Über die Bewertung von Mischreibungsprozessen und deren Einfluss auf die Lebensdauer großflächiger tribologischer Kontakte

Translated title of the contribution: On the modelling of mixed friction processes and their effects on life expectancy of large area tribological contacts

Philipp Bergmann

Research output: ThesisDoctoral Thesis


The continuous development of machines allow for an increase of their overall efficiency. Performed measures, such as downsizing, hybridization and the use of low and ultra low viscosity oils in order to reduce the frictional losses force journal bearings as essential components of these machines into operation in the mixed and boundary lubrication regime resulting in increased frictional losses and a higher risk of wear. In the course of the present work, this topical problem was dealt with in a holistic approach. On the one hand, a new measurement principle of acoustic emissions was applied and the correlation to tribological processes was investigated. For this purpose two tribological contacts (Ring-on-Disc and a reduced journal bearing system) were pushed from initially stable operation into gradual failure. During this process, the acoustic emissions were studied. On the other hand, a numerical evaluation chain with the help of MATLAB® and COMSOL Multiphysics® was developed in order to allow for the simulation of operation in fluid, boundary and mixed lubrication under arbitrary loading conditions. The numerical framework was validated with the help of literature data and conducted tests and allowed for the investigation of several aspects of modelling of mixed lubrication. For the evaluation of wear, experimental investigations were conducted and evaluated based on energetic methods. The achieved test results were utilized with the help of a reformulated Archard’s wear law and implemented in the developed numerical evaluation framework. Conducted numerical investigations were compared with experimental result. The investigations of the acoustic emissions showed a strong correlation to tribological processes, described by conventional measurement variables, such as the coefficient of friction with the onset of wear which allowed a subsequent characterisation of the two investigated systems. By a comparison between numerical and experimental results, the developed numerical framework could be validated and the simulation of mixed lubrication processes was investigated in deep detail allowing to make a significant scientific contribution. Based on the energetic evaluation of the experimental wear results, the wear behaviour of two material combinations was characterized and the universal applicability of this evaluation method was demonstrated. Conducted numerical wear investigations showed a good phenomenological correlation to experimental results.
Translated title of the contributionOn the modelling of mixed friction processes and their effects on life expectancy of large area tribological contacts
Original languageGerman
Awarding Institution
  • Montanuniversität
  • Brand, Clemens, Assessor A (internal)
  • Grün, Florian, Supervisor (internal)
Publication statusPublished - 2018

Bibliographical note

embargoed until 30-04-2023


  • Tribology
  • Friction
  • Wear
  • Simulation
  • Testing

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