Collapse of Worn Casing

1977 ◽  
Vol 99 (1) ◽  
pp. 208-214 ◽  
Author(s):  
C. E. Murphey
Keyword(s):  
Yield Strength ◽  
Lower Bounds ◽  
Wall Thickness ◽  
Axial Load ◽  
External Pressure ◽  
Upper And Lower Bounds ◽  
Percentage Reduction ◽  
Steel Tubes ◽  
Collapse Pressure ◽  
Severe Wear

Collapse tests were performed on one-in. dia steel tubes with flats milled on the exterior to simulate worn casing. External pressure and axial load were applied to the tubs having a range of wall thickness, yield strength, and degree of wear. Empirical correlation of the data and comparison with elastic collapse calculations indicate the percentage reduction in collapse pressure due to wear. This reduction is predictable within upper and lower bounds. While the milled external flat may not accurately simulate severe internal wear, the correlation is adequate for less than severe wear to give an indication of remaining strength.

Free bending characteristics of sheathed spiral strands under cyclic loading

1992 ◽  
Vol 27 (4) ◽  
pp. 219-226 ◽  
Author(s):  
M Raoof ◽  
Y P Huang
Keyword(s):  
Lower Bounds ◽  
Axial Load ◽  
Flexural Rigidity ◽  
Large Diameter ◽  
External Pressure ◽  
Plane Section ◽  
Upper And Lower Bounds ◽  
Radius Of Curvature ◽  
Floating Platform ◽  
Free Bending

A theoretical insight is given into the non-linear free bending characteristics of axially preloaded and large diameter sheathed spiral strands experiencing high external hydrostatic pressure in, for example, deep water floating platform applications. The theoretical model takes geometrical non-linearities and interwire friction fully into account. It is capable of estimating variations of strand plane-section bending stiffness, ( EI)eff, and hysteresis as a function of the imposed radius of curvature, magnitude of the external pressure, and level of mean axial load. An oversight in a previously reported analytical model for following the reductions in strand flexural rigidity due to interlayer slippage has also been identified and subsequently corrected. In addition, the corrected model (which assumed small deflections) has been extended to cover geometrical non-linearities due to changes in lay angle and helix radius. Numerical results are presented for a large diameter (102 mm OD) sheathed spiral strand experiencing various levels of mean axial load and external pressure. In particular, it is shown that under the plane-section bending assumption, the upper and lower bounds to ( EI)eff are, for all practical purposes, independent of the magnitude of mean axial load and external pressure. Moreover, the maximum possible values of radii of curvature associated with which plane-section bending is possible, have been identified in all cases. It is believed that even in the presence of interlayer slippage, the damping model (which is based on plane-section bending) offers reasonable and useful lower bounds to a strand's specific damping which should prove of value in certain applications involving cable dynamics.

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.

Improved Prediction of External Pressure Collapse of Seamless Pipe

2009 ◽  
Author(s):  
Josef Navarro ◽  
Philip Cooper
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Design Method ◽  
External Pressure ◽  
Thickness Variation ◽  
Seamless Pipe ◽  
Line Pipe ◽  
Collapse Pressure ◽  
Average Wall Thickness ◽  
Improved Design

Seamless pipe typically features well controlled average wall thickness around its cross-section, but is prone to significant local thickness variation arising from the manufacturing process. Pipeline design codes, such as DNV OS-F101, provide little guidance on how to treat thickness variation whilst designing for collapse resistance. Standard practice is to consider minimum wall thickness across the whole cross-section, an assumption that two dimensional finite element simulations have proven conservative. This justifies the need for an improved design method. A program of simulations has been carried out to investigate the effect of wall thickness variation on collapse pressure. A modification to the DNV OS-F101 collapse design equation using average wall thickness over the whole crossection together with a fabrication factor is presented based on the results of this study. The fabrication factor de-rates the collapse pressure according to the amount of thickness variation present. The correction has been calibrated for thickness variations up to the maximum permitted by typical line pipe specifications. A number of FE trials demonstrate that the proposed formula predicts simulated collapse pressures with 98% accuracy. Adopting this method could provide significant wall thickness savings for deep water flowlines which in turn could lead to a reduction in steel costs and transportation and lay vessel requirements.

