Refinement and evaluation of crack-opening-area analyses for circumferential through-wall cracks in pipes

Rahman, Sharif; Brust, F. W.; Ghadiali, N.; Krishnaswamy, P.; Wilkowski, G.; Choi, Young−Hwan; Moberg, F.; Brickstad, B.

doi:10.2172/46620

Cited by 25 publications

(9 citation statements)

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“…(1), the total crack driving force, J, for an o-centered crack of angle c are the well-known GE/EPRI equations 4 [30±33] for elastic and plastic components of J, respectively, for a symmetrically centered crack, i.e., when c 0, Fyap, R m at and h 1 yap, n, R m at are elastic and plastic in¯uence functions for symmetrically centered cracks, M 0 is a reference moment, and K e, c and K p, c are constant elastic and plastic correction factors for o-center cracks, respectively. Note, an eective crack length using plastic-zone-size correction was used in the original GE/EPRI equations [30].…”

Section: A New J-estimation Methodsmentioning

confidence: 99%

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Elastic–plastic analysis of off-center cracks in cylindrical structures

Firmature

Rahman

2000

Engineering Fracture Mechanics

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This paper presents new elastic and elastic±plastic ®nite element solutions of the J-integral for a pipe containing o-center through-wall cracks under pure bending. The analysis is based on a three-dimensional nonlinear ®nite element method and small-strain theory. One hundred and ®ve analyses were performed using the ABAQUS commercial code for a wide variety of crack sizes, o-center crack angles, and material hardening exponents. The results from these analyses show that the J-integral values at the two crack fronts of an o-center crack are unequal due to the loss of symmetry with respect to the bending plane of the pipe. In addition, the J-integral is larger, and hence, critical at the crack front which is farther away from the bending axis of the pipe. This is because, at that crack front, the tensile stress is larger and the component of the applied bending moment about the crack centerline has a further crack-opening eect. Also at this crack front, the J values can be lower or slightly higher than those of a symmetrically centered crack, depending on the crack size and o-centered angle. For the crack front that is closer to the bending axis, the J values are always lower than those of a symmetrically centered crack. This implies that the load-carrying capacity of a pipe is usually larger for an o-center crack than that for a symmetrically centered crack. Finally, based on these ®nite element solutions, new analytical expressions of J-integral were developed for fracture analysis of pipes containing o-center cracks. 7

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Section: A New J-estimation Methodsmentioning

confidence: 99%

“…See Ref. [4,8] for justi®cation of using actual crack length over eective crack length. The evaluations of Fyap, R m at and h 1 yap, n, R m at are described in Appendix A.…”

Section: A New J-estimation Methodsmentioning

confidence: 99%

Elastic–plastic analysis of off-center cracks in cylindrical structures

Firmature

Rahman

2000

Engineering Fracture Mechanics

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“…Fracture analysis can be based on linear-elastic or more complex elastic± plastic (nonlinear) models. It is well established that nonlinear fracture-mechanics methods, compared with the elastic methods [1,2], provide more realistic measures of fracture behavior of cracked structures with high toughness and low strength materials. Cracked components composed of these materials, when used in nuclear power plants, chemical and fossil plants, automobiles, and aerospace and aircraft propulsion systems, pose a serious threat to structural integrity.…”

Section: Introductionmentioning

confidence: 99%

“…Cracked components composed of these materials, when used in nuclear power plants, chemical and fossil plants, automobiles, and aerospace and aircraft propulsion systems, pose a serious threat to structural integrity. In much or all of the working temperature regime of these components, the material is typically stressed above the brittle-to-ductile transition temperature where the fracture response is essentially ductile, and the material is capable of considerable inelastic deformation [1,2]. As such, elastic±plastic theories should be employed in fracture analyses of these structural components.…”

Section: Introductionmentioning

confidence: 99%

Probabilistic fracture mechanics for nonlinear structures

Rahman

Kim

2001

International Journal of Pressure Vessels and Piping

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“…1] and can thus be located anywhere around the pipe circumference. The likelihood of a crack being off-centered can be further emphasized in light of the argument that a symmetric bending plane under normal operating stress may become very different under normal plus safe-shutdown earthquake stress, due to the uncertainty in the seismic ground motion [4][5][6]. Hence, analysis of off-center cracks is an exciting research area for pipe fracture and LBB applications.…”

Section: Introductionmentioning

confidence: 99%

Probabilistic analysis of off-center cracks in cylindrical structures

Chen

Firmature

Rahman³

2000

International Journal of Pressure Vessels and Piping

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This paper presents a probabilistic methodology for fracture-mechanics analysis of off-center cracks in pipes subject to pure bending moment. It is based on: (1) a new analytical approximation of the J-integral; (2) statistical models of uncertainties in loads, material properties, and crack geometry; and (3) standard computational methods of structural reliability theory. The proposed analytical equations were applied to a probabilistic fracture-mechanics analysis of off-center cracks in pipes. The second-order reliability method was used to determine the probabilistic characteristics of the J-integral and failure probability based on the initiation of crack growth. Numerical examples are presented to illustrate the proposed methodology. The results show that the failure probability strongly depends on the offcenter crack angle and is generally lower than that of a pipe with a symmetrically centered crack. Hence, simplifying an off-center crack by a symmetrically centered crack can produce significant conservatism in predicting failure probabilities. In addition, uncertainty in the offcenter crack angle, if it exists, can increase the failure probability of pipes. ᭧

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Refinement and evaluation of crack-opening-area analyses for circumferential through-wall cracks in pipes

Cited by 25 publications

References 0 publications

Elastic–plastic analysis of off-center cracks in cylindrical structures

Elastic–plastic analysis of off-center cracks in cylindrical structures

Probabilistic fracture mechanics for nonlinear structures

Probabilistic analysis of off-center cracks in cylindrical structures

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