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 Corrosion defect harmfulness by domain failure assessment diagram

2018 ◽  
Vol 2 (3) ◽  
pp. 163-177 ◽  
Author(s):  
G. Pluvinage ◽  
◽  
O. Bouledroua ◽  
M. H. Meliani ◽  
◽  
...  
Keyword(s):  
Corrosion Defect ◽  
Failure Assessment Diagram ◽  
Failure Assessment

Constraint in the Failure Assessment Diagram Approach for Fracture Assessment

1995 ◽  
Vol 117 (3) ◽  
pp. 260-267 ◽  
Author(s):  
R. A. Ainsworth ◽  
N. P. O’Dowd
Keyword(s):  
Crack Size ◽  
Structural Constraint ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
T Stress ◽  
Fracture Assessment ◽  
The Subject ◽  
Constraint Effects ◽  
Two Parameters ◽  
Diagram Approach

This paper presents a framework for including constraint effects in the failure assessment diagram approach for fracture assessment. As parameters for describing constraint are still the subject of development, the framework is illustrated using both the elastic T-stress and the hydrostatic Q-stress. It is shown that constraint effects can be treated by modifying the shape of the failure assessment curve. In their simplest form, the modifications involve only two parameters: one quantifying the magnitude of structural constraint which depends on geometry and crack size; and the second quantifying the influence of constraint on fracture toughness.

Numerical Validation of a Strain-Based Failure Assessment Diagram Approach to Fracture

2009 ◽  
Author(s):  
Peter J. Budden ◽  
Michael C. Smith
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Present Author ◽  
Plastic Relaxation ◽  
Failure Assessment Diagram ◽  
Defect Assessment ◽  
Failure Assessment ◽  
Basic Approaches ◽  
Assessment Procedures ◽  
Diagram Approach

The basic approaches in defect assessment procedures such as R6 consider the stresses on the section containing the flaw. Such approaches can be overly conservative and lead to unacceptably small estimates of limiting defect sizes for cases where the applied loads are due to displacements or strains well in excess of yield, when significant plastic relaxation of stress occurs. The potential for over-conservative assessments has led to a renewed interest in recent years in strain-based assessment methods, in both the power and pipeline industries. Significant levels of plastic strain can be imposed across the flawed section in some cases. Recently, the present author has published a general approach to strain-based fracture that uses a strain-based failure assessment diagram (SB-FAD). This includes a range of Options similar to that of the basic R6 approach. The present paper describes some validation of the SB-FAD approach based on elastic-plastic cracked-body finite element data for plates and cylinders.

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