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.

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

2010 ◽  
Author(s):  
Claudio Ruggieri
Keyword(s):  
Strong Support ◽  
Mouth Opening ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Load Line ◽  
Load Line Displacement ◽  
Edge Notch ◽  
Load Displacement ◽  
Fracture Specimens

This work investigates application of the η-factor (which bears direct connection with laboratory toughness measurements) on accurate and robust estimates of J for clamped single edge notch tension (SE(T)) specimens made of homogeneous and welded materials using load-displacement records. Very detailed nonlinear 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, material deformation and mismatch level. The procedure enables determining the corresponding separation parameters for each specimen geometry thereby allowing evaluation of factor η derived from a load separation analysis. The study shows that η-factors based on load-displacement records defining the plastic area provide effective and accurate toughness measurements for clamped SE(T) fracture specimens. The analyses also revealed 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. Overall, the present results provide a strong support to use η-based procedures in toughness measurements using clamped SE(T) fracture specimens.

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.

Improved J and CTOD Estimation Formulas for C(T) Fracture Specimens Including Overmatched Weldments

2011 ◽  
Author(s):  
Rafael G. Savioli ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Estimation Procedure ◽  
Primary Objective ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Opening Displacement ◽  
Wide Range ◽  
Extensive Body ◽  
Fracture Specimens

This work focuses on the evaluation procedure to determine the elastic-plastic J-integral and CTOD fracture toughness based upon the η-method for C(T) fracture specimens made of homogeneous and welded steels. The primary objective of this investigation is to enlarge on previous developments of J and CTOD estimation procedures for this crack configuration while, at the same time, addressing effects of strength mismatch on the plastic η-factors. The present analyses enable the introduction of a larger set of factor η for a wide range of crack sizes (as measured by the a/W-ratio) and material properties, including different levels of weld strength mismatch, applicable to structural, pipeline and pressure vessel steels. Very detailed non-linear finite element analyses for plane-strain models of square groove, center cracked C(T) fracture specimens provide the evolution of load with increased crack mouth opening displacement required for the estimation procedure. Overall, the present study, when taken together with previous investigations, provides a fairly extensive body of results to determine parameters J and CTOD for different materials using C(T) specimens with varying overmatch conditions.

Effects of Weld Strength Mismatch on J and CTOD Estimation Procedures for SENT Fracture Specimens Based on Plastic Eta-Factors

2011 ◽  
Author(s):  
Marcelo Paredes ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Estimation Procedure ◽  
Primary Objective ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Opening Displacement ◽  
Wide Range ◽  
Extensive Body ◽  
Fracture Specimens

This work focuses on the evaluation procedure to determine the elastic-plastic fracture toughness J-integral and CTOD based upon the η-method for welded SENT fracture specimens with clamped ends. The primary objective is to gain additional understanding on the effect of weld strength mismatch on estimation techniques to determine J and CTOD fracture parameters for a wide range of a/W-ratios and mismatch levels. Very detailed non-linear finite element analyses for plane-strain and 3-D models of SENT fracture specimens with center cracked, square groove welds provide the evolution of load with increased crack mouth opening displacement and load line displacement which are required for the estimation procedure. The results show that levels of weld strength mismatch within the range 10∼20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials. The present analyses, when taken together with previous studies, provide an extensive body of results which serve to determine parameters J and CTOD for different materials using SENT specimens with varying geometries and mismatch levels.

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.

Effects of Weld Strength Mismatch on Estimation Procedures for J and CTOD Fracture Parameters Using SE(B) Specimens

2007 ◽  
Author(s):  
Gustavo H. B. Donato ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Estimation Procedure ◽  
Primary Objective ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Fracture Parameters ◽  
Wide Range ◽  
Estimation Procedures ◽  
Fracture Specimens

This work presents an exploratory development of J and CTOD estimation procedures for welded fracture specimens under bending based upon plastic eta factors and plastic rotation factors. The techniques considered include: i) estimating J and CTOD from plastic work and ii) estimating CTOD from the plastic rotational factor. The primary objective is to gain additional understanding on the effect of weld strength mismatch on estimation techniques to determine J and CTOD fracture parameters for a wide range of a/W-ratios and mismatch levels. Very detailed non-linear finite element analyses for plane-strain models of SE(B) fracture specimens with center cracked, square groove welds provide the evolution of load with increased load-line displacement and crack mouth opening displacement which are required for the estimation procedure. The results show that levels of weld strength mismatch within the range ±20% mismatch do not affect significantly J and CTOD estimation expressions applicable to homogeneous materials, particularly for deeply cracked fracture specimens. The present analyses, when taken together with previous studies, provide a fairly extensive body of results which serve to determine parameters J and CTOD for different materials using bend specimens with varying geometries and mismatch levels.

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