A Basic Procedure for the Integrity Assessment of Structural Steels Containing Notches

2016 ◽  
Author(s):  
Sergio Cicero ◽  
Virginia Madrazo ◽  
Tiberio García
Keyword(s):  
Theoretical Framework ◽  
Structural Steels ◽  
Notch Effect ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Basic Procedure ◽  
Failure Assessment ◽  
Different Temperatures ◽  
Fracture Tests

This paper presents a basic procedure for the integrity assessment of structural steels containing notches. It is based on the work developed by the authors in the last five years analyzing the notch effect in structural steels, with the Theory of Critical Distances as the main theoretical framework. The procedure combines the notch effect corrections provided by this theory with a basic Failure Assessment Diagram, and has been successfully validated through its application to 394 fracture tests performed on 4 different steels working at different temperatures.

Structural Integrity Assessment of Notched Components

2011 ◽  
Author(s):  
Sergio Cicero ◽  
Virginia Madrazo ◽  
Isidro Carrascal ◽  
Miguel Laporta
Keyword(s):  
Structural Integrity ◽  
Notch Effect ◽  
Single Edge ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Notched Components ◽  
Notch Analysis

This paper analyzes the notch effect and presents a methodology, based on failure assessment diagrams and the notch analysis approaches based on the theory of critical distances, for the structural integrity assessment of notched components, which allows more accurate structural analyses to be made. The methodology is applied to a set of tests performed on PMMA single edge notched bending (senb) specimens, providing better results than those obtained when the analysis is performed considering that notches behave as cracks.

Limits of Applicability of the Notch Failure Assessment Diagram

2018 ◽  
Author(s):  
Anthony J. Horn ◽  
Chris Aird
Keyword(s):  
Structural Integrity ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Mechanical Damage ◽  
Root Radius ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Notch Root Radius ◽  
Failure Assessment ◽  
Sharp Crack

Structural integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as those associated with lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper uses mechanistic modelling to define the limits of applicability of the NFAD approach in terms of ρ/a, where ρ is the notch root radius and a is the notch depth. The work concludes that the NFAD can be used to assess notches with ρ/a values of up to unity.

Structural Integrity Assessment of Notched Components Using the Master Curve Methodology and Failure Assessment Diagrams

2015 ◽  
Author(s):  
Tiberio Garcia ◽  
Sergio Cicero ◽  
Virginia Madrazo
Keyword(s):  
Master Curve ◽  
Structural Integrity ◽  
Reference Temperature ◽  
Integrity Assessment ◽  
Apparent Fracture Toughness ◽  
Failure Assessment ◽  
Crack Type ◽  
Fracture Tests ◽  
Cracked Specimens ◽  
Notched Components

This paper proposes a methodology for the structural integrity assessment of notched components. It combines failure assessment diagrams and a notch analysis approach based on the application of the Master Curve methodology for the prediction of the apparent fracture toughness of ferritic-pearlitic steels in notched conditions. This approach considers a new parameter named the notch reference temperature (T0N), which is different from the reference temperature (T0) obtained in cracked specimens and varies with the notch radius. With this purpose, the methodology has been applied to a set of fracture tests on steel S275JR, with notch radii ranging from 0 mm (crack-type defects) up to 2.0 mm and testing temperatures from −120°C up to 40°C. The methodology improves significantly the results obtained under the assumption that notches behave as cracks.

Development of Guidance for the Assessment of Non-Sharp Defects Using the Notch Failure Assessment Diagram

2016 ◽  
Author(s):  
Anthony J. Horn ◽  
Sergio Cicero ◽  
Adam Bannister ◽  
Peter J. Budden
Keyword(s):  
Structural Integrity ◽  
Fatigue Cracks ◽  
Mechanical Damage ◽  
Fe Analysis ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Wide Range ◽  
Failure Assessment ◽  
Sharp Crack ◽  
Safety Assessments

Structural integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper presents the first stage of on-going work to validate an NFAD method and to develop guidance for its application in safety assessments. The work uses 3D Finite Element (FE) Analysis in conjunction with a wide range of test data on non-sharp defects as a basis for validation. The paper also develops some practical guidance on the treatment of Lüders strain in the FE analysis of specimens containing notches instead of fatigue pre-cracks.

