Finite element analysis of ship-ice collision using LS-DYNA

Abstract

The energy industry's increasing interest in the Arctic region demands more and stronger polar ships. IACS has released a set of documents titled Unified Requirements for Polar Ships (URI) to harmonize different ice classification specifications. This thesis defines a procedure for evaluating an "IACS Polar Class" ship under ice impacts using LS-DYNA, an explicit finite element analysis tool. The final product includes a numerical model that is capable of evaluating the global motions of the ship and ice, the ship-ice contact force, and the local structural response of the ship. A few ice material models whose pressure-area relationships comply with the URI are proposed as well. Restoring forces are modeled using user-defined-curve-functions. This innovative approach significantly reduces the computation cost by excluding the water domain from the analysis. The Arbitrary Lagrangian-Eulerian method in LS-DYNA is discussed and employed to estimate necessary inputs for the user-defined-curve-functions. Several ship-ice impact scenarios are modeled in LS-DYNA and contact forces are compared with the estimations by DDePS, a simple analytical solution that is consistent with the URI. In the last part of this thesis, the ship from the previous analysis is ice-strengthened with internal structures in accordance with the URI and the DNV specifications. Local structural response of this ship under ice impacts is assessed.