Study On Hatch Cover And Drive Mechanism For Full-ocean-depth Manned Submersible

With the rapid development of China's economy in the past 30 years,more and more land resources have been gradually exploited and excavated.This also led to the existing land resources no longer meeting the needs of modern development,so more and more countries are looking to developing ocean,which also promoted the rapid development of marine equipment.As one of the most advanced marine expedition equipment,the deep-sea manned submersible can carry scientists to the deepest point of the Mariana Trench in the world to complete observation and sampling tasks.Based on the needs of research and development of "Rainbow Fish",a full-ocean-depth manned submersible,this thesis focuses on the development of hatch and opening/closing mechanisms of manned cabin.The design of the hatch is based on the determination of the spherical hull parameters of the manned cabin and the structural form of the hatch enclosure.The “Rainbow Fish” manned submersible uses maraging steel as the spherical hull material for the manned cabin,while the new formula in the current design specification of the China Classification Society(CCS)cannot cover the design for the deep-sea manned cabin made of maraging steel.To determine the spherical hull parameters,therefore,first of all,this thesis verifies the feasibility of the current specification for the design of the spherical hull made of maraging steel by collapse test on a model sphere.The test was conducted in the Hadal Science and Technology Research Center of Shanghai Ocean University.The stress-strain relationship and ultimate strength of the model were obtained and compared with the numerical calculation results,and proved the rationality of designing the manned cabin of maraging steel with the existing specifications.Based on this design method,the spherical hull parameters of the manned cabin were determined.At the same time,based on the existing experience and specifications of the manned submersibles “Jiaolong” and “Mir”,the structure of the hatch enclosure was initially designed.Based on the determination of the spherical hull parameters and the structural form of the hatch enclosure,the design of hatch was carried out combining the experience of domestic and international deep-sea submersibles and the specifications of ship classification society.Its strength and stability are checked.Numerical calculations by finite element software ABAQUS are applied to analyze the key technical problems such as contact stress and deformation between the hatch and hatch enclosure.The effects of different safety factors,friction coefficients,and opening cut angles on contact stress are analyzed,and results show that the friction coefficient has a greater influence on contact stress comparing to other influential parameters.The sealing of the hatch cover is one of the key technologies that affects the safety.Different sealing methods and sealing grooves are compared,and the seals are analyzed using finite element software ANSYS.Results show that the pressure of the sealing contact surface is greater than the pressure of the medium,and the shear stress on the sealing ring is smaller than its shear strength,which can ensure the reliability of the sealing.The selection of the height and width of the rectangular sealed groove under different compression ratios and different shrinkages is calculated,which can provide reference for the groove design of the seal ring diameter in the same state in the later design period;at the same time,different compression ratios and media pressures are obtained.Under the effect of the initial preload,with the increase of the compression rate,the maximum Von-Mises stress changes from the initial shape to the dumbbell shape and then to the center region,indicating that the failure region of the seal ring may exist in pre-compression region of the dumbbell area or middle area;Under the water pressure,the maximum Von-Mises stress of the sealing ring begins to move toward the gap side of the groove in contact with the sealing surface,and the middle area is a low stress area,indicating that the sealing ring may fail in the gap.Due to the fact that the hatch cover of manned submersible weighs hundreds of kilograms,it is difficult to open it directly by manpower.The opening/closing mechanism can balance the torque for making it easy to open the hatch cover.When the hatch cover is opened,the spring force of the torsion bar spring in the opening/closing mechanism assists the extra-vehicle personnel to open it;when the hatch cover is closed,the gravity is balanced again through the opening/closing mechanism to prevent the sudden drop of the hatch cover and the damage the hatch cover.In this thesis,the theoretical analysis of the gravity-balanced opening/closing mechanism is carried out,and the function and reliability of the opening and closing mechanism are verified through the processing of the experimental prototype.