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.

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.

French RPV PTS Assessment: An Overview of EDF Research and Development in Progress on Thermalhydraulic, Materials and Mechanical Aspects

2003 ◽  
Author(s):  
Dominique Moinereau ◽  
Jean-Michel Frund ◽  
Henriette Churier-Bossennec ◽  
Georges Bezdikian ◽  
Alain Martin
Keyword(s):  
Structural Integrity ◽  
Three Dimensional ◽  
Crack Arrest ◽  
Pressure Vessels ◽  
Short Description ◽  
Constraint Effect ◽  
Materials Properties ◽  
Integrity Assessment ◽  
Pressurized Thermal Shock ◽  
Reactor Pressure

A significant extensive Research & Development work is conducted by Electricite´ de France (EDF) related to the structural integrity re-assessment of the French 900 and 1300 MWe reactor pressure vessels in order to increase their lifetime. Within the framework of this programme, numerous developments have been implemented or are in progress related to the methodology to assess flaws during a pressurized thermal shock (PTS) event. The paper contains three aspects: a short description of the specific French approach for RPV PTS assessment, a presentation of recent improvements on thermalhydraulic, materials and mechanical aspects, and finally an overview of the present R&D programme on thermalhydraulic, materials and mechanical aspects. Regarding the last aspect on present R&D programme, several projects in progress will be shortly described. This overview includes the redefinition of some significant thermalhydraulic transients based on some new three-dimensional CFD computations (focused at the present time on small break LOCA transient), the assessment of vessel materials properties, and the improvement of the RPV PTS structural integrity assessment including several themes such as warm pre-stress (WPS), crack arrest, constraint effect ....

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.

Engineering Critical Assessments of Ductile Pipes With Axial Flaws and High Strain Hardening Capacity

2008 ◽  
Author(s):  
Claudio Ruggieri
Keyword(s):  
Strain Hardening ◽  
Structural Integrity ◽  
Steel Pipes ◽  
Integrity Assessment ◽  
Ductile Materials ◽  
Axial Crack ◽  
Open Issue ◽  
Failure Predictions ◽  
Low Constraint ◽  
Assessment Problems

ECA procedures of crack-like defects based upon the FAD philosophy have undergone extensive developments in the past decade to form the basis for industrial codes and guidelines for structural integrity assessments. However, the application (and validation) of these procedures in defect assessments of structural components made of ductile materials under low constraint conditions remains a potential open issue. A central objective of this work is to assess the capability of the failure assessment diagram methodology to predict the failure pressure of ductile pipes with planar defects having different geometries. Specifically, the present work compares the burst pressure predictions for austenitic steel pipes with axial flaws derived from two widely used FAD procedures:BS7910 and API579. Such an application serves as a prototype for a wide class of integrity assessment problems involving the effects of strain hardening properties and ductility while, at the same time, assessing the robustness of FAD procedures in failure predictions. The direct application of BS7910 procedure indicate rather large margins between the predicted and the actual (measured) failure pressures. In contrast, the API 579 procedure appears to provide better agreement with experimental data. Overall, the results validate the use of FAD-based methodologies for defect assessments of ductile pipes with axial crack-like flaws.

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.

Integrity Assessment of Spherical Pressure Components With Local Corrosion and Hot Spots

2006 ◽  
Author(s):  
Pattaramon Tantichattanont ◽  
Seshu Adluri ◽  
Rangaswamy Seshadri
Keyword(s):  
Lower Bound ◽  
Hot Spots ◽  
Structural Integrity ◽  
Hot Spot ◽  
Corrosion Damage ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Local Corrosion ◽  
Integrity Assessment ◽  
Spherical Pressure

