Characterisation of multifunctional surfaces with robust filters

Research has shown that engineered surfaces containing lubrication pockets and directional surface texture can decrease wear and friction in sliding or rolling contacts. A new generation of multifunctional (MUFU) surfaces is achieved by hard machining followed by robot assisted polishing (RAP). The novel production method allows for a large degree of freedom in specifying surface characteristics such as frequency, depth and volume of the lubricant retention valleys, as well as the amount of load bearing area and the surface roughness. The surfaces cannot readily be characterized by means of conventional roughness parameters due to the multi-process production method involved. A series of MUFU surfaces were characterized by using the ISO 13565 standard for stratified surfaces and it is shown that the standard in some cases is inadequate for characterisation of a MUFU surface. To improve the filtering of MUFU surfaces the robust Gaussian regression filtering technique described in ISO 16610-31 is analysed and discussed. It is shown how the robust Gaussian regression filter can be used to remove the form and find a suitable reference surface for further characterisation of the MUFU surfaces.