Flexural strength is the important factor for calculating the ice resistance caused by the interaction between icebreaker or icebreaking vessel and level ice. But the influence of flexural strength on ice resistance is often ignored in the numerical simulation by commercial software. Thus, it is meaningful to realize the influence of flexural strength on ice resistance in software. In this paper, an isotropic elastic-plastic material model was chosen as the ice material. The strength was changed by altering the effective plastic failure strain and the Young modulus. And the flexural strength calculation formula was derived. Then, different parameters were employed for the numerical simulation of ship-level ice interaction to simulate the collision between a ship and sea ice with different strengths. The method proposed in this paper can be used to study the influence of sea ice with different strengths on ice resistance and can also be extended to more material models of sea ice in the numerical simulation.
Icebreakers and icebreaking vessels often collide with sea ice when navigating in ice-covered areas, which may cause large ice resistance. This is directly related to the icebreaking capacity of the ship in these areas, and also an important reference for calculating the power of the main engine, carrying out the optimal design of the ship type and the structural design of the ship (Kim et al., 2014; Wu, Wang and Zhang, 2020). Thus, it is very important to evaluate the ice resistance of ships in these areas.
There is no general and accurate method to predict the ice resistance of ships (Jeong and Choi, 2009; Guo et al., 2015). The common methods are semi-empirical formulation (Lindqvist, 1989; Spencer, 1992), numerical simulation (Su, Riska and Moan, 2010; Zhang et al., 2019), model-scale (Zhou et al., 2013; Myland and Ehlers, 2017), and full-scale test (Riska et al., 2001; Lee et al., 2018). The semi-empirical formulation has a small scope of application, while the model/full-scale test is expensive and uneconomic. As for the numerical simulation, it has gradually become the main method of ship performance analysis in ice-covered areas because of its fast calculation speed and low cost. At the same time, the numerical simulation can easily modify the characteristics of ship hull and sea ice, which is of great significance to the research of ship performance in these areas and the development of new ship forms. Ice material has a great influence on the accuracy of the calculation result in the numerical simulation. Until now, the research of ice material in is still a hot spot. In commercial software, researchers try different material models to find the suitable model which matches the test result well. Taking LS-DYNA as an example, a variety of material models have been tried and verified, mainly the simple plastic strain failure model (Li et al., 2019), the elasto-plastic material with arbitrary stress versus strain curve and arbitrary strain rate dependency (Wang et al., 2018), the crushable foam material model (Gagnon and Derradji-Aouat, 2006), and the isotropic elastic-plastic material with unique yield stress versus plastic strain curves for compression and tension (Sazidy, 2015).
