Composite over-wrapped pressure vessel (COPV) with ultra-thin metal liner and high strength carbon fiber reinforced plastic (CFRP) structure was widely used in space system. Meanwhile, there are some difficulties in the calculation of COPV stress-strain state related to the elastic-plastic liner and elastic composite. In this paper a novel design theory was proposed for calculating stress distribution in the bi-material COPV and determining the optimal thickness parameters of COPV based on traditional grid theory optimization. This new theory named Parameters Correspondence Relationship Structure Design Method (PCRSDM) can increase the design precision and structure performance factor of COPV compared to traditional grid theory. The correct models of mechanical characteristic between liner and CFRP are established from the view of optimized grid theory, the present theory is useful to develop a theoretical framework to calculate and design the COPV double shells. The COPV stress-strain behavior is also systemically studied by the ANSYS finite element analysis (FEA), the results show good agreement between FEA simulation and PCRSDM calculation. Both FEA and PCRSDM can meet the design requirements of COPV. A complete design, development and qualification testing of a specialized COPV used to satellite propulsion system was successfully conducted to verify the COPV design in terms of PCRSDM and FEA, the result show that PCRSDM is suitable for the design of COPV.
To meet the application requirements of zero boil-off storage of cryogenic liquid krypton propellant in the process of completing deep space exploration missions by electric propulsion system, it is important to study the thermodynamic changes in cryogenic liquid krypton tanks under different environments. The gas phase and liquid phase material model of krypton working fluid, the gas-liquid phase change model at the interface layers, and the heat transfer process between the wall and the internal fluid are established by ANSYS-Fluent. The energy source term, gas phase, liquid phase mass source term, and phase change saturation temperature in the liquid krypton cryogenic tank are defined. This paper’s three influencing factors of gravity, initial liquid filling rate, and wall heat leakage are simulated and analysed. The results show that: (1) The self-pressurization rate significantly rises as the wall heat flux rises, and the gas-liquid interface drops less quickly. The pressure and temperature in the tank are also increasing at the same liquid level. (2) In the normal gravity environment, the bigger the filling rate, the lower the corresponding self-pressurization rate. (3) In the process of variable gravity, the gas pressurization rate in the cryogenic liquid krypton tank falls with the decrease of gravity.
In the present study, TA1 titanium alloy sheets with a thickness of 0.8mm were welded by electron beam welding. Microstructure of the welded region was investigated using optical microscope and electron backscattered diffraction. Then, the tensile test was conducted to analyse the tensile behavior of the welded sheets as well as the fractography of the fracture surfaces. It is shown that the mean grain size in the heat-affected zone is smaller than that in the fusion zone and base material. The strength of the base metal is lower than that of the fusion zone and heat-affected zone. The average values of the yield strength, tensile strength and elongation of the tensile specimens are 224MPa, 335MPa and 35%, respectively. In addition, the tensile specimens of the welded sheets suffer both ductile and brittle deformation during the tensile tests.
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