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Article
Publication date: 25 December 2020

Krishna LA, Veerappan AR and Shanmugam S

Elastic stress solutions are required in the field of fracture mechanics and the analysis of creep failure. The published precise elastic solutions are not addressing the…

Abstract

Purpose

Elastic stress solutions are required in the field of fracture mechanics and the analysis of creep failure. The published precise elastic solutions are not addressing the influence of the manufacturing process induced, inevitable cross sectional deviations called ovality and thinning. The influence of ovality on plastic limit and collapse loads are reported in literature. Hence, it is important to study the combined effect of ovality and thinning on elastic stresses of bends.

Design/methodology/approach

This paper relies on elastic finite element evolutions of stress components– longitudinal membrane stress, longitudinal bending stress, circumferential membrane stress and circumferential bending stresses. Based on the results, the coefficients for the equations are also obtained through the regression analysis.

Findings

New analytical solutions are prescribed to estimate the elastic stresses at the mid-section of the 90° very thin-walled bend with ovality and thinning, when subjected to in-plane bending moment. The ovality has significant influence on elastic stress whereas the thinning is not so. The proposed equations give an accurate estimation of elastic stresses at the mid-section of the bend with the incorporation of the parameters, namely R/rm, rm/t and ovality.

Research limitations/implications

The influence of shape imperfections, namely ovality and thinning on elastic stress of 90° very thin-walled bends having rm/t > 20, subject to in-plane bending moment is proposed.

Originality/value

The influence of shape imperfections, namely ovality and thinning, on elastic stress of 90° very thin-walled bends with rm/t > 20, subject to in-plane bending moment is proposed.

Details

Multidiscipline Modeling in Materials and Structures, vol. 17 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 20 October 2021

R. Silambarasan, A.R. Veerappan and S. Shanmugam

The purpose of this paper is to quantify the combined effect of shape distortion and bend angle on the collapse loads of pipe bends exposed to internal pressure and in-plane…

108

Abstract

Purpose

The purpose of this paper is to quantify the combined effect of shape distortion and bend angle on the collapse loads of pipe bends exposed to internal pressure and in-plane closing bending moment. Non-linear finite element analysis with large displacement theory was performed considering the pipe bend material to be elastic perfectly plastic.

Design/methodology/approach

One half of the pipe bend model was built in ABAQUS. Shape distortion, namely, ovality (Co) and thinning (Ct), were each varied from 0% to 20% in steps of 5% and bend angle was varied from 30° to 180° in steps of 30°.

Findings

The findings show that ovality has a significant impact on collapse load. The effect of ovality decreases with an increase in bend angle for small thickness. The opposite effect was observed for large thickness pipe bends. The influence of ovality was more for higher bend angles. Ovality impact was almost negligible at certain internal pressure denoted as nullifying point (NP). The latter increased with an increase in pipe bend thickness and decreased with increase in pipe bend radius. For small bend angles one NP was observed where ovality impact is negligible and beyond this point the ovality effect increased. Two NPs were observed for large bend angles and ovality effect was maximum between the two NPs. Thinning yielded a minimal effect on collapse load except for small bend angles and bend radii. The influence of internal pressure on thinning was also negligible.

Originality/value

Influence of shape distortions and bend angle on collapse load of pipe bend exposed to internal pressure and in-plane closing bending has been not revealed in existing literature.

Details

World Journal of Engineering, vol. 20 no. 2
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 21 December 2022

Raghuraman T., Veerappan AR. and Shanmugam S.

This paper aims to present the approximate limit pressure solutions for thin-walled shape-imperfect 90° pipe bends. Limit pressure was determined by finite element (FE) limit…

Abstract

Purpose

This paper aims to present the approximate limit pressure solutions for thin-walled shape-imperfect 90° pipe bends. Limit pressure was determined by finite element (FE) limit analysis with the consideration of small geometry change effects.

Design/methodology/approach

The limit pressure of 90° pipe bends with ovality and thinning has been evaluated by geometric linear FE approach. Internal pressure was applied to the inner surface of the FE pipe bend models. When von-Mises stress equals or just exceeds the yield strength of the material, the corresponding pressure was considered as the limit pressure for all models. The current FE methodology was evaluated by the theoretical solution which has been published in the literature.

