Determination of J-Integral Using the Load-COD Record for Circumferential Through-Wall Cracked Pipes

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Crack Opening ◽  
Estimation Method ◽  
J Integral ◽  
Opening Displacement ◽  
Element Analysis ◽  
Load Line ◽  
Load Line Displacement ◽  
Η Factor ◽  
J Estimation

The present paper provides experimental J estimation equation based on the load-crack opening displacement (COD) record for testing the circumferential through-wall cracked pipe under combined tension and bending. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic η-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks (small crack angle), whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

A Method of J Testing Based on Crack Opening Displacement for Circumferential Through-Wall Cracked Pipes under Combined Tension and Bending

2006 ◽  
Vol 110 ◽  
pp. 63-70
Author(s):  
Nam Su Huh ◽  
Ludwig Stumpfrock ◽  
Eberhard Roos ◽  
Yun Jae Kim ◽  
Young Jin Kim
Keyword(s):  
Crack Opening Displacement ◽  
Conventional Method ◽  
Crack Opening ◽  
Estimation Method ◽  
Combined Loading ◽  
Resistance Curve ◽  
Opening Displacement ◽  
Load Line ◽  
Load Line Displacement ◽  
Leak Before Break

Application of the leak-before-break concept to nuclear piping requires accurate fracture mechanics assessment on pipes with postulated circumferential through-wall crack subject to combined tension and bending. One important element is determination of relevant J-resistance curve for pipes under combined loading. This paper provides experimental J estimation method for the circumferential through-wall cracked pipe under combined tension and bending, based on the load-crack opening displacement (COD) record to estimate J-resistance curve. To give confidence in the proposed method, the J results from detailed elastic-plastic finite element (FE) analysis are also compared with estimated J based not only on proposed method but also on conventional method using load-load line displacement, which shows that estimated J based on the proposed method provides reliable J estimates regardless of analysis condition, on the other hand, the conventional method using the load-load line displacement record gives erroneous results for shallow cracks.

Applicability of J Estimation Procedures for Overmatched SE(T) Fracture Specimens

2010 ◽  
Author(s):  
Lenin M. Paredes ◽  
Henrique S. S. Carvalho ◽  
Claudio Ruggieri
Keyword(s):  
Primary Objective ◽  
Weld Strength ◽  
Evaluation Procedure ◽  
Single Edge ◽  
Load Line ◽  
Load Line Displacement ◽  
Edge Notch ◽  
Η Factor ◽  
Fracture Specimens ◽  
J Estimation

This work focuses on the evaluation procedure to determine the elastic-plastic fracture toughness J-integral based upon the η-method for welded SE(T) fracture specimens. The primary objective of this investigation is to address the significance of the η-factor on accurate and robust estimates of J clamped single edge notch tension (SE(T)) specimens using load-displacement records. Very detailed non-linear finite element analyses for plane-strain models provide the evolution of load with increased load-line displacement to define the applied load as a separable function dependent upon crack geometry, strength mismatch level and specimen deformation. The analyses reveal that η-factors for clamped SE(T) fracture specimens based on load-line displacement (LLD) records and plastic area are relatively insensitive to weld strength mismatch.

Dynamic J-Integral Evaluation of Three-Point-Bend Beams with Various Geometrical Dimensions

2011 ◽  
Vol 488-489 ◽  
pp. 630-633
Author(s):  
Marius Gintalas ◽  
Antanas Žiliukas ◽  
Kaspars Kalniņš
Keyword(s):  
Fracture Toughness ◽  
Plastic Material ◽  
Rectangular Cross Section ◽  
Estimation Method ◽  
Displacement Curve ◽  
Elastic Plastic ◽  
Load Line ◽  
Load Line Displacement ◽  
Specimen Test

J-Integral is the main effective and commonly used tool for cracked elastic-plastic material resistance assessment. Determination of fracture toughness under impact loading conditions is related with problems of crack length measurement. Nevertheless, current experimental techniques restrict the specimen’s geometry taking into account span and height ratio, which is equal to four. Evaluation of fracture toughness estimation method which requires only experimental load-line displacement curve of single specimen is research object of dynamic fracture mechanics. This article proposes an approach of impact fracture toughness determination of elastic-plastic steel from single any size specimen test. Load-line displacement data obtained from three-point-bending tests of rectangular cross section specimens with V form single edge notch was used for J-integral calculation. Five series of specimens with different geometry were manufactured from ductile steel and tested.

