Evaluation of J/CTOD for Clamped SE(T) Specimens With Welds

2011 ◽  
Author(s):  
Guowu Shen ◽  
William R. Tyson ◽  
James A. Gianetto ◽  
Dong-Yeob Park
Keyword(s):  
Yield Strength ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Homogeneous Material ◽  
J Integral ◽  
Center Line ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Integral Evaluation

In BS 7448, Part 2, the stress intensity factor, J-integral and crack tip opening displacement (CTOD) equations developed for evaluation of fracture toughness of a homogeneous material using experimentally measured quantities, such as load-load line displacement, are applied to SE(B) specimens with yield-strength-mismatched welds. The accuracy of this procedure was studied by Gordon and Wang using finite element analysis (FEA). Recently, the so-called “η factor” method for J-integral evaluation of SE(T) specimens with weld-center-line-cracked and yield-strength-mismatched welds was studied by Ruggieri using detailed FEA calculations and the load separation method proposed by Paris et al. For application to strain-based design of pipelines, CANMET has developed equations to evaluate J-integral and CTOD resistance curves for clamped SE(T) specimens of homogeneous materials using experimentally measured load and crack-mouth-opening displacement (CMOD) in a single-specimen procedure similar to that in ASTM E1820. In the present study, the accuracy of using these equations for J-integral evaluation of clamped SE(T) specimens with weld-center-line-cracked and strength-mismatched welds was studied. It was found that the errors in J and CTOD using the equations developed for SE(T) specimens of homogenous materials for these strength-mismatched welds are similar to those for SE(B) specimens with the same weld geometry and mismatch level as reported by Gordon and Wang. It was also found that using the higher of the strength of base and weld metals σY (= (σYS+σTS)/2), (i.e. (σY)w for overmatching and (σY)B for undermatching) in converting J to CTOD gives reasonable and conservative CTOD evaluations for specimens with weld-center-line-cracked and yield-strength-mismatched welds.

Effect of Side Grooves on Compliance, J-Integral and Constraint of a Clamped SE(T) Specimen

2010 ◽  
Author(s):  
Guowu Shen ◽  
William R. Tyson ◽  
James A. Gianetto ◽  
Dong-Yeob Park
Keyword(s):  
Plane Strain ◽  
Crack Depth ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
J Integral ◽  
Single Edge ◽  
Opening Displacement ◽  
Element Analysis ◽  
Crack Tip Constraint

The effect of side grooves on crack mouth opening displacement (CMOD) compliance, distribution of J-integral and crack-tip constraint parameters Q and A2 along the thickness of a clamped single-edge-notched tension (SE(T)) specimen were studied by finite element analysis (FEA). Focus was on the effect of depth of side grooves on J-integral and constraint parameters Q and A2 for shallow and deep cracks. The 3-D results were compared with those of SE(T) specimens in plane strain. The results show that the effective thickness equation used in ASTM E 1820 to evaluate compliance of side-grooved SE(B) and C(T) specimens can be used for clamped SE(T) specimens with reasonable accuracy. The results also suggest that the depth of the side grooves affects the distribution of the J-integral: the highest J-integral is at the center of the thickness for a SE(T) specimen with side grooves equal to or less than 10% of total thickness, and near the root of the side grooves for side grooves greater than 10% for a deeply-cracked specimen when the applied load P≥PY. The FEA results also show that the depth of side grooves affects the distribution of the constraint parameters: the crack-tip constraint is highest at the center of the thickness for a specimen with 0% side grooves (plain-sided), and near the root of the side grooves for side grooves equal to or greater than 10%. It was also found from FEA that the crack-tip constraint of a SE(T) specimen with 20% side grooves with shallow (a/W = 0.2) or deep (a/W = 0.5) crack is higher than that of a SE(T) specimen with the same crack depth in plane strain. As a result, the J-resistance of a SE(T) specimen with 20% side grooves may be lower than that of the same specimen in plane strain.

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.

