Entwicklung einer Versuchsmethodik zur Untersuchung von Frettingbeanspruchung

Translated title of the contribution: Design of a test methodology to examine fretting damage

Bernd Strohhäussl

Research output: ThesisDiploma Thesis

Abstract

The term “Fretting” covers a process of high complexity, which is basically designated to a small oscillating relative movement between two bodies in contact. Fretting results in different types of damage mechanisms and may cause a significant reduction in durability, therefore representing a serious problem in modern machinery design. The major part of research in this field has been conducted on Hertzian contacts, due to the immense knowledge about the mechanical behaviour and contact mechanics. The knowledge base concerning the damage behaviour of large area contacts exhibiting micro-displacements is not that distinctive. As they represent a major part of applications in mechanical engineering, there is a rising need to investigate these types of contacts in detail. Keeping this in view, an electromotive direct drive actuated test rig with specially suited load unit, which enables investigations on the fretting behaviour of large scale contacts, was designed in this thesis. Due to the special requirements of the fretting tests, a closed-loop position control was adapted. By means of modifying the PI-controller and superimposing a process-dependent feed-forward-value, the linear drive can be used both for micro- and macro displacements. The methodology to achieve tribologically reproducible test results and accordingly a damage equivalent evaluation procedure was build up by fretting tests on the re-designed linear drive, and an established fretting test rig mounted on a displacement controlled servo-hydraulic tester. A comparative study was done by macro- and microscopic fracture surface inspection. With similar setup parameters and test-cycles, significant changes in local damage evolution were observed. Differences in stiffness of the specific test rigs and local distribution of forces during one load cycle lead to an increased local fretting damage in case of the hydraulic test cell. The linear drive unit led to fretting damages, which are closer to those observed in real parts. The achieved large-scale contact pattern and the beneficial reproducibility of the fretting damage forms the basis for detailed damage characterization, study of the effect of coatings and tribological surface modifications in future work, using the re-designed electromotive linear drive test rig.
Translated title of the contributionDesign of a test methodology to examine fretting damage
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Godor, Istvan, Co-Supervisor (internal)
  • Eichlseder, Wilfried, Supervisor (internal)
Award date16 Dec 2011
Publication statusPublished - 2011

Bibliographical note

embargoed until 29-09-2016

Keywords

  • tribology
  • fretting
  • testrig
  • tribometry
  • electromotive direct drive

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