EXPERIMENTAL STUDY OF THE INTERACTION OF CORROSION DAMAGE AND OUT-OF-CIRCULARITY IN THE COLLAPSE OF SUBMARINE PRESSURE HULLS

2021 ◽  
Vol 154 (A3) ◽  
Author(s):  
J R MacKay ◽  
M J Smith ◽  
F Van Keulen ◽  
T N Bosman
Keyword(s):  
Linear Trend ◽  
Corrosion Damage ◽  
External Pressure ◽  
General Corrosion ◽  
Geometric Imperfection ◽  
Collapse Pressure ◽  
Compressive Stresses ◽  
Bending Stresses ◽  
Corrosion Pitting ◽  
Corrosion Pits

The effect of corrosion damage on overall collapse strength of submarine pressure hulls was studied experimentally. Ring-stiffened cylinders were machined from aluminium tubing and loaded to collapse under external pressure. In selected specimens, some of the outer shell material was machined away in large single patches, representing general corrosion. Other specimens had many smaller patches, representing corrosion pitting from the outside of the hull, followed by grinding. Large-amplitude out-of-circularity (OOC) was introduced by mechanically deforming selected cylinders. Clusters of artificial corrosion pits were found to have approximately the same effect on collapse pressure as equal-depth general corrosion covering the same region of plating. General corrosion was found to be most severe when it was “in-phase” with OOC, since, during pressure loading, high compressive stresses resulting from corrosion were compounded by compressive bending stresses associated with OOC, and furthermore, the corrosion tended to increase the geometric imperfection itself. On the other hand, out-of-phase corrosion reduced the effect of OOC, while at the same time the thinning-associated compressive stresses were counteracted by local tensile bending stresses associated with OOC, so that strength reductions were correspondingly smaller. Overall collapse pressures for corroded specimens were reduced by, on average, 0.85% for each 1% of shell thinning. That result is based on a linear approximation of the nonlinear relationship between thinning and collapse pressure. The linear trend-line, which was used to account for the experimental scatter, is based on specimens with 13 to 27% shell thinning, and with a variety of corrosion areas and OOC amplitudes.

Experimental Study Of The Interaction Of Corrosion Damage And Out-Of-Circularity In The Collapse Of Submarine Pressure Hulls - Technical Note

2012 ◽  
Vol 154 (A3) ◽  
Keyword(s):  
Linear Trend ◽  
Corrosion Damage ◽  
External Pressure ◽  
Technical Note ◽  
General Corrosion ◽  
Geometric Imperfection ◽  
Collapse Pressure ◽  
Compressive Stresses ◽  
Bending Stresses ◽  
Corrosion Pits

The effect of corrosion damage on overall collapse strength of submarine pressure hulls was studied experimentally. Ring-stiffened cylinders were machined from aluminium tubing and loaded to collapse under external pressure. In selected specimens, some of the outer shell material was machined away in large single patches, representing general corrosion. Other specimens had many smaller patches, representing corrosion pitting from the outside of the hull, followed by grinding. Large-amplitude out-of-circularity (OOC) was introduced by mechanically deforming selected cylinders. Clusters of artificial corrosion pits were found to have approximately the same effect on collapse pressure as equal-depth general corrosion covering the same region of plating. General corrosion was found to be most severe when it was “in-phase” with OOC, since, during pressure loading, high compressive stresses resulting from corrosion were compounded by compressive bending stresses associated with OOC, and furthermore, the corrosion tended to increase the geometric imperfection itself. On the other hand, out-of-phase corrosion reduced the effect of OOC, while at the same time the thinning-associated compressive stresses were counteracted by local tensile bending stresses associated with OOC, so that strength reductions were correspondingly smaller. Overall collapse pressures for corroded specimens were reduced by, on average, 0.85% for each 1% of shell thinning. That result is based on a linear approximation of the nonlinear relationship between thinning and collapse pressure. The linear trend-line, which was used to account for the experimental scatter, is based on specimens with 13 to 27% shell thinning, and with a variety of corrosion areas and OOC amplitudes.

