Brittle Crack Arrestability and Inverse Fracture in DWTT

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Takahiro Sakimoto ◽  
Toshihiko Amano ◽  
Takashi Hiraide ◽  
Tetsuya Tagawa ◽  
Satoshi Igi ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Test Temperature ◽  
Crack Arrest ◽  
Ductile Crack ◽  
Brittle Crack ◽  
Burst Test ◽  
Shear Area ◽  
Linepipe Steels ◽  
Temperature Test ◽  
Test Stress

Abstract The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle crack propagation, and the shear area fraction SA% in the DWTT has been adopted in the requirement for the linepipe steels. However, recent studies have pointed out the issue of ambiguity in evaluation of the DWTT when a ductile crack initiates from the notch and then transits to a brittle crack during ductile crack propagation. This fracture behavior is termed “inverse fracture.” According to the API Recommended Practice 5L3 (API RP 5L3), a test is considered invalid when a DWTT specimen shows inverse fracture. In this case, it is difficult to examine the acceptance criterion (85% shear area transition temperature) for linepipe steels. Because the purpose of the DWTT is to evaluate the brittle crack arrestability of the steels in a pressurized linepipe, the DWTT results should be examined with a propagating brittle crack arrest test. A large-scale brittle crack arrest test called the West Jefferson test is generally conducted to reproduce the crack propagation and arrest behavior in actual linepipes. However, it is somewhat difficult to control the lower test temperature and to initiate brittle crack in recent high-toughness steels in this burst test. Although the test stress conditions of the uniaxial tension in the plate tension brittle crack arrest test and the biaxial tension in a pressurized pipe are different, the plate tension brittle crack arrest test has the advantages of accurate control of the test temperature, test stress, and brittle crack initiation in comparison with the actual pipe burst test. Therefore, in this study, the brittle crack arrestability of linepipe steel which showed inverse fracture in the DWTT was investigated by conducting plate tension brittle crack arrest tests under an isothermal condition (crack arrest temperature test (CAT test)), which simulates the condition of the actual pipelines in service. This study also investigated the local shear lip thickness fraction in the CAT tests together with the shear area fraction SA% measured in DWTTs. Based on the results, the effect of brittle crack arrestability on inverse fracture appearance in the DWTTs was discussed in comparison with the brittle crack arrest behavior in the CAT tests.

Effect of Notch Type in Drop-Weight Tear Test Specimen on Crack Propagation and Arrest Behavior

2018 ◽  
Author(s):  
Satoshi Igi ◽  
Toshihiko Amano ◽  
Takahiro Sakimoto ◽  
Yasuhiro Shinohara ◽  
Tetsuya Tagawa
Keyword(s):  
Crack Propagation ◽  
Large Scale ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Chevron Notch ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Shear Area ◽  
The Impact ◽  
Crack Propagation And Arrest

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle fracture propagation. However, in the recent years there is an ambiguity in its evaluation if inverse fracture appears on the specimen fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer and existing tiny split have been discussed as a possible cause. In this paper, machined notch in brittle weld DWTT for X65 was performed and compared with various notch types of DWTTs such as conventional DWTT specimen with a pressed notch (PN), a chevron notch (CN) and a static pre-cracked (SPC). The fracture appearances were compared with different strength X65 - X80 grades linepipes and with different initial notch types. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen types, but there were no cases where the inverse fracture did not occurs. The purpose of DWTT is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. A large scale brittle crack arrest test, so called West Jeferson test is generally used to reproduce crack propagation and arrest behavior in an actual pipeline material. A middle scale test so called Crack Arrest Temperature (CAT) test was also proposed to check the shear area fraction measured in DWTT with API rating with that the local shear lip thickness fraction in those tests. CAT test can well reproduce crack propagation and arrest behavior under the condition of brittle crack initiation from the initial notch.

