Controlling of the friction in lubricated systems through Multi-Scale texturing with laser interference texturing and micro coining

点击翻译按钮获取中文摘要

A tailored surface pattern can reduce friction and wear in lubricated machine parts and thus lead to increased efficiency and service life and reduced lubricant consumption. The shape, size and spacing of such a structure are specific to each tribological system, hindering any generalised statement as to optimal parameters.In the first funding period structures were produced on flat surfaces by means of laser interference, micro-embossing and a combination thereof (multiscale structuring) and characterised with a lab tribometer. The investigations show that under hydrodynamic or mixed lubrication, laser-textured surfaces with a cross pattern increase the lubrication film lifespan and reduce wear, as do hemispheric embossed structures in boundary or mixed lubrication regime.In addition to tribocontacts, surface structures can also be used outside of the contact, to carry lubricant to the contact zone or to prevent it from leaving the contact. For applications with high pressures the fine structures would thus be protected and deficient lubrication could be avoided. Preliminary studies showed that such textures (especially multiscale) specifically affect the wetting and spreading behaviour and allow the control of passive lubricant transport.Taking into account the preliminary investigations, the objectives of the research proposal can be defined as:1. Transference of the acquired knowledge and the proven enhancements in planar surfaces concerning the use of multiscale structures to an application with curved cylindrical surfaces (i.e. plain bearings).2. Investigation of the influence of surface structures (laser, embossed and multiscale) on the passive transport of lubricant as a result of surface topography, as a function of a temperature gradient, as well as the application of the findings (i.e. rolling-element bearings).In this sense, test set-ups to structure cylindrical surfaces will be designed and tested. Simulations will be performed to interpret and analyse of the forming process. The surface of the prepared samples, i.e. the shaft sleeve of a plain bearing, will be topographically (shape and roughness) and microstructurally (SEM, EBSD, TEM) characterised. The tribological examination of the samples will be under a service contract at the IME at Aachen University (RWTH).For the investigation of the passive lubricant transport, simulations and basic experiments will be conducted on flat textured surfaces to validate the model and determine a shortlist of structures. Promising structures will then be applied to a machine element and tribologically examined.