“…These regimes are characterized by the coexistence of hydrodynamic and asperity contact pressure where the latter is generally responsible for increased frictional losses, wear and a higher chance of failure. On the one hand, these circumstances demand a continuous further development of the tribological partners shaft and journal bearing material as well as the lubricant by experimental investigations [2][3][4][5][6][7][8][9]. On the other hand, the prediction of wear based on numerical investigations becomes increasingly important especially in the course of the design process and the evaluation of life expectancy [10,11].…”
Hydrodynamic journal bearings are subjected to progressively rough loading conditions leading to an increased share of operation in mixed and boundary lubrication. This results in increased frictional losses, additional wear and a higher chance of failure, which calls for the understanding of wear processes and the necessity of a numerical assessment. We conducted wear investigations of journal bearings by making use of a close-to-component test setting, and the progress of wear could be linked to the introduced frictional energy and in combination with a comprehensive surface analysis tribological effects could be resolved in detail. Achieved wear coefficients were implemented in a novelly developed numerical framework, which allows for the dynamic numerical evaluation of operation in the fluid and mixed lubrication regime and simultaneously occurring wear processes. By comparing numerical and experimental results, we evaluated the numerical framework's capability to conduct holistic simulations including aspects like dynamically changing operation conditions, fluid and mixed lubrication as well as wear.
“…These regimes are characterized by the coexistence of hydrodynamic and asperity contact pressure where the latter is generally responsible for increased frictional losses, wear and a higher chance of failure. On the one hand, these circumstances demand a continuous further development of the tribological partners shaft and journal bearing material as well as the lubricant by experimental investigations [2][3][4][5][6][7][8][9]. On the other hand, the prediction of wear based on numerical investigations becomes increasingly important especially in the course of the design process and the evaluation of life expectancy [10,11].…”
Hydrodynamic journal bearings are subjected to progressively rough loading conditions leading to an increased share of operation in mixed and boundary lubrication. This results in increased frictional losses, additional wear and a higher chance of failure, which calls for the understanding of wear processes and the necessity of a numerical assessment. We conducted wear investigations of journal bearings by making use of a close-to-component test setting, and the progress of wear could be linked to the introduced frictional energy and in combination with a comprehensive surface analysis tribological effects could be resolved in detail. Achieved wear coefficients were implemented in a novelly developed numerical framework, which allows for the dynamic numerical evaluation of operation in the fluid and mixed lubrication regime and simultaneously occurring wear processes. By comparing numerical and experimental results, we evaluated the numerical framework's capability to conduct holistic simulations including aspects like dynamically changing operation conditions, fluid and mixed lubrication as well as wear.
“…The results of these characterizations have been also reported in a previous work. 14 Figure 1.Example of EJB and steel ball samples used for the wear tests.…”
Section: Methodsmentioning
confidence: 99%
“…The conditions were also selected to achieve boundary lubrication regime at the starting test condition. It was determined by the Lambda ratio values, ʌ, obtained by using the calculations given in Farfán-Cabrera and Gallardo-Hernández 14 and based on Hamrock et al. 1 for a ball-on-concave flat lubricated sliding contact.…”
Ideally, engine journal bearings are expected to operate under hydrodynamic lubrication regime to limit wear and promote minimal friction by sliding. Nevertheless, engine journal bearings fail since wear caused by severe conditions in actual engine operation, such as start/stop, misalignment, lubricant degradation, overheating, and debris contamination, producing a transition from hydrodynamic to mixed and boundary lubrication regimes and wear increased in both engine journal bearings and crankshaft. Thus, this work aims to study the influence of boundary lubrication, engine mineral oil aging, and debris contamination on wear of engine journal bearings. An adapted microscale abrasion tester using a ball-on-concave flat configuration was used to reproduce boundary lubrication under controlled conditions. Steel balls having a similar surface than crankshafts and concave flat samples cut from actual engine journal bearings were tested. The tests were run under boundary lubrication at a constant load, speed, and sliding distance at 26 ℃ and 100 ℃ using separately clean fresh and aged engine mineral oil, and then, tests were conducted using the oils contaminated with hard abrasive particles. The engine mineral oil was degraded by a laboratory aging process approaching oxidation of an engine mineral oil used in actual use conditions. Oxidation, additives depletion and changes in viscosity were evaluated. The wear volumes and scar morphologies of engine journal bearing samples were analyzed. The results suggested that high temperature was the main contributor for wear increase in engine journal bearings, while oil aging and debris did not influence considerably on the wear. However, the oils contaminated with hard particles produced a wear decrease in engine journal bearing samples but increased wear in rotary balls.
“…These test stands are successfully used in predicting hydrodynamic load bearing capabilities and wear-fatigue phenomena [8]. However, several studies point out the limited measurement and control accuracy of these rigs for certain investigation topics owing to complex rig assemblies [9,10].…”
Section: Introductionmentioning
confidence: 99%
“…In this regard, tribological model scale set ups including micro abrasion testers [10], scratch tests [11], or pin-on-disc systems [12] are compromisingly carried out to gain a better understanding about the basic tribological phenomena of sliding surfaces. However, it is also emphasized in literature that various basic model test configurations, such as pin-on-plate, fail to reproduce damage mechanisms and tribological functionality of journal bearing applications, such as shown in [13].…”
Abstract:The current paper addresses the field of experimental research of journal bearing systems. In this regard, the challenges are dealt with concerning simultaneous testing with a close correlation to the industrial application and with a high resolution of tribological processes. Concerning this aspect, two damage equivalent laboratory test methodologies for journal slide bearing systems are presented, and their ability to visualize certain performance parameters of bearing systems are emphasized (for instance friction performance, (start stop) wear processes, and seizure events). The results clearly emphasize that the applied methodologies provide accurate findings regarding specific effects of selective parameters/changes on the performance of bearing systems, such as polymer overlays may result in improved mixed friction sliding conditions if designed properly, and they provide superior start stop wear resistance; the use of specific corrosion inhibitors can successfully prevent tribo-corrosion on bronze bearings; a decrease of oil viscosity increases solid friction share but decreases fluid friction; lubricant anti-wear additives are able to improve seizure resistance and sliding properties of bearing systems depending on formulation harmonization; and novel bearing material coatings, e.g., sputtered SnCu, can significantly improve emergency running capabilities.
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