Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 ◽  
Author(s):  
Gery Wilkowski ◽  
David Rudland ◽  
Do-Jun Shim ◽  
David Horsley
Keyword(s):  
Transition Temperature ◽  
Surface Crack ◽  
Master Curve ◽  
Crack Depth ◽  
Temperature Shift ◽  
Transition Temperatures ◽  
Surface Cracks ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

When Old Line Pipes Initiates Fracture in a Ductile Manner

2006 ◽  
Author(s):  
G. Wilkowski ◽  
D. Rudland ◽  
D. Rider ◽  
P. Mincer ◽  
W. Sloterdijk
Keyword(s):  
Transition Temperature ◽  
Ductile Fracture ◽  
Static Loading ◽  
Crack Depth ◽  
Temperature Shift ◽  
Charpy Impact ◽  
Pipe Material ◽  
Line Pipe ◽  
Strain Rate Effects ◽  
Constraint Effects

This paper presents a procedure to determine the lowest temperature that a ductile fracture will initiate in old (or new) pipe that behaves in a brittle manner (by Charpy testing). Over the last decade, much work has been done to assess constraint effects on the crack-driving force for specimens and cracks in pipes. The material’s transition temperature where the fracture process changes from ductile tearing to cleavage fracture at crack initiation is affected by the constraint conditions, but is a material property that cannot be determined analytically. This paper presents a methodology to account for constraint effects to predict the lowest temperature where ductile fracture initiation occurs and relates that temperature back to Charpy impact data for X60 and lower grades, particularly for older vintage linepipe materials. The method involves a series of transition temperature shifts to account for thickness effects, strain-rate effects, and constraint effects to give a master curve of transition temperatures from Charpy data to through-wall-cracked or surface-cracked pipes (with various surface-crack depth values) under quasi-static loading. These transition temperature shifts were based on hundreds of pipe tests and thousands of specimen tests over several decades of work by numerous investigators. Conducting tests on 1927 and 1948 vintage line-pipe steels subsequently validated this method. In addition, data were developed on the 1927 vintage pipe material to assess the effect of the bluntness of a corrosion flaw on the lowest temperature where ductile fracture will still occur under quasi-static loading. An addition transition temperature shift occurs as a function of the bluntness of the flaw.

Application of Master Curve Method to Fracture Toughness Estimation of the Transport and Storage Cask Material

2008 ◽  
Author(s):  
Kiminobu Hojo ◽  
Kentaro Yoshimoto ◽  
Ryuichi Yamamoto ◽  
Toshihiro Matsuoka ◽  
Uwe Mayer
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Alloy Steel ◽  
Master Curve ◽  
Structural Integrity ◽  
Scale Model ◽  
Low Alloy Steel ◽  
Brittle To Ductile Transition ◽  
Data Scatter ◽  
And Storage

The transportation and storage casks have to be designed by considering transport and handling accidents. IAEA safety standard [1] requires drop test using a scale model and demonstration of structural integrity of the cask container vessel from the view point of leakage and instable fracture. For the fracture evaluation, it has to be verified that brittle fracture does not occur at the lowest temperature −40degC. MHI has developed the MSF-57BG cask whose body is made of forged low alloy steel LF3-m. It is well known that low alloy steel has the brittle-to-ductile transition temperature range of fracture toughness and large scatter of toughness value in this region. For the cask’s integrity evaluation, it is needed to obtain the fracture toughness dependent on temperature of this material by considering data scatter. The Master curve procedure [2] was proposed for estimation of fracture toughness of the pressure vessel on the basis of statistical procedure by using relatively small number of specimens. This paper examined the determination method of fracture toughness considering dynamic loading effect and data scatter in the brittle-to-ductile transition temperature by using the Master curve procedure.

Finite Element Analysis of Polyethylene Pipe Butt Fusion Joints with Circumferential Surface Cracks

2013 ◽  
Vol 785-786 ◽  
pp. 1151-1158
Author(s):  
Zhi Bin Zhu ◽  
Xiao Xiang Yang ◽  
Li Jing Chen ◽  
Nai Chang Lin ◽  
Zhi Tuo Wang ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Viscoelastic Material ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Element Analysis ◽  
Polyethylene Pipe

Based on the viscoelastic material property of polyethylene pipe, software ANSYS was used to simulate and analyze the mechanical property of polyethylene pipe butt fusion joints with circumferential surface crack defects. The viscoelastic material creep parameters were characterized as Prony series and 1/4 node singular element was selected for meshing along the boundaries of the crack, then the stress intensity factor of polyethylene pipe butt fusion joints with circumferential surface crack was calculated under the uniform internal pressure. Through the finite element simulation, the result showed that polyethylene pipe were most likely to fracture failure when crack initiated. Thus the viscoelasticity of materials can be ignored when analyzing the stress intensity factor of circumferential surface cracks of polyethylene pipe. the main influencing factor of the circumferential crack defects was the ratio of the crack depth to the thickness of polyethylene pipe.