Modeling and CMOD Mapping of Surface-Cracked Wide Plates

2008 ◽  
Author(s):  
Da-Ming Duan ◽  
Yong-Yi Wang ◽  
Yaoshan Chen ◽  
Joe Zhou
Keyword(s):  
Test Data ◽  
Driving Force ◽  
Mouth Opening ◽  
Quality Data ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Test Conditions

Curved wide plate (CWP) tests are frequently used to measure the tensile stress and strain capacity of pipeline girth welds. The parameters affecting the CWP measurement include specimen geometry and cooling setups. High-quality data is obtained when valid test conditions are confirmed. Crack mouth opening displacement (CMOD) is often measured in CWP tests. CMOD is a direct indicator of the amount of deformation at the cracked plane. It is an indirect indicator of the crack driving force (CDF) imparted on the crack. For a given test geometry and material, certain relationships can be derived between the measured CMOD and the more conventional representation of crack driving force, such as CTOD (crack tip opening displacement) and J-integral. Such relationships are a key element in fracture toughness testing standards. This kind of relationship is also particularly useful in strain-based design where CWP specimens are used for strain capacity and flaw growth prediction. In this paper finite element (FE) analysis is first used in modeling CWP testing conditions for X100 specimens with girth weld flaws to validate the test conditions. A novel approach called CMOD mapping is then developed to characterize the flaw behavior which, by making a direct use of CMOD test data from the CWP tests, is used to estimate the crack growth in the CWP. Finally analysis of strain limits using crack driving force (CDF) for the CWP specimens is also given by comparing experimental test data and FE estimation.

Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

Validation on the Relationship Between J Integral and CTOD for Offshore Structural Steel Weldments by Experimental and Numerical Analyses

2014 ◽  
Author(s):  
Dong Hyun Moon ◽  
Jeong Soo Lee ◽  
Jae Myung Lee ◽  
Myung Hyun Kim
Keyword(s):  
Plastic Deformation ◽  
Crack Tip ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Constraint Factor ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Plastic Constraint ◽  
The Relationship

Elastic plastic fracture mechanics (EPFM) is the domain of fracture analysis which considers extensive plastic deformation at crack tip prior to fracture. J integral and crack tip opening displacement (CTOD) have been commonly used as parameters for EPFM analysis. The relationship between these parameters has been extensively studied by industry and academia. The plastic constraint factor can serve as a parameter to characterize constraint effects in fracture involving plastic deformation. Therefore, the characteristics of plastic constraint factor are important in EPFM analysis. In this study, the relationship between J Integral and CTOD was investigated by conducting fracture toughness tests using single edge notched bend (SENB) specimens. Also, plastic constraint factor was investigated by using finite element analysis. Numerical analysis was carried out using ABAQUS elastic-plastic analysis mode.

Comparison of J-Integral Measurement Methods on Clamped Single-Edge Notched Tension Specimens

2016 ◽  
Author(s):  
Timothy S. Weeks ◽  
Jeffrey W. Sowards ◽  
Ross A. Rentz ◽  
David T. Read ◽  
Enrico Lucon
Keyword(s):  
Mouth Opening ◽  
Surface Strain ◽  
Image Correlation ◽  
Crack Mouth Opening Displacement ◽  
J Integral ◽  
Crack Mouth ◽  
Single Edge ◽  
Opening Displacement ◽  
Strain Gradients

This paper reports an extension of a previous study that compared methods of evaluating J by the crack mouth opening displacement and by surface strain gradients. Here, the surface strain gradients are measured by three-dimensional digital image correlation. The results herein represent a small test matrix that involved evaluation of the J-integral for clamped single-edge notched tensile specimens from API 5L X65 base-metal, weld metal and the adjacent heat affected zone; the J-integral was evaluated by a standardized procedure utilizing the crack mouth opening displacement (CMOD) and by the contour integral method on an external surface strain contour. Digital image correlation provides sufficient full-field strain data for use by this method and is considerably more robust than surface-mounted strain gage instrumentation. A series of validity checks are presented that demonstrate that the data are useful and valuable. Experimental determination of the J-integral is not limited to thoroughly analyzed test geometries and may be achieved with limited instrumentation. Furthermore, the method described does not require a determination of crack size nor any instrumentation that requires access to the crack mouth.

