| With the rise of prominence of the Arctic regions in the values of geo-strategy,shipping route and energy resources,the Arctic strategy has drawn the attention of many countries.Large-size underwater vehicles can carry out the missions of resource survey,geomorphic information collection and resource transportation in the Arctic.Due to the complexity of the arctic environment,there are certainly circumstances where large underwater vehicles need to ascend and break the ice to surface when performing missions.Therefore,it is of great importance to study the load characteristics of vertical ice-breaking.The focus of most of the existing researches is placed on longitudinal and transverse ice-breaking.Since the failure mode of vertical ice-breaking is different from these two forms of ice-breaking,the findings cannot be directly applied to vertical ice-breaking.In order to investigate the load of vertical ice-breaking,this thesis studies the dynamic characteristics of the load on a large underwater vehicle during vertical ice-breaking,and summarizes the methods for calculating the load of vertical ice-breaking.The main contents are as follows(1)Investigate the physical and mechanical properties of sea ice,and analyze different constitutive models and failure criteria of sea ice.Based on the sea ice model test,various sea ice mechanics models were established for numerical simulation.By comparing the results of model test and three-point bending test,it was found that the sea ice mechanics model based on the isotropic elastic-plastic constitutive model and Drucker-Prager failure criterion well serves the needs in this study.(2)The numerical model of large underwater vehicle is established,and based on the research of sea ice mechanics model,the ice load of elastic model,rigid model in vertical ice-breaking,and the ice load results of local model and overall model in vertical ice-breaking are compared and analyzed.Based on the accuracy and efficiency of the results obtained,the numerical simulation method of vertical floating ice-breaking was established using the whole model of underwater vehicle with rigid body materials.(3)Based on the numerical simulation method of large underwater vehicle vertical floating ice-breaking,the ice load characteristics of typical parts(bow,enclosure,hull and stern)during ice-breaking is studied.Statistical analysis of the ice load in typical locations under different working conditions,analysis of the space-time distribution characteristics of the ice load are performed,and calculation formula of design load on typical locations of underwater vehicle vertical floating ice-breaking is devised and verified. |
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