Surface Stress Analysis of Internally Corroded Pipes Under External Pressure

2017 ◽  
Author(s):  
Zhanfeng Chen ◽  
Xiaoli Shen ◽  
Hao Ye ◽  
Sunting Yan ◽  
Zhijiang Jin
Keyword(s):  
Surface Stress ◽  
Internal Surface ◽  
Approximate Solutions ◽  
External Pressure ◽  
Diameter Ratio ◽  
Stress Distributions ◽  
Failure Pressure ◽  
Hoop Stresses ◽  
Stress Function Method ◽  
Maximum Stresses

Corrosion often leads to the failure of transporting pipelines. The surface stresses on the corroded pipes are related to the failure pressure. In this paper, a double circular arc (DCA) model is developed to calculate the surface stress of the internal corroded pipes under external pressure. In addition, a critical corrosion ratio and a critical thickness-to-diameter ratio are presented to determine the location of the maximum stress. Based on the stress function method and bipolar coordinates, an analytical solution of the DCA model was obtained. And then the stress distributions on the internal and external surfaces of the corroded pipes were determined. Next, the equivalent and hoop stresses at several locations in the cross section of the corroded pipes were discussed. The calculated results were validated using finite element method (FEM). Results show that the maximum stresses vary from the internal surface to the external surface with the increase of the corrosion ratio or the thickness-to-diameter ratio. Our research provides a benchmark for approximate solutions to predict the failure pressure and assess the integrity of the corroded pipelines.

Approximate Direct and Inverse Relationships for Thermal and Stress States in Thick-Walled Vessels Under Thermal Shock

2006 ◽  
Vol 129 (1) ◽  
pp. 52-57 ◽  
Author(s):  
A. E. Segall ◽  
R. Akarapu
Keyword(s):  
Finite Element ◽  
Thermal Shock ◽  
Thermal Loading ◽  
Thermoelastic Stress ◽  
Internal Surface ◽  
Approximate Solutions ◽  
Stress Distributions ◽  
Starting Point ◽  
Laplace Transformations ◽  
Stress States

Approximate solutions were derived for the transient through steady-state thermal-stress fields developed in thick-walled vessels subjected to a potentially arbitrary thermal shock. In order to accomplish this, Duhamel’s integral was first used to relate the arbitrary thermal loading to a previously derived unit kernel for tubular geometries. Approximate rules for direct and inverse Laplace transformations were then used to modify the resulting Volterra equation to an algebraically solvable and relatively simple form. The desired thermoelastic stress distributions were then determined using the calculated thermal states and elasticity theory. Good agreement was seen between the derived temperature and stress relationships and earlier analytical and finite-element studies of a cylinder subjected to an asymptotic exponential heating on the internal surface with convection to the outer environment. It was also demonstrated that the derived relationships can be used to approximate the more difficult inverse (deconvolution) thermal problem for both exponential (monotonic) and triangular (non-monotonic) load histories. The use of polynomial of powers tn∕2 demonstrated the feasibility of employing the method with empirical data that may not be easily represented by standard functions. For any of the direct and inverse cases explored, the resulting relationships can be used to verify, calibrate, and/or determine a starting point for finite-element or other numerical methods.

The Effect of Length: Diameter Ratio on Collapse of Casing

1984 ◽  
Vol 106 (2) ◽  
pp. 160-165 ◽  
Author(s):  
N. C. Huang ◽  
P. D. Pattillo
Keyword(s):  
Axial Load ◽  
External Pressure ◽  
Field Application ◽  
Diameter Ratio ◽  
Finite Cylinder ◽  
Oil Well ◽  
Steel Mill ◽  
Cross Sectional ◽  
Axial Tension ◽  
Collapse Resistance

This paper presents an analysis of the cross-sectional collapse of a cylinder of finite length loaded simultaneously by an axial tension (which may be zero) and external pressure. The calculation is based on Sanders’ nonlinear shell equations with plasticity introduced via the concept of effective stress from a uniaxial tension test. The finite cylinder is an appropriate model of oil well casing as it undergoes quality control testing in the steel mill where the edges of the cylinder are usually fixed in the case of nonzero axial load and free in the case of zero axial load. However, in field application, the length: diameter ratio of casing is such that the cylinder may be considered infinite. Guidelines contained herein permit prediction of the collapse resistance of field casing from the results of mill tests performed on short samples.