Determination of Brittle-to-Ductile Transition Temperatures of Large-Diameter TMCP Linepipe Steel With High Charpy Energy by Use of Modified West Jefferson Testing

2016 ◽  
Author(s):  
Y. Hioe ◽  
G. Wilkowski ◽  
M. Fishman ◽  
M. Myers
Keyword(s):  
Transition Temperature ◽  
Brittle Fracture ◽  
Large Diameter ◽  
Pipe Steels ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Pipe Burst ◽  
Drop Weight Tear Test ◽  
Fracture Appearance ◽  
Shear Area

In this paper the results will be presented for burst tests from a Joint Industry Project (JIP) on “Validation of Drop Weight Tear Test (DWTT) Methods for Brittle Fracture Control in Modern Line-Pipe Steels by Burst Testing”. The JIP members for this project were: JFE Steel as founding member, ArcelorMittal, CNPC, Dillinger, NSSMC, POSCO, Tenaris, and Tokyo Gas. Two modified West Jefferson (partial gas) pipe burst tests were conducted to assess the brittle-to-ductile transition temperature and brittle fracture arrestability of two 48-inch diameter by 24.6-mm thick X65 TMCP line-pipe steels. These steels had very high Charpy energy (350J and 400J) which is typical of many modern line-pipe steels. In standard pressed-notch DWTT specimen tests, these materials exhibited abnormal fracture appearance (ductile fracture from the pressed notch prior to brittle fracture starting) that occurs with many high Charpy energy steels. Such behavior makes the transition temperature difficult to determine. The shear area values versus temperature results for these two burst tests compared to various modified DWTT specimens are shown. Different rating methodologies; DNV, API, and a Best-Estimate of steady-state fracture propagation appearance were evaluated.

scholarly journals Stress Analysis and Stress-Intensity Factors for Finite Geometry Solids Containing Rectangular Surface Cracks

1977 ◽  
Vol 44 (3) ◽  
pp. 442-448 ◽  
Author(s):  
J. P. Gyekenyesi ◽  
A. Mendelson
Keyword(s):  
Stress Intensity ◽  
Displacement Field ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Crack Opening ◽  
Crack Depth ◽  
Elastic Equilibrium ◽  
Finite Geometry ◽  
Surface Cracks ◽  
Intensity Factors

The line method of analysis is applied to the Navier-Cauchy equations of elastic equilibrium to calculate the displacement field in a finite geometry bar containing a variable depth rectangular surface crack under extensionally applied uniform loading. The application of this method to these equations leads to coupled sets of simultaneous ordinary differential equations whose solutions are obtained along sets of lines in a discretized region. Using the obtained displacement field, normal stresses, and the stress-intensity factor variation along the crack periphery are calculated for different crack depth to bar thickness ratios. Crack opening displacements and stress-intensity factors are also obtained for a through-thickness, center-cracked bar with variable thickness. The reported results show a considerable potential for using this method in calculating stress-intensity factors for commonly encountered surface crack geometries in finite solids.

Constraint Effects of Surface Crack Depth on Toughness: Experimental and Numerical Assessments

2019 ◽  
Author(s):  
G. Wilkowski ◽  
S. Kalyanam ◽  
Y. Hioe ◽  
F. W. Brust ◽  
S. Pothana ◽  
...  
Keyword(s):  
Surface Crack ◽  
Crack Depth ◽  
Limit Load ◽  
Initiation Toughness ◽  
Surface Cracks ◽  
Flat Plates ◽  
Depth Effect ◽  
Ductile Tearing ◽  
Wide Range ◽  
Axial Surface