Simulation of Dynamic Crack Propagation and Arrest Using Various Types of Crack Arrestor

2016 ◽  
Author(s):  
Mohammed Uddin ◽  
Gery Wilkowski
Keyword(s):  
Crack Propagation ◽  
Large Diameter ◽  
Small Diameter ◽  
Full Scale ◽  
Fe Model ◽  
Ductile Crack ◽  
Burst Test ◽  
Ductile Crack Growth ◽  
Diameter Pipe ◽  
Linepipe Steels

In linepipe steels, there has been a growing interest in using damage mechanics that provides physical models of the fracture process which are embedded into a two- or three-dimensional finite element (FE) model. Among the various damage models, the cohesive zone model (CZM) has recently been used to simulate the ductile crack growth behavior in linepipe steels because of its computational efficiency and it requires only two parameters which can be determined in experiments. While CZM is not yet to be used as predictive tool, but it has a great application in crack arrestor design as well as in providing insight to ductile crack propagation. In this paper, the authors have demonstrated some practical applications of CZM in linepipe steels. The CZM was used to simulate the ductile crack propagation in full-scale pipes which was able to capture the global deformation as well as the experimental crack speed. The model was then used to determine the effect of anchor blocks at the end of the pipe in a large diameter full-scale burst test. Later, the model was used to simulate two small diameter pipe tests with steel crack arrestors to mimic two arrestor cases with one showing crack propagation and the other showing crack arrest. The CZM model was also applied to demonstrate the circumferential ring-off behavior of a small diameter pipe test with rigid crack arrestor. The arrestor model was then extended to simulate a large diameter full scale Mojave burst test with “soft crack arrestor (SCA)”. A single element FE model was developed to verify the SCA material which was later extended with stain-based failure criteria. Finally, ductile crack growth in full-scale pipe with SCA was demonstrated to show that the FE CZM model can be used to optimize the design of SCA.

Inverse Fracture in DWTT and Brittle Crack Behavior in Large-Scale Brittle Crack Arrest Test

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Tetsuya Tagawa ◽  
Toshihiko Amano ◽  
Takashi Hiraide ◽  
Takahiro Sakimoto ◽  
Satoshi Igi ◽  
...  
Keyword(s):  
Large Scale ◽  
Crack Arrest ◽  
Brittle Crack ◽  
Specimen Type ◽  
Chevron Notch ◽  
Drop Weight Tear Test ◽  
Shear Lip ◽  
Local Shear ◽  
Shear Area ◽  
Linepipe Steels

The drop weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle fracture propagation. Although there is an ambiguity in the evaluation of DWTT results if inverse fracture appears on the fracture surfaces, the cause of inverse fracture is not yet fully understood. In the present work, DWTTs were performed with X65, X70, and X80 steel linepipes. In addition to the conventional DWTT specimen with a pressed notch (PN), PN specimens with a back slot (BS) and specimens with a chevron notch (CN) or static precrack (SPC) were also examined, and the fracture appearances in different strengths and different initial notch types were compared. Although the frequency of inverse fracture in these DWTTs was different with each material and each specimen type, there was no material or specimen type that was entirely free from inverse fracture. The purpose of the DWTT is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. Therefore, the DWTT results should be examined with a running brittle crack arrest (BCA) test. A large-scale BCA test with temperature gradient was also performed with the X65 mother plate, and the shear area fraction measured in the DWTT fracture surface was compared with the local shear lip thickness fraction in the BCA test. Based on the results, the count of inverse fracture in the DWTT was discussed in comparison with the long BCA behavior in the BCA test.

Dynamic Ductile Tearing in High Strength Pipeline Steels

1996 ◽  
Author(s):  
F. Rivalin ◽  
A. Pineau
Keyword(s):  
Crack Propagation ◽  
High Strength Steels ◽  
High Strength ◽  
Pearlitic Steel ◽  
Crack Arrest ◽  
Full Scale ◽  
Ductile Crack ◽  
Safety Level ◽  
Dynamic Conditions ◽  
Pipe Burst

The study of rapid ductile crack propagation and crack arrest is a central point if one wants to reach a higher safety level in pipelines. Correlations between Charpy tests and full scale burst tests proved to be unsuccessful in predicting pipe burst for recent high strength steels. This paper presents an experiment which allows to test large SENT specimens under dynamic loading, and to characterize steel resistance against rapid ductile crack propagation by a classical energetic parameter, called the crack propagation energy, R, proposed by Turner. The R parameter proved to be characteristic of the rapid crack propagation in the material, for a given specimen and loading configuration. Failure of the specimen under dynamic conditions occurs by shearing fracture which is the same as in a full scale burst test. An example is given for an X65 ferritic-pearlitic steel loaded under static and dynamic conditions. A fracture mode transition is shown following the loading rate. From a metallurgical point of view, shearing fracture occurs by nucleation, growth and coalescence of voids, as for classical ductile fracture.

