| To explore the vast ocean world,marine engineering equipment is an indispensable condition,and its importance has been explained in made in China 2025,which indicates that the development of the ocean can greatly promote the economic development of the country,and on the other hand,it also shows the determination and strength of China's ocean development.Whether it is a manned submersible or an unmanned submersible,they all have a very important component,that is,the pressure shell.However,the existing pressure shell has some disadvantages,such as unreasonable structure,difficult processing and high defect sensitivity,while the corrugated cylindrical pressure shell shows amazing compression characteristics.And its compressive properties are closely related to the material parameters,geometric parameters and defect amplitude of the corresponding model.Therefore,in this paper,the nonlinear buckling,material parameters,geometric parameters and defect size of corrugated cylindrical pressure shell are discussed in detail as follows:(1)Firstly,according to BSI(pd5500)(2009)standard,two cylindrical shells are designed(one is ordinary cylindrical pressure shell,the other is circumferential corrugated cylindrical pressure shell).Through linear buckling analysis,it can be seen that the buckling load of corrugated cylindrical pressure shell is far greater than that of ordinary cylindrical pressure shell,which shows that the buckling load of corrugated cylindrical pressure shell is significantly increased;the higher the meridional curvature of shell is In addition,the reduction of the bending wave is caused by the extremely high rigidity of the corrugated cylindrical pressure shell.From the equilibrium path of two cylindrical shells,it can be seen that the first yield point of the ordinary cylindrical pressure shell is located behind the critical buckling point in the equilibrium path,which indicates that the imperfect ordinary cylindrical pressure shell is unstable in the elastic range,which is consistent with the ordinary cylindrical pressure shell The equilibrium curve of the corrugated cylindrical pressure shell also shows the characteristics of instability.Due to the enhancement of the axial stress on the corrugated area,the critical buckling mode and post buckling mode are all in the form of axisymmetric failure.The buckling of the corrugated cylindrical pressure shell occurs in the elastic-plastic range,which proves that the nonlinear calculation greatly improves the calculation accuracy.With the increase of defect size,the nonlinear buckling load of corrugated cylindrical pressure shell decreases slightly,which shows that the sensitivity of corrugated cylindrical pressure shell to initial geometric defects is much smaller than that of ordinary cylindrical pressure shell.(2)Then,the influence of three kinds of corrugations: sine wave,triangle wave and semicircle wave on the buckling of cylindrical shell is analyzed,and the results show that the cylindrical shell with sinusoidal circumferential corrugations has the best bearing capacity;the linear elastic buckling load of the three kinds of corrugations increases with the increase of modal order,and the linear buckling load of the cylindrical shell with triangular circumferential corrugations is the smallest,and the linear buckling load of the cylindrical shell with sinusoidal circumferential corrugations is the least According to the nonlinear buckling analysis,the buckling value does not change with the increase of the defect,which indicates that no matter what kind of corrugated pressure shell is sensitive to the defect;furthermore,it is found that the maximum stress of each pressure shell at the critical buckling point is greater than the material yield stress(313.7)MPA),which shows that all three kinds of corrugated shells buckle in the elastic-plastic range;similarly,the critical value of the corrugated cylindrical shell with triangular section is the smallest,and the critical value of the corrugated cylindrical shell with sinusoidal section is the largest,so the research on the corrugated cylindrical shell with sinusoidal section is carried out.(3)With the increase of the amplitude of sinusoidal ripple,the nonlinear buckling load of the circumferential sinusoidal ripple cylindrical pressure shell increases first and then decreases,and its buckling value changes little with the increase of its own defects,when the amplitude of ripple s = 2.5 The results show that the three buckling positions of the cylindrical shell are in the middle of the cylindrical shell,and the post buckling modes show typical pit forms;the nonlinear buckling of the equal mass cylindrical shell The load value is more than 4 times of the ordinary cylindrical shell,and the nonlinear buckling load value of the equal volume sine wave shaped cylindrical pressure shell is more than 5 times of the ordinary cylindrical shell,which fully shows the superiority of the bearing capacity of the sine wave shaped cylindrical pressure shell.Through the study of the geometric parameters and material parameters of the corrugated cylindrical pressure shell,it is found that the bearing capacity of the corrugated cylindrical pressure shell increases with the increase of the diameter to wall thickness ratio In addition,the critical value increases linearly with young's modulus and decreases linearly with the increase of yield strength.(4)Finally,through the contour inspection of 3D optical scanner and the non-destructive inspection of ultrasonic thickness gauge,it is found that the completion of the corrugated cylindrical pressure shell is relatively high,which has a high consistency with the ideal model.The results show that with the increase of the amplitude of the sine ripple,the buckling load of the circumferential sine ripple cylindrical pressure shell increases first and then decreases,which is related to the yield strength of the corrugated cylindrical shell structure and materials,and the buckling resistance of any corrugated cylindrical pressure shell is better than that of the ordinary cylindrical shell(the amplitude of the ripple is s = 0 mm);the numerical calculation of the real corrugated cylindrical pressure shell shows that the buckling load of the corrugated cylindrical shell increases first and then decreases The failure position is basically consistent with the test results.Through the strength analysis of the ideal corrugated cylindrical pressure shell,it is found that when the corrugated amplitude s = 0 mm,2.5 mm,the corrugated cylindrical pressure shell will have normal buckling failure;when the corrugated amplitude s = 5 mm,10 mm,15 mm,the corrugated cylindrical pressure shell will have strength failure. |
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