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Journal of Pressure Vessel Technology-transactions of The Asme | 2015

Application of Weibull Stress Criterion to Brittle Fracture Assessment of Heat-Affected Zone-Notched Welds With Residual Stress

Yusuke Seko; Yasuhito Imai; Masaki Mitsuya; Noritake Oguchi; Fumiyoshi Minami

A constraint loss correction procedure using the Weibull stress criterion is specified in ISO 27306. However, this standard is applicable only to structural steel components with defects, not to welded joints. Therefore, we propose a method for estimating the brittle fracture limit of a weld with a notch in the heat-affected zone (HAZ) and residual stress based on the Weibull stress criterion. Three-point bending (3PB) tests and wide-plate (WP) tension tests of HAZ-notched welds made of 780-MPa class high-strength steel were conducted at −40 °C. The minimum critical crack tip opening displacement (CTOD) of the WP specimen fracturing at the coarse-grained region of the HAZ (CGHAZ) was approximately four times that of the 3PB specimen. Then, the effects of specimen geometry, residual stress, crack-front shape, and HAZ microstructure classification on the Weibull stress were investigated by using a finite element analysis (FEA). The results of these analyses showed that the specimen geometry, the welding residual stress, and HAZ microstructure affect the Weibull stress of HAZ-notched welds as crack driving force. Based on above results, the CTOD–Weibull stress curves for 3PB and WP specimens fracturing at CGHAZ were calculated by using an FEA. It was confirmed that the brittle fracture limit of an HAZ-notched weld with residual stress could be predicted from the Weibull stress criterion because predicted critical CTOD of WP specimens obtained by Weibull stress included experimental critical CTOD of WP specimens.


Volume 3: Materials and Joining; Risk and Reliability | 2014

Application of Weibull Stress Criterion to Brittle Fracture Assessment of HAZ-Notched Welds With Residual Stress

Yusuke Seko; Yasuhito Imai; Masaki Mitsuya; Noritake Oguchi; Fumiyoshi Minami

This paper presents a method for estimating the brittle fracture limit of a weld with a notch in the heat-affected zone (HAZ) and residual stress based on the Weibull stress criterion. A constraint loss correction procedure using the Weibull stress criterion is specified in ISO 27306. However, this standard is applicable only to structural steel components with defects, not to welded joints. Therefore, we conducted fracture tests and finite element analyses to propose a new evaluation method for welded structural components.In this study, three-point bending (3PB) tests and wide-plate (WP) tension tests of HAZ-notched welds made of 780-MPa-class high-strength steel were conducted at −40°C. Brittle fractures occurred in the HAZ regions of all the specimens, and the critical crack tip opening displacement (CTOD) values obtained in the 3PB and WP tests were approximately 0.02–0.07 mm and 0.08–0.11 mm, respectively. The minimum critical CTOD of the WP specimen fracturing at the coarse-grained region of the HAZ (CGHAZ) was approximately four times that of the 3PB specimen. These results confirmed that the difference of specimen geometry affects the brittle fracture resistance of a HAZ-notched weld with residual stress. Hence, the assessment of the brittle fracture limit of a welded structural component with a defect obtained by the fracture toughness of a 3PB specimen would be excessively conservative.The effects of specimen geometry, residual stress, crack-front shape and HAZ microstructure classification on the Weibull stress were investigated to clarify the difference of experimental critical CTOD for 3PB and WP by using a finite element analysis. The results of this analysis showed that the Weibull stress of WP specimen was larger than one of 3PB specimen in all CTOD region due to difference of geometry. The welding residual stress increased the Weibull stress only for WP. Compressive residual stress and crack front shape for 3PB specimen did not affect the Weibull stress. The difference of HAZ microstructure distribution for same welded joint affects the Weibull stress for 3PB and WP specimens.Finally, it was confirmed that the brittle fracture limit of a HAZ-notched weld with residual stress could be predicted from the Weibull stress criterion because critical CTOD of WP specimens predicted by critical CTOD of 3PB specimens fracturing at the CGHAZ included critical CTOD of WP specimens obtained by experiments.Copyright


