Entwicklung einer Untersuchungsmethodik zur Evaluierung des Fretting-Widerstandes

Research output: ThesisDiploma Thesis

Abstract

Fretting is a complex process, which in general is governed by the interaction of two bodies in contact under high surface pressure, and a third these two local separating body. The two bodies are moved by a small relative oscillating motion. Fretting is also known by the terms fretting wear, fretting fatigue and fretting corrosion. The characteristic difference between fretting and pure wear is the microscopic relative motion between the two bodies. During the fretting process a third body is formed, due to the degradation of the surfaces of the two contact partners. This debris are transformed due to chemical reaction with the surrounding media. The degradation process weakens the surface and leads to the formation of cracks. The weak surface and the existing cracks can cause failure of a component. For evaluation of the fretting process, fretting wear tests with a self designed rig have been performed on steel specimens. Therefore two pads are pressed with a defined normal force symmetrically against the specimen, which is moving at microscopic amplitude. The condition in the contact zone is changing during the fretting process. This change of condition could be characterized by hysteresis. The area inside the hysteresis is a parameter for the dissipated energy during one cycle. The bigger the area inside a hysteresis, the more energy is dissipated. After the tests, damage analysis has been performed. The amount of degraded surface during the test was measured to draw significant fretting wear diagrams. They make it possible to predict the resistance against fretting under defined parameters. The whole rig has been modelled in a FE-Simulation, to compute the stress state in the fretting zone. The damaged surface of the specimen has been scanned with a laser confocal microscope, to get the amount of worn surface volume. To get an indicator for the resistance against fretting, the energy wear rate has been implemented. This energy wear rate is the ratio between the worn volume of the surface and the dissipated energy calculated out of the hysteresis. The less surface is worn per dissipated energy, the higher is the resistance against fretting.

Details

Translated title of the contributionDevelopment of a methodic aprroach for evaluation of fretting resistance
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
Award date19 Dec 2008
Publication statusPublished - 2008