Abstract Work published for the first time at the ASME PVP 2017 conference showed that when on the upper-shelf, the toughness measured directly from surface-cracked pipe tests decreased as the flaw depth increased. A similar trend existed in SENT tests. Initially it was found that this flaw depth sensitivity of the toughness occurred for a very tough material like TP304 stainless steel. The significance of that result was that even for a material where limit-load was thought to exist, as the flaw depth increased the toughness dropped appreciably, and the failure analysis mode changed from limit-load to elastic-plastic fracture. Experimentally, this made sense because it explained the observed phenomena of load-controlled leak-versus-break behavior for circumferential surface-cracked pipes (as will be shown for several pipe tests), but that LBB behavior is not predictable from circumferential flaw limit-load analysis. Furthermore, the flaw depth effect on toughness also exists for axial surface cracks and even in flat plates with surface cracks. For axial surface cracks the implication was that the long-used empirical surface-crack bulging factor from Maxey/Kiefner (incorporated in many international codes and standards) actually incorporated both the bulging factor and the toughness changes with flaw depth. Because of the change in toughness with flaw depth, when using detailed finite-element fracture analyses for the crack-driving force it is possible to have more error in the failure stress predictions if a constant toughness is assumed for all surface-flaw depths. In fact, in another paper in the ASME 2019 PVP conference it will be shown that the toughness in a wrought TP304 elbow at crack initiation of a circumferential surface crack that was 68% of the thickness was about 1/3rd of the toughness from a standard 1T CT specimen made from the same material. Those results will also be reviewed. Similar results of toughness decreasing with flaw depth in surface-cracked pipes and SENT specimens for various materials over a large range of strain-hardening behavior will show the toughness decrease trend with flaw depth is consistent. To understand these trends more theoretically, 3D FE analyses were also conducted for one initial set of TP304 SENT specimens with a wide range of a/w values (0.3 < a/w < 0.9). The initiation toughness decreased by a factor of 5 to 6 as the crack depth increased; however, the Q value coinciding to the load at the start of ductile tearing was constant for the wide range of a/W values. Q at the start of ductile tearing in the SENT (Qi) was more consistent at normalized distances from the crack tip, rσo/J that were in the range from 0.25 to 1.5 rather than just the popularly considered rσo/J = 2. Hence, by having one SENT test result with a single a/W value, the Ji value for any other a/W can then be calculated. This is consistent with the experimental trends to date, but unfortunately Ji was found to be not proportional to the Q values as is conventionally assumed by many researchers at this time.

Fracture Toughness Variation With Flaw Depth in Various Specimen Geometries and Role of Constraint in Material Fracture Resistance

2017 ◽  
Author(s):  
Y. Hioe ◽  
S. Kalyanam ◽  
G. Wilkowski ◽  
S. Pothana ◽  
J. Martin
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Crack Growth ◽  
Surface Crack ◽  
Crack Depth ◽  
Limit Load ◽  
Surface Cracks ◽  
Maximum Moment ◽  
Toughness Variation ◽  
Axial Surface

A series of pipe tests with circumferential surface cracks has been conducted along with fracture toughness tests using single-edge notch tension (SENT) specimens having similar crack depths and crack orientations as the surface-cracked pipes. This paper presents observation of measured fracture toughness variation due to the crack depth and discusses the effect of constraint on the material resistance to fracture. Crack-tip-opening displacement (CTOD) measurements were obtained with the use of a dual clip-gauge mounted on both the SENT specimens and center of the surface-cracks in the pipes. CTOD was obtained at both the crack initiation and during the crack growth through the ligament. CTOD is a direct measure of the material toughness in the pipe and SENT tests. CTOD at crack initiation and during crack growth can also be related to the material J-Resistance (J-R) curve. Commonly, the material resistance is assumed to be the same for all circumferential surface-crack geometries in a surface-cracked pipe fracture mechanics analyses. However, based on experimental observations on a series of recently conducted surface-cracked pipe tests, the CTOD at the center of the surface crack at the start of ductile tearing and maximum moment changed with the depth of the surface crack. This is believed to be a constraint effect on plasticity in the ligament which depends on crack depth. The CTOD values at crack initiation were decreasing linearly with crack depth. This linear decrease in CTOD trend with flaw depth was also observed in SENT tests. More importantly, the decrease in CTOD with surface crack depth was significant enough that the failure mode changed from being limit-load to elastic-plastic fracture even in relatively small-diameter TP304 stainless steel pipe tests. This toughness drop explains why the Net-Section-Collapse (limit-load) analysis overpredicted the maximum moment for some crack geometries, and why the deeper surface cracks tore through the pipe thickness at moments below that predicted by the NSC analysis for a through-wall crack of the same circumferential length. An “Apparent NSC Analysis” was developed in a companion paper to account for the changing toughness with crack depth [1]. Finally, this same trend in decreasing toughness with flaw depth is apparent in surface-cracked flat plates [2] and axial surface flaws in pipes [3]. The leak-before-break behavior for axial surface cracks is also not explained by numerical calculations of the crack-driving force when assuming the toughness is constant for all surface cracks and the through-wall cracks, but the change in toughness with surface flaw depth explains this behavior. Previously, axial flaw empirical limit-load solution was developed by Maxey and Kiefner [4], and is consistent with the observations from this paper.