Brittle Crack Propagation/Arrest Behavior in T-Joint Structure of Heavy Gauge Steel Plates

2012 ◽  
Vol 706-709 ◽  
pp. 914-919 ◽  
Author(s):  
Tsunehisa Handa ◽  
Kimihiro Nishimura ◽  
Hiroshi Shiomi ◽  
Seishi Tsuyama
Keyword(s):  
Crack Propagation ◽  
Steel Plate ◽  
Crack Arrest ◽  
Steel Plates ◽  
Brittle Crack ◽  
K Value ◽  
Joint Structure ◽  
Large Heat ◽  
Large Container ◽  
Arrest Toughness

Brittle crack arrestability is extremely important in welded joints of heavy gauge steel plates used in large container ships. Recently, much attention has been focused on potential crack propagation along welds using large heat input. This paper examines the application of a T-joint to the strength deck structure of container ships to enhance crack arrestability. The crack arrest toughness, Kca, for crack arrest was varied. The ESSO test of T-joint components showed that brittle crack was arrested at the T-joint if the steel plate used for the flange had a high Kca value in the range from 4900 to 7300N/mm3/2. FE-analysis of the stress intensity factor K indicated that brittle crack propagation was arrested under the condition that the K-value at the running crack tip was less than the Kca of the material. In the T-joint, it was noted that the K-value around the area of the deepest point of the crack decreased and was finally less than the Kca of the flange plate when the brittle crack penetrated suddenly into the flange plate to a 10mm depth. This phenomenon shows the advantage of using a T-joint for brittle crack arrest in the flange plates of strength deck structures.

Experimental Measurement of CTOA During Ductile Crack Propagation in Pipeline Burst Tests

2018 ◽  
Author(s):  
Kazuki Shibanuma ◽  
Hikaru Yamaguchi ◽  
Takahiro Hosoe ◽  
Katsuyuki Suzuki ◽  
Shuji Aihara
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Crack Velocity ◽  
High Speed ◽  
Crack Arrest ◽  
Opening Angle ◽  
Small Scale ◽  
Outer Diameter ◽  
Burst Test ◽  
Pipe Burst

Dynamic measurement of drop-weight tear test (DWTT) and pipe burst test for 356 mm outer diameter and 9.5 mm wall thickness steel pipe were conducted using high-speed camera. Crack velocity in the DWTT were 10 m/s during the steady state. Crack Tip Opening Angle (CTOA) values measured in the DWTT showed the constant value of about 20.1° during steady state propagation. On the other hand, crack velocity in the burst test showed monotonically decreasing during crack propagation from 200 m/s but it was found that CTOA value kept constant value of about 13.2° until crack arrest irrespective of the crack velocity. These results showed the validation of the CTOA criterion for the high-pressure gas pipelines. The results also showed that CTOA in a burst test is generally different from that in a test using small-scale specimen. Future developments of the experimental procedure using a small-scale specimen to provide CTOA value corresponding with that in a burst test would be effective.