Through-Thickness Residual Stress Distribution After the Cold Expansion of Fastener Holes and Its Effect on Fracturing

2004 ◽  
Vol 126 (1) ◽  
pp. 129-135 ◽  
Author(s):  
A. Tamer O¨zdemir ◽  
Lyndon Edwards
Keyword(s):  
Thickness Effect ◽  
Fourier Series Expansion ◽  
Hole Drilling ◽  
Three Dimension ◽  
Stress Distributions ◽  
Element Analysis ◽  
Cold Expansion ◽  
Residual Strains ◽  
Hoop Stresses ◽  
Stress Patterns

Many analytical and experimental techniques utilize two-dimensional analysis approach to determine residual strains and stresses at cold expanded holes. In the present work, a recently developed technique of hole drilling was used to sketch stress patterns in three-dimension at a particular orientation of split-sleeve cold expanded holes. At this orientation, similarities were obtained in between the present results and the stress distributions measured by Fourier series expansion, neutron diffraction methods and prediction of a recent finite element analysis. It is clear that after cold expansion there are significant variations in residual hoop stresses at different sections through the thickness of the plate. However, finish reaming and de-burring around the hole redistributes residual stresses such that hoop stresses adjacent to the hole along its entire length becomes more compressive and almost uniform. Finally a correlation between stress pattern and crack profile, displaying the through-thickness effect was shown.

Elastic Analysis of Journal Bearings

Volume 1 ◽  
2004 ◽  
Author(s):  
M. M. Villar ◽  
M. M. Pe´rez
Keyword(s):  
Stress Distribution ◽  
General Purpose ◽  
Von Mises Stress ◽  
Elastic Analysis ◽  
Stress Distributions ◽  
Finite Element Program ◽  
Relative Significance ◽  
Element Program ◽  
Von Mises ◽  
Hoop Stresses

In this paper a numerical model is used to investigate the effect of the elasticity of the bearing in the pressure distribution in the lubricant and the stress distribution in the bearing. The lubricant film, as well as a bearing, including the lining and the backing of the insert, and the housing, are modeled using the general-purpose ANSYS®5.7 commercial Finite Element program. Results have been obtained for the pressure, radial displacement, hoop and von Mises stress distributions at the surface of the bearing, as well as for the shear stress distribution at the interface between the lining and the backing. A number of conclusions have been drawn regarding the relative significance of the steep pressure gradient at the end of the lubricated region on the hoop stresses that cause localized bending distortions at the surface of the lining. These localized bending distortions, in turn, are likely to cause fatigue failure of the lining.

scholarly journals Study on the characteristics of pipe buckling strength under pure bending and external stress using nonlinear finite element analysis

2021 ◽  
Vol 12 (2) ◽  
pp. 110-116
Author(s):  
Hartono Yudo ◽  
Wilma Amiruddin ◽  
Ari Wibawa Budi Santosa ◽  
Ocid Mursid ◽  
Tri Admono
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bending Moment ◽  
Nonlinear Finite Element Analysis ◽  
External Pressure ◽  
Diameter Ratio ◽  
Nonlinear Finite Element ◽  
Pure Bending ◽  
Element Analysis ◽  
Buckling Strength

Buckling and collapse are important failure modes for laying and operating conditions in a subsea position. The pipe will be subjected to various kinds of loads, i.e., bending moment, external pressure, and tension. Nonlinear finite element analysis was used to analyze the buckling strength of the pipe under pure bending and external pressure. The buckling of elastic and elasto-plastic materials was also studied in this work. The buckling strength due to external pressure had decreased and become constant on the long pipe when the length-to-diameter ratio (L/D) was increased. The non-dimensional parameter (β), which is proportionate to (D/t) (σy/E), is used to study the yielding influence on the buckling strength of pipe under combined bending and external pressure loading. The interaction curves of the buckling strength of pipe were obtained, with various the diameter-to-thickness ratio (D/t) under combination loads of external pressure and bending moment. For straight pipes L/D = 2.5 to 40, D = 1000 to 4000 mm, and D/t = 50 to 200 were set. The curved pipes D/t = 200, L/D =2.5 to 30 have been investigated by changing the radius of curvature-to-diameter ratio (R/D) from 50 to ∞, for each one. With decreasing R/D, the buckling strength under external pressure decreases slightly. This is in contrast to the bending of a curved pipe. When the value of R/D was decreased, the flexibility of the pipe was increased. However, the buckling strength of the pipe during bending was decreased due to the oval deformation at the cross-section.

