Purpose
The purpose of this paper is to reveal the influence of dimples on the tribological properties of the “washers-cage-rollers” system of rolling element bearing (REB) under starved lubrication.
Design/methodology/approach
A fiber laser marking system was used to prepare dimples patterns on the raceways of the shaft washers of cylindrical roller thrust bearings (CRTBs). The friction and wear properties of dimples textured CRTBs with different diameter of dimples (200 µm, 250 µm, 300 µm) and depth of dimples (4 µm, 8 µm, 12 µm) were researched through a vertical universal wear test rig using a customized tribo-pair under starved lubrication. The surface stresses and the influence mechanism of dimple units on the tribological behavior of REBs were also compared and discussed.
Findings
Although the surface stresses on the raceways of dimples textured bearings are significantly higher than that of the smooth group, the coefficients of friction and wear losses of them are all reduced under starved lubrication. When the effective volume of dimples is between 1.13 and 2.25 and the depth of dimples is smaller than 12 µm, the tribological properties of dimples textured CRTBs are significantly improved. In this work, when the diameter of dimples is 250 µm, and the depth of dimples is 8 µm, the textured bearings can provide the excellent friction-reduction ability and outstanding wear resistance.
Originality/value
This work is a valuable reference for the raceway design and optimization of REBs.
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With the rapid advancement of sponge city infrastructure in China, the concept and construction of sponge campus have received wide attention. Implementation of a sponge campus incorporated with low impact development (LID) facilities could effectively reduce runoff and promote rainwater recycling in case of rainfall occurrence, provide resilience and improve stability against climate change for both system itself and adjacent regions. However, most of the studies on sponge campus in China are focused on the design and evaluation of college campuses, while little emphasis has been put on elementary and secondary schools where the requirement and characteristics of target users are totally different. In this paper, designing concepts regarding vertical design and application of LID for sponge campus for elementary and secondary schools were given based on engineering practice. Then a typical secondary school campus in Kunshan, China was taken as an example, and simulation was conducted on recurrence period of 1 year and 20 years using stormwater management model (SWMM). The results showed that, under the rainfall intensity with a recurrence period of 1 year and 20 years, the peak flow was reduced 46.8% and 59.0%, respectively, while the total inflow was reduced 25.4% and 33.9%, respectively. Under recurrence period of 1 year, this vertically-designed campus with LID facilities provided 15.13% water storage capacity for the neighboring plot with only 9.16% of the plot area. This new way of vertical design coupled with LID facilities can help to create a much more ecological, safe and beautiful school campus.
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