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.

A Statistical Framework for Analysing Weld Residual Stresses for Structural Integrity Assessment

2008 ◽  
Author(s):  
Brahim Nadri ◽  
Peter J. Bouchard ◽  
Christopher E. Truman ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Spatial Distribution ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Measured Data ◽  
Integrity Assessment ◽  
Statistical Framework ◽  
Weld Residual Stress ◽  
Four Levels

Thermal and mechanical processes during welding introduce complex three-dimensional distributions of residual stress. Management of residual stresses represents a major challenge for engineers in order to achieve safe and reliable operation of existing engineering plants. Consideration of how such stresses vary through the wall within welded components is critical in structural integrity assessments. Development of more accurate and realistic weld residual stress profiles through statistical analysis of high quality measured data is highly desirable. This can not be achieved without adequate interpretation of measured weld residual stress data through the development of an appropriate framework. This paper proposes a framework for analysing measured data at four levels of complexity depending on its spatial distribution. The framework provides clear guidance on how to perform appropriate statistical analyses of residual stress data and proposes how to deal with some practical issues that may arise from various stress measurements; for example the gauge size, spatial distribution, measurement uncertainties and data analysis assumptions. Parts of the proposed framework are then applied to measured stress data in a simple welded laboratory test specimen.

scholarly journals A New Characterization Parameter of out-of-plane Constraint for C(T) Specimens

2018 ◽  
Vol 179 ◽  
pp. 02006
Author(s):  
Zhao Lingyan ◽  
Cui Yinghao ◽  
Yang Fuqiang
Keyword(s):  
Structural Integrity ◽  
Three Dimensional ◽  
Equivalent Plastic Strain ◽  
Crack Tip ◽  
Stress Fields ◽  
Integrity Assessment ◽  
Out Of Plane ◽  
Dimensional Finite Element ◽  
Material Fracture ◽  
Three Dimensional Finite Element

As the resistance of structures against the crack-tip plastic deformation, constraints has attracted much attention in the research of material fracture behaviour. In order to increase the accuracy of structural integrity assessment, many characterization parameters of in-plane and out-of-plane constraints have been considered and proposed in the last few decades. Three-dimensional finite element analyses have been conducted for five C(T)50 specimens with different out-of-plane constraint. The distributions of four constraint parameters (σ22/σ0, Tz, h and Dp) along crack fronts were calculated. To characterize the out-of-plane constraint, the capability of constraint parameters such as σ22/σ0, Tz, h and Dp were analyzed and compared. Results show that, compared with the three constraint parameters (σ22/σ0, Tz and h) based on crack-tip stress fields, the parameter Dp based on crack-tip equivalent plastic strain is more sensitive to out-of-plane constraint, and may effectively characterize the out-of-plane constraint.

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 ....

scholarly journals Numerical aspects for efficient welding computational mechanics

2014 ◽  
Vol 18 (suppl.1) ◽  
pp. 139-148
Author(s):  
Tarek Aburuga ◽  
Aleksandar Sedmak ◽  
Zoran Radakovic
Keyword(s):  
Residual Stresses ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Mechanical Analysis ◽  
Tensile Test Specimen ◽  
Integrity Assessment ◽  
Mass Scaling ◽  
Three Dimensional Models ◽  
Thermal Mechanical Analysis

The effect of the residual stresses and strains is one of the most important parameter in the structure integrity assessment. A finite element model is constructed in order to simulate the multi passes mismatched submerged arc welding SAW which used in the welded tensile test specimen. Sequentially coupled thermal mechanical analysis is done by using ABAQUS software for calculating the residual stresses and distortion due to welding. In this work, three main issues were studied in order to reduce the time consuming during welding simulation which is the major problem in the computational welding mechanics (CWM). The first issue is dimensionality of the problem. Both two- and three-dimensional models are constructed for the same analysis type, shell element for two dimension simulation shows good performance comparing with brick element. The conventional method to calculate residual stress is by using implicit scheme that because of the welding and cooling time is relatively high. In this work, the author shows that it could use the explicit scheme with the mass scaling technique, and time consuming during the analysis will be reduced very efficiently. By using this new technique, it will be possible to simulate relatively large three dimensional structures.

