Experimental investigation of EHD grease lubrication in finite line contacts

Abstract

Abstract:The objective of this study was to investigate the grease-lubricated film-forming mechanisms in the finite line contact and to improve the grease-lubricated finite line contact's film-forming capacity. An elastohydrodynamic lubrication (EHL) test rig with two interferometry microscopes, which could simultaneously monitor two different contact locations in the finite line contact, was constructed in order to study the influences of the grease thickener formulation on the film thickness and lubrication condition. By using the relative light intensity method, the thickness maps of the grease-lubricated film were calculated from the interferometer images captured by the two microscopes. The test results revealed that the grease thickener's formulation had remarkable effects on film formation and the perturbation of film thickness. For the lithium-based grease, the film's thickness near the two ends of the roller was prone to severe perturbation caused by the conglomeration of clumps that were hard to shear. For the aluminum-complex-based grease, the fibers tended to accumulate in the middle of the roller rather than at the two ends. The urea-based grease could be easily sheared into smaller particles. In addition to the straight-line profile rollers, the logarithmic profile rollers were tested and found to effectively enhance the axial grease flow, increase the axial shear stress, and thus shear more fibers into particles within the contact area.

Grease film evolution in rolling elastohydrodynamic lubrication contacts

“…4(b), Fig. 7(b), and previous observations [8,[22][23][24]51]. The breakdown of lumps from their intact state to small particles contributes to the transition from distorted contact to normal contact, as shown in Fig.…”

A review of recent advances in tribology

“…The results showed that in the oil starvation condition, lubricant molecules rearrange to form an ordered layer and a thicker critical film. Wang et al [107] by using the relative light intensity method [76], obtained the thickness maps of the grease-lubricated films from the interferometer images captured by the two microscopes. Their test results revealed that the grease thickener's formulation had remarkable effects on film formation and the perturbation of film thickness.…”

Determination of the dynamic hardness of greases as a characteristic of deformation properties in a tribocontact

“…The dependence of the structure and properties of the polymer greases on the concentration of lithium stearate was established. Also, the scientific works of the authors [9][10][11][12] are devoted to various aspects of the use of greases in technical applications. At the same time, the analysis of studies has shown that little attention has been paid to the study of the deformation properties of greases under various conditions of tribological contact.…”