Numerical Simulations of Cone Ice Crushing Tests according to Various Yield Functions and Fracture Criteria

초록

Assessment of ice load caused by collision between ice and marine structure is important to assess the structural safety of ships and offshore structures. Crushing tests of cone-shaped ice specimens have been carried out by MUN. In order to find what types of yield functions and fracture criteria well predicts crushing test results in terms of crushing force, simulations have been conducted using yield functions of crushable foam, Drucker-Prager, Mohr-Coulomb where high(M1), medium(M2), and low(M3) compressive hardening cases are considered and using ice-spalling criteria. Cone-shaped ice specimens with 10cm diameter were crushed by a rigid flat indenter. A new concept as a fracture criterion is introduced where fracture energy is not constant and varying in line with contact area exposed to the rigid indenter. Displacement-dependent fracture energy is defined to finite elements corresponding to each vertical layer. For five variables of function, hardening intensity, damage initiation/evolution, and mesh density, parameters study has been performed. Damage initiation criterion is believed to be negligible effect, while damage evolution criterion affects greatly to ice crushing forces. Final parameter is mesh density and there is little effect of mesh density because ratio of element length to fracture energy determines level of damage evolution.