Methodenentwicklung zur Bewertung von großflächigen Aluminium-Stahl-Kontakten

Translated title of the contribution: Development of methods for the assessment of large-area aluminum-steel contacts

Christoph Apfelknab

Research output: ThesisDiploma Thesis


Fretting generally represents a process, where a small oscillatory relative movement between two bodies in contact under a high surface pressure, can express itself in various forms of damage. The occurrence of this wear phenomenon can significantly reduce the lifetime of components. Therefore, it is important to carry out scientific investigations particular in large area contacts. In order to reduce time and costs, a test chain is required from component testing to model testing. For the investigation of large area contact problems, model tests were carried out on simple specimen geometries using a linear test machine. As a result, an existing test chain could be extended by a model test. A basic understanding of the test machine as well as an appropriate test methodology was developed by preliminary tests. The test results are used to determine varying test parameters for the following main tests. In the course of the main tests, the material pairing of aluminum and sintered steel was tested under the previously defined test parameters and evaluated using various evaluation methods. In addition to the observation of the measured variables recorded during the test, such as friction force and relative moving distance, the corresponding specimens were analysed gravimetrically and optically with regard to wear and corresponding evaluation variables were derived therefrom. An optimal evaluation and assessment of the performed experiments were found to be challenging due to a change in the stiffness of the linear test machine occurring during the tests. By setting up a running-condition-fretting-map, the most appropriate evaluation method was defined for the performed experiments in this work. For this, the stressed aluminum surfaces are evaluated subjectively visually with regard to the areas with a stick- and slip-zone and the respective corresponding percentages are determined. After this, the percentages of the slip-zone are assigned in the running-condition-fretting-map to the respectively applied surface pressure and oscillating distance. The result shows that a larger percentage of slip-zone is present with increasing application of the relative moving distance and with smaller surface pressures, and thus the surfaces have correspondingly greater wear damage. In addition, a hypothesis for the damage procedure of the surface could be defined by damage analysis of the tested aluminum specimens. It was found that there exists no purely adhesive wear, but rather a complex process with elastic-plastic deformations and associated fatigue-induced crack formation and crack growth proceeded from the surface into the material as well as parallel to the surface of the material in combination with adhesive wear. This damage mechanism could be proved by using metallographic sections on selected tested aluminum specimens from model testing to component testing. Numerical simulations based on the simple contact geometry of the model test were performed in parallel with the experiment. The local contact variables, such as contact pressure and relative slip, were examined in the first place. Based on this, the implementation of a methodology for the numerical simulation of the wear on the surfaces in contact was carried out. Moreover, methods were used to replicate the stick- and slip-zones that are typical for fretting. With these simulations, it is not possible to represent the complex damage mechanisms occurring in the experimental tests.
Translated title of the contributionDevelopment of methods for the assessment of large-area aluminum-steel contacts
Original languageGerman
  • Godor, Istvan, Co-Supervisor (internal)
  • Grün, Florian, Supervisor (internal)
  • Stoschka, Michael, Co-Supervisor (internal)
Award date7 Apr 2017
Publication statusPublished - 2017

Bibliographical note

embargoed until 01-10-2021


  • fretting
  • model testing
  • linear testing machine
  • large-area contact

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