Experimental Study on Inverse Fracture in Drop-Weight Tear Test and Other Laboratory Test: Current Activities in HLP Committee, Japan, Report 2

2016 ◽  
Author(s):  
Tetsuya Tagawa ◽  
Taishi Fujishiro ◽  
Toshihiko Amano ◽  
Shuji Aihara ◽  
Satoshi Igi
Keyword(s):  
High Speed ◽  
Crack Arrest ◽  
Image Correlation ◽  
Correlation Technique ◽  
Brittle Crack ◽  
Fracture Surfaces ◽  
Drop Weight ◽  
Drop Weight Tear Test ◽  
Shear Area ◽  
The Impact

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against long brittle fracture propagation. However, there is an ambiguity in its evaluation if the inverse fracture appears (100% shear area prior to cleavage fracture from the notch) on the DWTT fracture surfaces. Although cause of the inverse fracture is not fully understood, compressive pre-straining near the impact hammer has been discussed as a possible cause. In the present work, DWTTs for X65, X70 and X80 were performed. In addition to conventional DWTT specimen with a pressed notch (PN), PN specimen with a back slot and specimens with a chevron notch (CN) or a static pre-cracked (SPC) were examined. The fracture appearances were compared in the different strength and in the different initial notch type. The frequency of the inverse fracture appeared in these DWTTs were different in each material and each specimen type, but there were no cases free from the inverse fracture. The inverse fracture was investigated by fractography and the hardness profiles along the under layer of the fracture surfaces. Also, the strain histories during impact in DWTTs were measured by the digital image correlation technique based on the high-speed camera images. The DWTT specimen purpose is to evaluate the brittle crack arrestability of the material in a pressurized linepipe. The DWTT results should be examined with a manner of a running brittle crack in a pressurized linepipe. A large scale brittle crack arrest test, so called temperature gradient ESSO test was also performed for X65 mother plate. The shear area fraction measured in DWTT fracture appearance was compared with the local shear lip thickness fraction in ESSO test. The count of the inverse fracture was discussed in comparison with the long brittle crack arrest behavior in ESSO test.

Structural Brittle Crack Arrest Design for Ultra Large Container Ship

2012 ◽  
Vol 81 (6) ◽  
pp. 485-488
Author(s):  
Masanobu TOYODA ◽  
Tsunehisa HANDA
Keyword(s):  
Crack Arrest ◽  
Container Ship ◽  
Brittle Crack ◽  
Large Container

Design of crack arrestors for ultra high grade gas transmission pipelines: simulation of crack initiation, propagation and arrest

2011 ◽  
Vol 2 (2) ◽  
pp. 307-319
Author(s):  
F. Van den Abeele ◽  
M. Di Biagio ◽  
L. Amlung
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Large Scale ◽  
Large Diameter ◽  
Pipe Material ◽  
High Grade ◽  
Gas Pipelines ◽  
Ductile Crack ◽  
Reinforced Plastics ◽  
Four Point Bending

One of the major challenges in the design of ultra high grade (X100) gas pipelines is the identification of areliable crack propagation strategy. Recent research results have shown that the newly developed highstrength and large diameter gas pipelines, when operated at severe conditions, may not be able to arrest arunning ductile crack through pipe material properties. Hence, the use of crack arrestors is required in thedesign of safe and reliable pipeline systems.A conventional crack arrestor can be a high toughness pipe insert, or a local joint with higher wall thickness.According to experimental results of full-scale burst tests, composite crack arrestors are one of the mostpromising technologies. Such crack arrestors are made of fibre reinforced plastics which provide the pipewith an additional hoop constraint. In this paper, numerical tools to simulate crack initiation, propagationand arrest in composite crack arrestors are introduced.First, the in-use behaviour of composite crack arrestors is evaluated by means of large scale tensile testsand four point bending experiments. The ability of different stress based orthotropic failure measures topredict the onset of material degradation is compared. Then, computational fracture mechanics is applied tosimulate ductile crack propagation in high pressure gas pipelines, and the corresponding crack growth inthe composite arrestor. The combination of numerical simulation and experimental research allows derivingdesign guidelines for composite crack arrestors.

Effect of toughness distribution in the thickness direction on long brittle crack propagation/arrest behaviour of heavy gauge shipbuilding steel

2018 ◽  
Vol 32 (7) ◽  
pp. 460-468 ◽  
Author(s):  
Tsunehisa Handa ◽  
Satoshi Igi ◽  
Kenji Oi ◽  
Kimihiro Nishimura ◽  
Hisakazu Tajika ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Thickness Direction ◽  
Brittle Crack ◽  
Shipbuilding Steel
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