Abstract Underground pipes are essential infrastructure for water, oil and gas transport. The presence of localized pitting corrosion has been identified as one of the main deterioration mechanisms for metal pipes, which, when exposed to external loadings, can easily fail due to intensified stresses at the corrosion pit. The assessment of such an intensified stress field around the pit has been a key focus for decades since it is a major mode of pipe failures. Although stress intensity factors for structures with surface cracks have been extensively studied in literature, there is little study essentially relating the stress intensity factors of pipes with different levels of pitting corrosion. In the present study, a three-dimensional geometrical model for corrosion pits is proposed and a J -integral based finite element method is employed to derive the solutions for stress intensity factors for various pit and pipe geometries. Attempt is also made to derive formulas of maximum stress intensity factors by use of the evolutionary polynomial regression method. It has been found that the maximum stress intensity factor for corrosion pits with high aspect ratio occurs at a different position from those with low aspect ratio. It has also been found that idealization of corrosion pits as surface cracks rather than three-dimensional pits will cause an inaccurate estimate of stress intensity factors for pipes. The results of this study provide a fundamental basis for safety evaluation and life prediction of buried cast iron pipelines.
Last. Wei Yang(WUT: Wuhan University of Technology)H-Index: 23
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Corrosion, manufacturing defects or complex stress state can induce inclined surface cracks on pipes that lead to failure by mixed mode fracture. Very few studies have been undertaken on stress intensity factors for inclined cracks with mixed modes. This paper presents a combined J integral and finite element method to determine the stress intensity factors for inclined external surface cracks in pressurized pipes. A meshing technique is proposed to model the complex region around the crack. To ...
One of the factors affecting the life-time of the main pipelines is their susceptibility to different types of corrosion. A common type of pipeline corrosion is pitting corrosion which is a form of localized corrosion - a random process occurring in a certain section of the pipeline, leading to walls thinning under the influence of the external environment. Such a change in the pipeline geometry accompanied by a significant change in the local stress-strain state leads to a large number of emerg...
Purpose – The purpose of this paper is to develop a multi-scale modeling approach for simulating the tensile behavior of corroded aluminum alloy 2024 T3. Design/methodology/approach – The approach combines two FE models: a model of a three-dimensional representative unit cell representing a pit and a model of the tensile specimen. The models lie at the micro- and macro-scales, respectively. The local homogenized mechanical behavior of the corroded material is simulated for different pit configur...
Abstract Pitting corrosion is an insidious form of localized corrosion affecting characteristics of various engineering metallic alloys. Currently very limited literature exists with regard to systematic characterization of pitted surfaces or the efficient use of numerical methods to assess its effect, i.e. fatigue life reduction caused by the state of a corroded specimen and particularly through the study of stress concentrations considering the geometrical anomalies introduced to a surface. Mu...
Aging and deterioration of underground cast iron pipes is inevitable after their long time in service, with corrosion being the most predominant mechanism for pipe failures. Although considerable research has been undertaken in the past few decades, more is on the effects of corrosion on structural capacity of pipes than that on the prediction of their service life. This paper presents a methodology to quantitatively assess the risk of pipe collapse and predict its remaining service life using a...
Last. Chun-Qing Li(RMIT: RMIT University)H-Index: 22
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Abstract Failure of cylindrical vessels can be caused by stress singularity at pitting corrosion induced cracks. Literature suggests that most of research focuses on stress intensity factors for surface cracks with low aspect ratios, i.e., a/c ⩽ 1.0. Situation may well arise where the aspect ratio of cracks is larger than one. This paper attempts to propose a weight function method to determine stress intensity factors for high aspect ratio semi-elliptical cracks in cylindrical vessels. The weig...
Abstract Surface cracks with aspect ratio a / c > 1.0 can occur in pipes subjected to corrosion attacks. There are few studies on stress intensity factors for semi-elliptical surface cracks with such high aspect ratio. With the failure rate for cast iron pipes unacceptably high there is a need to examine the accuracy of the prediction of stress intensity factors for pipes with high aspect ratio. However, little research has been undertaken on stress intensity factors with high aspect ratio. This...
#2Yoichi Sumi(Yokohama National University)H-Index: 18
The objective of this study was to estimate the strength and deformability of corroded steel plates under quasi-static uniaxial tension. In order to accurately simulate this problem, we first estimated the true stress–strain relationship of a flat steel plate by introducing a vision sensor system to the deformation measurements in tensile tests. The measured true stress–stain relationship was then applied to a series of nonlinear implicit three-dimensional finite element analyses using commercia...
