9 - Fracture of Ice and Its Time-Dependency

Summary

The chapter commences with a description of various observations of time-dependent fractures in ice. In the medium scale tests, slow loading resulted in very large flaws, whereas fast loading resulted in many small fractures and spalls in the vicinity of the load application. Then, a summary of fracture toughness measurements on ice are summarized. The question of stress singularity at crack tips is raised, and to deal with this, Barenblatt’s analysis is introduced, based on linear elasticity. Schapery’s linear viscoelastic solution for this method is described, using the elastic-viscoelastic correspondence principle. The J integral forms the basis of the application to fracture, using the correspondence principle noted. A set of experiments on ice samples, beams with 4-point loading, was conducted. Tests with a range of loading rates, as well as constant-load tests, were conducted. Comparison of the results with theory was made. The results of Liu and Miller using the compact tension set-up were also considered. Good agreement with theory was found in all cases. Nonlinear viscoelastic theory of Schapery is also outlined.