Despite a large amount of work dedicated to the study of the effects of textured surfaces in tribological pairs, there is still a need for accurate and convincing experimental results to prove the benefi c effects predicted theoretically. This paper presents an original experimental set-up with a partially textured fl at pin sliding on a rotating disc in the presence of a thin lubricating fi lm of constant thickness. The texture was composed of a series of parallel grooves cut on the half of the pin front face. The main objective of the reported work was the experimental assessment of hydrodynamic performances (load capacity and friction force) for parallel, partially textured sliders and the comparison with a similar step slider. Preliminary results have clearly put in evidence the collective hydrodynamic effect of partially textured surfaces. The stepped confi guration has shown greater load capacity with respect to textured confi guration. Copyright
The process of liquid flow takes place inside a highly compressible porous layer (HCPL) many times. In these cases, elastic forces of the HCPL solid phase are negligible, compared with hydrodynamic (HD) forces. Such processes were named ex-poro-HD (XPHD). A study of the impact process under XPHD conditions for circular and rectangular aligned plates was recently performed and presented by the authors. The impact of a rigid sphere on an HCPL, imbibed with a Newtonian liquid, under XPHD conditions, is analysed in the present paper. The Kozeny—Carman equation was used to compute the permeability variation as a function of compacticity/porosity. The Bowden and Tabor model for squeeze under impact was extended for XPHD conditions. The obtained model gives the impact pressure and force variations as the layer thickness decreases, so the damping capacity of the HCPL was evaluated. The maximum value of the absorbed energy, given by the optimal compacticity/porosity of the HCPL, is established. A comparison with the impact of a rigid sphere on a Newtonian liquid film under HD conditions is also done, keeping the same geometry and same kinematic and dynamic parameters, inherited from the XPHD model. The damping capacity of an HCPL is several orders of magnitude greater than that of the Newtonian liquid layer. The theoretical model was validated by two experiments, in which the HCPL is impacted by free falling ball tests.
The objective of this article is the study of the load-carrying capacity of a Rayleigh step slider (RSS) for both direct motion (þRSS -which generates lifting effects) and reverse motion (ÀRSS -which generates suction or cavitational effects). Normal force was measured on a pinon-disc test rig, with two lubricants (SAE-20 W-50 oil and glycerin) at four speeds and three values of film thickness. During reverse motion (ÀRSS), cavitational effects have been observed for some test cases. It is supposed that surface tension influences the appearance of cavitational effects, and a modified capillary number, Ca þ , is proposed as indicator of cavitation inception. Close-up views taken near the trailing edge of the pin show the occurrence of several streamers, typical for cavitational effects, only when Ca þ 4 2. Numerical simulation as well as approximate analytical models are presented for both directions of motion. The comparison of predicted theoretical results with the experimental data is satisfactory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.