• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1998.04a
• /
• pp.218-227
• /
• 1998

Present study is undertaken to optimize the lubrication reliability and frictional loss of the dynamically-loaded journal bearing in hermetic reciprocating compressor with alternative refrigerant R600a application. Thermodynamic and dynamic analysis has been conducted to investigate cylinder pressure variations by substitution alternative refrigerant R600a for R12. The modeling of the dynamics of the compressor mechanism has been performed with lumped mass method. A mathematical model is developed for analyzing the dynamics of the journal bearing system with the mobility method. It takes into account the effects of the refrigerant species, aspect ratio, clearance ratio and surface roughness. A corresponding computer program is described which enables to obtain the minimum film thickness and frictional loss. Design optimization is graphically performed by parametric studies of the aspect ratio and clearance ratio.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.865-866
• /
• 2006

Bearingless Switched Reluctance Motor(SRM) have combined characteristics of SRM and magnetic bearing. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Bearingless SRM is simple structurally because the permanent magnet does not exist and bearing does not take the influence at the environment because it does not exist and has strong torque, and loss of bearing by bearing current has the advantage not to exist. In this paper, a design method of bearingless SRM for suspension power and starting torque is proposed. The design model is implement by maxwell.

• Steel and Composite Structures
• /
• v.9 no.2
• /
• pp.173-189
• /
• 2009

This paper presents a study on the behavior and design of bolted stainless steel plates under in-plane tension. Using an experimentally validated finite element (FE) program strength of stainless steel bolted plates under tension is examined with an emphasis on plate bearing mode of failure. A numerical parametric study was carried out which includes examining the behavior of stainless steel plate models with various proportions, bolt locations and in two different material grades. The models were designed to fail particularly in bolt tear-out and material piling-up modes. In the numerical simulation of the models, non-linear stress-strain material behavior of stainless steel was considered by using expressions which represent the full range of strains up to the ultimate tensile strain. Using the results of the parametric study, the effect of variations in bolt positions, such as end and edge distance and bolt pitch distance on bearing resistance of stainless steel bolted plates under in-plane tension has been investigated. Finally, the results obtained are critically examined using design estimations of the currently available international design guidance.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.993-996
• /
• 2005

This paper is concerned with transfer process on hot forging of bearing hub. Workers on hot forging have difficulty in working by high temperature and weight workpiece. And In conventional got forging of bearing hub, the material wasted to the flash accounts approximately 10% of the original workpiece. It is need manufacture automation and reduce the cost of forged products. Surface treatment of die and lubricant are investigated from experiment and FE-simulation for analysis of forming simulation. In order to hot forging process design considered flash thickness and blocker geometry and initial temperature of die and billet. This transfer process gave comparatively good results compared with actual products.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.12 s.243
• /
• pp.1567-1573
• /
• 2005

This paper introduces a new active magnetic bearing(AMB) that can provide both radial and axial control functions in one bearing unit without axial disk. It has a structure of double four-pole AMB or a four-pole AMB where each core is split into two axially. The cores have two kinds of coil winding; they independently generate fluxes on the planes perpendicular or parallel to the shaft. For the radial control action, it works just like a conventional four-pole AMB. Meanwhile, for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. In this paper, the proposed structure, principle, and design process based on magnetic flux analysis are introduced, and its feasibility is experimentally verified by using a simple PD control algorithm with a feedforward loop to compensate the coupled flux effect.

• Journal of the Korean Society for Precision Engineering
• /
• v.1 no.2
• /
• pp.47-57
• /
• 1984

The porous matterials are used both to control the flow of the compressed gas and to serve as the bearing surface. This porous design offers several advantages over the conventional externally pressurized gas bearings. It can simplify the construction, lower the gas consumption, and make the cleaning of the gas supply less critical. Test apparatus was cinstructed to experi- mentally investigate maximum load capacity of thrust bearing was measured 200 Kg (15Kg/$\mu$m), and radial bearing was 36 Kg/$\mu$m. And a rotation accuracy of face waving was 0.0127$\mu$m, and center waving was measured 0.5 $\mu$m. Finally, the use of this method of design and manufacturing will contribute to many practical application in the field required for precision and high stability.

• Journal of the Korean Society of Safety
• /
• v.12 no.1
• /
• pp.9-18
• /
• 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.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.10
• /
• pp.146-153
• /
• 1996

This paper presents the development of a collocated capacitance sensor and its application to the controller design for magnetic bearing supported rotor systems. The main feature of the sensor is that it is made of a compact printed circuit board(PCB) so that it can be built into the actuator coil of the magnetic bearing unit. The singnal processing unit hax been also developed. The experi- mental results of the sensor performance evaluation on sensitivity, bandwidth and resolution are presented. Then, simulation study shows the advantages of the collocated sensor for magnetic bearings over the nonco- llocated sensor. Finally, the experimental result on the performance of the collocated sensor based contrl- ler for a magnetic bearing rotor system is presented.

• Tribology and Lubricants
• /
• v.36 no.1
• /
• pp.27-33
• /
• 2020

Self-equalizing tilting pad thrust bearings are usually employed in turbomachines to achieve high stability and reliability. A tilting pad bearing can incorporate self-equalizing links to handle the misalignment between the bearing and the thrust collar. In this popular design method, the pads sit on the upper-level plates and the lower-level plates stay on the retainer base. With misalignment, the pads that are heavily loaded are pushed down. Consequently, the link pushes up the pads on the opposite side, keeping the bearing surface parallel to the thrust collar surface. The self-equalizing link is used to handle the misalignment from the thermal and mechanical effects. In this study, the experimental investigation deals with the performance of self-equalizing tilting pad thrust bearings. The test rig for evaluating the performance of bearing is developed which can control the misalignment angle. Simultaneous measurements are taken for the force acting on each pad. Pad metal temperature and oil film thickness are functions of the shaft speed, bearing load, misalignment angle, and design of leveling plates. The effect of misalignment on bearing performance is discussed. The results demonstrate that the load on each pad depends on the test conditions(especially misalignment angle), and the load influences the performance of bearings.

• Geomechanics and Engineering
• /
• v.5 no.4
• /
• pp.363-377
• /
• 2013

Any structure constructed on the earth is supported by the underlying soil. Foundation is an interfacing element between superstructure and the underlying soil that transmits the loads supported by the foundation including its self weight. Foundation design requires evaluation of safe bearing capacity along with both immediate and long term settlements. Weak and compressible soils are subjected to problems related to bearing capacity and settlement. The conventional method of design of footing requires sufficient safety against failure and the settlement must be kept within the allowable limit. These requirements are dependent on the bearing capacity of soil. Thus, the estimation of load carrying capacity of footing is the most important step in the design of foundation. A number of theoretical approaches, in-situ tests and laboratory model tests are available to find out the bearing capacity of footings. The reliability of any theory can be demonstrated by comparing it with the experimental results. Results from laboratory model tests on square footings resting on sand are presented in this paper. The variation of bearing capacity of sand below a model plate footing of square shape with variation in size, depth and the effect of permissible settlement are evaluated. A steel tank of size $900mm{\times}1200mm{\times}1000mm$ is used for conducting model tests. Bearing capacity factor $N_{\gamma}$ is evaluated and is compared with Terzaghi, Meyerhof, Hansen and Vesic's $N_{\gamma}$ values. From the experimental investigations it is found that, as the depth of sand cushion below the footing ($D_{sc}$) increases, ultimate bearing capacity and settlement values show an increasing trend up to a certain depth of sand cushion.