Research On The Adjustment Method Of Hole Area Of Residual Stress In Deep-sea Pressure Spherical Shell

In the four strategic areas of human development(land / sea / air / sky),the ocean is the second largest space,which is the most realistic and most promising strategic space.The exploration and development of deep sea resources is of great significance to promoting Chinese economic and enhancing comprehensive national strength.Manned submerseble is an important technical and equipment to support the exploration and development of deep sea resources and to develop deep sea scientific research and to launch deep sea engineering operations.Submersible core area of the manned pressure spherical shell commonly used titanium alloy in the current international,welding forming technology of melon flapper,however,the welding residual stress of the spherical shell has a great negative impact on the compressive strength and safety.Therefore,it is of great practical and strategic significance to study the welding residual stress and its adjustment method of deep-sea pressure spherical shell,which is of great significance to improve the quality of deep-sea equipment and deep-sea development capability.In this paper,based on the theory of welding finite element combined with the welding test and external pressure test,the welding residual stress and its adjustment in the open area of deep sea spherical shell are studied.First,according to the laboratory condition and project ability,combining the strength theory and stability theory to design the test model.Second,based on the welding finite analysis theory,the simulation of the welding simulation and the external pressure test of the model is carried out,comparing the residual stress and its adjustment of the model test and numerical simulation,and it is proved that the method of numerical simulation is used to verify the welding process and the external pressure test of spherical shell is feasible;Finally,numerical simulation is used to study the welding residual stress in different welding methods-narrow gap welding and electron beam welding,and the difference of welding residual stress after external pressure treatment,then evaluating the influence of two different methods and adjusting methods on the safety of spherical shell.The main research contents of this paper are as follows:(1)Study on the finite element theory of welding and the stability of spherical shell.To study the theory of finite element simulation,a simplified simulation of designing spherical shell welding,at the same time,the simplified model and theoretical of welding temperature field and stress field are studied.The method and theory of the stability of the test model areintroduced,including the theoretical formula of spherical shell stability,linear buckling analysis and nonlinear buckling analysis,which lays the theoretical foundation for the design of the experimental model.(2)The design and verification of the pressure spherical shell test model.The preliminary design of the test model based on the standard of CCS,and the strength of the test model is verified by the finite element method,Then using GL specification to check the critical instability of experimental model.At the same time,the linear buckling and nonlinear buckling of the test model were carried out by finite element analysis.Finally,the strength and stability of the test model are verified to meet the design requirements of the experimental model.(3)The contrastive study of numerical simulation and experimental on welding residual stress and its adjustment in spherical shell.Firstly,the welding temperature fields of annular welds in the open area of the model are simulated,then simulate the welding stress field.On this basis,the external pressure of different load is adjusted to adjust the residual stress and get the change rule.Then the residual stress measurement and external pressure test were carried out to test the residual stress before and after the external pressure test.Finally,comparing the measured values and numerical simulation values of the pressure spherical shell,which verified the feasibility of numerical simulation of welding and external pressure in the spherical shell.(4)A comparative study on welding residual stress and its adjustment effect of pressure spherical shell with narrow gap welding and electron beam welding.Using the method of numerical simulation,comparising the residual stress distribution in different welding modes-narrow gap welding and electron beam welding,then the modles made by two welding methods are respectively subjected by external pressure treatment and study the effect of residual stress adjusting.Finally,the effect of different welding methods about the residual stress and the effect of the external pressure.