Tribometric assessment towards functionality of current and future journal bearing systems

Florian Summer

Research output: ThesisDoctoral Thesis


Journal bearings are essential components of modern internal combustion engines. These tribological systems are constantly subjected to changes in design and performance as the engine itself. In particular, the current engine developments in terms of efficiency and exhaust emission limits cause perforce changes of well-functioning engine components. Simultaneously, reduction of engine power is not accepted, which increases the engine power densities. All these actions push journal bearing systems beyond their limits of efficiency and function. Accordingly, taking into account the new conditions, a material-specific redesign of the three main components of journal bearing systems – viz. the bearing material, the lubricant and the shaft material – is required. This problem is the subject of investigations of this dissertation thesis. The framework of this thesis is based on a systematic study of the functioning of journal bearings under boundary and mixed friction conditions. Based on currently used bearing materials, lubricants and shaft materials research work has been carried out in particular on possible future solutions for all beforehand listed components. In this regard research activities have focused on the investigations of start stop wear and emergency running properties of journal bearings, as well as the on the investigations of chemical interactions between surfaces and lubricants. The latter has been studied only sparingly in the past. The future-oriented tasks have been processed using model and component test configurations supported by spatially resolving analytics. The findings of the study show that a synergetic design of bearing material, lubricant and shaft material has a positive impact on the sliding performance of journal bearing systems in boundary and mixed friction conditions. Especially the performances of the tested metallic bearing materials can be boosted with the aid of protective components of the lubricant chemistries, whereas the tested polymer based bearing overlay operates well independently of currently used additive technologies. Changes in the lubricant chemistry to comply with emission limit reductions from EURO III to EURO VI resulted in a seizure load limit decrease of 40-55 % for the tested metallic bearings. Examinations with regard to reductions of the lubricant viscosity resulted overall in an increase of the failure risks of the tested bearing systems. Furthermore, the results include the tribological characterization of novel bearing materials, experimental lubricant formulations and the effect of the shaft topography conditions.
Translated title of the contributionTribometrische Bewertung der Funktionalität von gegenwärtigen und zukünftigen Gleitlagersystemen
Original languageEnglish
  • Ebner, Reinhold, Assessor B (internal)
  • Grün, Florian, Assessor A (internal)
Publication statusPublished - 2016

Bibliographical note

embargoed until null


  • Tribology
  • Journal bearings
  • Start stop wear
  • Seizure resistance
  • Additive interactions
  • Effect of shaft surface conditions
  • Novel lead free bearing materials
  • Viscosity decrease
  • Effect of antiwear affitives
  • Change in lubricant formulation
  • New additives

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