Validating 3D two-parameter fracture mechanics models for structural integrity assessments

Abstract Nowadays, it has been recognized that probabilistic fracture mechanics (PFM) is a promising methodology in structural integrity assessments of aged pressure boundary components of nuclear power plants, because it can rationally represent the influencing parameters in their inherent probabilistic distributions without over conservativeness. A PFM analysis code PFM analysis of structural components in aging light water reactor (PASCAL) has been developed by the Japan Atomic Energy Agency to evaluate the through-wall cracking frequencies of domestic reactor pressure vessels (RPVs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) transients. In addition, efforts have been made to strengthen the applicability of PASCAL to structural integrity assessments of domestic RPVs against nonductile fracture. A series of activities has been performed to verify the applicability of PASCAL. As a part of the verification activities, a working group was established with seven organizations from industry, universities, and institutes voluntarily participating as members. Through one-year activities, the applicability of PASCAL for structural integrity assessments of domestic RPVs was confirmed with great confidence. This paper presents the details of the verification activities of the working group, including the verification plan, approaches, and results.

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An Engineering Methodology for Structural Integrity Assessments Using Probabilistic Fracture Mechanics

Advances in Safety and Reliability ◽

10.1016/b978-008042835-2/50165-x ◽

1997 ◽

pp. 1477-1484

Author(s):

Claudio Ruggieri ◽

Robert H. Dodds

Keyword(s):

Fracture Mechanics ◽

Structural Integrity ◽

Probabilistic Fracture Mechanics ◽

Integrity Assessments

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Review of the Current Conservatisms in the Assessment of Thin-Walled Structures

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2009-77476 ◽

2009 ◽

Author(s):

R. S. Kulka ◽

A. J. Price

Keyword(s):

Fracture Mechanics ◽

Best Practice ◽

Structural Integrity ◽

Fracture Behaviour ◽

Stress Distributions ◽

Limit Loads ◽

Thin Walled Structures ◽

Commercial Drivers ◽

Thin Walled ◽

Integrity Assessments

Current methods for performing fracture mechanics assessments of thin-walled structures possess significant levels of conservatism, since they are often for general use with both thin-walled and thick-walled structures. In many industries, there are significant commercial drivers for reducing the amount of conservatism in these assessments. An enhanced understanding of the fracture behaviour of thin-walled structures in different situations may lead to the development of more appropriate structural integrity assessments. A review of the information pertaining to fracture mechanics analysis of thin-walled structures has been conducted. There are indications that improvements to the best practice methodology may be made, through improved tensile and toughness properties, consideration of limit loads, and the effect of residual stress distributions.

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Verification of Probabilistic Fracture Mechanics Analysis Code PASCAL

Volume 2: Plant Systems, Structures, Components and Materials ◽

10.1115/icone25-66468 ◽

2017 ◽

Author(s):

Yinsheng Li ◽

Genshichiro Katsumata ◽

Koichi Masaki ◽

Shotaro Hayashi ◽

Yu Itabashi ◽

...

Keyword(s):

Fracture Mechanics ◽

Working Group ◽

Nuclear Power ◽

Power Plants ◽

Structural Integrity ◽

Pressure Vessels ◽

Irradiation Embrittlement ◽

Energy Agency ◽

Probabilistic Fracture Mechanics ◽

Integrity Assessments

Probabilistic fracture mechanics (PFM) has been recognized as a promising methodology in structural integrity assessments of aged pressure boundary components of nuclear power plants because it can rationally represent the influencing parameters in their inherent probabilistic distributions without over conservativeness. In Japan, a PFM analysis code PASCAL (PFM Analysis of Structural Components in Aging LWR) has been developed by the Japan Atomic Energy Agency (JAEA) to evaluate the through-wall cracking frequencies of Japanese reactor pressure vessels (RPVs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) transients. In addition, efforts have been made to strengthen the applicability of PASCAL to structural integrity assessments of domestic RPVs against non-ductile fracture. On the other hand, unlike deterministic analysis codes, the verification of PFM analysis codes is not easy. A series of activities has been performed to verify the applicability of PASCAL. In this study, as a part of the verification activities, a working group was established in Japan, with seven organizations from industry, universities and institutes voluntarily participating as members. Through one year activities, the applicability of PASCAL for structural integrity assessments of domestic RPVs was confirmed with great confidence. This paper presents the details of the verification activities of the working group including the verification plan, approaches and results.

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Engineering Criticality Assessments of Floating Offshore Platforms Based on Time Domain Structural Response Analysis

10.1115/omae2021-63796 ◽

2021 ◽

Author(s):

Jeffrey O’Donnell ◽

Johyun Kyoung ◽

Sagar Samaria ◽

Anil Sablok

Keyword(s):

