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26 SAMC
o
T • Annual report 2012
The effects of the sliding velocity (6 mm/s to 105 mm/s),
air temperatures (-2°C to -20°C), normal load (300 N to
2,000 N), presence of sea water in the interface, and ice
grain orientation with respect to the sliding direction on
the friction coefficient were investigated.
“The major findings from the tests are as follows”, says
Sukhorukov:
• Ice surface roughness is the key parameter that de
termines the value of the friction coefficient. Repeat
ed sliding over the same track led to surface pol
ishing and decreased the kinetic friction coefficient
from 0.48 to 0.05.
• The friction coefficient was found to be independent of
the sliding velocity (6 mm/s to 105 mm/s) when sliding
occurs between natural ice surfaces. As the contact
ing surfaces become smoother, the kinetic friction
coefficient started to depend on the velocity, as pre
dicted by existing ice friction models, i.e.
µ ~ ν
−0.5
.
• The effect of the air temperature on the kinetic fric
tion coefficient was not detected. Both very high
(~0.5) and low (~0.05) kinetic friction coefficients
were obtained in the tests performed at high (-2°C)
and low (-20°C) air temperatures. Significant scatter
in the data was observed because of the difference in
the ice surface roughness.
• The frictional force (both static and dynamic) was lin
early related to the normal load.
• The presence of sea water in the sliding interface
has very little effect on the static and kinetic friction
coefficients.
Ice Actions on a Floating Jetty
Floating structures may also be used close to shore.
In 2008, the Port of Longyearbyen decided to increase
their harbour facilities by launching a Floating Jetty
(Fig. 20). The jetty consists of two sections, each 20×5
m, linked together in such a way that the jetty is 42 m
long. Basically 30 mm thick PE100 is used as material
in the jetty.
Fig. 19. Temporal variations of the frictional force in stick-
slip regime a) and steady sliding regime b).
The test parameters:
a) the normal force was 242.4 N, the apparent contact
area Sa = 0.101 m
2
, the sliding velocity v = 5.4 mm/s, Tair =
-10.6°C, Ttrack = -5.5°C, and Tice block = -4.4°C;
b) the normal force was Fn = 276.8 N, Sa = 0.0714 m
2
, v = 87.7
mm/s, Tair = -2°C, Ttrack=-2.9°C, and Tice block=-2.3°C.
Fig. 20. Location of the floating jetty and direction of sea
current and ice drift.