Effect of Steel Properties on Buckling Pressure of Corroded Pipelines

2017 ◽  
Vol 898 ◽  
pp. 741-748 ◽  
Author(s):  
Meng Li ◽  
Hong Zhang ◽  
Meng Ying Xia ◽  
Kai Wu ◽  
Jing Tian Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Yield Strength ◽  
Strain Hardening ◽  
Corrosion Damage ◽  
Element Model ◽  
External Pressure ◽  
Strain Hardening Exponent ◽  
The Finite Element Method ◽  
Collapse Pressure ◽  
Steel Properties

Due to the harsh environment for submarine pipelines, corrosion damage of the pipeline steels is inevitable. After the corrosion damage, pipelines are prone to failure and may cause serious consequences. The analysis of the effects of different steel properties on the collapse pressure of pipelines with corrosion defects is of importance for the option of appropriate pipeline and avoiding accidents. Based on the finite element method, the finite element model of the pipeline with defects under external pressure was built. Firstly, the accuracy of the numerical model was validated by comparing with previous experimental results. The effects of yield strength and strain hardening exponent on collapse pressure of pipelines with different sizes of defect were discussed in detail. Results showed that the yield strength and strain hardening exponent have different influences on collapse pressure: the collapse pressure increases with the increasing yield strength, and the collapse pressure decreases with the increasing strain hardening exponent.

The Sensitivity of Overall Collapse of Damaged Submarine Pressure Hulls to Material Strength

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
John R. MacKay ◽  
Fred van Keulen
Keyword(s):  
Strain Hardening ◽  
Corrosion Damage ◽  
Material Behavior ◽  
Material Strength ◽  
Low Grade ◽  
General Corrosion ◽  
Collapse Pressure ◽  
Cyclic Plastic ◽  
Collapse Strength ◽  
Plastic Loading

Budget and schedule restrictions sometimes require naval submarines to be operated with unrepaired corrosion damage to the pressure hull. It is important to understand the effects of corrosion wastage on the structural capacity of the hull, so that appropriate diving depth restrictions can be imposed if necessary. The current paper presents an experimental study of the interaction of material behavior with corrosion defects, especially with respect to their effect on overall elasto-plastic collapse of pressure hulls. Twenty ring-stiffened cylinders, representative of submarine pressure hulls failing by overall collapse, were machined from high- and low-grade aluminum alloy tubes. Artificial general corrosion damage was introduced in selected specimens by machining away material from the outside of the cylinder shell in rectangular patches of uniform depth. The cylinders were monotonically loaded to collapse under external hydrostatic pressure. One corroded cylinder was repeatedly loaded past the yield limit before the collapse test in order to study the effect of cyclic plastic loading on its ultimate collapse strength. Overall collapse pressures for corroded cylinders with a variety of patch sizes and depths and material strengths were reduced by, on average, 0.85 times the depth of thinning divided by the original shell thickness. The collapse strength of corroded cylinders was found to be more sensitive to the shape of the stress-strain curve than for intact specimens. Higher levels of strain hardening and ductility were found to improve the performance of damaged cylinders. Permanent deformations in the cyclically loaded cylinder, as measured with strain gauges, grew with each constant-amplitude load cycle; however, the additional deformations tended towards zero with increasing number of cycles, and a subsequent collapse test indicated that the cyclic loading did not affect the collapse pressure. The sensitivity of overall collapse to material strength is related to not only the yield stress, but also the plastic reserve of the material; higher levels of strain hardening and ductility increase overall collapse strength of hulls, especially those with general corrosion damage. The effect of a given level of corrosion thinning is less severe for cylinders with relatively greater levels of strain hardening. It is unlikely that cyclic plastic loading of corroded hulls will lead to premature collapse at a load level below the monotonic collapse pressure.

