• Tribology and Lubricants
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• v.31 no.3
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• pp.109-124
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• 2015

This paper presents a wear analysis procedure for the journal bearings on a stripped-down single-cylinder engine during start-up and coast-down by motoring. A journal bearing is in the mixed elastohydrodynamic (EHL) lubrication region when the shaft speed is less than the corresponding lift-off speed. Below the lift-off speed, a wear scar can form on bearing surfaces. In part 1 of this paper, we develop the appropriate formulations and the calculation procedure for the analysis. Specifically, we formulate an equation for modified film thickness in a journal bearing considering the additional wear volume. In order to obtain the modified specific wear rate induced by the modified Archard’s wear coefficient, we utilized the extended non-dimensional diagram for the specific wear rate, k, the fractional film defect coefficient, Ψ and the asperity load sharing factor, γ₂. This asperity load sharing factor is newly calculated by setting the Zhao-Maietta-Chang (ZMC) asperity contact pressure equation coupled with the central film thickness equation derived by using the ZMC asperity contact model equal to the modified central contact pressure derived by using the central (or maximum) contact pressure at the dry rough line-contact configuration. We can use the procedure introduced in this paper to determine the lifetime (or longterm) linear wear in radial journal bearings that is a result of repeated stop-start cycles.

• Tribology and Lubricants
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• v.35 no.1
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• pp.77-86
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• 2019

The present study focuses on the effect of staggered integration factor (SIF) on Morton effect simulation results. The Morton effect is a synchronous rotordynamic instability problem caused by the temperature differential across the journal in fluid film bearings. Convection and conduction of heat in the thin film displaces the hot spot, which is the hottest circumferential position in the thin film, from -20 to 40 degrees ahead of the high spot, where the minimum film clearance is experienced. The temperature differential across the journal causes a bending moment and the corresponding thermal bow in the rotating frame acts like a distributed synchronous excitation in the fixed frame. This thermal bow may cause increased vibrations and continued growth of the synchronous orbit into a limit cycle. The SIF is developed assuming that the response of the rotor-lubricant-bearing dynamic system is much quicker than that of the bearing-journal thermal system, and it is defined as the ratio between the simulation time of the thermal system and the rotor-spinning period. The use of the SIF is unavoidable for efficient computing. The value of the SIF is chosen empirically by the software users as a value between 100 and 400. However, the effect of the SIF on Morton effect simulation results has not been investigated. This research produces simulation results with different values of SIF.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.233-238
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• 2024

The pipe cleaning process is a crucial step in the shipbuilding process of a shipyard. It involves removing foreign substances from the inside of the pipes before moving on to the stage of testing equipment after installing the pipes. If there are foreign substances inside the pipes and the equipment is tested, the foreign substances can enter the high-priced equipment and become a factor in the breakdown of pumps, gears, bearings, and other components. Especially in the case of pumps or hydraulic valves, even small foreign substances can lead to major accidents if they enter the equipment, and such equipment accidents can be a potential cause of major disasters, leading to accidents involving workers operating the equipment in the vicinity. Therefore, it is a process that shipyard customers, who are shipowners, also focus on and manage very intensively. To solve these problems, this study developed a system that can increase the cleaning effect of the cleaning fluid inside the pipes by increasing the flow of the cleaning fluid inside the pipes in the existing pipe cleaning method.