Buckling Analysis And Experimental Study On Egg-shaped Pressure Shell With Variable Wall Thickness

The report of the 18 th National Congress of the Communist Party of China mentioned the need to improve the development and utilization of marine resources,which indicates that the development of the marine economy is very important for China's economic development.The submersible is one of the most important tools for marine exploration,and the pressureresistant casing is one of the most important equipment for the submersible.The existing pressure-resistant shell has the defects of unreasonable structure and large defect sensitivity.The newly proposed egg-shaped bionic pressure-resistant shells exhibit good pressure resistance characteristics,but its pressure resistance has a certain gap with the existing pressure-resistant shell.Therefore,this paper proposes a new type of egg-shaped bionic pressure-resistant shell with variable wall thickness and it has better pressure resistance and higher material utilization.In this paper,theoretical analysis,numerical calculation and proportional test are combined to interpret the buckling characteristics of thickened eggshaped pressure shell.The main research contents and conclusions are as follows:(1)First according to the NR equation,the contour of the egg-shaped pressure shells with variable wall thicknesses are designed and combined with the unit deformation displacement of the bionic eggshell to obtain the maximum deformation displacement of the fracture.Then the wall thickness distribution are designed according to the Mushtari formula and the strength and buckling theory.Optimizing the thickness-ratio parameters to explore the distribution ratio of wall thickness,and to find an optimal wall thickness distribution for the influence of the strength and stability of the egg-shaped pressure-resistant shell.Thickened egg-shaped pressure shells with excellent parameters are L1 / L =0.25.(2)The numerical model of the egg-shaped pressure shells with ariable wall thicknesses are established to analyze the linear elastic buckling and consider the influence of multimodality on the elastic buckling of the line and compare it with the uniform eggshell.The nonlinearity of the egg-shaped pressure shells with ariable wall thicknesses are analyzed.Nonlinear buckling loads and instabilities modes in the case of buckling and multi-models.The study shows that the linear elastic buckling load of the egg-shaped pressure shells with variable wall thicknesses are 1.14 times that of the thick egg-shaped pressure shell;under the same conditions,the nonlinear buckling load of the egg-shaped pressure shells with variable wall thicknesses are the uniform egg shape resistance.The shells are 1.05~1.12 times.Combined with the actual working conditions,the egg-shaped pressure-resistant shells with variable wall thicknesses are suitable for working conditions of 1~4km;the equal-thick eggshaped pressure-resistant shells are more suitable for working environment above 5km working condition.(3)On the basis of the egg-shaped pressure-resistant shells with variable wall thicknesses,an open-hole thickened egg-shaped pressure-resistant shell with a hole diameter of 100 mm is designed,and the height of the upper wall and the height of the lower wall of the opening are designed according to the ship's classification society specification.The orthogonal test method was used to investigate the influence of geometric parameters such as wall thickness on the buckling characteristics of the thickened egg-shaped pressure shells and the numerical analysis was carried out.From the perspective of three mechanical properties of the shelsl to interpret its influence law,it concludes: surrounded by the wall thickness of the main factors affecting thickened shell opening.(4)The numerical analysis results were verified by experiments,and the mature 3D printing technology was used to produce a resin scale model with higher precision.The egg shell has a high degree of completion and a high consistency with the ideal model.The stability of the eggshells with variable wall thicknesses are better than that of the thick egg shells.The results of hydraulic test and numerical analysis are similar.The test results are closer to the linear elastic buckling solution in numerical analysis.The buckling failure mode of egg shells occurs in the middle of the equator to form a fracture surface,and numerical analysis forms pits in the middle of the egg shell.The results are consistent;the metal proportional test model using machining technology has a high test reference value,and the test results are in good agreement with the nonlinear buckling results in the numerical analysis.The water pressure damage form is formed at the equator.The pit,which is consistent with the numerical solution.