Numerical Analysis for Determination of the J Integral and Crack Opening Displacement in the Cracked Aluminum Plates Repaired with FML Composite Patches

2012 ◽  
Vol 12 (21) ◽  
pp. 2259-2265
Author(s):  
Gholamhassan Payganeh ◽  
Faramarz Ashenai Ghasemi ◽  
Ali Pourkamali Anaraki ◽  
Ahmad Fallah Rahmatabad
Keyword(s):  
Numerical Analysis ◽  
Crack Opening Displacement ◽  
Crack Opening ◽  
J Integral ◽  
Opening Displacement ◽  
Aluminum Plates

Estimates of Plastic J-Integral and Crack Opening Displacement Considering Circumferential Transition Crack From Surface to Through-Wall Crack in Cylinder

2013 ◽  
Author(s):  
Doo-Ho Cho ◽  
Young-Hwan Choi ◽  
Han-Beom Surh ◽  
Jae-Boong Choi ◽  
Nam-Su Huh ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
J Integral ◽  
Opening Displacement ◽  
Element Analysis ◽  
Tp 316 ◽  
Reference Stress ◽  
Strain Data ◽  
Plastic Influence Functions ◽  
Integrity Assessments

The present paper provides the enhanced estimation of plastic J-integral and crack opening displacement (COD) for circumferential transition crack from surface to through-wall crack in cylinder based on detailed finite element analysis. The effects of circumferential transition crack on plastic J-integral and crack opening displacement have been systematically investigated for practical ranges of cylinder geometries and materials of interest. Then, the plastic influence functions (h1, h2) employed in the GE/EPRI method have been proposed to quantify those effects on plastic J-integral and COD. Furthermore, the J-integral and COD estimations based on the reference stress method using optimized reference load have also been introduced for circumferential non-idealized TWC in cylinder. Then, in order to gain the confidence in the proposed methods, the results from those proposed estimates were compared with elastic-plastic FE results by using actual stress-strain data and Ramberg-Osgood fit constants for TP 316 stainless steel. The present results can be expected to apply on various structure integrity assessments and to accurate plastic J-integral and COD estimation for circumferential non-idealized TWC in cylinder.

Modified J Estimation by GE/EPRI Method for Circumferential Surface Cracked Pipes Under Bending or Combined Bending and Pressure Loads

2011 ◽  
Author(s):  
Jing Zhang ◽  
Chang-Jun Liu ◽  
Fu-Zhen Xuan ◽  
Pei-Ning Li
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
Estimation Method ◽  
J Integral ◽  
Element Analysis ◽  
Shape Factors ◽  
Failure Assessment ◽  
Integral Estimation ◽  
J Estimation

In order to assess the structural integrity of the components in nuclear power plants, it is necessary to accurately evaluate the J-integral. EPRI J-integral estimation method has been widely used. However for the pipes with circumferential surface cracks, since the solutions of fully plastic factors H1 were few under the combined pressure and bending loading condition. In such a case, EPRI J-integral might be non-conservative in elastic-plastic transition zone. Considering the problems, detailed finite element analysis (FEA) were conducted in this work, and H1, shape factors F were provided for the pure pressure, pure bending, and combined pressure and bending conditions. The reasons for non-conservatism of EPRI method were discussed, and a modified J estimation method was developed. For validation, failure assessment curves (FACs) were employed to compare the proposed J-integral estimation, EPRI J-integral and FEA method. The results showed that FAC based on the proposed J-integral method agreed well with FEA result, which provided good confidence in the use of this method.

Significance of the Plastic Eta Factor in J Estimation Procedures for Tensile SE(T) Fracture Specimens

2010 ◽  
Author(s):  
Henrique S. S. Carvalho ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Load Line ◽  
Load Line Displacement ◽  
Estimation Procedures ◽  
Η Factor ◽  
Fracture Specimens

Current evaluation procedures for toughness measurements, such as the J-integral and the crack tip opening displacement (CTOD), focus primarily on single-specimen estimation schemes which essentially relate the plastic contribution to the strain energy with J based upon a plastic η-factor. This work addresses the significance of the η-factor on estimation procedures for J in pin-loaded and clamped single edge notch tension (SE(T)) specimens using load-displacement records. Very detailed non-linear finite element analyses for plane-strain models provide the evolution of load with increased load-line displacement and crack mouth opening displacement to define the applied load as a separable function dependent upon crack geometry and material deformation. The analyses reveal that η-factors based on load-line displacement (LLD) are very sensitive to plasticity changes at locations remote from the crack-tip region. In contrast, η-factors based on crack mouth opening displacement (CMOD) appear less affected by remote crack-tip plasticity. Overall, the present results provide a strong support to use η-based procedures in toughness measurements for clamped SE(T) fracture specimens.

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