• Tribology and Lubricants
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• v.40 no.5
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• pp.157-162
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• 2024

This study evaluates the structural stability of the drive system of a monorail and investigates the causes of derailment accidents using finite element analysis. We assume a scenario where the gear pitch decreases by 1 mm owing to construction defects and perform dynamic analysis as the pinion gear traverses the abnormal pitch interval of the rack gear. The contact analysis between the rack and pinion gears reveals that the pinion gear collides in the abnormal pitch range due to the construction defect at the rack gear connection. The collision generates stresses exceeding the yield strength of the gear and rail materials, leading to plastic deformation. This study additionally investigates the bearings where the actual damage occurs utilizing the load data derived from the analysis. Findings indicate that plastic deformation and fatigue damage occurs in the bearing retainer and balls owing to the impact load, leading to ball detachment and retainer failure. Moreover, repetitive impact loads can rapidly degrade bearing durability, directly contributing to accidents. The findings of this study should be considered during the design, manufacturing, assembly, and maintenance processes of monorail system components, enhancing the safety through precise manufacturing and assembly practices.

• Tribology and Lubricants
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• v.21 no.6
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• pp.278-282
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• 2005

Deep groove ball bearing is installed in a control element of an integral nuclear reactor, where water is used as coolant and lubricant. This bearing is made of STS440C stainless steel for the raceways and the balls to use in radioactive environment and water. It is known that the retainer design affects ball bearing operability and endurance life, however there is no verified retainer design and material for water lubricated ball bearing. Four kinds of retainers are manufactured for the endurance test of water lubricated deep groove ball bearing. Three of them are commercially developed types and the other is designed for this research. It is verified that ball bearings with steel pressed and general plastic retainer can not survive to required life in the water, however bearings with machined type and cylinder type retainer can survive. This proves that one of the major design parameters for water lubricated ball bearing is retainer type and material. In this paper, experimental research of endurance test for water-lubricated ball bearing are reported.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.737-742
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• 2015

Course correction munition are a weapson system for precision attacks and are assembled by applying a ballistic control system to existing projectiles. The roll control system is a subsystem of the ballistic control system and is placed between the guidance and control units inside of the projectile, which undergoes a 5000g lateral acceleration. Thus, it is very important to design the system to endure this load. Many developed countries evaluate the performance and safety of course correction munitions' parts using live-fire gun launch tests or a soft recovery system. However, these methods are expensive and slow. Thus, in this study, we develop impact analysis model of the roll control system using CAE. We apply the code to simulate impact phenomenon and use Johnson-Cook material model for modeling the high strain rate effect on the materials. We also design bearings in detail to analyze their behavior and verify the reliability of CAE model through gas-gun impact tests of the roll control system.