• Journal of the Korea Convergence Society
• /
• v.8 no.5
• /
• pp.179-184
• /
• 2017

The cage of a tapered roller bearing keeps the gap between the rollers, which prevents friction, wear and suppresses heating. The material of the cage is changing from metal to plastic for lightening the weight. If the cage is severely deformed due to resonance, the roller may not be able to roll and even get off the cage. In this paper, the dynamic characteristics of the cage is analyzed according to the cage material. Under the assumption that a train runs at the highest speed, frequency harmonics of that speed is calculated, and the comparative analysis is carried out in order to select the optimum thickness of the cage, which is easy to change among the cage design variables for avoiding the resonance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.4
• /
• pp.464-469
• /
• 2019

Tapered roller bearings are used widely in vans, trucks, and trains because they can support the vehicle in a stable manner even under a heavy load. The cage of a tapered roller bearing maintains the gap between the rollers, which prevents friction wear and suppresses heating. If the cage is severely deformed due to resonance, the roller may not be able to roll smoothly and even leave the cage. Consequently, it is very important to analyze the dynamic characteristics of the cage for reliable performance of a bearing. The cage essentially has geometrical tolerance in the manufacturing process. In this paper, the effects of those geometrical imperfections on the dynamic characteristics of the cage were investigated. As a result, natural frequency separation occurred near the natural frequency of the ideal cage due to geometrical imperfections. In addition, the interval was proportional to the magnitude of the geometric error, and the interval increased with increasing mode number.

• Tribology and Lubricants
• /
• v.31 no.6
• /
• pp.281-286
• /
• 2015

Automotive transmission systems are assembled with a large number of gears and shafts, and rolling bearings are used to ensure their smooth operation. Gear oil in the gear box contains solid particles such as wear debris from contacting gears and metallic chips. This particle-enriched lubricating oil can cause premature failure of the rolling bearings. Research aimed at improving the service life of these rolling bearings has been confined mainly to design and lubrication of the inner/outer rings and the rolling elements. In this paper, we redesigned the shape of the cage pocket of a deep groove ball bearing to reduce the premature failure due to particle contamination. Test bearings are assembled with this new cage design containing a hole punched in the cage pocket. Endurance tests are carried out using the contaminated lubricating oil with miracle grid as hard particle. The duration and damaged bearing component shapes are compared for two different cages. The B₁₀ life of bearing with new cage is increased by about 66% compared to the conventional cage. This is because the hard particles can be easily discharged through the pocket hole without staying for a long time in the lubrication regions. This greatly decreases abrasive wear and dents on the highly stressed ball bearing surfaces. Therefore, the cage design of this study, containing a pocket hole, can significantly delay the premature failure of rolling bearings and improve the endurance life.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.537-538
• /
• 2011

• Tribology and Lubricants
• /
• v.40 no.1
• /
• pp.1-7
• /
• 2024

Ball bearings are a major component of mechanical parts for transmitting rotation. Compared to tapered roller bearings, ball bearings offer less rolling resistance, which leads to reduced heat generation during operation. Because of these characteristics, ball bearings are widely used in electric vehicles and machine tools. The design of ball bearing cages has recently emerged as a major issue in ball bearing design. Cage design requires pre-verification of performance using theoretical or experimental formula or computational fluid dynamics (CFD). However, CFD analysis is time-consuming, making it difficult to apply in case studies for design decisions and is mainly used in performance prediction following design confirmation. To use CFD in the early stages of design, main-taining analytical accuracy while reducing the time required for analysis are necessary. Accordingly, this study proposes a laminar steady-state segment CFD technique to solve the problem of long CFD analytical times and to enable the use of CFD analysis in the early stages of design. To verify the reliability of the CFD analysis, a bearing drag torque test is performed, and the results are compared with the analytical results. The proposed laminar steady-state segment CFD technique is expected to be useful for case studies in bearing design, including cage design.

• BMB Reports
• /
• v.55 no.4
• /
• pp.175-180
• /
• 2022

Peptides are gaining substantial attention as therapeutics for human diseases. However, they have limitations such as low bioavailability and poor pharmacokinetics. Periostin, a matricellular protein, can stimulate the repair of ischemic tissues by promoting angiogenesis. We have previously reported that a novel angiogenic peptide (amino acids 142-151) is responsible for the pro-angiogenic activity of periostin. To improve the in vivo delivery efficiency of periostin peptide (PP), we used proteins self-assembled into a hollow cage-like structure as a drug delivery nanoplatform in the present study. The periostin peptide was genetically inserted into lumazine synthase (isolated from Aquifex aeolicus) consisting of 60 identical subunits with an icosahedral capsid architecture. The periostin peptide-bearing lumazine synthase protein cage nanoparticle with 60 periostin peptides multivalently displayed was expressed in Escherichia coli and purified to homogeneity. Next, we examined angiogenic activities of this periostin peptide-bearing lumazine synthase protein cage nanoparticle. AaLS-periostin peptide (AaLS-PP), but not AaLS, promoted migration, proliferation, and tube formation of human endothelial colony-forming cells in vitro. Intramuscular injection of PP and AaLS-PP increased blood perfusion and attenuated severe limb loss in the ischemic hindlimb. However, AaLS did not increase blood perfusion or alleviate tissue necrosis. Moreover, in vivo administration of AaLS-PP, but not AaLS, stimulated angiogenesis in the ischemic hindlimb. These results suggest that AaLS is a highly useful nanoplatform for delivering pro-angiogenic peptides such as PP.

• Tribology and Lubricants
• /
• v.35 no.3
• /
• pp.158-168
• /
• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• Smart Structures and Systems
• /
• v.9 no.4
• /
• pp.303-311
• /
• 2012

The possibility of suppressing critical speeds by using electromagnetic actuators (EMAs) is assessed experimentally in this paper. The system studied is composed of a horizontal flexible shaft supported by two ball bearings at one end and one roller bearing that is located in a squirrel cage at the other end. Four identical EMAs supplied with constant current are utilized. The EMAs associated to the squirrel cage constitutes the hybrid bearing. Results obtained, show that the constant current, when applied to the EMAs, produces a shift of the first critical speed toward lower values. Moreover, the application of constant current for a speed interval around the critical speed enables a smooth run-up or run-down without crossing any resonance.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1558-1565
• /
• 2015

In this paper, we propose a new method for detecting bearing faults using vibration signals. The proposed method is based on support vector machines (SVMs), which treat the harmonics of fault-related frequencies from vibration signals as fault indices. Using SVMs, the cross-validations are used for a training process, and a two-stage classification process is used for detecting bearing faults and their status. The proposed approach is applied to outer-race bearing fault detection in three-phase squirrel-cage induction motors. The experimental results show that the proposed method can effectively identify the bearing faults and their status, hence improving the accuracy of fault diagnosis.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.237-242
• /
• 2001

In this paper, we theoretically analyzed the NRRO(the non-repeatable run-out) of a ball bearing with ball geometric imperfection. The quasi-static and dynamic analysis of a ball bearing was performed to calculate the displacement of shaft center caused by the ball form errors while the shaft is rotating. From consideration of the generating mechanism of NRRO, it is found that the size and form errors of ball generate vibrations with (equation omitted)$\_$c/ and n(equation omitted)$\_$b/${\pm}$(equation omitted)$\_$c/(where n is even) components, respectively. The ball form errors of a ball bearing were precisely measured and NRRO of a ball bearing was calculated using the measured data. A statistical approach was peformed to analyze NRRO of ball bearings with radial errors.