Ship owners, including navies, are increasingly sailing ice-infested waters and hence need to know the safety of ship hulls regarding collision with ice. Considerable knowledge exists for modelling failure of the hull in impact situations; however, these methods are either insufficiently precise or too expensive for engineering practice. A method is discussed where the material is characterized to utilize the full energy absorbing capacity until rupture with limited parameters and associated testing. The underlying theory is provided, and the required material tests are described. After calibration of the material and failure models, the application on a large-scale raking test is demonstrated.
With the artic region becoming more accessible for sailing, the current fleet of ships extends the operational area to the North, including the Marginal Ice Zone (MIZ). With the increased amount of shipping, the probability of ice collision increases. Also, the chance of ‘normal’ ships sailing into the arctic area increases, thus ships without ice class or any considerations to withstand lower temperatures or impacts with ice.
For the maritime industry and navies, it is crucial to know if their "normal", non-ice-classed ships, can withstand the conditions that occur in the arctic area or the MIZ. Additionally, with the adequate calculation method, the benefit of using higher strength or higher ductility steels in new builds can be demonstrated.
Ice impact analyses consist of three main aspects: the load from ice, determined by the size of the ice floe and its impact speed, the distribution of the load on the hull, and the resistance of the hull against such impacts. This paper focuses on the third aspect.
There is a strong analogy with collision and grounding analysis. For ice impact, only the glancing or raking damage scenario is of interest. This impact scenario has received special attention since the grounding of Exxon Valdez and has resulted in large and small scale experiments and development of material failure models. Some experimental highlights are:
Full scale tests at NSWC (Rodd, 1996) and TNO (Vredeveldt and Wevers, 1995) in the 1990s
Denting tests (Muscat-Fenech and Atkins, 1998)
More recent raking damage drop tests (Haag, 2017).