Validation of the Proposed R6 Method for Assessing Non-Sharp Defects

2017 ◽  
Author(s):  
Anthony J. Horn ◽  
Sergio Cicero ◽  
Adam Bannister ◽  
Peter J. Budden
Keyword(s):  
Structural Integrity ◽  
Fatigue Cracks ◽  
Mechanical Damage ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Second Stage ◽  
Lack Of Fusion ◽  
Wide Range ◽  
Failure Assessment ◽  
Sharp Crack

Structural integrity assessment codes such as R6 [1] and BS7910 [2] provide guidance on the assessment of flaws that are assumed to be infinitely sharp using the Failure Assessment Diagram (FAD). In many cases, such as fatigue cracks, this assumption is appropriate, however it can be pessimistic for flaws that do not have sharp tips such as lack of fusion, porosity or mechanical damage. Several Notch Failure Assessment Diagram (NFAD) methods have been proposed in the literature to quantify the additional margins that may be present for non-sharp defects compared to the margins that would be calculated if the defect were assumed to be a sharp crack. This paper presents the second stage of validation work, using 3D Finite Element (FE) Analyses and a wide range of test data on non-sharp defects, to validate an NFAD method proposed for inclusion in R6 and to quantify the errors caused by various approximations in the method.

Integrity Assessment of Defected Structure at High Temperature With a Material Database

2010 ◽  
Author(s):  
Zhengdong Wang ◽  
Fu-Zhen Xuan ◽  
Shan-Tung Tu
Keyword(s):  
High Temperature ◽  
Crack Size ◽  
Pressure Vessels ◽  
Time Dependent ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Base Materials ◽  
Axial Tension ◽  
Failure Assessment ◽  
Dependent Failure

The basic theory of Time Dependent Failure Assessment Diagram (TDFAD) is introduced in this paper to be modified for cracks in mismatched welds at high temperature. A time-dependent failure assessment curve is constructed using the method of R6 Option 2. This curve depends not only on the geometry and crack size but also on the mechanical properties of both weld and base materials. The application of such an approach is given to an internal circumferentially defected welded-cylinder under axial tension. An engineering tool of integrity assessment for defected structure at high temperature has been developed for a decade based on the Time Dependent Failure Assessment Diagram (TDFAD) technology for pressure vessels. The software is illustrated in this paper by framework and interfaces and some industrial cases are introduced to show the procedure of the assessment by using the software. A high temperature material database (HTMD) of main properties for typical high temperature steels and alloys is constructed to meet the needs of the safety assessment of the pressure vessels and other structures. The structure of the database is shown in the paper with some tables and charts.

Use of the Failure Assessment Diagram to Evaluate the Safety of the Reactor Pressure Vessel

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Mingya Chen ◽  
Feng Lu ◽  
Rongshan Wang
Keyword(s):  
Pressure Vessel ◽  
Failure Modes ◽  
Mechanical Load ◽  
Reactor Pressure Vessel ◽  
Plastic Collapse ◽  
Integrity Assessment ◽  
Failure Assessment Diagram ◽  
Single Criterion ◽  
Failure Assessment ◽  
Reactor Pressure