Examination of Commercial Casing Collapse Strength Under Axial Loading

1982 ◽  
Vol 104 (4) ◽  
pp. 343-348 ◽  
Author(s):  
T. Tamano ◽  
Y. Inoue ◽  
H. Mimura ◽  
S. Yanagimoto
Keyword(s):  
Axial Load ◽  
Axial Stress ◽  
Axial Loading ◽  
External Pressure ◽  
Plastic Collapse ◽  
Slight Effect ◽  
Collapse Pressure ◽  
Minimum Value ◽  
Collapse Strength ◽  
Casing Collapse

Collapse testing of commercial API grade 7-in. casing was conducted under combined external pressure and axial load. The measured collapse pressure was considerably higher than the API minimum value, especially for the large D/t ratio, as expected. For the casings of large D/t ratio, the measured collapse pressure was a little smaller than the theoretical value for ideal pipe and the axial stress had a slight effect on the collapse pressure. In the range of plastic collapse, the measured collapse pressure was not less than the yield pressure for ideal pipe except near the boundary of the elastic and plastic collapse ranges.

Bounds for the Natural Frequencies of a Simply Supported beam Carrying a Uniformly Distributed Axial Load

1967 ◽  
Vol 9 (2) ◽  
pp. 149-156 ◽  
Author(s):  
G. Fauconneau ◽  
W. M. Laird
Keyword(s):  
Lower Bounds ◽  
Axial Load ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Upper Bounds ◽  
Upper And Lower Bounds ◽  
Simply Supported Beam ◽  
Simply Supported ◽  
Distributed Load ◽  
Made In

Upper and lower bounds for the eigenvalues of uniform simply supported beams carrying uniformly distributed axial load and constant end load are obtained. The upper bounds were calculated by the Rayleigh-Ritz method, and the lower bounds by a method due to Bazley and Fox. Some results are given in terms of two loading parameters. In most cases the gap between the bounds over their average is less than 1 per cent, except for values of the loading parameters corresponding to the beam near buckling. The results are compared with the eigenvalues of the same beam carrying half of the distributed load lumped at each end. The errors made in the lumping process are very large when the distributed load and the end load are of opposite signs. The results also indicate that the Rayleigh-Ritz upper bounds computed with the eigenfunctions of the unloaded beam as co-ordinate functions are quite accurate.

Buckling and Unstable Collapse of Seamless Pipes and Tubes

2010 ◽  
Author(s):  
F. Van den Abeele ◽  
J. Bar ◽  
S. Jakani
Keyword(s):  
Yield Stress ◽  
Wall Thickness ◽  
Compressive Loading ◽  
External Pressure ◽  
Pipe Production ◽  
Transition Range ◽  
Collapse Pressure ◽  
Initial Imperfections ◽  
Collapse Resistance ◽  
Wide Range

Deepwater pipelines and high pressure casing and tubing are prone to buckling and unstable collapse under compressive loading and external pressure. The most important parameters governing the unstable collapse behaviour of perfectly round pipes and tubes are the circumferential yield stress of the material, the Young’s modulus and the ratio of diameter over thickness (D/t). Initial imperfections in the geometric shape of the pipe, like wall thickness variations or ovality, can have a pronounced influence on the collapse resistance of a pipe. Local dents can reduce the collapse pressure significantly, and trigger propagating buckles along the line. In this paper, buckling and unstable collapse of seamless pipes and tubes are studied. First, collapse pressure experiments for High Collapse Casing grades L80HC and P110HC are presented, showing that the seamless pipe production at ArcelorMittal Tubular Products in Ostrava (Czech Republic) is under tight quality control and complies with the API standards. Then, the critical collapse pressure is calculated for different scenarios. Depending on the ratio of diameter to wall thickness, four regimes are identified: yielding collapse, followed by plastic collapse, a transition range, and finally elastic collapse. For each condition, closed form expressions are derived for the critical collapse pressures. In addition, simplified design equations are reviewed to quickly estimate the collapse pressure. Then, the influence of initial imperfections on the collapse resistance is studied. Both the effects of geometric imperfections (ovality and wall thickness eccentricity) and material properties (especially yield stress and residual stresses) are addressed. In the end, an enhanced design equation is proposed to predict the critical collapse pressure of dented seamless pipes. This equation is validated by collapse experiments, can account for different initial imperfections, and is valid for a wide range of D/t ratios.

