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.

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.

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.

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.

Evaluation for Abnormal Fracture Appearance in Drop Weight Tear Test With High Toughness Linepipe

2002 ◽  
Author(s):  
Ryuji Muaoka ◽  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
Joe Kondo
Keyword(s):  
Brittle Fracture ◽  
Fracture Surface ◽  
Full Scale ◽  
Area Fraction ◽  
Burst Test ◽  
High Toughness ◽  
Chevron Notch ◽  
Drop Weight Tear Test ◽  
Fracture Appearance ◽  
Shear Area

The West-Jefferson type full scale partial gas burst test was carried out in order to investigate appropriate evaluation method for resistance to brittle fracture propagation in high toughness linepipe materials that exhibits abnormal fracture appearance by the Drop Weight Tear Test (DWTT). Shear area fraction (SA%) of the DWTT that had been derived from the way regarding or disregarding the abnormal fracture appearance was compared with the shear area fraction obtained from the fracture surface by the full scale burst test. It was shown that SA% obtained by the burst tests corresponded well with that by the pressed notch DWTT for the cases of disregarding abnormal fracture appearance. On the other hand, SA% in the DWTT was lower than that in the burst test when the abnormal fracture appearance was treated in the same manner as the brittle fracture that occurs at the notch tip of the specimen. Therefore, it can be stated that the evaluation by regarding the abnormal fracture surface can be conservative and much relevant evaluation can be possible by disregarding the abnormal fracture appearance. SA% of the fracture surface in the Chevron notch DWTT showed slightly lower value than that in the burst test, regardless of whether abnormal fracture appearances was regarded or disregarded. This means the Chevron notch DWTT is also severe testing method, as well as the pressed notch DWTT with regarding the abnormal fracture surface.

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

scholarly journals Effect of Un-welded Length on Behavior of Brittle Crack Arrest in Tee joint structure

2008 ◽  
Vol 26 (2) ◽  
pp. 124-130 ◽  
Author(s):  
Tsunehisa HANDA ◽  
Shinichi SUZUKI ◽  
Noboru KIJI ◽  
Masanobu TOYODA ◽  
Takashi MIYATA
Keyword(s):  
Crack Arrest ◽  
Brittle Crack ◽  
Joint Structure

Effect of unwelded length on behaviour of brittle crack arrest in T-joint structure

2009 ◽  
Vol 23 (9) ◽  
pp. 640-647 ◽  
Author(s):  
Tsunehisa Handa ◽  
Shinichi Suzuki ◽  
Noboru Kiji ◽  
Masanobu Toyoda ◽  
Takashi Miyata
Keyword(s):  
Crack Arrest ◽  
Brittle Crack ◽  
Joint Structure

Simplified Evaluation of Brittle Crack Arrest Toughness in Heavy-thick Plate by Combined Small-scale Tests

2017 ◽  
Vol 27 (2) ◽  
pp. 210-215 ◽  
Author(s):  
Teppei Okawa ◽  
Hiroyuki Shirahata ◽  
Kiyotaka Nakashima ◽  
Kazuhisa Yanagita ◽  
Takehiro Inoue
Keyword(s):  
Thick Plate ◽  
Crack Arrest ◽  
Small Scale ◽  
Brittle Crack ◽  
Arrest Toughness
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