Experimental investigation on Stribeck curves of different elastic modulus materials under oil and water lubrication conditions

Abstract

Purpose The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions. Design/methodology/approach Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system. Findings In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered. Originality/value The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

Surface topography effect on tribological performance of water-lubricated journal bearing under mixed-EHL regime

“…As a result, severe asperity-to-asperity contact occurs. Other important factors which may cause WLSTB to operate in mixed-EHL regime are improper bearing radial clearance, sea wave effect, misaligned propeller shaft, dynamic forces, etc, [6][7][8][9].…”

“…Various tribological aspects of water-lubricated rubber bearings such as (a) lubrication mechanisms [10] (b) lubrication regimes transition [11][12][13] (c) optimum design of journal bearing [14,15] (d) dynamic characteristics [16] (e) turbulence and misalignment effect [17,18] (f) local wear [19], have been explored by researchers on both numerical and experimental levels [7][8][9][10][11][12][13][14][15][16][17][18][19]. An emphasis is provided on the literature related to mixed-EHL analysis of WLSTB considering different surface topography of bushing liner and journal surfaces.…”