The friction of ice on ice at low sliding velocities

The kinetic coefficient of friction μ has been measured for both freshwater, granular ice and saltwater, columnar ice sliding against itself. The variables were ambient temperature (−3°C to −40°C), sliding velocity (5 × 10−7 −5 × 10−2 ms−1), normal pressure (0.007–1.0 MPa) and grain size (2.5–6.0 mm). Generally, μ decreased with increasing velocity and with increasing temperature, but was relatively insensitive to both pressure and grain size over the ranges investigated. At the lower temperatures (−30°C and −40°C) the frictionvelocity curve exhibited a peak at intermediate velocities. The friction coefficients for freshwater and saltwater ice were almost indistinguishable at higher temperatures (−3°C and −10°C), but saline ice had lower friction at lower temperatures. The results are explained in terms of frictional heating, creep and fracture.