Flattening of Pyramidal Asperities Under Combined Normal Loading and In-Plane Biaxial Straining

Maximilian Zwicker, Ulfar Arinbjarnar, Maximilian Knoll, Niels Bay, Chris V. Nielsen*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


In metal forming processes, contact mechanics in the tool-workpiece interfaces determine the resulting friction and thus influence the quality and stability of the process. In models representing dry, thin film and boundary lubrication
conditions in metal forming, friction may be assumed proportional to the ratio of the real contact area to the apparent contact area. It is therefore important to obtain a fundamental understanding of as many of factors influencing asperity
flattening as possible. This paper presents asperity flattening of pyramidal model asperities loaded normally by a plane tool. The experiments are performed in a recently developed test setup, which allows for different in-plane strain ratios in
combination with the normal load. The in-plane deformation is known, through the yield criterion, to influence the necessary yield pressure to flatten the asperities and hence the resulting real contact area. In-plane balanced biaxial stretching is
shown to result in further asperity flattening than plane strain. When comparing to previous results, it is shown that in-plane strains reduce the effect of the asperity shape on the resulting real contact area ratio.
Original languageEnglish
Title of host publicationProceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity (ICTP 2023)
EditorsK. Mocellin, PO. Bouchard, R. Bigot, T. Balan
Place of PublicationCham
Publication date2023
ISBN (Print)978-3-031-40919-6
ISBN (Electronic)978-3-031-40920-2
Publication statusPublished - 2023
EventInternational Conference on the Technology of Plasticity - Mandelieu-La, France
Duration: 24 Sept 202329 Sept 2023


ConferenceInternational Conference on the Technology of Plasticity
SeriesLecture Notes in Mechanical Engineering


  • Sheet metal forming
  • Friction
  • Asperity flattening
  • Pyramidal asperities


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