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.

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.

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.

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.

Experimental Observation of Front-Face-Displacement and Load-Line-Displacement in CT and Bend Specimens During Fracture Toughness Tests

2009 ◽  
Author(s):  
Bong-Sang Lee ◽  
Sang-Yoon Park ◽  
Min-Chul Kim
Keyword(s):  
Fracture Toughness ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Front Face ◽  
Analytical Relationship ◽  
Conservative Estimate ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Load Line ◽  
Load Line Displacement

The master curve method described in ASTM E1921 provides a tool for using small specimens such as sub-sized CT and PCVN specimens for standard fracture toughness testing. However, a direct measurement of the load-line displacement of small specimens is not practical for standard fracture toughness tests. Mostly, the front-face displacement or the crack mouth opening displacement can be measured and converted into the load-line displacement by using an analytical relationship proposed by several investigators. Since those relationships were deduced from numerical calculations of the loaded specimens, experimental deviations may occur because of specimen indentation, rotation and arm bending during an actual testing. It is clear that the determination of fracture toughness is influenced by the accuracy of the estimation of load-line displacement as well as the load measurement. In this study, the relationship between the load-line displacement and the front-face displacement or the crack mouth displacement was investigated experimentally by using a series of CT and Bend specimens modified to measure the two displacements simultaneously during a single test. The results showed that the front-face measurement of CT specimens may result in about 3% more conservative estimate of fracture toughness. In the case of bend specimens, the crack mouth opening displacement measurement may result in about 7% non-conservative estimate of fracture toughness than the load-line measurement.

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.

Wide Range Compliance Solutions for Various Fracture Test Specimens Using Crack Mouth Opening Displacement

2017 ◽  
Author(s):  
Claudio Ruggieri ◽  
Rodolfo F. de Souza
Keyword(s):  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Width Ratio ◽  
Fracture Test ◽  
Single Edge ◽  
Opening Displacement ◽  
Element Analysis ◽  
Single Edge Notch ◽  
Wide Range ◽  
Edge Notch

This work addresses the development of wide range compliance solutions for tensile-loaded and bend specimens based on CMOD. The study covers selected standard and non-standard fracture test specimens, including the compact tension C(T) configuration, the single edge notch tension SE(T) specimen with fixed-grip loading (clamped ends) and the single edge notch bend SE(B) geometry with varying specimen spam over width ratio and loaded under 3-point and 4-point flexural configuration. Very detailed elastic finite element analysis in 2-D setting are conducted on fracture models with varying crack sizes to generate the evolution of load with displacement for those configurations from which the dependence of specimen compliance on crack length, specimen geometry and loading mode is determined. The extensive numerical analyses conducted here provide a larger set of solutions upon which more accurate experimental evaluations of crack size changes in fracture toughness and fatigue crack growth testing can be made.

Experimental Determination of J-R Curves Using SENB Specimens and P-CMOD Data

2008 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Crack Extension ◽  
Mouth Opening ◽  
Cost Effective ◽  
Crack Mouth Opening Displacement ◽  
Simple Relationship ◽  
J Integral ◽  
Single Specimen ◽  
Opening Displacement ◽  
Load Line Displacement ◽  
Senb Specimen

Fracture toughness and J-R curves of ductile materials are often measured under the guidance of ASTM standard E1820 using the single specimen technique and the elastic unloading compliance method. For the standard single-edge notched bend [SENB] specimens, the load, load-line displacement (LLD), and crack-mouth opening displacement (CMOD) are required being measured simultaneously. The load-CMOD data are used to determine the crack extension, and the load-LLD data together with the crack extension are used to determine the J-integral values in a J-R curve test. Experiments have indicated that the CMOD measurement is very accurate, but the LLD measurement is difficult and less accurate in a fracture test on the SENB specimen. If the load-CMOD records is used to determine the crack extension and the J-integral values, experimental accuracies for the J-R curve testing would be increased, and the test costs can be reduced. To this end, this paper develops a simple relationship between LLD and CMOD that is used to convert the measured CMOD record to the corresponding LLD data, and then to calculate the J values for a growing crack in a J-R curve test on the SENB specimen using one single specimen technique. The proposed method is then verified by the experimental data of J-R curves for HY80 steel using the SENB specimens and the load-CMOD data only. The results show that the proposed method is more accurate and more cost-effective for the J-R curve testing.

Revised η-Factors for 3P SE(B) Fracture Specimens Incorporating 3-D Effects

2014 ◽  
Author(s):  
Rodolfo F. de Souza ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Mouth Opening ◽  
Estimation Procedure ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Specimen Thickness ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Wide Range ◽  
Fracture Specimens

Standardized procedures to measure cleavage fracture toughness of ferritic steels in the DBT region most commonly employ three-point bend fracture specimens, conventionally termed SE(B) or SENB specimens. The evaluation protocol of fracture toughness for these crack configurations builds upon laboratory records of load and crack mouth opening displacement (CMOD) to relate plastic work with J (or, equivalently, CTOD). The experimental approach employs a plastic η-factor to relate the macroscale crack driving force to the area under the load versus crack mouth opening displacement for cracked configurations. This work provides revised η-factors derived from CMOD records applicable to estimate the J-integral and CTOD in SE(B) specimens with varying crack size and specimen configuration. Non-linear finite element analyses for plane-strain and 3-D models provide the evolution of load with increased CMOD which is required for the estimation procedure. The analysis matrix considers SE(B) specimens with W = 2B and W = B configurations with and without side grooves covering a wide range of specimen thickness, including precracked Charpy (PCVN) specimens. Overall, the present results provide further validation of the J and CTOD evaluation procedure currently adopted by ASTM 1820 while, at the same time, giving improved estimation equations for J incorporating 3-D effects which enter directly into more accurate testing protocols for experimental measurements of fracture toughness values using 3P SE(B) specimens.

Effects of Weld Strength Mismatch on Estimation Procedures for J Fracture Parameter Using Clamped SE(T) Specimens

2009 ◽  
Author(s):  
Gustavo H. B. Donato ◽  
Rodrigo Magnabosco ◽  
Claudio Ruggieri
Keyword(s):  
Mouth Opening ◽  
Primary Objective ◽  
The Body ◽  
Weld Strength ◽  
Crack Mouth Opening Displacement ◽  
Fracture Parameter ◽  
Opening Displacement ◽  
Fracture Parameters ◽  
Wide Range ◽  
Estimation Procedures

This work presents an exploratory development of J estimation procedures for deep and shallow cracked tension SE(T) specimens based upon plastic eta factors which incorporate the effects of weld strength mismatch. The considered technique includes estimation of J from plastic work. The primary objective is to derive estimation procedures which are applicable to determine J fracture parameters for a wide range of a/W-ratios, material flow properties and different levels of weld strength mismatch using clamped SE(T) specimens of varying geometries. 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, which are needed to determine the estimation procedures. Laboratory testing of a welded structural steel using SE(T) specimens provide the data needed to evaluate J evolution for the welded joints based upon the proposed methodology. The crack driving force evolution is compared against the results obtained using plastic eta factors for homogeneous specimens and demonstrates the importance of considering mismatch effects on crack-tip stress fields and fracture parameters. The present analyses, when taken together with previous studies, extend the body of results which serve to determine J integral using tension SE(T) specimens with varying geometries and mismatch levels.

Sign in / Sign up

Export Citation Format

Share Document