Collapse of Deepwater Pipelines

1988 ◽  
Vol 110 (1) ◽  
pp. 1-11 ◽  
Author(s):  
M. K. Yeh ◽  
S. Kyriakides
Keyword(s):  
Wall Thickness ◽  
External Pressure ◽  
Full Scale ◽  
Stress Strain ◽  
Steel Tubes ◽  
Geometric Imperfections ◽  
Circular Shape ◽  
Geometric Deviations ◽  
Initial Geometric Imperfections ◽  
Grade Steel

The paper describes a series of full-scale collapse experiments using X-42 and X-65 grade steel tubes. The initial geometric imperfections of the tubes were measured using a specially designed scanning facility prior to collapsing them under external pressure. Geometric deviations from a circular shape were recorded at 90 points around the circumference. The wall thickness was also recorded at the same points. At least 31 circumferential scans were made over lengths of 9 diameters. The stress-strain characteristics in the axial and circumferential directions were measured for each tube. The measured parameters were used to calculate numerically the collapse pressures of the tubes. The biggest deviation between the experimental and calculated values was less than 8 percent. These are compared with the results obtained from the same analysis using various idealized imperfection measures.

Collapse Capacity of UOE Deepwater Linepipe

2011 ◽  
Author(s):  
Olav Aamlid ◽  
Leif Collberg ◽  
Simon Slater
Keyword(s):  
Heat Treatment ◽  
Yield Strength ◽  
Wall Thickness ◽  
Detrimental Effect ◽  
External Pressure ◽  
Compressive Yield Strength ◽  
Safety Factors ◽  
Cold Forming ◽  
Deep Waters ◽  
Collapse Prediction

Whereas the wall thickness for most pipelines is governed by internal pressure, the wall thickness of pipelines at very deep waters may be governed by external pressure and the failure mode is collapse. This paper will firstly summarise the work performed in the early 90ties in the SUPERB project that constitutes the basis for the collapse equation adopted in DNV Rules for Submarine Pipeline Systems. This work documented a comparison between various expressions for collapse prediction (Timoshenco, Murphy and Langner (Shell) and Haugsmaa (BSI)) to available experimental results. This work made it possible to select the formulation deemed to be most appropriate as a design equation as well as calibrating safety factors. Secondly, the paper will discuss the well documented detrimental effect that pipe forming can have on the compressive yield strength in the hoop direction and thus the collapse capacity of pipes. This effect led to the introduction of the so-called fabrication factor in DNV-OS-F101 that reduces the compressive yield strength by 7–15 per cent for pipes manufactured using cold forming. However, DNV-OS-F101 states “The fabrication factor may be improved through heat treatment or external cold sizing (compression), if documented” and the paper will summarise various published work, experimental and analyses, that has, during the last 15 years, been performed in several pipeline projects to document the beneficial effect that mainly light heat treatment but also optimised forming in the UOE process have on the compressive yield stress and collapse capacity.

scholarly journals On the Generalized Distance Energy of Graphs

Mathematics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 17 ◽  
Author(s):  
Abdollah Alhevaz ◽  
Maryam Baghipur ◽  
Hilal A. Ganie ◽  
Yilun Shang
Keyword(s):  
Lower Bounds ◽  
Complete Graph ◽  
Connected Graph ◽  
Distance Matrix ◽  
Wiener Index ◽  
Diagonal Matrix ◽  
Upper And Lower Bounds ◽  
Star Graph ◽  
Extremal Graphs ◽  
Generalized Distance

The generalized distance matrix D α ( G ) of a connected graph G is defined as D α ( G ) = α T r ( G ) + ( 1 − α ) D ( G ) , where 0 ≤ α ≤ 1 , D ( G ) is the distance matrix and T r ( G ) is the diagonal matrix of the node transmissions. In this paper, we extend the concept of energy to the generalized distance matrix and define the generalized distance energy E D α ( G ) . Some new upper and lower bounds for the generalized distance energy E D α ( G ) of G are established based on parameters including the Wiener index W ( G ) and the transmission degrees. Extremal graphs attaining these bounds are identified. It is found that the complete graph has the minimum generalized distance energy among all connected graphs, while the minimum is attained by the star graph among trees of order n.

scholarly journals Hadamard k-fractional inequalities of Fejér type for GA-s-convex mappings and applications

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Hui Lei ◽  
Gou Hu ◽  
Zhi-Jie Cao ◽  
Ting-Song Du
Keyword(s):  
Lower Bounds ◽  
Hypergeometric Functions ◽  
Upper And Lower Bounds ◽  
Weighted Inequalities ◽  
Convex Mappings ◽  
Special Means

Abstract The main aim of this paper is to establish some Fejér-type inequalities involving hypergeometric functions in terms of GA-s-convexity. For this purpose, we construct a Hadamard k-fractional identity related to geometrically symmetric mappings. Moreover, we give the upper and lower bounds for the weighted inequalities via products of two different mappings. Some applications of the presented results to special means are also provided.

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