Cone Ice Crushing Tests and Simulations according to Various Yield and Fracture Criterion

초록

Assessment of ice load caused by collision between ice and marine structure is important to estimate the structural safety of ships and offshore structures. Cone type ice crushing tests with fresh water ice have been carried out by MUN. In order to find best-fit yield functions and fracture criterion with crushing test results, numerical simulations have been conducted according to yield functions of crushable foam, Drucker-Prager, and Mohr-Coulomb, three different hardening models of M1, M2, and M3 in which each has different relation of uniaxial compressive yield stress versus volumetric strain, and ice-spalling criteria composed of damage initiation and evolution, and two different element densities. Crushing test results carried out by MUN are explained. Cone type ice specimens with 10 cm diameter were crushed by a rigid flat indenter. The test results were crushing force versus indenter stroke. A new concept 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 greatly effect 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.