Analysis of multiple failure modes is the key element of the integrity evaluation of the nuclear reactor pressure vessel (RPV). While the simple single-criterion failure code provides the guidance for structural integrity, the guidance ignores the interaction between fast fracture and plastic collapse. In this paper, the differences between the reserve factor (RF) in the R6 two-criteria failure procedure and the safety coefficient (SC) in the single-criterion failure code were compared. Based on 3D finite element (FE) analyses, the option 3 failure assessment diagram (FAD) of the beltline of the RPV was established according to the R6 basic route and alternative approaches, respectively. Also, the nonconservation of the secondary stress correction parameter ρ was reviewed. In this paper, it was shown that the effect of crack sizes on the FAD is considered to be limited, and the influence of the thermal stress on the FAD is obvious in the transition region of the failure assessment curve (FAC). The FAD only considering the mechanical load encloses the FAD considering the thermal–mechanical load for the Lr smaller than 1, but it is contrary when the Lr is bigger than 1. It is not enough to just satisfy the requirement in the IWB-3612 of the ASME code because the risk of plastic-collapse failure is ignored. And in this study, the maximum nonconservation of the fracture toughness RF is more than 7% due to the approximate value of ρ. Accordingly, the accurate method in the R6 procedure should be used in the integrity assessment of the RPV under the faulted transient.

Estimation of the V-Factor for Circumferentially Cracked Pipes Under Combined Thermal and Mechanical Stresses Using a Strain-Based Failure Assessment Diagram

2011 ◽  
Author(s):  
Chang-Young Oh ◽  
Yun-Jae Kim ◽  
Dong-il Ryu ◽  
P. J. Budden ◽  
R. A. Ainsworth
Keyword(s):  
Finite Element ◽  
Thermal Load ◽  
Thermal Stresses ◽  
Mechanical Stresses ◽  
Estimation Methods ◽  
Finite Element Analyses ◽  
3 Dimensional ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Dimensional Finite Element

This paper presents finite element solutions for elastic-plastic J for circumferentially cracked pipes under combined mechanical and thermal loads in terms of the V/Vo factor used within a strain-based failure assessment diagram. In this study, 3-dimensional finite element analyses are conducted to calculate the V-factor under combined mechanical and thermal load. It is found that estimation of V/Vo is sensitive to the method used for its evaluation. For larger thermal stresses, currently proposed estimation methods are overly conservative.

Defective Pipeline Fatigue-Life Prediction Using Failure Assessment Diagram Technique

2004 ◽  
Author(s):  
Jinheng Luo ◽  
Xinwei Zhao ◽  
Qingren Xiong ◽  
Chunyong Huo
Keyword(s):  
Fatigue Life ◽  
Evaluation System ◽  
Life Prediction ◽  
Safety Evaluation ◽  
Load Ratio ◽  
Test System ◽  
Full Scale ◽  
Oil Pipeline ◽  
Failure Assessment Diagram ◽  
Failure Assessment

The life prediction, whose results can be used to define the inspection, repair or replacement cycle of in-service pipeline, is a main component of safety assessment of gas and oil pipeline. At present, failure Assessment Diagram (FAD) technique has been widely used in quantitative engineering safety evaluation system of pipeline that contains crack-like flaws. In past work, the authors developed a very useful model to predict the fatigue life of defective pipeline and established a computer calculating method. Based on FAD technique, toughness ratio and load ratio are calculated repeatedly with every crack increment in the model. With the self-developed full-scale test system, the full-scale pipe fatigue test was collected to verify the applicability of this method.

scholarly journals Effect of the Strain Rate on the Fracture Behaviour of High Pressure Pre-Charged Samples

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1417
Author(s):  
Guillermo Álvarez Díaz ◽  
Tomás Eduardo García Suárez ◽  
Cristina. Rodríguez González ◽  
Francisco Javier Belzunce Varela
Keyword(s):  
Fracture Toughness ◽  
High Pressure ◽  
Hydrogen Embrittlement ◽  
Strain Rate ◽  
Fracture Behaviour ◽  
Structural Steels ◽  
Gaseous Hydrogen ◽  
Displacement Rate ◽  
Steel Strength ◽  
Fracture Tests

The aim of this work is to study the effect of the displacement rate on the hydrogen embrittlement of two different structural steels grades used in energetic applications. With this purpose, samples were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h. Then, fracture tests of the pre-charged specimens were performed, using different displacement rates. It is showed that the lower is the displacement rate and the largest is the steel strength, the strongest is the reduction of the fracture toughness due to the presence of internal hydrogen.

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