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.

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.

On the Constraint-Based Failure Assessment of Surface Cracks in T-Plate Welded Joints

2003 ◽  
Author(s):  
X. Wang ◽  
R. Bell ◽  
S. B. Lambert
Keyword(s):  
Lower Bound ◽  
Welded Joints ◽  
Structural Integrity ◽  
Constraint Effect ◽  
Engineering Structures ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Recent Developments ◽  
Failure Predictions ◽  
Crack Tip Constraint

The loss of crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. However, conventional failure assessment schemes (CEGB-R6, BS-7910) use lower bound toughness obtained from highly constrained test specimens. Cracks in many real engineering structures are not highly constrained, which makes failure predictions using conventional failure assessment schemes based on lower bound fracture toughness values overly pessimistic. Excessive pessimism in the structural assessment can lead to unwarranted repair or decommissioning of structures, and thus cause unneeded cost and inconvenience. Recent developments on constraint-based fracture mechanics have enabled the practical assessment of defective components including the constraint effect. For example, the recent revision of R6 and the newly developed structural integrity assessment procedures for European industry (SINTAP) have suggested a framework for failure assessments including the constraint effect. In this paper, the constraint-based failure assessment of surface cracked T-plate welded joints under tension load is presented. Different issues including the constraint-based failure assessment diagrams, the treatment of combining primary and the secondary loads, and the calculation of stress intensity factors, limit loads and constraint parameters for surface cracked T-plate joints are discussed. It is demonstrated that when the lower constraint effect is properly accounted for, the maximum allowable tensile stress level increases substantially.

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.

Instrumented Indentation Technique to Measure Flow Properties: A Novel Way to Enhance the Accuracy of Integrity Assessment

2003 ◽  
Author(s):  
Jae-Il Jang ◽  
Yeol Choi ◽  
Yun-Hee Lee ◽  
Jung-Suk Lee ◽  
Dongil Kwon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Crack Detection ◽  
Structural Integrity ◽  
Instrumented Indentation ◽  
Flow Properties ◽  
Integrity Assessment ◽  
Indentation Technique ◽  
Failure Assessment ◽  
Similar Vein ◽  
Non Destructive

While most in-field technologies for structural integrity diagnosis focus on precise crack detection, the instrumented indentation technique has emerged as one of the most practically useful technologies for non-destructive and quantitative in-field measurement of mechanical properties. In a similar vein, here an advanced indentation technique for determining tensile properties and its application to structural integrity assessment are introduced and discussed. This novel indentation technique can enhance the accuracy of fitness-for-service (FFS) assessment by application to failure assessment diagram (FAD) construction.

Reliability Analysis of Defect-Containing Structures Using Partial Safety Factors

2009 ◽  
Author(s):  
Liwu Wei
Keyword(s):  
Failure Probability ◽  
Structural Integrity ◽  
General Trend ◽  
Safety Factors ◽  
Integrity Assessment ◽  
Fracture Region ◽  
Failure Assessment ◽  
Elastic Fracture ◽  
Partial Safety Factors ◽  
Collapse Region

Some standards of structural integrity assessment such as BS 7910 and API 579-1/ASME FFS-1 recommend values of partial safety factor (PSF) applied to the deterministic engineering critical assessments of flaw-containing structures to achieve certain reliability levels. However, it is still uncertain as to whether the use of the PSFs can achieve the target reliability level specified in the codes, or excessively exceed the targets (un-conservative) or under-reach the targets (too conservative). This work was undertaken to make investigations into these issues raised from the use of PSFs through case studies involving deterministic fitness-for-service analysis incorporating PSFs and probabilistic fracture mechanics analysis. Two cases, a through-thickness crack and a surface-breaking elliptical crack in a plate subjected to tension, were considered. The results in terms of failure probability from the studied cases have shown a general trend that for each of the four PSFs recommended in BS 7910, the failure probability decreased as the assessments changed from the elastic fracture region to the plastic collapse region in the failure assessment diagram. Some over-conservatism has been found in certain situations from the use of PSFs recommended in BS 7910:2005. Cautions are given for application of the PSFs for integrity assessment of the structures and components containing flaws.

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.

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.

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.

Development of Test Guidance for Single Edge Notch Bend Fracture Toughness Specimens Containing Notches Instead of Fatigue Pre-Cracks

2015 ◽  
Author(s):  
Anthony J. Horn ◽  
Peter J. Budden
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Single Edge ◽  
Integrity Assessment ◽  
Single Edge Notch ◽  
Notched Specimens ◽  
Edge Notch ◽  
Cracked Specimens ◽  
Single Edge Notch Bend

Structural integrity assessment codes such as R6 and BS7910 provide guidance on the assessment of flaws that are assumed to be infinitely sharp. 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 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. A common feature of these methods is the need to understand how the effective toughness, characterised using the J-integral for a notch, varies with notch acuity. No comprehensive guidance currently exists for obtaining J experimentally from specimens containing notches, hence the typical approach is to use equations intended for pre-cracked specimens to calculate J for notched specimens. This paper presents a comprehensive set of test guidance for calculating J from Single Edge Notch Bend (SENB) fracture toughness specimens containing notches instead of fatigue pre-cracks. This has been achieved using 3D Finite Element Analyses to quantify the accuracy of formulae intended for pre-cracked specimens in fracture toughness testing standards ASTM E1820, BS7448-1 and ESIS P2-92 when applied to specimens containing notches. The paper quantifies the accuracy of these equations for notched SENB specimens and identifies the conditions under which the equations can lead to inaccurate measurement of J for notched specimens.

On the Constraint-Based Failure Assessment for Surface Cracked Welded Plates Under Tension

2003 ◽  
Author(s):  
X. Wang ◽  
W. Reinhardt
Keyword(s):  
Lower Bound ◽  
Structural Integrity ◽  
Constraint Effect ◽  
Engineering Structures ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Recent Developments ◽  
Failure Predictions ◽  
Crack Tip Constraint ◽  
Assessment Procedures

Conventional failure assessment schemes (CEGB-R6, BS-7910) use a lower bound toughness obtained from highly constrained test specimens. A lower crack tip constraint leads to enhanced resistance to both cleavage and ductile tearing. The cracks in many real engineering structures are not highly constrained, which makes failure predictions using conventional failure assessment schemes based on the lower bound fracture toughness overly conservative. Too much conservatism in the structural assessment can lead to unwarranted repair or decommissioning of structures, and thus cause unnecessary cost and inconvenience. Due to recent developments in constraint-based fracture mechanics, it is important to include the constraint effect in the practical assessment of defective components. For example, the recent revision of R6 and the newly developed structural integrity assessment procedures for European industry (SINTAP) have suggested a framework for failure assessments that can take the constraint effect into account. In this paper, the constraint-based failure assessment of a surface cracked welded plate under uniaxial tension load is presented. A constraint-based failure assessment diagram and a method for combining primary and the secondary loads are discussed. Finite element based correlations are used to calculate the stress intensity factors, and constraint parameters, while the limit loads are derived from existing closed form approximations. It is demonstrated that when the lower constraint effect is properly accounted for, the maximum allowable tensile stress level can increase 15% or more.

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