Volume 1: Risk Assessment and Management; Emerging Issues and Innovative Projects; Operations and Maintenance; Corrosion and Integrity Management | 1998

Fatigue Behavior of Line Pipes Subjected to Severe Mechanical Damage

Naoto Hagiwara; Noritake Oguchi

Fatigue tests were carried out on ERW line pipes 200 mm and 300 mm in diameter with a severe gouge in dent type defect. Hoop stress fluctuation between 15% and 30% of the yield stress of the pipe materials was applied by cyclic internal pressure loading. By the parameter Q, a function of defect size and fracture toughness, fatigue behavior could have been well explained. Fatigue behavior differed above and below the threshold Q (Qth. When Q<Qth, crack propagation was initially associated with ductile crack growth, and therefore, fatigue life, Nf, decreased to less than 1000 cycles. On the contrary, Nf was larger than 1000 cycles when Q≧Qth. Nf was predictable with a power law equation incorporating dent depth, gouge depth, and stress amplitude when Q≧Qth. A gouge in a dent with Q<Qth, requires immediate repair or replacement.Copyright


Volume 3: Materials and Joining; Risk and Reliability | 2014

Development of In-Service Weld Repair Method for L555 (X80)-Grade Pipeline

Yoshiaki Yano; Noritake Oguchi; Makoto Katsuki; Toshiyuki Mayumi; Yasuhiro Ohtani

This paper deals with the development of the overlay weld repair method and the weld sleeve repair method applicable to L555 (X80) pipeline. Mechanical properties of the repaired pipes were investigated and finally proper welding materials and conditions were determined which could ensure hardness limit, required strength and toughness for in-service weld repair methods. Applicability of the in-service repair methods was validated and it was consequently confirmed that the weld repair methods will be able to apply to the repair of operating or pressurized pipeline ensuring the integrity of pipeline.Copyright


2012 9th International Pipeline Conference | 2012

The First L555 (X80) Pipeline in Japan

Yoshiyuki Matsuhiro; Noritake Oguchi; Toshio Kurumura; Masahiko Hamada; Nobuaki Takahashi; Atsuhi Shirahama

The construction of the first L555(X80) pipeline in Japan was completed in autumn, 2011.In this paper, the overview of the design consideration of the line, technical points for linepipe material and for girth welds are presented.In recent years the use of high strength linepipe has substantially reduced the cost of pipeline installation for the transportation of natural gas. The grades up to L555(X80) have been used worldwide and higher ones, L690(X100) and L830(X120), e.g., are being studied intensively. In the areas with possible ground movement, the active seismic regions, e.g., pipeline is designed to tolerate the anticipated deformation in longitudinal direction.In Japan, where seismic events including liquefaction are not infrequent, the codes for pipeline are generally for the grades up to L450(X65). Tokyo Gas Co. had extensively investigated technical issues for L555(X80) in the region described above and performed many experiments including full-scale burst test, full-scale bending test, FE analysis on the girth weld, etc., when the company concluded the said grade as applicable and decided project-specific requirements for linepipe material and for girth weld.Sumitomo Metals, in charge of pipe manufacturing, to fulfill these requirements, especially the requirement of round-house type stress-strain (S-S) curve to be maintained after being heated by coating operation, which is critical to avoid the concentration of longitudinal deformation, developed and applied specially designed chemical composition and optimized TMCP (Thermo-Machanical Control Process) and supplied linepipe (24″OD,14.5∼18.9mmWT) with sufficient quality. It had also developed and supplied induction bends needed with the same grade.Girth welds were conducted by Sumitomo Metal Pipeline and Piping, Ltd and mechanized GMAW (Gas Metal Arc Welding) was selected to achieve the special requirements, i.e., the strength of weld metal to completely overmatch the pipe avoiding the concentration of longitudinal strain to the girth weld, and the hardness to be max.300HV10 avoiding HSC (Hydrogen Stress Cracking) on this portion. Both of RT (Radiographic Test) and UT (Ultrasonic Test) were carried out to all the girth welds. These were by JIS (Japan Industrial Standards) and the project-specific requirements.Copyright


Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme | 2008

Effects of Local Metal Loss on Deformability of Line Pipes Subjected to Compressive Load

