Research On The Structural Strength And Design Parameters Of Flexible Connection Channels For Underwater Multi-body Structures

The International Seabed region is rich in resources,and the underwater vehicle is an important carrier for underwater scientific research and resource development.With the development of mining progress,large-scale deep-sea underwater platforms emerge as the times require.Because large underwater platforms usually need large depth and large drainage,and it is impossible to increase the geometric scale of pressure hull indefinitely due to the limitation of shell thickness and material properties,so multi-body pressure-resistant structure is proposed at home and abroad.This structure is composed of several pressure spherical shells with relatively small diameters,which can meet the needs of large underwater platform under the existing materials,processing technology and welding capacity of thick plates.The multi-body pressure-resisting structure solves the limitation of shell thickness and material performance,but the problem of connecting passage of multi-body pressure-resisting structure follows.The stress of the connecting passage is complex and easy to cause relative deformation,so displacement compensation is needed,which leads to the problem of flexible connection of the connecting passage.Based on the design and application of corrugated pipes,the spiral ribbed cylindrical shell is proposed as a flexible connecting passage for underwater multi-body structures,and the structural strength and design parameters of flexible connecting passage are studied.The main works of this paper are as follows:(1)Structural design and failure mode analysis of flexible connection channels.The main factors that need to be considered in the shape design of multi-body pressure-resistant structures are analyzed.The advantages and disadvantages of different combinations of multi-body pressure-resistant structures in volume-weight ratio,internal space utilization and processing technology,and their effects on the shape design of multi-body pressure-resistant structures are comprehensively analyzed.Considering the strength and stability of multi-body compressive structure,the formula for calculating the volume-weight ratio of the simplest spherical-cylindrical composite compressive structure with the shape of dumbbell is deduced.The stress analysis of spiral ribbed cylindrical shells and non-stiffened spherical shells under load are discussed,with emphasis on the failure mode of spiral ribbed cylindrical shells.(2)Research on stiffness and strength of flexible connection channel.Abaqus finite element program is used to compare the spiral ribbed cylindrical shells connection passage proposed in this paper with the previous uniform ring ribbed cylindrical shell connection passage.The stress intensity and deformation characteristics of spiral ribbed cylindrical shells at arbitrary positions under external pressure are calculated quantitatively,and the variation law with structural parameter(L/ R,l,t)is analyzed through a series of calculations.(3)A large number of finite element simulations of spiral ribbed cylindrical shells are carried out to reveal the characteristics of instability waveforms of spiral ribbed cylindrical shells.A numerical method for calculating the ultimate strength of spiral ribbed cylindrical shells considering geometric and material nonlinearities is proposed.(4)Applying ANSYS finite element software to optimize the structural parameters of spiral ribbed cylindrical shells,the rational structural type of spiral ribbed cylindrical shells is studied on the premise of ensuring the structural strength of spiral ribbed cylindrical shells.According to the optimum design parameters of compressive structure based on strength standard,the strength and stability of compressive structure are calculated and checked by Abaqus finite element software,and the different rib reinforcement modes of compressive cylindrical shell are compared and analyzed.(5)Taking spiral ribbed cylindrical shells as connecting channels,different spherical-cylindrical composite multi-body compressive structure schemes are designed,and the differences of flexible connection level,strength and stability of connecting channels at different locations are analyzed and compared.