Investigation into relative slip during fretting fatigue under partial slip contact condition

Abstract

A B S T R A C T A finite element analysis based methodology was developed to compute local relative slip on contact surface from the measured global relative slip away from contact surface. A set of springs was included in finite element model to simulate fretting fatigue test system. Compliance of springs was calibrated by comparing experimental and computed global relative slips. This methodology was then used to investigate local relative slip during fretting fatigue in cylinder-on-flat contact configuration under partial slip contact condition for unpeened and shot-peened titanium alloy, Ti-6Al-4V. Relative slip on contact surface is significantly smaller (about one order) than the measured global relative slip by using a conventional extensometer near the contact surface. Effects of coefficient of friction, rigidity of fretting fatigue system and applied stress to specimen on the global and local relative slips were characterized. Coefficient of friction and contact load have considerable effect on local relative slip, and practically no effect on global relative slip. Gross slip condition can develop at some locations on contact surface in spite of overall partial slip condition. Increase in rigidity of fretting fatigue system increases local relative slip but decreases global relative slip. Finally, fatigue life diagrams based on relative slip on contact surface are established for both unpeened and shot-peened titanium alloy. These show the same characteristics as of the conventional S-N diagram where fatigue life decreases with increase of relative slip. a = half width of contact zone E = Young's modulus E sp = modulus of elasticity of spring E pad = Young's modulus of pad F = applied force l AB = distance between contact point and location of extensometer's upper arm l DC = distance between points C and D M = bending moment acting on pad N = number of cycles N f = fatigue life P = normal contact load Correspondence: S. Mall.

Finite element implementation of multiaxial continuum damage mechanics for plain and fretting fatigue

“…It should also be noted that a constant COF value has been employed here across all fretting load cases, based on an average value identified from the test measurement [25,33]. This may lead to an underestimate of fatigue damage for partial slip cases, where high local COF values have been reported to occur [26]. Furthermore, there is insufficient test data available to quantify the key effect of scatter in fatigue; similarly for the predicted results.…”

“…It has been pointed out by Jin and Mall [25] that the FE predicted relative slip and the experimental observed slip magnitudes across the range from partial slip to gross slip do not agree. Sabelkin and Mall [26] concluded that (i) the experimentally observed relative slip was significantly larger than the actual slip at the contact surface and (ii) this is controlled by rig compliance and the COF. In order to estimate the local slip in FE and following the work of [26], Madge [17] employed the following relationship between FE and experimental slip (d local and d global respectively):…”

“…9 shows this in a schematic. Since FE predicted relative slip is locally computed it is called the local slip d local ; since the experimental observed slip incorporates the effects of rig compliance and the surface conditions, it is called the global slip d global [26]. As shown in Fig.…”

Wear characterization of Ti–6Al–4V under fretting–reciprocating sliding conditions

“…The actual relative slip (δ) between the pads and specimen is different from the applied displacement, δ app due to machine compliance [13,[24][25][26]]. An approach for measuring the relative slip, δ incorporating the effects of both the structural compliance and specimen elongation has been developed [25], and it was modified in the present study, i.e.…”

The Fretting Fatigue Behavior of Ti-6Al-4V

“…The difficulty with using the finite element method is the need for extreme mesh refinement or submodeling at the fretting hot-spot location. It is important to enforce stick and slip constraints along the interface to determine the local relative slip at the interface which is considerably smaller than what is measured at a remote point in a fretting fatigue experiment [25,26].…”