Evaluation of Residual Stresses in Butt Welded Joint of Dissimilar Material by FEM

2017 ◽  
Vol 754 ◽  
pp. 268-271 ◽  
Author(s):  
Raffaele Sepe ◽  
M. Laiso ◽  
A. de Luca ◽  
Francesco Caputo
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Arc Welding ◽  
Structural Integrity ◽  
Welded Joint ◽  
Dissimilar Material ◽  
Fe Model ◽  
Butt Joints ◽  
Integrity Assessment ◽  
Steel Joints

The study proposed within this paper deals with an application of finite element techniques to the thermo-structural analysis of a dissimilar butt-welded joint. Residual stresses induced by the fusion arc-welding of steel joints in power generation plants are a concern to the industry. Nowadays, the application of finite element method appears to be a very efficient method for the prediction and the investigation of the weld-induced residual stresses, nevertheless the detailed modelling of all phenomena involved in such process is still challenging. The structural integrity assessment of welded structures strongly requires a deep investigation of weld-induced residual stresses in order to be compliant with safety requirement of power plant. The longitudinal and transversal residual stresses in dissimilar material butt joints of 8 mm thick for V-groove shape were studied. The developed thermo-mechanical FE model as well as the simulation procedures are detailed and results are discussed. As a result of such work, it has been found out that residual stresses in the two dissimilar plates are characterized by very different magnitudes and distribution.

Dynamic Fracture Parameters and Calculations for 3-D Cracks

2003 ◽  
Author(s):  
Wing Cheng ◽  
Shigeru Itoh
Keyword(s):  
Dynamic Loading ◽  
Dynamic Fracture ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Welding Process ◽  
Fracture Parameter ◽  
Integrity Assessment ◽  
Fracture Parameters ◽  
Cracked Structures ◽  
Geometrical Factors

Welded structures such as armor fighting vehicles, shipboard structures or munitions systems are required to sustain intense and rapidly applied dynamic loading due to gun firings, impact of enemy munitions and extreme loading from accident scenarios. Flaws are normally found in various extents in welds depending on quality control of the welding process. It is important to determine critical flaw sizes of three-dimensional cracks in a welded joint under dynamic loading introduced by the above scenarios. Calculation of dynamic fracture parameters of the three-dimensional cracks of various geometrical factors at different locations is important for use the crack growth evaluation, flacture and structural integrity assessment. This paper summarizes the methodologies and results of the dynamic fracture parameter calculations for stationary three-dimensional cracks in cracked structures subjected to both static and dynamic loads.

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.

Plastic Limit Loads for Through-Wall Cracked Pipes Using Finite Element Limit Analysis

2006 ◽  
Vol 321-323 ◽  
pp. 724-728
Author(s):  
Nam Su Huh ◽  
Yoon Suk Chang ◽  
Young Jin Kim
Keyword(s):  
Finite Element ◽  
Limit Analysis ◽  
Structural Integrity ◽  
Three Dimensional ◽  
Limit Load ◽  
Plastic Behavior ◽  
Plastic Limit ◽  
Integrity Assessment ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic

The present paper provides plastic limit load solutions for axial and circumferential through-wall cracked pipes based on detailed three-dimensional (3-D) finite element (FE) limit analysis using elastic-perfectly plastic behavior. As a loading condition, both single and combined loadings are considered. Being based on detailed 3-D FE limit analysis, the present solutions are believed to be valuable information for structural integrity assessment of cracked pipes.

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.

Standardisation on Measurement and Interpretation of Residual Stress Data

2019 ◽  
Author(s):  
Ali Mirzaee-Sisan ◽  
P. John Bouchard ◽  
Foroogh Hosseinzadeh
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Practice Guidelines ◽  
Structural Integrity ◽  
Good Practice ◽  
Critical Assessment ◽  
Numerical Prediction ◽  
Specific Technique ◽  
Integrity Assessment

Abstract This paper highlights many unanswered questions relating to the characterisation of residual stresses in weldments and their treatment in engineering critical assessment and fitness for service assessment codes and standards. The need for an overarching standardisation framework is identified which goes beyond developing good practice guidelines for numerical prediction or measurement using a specific technique. The framework should cover all uncertainties and possible errors in measuring, simulating and interpreting residual stress in the context of structural integrity assessment.

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