Effect of the contact pressure on the fretting of railway axle journal bearings

Abstract

The fretting wear is caused by the very slight relative slip between the contacting surfaces of the inner ring side face and the backing ring of an axle journal bearing in railway applications, but its mechanism is not clear. In this work, first we have conducted a reproduction test using a full-scale railway axle journal bearing in order to understand the fretting wear behavior of the axle journal bearings. Secondly, laboratory tests using a full-scale railway axle journal bearing were conducted to investigate the contact pressure distributions by inserting a film pressure sensor between the inner ring side face and the backing ring of the axle journal bearing under the conditions of radial loads. It has been found that the fretting wear of the backing ring becomes larger in the proximity to its outside diameter, the contact pressure of the opposite of the load side is larger than that of the load side and the contact pressure becomes larger in the proximity to its outside diameter. Accordingly, the fretting wear area of the backing ring is approximately coincident with the area where the amplitude of the contact pressure is large.

Effects of segment-structured DLC film on the fretting wear of railway axle journal bearings

“…Moreover, the fretting wear of the backing ring is more remarkable than that of the inner ring. The fact that the fretting wear generated remarkably at the radially outer contact surface is the same tendency as the previous works (Okamura et al, 2016(Okamura et al, , 2018a(Okamura et al, , 2018b Fig. 17 The inboard inner ring large side face after the rotation test.…”

“…It is concluded from the above mentioned that the S-DLC film is effective in suppressing the fretting wear generated on the contact surfaces between them of the axle bearings. Now the authors have reported in our previous paper (Okamura et al, 2016) that the fretting wear generated remarkably at the radially outer contact surface being subjected to higher contact pressure between them. As mentioned in 3.1.3, it was observed that S-DLC film was removed from the contact surface in the radial direction towards the outer side (see Figs.…”

“…The fretting wear of the backing ring side face occurs all over the contact surface with the inner ring from the center to the outer diameter in the radial direction. As previously described (Okamura et al, 2016), this is because the backing ring goes up the tapered portion of the axle journal and is expanded radially, when the axle bearing is fitted onto the axle journal. The fretting wear of the inner ring occurs all over the contact surface with the backing ring.…”

“…When an axle bearing is fitted onto an axle journal, the backing ring goes up the tapered portion of the axle journal and is expanded radially, so that the backing ring side face deforms (Okamura et al, 2016). Furthermore, some cracks and decohesion can occur in C-DLC film because the film coated on the backing ring side face is not able to follow the iteration deformation of the backing ring due to the rotary bending of the axle (Okamura et al, 2018b).…”

“…In our previous studies, the authors investigated the effects of the contact pressure between the inner ring and the backing ring on the fretting in order to elucidate the mechanism of the fretting generation; through a reproduction test of fretting using a full-scale axle bearing in order to understand the fretting wear behavior between them. As the result, the authors found that (1) the fretting wear between them becomes more remarkable on the outer side of their contact surfaces in the radial direction, (2) the contact pressure between them distributes all over the contact surface, especially on its outer side in the radial direction, and (3) the fretting wear area of the backing ring is approximately coincident with the area where the amplitude of the contact pressure is large (Okamura et al, 2016).…”