Measurements of restitution coefficients of ice at low temperatures

Measurements of the restitution coefficient (ε) of a smooth water ice sphere (radius = 1.5 cm) are made in a wide range of impact velocities (1≤υi≤700cms−1) and temperatures (113≤T≤269K). The impact velocity dependence of ε is different in the quasi-elastic and inelastic regimes separated by a critical velocity (υc) at which fracture deformation occurs at the impact point of ice samples. In the quasi-elastic regime (υi≤υc), the value of ε is almost constant (0.88) and ice samples show no fracture deformations. In the inelastic regime (υi>υc), ε decreases with increasing υi and ice samples have fracture patterns. The velocity dependence of ε is fitted as ε(υi) = (υiυc)−log(υiυc). vc is shown to increase with decreasing temperature from 25cms−1 (269K) to 180cms−1 (113–215K).