appears to be relatively smaller than the static stiffness. In addition, moving and dynamic analysis of air bearing seems to be possible to provide qualitative predictions even if there are somewhat discrepancies quantitatively, compared to experimental data.

• Tribology and Lubricants
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• 제20권5호
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• pp.245-251
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• 2004

This paper presents the effects of the bump foil stiffness on the static and dynamic performance of the foil journal bearings. Reynolds equation is used for the static and dynamic performance analyses. To consider the deflection of top foil the top foil is modeled as a elastic beam and the bump foil is modeled as a spring. So in the static performance analysis the load capacity is compared to the various bump foil stiffness and in the dynamic performance analysis the trajectory of journal center is compared to the various bump foil stiffness.

• 한국공작기계학회논문집
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• 제16권1호
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• pp.40-46
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• 2007

High speed machining has become the main issue of metal cutting. Due to increase of the rotational speed of the spindle, problems such as the run-out errors and reduced stiffness must be overcome to improve the machining accuracy. In order to solve the problems, it is important to determine the appropriate clamping unit and tooling system. This paper presents an investigation into an analysis of static stiffness in the main spindle interface. Finite element analysis is performed by using a commercial code ANSYS according to variation of cutting force, clamping force and rotational speed. From the finite element results, it is shown that the rotational speed and clamping force mostly influence on the variation of the static stiffness in the main spindle interface.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.985-988
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• 2002

The Spindle-]fearing System is very important unit for geometrical accuracy in machine tools. To improve effectively the weak point of spindle system, it is necessary that the contribution ratio of spindle core parts to static and dynamic stiffness is clarified. In this paper, static contribution ratio of core parts is calculated by overlapping static deformation of basic spindle design with one flexible parts. The dynamic contribution ratio for natural frequency and dynamic deformation at spindle end is obtained by calculating correlation between original and basic spindle deformation, by curve fitting with regressive method. It is proved the validity of estimation result is correct.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.599-605
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• 2009

The aim of the present study is the characteristics of bridge rubber pads and suggested how to determine the stiffness the pads. A disk bearing is operated as an elastic bearing in the vertical direction and is composed of a Polyether Urethane (polyurethane) disk for elastic support and Polytetrafluoroethylene (PTFE) to accommodate movement. Static tests are conducted in a laboratory to determine the static behavior of a Polyurethane disk. Finite Element (FE) analysis is also performed to verify the static performance. For dynamic behavior, four disk bearings having the identical Polyurethane disk used in the static tests are installed in a full size railway bridge and tested under a running locomotive. From the tests results, the static and dynamic stiffness of disk bearings are estimated and compared with each other. In the procedure to estimate the stiffness of a pad, the dead load(pre-load) of a bridge and live load of a vehicle are considered.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.15-20
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• 2001

This paper presents the experimental study of the static stiffness for the BT shank(7/24 long taper) and the HSK tool shank(1/10 short taper) in the main spindle taper of machine tool. The static stif71ess test was performed under different experimental conditions. It is turned out that the effective axial drawing force is larger than 6kN in the 7/24 test tool shank and BkN in the 1/10 test tool shank. As a test result, considering that the actual drawing force of the machining center is about 1300k2f and axal drawing force 12kN is equivalent amount as a 1220kgf, it is turned out that 1/10 test tool shank superior to 7/24 test tool shank in the static stiffness.