Fatigue damage estimation of icebreaker ARAON colliding with level ice

Abstract

This paper presents a methodology for precisely calculating the fatigue damage of an arctic vessel colliding with level ice. For accurate prediction of local ice loads acting on the external surface of the hull, focusing on the bow area, numerical simulation using the finite element method (FEM) was conducted first. The existing Drucker-Prager plastic model was combined with damage mechanics to simulate the icebreaking phenomenon. Furthermore, element erosion technology was considered to simulate crack formation and propagation through level ice that collides with a moving structure. Both dynamic drag and static buoyancy were applied to consider the dynamic behavior of submerged ice fragments. With this model, the ice resistance acting on rigid structures and a ship hull passing through level ice at multiple forward speeds were numerically calculated and compared with the test results. An additional simulation was performed in which ice fragments are removed immediately after being broken, with an attempt to decompose the total ice resistance into icebreaking resistance and the resistance of submerged ice fragments. Afterward, the spatial distribution of extreme values and frequencies of loads from the forefront to the vicinity of the hull shoulder area was derived. Finally, the ice load applied to the icebreaker ARAON at full scale under level ice conditions was calculated and then converted into stress at the target point using the influence coefficient method. Based on the converted stress information, the cumulative fatigue damage according to the speed was calculated, and the tendency of the cumulative fatigue damage was analyzed.