EXPERIMENTAL RESULTS ON THE TENSILE STRENGTH OF ATMOSPHERIC ICE

Abstract

The tensile strength of atmospheric ice samples (glaze and rime) obtained in an open type wind tunnel has been measured. Ice was grown from supercooled water droplets impinging on a rotating aluminium cylinder. In a first series of tests, the liquid water content of air was set at 0,8 g/m3 and the tensile strength of atmospheric ice was measured as a function of temperature ranging from −3 to −20°C, wind velocity during accretion ranging from 10 to 23 m/s and nominal strain rate ranging from 8, 70 × 10-7 to 1, 88 × 10-3 s-1. In a second series of tests, the liquid, water content of air was set at 1, 2 g/m3 and the wind velocity was maintained at 23 m/s. The tensile strength was measured as a function of temperature ranging from −3 to −20°C and larger nominal strain rate ranging from 7,25 × 10-8 to 7, 25 × 10−3 s−1. Maximum strengths, measured at −14°C, are found to be 5, 0 MPa at 1, 2 g/m3 liquid water content and 3, 1 MPa at 0, 8 g/m3 liquid water content. For the lowest temperatures used (−14 and −20°C), the atmospheric ice tensile strength increases with strain rate in the ductile range, i.e. strain rates lower than about 10−6 s−1. In these cases, the strength is found to be maximum for strain rate corresponding to the ductile-brittle transition and decreasing for higher strain rates. For the highest temperatures used (−3 and −8°C), the tensile strength of ice is found to be nearly constant as a function of strain rate.