scholarly journals Material Assessment of Canadian SAW Line-Pipes

1998 ◽  
Author(s):  
D. K. Mak ◽  
W. R. Tyson
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Yield Strength ◽  
Notch Toughness ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Ductile Tearing ◽  
Average Grain Size ◽  
Grade One

Eight pipes, manufactured between 1952 and 1981, have been collected from various Canadian pipeline companies and tested. They include six pipes from the field made in the 1950’s and 1960’s of X52 grade, one experimental pipe manufactured in the early 1970’s of X65 grade, and a modern clean steel of X70 grade manufactured in 1981. The steels have been characterized by chemical composition, grain size, yield and tensile strengths, notch toughness (Charpy V-notch absorbed energy), and fracture toughness (J-integral and crack-tip opening displacement). The modern steel has much lower carbon content and much smaller grain size compared to the pipes manufactured in the 1950’s and 1960’s. The former is a fully-killed controlled-rolled steel while the latter are semi-killed ferrite-pearlite steels. All eight pipes have ferrite-pearlite microstructures, with the average grain size ranging from 4 to 14 μm. The transverse yield strength was found to be significantly higher (by about 20%) than the longitudinal yield strength. Notch toughness and fracture toughness were similar for pipes manufactured in the 1950’s and 1960’s. In comparison, the modern steel has much higher toughness and higher strength. J-integral and CTOD δ were found to be related by J = m σyδ with m = 1.8 and σy the transverse yield strength. The J-integral at 0.2 mm crack growth was consistent with a linear correlation with the upper-shelf Charpy energy. All the steels in this study fractured by ductile tearing in slow loading in spite of the low toughness of the older steels. It is suggested that, in the absence of Charpy upper shelf data, a reasonable representative toughness for resistance to axial surface flaws propagating by ductile tearing is J = 120±15 kJ/m2.

Direct Comparison of Single-Specimen Clamped SE(T) Test Methods on X100 Line Pipe Steel

2014 ◽  
Author(s):  
Timothy S. Weeks ◽  
Enrico Lucon
Keyword(s):  
Crack Growth ◽  
Mouth Opening ◽  
Closed Form Solution ◽  
Test Methods ◽  
J Integral ◽  
Single Specimen ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Line Pipe ◽  
Resistance Curves

The clamped single edge-notched tension (SE(T)) specimen has been widely used in a single-specimen testing scheme to generate fracture resistance curves for high strength line-pipe steels. The SE(T) specimen with appropriate notch geometry is a low-constraint specimen designed to reduce conservatism in the measurement of fracture toughness. The crack driving force is taken as either the J-integral or crack tip opening displacement (CTOD); it is generally accepted that the two parameters are interchangeable and equivalent using a simple closed form solution. However, the assumption that they are interchangeable, and to what extent, hasn’t been previously investigated experimentally on the same SE(T) specimen. This paper presents multiple test methods that were simultaneously employed on the same SE(T) specimens. The instrumentation includes: clip-gauges to measure surface crack mouth opening displacements (CMOD) and CTOD by the double-clip-gauge method; strain-gage arrays for direct J-integral measurements; and direct-current potential-drop (DCPD) instrumentation for supplementary crack size measurement. A direct comparison of ductile crack-growth resistance curves generated using J-integral and CTOD is presented here where each represents a different experimental and analytical approach. The two methods are in reasonable agreement over a narrow range of crack growth, differing slightly at initiation and diverging with increasing crack growth. Analysis of the supplementary instrumentation (i.e., strain gages, extensometers and DCPD) will be provided in a future publication.

Sign in / Sign up

Export Citation Format

Share Document