Findings

Ovality and thinning produced a significant effect on thin-walled pipe bends. The ovality weakened pipe bend performance at any constant thinning, while thinning improved the performance of the bend portion at any constant ovality. The limit pressure of pipe bends under internal pressure increased with an increase in the bend ratio and decreased with an increase in the pipe ratio. With a simultaneous increment in bend radius and reduction in wall thickness, there was a reduction in limit pressure. A new closed-form empirical solution was proposed to evaluate limit pressure, which was validated with published experimental data.

Originality/value

The influences of structural deformation (ovality and thinning) in the limit pressure analysis of 90° pipe bends have not been investigated and reported.

Details

World Journal of Engineering, vol. 21 no. 2
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 30 June 2020

L.A. Krishna, A.R. Veerappan and S. Shanmugam

Precise assessment of elastic stress is required in the field of fracture mechanics. While bending a straight pipe, the deformation of the circular cross section out of roundness…

Abstract

Purpose

Precise assessment of elastic stress is required in the field of fracture mechanics. While bending a straight pipe, the deformation of the circular cross section out of roundness called ovality and thinning are foreseeable. The ovality has a significant effect on the structural integrity of the pipe. The sole objective of this paper is to provide new analytical solutions to predict accurate elastic stress distribution at the median section of the U-bend, with deformities such as ovality and thinning when subjected to in-plane closing moment by using elastic finite element analysis.

Design/methodology/approach

The quarter model of the U bend has been analysed by using ABAQUS. The elastic stress components included in this analysis are longitudinal bending stress, longitudinal membrane stress, circumferential bending stress and circumferential membrane stress. Based on finite element results, analytical elastic stress solutions are also provided for both longitudinal and circumferential stresses by using these stress components.

Findings

As the ovality has a significant effect, it is further included in the analytical solution. The thinning is not included since it has very little effect. Analytical stress solutions are provided for a wide range of bend characteristics to include ovality, mean radius and thickness.

Originality/value

Significance of ovality and thinning on elastic stress of U-bend has not been reported in the existing literature.

Details

International Journal of Structural Integrity, vol. 12 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 8 February 2019

Nikolaos Athanasopoulos, Evangelos Gavalas and Spyros Papaefthymiou

The purpose of this paper is to present a finite element method (FEM) model that predicts the collapse pressure of the majority of the gas/petroleum pipelines worldwide. More…

Abstract

Purpose

The purpose of this paper is to present a finite element method (FEM) model that predicts the collapse pressure of the majority of the gas/petroleum pipelines worldwide. More specifically, it refers to pipelines with diameter to wall thickness (D/t) ratios between 15 and 45. The model’s results were evaluated on the basis of the DNV-OS-F101 offshore pipeline design code.

Design/methodology/approach

A series of FEM simulations were conducted using a 2D model created in the ANSYS’ software environment considering both the plane strain and the plane stress approach. The corresponding values of the collapse pressure for pipes with different value sets of D/t and ovality were calculated in Python (programming language) according to the DNV equations. Given that the pipeline’s resistance to collapse is governed by geometric imperfections and material properties, amongst others, the influence of other crucial factors, such as ovality, eccentricity, hardening modulus and the chemical composition (pipe’s steel grade) was examined.

Findings

The FE model approaches very closely the DNV calculations. Although the effect of the hardening modulus and pipe’s steel grade, respectively, was found to be insignificant on the pipeline’s collapse, it turned out that the lower the D/t ratio was the bigger the influence of these factors appeared. The D/t ratio does not affect the pipe’s sensitivity in eccentricity, because for a pipe with the same characteristics and eccentricity, but with higher ovality, the decrease in collapse pressure was found to be lower.

Originality/value

A 2D FEM which estimates collapse pressure and simultaneously takes into account the effect of various factors is less time-consuming and costly than the full-scale pipe collapse tests in pressure chambers.

Details

International Journal of Structural Integrity, vol. 10 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 1 July 2021

Silambarasan R., Veerappan A.R. and Shanmugam S.

The purpose of this study is to investigate the effect of structural deformations and bend angle on plastic collapse load of pipe bends under an in-plane closing bending moment…

Abstract

Purpose

The purpose of this study is to investigate the effect of structural deformations and bend angle on plastic collapse load of pipe bends under an in-plane closing bending moment (IPCM). A large strain formulation of three-dimensional non-linear finite element analysis was performed using an elastic perfectly plastic material. A unified mathematical solution was proposed to estimate the collapse load of pipe bends subjected to IPCM for the considered range of bend characteristics.