Assessment of Lower Regions of Pressure Vessels Subjected to Corrosion Wall Thinning

2010 ◽  
Author(s):  
Colin Madew ◽  
John Sharples ◽  
Richard Charles ◽  
Godfrey Smith
Keyword(s):  
Corrosion Damage ◽  
Pressure Vessels ◽  
Nuclear Industry ◽  
Pressure Solution ◽  
Finite Element Models ◽  
General Corrosion ◽  
Pressure Loading ◽  
Collapse Pressure ◽  
Symmetric Finite Element ◽  
Safe Working

Pressure vessels are common components of plant currently in operation within the nuclear industry and elsewhere. Their assessment and maintenance is of paramount importance to the integrity and safe working of the plant. Often these pressure vessels contain highly corrosive substances, which over time, cause deterioration in the integrity of the vessel. Current codes and standards such as BS7910, API579 and FITNET provide guidance on the assessment of cylinders and pipes with localised and general corrosion, but to date, no such guidance is available for complete vessels, where the corrosion occurs in the lower region of the vessel, e.g. where the base of a vessel is connected to the vessel wall. This paper investigates the resistance to plastic collapse, from internal pressure loading, of flat based cylindrical pressure vessels, where the base and wall thicknesses are considerably different due to corrosion damage. A ‘First Estimate’ or conservative lower bound collapse pressure solution for such vessels is described. The solution has been derived using axi-symmetric finite element models with varying degrees of general corrosion thinning.

“First Estimate” Plastic Collapse Solutions for Flat and Torispherical Ended Pressure Vessels Subjected to Extensive Corrosion Wall Thinning

2012 ◽  
Author(s):  
Colin Madew ◽  
Mark Wilkes ◽  
Richard Charles ◽  
Ian Symington
Keyword(s):  
Preceding Paper ◽  
Pressure Vessels ◽  
Graphical Form ◽  
General Corrosion ◽  
Plastic Collapse ◽  
Collapse Pressure ◽  
Fatigue Initiation ◽  
Wall Thinning ◽  
Geometric Discontinuities ◽  
Corrosion Pits

Plants in safety-critical industries comprise of a number of different components, including various sizes of pressure vessels, and their integrity is often paramount to the safe running of the plant. In many cases these vessels can contain highly corrosive liquids, which, over time can lead to a degree of thinning in the vessel walls. With corrosion wall-thinning come a number of issues, including a reduced plastic collapse load of the vessel and possible fatigue initiation from corrosion pits. Since failure of these vessels could lead to catastrophic failure and the escape of highly corrosive material, the assessment and maintenance of these vessels is of high importance. Current Fitness for Service Codes and Standards provide guidance on the assessment of cylinders and pipes with localized wall thinning and general corrosion, with respect to plastic collapse. This guidance, however, is not currently applicable to components with geometric discontinuities (the pressure vessel base-wall junction). This paper follows a preceding paper presented at the ASME PVP Conference 2010 which derived “First Estimate” plastic collapse solutions for flat-based, corroded, pressure vessels. These solutions have been expanded through further finite element studies to accommodate the estimation of plastic collapse in tori-spherical headed pressure vessels subjected to extensive corrosion wall-thinning. Results from this study are presented in graphical form to enable a quick and efficient first estimate of the effect of wall thinning on the collapse pressure to be attained.

Lifetime Enhancement of Propulsion Shafts Against Corrosion-Fatigue by Laser Peening

2018 ◽  
Author(s):  
Lloyd A. Hackel ◽  
Jon E. Rankin
Keyword(s):  
Corrosion Fatigue ◽  
Fatigue Testing ◽  
Salt Water ◽  
Fatigue Cracks ◽  
Water Immersion ◽  
High Energy ◽  
General Corrosion ◽  
Laser Peening ◽  
Corrosion Pits ◽  
Deep Pits

This paper reports substantially enhanced fatigue and corrosion-fatigue lifetimes of propulsion shaft materials, 23284A steel and 23284A steel with In625 weld overlay cladding, as a result of shot or laser peening. Glass reinforced plastic (GRP) coatings and Inconel claddings are used to protect shafts against general corrosion and corrosion pitting. However salt water leakage penetrating under a GRP can actually enhance pitting leading to crack initiation and growth. Fatigue coupons, untreated and with shot or laser peening were tested, including with simultaneous salt water immersion. Controlled corrosion of the surfaces was simulated with electric discharge machining (EDM) of deep pits enabling evaluation of fatigue and corrosion-fatigue lifetimes. Results specifically show high energy laser peening (HELP) to be a superior solution, improving corrosion-fatigue resistance of shaft and cladding metal, reducing the potential for corrosion pits to initiate fatigue cracks and dramatically slowing crack growth rates. At a heavy loading of 110% of the 23284A steel yield stress and with 0.020 inch deep pits, laser peening increased fatigue life of the steel by 1370% and by 350% in the corrosion-fatigue testing.

