An overview of buckling and ultimate strength of spherical pressure hull under external pressure

2010 ◽  
Vol 23 (3) ◽  
pp. 227-240 ◽  
Author(s):  
Binbin Pan ◽  
Weicheng Cui
Keyword(s):  
Ultimate Strength ◽  
External Pressure ◽  
Spherical Pressure

Structural Reinforcement of Viewports in Spherical Pressure Hull for Manned Submersibles

2014 ◽  
Vol 48 (3) ◽  
pp. 17-24 ◽  
Author(s):  
Bhaskaran Pranesh ◽  
Dharmaraj Sathianarayanan ◽  
Sethuraman Ramesh ◽  
Gidugu Ananda Ramadass
Keyword(s):  
Atmospheric Pressure ◽  
Hoop Stress ◽  
Sea Water ◽  
External Pressure ◽  
Element Analysis ◽  
Structural Reinforcement ◽  
Replacement Method ◽  
Axis Of Symmetry ◽  
Spherical Pressure ◽  
Design Pressure

AbstractManned submersibles are underwater vehicles. These vehicles are equipped with an atmospheric pressure casing called a spherical pressure hull, which can accommodate up to three people. The spherical pressure hull facilitates safe passage to high-pressure environments. It has circular openings that serve as viewports to enable underwater viewing and intervention. The regions near the openings are the weakest in the pressure hull and must be reinforced. Reinforcement of the viewports is performed using the area replacement method. The amount of material removed from the viewport opening must be replaced along the axis of symmetry of the opening. This is the minimum amount of material that must be placed along the circumference of the viewports. Reinforced viewports in the pressure hull are analyzed using finite element analysis, and the stresses are classified into primary and secondary stresses. The reinforcements of the viewports are carried out in such a way that the calculated primary and secondary stresses are below the permissible limits.Abbreviations:P ‐ External pressure (design pressure)Dm ‐ Mean diameter of the pressure hullRm ‐ Mean radius of the pressure hullt ‐ Thickness of the pressure hullσ ‐ Hoop stressPy ‐ Pressure at yield strength of the materialPb ‐ Buckling pressureE ‐ Young’s modulus of the materialγ ‐ Poisson’s ratioMSW ‐ Meters of sea water

Reeling Effect on the Ultimate Strength of Sandwich Pipes

2005 ◽  
Author(s):  
Xavier Castello ◽  
Segen F. Estefen
Keyword(s):  
Ultimate Strength ◽  
Numerical Models ◽  
Kinematic Hardening ◽  
External Pressure ◽  
Combined Loading ◽  
Collapse Pressure ◽  
Finite Element Software ◽  
Structural Resistance ◽  
Longitudinal Bending ◽  
Full Scale Tests

Sandwich pipes composed of two steel layers separated by a polypropylene annulus can be used for the transport of oil&gas in deepwaters, combining high structural resistance with thermal insulation in order to prevent blockage by paraffin and hydrates. In this work, sandwich pipes with typical inner diameters of those employed in the offshore production are analyzed numerically to evaluate the ultimate strength under external pressure and longitudinal bending as well as the effect of the reeling installation method on the collapse pressure. Numerical models were developed using the commercial finite element software ABAQUS. The validation was based on experimental results. The analyses for combined loading were performed using symmetry conditions and the pipe was reduced to a ring with unitary length. The analysis of bending under a rigid surface was simulated numerically according to the experiments performed using a bending apparatus especially built for full scale tests. Symmetry conditions were employed in order to reduce the analysis to a quarter of a pipe. Mesh sensitivity studies were performed to obtain an adequate mesh refinement in both analyses. The collapse pressure was simulated numerically either for the pre or post reeling process. Bauschinger effect was included by using kinematic hardening plasticity models. The influences of plasticity and out-of-roundness on the collapse pressure have been confirmed.

Further study on the ultimate strength analysis of spherical pressure hulls

2010 ◽  
Vol 23 (4) ◽  
pp. 444-461 ◽  
Author(s):  
B.B. Pan ◽  
W.C. Cui ◽  
Y.S. Shen ◽  
T. Liu
Keyword(s):  
Ultimate Strength ◽  
Strength Analysis ◽  
Spherical Pressure

Adhesion Effect on the Ultimate Strength of Sandwich Pipes

2006 ◽  
Author(s):  
Xavier Castello ◽  
Segen F. Estefen
Keyword(s):  
Ultimate Strength ◽  
Structural Strength ◽  
Numerical Models ◽  
Maximum Shear Stress ◽  
Experimental Tests ◽  
External Pressure ◽  
Friction Model ◽  
Shear Loads ◽  
Longitudinal Bending ◽  
Contact Models

Sandwich pipes composed of two steel layers separated by a polypropylene annular can be used for deepwater oil&gas transportation. They combine high structural strength to resist external pressure with thermal insulation to prevent blockage by paraffin and hydrate. In this work, experimental tests and numerical models were employed to verify the influence of the inter-layer adhesion on the ultimate strength under external pressure and longitudinal bending of a sandwich pipe prototype. The maximum shear stress obtained from sandwich pipe specimens bonded with a specific adhesive indicated the adhesion levels to be adopted in the numerical simulations. Two contact models were employed to simulate the bonding and slipping conditions between layers, one adopting a friction model and the other including non-linear springs between metal and polymer nodes. The latter is an adapted solution to simulate both tension and shear loads. As expected for a sandwich structure, the structural strength is strongly dependent on the interface stickiness. The analyzed geometry is able to withstand a water depth up to 3,000 meters with a bonding strength corresponding to only 10% of the idealized perfect adhesion condition.

Manufacturing Imperfection Sensitivity Analysis of Spherical Pressure Hull for Manned Submersible

2013 ◽  
Vol 47 (6) ◽  
pp. 64-72 ◽  
Author(s):  
Bhaskaran Pranesh ◽  
Dharmaraj Sathianarayanan ◽  
Sethuraman Ramesh ◽  
Gidugu Ananda Ramadass
Keyword(s):  
Numerical Analysis ◽  
Parametric Design ◽  
External Pressure ◽  
Imperfection Sensitivity ◽  
Element Analysis ◽  
Allowable Deviation ◽  
Buckling Behavior ◽  
Manufacturing Procedure ◽  
Manned Submersible ◽  
Spherical Pressure

AbstractAny pressure hull invariably has imperfections as a result of the manufacturing procedure. Imperfections in a spherical pressure hull are the basis for localized buckling and deformation behavior. Numerical analysis and analytical calculations are carried out to predict the buckling behavior and strength of a pressure hull made of titanium alloy (Ti-6Al-4V) for both perfect and imperfect pressure hulls. Finite element analysis is carried out for different imperfection angles to see the effect on strength and buckling. Results of numerical analysis show that there is considerable reduction in both buckling pressure and strength as a result of imperfections. Hence, allowable deviation due to imperfection for a spherical pressure hull has to be considered for thickness calculations.Abbreviations:P  external pressure (Design pressure)Dm  mean diameter of the pressure hullRm  mean radius of the pressure hullRi  imperfect radius of the pressure hullt  thickness of the pressure hullΔR  imperfect deviationδ  imperfection angleσ  hoop stressPy  pressure at yield strength of the materialPb  buckling pressureE  Young’s modulus of the materialμ  Poisson’s ratioMSW  meters of sea waterAPDL  ANSYS Parametric Design Language

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