Research On Ultimate Strength Of Polar Ship With Collision Damage Repaired By CFRP

With the global warming and the improvement of the seaworthiness of the Arctic waterway,more and more ships are sailing in the Arctic.However,the environment of the Arctic is poor,and ships sailing in the Arctic may be affected by strong winds,waves and ice,among which the ice load has the greatest impact on the ship structures.There are many accidents caused by ship-ice collision,among which sag damage is common.In the actual accident,some of the ship structures with sunken damage can still be operated.In this thesis,it is proposed to use carbon fiber composite material,namely CFRP,to repair the damaged ship,which can effectively and quickly improve the structural strength of the hull and improve the structural safety of ships sailing in polar regions.In this thesis,aiming at the process of ship-ice collision,considering the material characteristics and selecting the appropriate sea ice model,the process of ship-ice collision is simulated more accurately,and the sag damage model of stiffened panels under various working conditions is obtained.And its ultimate strength is calculated,and low temperature consideration is added to explore the effect of temperature.Then the use of CFRP to repair the sunken damaged stiffened panel is proposed,and the influence of repair parameters on the repair effect is analyzed.Then the properties of adhesive layer and CFRP at low temperature are summarized to explore the effect of low temperature on the repair of sag damaged stiffened panels by CFRP.Finally,the collision scheme of sea ice-hull girder is designed,and the sunken hull girder is repaired by CFRP to explore the repair effect of CFRP on the damaged hull gieder at low temperature.The specific research contents are as follows:(1)Through the finite element software ABAQUS,a suitable sea ice-stiffened panel collision model is established,and the sag damage stiffened panel model is obtained,and the ultimate strength of the sag damage stiffened panel is calculated.It is found that the sag damage will reduce the bearing capacity of the stiffened panel.And the deeper the sunken is,the more obvious the ultimate strength of the stiffened panel decreases,while the effect of the sunken area on the ultimate strength is not obvious.With the addition of the influence of low temperature,it is found that the ultimate strength of the stiffened panels made of EH36 steel will not decrease more obviously due to the decrease of temperature.(2)CFRP is used to repair the sunken damaged stiffened panels,and the repair model is subjected to uniaxial compression,and its ultimate strength is calculated by step-by-step failure method.The result shows that using CFRP to repair the damaged stiffened panels can effectively improve its ultimate strength.The effects of CFRP,adhesive layer and sunken parameters on the ultimate strength are analyzed.It is found that the repair effect is the best when the CFRP laying angle is 0 °,the repair effect will be improved by increasing the number of layers,and the repair effect can be enhanced by increasing the size of CFRP.It is most economical to use CFRP to repair the upper layer on one side.The thickness and properties of the adhesive layer has little effect on the repair.The effect of CFRP in repairing the damaged stiffened panels will become better with the increase of the depth and area of the sunken.(3)According to the existing experiments,the effects of low temperature on adhesive layer and CFRP parameters are obtained,and the parameters of adhesive layer and CFRP at different temperatures are obtained according to the influence law,and used to study the effect of low temperature on CFRP repairing stiffened panels with different sunken area and depth.The results show that the repair effect decreases with the decrease of temperature.When the sunken area is the same,the deeper the sunken is,the better the repair effect of CFRP is.At low temperature,the repair effect will become better with the increase of sunekn area.(4)Establish the cabin model,design a reasonable collision scheme,and calculate the ultimate bending moment of sunken damaged hull girder and CFRP repaired sunken damaged hull girder in the case of sagging and hogging,respectively.The result shows that the sunken will reduce the ultimate bending moment of the hull girder,and with the increase of sea ice collision speed,the sunken deepens and the ultimate bending moment decreases.However,the use of CFRP for repair has a certain effect on both the side sunken and the bottom plate sunken.Considering the low temperature,it is found that the repair effect of CFRP on the hull girder decreases with the decrease of temperature.