Research On Calculation Method Of Ice Load For Polar Heavy Icebreaker

The polar heavy icebreaker has the ability to work during winter/spring in the high latitude ice area where the working environment is extremely harsh,and it can withstand the combined effects of various ice loads under extremely low temperature conditions,including the crotch impact ice load generated by various types of icebreaking conditions,and the ship central side extrusion,local ice pressure,etc.As polar sea ice changes rapidly,the polar region channel becomes a trade route bridging Asia and Europe while sea ice remains the main factor that threats safe navigation.Therefore,the spatial distribution and mechanical properties of sea ice are of great importance to anti-ice structures of ships and are thus studied.The polar ice area where navigation and operation are carried out are predominately made of multi-year ice,especially the key operation areas.Due to the particularity of its operating environment and mission,heavy icebreakers have special features in ice load forecasting and design and placement of ice zone components.This paper is to serve the development of polar heavy icebreaker ship by carrying out multi-year sea ice mechanical characteristics simulation and numerical simulation model research.It aims to collect the characteristics of polar multi-year ice from domestic and foreign references.We started to find a standard parameter that meets the geometric and strength requirements of the polar multi-year ice model in terms of physical attribute and material properties.Then,we focus on studies on the calculation method of the ice load of the polar heavy icebreaker and the ultimate bearing capacity of the typical structural zone of the ice belt.The main research contents are as follows:(1)Study on the physical attributes and mechanical properties of multi-year sea ice in the polar was conducted by comparing and analyzing the characteristics of polar ice and one-year ice in terms of sea ice thickness,salinity,density,friction coefficient,tensile strength,bending strength,shear strength,compressive strength,elastic modulus and Poisson's ratio.And we studied the mechanical properties and numerical simulation models of multi-year sea ice,summing up the ice body characteristics of the polar multi-year ice model by applying to different sea ice material distribution to simulate the destruction of polar ice for many years.(2)The dynamic process of icebreaker and polar ice collision is simulated based on the numerical simulation of polar sea ice numerical model.A complete ice load calculation method is proposed.The nonlinear finite element numerical simulation method is used to simulate the collisional icebreaking.The theoretical calculation and the numerical simulation method are combined to simulate the continuous icebreaking.The material parameters and failure criteria of different sea ice are selected,and the corresponding working conditions are set according to the ice pole specification to simulate the structures' interaction with sea ice.(3)Study on the ultimate bearing capacity of the ship structure in the polar region.We calculate the ice load value of the target ship's first structure using the corresponding ice level specification.Then we can numerically simulate the ship ice collision process based on the nonlinear finite element numerical simulation method to obtain the contact surface at any time.The ultimate bearing capacity of the structural frame considering the plastic deformation of the material is analyzed.The results are compared with ice level specification,which provides a more reasonable method for determining the structural design load of the heavy icebreaker.