Soft Elastohydrodynamic Analysis of Radial Lip Seals With Deterministic Microasperities on the Shaft

Abstract

A numerical analysis is conducted to investigate the elastohydrodynamic effect of deterministic microasperities on the shaft of a lip seal. Various geometries of microasperities (triangular, square, hexagonal, and circular) are put into a 100×100μm2 unit cell and are investigated using Reynolds equation. For each shape, the area fraction of the microasperity is varied between 0.2 and 0.8, and the asperity height is varied between 0.3μm and 5μm. The calculation for load capacity and friction coefficient indicates that there are values for asperity height, where the load capacity and friction coefficient are optimized. These optimum heights were reached at 1–3μm. Although the lip seal surface is considered to be smooth, reverse pumping can still be obtained using an oriented triangular design. The Couette flow rate for this asperity showed lubricant is reverted back toward the seal side 2.6 times more than using a conventional lip seal. The addition of microasperities to the shaft surface shows significant improvement in lubrication characteristics for the lip seal in the form of a simultaneous reduction in friction coefficient and increase in the reverse pumping rate.

Grease Lubrication Mechanisms in Bearing Seals

“…Nowadays, it is believed that both the seal and shaft roughness are important. Numerical models support this hypothesis, such as those by Gabelli and Poll [14], Shen and Salant [41], Hajjam and Bonneau [17]. Horve [22] has shown that a high seal roughness and a shaft roughness of 0.25-0.5 Ra are critical for long seal life and good sealing performance.…”

“…Horve [22] showed that high shaft surface roughness increases wear of the rubber lip. A shaft with engineered surface asperities, as suggested by Hadinata and Stephens [41], is extremely rough and may cause very high wear rates of the seal, especially when operating in the mixed lubrication regime during start/stop and low speeds.…”

“…Gabelli and Poll [14] modelled the lubricant film formation between two parallel rough surfaces using Reynolds equation and finite difference techniques. Later, Shi and Salant [41] used a more realistic quasi-random surface roughness geometry for their simulations. Hajjam and Bonneau [17] studied the influence of different mathematical roughness models on performance features like film thickness, power loss, pumping rate and lip temperature.…”

“…However, recently, the bearings and seals laboratory at the University of Kentucky has developed a manufacturing technique based on X-ray lithography and UV photolithography to fabricate these engineered surface textures. Hadinata and Stephens [41] conducted a numerical analysis to investigate the elastohydrodynamic effect of various geometries of microasperities. They used the Reynolds equation to calculate the load capacity, friction, and pumping of triangular, square, hexagonal, and circular microasperity geometries.…”

Frictional effect of spherical convex textured rigid bodies sliding on smooth PDMS

“…On the aspect of theory, Shinkarenko et al [7] obtained the pressure distribution in the fluid film and the elastic deformation of the elastomer by establishing and solving the theoretical model, which provided the best parameters for the design of the surface texture. Hadinata et al [8] conducted a numerical analysis to study the effect of deterministic microasperities on the elastohydrodynamic performance of lip seal. The micropores on the shaft surface show a significant decrease in friction and an increase in reverse pumping rate.…”