Key Techniques For A Large-Volume,Full-Sea Deep-borne Simulation Device

With the development of deep-sea exploration technology,China has proposed the strategic planning toward the exploration of the deep blue sea.Bathyscaphes and related equipments are necessary for scientific research,environmental detection,exploration,and development of the deep sea.With the continuous development of bathyscaphe technology,deep-sea environmental simulation technology and equipment play an increasing role in the testing,verification,improvement,and upgrading of bathyscaphes.In 2012,Jiaolong,China’s first self-developed manned submersible,completed its 7000 m sea trial under a working pressure of 70 MPa,making China become the fifth country in the world after the America,Russia,France,and Japan to master deep manned submersible technology.The Mariana Trench,the deepest point in the ocean,is about 11000 m deep,and the pressure is beyond 110 MPa,which is the ultimate challenge for deep manned submersibles.However,the volume of the deep-sea simulation device currently built in China cannot meet the test requirements of the full-sea deep-borne manned submersible.Therefore,to meet the major strategic needs of our country to explore the deep-sea environment,develop and utilize the ocean,and accomplish efficient exploration and scientific investigation in the complex deep-sea environment,this study focused on the development of a large-volume,full-sea deep-borne simulation device.Structural design,mechanical analysis,safety verification,simulation and experimental verification of the working process were conducted.The proposed large-volume,full-sea deep-borne simulation device can support the development and testing of the manned capsule over the full depth of the sea and can provide a theoretical and practical basis for the further development of the large-scale,full-depth,super-high-pressure simulation test device.The following were the main results of this study.(1)Based on the required parameters of the underwater simulation experiment of the deep-sea manned submersible,an overall scheme design was developed for the first large-volume,full-sea deep-borne simulation device in China.The basic structure of the simulation device and the working load of its components were determined.The dimensions of the cylinder and frame of the simulation device,pretightening force,and winding layer parameters were calculated based on the digital winding theory.(2)An explicit analytical expression of the stress distribution of the pressure cylinder of the device under the wire-winding condition was proposed.A safety check of the winding layer was performed.The mechanical parameters of the cylinder were calculated based on the Bryce formula and radial shrinkage equation,and the stiffness and stability of the cylinder were checked.The mechanical parameters of the frame column were calculated,and the strength,stiffness,and stability of the frame column were examined.The positions of the stress and strain measurement points on the surface of the component were determined according to the theoretical safety check of the simulation device.(3)The stepless variable tension winding design of the large-volume,full-sea deep-borne simulation device was carried out.Considering the wire-winding process,the force conditions of the pressure cylinder and the frame were analyzed,and the force balance and deformation compatibility equations for the winding process were derived.Subsequently,the initial tensions of the pressure cylinder and frame steel wire winding were calculated,and the steel wire tension data were generated to guide production.To solve the problem of inaccurate tension control in the wire-winding process,a new winding process was proposed,and the dynamic model and state equation of the wire-winding system were established.The control strategy of the whale optimization algorithm PID(WOA-PID)was proposed to design the tension controller to improve the accuracy of tension control.(4)The static and dynamic finite-element models of the large-volume,full-sea deep-borne simulation device were established,and the static,modal,and transient dynamic analyses of the simulation device were performed under different working conditions.The stress distributions of the simulation device in the pretightening and working states were obtained by statics,and the stress distribution characteristics were analyzed.The strain values of each observation point were obtained.These values provided a theoretical reference for the later field stress test.Through the transient dynamic analysis,the influence of spherical crushing on the simulation device under different crushing conditions and different water contents of the ball was obtained.The range of safe water content and the maximum stress value of the main components under the limit condition were obtained.These values help predict the safety of the device during the human-loaded spherical simulation compression test.(5)The technical difficulties in the stress experiments of the large-volume,fullsea deep-borne simulation device were analyzed,and solutions were proposed.The technical scheme of the test experiment was designed.The corresponding experimental system was built,and the stress test experiment was conducted.The measured data show that the strength of the proposed simulation device meets the requirements.Comparison and analysis of the experimental and finite-element calculation data show that the two data are consistent with each other.Thus,this study demonstrates the correctness and accuracy of the finite-element modeling method for the large-volume,full-sea deep-borne simulation device.