• 제목/요약/키워드: Squeeze Pressure

검색결과 92건 처리시간 0.022초

RF-MEMS 스위치용 마이크로 외팔보의 감쇠특성 (Damping Characteristics of a Microcantilever for Radio Frequency-microelectromechanical Switches)

  • 이진우
    • 한국소음진동공학회논문집
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    • 제21권6호
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    • pp.553-561
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    • 2011
  • A theoretical approach is carried out to predict the quality factors of flexible modes of a microcantilever on a squeeze-film. The frequency response function of an inertially-excited microcantilever beam is derived using an Euler-Bernoulli beam theory. The external force due to squeeze-film phenomenon is developed from the Reynolds equation. Slip boundary conditions are employed at the interfaces between the fluid and the structure to consider the gas rarefaction effect, and pressure boundary condition at both ends of fluid analysis region is enhanced to increase the exactness of predicted quality factors. To the end, an approximate equation is derived for the first bending mode of the microcantilever. Using the approximate equation, the quality factors of the second and third bending modes are calculated and compared with experimental results of previously reported work. The comparison shows the feasibility of the current approach.

절단 원추형 Squeeze Film Damper 베어링과 회전축계의 동특성에 관한 연구 (A Study on the Dynamic Characteristics of Truncated Cone Type Squeeze Film Damper Bearing and Rotor System)

  • 윤석철
    • 한국안전학회지
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    • 제12권1호
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    • pp.9-18
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    • 1997
  • This paper is a study on the dynamic characteristics of truncated cone type squeeze film damper(SFD) bearing and rotor system. This model can alter the radial oil film gap which Is Important to the performance of rotor-bearing system and manufactured easily to change the shape concept of traditional circular type SFD bearing. In theoretical analysis, the oil film pressure distribution, the oil film force, the film damping coefficient and the eccentricity ratio, etc. were induced with regard to the film inertia effect. The film damping coefficients and optimum design parameters are calculated. When unbalance parameter U is greater than 0.2, the nonlinear vibration such as "Jump" phenomena appears in the vicinity of rotor critical speed. At this time, the increases of bearing parameter U, journal distance S, Reynolds number Re can control this unstable vibration. The experimental results show that SFD hearing and rotor system which are designed according to the design parameters in the stable region are operated stably in rotational speed 9,600rpm without nonsynchronous behavior.

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용탕단조법으로 제조된 AC4C 합금기 세라믹강화 복합재료의 특성연구 (Characterization of the Ceramic Reinforced AC4C Matrix Composites Processed by Squeeze Casting)

  • 김억수
    • 한국주조공학회지
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    • 제25권2호
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    • pp.88-94
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    • 2005
  • The microstructure and mechanical property of the ceramic reinforced AC4C matrix composites processed by squeeze casting were investigated. In this study Kaowool and Saffil fiber which are ceramic reinforcements are used as preform materials. As a matrix material, Al-7wt.%Si-0.3wt.%Mg(AC4C) has been used. In case of Kaowool and Saffil/AC4C composites, 7.5 MPa squeezing pressure and minimum 7.0% binder amount are needed to produce sound composite materials. The tensile strength of Kaowool/ AC4C composite is lower than the matrix metal and this can be explained by the melt unfilling due to formed cluster of Kaowool reinforcements. But the mechanical properties of hardness, wear resistance and thermal expansion are better than the matrix materials due to the strengthening effect of ceramic reinforcements.

용탕단조한 Al-7%Si-0.3% Mg합금 봉상시료의 편석거동 (Segregation of Squeeze Cast Al-7% Si-0.3% Mg Alloy Bars)

  • 김기영;기석도;박종락
    • 한국주조공학회지
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    • 제13권1호
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    • pp.71-80
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    • 1993
  • Squeeze casting has advantages to improve mechanical properties of nonferrous castings without losing high productivity. Sound pore free structure makes it possible to be subjected to heat treatment and welding. This process became popular to produce lighter automobile parts alternating cast iron parts. It has, however, two disadvantages of segregation and scattered structure due to the solidified layers in sleeve. In this study segregation behavior of squeeze cast Al-7%Si-0.3%Mg alloy bars was investigated using HVSC machine under various injection conditions. Degree of segregation decreased with injection pressure and effect of injection velocity on it was small. Segregation mode of solute was strongly governed by solidification mode and flow pattern.

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용탕단조법에 의한 휘스커강화 Al합금기 복합재료의 고속초소성 (High Strain Rate Superplasticity of Whisker Reinforced Aluminum Alloy Matrix Composites Fabricated by Squeeze Casting)

  • 임석원;유전의칙
    • 한국주조공학회지
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    • 제21권6호
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    • pp.359-365
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    • 2001
  • The superplastic behavior of whisker reinforced aluminum alloy matrix composites fabricated by squeeze casting as one of high pressure routes was investigated. The preforms of ${\alpha}-Si_3N_4$ and ${\beta}-SiC$ whiskers without any binder as a reinforcement were used. The matrix materials were 2024 and 7075 aluminum alloys. For the purpose of optimum superplastic condition, respectively, the whiskers volume fraction, extrusion temperature, tensile test temperature and initial strain rate were changed. Fracture surface of tested specimens were observed by SEM. By the results, it became possible to produce superplastic composites by applying only a hot extrusion process to composites obtained by the squeeze casting. The superplastic composites developed are ${\alpha}-Si_3N_4w/7075$, ${\alpha}-Si_3N_4w/2024$ and ${\beta}-SiCw/2024$ systems at high strain rate.

