Fretting in Aerospace Structures and Materials

Abstract

Fretting, the deleterious and synergistic combination of wear, corrosion, and fatigue phenomena driven by the partial slip of nominally clamped surfaces, has been linked to severe reductions in service lifetimes of a myriad of contacting components, including bearings, turbine blades and mechanically fastened joints-both structural and biological. This paper serves to frame the aggregate of economic, operational, and technical developments responsible for engendering renewed interest in fretting fatigue of critical structural elements of both commercial and military aerospace systems, including riveted primary structure and the blade/disk pair in jet propulsion plants. A collection of both empirical evidence of fretting-induced componential degradation and an overview of results from recent investigations conducted by the authors serves to motivate the need for design-oriented metrics that can be used to ensure the structural integrity and safe operation of both current and future aerospace systems.

An energy description of wear mechanisms and its applications to oscillating sliding contacts

“…1). Because of research efforts of the last 15 years, crack nucleation and the crack propagation [5,6,7] can now be predicted, whereas the threshold transition from a short to a long crack is in progress [8].…”

Predicting a contact's sensitivity to initial conditions using metrics of frictional coupling

“…This is because complete contacts are always coupled due to domain mismatch, and half-plane contacts cannot shake down aside from a few special cases. 7 Thus, for this verification, 90 • and 120 • common-edged contacts 8 were subjected to the loading regime shown in Fig. 9(a): namely, a constant normal load, P , was applied, and then a shear load, Q, was cycled within the range [Q min , Q max ], where Q min = −Q max .…”

“…Although the interfaces in components such as these usually appear to be stuck together, zones of micro-slip commonly develop at the edges of contact during cyclic loading. This has two main effects: (i) it results in the well-known damage process of fretting fatigue, which significantly reduces the service life of engineering components [7]; and (ii) it provides a source of damping, which can improve system performance [8,9]. Because of these effects, it is important for engineers to be able to predict the slip-stick behavior of frictional interfaces.…”

Subsurface crack formation and propagation of fretting fatigue in Ni‐based single‐crystal superalloys

“…The dovetail joint between the turbine blade and disk employed in aero‐engine or gas turbine is a typical fretting condition, and the fracture occurring at the turbine blade root will cause aero‐engine failure and aviation accident . According to the statistics from US Air Force (USAF), fretting fatigue occupies 1/6 of fatigue‐induced aero‐engine failure, thus the fretting fatigue properties of turbine blade attract more and more interests from researchers. Ni‐based single‐crystal (NBSX) superalloys are widely used in manufacture of advanced turbine blade for its excellent mechanical properties at high temperature.…”