STRENGTH ESTIMATION METHOD OF SHIP SIDE STRUCTURES SUBJECTED TO HARD BOW COLLISION

In the collision of hard and sharp bows, breaking of ship side structures starts from the point of collision on the bow, while in the collision of soft and rounded bows, breaking is likely to start from the supported point such as the bulkhead or transverse web frame. In the case of breaking from the point of collision, stretching of ship side structures is followed by crack propagation, so absorbed energy should be evaluated in consideration of crack propagation. In this paper, to develop an evaluation method for breaking from the point of collision, double hull panel models, which are typical of ship side structures of VLCCs, were destructed with the indentation or a rigid bow model which was pushed dynamically as well as statically. The first crack initiation condition was investigation by finite element simulation using fine mesh solid element models and crack initiation was found to be estimated with the ductile damage parameter which consists of equivalent plastic strain and stress triaxiality. Then crack propagation condition was investigated by finite element simulation using coarse mesh shell element models. It was found that reduction of the reaction force due to crack propagation could be simulated by finding the elements adjacent to the crack and reducing the failure strain for those elements.