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기판에 수직으로 진동하는 다공 평판 미소구조물의 공기감쇠 (Squeeze Film Damping of Perforated Planar Microstructures)

  • 김응삼;조영호;김문언
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권1호
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    • pp.64-69
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    • 2000
  • This paper investigates the equeeze film damping of a perforated planar micromechanical structure that oscillates in the normal direction to the substrate. Special focus has been places on the effect of holes and edges of the perforated planar microstructures on the squeeze film damping of oscillatory motions. Theoretical models and test structures of the squeeze film damping have been developed for the transversely oscillating perforated plates. A set of nine different test structures, having three different sized with three different numbers of perforations, has been fabricated and tested. The experimental Q-factors, measured from the fabricated test structures, are compared with the theoretical values, estimated from finite element analysis. It is found that the finite element analysis overestimates the Q-factors up to 150% of the experimental values. Major discrepancy comes from the inaccuracy of the zero pressure condition, placed by the finite element analysis along the perforated edges.

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스퀴즈필름효과를 고려한 인공심장밸브의 닫힘시 동적거동 해석 (Dynamic Behavior Analysis of the Heart Valve Prostheses Considering Squeeze Film Effect During Closing Phase)

  • 천길정
    • 대한기계학회논문집
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    • 제19권2호
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    • pp.443-450
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    • 1995
  • An analysis of the dynamics of a mechanical monoleaflet heart valve prosthesis in the closing phase is presented. Employing the moment equilibrium principles on the occluder motion and the squeeze film dynamics of the fluid between the occluder and the guiding strut at the instant of impact, the velocity of the occluder tip and the impact force were computed. The dynamics of fluid being squeezed between the occluder and the guiding struts is accounted for by Reynold's equation. The effect of the fluid being squeezed between the occluder and the guiding strut was to reduce the velocity of the occluder tip at the instant of valve closure as well as dampen the fluttering of the occluder before coming to rest in the fully closed position. The squeeze film fluid pressure changed rapidly from a high positive value to a relatively large negative value in less than 1 msec. The results of this study may be extended for the analysis of cavitation inception, mechanical stresses on the formed elements and valve components as well as to estimate the endurance limits of the prosthetic valves.

2-D Braided Textile 금속복합재료의 성형과 특성 해석 (Fabrication and Analytical Characterization of 2-D Braided Textile Metal Matrix Composites)

  • 이상관;김효준;변준형;홍순형
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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    • pp.38-41
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    • 2001
  • A new 2-D braided textile metal matrix composite was developed and characterized. The constituent materials consist of PAN type carbon fiber as reinforcements and pure aluminum as matrices. The braided preforms of different braider yarn angles were fabricated. For a fixed bundle size of 12K, three braider yarn angles was selected: $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. The braided preforms were infiltrated with pure Al by vacuum assisted squeeze casting. Through the investigation of melt pressing methods and the effects of process parameters such as applied pressure, and pouring temperature, the optimal process conditions were identified as follows: applied pressure of 60MPa, pouring temperature of $800^{\circ}C$. Using the measured geometric parameters, 3-D engineering constants of metal matrix composites have been determined from the elastic model, which utilizes the coordinate transformation and the averaging of stiffened and compliance constants based upon the volume of each reinforcement and matrix material.

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공기압 실린더용 저마찰 피스톤 실의 특성해석 (Analysis of a Low Friction Piston Seal in Pneumatic Cylinders)

  • 김도태;장중걸
    • 유공압시스템학회논문집
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    • 제8권3호
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    • pp.21-26
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    • 2011
  • Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seals in high speed pneumatic cylinders is analyzed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the squeeze type piston seal are simulated with variation of the seal radial installed interference, the operating pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the squeeze type piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

열-나노임프린트 리소그래피 공정에서의 폴리머 유동에 대한 해석적 접근 (Analytical Approach of Polymer Flow in Thermal Nanoimprint Lithography)

  • 김국원;김남웅
    • 한국공작기계학회논문집
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    • 제17권3호
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    • pp.20-26
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    • 2008
  • Nanoimprint lithography(NIL) is becoming next generation lithography of significant interest due to its low cost and a potential patterning resolution of 10nm or less. Success of the NIL relies on the adequate conditions of pressure, temperature and time. To have the adequate conditions for NIL, one has to understand the polymer flowing behavior during the imprinting process. In this paper, an analytical approach of polymer flow in thermal NIL was performed based on the squeeze flow with partial slip boundary conditions. Velocity profiles and pressure distributions of the polymer flow were obtained and imprinting forces and residual thickness were predicted with the consideration of the slip velocity between the polymer and the mold/substrate. The results show that the consideration of the slip is very important for investigating the polymer flow in Thermal NIL.