On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness

A new model was developed for the simulation of the friction coefficient in lubricated sliding line contacts. A half-space-based contact algorithm was linked with a numerical elasto-hydrodynamic lubrication solver using the load-sharing concept. The model was compared with an existing asperity-based friction model for a set of theoretical simulations. Depending on the load and surface roughness, the difference in friction varied up to 32 %. The numerical lubrication model makes it possible to also calculate lightly loaded contacts and can easily be extended to solve transient problems. Experimental validation was performed by measuring the friction coefficient as a function of sliding velocity for the stationary case

A stable heavier group 14 analogue of vinylidene

Vinylidene (H2C=C) is a member of the family of compounds of composition CH (and isomeric with ethyne, HC≡CH), but it has been observed only transiently—with a lifetime in the region of 0.1 ns. Indeed, no simple (non-base-stabilized) compounds of the type R2E=E have been characterized structurally for any of the group 14 elements. Here we show that by employing the bulky and strongly electron-donating boryl ligand (HCDippN)2B (Dipp, 2,6-iPr2C6H3), a simple monomeric digermavinylidene compound, (boryl)2GeGe, can be synthesized and is stable at room temperature. Both its formation via the two-electron chemical oxidation of the symmetrical Ge0 compound K2[(boryl)GeGe(boryl)] and its subsequent reaction chemistry (for example, with H2), are consistent with a high substituent lability and the accessibility of both 1,1- and 1,2-substitution patterns. Structural and computational studies of [(HCDippN)2B]2GeGe reveal a weak Ge–Ge double bond—the π component of which contributes to the highest occupied molecular orbital (HOMO)—with a Ge-centred lone pair as the HOMO–1