First Traction Results of High Spinning Large-Size Circular EHD Contacts from a New Test Rig: Tribogyr

Abstract

This article presents a new test rig named Tribogyr and the first results obtained so far. This device allows EHL friction tests in rolling-sliding under high spinning conditions applied to large-size circular contacts. Spinning is imposed thanks to a unique design that includes a tilting facility of one of the two spindles. After a brief description of the test rig structure and of the specimen geometry, the sensor's implementation and the device capabilities are reported. The parameter used to quantify the spin in this study is then defined. It only takes into account the rotational speed normal to the contact surface and the contact radius. Then, the friction coefficient and the temperature measurements are presented. The data are at first plotted versus the classical slide-to-roll ratio and compared to numerical results obtained with and without spin. The spin parameter then is introduced to replace the slide-to-roll ratio as the varying parameter. This representation allows reporting all the results in the same figure, where the influence of the operating conditions like the entrainment speed, the tilting angle, and the slide-to-roll ratio on friction and on temperature is much more visible. It is discussed that the observed temperature difference increase is generated by an additional shearing introduced by spinning despite an observed reduction of friction.

Numerical insight into heat transfer and power losses in spinning EHD non-Newtonian point contacts

“…A closer look inside the contact (possible with the help of numerical investigation only) allowed to explain this effect [14]: with the addition of spin, a part of the contact area sees its longitudinal stresses becoming negative; the integration of these stresses leads to lower longitudinal friction than in a no-spin case. Comparison of this study with numerical and experimental friction data found in the literature [14,26] is presented in Fig. 9.…”

“…The friction coefficient (Cf x ) is represented as a function of the longitudinal slide-to-rolling ratio (equation (2)). The same kinematic conditions as Dormois et al [14] is simulated here: both experimental conditions and relevant numerical parameters can be found in references [14] and [26]: l ¼ 2 , U m,x,0 ¼ 2 m/s, U m,y,0 ¼ 0 m/s, p H ¼ 845 MPa, a ¼ 0.92 mm, and 2 varies between 680 and 840 rad/s to achieve the corresponding longitudinal slide-to-rolling ratio (SRR x,0 ). Although the same lubricant was investigated, Dormois et al used an isothermal Roelands Dowson-Higginson viscosity density model as well as a Ree-Eyring behaviour for the friction calculation.…”

Effects of spinning on the mixed thermal elastohydrodynamic lubrication and fatigue life in point contacts

“…In the present study, " h is selected as 10 nm. 19,20 Equation 7can be considered as a special form of equation (2). At the boundary between the hydrodynamic lubrication and asperity contact regions, the pressure is consistent.…”

“…By introducing an effective viscosity * into equation (2), the non-Newtonian properties of lubricant can be considered. The sinh-law model 21,22 is used, and the effective viscosity * can be expressed as…”

“…It is important to understand the mechanism of lubrication in the presence of spinning because previous experimental researches have shown that the spinning is responsible for the reduction of transmission efficiency and lubrication failure. [1][2][3] However, relatively few numerical researches about the effects of spinning on TEHL have been presented.…”