Design/methodology/approach

ABAQUS was used to create one half of the pipe bend model due to its symmetry on the longitudinal axis. Structural deformations, i.e. ovality (Co) and thinning (Ct) varied from 0% to 20% in 5% steps while the bend angle (ø) varied from 30° to 180° in steps of 30°.

Findings

The plastic collapse load decreases as the bend angle increase for all pipe bend models. A remarkable effect on the collapse load was observed for bend angles between 30° and 120° beyond which a decline was noticed. Ovality had a significant effect on the collapse load with this effect decreasing as the bend angle increased. The combined effect of thinning and bend angle was minimal for the considered models and the maximum per cent variation in collapse load was 5.76% for small bend angles and bend radius pipe bends and less than 2% for other cases.

Originality/value

The effect of structural deformations and bend angle on collapse load of pipe bends exposed to IPCM has been not studied in the existing literature.

Details

World Journal of Engineering, vol. 19 no. 4
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 1 June 2000

Andrea P. Assanelli, Rita G. Toscano, Daniel H. Johnson and Eduardo N. Dvorkin

The production of steel pipes with guaranteed external collapse pressure (e.g. high collapse casings for oil wells) requires the implementation of an accurate process control. To…

Abstract

The production of steel pipes with guaranteed external collapse pressure (e.g. high collapse casings for oil wells) requires the implementation of an accurate process control. To develop that process control it is necessary to investigate how different parameters affect the external collapse pressure of the pipes. Experimental/numerical techniques implemented to investigate the collapse behavior of steel pipes are presented. The discussion of the experimental techniques includes the description of the facilities for performing external pressure collapse tests and the description of an imperfections measuring system. The numerical techniques include 2D and 3D finite element models. The effects on the value of the pipes’ external collapse pressure of their shape, residual stresses and material properties are discussed.

Details

Engineering Computations, vol. 17 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 22 March 2022

A. Vinothkumar, AR. Veerappan and S. Shanmugam

The aim of this study is to ensure the structural integrity of 90° back-to-back (B2B) pipe bends by developing a closed-form numerical solution for estimating the collapse load of…

Abstract

Purpose

The aim of this study is to ensure the structural integrity of 90° back-to-back (B2B) pipe bends by developing a closed-form numerical solution for estimating the collapse load of shape distorted 90° B2B pipe bends using non-linear finite element (FE) analysis.

Design/methodology/approach

The collapse behaviour of 90° B2B pipe bends with ovality (Co) and thinning (Ct) has been evaluated by non-linear FE approach. Moment load is applied in the form of in-plane closing moment (IPCM). The current FE approach was evaluated by the numerical solution for the plastic collapse moment of pipe bends, which has been published in the literature. The collapse moments were obtained from the twice elastic slope (TES) method using the moment-rotation curve of every individual model.

Findings

The implication of Ct/Cth on collapse load is found to be highly insignificant in terms of increasing bend radius and Co. Co weakens the geometry, and its effect on the collapse load is substantial. A closed-form numerical solution has been proposed to calculate the collapse load of 90° B2B pipe bend with shape imperfections.

Originality/value

The implications of shape distortion (Co and Ct) in the failure analysis (collapse load) of 90° B2B pipe bends has not been investigated and reported.

Details

Multidiscipline Modeling in Materials and Structures, vol. 18 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 December 1966

R.A. Phillips

RECENT developments at Electro‐Hydraulics Ltd. are in two categories: in component design and in solutions to basic hydraulic problems. Examples shown below are selected from a…

Abstract

RECENT developments at Electro‐Hydraulics Ltd. are in two categories: in component design and in solutions to basic hydraulic problems. Examples shown below are selected from a number of fairly recent component design details, followed by an outline of developments in seals and a summary of fatigue tests on hydraulic tubes.

Details

Aircraft Engineering and Aerospace Technology, vol. 38 no. 12
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 January 1982

Controlling the quality of products can lead to improved profitability. Many of the techniques associated with improving both of these aspects will be discussed at the forthcoming…

Abstract

Controlling the quality of products can lead to improved profitability. Many of the techniques associated with improving both of these aspects will be discussed at the forthcoming 6th International Conference on Automated Inspection and Product Control to be held at the Albany Hotel, Birmingham, UK, on 27–29 April, 1982. This preview provides an insight into the technological flavour of the conference.

Details

Sensor Review, vol. 2 no. 1
Type: Research Article
ISSN: 0260-2288

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