The kinetic friction of saline ice against itself at low sliding velocities

An experimental investigation was performed on the kinetic friction coefficient of laboratory-grown, columnar saline ice sliding against itself. Tests were performed on a dual-opposing load apparatus specially manufactured for attachment to an MTS testing system. The mean kinetic friction coefficient, μ, was measured for sliding velocities from 10−6 to 5 × 10−2 m s−1 at temperatures from —3° to —40°C under a contact pressure of about 20 kPa. The ice specimens were oriented with grain columns perpendicular to the sliding interface. At -3°C and at —10°C, three distinct regions were observed: from 10−6 to about 10−5ms−1, μwas nearly constant at 0.5; at velocities from 10−5 to 10−3 m s−1, μ began to drop rapidly to about 0.1; and, above 10−3 m s−1, μ began to level off at ~0.05. The velocity at which μ began to decline increased with decreasing temperature. At temperatures below —10°C, μ increased from ~0.5 at v =10−6ms−1 to a peak value of ~0.7 near a velocity of 5 × 10−5ms−1 and then fell rapidly to about 0.1 at 10−2ms−1. In general, μ increased with decreasing temperature and sliding velocity.