Abstract
The effects of surface roughness and topographical
orientation on surface stresses influencing wear have
been investigated for diamond like carbon (DLC) coated
steel surfaces with three levels of surface roughness in
the range of 0.004-0.11 µm Ra values, and with
topographical groove orientations of 0°, 45° and 90°. A
novel multiscale numerical finite element method (FEM)
model was developed to integrate the layered and
microstructural material features with the grooved
topography. Fractal geometry and a surface voxelisation
based approach were utilised to derive 3D surface
topography. The surface texture representation includes:
fractal signatures, which are sets of fractal dimensions
calculated at individual scales in different directions,
texture aspect ratio describing surface anisotropy, and
texture direction signatures calculated by the variance
orientation transform (VOT) method. The simulations show
details of the main topographical orientation effects on
local stresses affecting wear as they appear at a single
scratch test with a spherical diamond ball and in a
self-mated sliding situation of two rough surfaces. The
45° sliding direction in relation to grooves resulted in
a mixed state of surface loading in the scratch test
contact. In the complex state of stress-strain within the
roughness peaks the overall tensile stress decreased,
leading to greater surface resistance to cracking as
compared to 0° and 90° directions. Model based
calculations showed that the surface structure was about
four times more rigid in the direction of grooves as
compared to the more flexible behaviour in the
perpendicular direction. This behaviour was empirically
confirmed. The numerical calculations of rough vs rough
sliding surface include real surface topographical
features at various scales, material microstructural
features down to nano-scale and
topographical-microstructural interaction features. This
approximation is thus more comprehensive than the
classical approach. The real area of contact was 15-30%
of the apparent contact area. The macro-topography
dominated the tendency for surface cracking and plastic
deformation, which is influencing on both wear and
friction, while the micro-topographical features
contributed to cracking and deformation by less than 40%.
Original language | English |
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Pages (from-to) | 18-28 |
Number of pages | 11 |
Journal | Wear |
Volume | 388-389 |
DOIs | |
Publication status | Published - 15 Oct 2017 |
MoE publication type | A1 Journal article-refereed |
Keywords
- Friction
- Wear
- Topography
- FEM modeling
- DLC
- ProperTune