Localized (pitting) corrosion has been observed in steel and high-strength aluminium alloys in aqueous environments and has been identified as a potential origin for fatigue crack nucleation. In the present study, under uniaxial tension loading, stress distribution at the semi-elliptical corrosion pits has been investigated by conducting a series of three-dimensional semi-elliptical pitted models, systematically. Based on the finite element analyses, it is concluded that pit aspect ratio (a/2c) ...
Evolutionary Polynomial Regression (EPR) is a recently developed hybrid regression method that combines the best features of conventional numerical regression techniques with the genetic programming/symbolic regression technique. The original version of EPR works with formulae based on true or pseudo-polynomial expressions using a single-objective genetic algorithm. Therefore, to obtain a set of formulae with a variable number of pseudo-polynomial coefficients, the sequential search is performed...
Abstract The municipal water distribution systems across the world include a significant amount of cast-iron pipes. Many of the buried cast-iron pipes are over fifty years old and require rehabilitation. Municipalities decide on a rehabilitation solution between the replacement and re-use of the existing pipes based on the remaining strengths of the pipes. Fracture mechanics has appeared as the most viable tool for remaining strength assessment of the deteriorating pipes. However, a method of as...
Last. Jung-Gu Kim(SKKU: Sungkyunkwan University)H-Index: 29
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Abstract The corrosion of district heating (DH) pipelines in the internal environment is carefully controlled, however the long-terms of corrosion induced fracture is still uncertain. The general corrosion of pipeline in the heating water is very moderate, therefore it is almost not affected to initiate fracture. While, localized corrosion in weld zone is very dangerous situation because it can act as a stress concentration point. Therefore, it is significant to analyze using the fracture mechan...
Municipal water distribution systems in Canada and other countries include a large number of cast iron pipes that were installed almost 50 years ago. For structural integrity assessment of these pi...
In order to analyse failures of an ageing water pipe, some methods such as the loss-of-section require remaining wall thickness (RWT) along the pipe to be fully known, which can be measured by the magnetism based non-destructive evaluation sensors though they are practically slow due to the magnetic penetrating process. That is, fully measuring RWT at every location in a water pipe is not really practical if RWT inspection causes disruption of water supply to customers. Thus, this paper proposes...
Last. Shangtong Yang(University of Strathclyde)H-Index: 14
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Abstract Steel pipes have been widely used in the water and petroleum industries where crack-like flaws have long been recognised as a major cause of their failures. This paper intends to develop a new method for determining the elasto-plastic J-integral of cracked pipes made of all types of steel. A solution to elasto-plastic J-integrals is derived for external longitudinal semi-elliptical surface cracks in pressurised steel pipes. A meshing technique is developed in the detailed three-dimensio...
Last. Jung-Gu Kim(SKKU: Sungkyunkwan University)H-Index: 29
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To identify the effects of the stress concentration at the pit on the fracture of the district heating (DH) pipeline, the stress increase with the wall thickness reduction was formulated. The formula includes the stress intensity factor with the pitting corrosion. As a result of the application of the DH pipeline conditions to the ASME B31.3 code formula and corrosion test, the interplay with only uniform corrosion and stress due to the internal pressure can not be an immediate reason for the DH...
Abstract The remaining strength and the fatigue life of externally pitted corroded metallic pipeline are often assessed using an idealization to model the pit morphology, typically semi-ellipsoidal and cuboidal. Such idealized pit geometries are shown herein to underestimate Stress Concentration Factors (SCFs). By implication this leads to significant overestimates of fatigue life for pitting corroded pipes under sustained cyclic loading which could be the reason behind some of the recent unexpe...
#1Linh Nguyen(FedUni: Federation University Australia)H-Index: 16
#2Jaime Valls Miro(UTS: University of Technology, Sydney)H-Index: 19
Over 50% of global pipes have been made of cast iron, and most of them are aging. In order to effectively estimate possibilities of their failures, which is paramount for efficiently managing asset infrastructures, it requires the remaining wall thickness (RWT) of a pipe to be known. In fact, RWT of the cast iron pipes can be primarily measured by the magnetism based nondestructive testing technologies though they are quite slow. To speed up the inspection process, it is proposed to sense RWT of...
Factors affecting the operational life of the water supply and sewer utility networks have been investigated. A method has been proposed for identifying the main factors affecting the operational reliability of distribution networks, which is based on the use of the expert evaluation method. It has been found that the most affecting factors are: pipeline material; corrosion of pipe and joint materials due to the corrosive environment; technical condition; service life; non-compliance of pipe gra...