This paper presents a reliability-based methodology for assessing fracture failures of steel pipes with sharp corrosion pits. Based on newly developed models of elastic fracture toughness, the simple criterion of stress intensity factor (SIF) is used to establish the limit state functions for pipes with sharp corrosion pits in the longitudinal and circumferential directions. A stochastic model of load effect is developed and a time-dependent reliability method based on first passage probability for nonstationary lognormal processes is employed to quantify the probability of failure and predict the remaining service life. After applying the methodology to a case study, sensitivity analysis is carried out to identify the most influential variables on the probability of failure. It is found in the paper that the correlation coefficient has a considerable effect on probability of failure of steel pipes with sharp corrosion pits and that the larger the mode I fracture toughness is, the smaller the probability of pipe failure is.
Last. Chun-Qing Li(RMIT: RMIT University)H-Index: 22
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Linear elastic fracture mechanics has been widely used for fracture analysis of cracked metals. For ductile materials, it is known that the yielding of a crack front results in the easing of stress intensity at the crack front, which ultimately increases the total fracture toughness of the material. Therefore, to use linear elastic fracture mechanics for prediction of the failure of ductile materials requires the extraction of the elastic portion of the fracture toughness. The intention of this ...
Last. Shangtong Yang(University of Strathclyde)H-Index: 14
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Linear elastic fracture mechanics has been widely employed for fracture analysis of cracked pipes. For ductile metal pipes, the existence of plasticity eases the stress concentration at the crack front, which increases the fracture toughness of the pipe. Therefore, when using linear elastic fracture mechanics to predict the fracture failure of ductile pipes, the plastic portion of the fracture toughness should be excluded. This paper intends to derive an analytical model of elastic fracture toug...
#2Afshin Firouzi(IAU: Islamic Azad University)H-Index: 8
Last. Wei Yang(WUT: Wuhan University of Technology)H-Index: 23
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AbstractIn time-dependent reliability analysis, the calculation of the mean outcrossing or upcrossing rate of a stochastic process from a safe domain or barrier level based on the Rice formula continues to present serious challenge to researchers in the field. Furthermore, the derivation of closed-form analytical solutions to the first passage probability for nonstationary processes has not been very successful except for Gaussian process. The intention of this paper is to drive a closed-form so...
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 ...
Last. Hong-Shuang Li(NUAA: Nanjing University of Aeronautics and Astronautics)H-Index: 13
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This paper presents a computational framework for implementing an advanced Monte Carlo simulation method, called Subset Simulation (SS) for time-dependent reliability prediction of underground flexible pipelines. The SS can provide better resolution for low failure probability level of rare failure events which are commonly encountered in pipeline engineering applications. Random samples of statistical variables are generated efficiently and used for computing probabilistic reliability model. It...
Abstract In this paper, the cause of failure of an ASTM A53 Grade B carbon steel pipe was investigated. The investigated ASTM A53 Grade B pipe was used for a condensate pipeline and was found to be cracked after six months in service. The failed parts were investigated by means of stereoscopic microscope, optical microscope, scanning electron microscope equipped with energy dispersive X-ray spectroscopy micro-analysis, spark emission spectrometer, tension tester and Vickers hardness tester, in o...
SUMMARY: The corrosion of ferrous water mains is a signific ant problem for the Australian Water Industry. A significant proportion of Australia’s a geing water infrastructure is composed of cast iron and steel cement lined pipes, which are prone to co rrosion on the external surfaces that are in contac t with soil. Internal corrosion is not a significant issue for cement-lined pipes. For the water industr y to manage these ageing assets effectively, quantitativ e predictions of the damage likel...
Last. Shu-Xin Li(Lanzhou University of Technology)H-Index: 11
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A probabilistic method based on the corrosion module of the FITNET FFS procedure is presented to perform the structural integrity analysis for pipelines. The comparison of the failure pressure determined by both deterministic and probabilistic methods shows that even for a high safety factor, the deterministic method may predict nonconservative results. FITNET FFS procedure predicts a similar probability to that given by the Shell-92 model. The sensitivity analysis of both the uncertainty of the...
#1Wenxing Zhou(UWO: University of Western Ontario)H-Index: 21
A methodology is presented in this paper to evaluate the time-dependent system reliability of a pipeline segment that contains multiple active corrosion defects and is subjected to stochastic internal pressure loading. The pipeline segment is modeled as a series system with three distinctive failure modes due to corrosion, namely small leak, large leak and rupture. The internal pressure is characterized as a simple discrete stochastic process that consists of a sequence of independent and identi...
Abstract With the increasing emphasis on attempting to retain in service ageing infrastructure models for the description and prediction of corrosion losses and for maximum pit depth are of increasing interest. In most cases assessment and prediction will be done in a probabilistic risk assessment framework and this then requires probabilistic corrosion models. Recently, novel models for corrosion loss and maximum pit depth under marine immersion conditions have been developed. The models show t...
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...
This study aims to investigate the effects of correlation of random variables between the adjacent components on time variant system reliability of corroded pipelines. The system reliability analys...