Fracture Mechanics ◽

Time Domain ◽

Structural Integrity ◽

Structural Response ◽

Life Extension ◽

Response Analysis ◽

Offshore Platforms ◽

Industry Standards ◽

Offshore Industry ◽

Integrity Assessments

Abstract This paper presents a time-domain S-N fatigue analysis and an approach to reliable and robust engineering criticality assessments to supplement or provide an alternative to S-N fatigue assessments of offshore platform structures based on time domain structural response analysis. It also provides recommendations for industry standards to improve guidance for structural integrity assessments of offshore platforms using fracture mechanics. Demand continues to grow in the offshore industry to attain value from captured operational data for a number of purposes, including the reduction of uncertainties in structural integrity assessments during design and over the operational lifetime of floating offshore platforms. Recent advances in time domain structural analysis technology demonstrate substantially more accurate assessments of non-linear platform loadings and responses with enhanced computational efficiency. The current S-N approach for fatigue design and integrity assessments calculates a fatigue damage factor that does not address how loading occurs over time (ABS, DNVGL-RP-C203). For the present study, engineering criticality assessments (ECAs) based on fracture mechanics theory (BS 7910) are applied utilizing time-domain loading information theory. The ECA returns the smallest initial flaws that can grow to a critical size during a design lifetime, which can serve as an indicator of acceptability during design, a technical basis for in-service inspection intervals and facilitates asset integrity and life extension assessments. Critical initial flaws are calculated using the Paris Law (BS 7910) and cumulative fatigue crack growth in two ways: with and without an integrated and consistent check for fracture instability. The results are compared with those from S-N fatigue analyses and recommendations are provided.

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Application of Probabilistic Fracture Mechanics to Reactor Pressure Vessel Using PASCAL4 Code

Journal of Pressure Vessel Technology ◽

10.1115/1.4048103 ◽

2020 ◽

Vol 143 (2) ◽

Author(s):

Kai Lu ◽

Jinya Katsuyama ◽

Yinsheng Li ◽

Shinobu Yoshimura

Keyword(s):

Fracture Mechanics ◽

Power Plants ◽

Structural Integrity ◽

Pressure Vessels ◽

Pressurized Water ◽

Integrity Assessment ◽

Thermal Transients ◽

Probabilistic Fracture Mechanics ◽

Integrity Assessments ◽

Reactor Pressure

Abstract Probabilistic fracture mechanics (PFM) is considered to be a promising methodology in structural integrity assessments of pressure-boundary components in nuclear power plants since it can rationally represent the inherent probabilistic distributions for influence parameters without over-conservativeness. To strengthen the applicability of PFM methodology in Japan, Japan Atomic Energy Agency has developed a PFM analysis code PASCAL4 which enables the failure frequency evaluation of reactor pressure vessels (RPVs) considering neutron irradiation embrittlement and thermal transients. PASCAL4 is expected to make a significant contribution to the probabilistic integrity assessment of Japanese RPVs. In this study, PFM analysis for a Japanese model RPV in a pressurized water reactor (PWR) was conducted using PASCAL4, and the effects of nondestructive examination (NDE) and neutron flux reduction on failure frequencies of the RPV were quantitatively evaluated. From the analysis results, it is concluded that PASCAL4 is useful for probabilistic integrity assessments of embrittled RPVs and can enhance the applicability of PFM methodology.

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Two-parameter fracture mechanics and circumferential crack growth in surface cracked pipelines using line-spring elements

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2007.03.023 ◽

2008 ◽

Vol 75 (1) ◽

pp. 17-30 ◽

Cited By ~ 22

Author(s):

E. Berg ◽

B. Skallerud ◽

C. Thaulow

Keyword(s):

Fracture Mechanics ◽

Crack Growth ◽

Circumferential Crack ◽

Two Parameter

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Structural Integrity Assessments for Validating Directed Energy Deposition Repairs of Integrally Bladed Rotor

10.1115/1.0002681v ◽

2021 ◽

Author(s):

Onome Scott-Emuakpor ◽

Tommy George ◽

Brian Ruynon ◽

Andrew Goldin ◽

Casey Holycross ◽

...

Keyword(s):

Energy Deposition ◽

Structural Integrity ◽

Directed Energy Deposition ◽

Bladed Rotor ◽

Directed Energy ◽

Integrity Assessments

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Numerical Methods to Predict Distortion in Welded Components

Volume 6: Materials and Fabrication, Parts A and B ◽

10.1115/pvp2008-61497 ◽

2008 ◽

Author(s):

N. A. Leggatt ◽

R. J. Dennis ◽

P. J. Bouchard ◽

M. C. Smith

Keyword(s):

Residual Stress ◽

Numerical Methods ◽

Structural Integrity ◽

Large Strain ◽

Stress Fields ◽

Specimen Thickness ◽

Single Bead ◽

Stress Profiles ◽

Welding Processes ◽

Integrity Assessments

Numerical methods have been established to simulate welding processes. Of particular interest is the ability to predict residual stress fields. These fields are often used in support of structural integrity assessments where they have the potential, when accurately characterised, to offer significantly less conservative predictions of residual profiles compared to those found in assessment codes such as API 579, BS7910 and R6. However, accurate predictions of residual stress profiles that compare favourably with measurements do not necessarily suggest an accurate prediction of component distortions. This paper presents a series of results that compare predicted distortions for a variety of specimen mock-ups with measurements. A range of specimen thicknesses will be studied including, a 4mm thick DH-36 ferritic plate containing a single bead, a 4mm thick DH-36 ferritic plate containing fillet welds, a 25mm thick 316L austenitic plate containing a groove weld and a 35mm thick esshete 1250 austenitic disc containing a concentric ring weld. For each component, distortion measurements have been compared with the predicted distortions with a number of key features being investigated. These include the influence of ‘small’ vs ‘large’ strain deformation theory, the ability to predict distortions using simplified analysis methods such as simultaneous bead deposition and the influence of specimen thickness on the requirement for particular analysis features. The work provides an extremely useful insight into how existing numerical methods used to predict residual stress fields can be utilised to predict the distortions that occur as a result of the welding fabrication process.

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