Fig.7 amplified images of the slip and stick regions in Fig.6(b) and
Fig.6(d)
The surface of the sample continuously undergoes plastic deformation due
to the fretting friction between the sample and the fretting pad in the
slip region. After repeated sliding, rolling, and smoothing, plastic
failure occurs on the surface. Lamellar spalling occurs in the slip
zone, forming pits and wear debris with different depths and shapes. The
overall damage in the slip region is relatively large, the scratches are
deep, and the surface is extremely rough. Because of the wiping effect
of abrasive particles on the surface of the slip region, there are
almost no microcracks on the normal surface, and the microcracks occur
only at the edges of the pits where stress is concentrated. Kozo
Nakazawa et al. 23 made similar findings in their
research. In the stick region, due to the coupling effect of adhesion
and fretting, the surface material of the sample is severely torn, and
many small pits are connected to form a large pit. The surface damage is
small in the stick region where no tearing of the surface material has
occurred, and basically no slip marks similar to the slip region.
The morphology of the stick region and the slip region with an
equivalent stress of 400 MPa and a contact stress of 150 MPa under SP is
shown in Fig7.(h)(i); There are a lot of abrasive debris in the slip
region of SP, and furrows caused by the sliding effect can be seen
everywhere, and the surface is very rough; The surface of the stick
region is smoother than that of the slip region, and the surface is free
of scratches caused by the sliding effect, but there are pits of
different shapes caused by the surface material tearing. Compared with
DP, the area and depth of the pits generated in SP are less.