Fretting fatigue tests on shrink-fit specimens and investigations into the strength enhancement induced by deep rolling

Initial orientation of the fretting fatigue cracks in shrink-fit connection specimens

“…he setup of the fretting experimental tests investigated in this paper is shown in Fig. 1 (a), following our previous work: Bertini and Santus [22]. The specimen shaft is manufactured in aluminium alloy 7075-T6, with a conical end which is then shrink-fitted into a steel hub, allowing the connection shrinkage intensity to be controlled with an adjusting nut.…”

“…Other test setups have also been proposed, resembling the component under the actual load, still loaded with a laboratory testing machine, such as by Golden et al [16,17] for blade dovetail connections. This approach was also followed for the shrinkfitted shaft-hub connection by Juuma [18,19], Alfredsson [20], Lanoue et al [21], and finally by Bertini and Santus, and Bertini et al [22,23]. There is experimental evidence of fretting crack paths in the literature, such as by Szolwinski and Farris [9], Swalla and Neu [6], Muñoz et al [10], and Proudhon et al [24].…”

“…This is of great interest for this kind of analysis, especially considering that the crack orientation outward, which can be predicted as an effect of the normal stress correction, is very rarely observed. In this paper the fretting fatigue tests, which we previously presented in Bertini and Santus [22], are reconsidered and the initial crack orientation, evident by means of Scanning Electron Microscope (SEM) observations, is discussed by comparing these approaches proposed in the literature. The main interest of these tests is that the contact pressure fluctuates with the bulk bending load, which causes the tensile stress to be less predominant than in the usual test rigs where the pressure remains (almost) constant during the fretting cycle.…”

Investigation of microstructure effect on fretting fatigue crack initiation using crystal plasticity

“…If the components undergo an oscillatory force, the cracks will propagate through the material that can lead to fatigue failure. This phenomenon is common in bolt and riveted joints, 2 spline coupling, 3 shrink-fit connections, 4 and dovetail joints. 5 Many researchers have focused on fretting fatigue and have endeavoured to reveal different aspects of this NOMENCLATURE: _ γ α ð Þ , slipping rate; _ a, reference strain rate; D L , small grain size; D mean , mean grain size; D R , large grain size; d reg , seed spacing in regular tessellation; F * , stretching and rotation; F P , plastic deformation; g (α) , current strength of the α slip system; g ∾ , saturation stress; g 0 , critical resolved shear stress; h 0 , initial hardening modulus; h αβ , slip hardening modulus; L P , plastic velocity gradient; m (α) , normal to slip plane unit vector; p crit , critical accumulated plastic slip; p cyc , stabilized accumulated plastic slip; P r , percentage of grains within the range; s (α) , slip direction unit vector; τ (α) , resolved shear stress on α slip system; F, deformation gradient; n, rate sensitivity exponent; N, fatigue life; p, accumulated plastic slip; α, slip system index; δ, minimum seed spacing; λ, regularity parameter phenomenon.…”

“…If the components undergo an oscillatory force, the cracks will propagate through the material that can lead to fatigue failure. This phenomenon is common in bolt and riveted joints, spline coupling, shrink‐fit connections, and dovetail joints …”