Stress intensity factors for inclined external surface cracks in pressurised pipes

Li, Chun Qing; Fu, Guoyang; Yang, Wei

doi:10.1016/j.engfracmech.2016.08.014

Cited by 48 publications

(11 citation statements)

References 21 publications

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“…The critical fracture intensity factor, i.e., the fracture toughness, of cast iron is typically in the range from 5 to 20 MPa m 0.5 [19][20][21][22]. Our recent fracture tests of the cast iron pipe specimen showed the intensity factor was approximate 12~17 MPa m 0.5 .…”

Section: Leak and Burst Pressuresmentioning

confidence: 99%

Numerical interpretation of pressurized corroded cast iron pipe tests

Zhang

Rathnayaka

Shannon

et al. 2017

International Journal of Mechanical Sciences

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Pitting/patch corrosion is a major and common cause of leaks and (or) bursts in cast iron (CI) pipes that consist of over 50% of global pipelines. The determination of the remaining life of a CI pipe is a major challenge facing water utilities requiring an estimate of the impact of pitting corrosion on the degradation of structural pipe capacity. This paper uses an efficient finite element analysis (FEA) to model the behaviour of large diameter CI pipes with natural or simulated corrosion pits and patches. The test results were obtained through laboratory pressure testing. Laser scanning was used to develop three dimensional geometric models of pipe specimens for direct use in the numerical modelling. The CI material was simulated by a non-linear hyperbolic elastic model (termed MHM-CI) recently developed by the authors for CI pipe modelling. The numerical results showed that the proposed FEAs with the MHM-CI model are reasonably capable to predict the measured responses with increasing water pressure, importantly at the critical pipe corrosion patches, such as hoop strains, initiation of leak and burst failures. The initiation of fracture was explained by material failure purely by tension, which can form a crack that could lead to water leakage. Final burst possibility was modelled by using a simplified fracture mechanics approach to determine the critical crack length for spontaneous fast fracture as in a burst. Our numerical findings suggest that the proposed simplified numerical approach may be used to determine whether a corroded cast iron pipe would leak before break provided that the corrosion condition of the pipe and the relevant material properties are available. However, the window of time for leak before break would require further testing since this would be governed by sub critical fracture growth subject to repetitive external and internal pipe loadings.

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Section: Leak and Burst Pressuresmentioning

confidence: 99%

Numerical interpretation of pressurized corroded cast iron pipe tests

Zhang

Rathnayaka

Shannon

et al. 2017

International Journal of Mechanical Sciences

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“…Also, the defects on the pipe walls are often caused by corrosion, which can grow in any directions depending on the heterogeneity of surrounding soil properties (Wang et al, 2018;. Moreover, the crack-like defects in pipes most likely grow in an inclined manner because of the complex stress state (Li et al, 2016). As a result, in these pipes (e.g., Figure 1), the failures can be induced by a mixed mode loading interaction.…”

Section: Introductionmentioning

confidence: 99%

Reliability Assessment of Pressurized Pipes with Inclined Defect

Wang¹,

Wang²,

Yang³

et al. 2020

XV International Conference on Durability of Building Materials and Components. eBook of Proceedings

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Inclined defects in pipelines can lead to failures in the form of mixed mode fracture. A review of the literature suggests that few studies have been carried out on reliability assessment of pipelines considering mixed mode fracture. This paper intends to present a reliability-based method for assessing fracture failures of pressurized pipes with inclined defects. Richard's criterion is employed in the development of the limit state function for reliability assessment. A Stochastic model of load effects is developed, and first passage method with a developed analytical solution is used to predict the pipe failures. A worked example is provided to illustrate the application of the proposed method. The method presented in this paper can help pipe engineers and asset managers to develop a reliability-based maintenance strategy for better management of pipelines.

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“…Therefore, the developed model is only indirectly verified by ensuring that the equivalent influence coefficients for the elastic J integral, the normalized fully plastic J-integral, and total fracture toughness have been accurately determined. For the equivalent influence coefficients, extensive verifications were conducted by Li et al (2016) and Fu et al (2017b) for the proposed finite-element models. Because the same model was used for the cracked plate with inclined surface cracks under biaxial loading, the accuracy of the calculated equivalent coefficients was assured.…”

Section: Verificationmentioning

confidence: 99%

“…In the finite-element models, a conformed mesh was used around the crack region. A meshing technique with mixed quadratic hexahedron and tetrahedron elements in Li et al (2016) and Fu et al (2017b) was adopted. In addition, the energybased J-integral method, which is path-independent and can produce accurate results with relatively coarse meshes, was employed.…”

Section: Equivalent Influence Coefficientsmentioning

confidence: 99%

J-Integral Solution for Elastic Fracture Toughness for Plates with Inclined Cracks under Biaxial Loading

Yang

et al. 2018

J. Eng. Mech.

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This version is available at https://strathprints.strath.ac.uk/63936/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge. Abstract: Surface cracks with different orientations have been recognized as a major cause of potential failures of thin metal structures, which are often under biaxial loading. It has been known that, for cracked ductile metals, plasticity results in an easing of stress intensity at the crack front and ultimately increases the total fracture toughness of the metal. To enable the use of linear elastic fracture mechanics for ductile material failure prediction, the plastic portion of fracture toughness must be excluded. This paper aims to develop a J-integral based method for determining the elastic fracture toughness of ductile metal plates with inclined cracks under biaxial loading. The derived elastic fracture toughness is a function of the plate and crack geometry, strain-hardening coefficient, yield strength, fracture toughness, biaxiality ratio, and inclination angle. It is found that an increase in yield strength or relative crack depth, or a decrease in Mode-I fracture toughness, leads to a larger ratio of elastic fracture toughness to total fracture toughness. It is also found that the effect of biaxiality ratio and inclination angle on elastic fracture toughness is highly dependent on total fracture toughness. It can be concluded that the developed model can accurately predict the fracture failure of ductile thin metal structures with inclined cracks under biaxial loading.Author keywords: Inclined surface cracks; J-integral; Biaxial loading; Elastic fracture toughness; Cracked plates.It has been known that plasticity increases fracture toughness. The underlying mechanism is that yielding caused by plasticity eases stress concentration at the crack front. Consequently, fracture toughness increases and consists of elastic and plastic portions. In order to extract elastic fracture toughness from total fracture toughness, a failure assessment diagram was employed by Yang et al. (2016Yang et al. ( , 2017 and Li et al. (2017). The adopted failure assessment curve (Milne et al. 1988) is independent of both geometry and material properties and may be used for any structure. However, the derived elastic fracture toughness models may be overconservative, given that the curve was derived as a lower bound of the failure assessment diagrams obtained based on...

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Stress intensity factors for inclined external surface cracks in pressurised pipes

Cited by 48 publications

References 21 publications

Numerical interpretation of pressurized corroded cast iron pipe tests

Numerical interpretation of pressurized corroded cast iron pipe tests

Reliability Assessment of Pressurized Pipes with Inclined Defect

J-Integral Solution for Elastic Fracture Toughness for Plates with Inclined Cracks under Biaxial Loading

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