Fretting wear mapping: the influence of contact geometry and frequency on debris formation and ejection for a steel-on-steel pair

Abstract

This paper examines the influence of contact geometry and oscillation frequency in a steel cylinder-on-steel flat fretting contact, with contact geometry being varied via the cylinder radius. Fretting frequency did not significantly impact the wear behaviour for more-conforming contacts, but did so for less-conforming contacts where, at high frequency, the wear rate is approximately 50% of that observed for low-frequency fretting. It is proposed that frequency and contact conformity fundamentally control wear behaviour through influence of both the debris type and the retention or ejection of that debris from the contact. The debris type (either oxide or metallic) is influenced by fretting frequency (which controls the interval between asperity contacts) and by contact conformity (which controls the distance that oxygen has to travel to fully penetrate the contact). Debris retention within the contact is promoted by higher fretting frequencies (the associated higher contact temperature promotes debris agglomeration and sintering in the contact) and by higher contact conformity (which acts as a physical barrier to debris egress). Maps are presented which categorize the observed behaviour and outline a phenomenological framework by which the basic physical processes which influence fretting behaviour can be understood.

The role of geometry changes and debris formation associated with wear on the temperature field in fretting contacts

“…As the fretting frequency increases, the temperature within the contact will also increase, and it is argued that this will affect the debris formation and debris retention within the contact by mechanisms similar to those proposed when the role of ambient temperature has been considered. Indeed, a general reduction in wear rate has been found with increasing fretting frequency in previous studies [12][13][14].…”

Derivation of a wear scar geometry-independent coefficient of friction from fretting loops exhibiting non-Coulomb frictional behaviour

“…Most significantly, an improved method for deriving the geometry-independent CoF from a gross-slip fretting loop will be proposed. Figure 2 Cylinder-on-flat specimen arrangement employed in fretting tests [14] (a) (b) Many experimental researchers into fretting utilise con-conforming contact geometry, typically a sphere-on-flat or a cylinder-on-flat geometry. At the University of Nottingham, the bulk of our work has utilised the latter, often with a 6 mm radius cylinder.…”

“…At the University of Nottingham, the bulk of our work has utilised the latter, often with a 6 mm radius cylinder. Specimens are assembled in a cylinder-onflat arrangement ( Figure 2) which generates a line contact ( ) of 10 mm in length (see the work of Warmuth et al for a detailed description of the test apparatus [14]). A normal load, P, is applied to the upper (moving) specimen through a dead-weight with the fretting motion being applied perpendicular to the axis of the cylindrical specimen.…”

A combined wear-fatigue design methodology for fretting in the pressure armour layer of flexible marine risers

“…A two-dimensional critical-plane implementation of the SWT parameter, which has previously been validated for fretting fatigue by the authors [11] based on the previous work of Leen and co-workers [4,21], is incorporated. This is a combined stress and strain transformation (covering 360° in 5° increments) process, applied to the FE models of the pressure armour layer, to identify the critical plane value and orientation from the history of cyclic multiaxial stresses and strains on each candidate plane.…”

“…In this work, three-dimensional topography of the wear scars was measured using a Bruker Contour GT-I interferometer. The wear volume, V, was calculated as the volume of material removed from the reference surface, as described in [21]. This provided data to calculate the Archard wear coefficient using the equation:…”