Although fretting involves only micrometre-scale motion, it can cause unexpected wear and cracking, ultimately leading to costly and premature failure of critical components. The research focused on understanding how friction, wear, and cracking develop in heavily loaded contacts under conditions relevant to industrial machinery.
Amirhossein Zabihi conducted his doctoral dissertation at the Doctoral School of Industry Innovations (DSII) of Tampere University in collaboration with Wärtsilä.
In his dissertation, the experimental work was carried out using a specially designed test setup that reproduces large, flat-on-flat interfaces representative of those found in industrial machinery assemblies, in contrast to small-scale laboratory contacts. By systematically varying surface texture and imposed displacement amplitude under dry and oil-lubricated conditions, the study showed that surface texturing and oil lubrication can reduce friction and delay damage development. Moreover, the results identified threshold levels of imposed displacement amplitude below which a stable frictional regime is maintained, avoiding the initial adhesive friction peak that promotes crack initiation and accelerated fretting damage.
Detailed microscopic and cross-sectional analyses revealed how localized adhesive contact regions form on the surfaces and how these regions can eventually crack under repeated loading. The research showed how subsurface damage layers develop beneath the contact and influence crack initiation and wear-debris formation over time. In addition, the work elucidated how different fretting regimes emerge as operating conditions change—an important insight, as fretting damage often develops unnoticed until failure occurs.
The findings provide new insights into fretting damage mechanisms and practical guidance for improving the durability and reliability of steel components in heavy-duty industrial assemblies involving flat-on-flat, normally loaded contact interfaces. By helping engineers better control friction and damage at critical interfaces, the research supports longer component lifetimes, reduced maintenance needs, and improved operational safety. The outcomes are particularly valuable for manufacturers and designers of mechanical systems where fretting-induced degradation limits reliability and service life.
Public defence on Thursday 8 January
The doctoral dissertation of MSc Amirhossein Zabihi in the field of Materials Science and Engineering titled Fretting-Induced Degradation of Quenched and Tempered Steel under Flat-on-Flat Contact: An Experimental and Microstructural Study of Friction, Wear, and Cracking will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University on Thursday 08 January 2026 at 13:00 in auditorium K1702, Konetalo building, Hervanta campus (Korkeakoulunkatu 6, Tampere).
The opponents will be Professor Urban Wiklund from the Uppsala University in Sweden and Professor Jens Hardell from the Luleå University of Technology in Sweden. The Custos will be Assistant Professor Janne Juoksukangas from the Faculty of Engineering and Natural Sciences, Tampere University.