Modelling the surface topography of tribologically stressed surfaces generated by milling and microfinishing processes

Petra Wiederkehr, Institute of Machining Technology, TU Dortmund University, Dortmund, Germany
Sascha Rausch, Institute of Machining Technolog, TU Dortmund University, Dortmund, Germany
Sebastian Goeke, Institute of Machining Technology, TU Dortmund University, Dortmund, Germany
Dirk Biermann, Institute of Machining Technology, TU Dortmund University, Dortmund, Germany

The lifetime of tribologically stressed surfaces, in particular the wear rate during the running-in phase, can be improved significantly by structured surface topographies of both tribological partners. A promising machining technology for generating such surface topographies is the microfinishing process. By adjusting the design of the microfinishing process, surfaces with a plateau-like topography characterized by a high value of the reduced valley depth Rvk and a low value of the reduced peak height Rpk as well as surfaces with low Rvk and Rpk values can be achieved. In addition, previous machining operations, e.g. milling and grinding processes, can be used for generating a surface structure and influencing the surface integrity.

Analysing the tribological behaviour of milled and micro-finished surfaces in linear-oscillating wear tests, surfaces generated by milling and subsequent finishing operations showed the lowest wear rates. For a further improvement of the tribological behaviour, the resulting surface topography from the process chain milling and microfinishing has to be analysed in more detail. A suitable solution to reduce the experimental effort is the modelling and simulation of the machining process.

In order to accomplish this, a geometric physically-based simulation was developed at the Institute of Machining Technology (ISF) at TU Dortmund University, which enables the subsequent simulation of milling and micro-finishing processes. In this simulation system the specific engagement situation between the tool and the workpiece geometry is determined for an appropriate time and space discretization of the milling process. As a result, the surface topography can be modelled for milling processes taking the resulting process forces and dynamics into account. Based on digitized finishing tools, the process parameter values can be adjusted in order to achieve topographies that provide suitable characteristics for surfaces in tribological contact. Based on the initial surface topography and surface integrity, optimized process parameter values for the microfinishing process can be determined.

In this contribution, first results of the subsequent simulation of milling and microfinishing processes are presented. For the validation of the simulation results, the surface topographies are compared to those generated in real machining processes.

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