Experimental and numerical assessment on failure pressure of textured pipelines

2021 ◽  
pp. 1-20
Author(s):  
Hassan Karampour ◽  
Mahmoud Alrsai ◽  
Hossein Khalilpasha ◽  
Faris Albermani
Keyword(s):  
Ductile Failure ◽  
Tensile Tests ◽  
External Pressure ◽  
Burst Pressure ◽  
Failure Pressure ◽  
Numerical Assessment ◽  
Pressure Tests ◽  
Physical Tests ◽  
Smooth Pipe ◽  
Do So

Abstract A series of physical tests and finite element (FE) analyses are conducted to evaluate the failure of smooth (conventional) and textured (proposed concept) pipes. To do so, hydrostatic pressure tests are performed on aluminium beverage cans (ductile failure) and additively manufactured Ti6Al4V-0406 titanium pipes (brittle failure). Mechanical material properties are obtained from tensile tests of coupon samples. In absence of physical burst pressure tests, FE models are validated against experimental results of external pressure tests and are used to predict the buckle initiation (Pi) and burst pressure (Pb) capacity of the textured pipes with different number of circumferential triangles, N, and base angles, a. Results show that buckle initiation pressures of the textured concept is 2.34 and 1.80 times greater than those of the smooth aluminium cans and titanium pipes, respectively. However, the burst pressure of the textured pipe can only get 3% greater than the smooth pipe. Based on the current results a textured pipe with N=6 and a=30° is the optimum textured design.

External Longitudinal Flaws in Pipes Under Complex Loading

2000 ◽  
Vol 123 (1) ◽  
pp. 139-145 ◽  
Author(s):  
Roberto Brighenti
Keyword(s):  
Thermal Stresses ◽  
Superposition Principle ◽  
Three Dimensional ◽  
Complex Loading ◽  
Stress Distributions ◽  
Power Series Expansions ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Hoop Stresses ◽  
Crack Faces

A round pipe with an external longitudinal surface flaw is assumed to be subjected to different types of elementary hoop stress distributions acting perpendicular to the crack faces. The stress intensity factors (SIFs) along the crack front for such elementary cases are determined through the three-dimensional finite element method. Then these results are used to compute approximate values of SIFs in the case of complex loadings (such as internal pressure, thermal stresses, residual stresses due to plasticization, etc.), by employing both the superposition principle and the power series expansions of the actual hoop stresses. Thick and thin-walled pipes are examined, and some results are compared with those presented by other authors.

Analysis of Stresses for Cross-Ply Laminates with a Matrix Crack under Bending

2011 ◽  
Vol 284-286 ◽  
pp. 492-495
Author(s):  
Qing Dun Zeng ◽  
Mao Hua Ouyang
Keyword(s):  
Failure Mechanism ◽  
Transverse Crack ◽  
Approximate Solutions ◽  
Matrix Crack ◽  
Stress Distributions ◽  
Shear Lag ◽  
New Approach ◽  
Shear Lag Model ◽  
Lag Model ◽  
Shear Lag Theory

On the basis of the shear-lag theory, an analysis was presented for stress redistributions of cross-ply laminates with a transverse matrix crack in the 90º ply under bending by establishing a layered shear-lag model. The present results show that approximate solutions of displacement and stress distributions for cross-ply laminates with a transverse crack under bending can be obtained by using a shear-lag method. The present paper therefore affords a new approach for studying the stress redistributions and failure mechanism for cross-ply laminates with flaw under bending.

Analysis of Stresses for Cross-Ply Laminates with Multiple Matrix Cracks under Bending

2011 ◽  
Vol 311-313 ◽  
pp. 256-259
Author(s):  
Qing Dun Zeng ◽  
Mao Hua Ouyang
Keyword(s):  
Finite Element ◽  
Approximate Solutions ◽  
Stress Distributions ◽  
Shear Lag ◽  
Transverse Cracks ◽  
Shear Lag Model ◽  
Matrix Cracks ◽  
Variational Solutions ◽  
Lag Model ◽  
Good Agreement

On the basis of the shear-lag theory, a layered shear-lag model was established to study the stress redistributions of cross-ply laminates with multiple transverse matrix cracks in the 90º ply under bending. The present results are in a good agreement with variational solutions and finite element results and show that approximate solutions of stress distributions for cross-ply laminates with transverse cracks under bending can be obtained by using a shear-lag method. The present paper therefore affords a new way or method for studying the stress redistributions and failure mechanism for cross-ply laminates with flaws under bending.

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