• Title/Summary/Keyword: Hydrostatic journal bearing

Search Result 78, Processing Time 0.025 seconds

Development of the Optimized Angle Head for Internal Shape Machining Using Five-Axis Machine Tool (5축가공기를 활용한 내면 형상 가공용 최적 앵글헤드의 개발)

  • Hwang, Jong-Dae;Kim, Jae-Hyun;Cho, Young-Tae;Jung, Yoon-Gyo;Ko, Hae-Ju
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.14 no.1
    • /
    • pp.123-129
    • /
    • 2015
  • In general, recent critical studies of five-axis machine have tended to center on the question of effective machining to realize complex shape parts. However, the hydrostatic bearing and journal bearing, both of which are involved in the complex process of dividing the processing of internal precision-shape machining, must be optimized. Although the angle head is designed to machine the internal shape as it approaches the inner diameter of the work piece, research on the angle head in five-axis machining has received only minimal attention in domestic industries. In this study, an angle head which is optimized for effective internal shape machining is developed. In pursuit of this purpose, 3D and 2D designs of the angle head for five-axis machining are devised. Reliability is secured through static performance tests and machining accuracy evaluations of the angle head in keeping with the machining accuracy standard of 0.2mm for hydrostatic bearings.

Load-Bearing Capacity of Subsea Pipeline with Variation of Sea Water Depth and Buried Depth (수심과 퇴적 깊이 변화에 따른 해저배관의 하중지지능력 평가)

  • Baek, Jong-Hyun;Kim, Young-Pyo;Kim, Woo-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.36 no.10
    • /
    • pp.1131-1137
    • /
    • 2012
  • Subsea pipelines have been operated with buried depths of 1.2-4m underneath the seabed to prevent buoyancy and external impacts. Therefore, they have to show resistance to both the soil load and the hydrostatic pressure. In this study, the structural integrity of a subsea pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. A parametric study showed that the internal pressure increased the plastic collapse depth by increasing the resistance to plastic collapse. The hoop stress increased with an increase in the buried depth for the same water depth; however, the hoop stress decreased with an increase in the water depth for the same buried depth.

A Study on the Lubrication Characteristics of the Hydro-Static Journal Bearing for a Crank Shaft Pin Turner by Applying Dimple (딤플이 크랭크 샤프트 핀 터너 유정압 베어링의 윤활특성에 미치는 영향에 관한 연구)

  • Seo, Mi Na;Lee, Deug Woo;Ha, Yang Hyup;Lee, Sang Min;Kim, Yong Woo
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.31 no.8
    • /
    • pp.715-720
    • /
    • 2014
  • Recently, surface texturing technologies have been widely used in lots of industries to increase the machinery efficiency. In this research, the lubrication characteristics of a crank shaft pin turner bearing with dimples were studied. When increasing the dimples, the load carrying capacity due to the increased pressure was increased because those have sealing effects. Also, the run-out error of the bearing was decreased. Therefore, it is important to consider the depth, the number and the distribution of dimples when designing the hydrostatic journal bearing.

A Analytical Study on Seismic Performance of Stainless Water Tank using Lead Rubber Bearing (납고무받침을 이용한 스테인리스 물탱크 내진성능에 관한 해석적 연구)

  • Kim, Hu-Seung;Oh, Ju;Jung, Hie-Young
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.19 no.11
    • /
    • pp.230-236
    • /
    • 2018
  • Earthquakes over 5.0 on the Richter scale have recently occurred in Korea, which has led to interest in the seismic safety of structures. If a water storage facility is damaged by an earthquake, the water could leak, and the insufficient water would make fire suppression difficult. Therefore, a water storage facility should satisfy safety requirements for earthquakes. In this study, the seismic performance of a water tank was improved by installing a lead rubber bearing between the foundation and the tank. It designed the lead rubber bearing available to the existed concrete foundation. ANSYS was used for modeling to consider the interaction between the fluid and structure of the tank and the hydrostatic and hydrodynamic pressure using four seismic waves. In the case of hydrostatic pressure at 2.5 water level, full level, the same stress appeared irrespective of whether the seismic isolation was installed. When hydrostatic pressure and hydrodynamic pressures are applied at the same time, the seismic-isolated water tank showed less seismic force, and the damping ratio was lower than that of general seismic isolation. This occurred because the weight of the water tank is much smaller than the stiffness of the seismic isolation. The result is expected to be used for further research on seismic capacity evaluation for water tanks.

Performance of Hydrostatic/hybrid Journal Symmetric/asymmetric Bearings using Slot-entry Restrictor Under Couple Stress Lubricants

  • Ram, Nathi;Yadav, Saurabh Kumar;Sharma, Satish C.
    • Tribology and Lubricants
    • /
    • v.33 no.5
    • /
    • pp.187-201
    • /
    • 2017
  • This paper presents the impact of couple stress lubricant on performance of slot-entry hydrostatic/hybrid journal symmetric/asymmetric bearings. Reynolds Equation using Finite Element Technique has been solved for the flow of couple stress and Newtonian lubricants in bearings. The results have been computed for concentric design pressure ratio(${\beta}^{\ast}=0.5$), slot width ratio (SWR = 0.25) and chosen parameters of couple stress lubricant ${\bar{l}}=5$, 10, 15. It is observed that numerically simulated outcomes for slot-entry journal bearings, considering the influence of couple stress lubricant indicate a substantial improvement in the performance of the bearing.