Corrosion damage and hot spots are typical of damages that can occur in ageing pressure vessels and pipelines used in industrial processes. Internal and external corrosion could be the result of corrosive products stored inside or harsh environmental conditions on the outside. Hot spots are caused by damage due to loss of refractory lining on the inside wall of pressure components or due to maldistribution of flow containing catalyst and reactive fluids. The structural integrity of such ageing components needs to be evaluated periodically to establish the continued suitability of the vessels under operating conditions. The present paper develops a method for Level 2 (as categorized by API 579) structural integrity evaluations of spherical pressure vessels containing local corrosion damage or hot spot. The decay lengths for spherical shells subject to local damages have been studied based on stretching and bending effects using elastic shell theories so as to identify the reference volume participating in plastic action. A limit for “local” corroded spot or hot spot is defined by the size of damage that an onset of pure membrane action occurs inside the damaged area. The size of damage indicating the crossover from dominance of stretching effects on the damage behavior to that of bending effects is also presented. The lower bound recommended “remaining strength factors” for spherical pressure vessels containing corrosion or hot spot are formulated by application of Mura’s integral mean of yield criterion and the improved lower bound mα-multiplier. Three alternative recommendations are proposed. The effectiveness of the proposed methods is evaluated and demonstrated through illustrative examples and comparison with inelastic finite element analyses.

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.

Correlation of Fracture Toughness With Charpy Impact Energy for Low Alloy, Structural Steel Welds

2017 ◽  
Author(s):  
Kleber E. Bianchi ◽  
Vitor Scarabeli Barbosa ◽  
Rafael Savioli ◽  
Paulo Eduardo Alves Fernandes ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Impact Energy ◽  
Welded Joints ◽  
Structural Integrity ◽  
Charpy Impact ◽  
Reference Temperature ◽  
Transition Curve ◽  
Charpy Impact Energy ◽  
Integrity Assessment ◽  
Steel Welds

Correlations between Charpy impact energy and fracture toughness values have continuously been developed because of their applicability in structural integrity assessment methodologies. This also applies to the integrity analysis of welded joints, which represent material discontinuities and potential failure locus in structures. Therefore, in effective FFS methodology applications, the fracture toughness of welded joints located in critical regions should be accurately estimated. This work addresses an estimation procedure of fracture toughness values based on Charpy impact energy for low alloy, steel welds made from an ASTM A572 Gr 50 base plate material. To produce the welded joints, two processes were used: SMAW and FCAW. To ensure valid toughness test values corresponding to high constraint conditions, a strength overmatched, deeply-cracked SE(B) configuration having a weld centerline notch was adopted. The ductile-to-brittle transition curve was established by means of Charpy tests. Direct CVN correlations with fracture toughness, as well as reference temperature based correlations derived from the Master Curve approach, were evaluated. The obtained results indicate that both correlation procedures are suitable for weld metal toughness estimations based on Charpy data. However, slightly different values of correlation constants than those indicated for the base metal should be employed in the case of the reference temperature method.

A Comparison of Two- and Three-Dimensional Fracture Assessments in the Presence of Residual Stresses

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
S. J. Lewis ◽  
C. E. Truman ◽  
D. J. Smith
Keyword(s):  
Residual Stresses ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Major Effect ◽  
Probabilistic Methods ◽  
Secondary Importance ◽  
Integrity Assessment ◽  
Path Independence ◽  
Out Of Plane ◽  
Failure Predictions

The influence of various assumptions on the modeling of cleavage fracture in the presence of residual stresses was investigated. Analyses were undertaken for modified single edge notched bend specimens, manufactured from A533B ferritic steel. The influence of residual stress fields, introduced by a method of in-plane compression, was investigated through the use of a modified J-integral, designed to retain path independence in the presence of initial stress and strain fields and nonproportional loading. Application of modified J values to predict fracture using probabilistic methods, and their use in a well-known structural integrity assessment code, showed that assumptions about levels of out-of-plane constraint, material hardening behavior, and the method of crack introduction have a significant influence on the conservatism of the resulting failure predictions. It was found that more realistic modeling of crack introduction had a major effect on the accuracy of failure predictions, with the effects of material hardening being of secondary importance.

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.

Sign in / Sign up

Export Citation Format

Share Document