External Weld Overlays for Repair of Pressure Components

2003 ◽  
Author(s):  
Shane J. Findlan
Keyword(s):  
Weld Metal ◽  
Corrosion Damage ◽  
Microbiologically Influenced Corrosion ◽  
General Corrosion ◽  
Degradation Mechanisms ◽  
Weld Overlay ◽  
Metal Deposit ◽  
Wall Thinning ◽  
Erosion Corrosion ◽  
Weld Overlays

External weld metal deposit overlays have been successfully implemented in industry as both temporary and permanent repair for the restoration of thinning or degraded steel piping. Pressure components systems suffer from numerous degradation mechanisms, including microbiologically influenced corrosion (MIC), erosion-corrosion damage (EC), fatigue, and general corrosion. The magnitude of the damage induced in the component determines whether a weld overlay repair can be successfully applied to restore the component’s integrity. This paper addresses the use of weld overlays for repair of pressure components degraded by wall thinning due to corrosion, erosion-corrosion, MIC and other mechanisms.

scholarly journals Research of Supporting Ability and Prediction of Residual Life of Casing Pipes at General Corrosion Damage of Inner Surface

2021 ◽  
Vol 225 ◽  
pp. 02002
Author(s):  
Natalia Fedorova ◽  
Yulianna Dimitriadi ◽  
Nikita Ryapolov
Keyword(s):  
Residual Life ◽  
Corrosion Damage ◽  
General Corrosion ◽  
Corrosion Depth ◽  
Inner Pressure ◽  
Nominal Thickness ◽  
Inner Surface ◽  
To Receive

The detection and the measuring of the developing damages must be accompanied by evaluation of the supporting ability of the design in terms of the increasing size of a defect. If the type of damage is dominant one on the further period of the operation, so the received functional dependences can be used to predict a residual life of the designs. As illustrated by the casing pipes of 168.3 mm diameter, where the dominant damage is the general corrosion of the inner surface, the algorithm to receive the expression for the calculation of coefficients of the lowering of the supporting ability to the excessive inner pressure in the function of the nominal thickness of pipes wall and corrosion depth is shown. The algorithm of the application of the received expression to calculate the residual life of the damaged casing pipes is given.

Clamped torispherical shells under external pressure — some new results

1988 ◽  
Vol 23 (1) ◽  
pp. 9-24 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Failure Mode ◽  
External Pressure ◽  
Spherical Cap ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Modes Of Failure ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Initial Geometric Imperfections ◽  
The One

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells. A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.

Initiation of Propagating Buckles From Local Pipeline Damages

1984 ◽  
Vol 106 (1) ◽  
pp. 79-87 ◽  
Author(s):  
S. Kyriakides ◽  
C. D. Babcock ◽  
D. Elyada
Keyword(s):  
Parametric Study ◽  
External Pressure ◽  
Maximum Diameter ◽  
Minimum Diameter ◽  
Geometric Imperfection ◽  
Geometric Characteristics ◽  
Offshore Pipeline ◽  
Initiation Pressure ◽  
The Subject

The paper deals with the subject of initiation of a propagating buckle in an offshore pipeline. If the external pressure is high enough, then a propagating buckle can be initiated by locally denting the pipe. Such a buckle will propagate at any pressure above the propagation pressure of the pipe. The pressure at which a local geometric imperfection transforms itself into a propagating buckle is known as the initiation pressure. This pressure depends on the geometric characteristics of the damage. The paper restricts itself to a parametric study of damages produced by point, knife and plate indentors. It is found that the geometry of these types of damages can be well represented by the ratio of minimum diameter: maximum diameter of the most damaged section.

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