Yoshikazu Hashimoto; Naoto Hagiwara; Hiroshi Yatabe; Noritake Oguchi

In this paper, the deformability of line pipe with local metal loss was examined. A full-scale experiment and a finite element (FE) analysis were carried out for line pipe with local metal loss subjected to an axial compressive load. As a result, a good agreement was obtained between the analytical and experimental results. This indicated that the present analytical method was applicable to evaluate the deformability of line pipes with local metal loss subjected to a large ground movement. Parametric studies were then conducted to clarify the relationship between the geometry of the local metal loss and the deformability using the FE analytical method.


Volume 2: Integrity Management; Poster Session; Student Paper Competition | 2006

Critical Hardness for HSC in Deposit Welding on Steel Line Pipes Under Cathodic Protection

Noritake Oguchi; Jun’ichi Sakai; Hiroyuki Inoue; Shigeru Komukai

Repairing corrosion-damaged areas of operational steel line pipes by deposit welding performed without stopping the gas flowing inside is a common practice. However, this repair method tends to considerably increase the hardness of the weld metal and the HAZ, and it poses the risk of HSC under cathodic protection. In this study, the HSC susceptibility of the welding area was examined using welded full-scale C-ring specimens. The specimens were prepared from X42, X60, and X65 steel line pipes, whose outer diameter and longitudinal length were 610mm and 100 to 110mm, respectively, and whose nominal thickness was 10.3 to 15.1mm Deposit welding was applied to the middle of each specimen’s outer surface, and then a bolt through the specimen was tightened until the welded part was subjected to yield stress. The welded surface of the welding and its surrounding area were exposed to a test solution whose pH was adjusted to 7, and a cathodic current of 20mA/cm2 or 4mA/cm2 was applied for 500hours. Cracks appeared in the weld metals on the C-ring specimens to which a cathodic current of 20mA/cm2 had been applied. However, the propagation of the cracks ceased at the boundaries between the weld metal and the HAZ, and no cracks initiated in the HAZ. The maximum hardness of the HAZ was about 300 to 400Hv. These levels of hardness are far greater than 260Hv, which is the value obtained from experiments carried out using slow strain rate testing and is widely used in Japan as a criterion of hardness for avoiding HSC in the HAZ.Copyright


Volume 2: Design and Construction; Pipeline Automation and Measurement; Environmental Issues; Rotating Equipment Technology | 1998

Large Deformation Behavior of Pipe Bends Subjected to In-Plane Bending

Koji Yoshizaki; Hirokazu Ando; Noritake Oguchi

Ground liquefaction during earthquakes can produce a significant amount of lateral ground displacement. For buried gas pipelines, deformation and strain are likely to be concentrated on the pipe bends. Closing and opening in-plane bending experiments were conducted for various kinds of pipe bends until the measured strain exceeded 25% using pipe specimens of a diameter from 100 to 300 mm. The deformation behavior was different between the closing mode and the opening one. In the closing mode, an ovalization was observed in the central cross section of the bend, and internal pressure was maintained in all experiments. On the other hand, unique behavior was observed in the opening mode. When the pipe diameter was 300 mm (Do/t=43), local buckling was observed at the center of the bend. However, when Do/t was less than 32 (200 mm in diameter), the flexural rigidity of the bend became much higher than that of a straight pipe, and buckling and rupture were observed in the straight pipe. Finite element analyses were carried out using linear shell elements, and the validity of the numerical modeling technique over 25% of plastic strain was confirmed.Copyright


Jsme International Journal Series A-solid Mechanics and Material Engineering | 1999

Fatigue Behavior of Steel Pipes Containing Idealized Flaws under Fluctuating Pressure

Naoto Hagiwara; Yves Meziere; Noritake Oguchi; Mures Zarea; Rémy Champavère


Welding in The World | 2016

Brittle fracture assessment of embedded flaw in heat-affected zone based on Weibull stress criterion

Yusuke Seko; Yasuhito Imai; Masaki Mitsuya; Noritake Oguchi; Fumiyoshi Minami

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Hiroyuki Inoue

Osaka Prefecture University

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