Experimental study of the quasi-static and dynamic fracture toughness of freshwater ice using notched semi-circular bend method

The dynamic fracture toughness of ice involves its fracture resistance under impact loading, which is essential for impact or blasting parameter selection and evaluation. Temperature is an important factor influencing ice mechanical properties. To examine the evolution of ice fracture characteristics at different loading rates and temperatures, notched semi-circular bend method was applied to determine the freshwater ice quasi-static and dynamic fracture toughness. A modified low-temperature split Hopkinson pressure bar system was developed to measure dynamic ice fracturing properties. A high-speed camera captured ice specimen cracking initiation and propagation processes. The experimental results indicate that the overall initiation fracture toughness (IFT) of freshwater ice under dynamic loading exceeds that under quasi-static loading. The loading rate effect on the dynamic fracture toughness and failure modes greatly exceeds the test temperature effect. The freshwater ice dynamic IFT increases approximately linearly with the loading rate and rapidly at temperatures from –5°C to –45 °C. In all tests, cracks always initiate from the notch plane. Two symmetrical curved cracks then propagate from the contact end of two support rollers to the flat contact end, ultimately leading to different sample fragmentation distributions. These results improve the understanding of the dynamic fracturing mechanism in ice engineering applications.