Development of a high precision CNC lathe for mirror surface machining (경면가공용 고정밀 CNC 선반 개발)

  • 박청홍;이후상;신영재;이군석;김춘배
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.14 no.3
    • /
    • pp.82-88
    • /
    • 1997
  • In this paper, the development of a precision CNC lathe prototype for mirror surface machining is presented. To obtain high precision machining accuracy, a hydrostatically supported precision spindle and a sliding guideway with turcite pad are adopted as the motion elements. The machining accuracy of the prototype machine, and the motional accuracy of its motion elements are tested and evaluated to confirm the validity of the application of these elements on the prototype. The hydrostatic spindle shows 0.09 .mu. m of rotational accuracy and the guideway shows about 0.8 .mu. m/170mm of horizontal straightness. The sur- face roughness of cupper and aluminium cylinder machined by the prototype machine with diamond tool are 0.07 .mu. m and 0.10 .mu. m Rmax respectively. From these results, it is verified that the prototype lathe is avail- able for high precision machining.

  • PDF

Structural Characteristic Analysis of an Ultra-Precision Machine for Machining Large-Surface Micro-Features (초정밀 대면적 미세 형상 가공기의 구조 특성 해석)

  • Kim, Seok-ll;Lee, Won-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.31 no.12
    • /
    • pp.1173-1179
    • /
    • 2007
  • In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

An Analysis for Turbulent Hybrid Bearings with Fluid Inertia and Swirl Injection Effects (유체의 관성력과 스월의 영향을 고려한 난류 하이브리드 베어링의 해석)

  • 이용복;김창호;최동훈
    • Tribology and Lubricants
    • /
    • v.12 no.3
    • /
    • pp.85-91
    • /
    • 1996
  • An analysis for turbulent hybrid beatings with fluid inertia and swirl injection effect was derived for studying static characteristics of swirl-controlled hybrid journal. The swirl-controlled hybrid journal beating is considered to have more freedom in stability control in high speed rotating machinery. Current analysis is compared with experimental results with 3-recess hydrostatic journal bearing. The analysis revealed that the fluid momentum exchange at orifice discharge could produce pressure rise inside the recess region which can control the shear flow induced by journal rotation. The analysis also shows that the swirl-controlled hybrid journal beating has a capability of controlling load carrying capacity and stability by manipulating supply pressure and injection angle.

Analysis on the Static Performance of Vacuum-Preloaded Porous Air Bearings (진공예압형 다공질 공기베어링의 압력분포 및 성능해석)

  • Khim, Gyungho;Park, Chun Hong
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.30 no.12
    • /
    • pp.1327-1333
    • /
    • 2013
  • Air bearings are widely used in precision stages because of low friction and high motion accuracy, however, they suffer from low stiffness in comparison with rolling bearings or hydrostatic bearings. So, several preloading methods using weight, magnet and vacuum force, and opposing pads have been used to increase the stiffness of the air bearings. In this paper, pressure distributions of the vacuum preloaded porous air bearings are calculated using the proposed method. And then, the load capacity and stiffness are analyzed. For the vacuum preloaded air bearings, the stiffness is increased owing to reduced bearing clearance by vacuum force. The simulation results indicate that variation of vacuum pressure with clearance in the vacuum pocket gives rise to low stiffness, so the vacuum pocket should be designed for pressure to be constantly maintained regardless of the bearing clearance by means of large effective pumping speed.

Design, Fabrication, and Testing of a MEMS Microturbine

  • Jeon Byung Sun;Park Kun Joong;Song Seung Jin;Joo Young Chang;Min Kyoung Doug
    • Journal of Mechanical Science and Technology
    • /
    • v.19 no.2
    • /
    • pp.682-691
    • /
    • 2005
  • This paper describes the design, fabrication, and testing of a microturbine developed at Seoul National University. Here, the term 'microturbine' refers to a radial turbine with a diameter on the order of a centimeter. Such devices can be used to transmit power for various systems. The turbine is designed using a commercial CFD code, and it has a design flow coefficient of 0.238 and work coefficient of 0.542. It has 31 stator blades and 24 rotor blades. A hydrodynamic journal bearing and hydrostatic thrust bearings counteract radial and axial forces on the rotor. The test turbine consists of a stack of five wafers and is fabricated by MEMS technology, using photolithography, DRIE, and bonding processes. The first, second, fourth, and fifth layers contain plumbing, and hydrostatic axial thrust bearings for the turbine. The third wafer contains the turbine's stator, rotor, and hydrodynamic journal bearings. Furthermore, a turbine test facility containing a flow control system and instrumentation has been designed and constructed. In performance tests, a maximum rotation speed of 11,400 rpm and flow rate of 16,000 sccm have been achieved.