Fatigue Crack Growth and Coalescence Algorithm Starting from Multiple Surface Cracks

2014 ◽  
Vol 891-892 ◽  
pp. 1003-1008 ◽  
Author(s):  
John Hock Lye Pang ◽  
You Xiang Chew
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Growth Data ◽  
Aspect Ratios ◽  
Weld Toe ◽  
Fatigue Crack Propagation Life

Fatigue crack growth and propagation analysis in welded joints have to deal with the complexity of modeling multiple weld toe surface cracks originating from weld toes. Fitness-For-Service (FFS) assessments for weld toe surface cracks employ a fracture mechanics and Paris Law approach to predict the fatigue crack propagation life of a semi-elliptical surface crack (SESC) to failure. A fatigue crack growth algorithm for assessing multiple surface crack growth, coalescence and propagation life was initially validated with previuously report crack growth data for a fillet shoulder specimen. Next a parametric study for single, double, and triple SESCs located along the weld toe line of a fillet weld was investigated with three starting crack depth sizes (0.1mm, 0.5mm, 1.0mm) coupled with three different crack aspect ratios (a/c = 1.0, a/c = 0.5 and 0.25) giving a total of 27 cases studied.

Phased array ultrasonic inspection of near-surface cracks in a railhead and its verification with rail slicing

2020 ◽  
Vol 62 (7) ◽  
pp. 387-395
Author(s):  
R Anandika ◽  
J Lundberg ◽  
C Stenström
Keyword(s):  
Surface Crack ◽  
Phased Array ◽  
Crack Depth ◽  
Ultrasonic Inspection ◽  
Accurate Estimation ◽  
Surface Cracks ◽  
Crack Network ◽  
Near Surface ◽  
3D Image Reconstruction ◽  
Crack Profile

In this study, near-surface cracks in a railhead are inspected thoroughly using phased array ultrasonic testing (PAUT). This research finds an alternative technique to inspect for near-surface cracks because the conventional non-destructive testing method for rail inspection lacks the capacity to inspect the near-surface crack profile. This study shows that PAUT can determine not only the crack depth but also the near-surface crack profile, so that the inspector can estimate the stage of crack growth and how the crack propagates. This information is valuable to the rail maintainer as one of the considerations for deciding the thickness of metal to remove when grinding the rail. In this study, after the measurement, the inspected region of the cracked railhead is sliced into thin pieces so that crack network information can be extracted. A 3D image reconstruction of the surface cracks based on the crack marks from all of the sliced rail pieces is performed. This image is then used as a reference to confirm the PAUT results. The results show that PAUT can clearly deliver crack profile estimation and provide an accurate estimation of a 3.51 mm crack-tip depth with an absolute error range of 8%-18%. The results also suggest that PAUT is a potential method for installation in a measurement train for near-surface crack inspection.

A Global Limit Load Solution for Plates With Semi-Elliptical Surface Cracks Under Combined Tension and Bending

2004 ◽  
Author(s):  
Yuebao Lei
Keyword(s):  
Finite Element ◽  
Surface Crack ◽  
Crack Depth ◽  
Limit Load ◽  
Elliptical Crack ◽  
Surface Cracks ◽  
Rectangular Crack ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
New Equation

A new global limit load solution is developed in this paper for a precise semi-elliptical surface crack in a plate under combined tension and bending, based on the net-section collapse principle. The new global limit load solution is compared with finite element (FE) results for the semi-elliptical crack, and with the global limit load solution for the circumscribing rectangular crack. The predictions of the new equation are conservative and close to the elastic-perfectly-plastic FE results for shallow cracks. For narrow plates with deep cracks, however, no FE results for the global limit load are available. The differences between the limit load solutions for a semi-elliptical crack and a rectangular crack are negligible for very wide plates but significant for narrow plates, depending on the normalised crack depth and the ratio between the crack length and width of the plate.

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