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Sunwoong Choi - One of the best experts on this subject based on the ideXlab platform.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 2. Criteria for onset of rapid Crack propagation
    Polymer Testing, 2017
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract The rapid Crack propagation behavior in pressurized plastic pipes was investigated to establish the criteria for onset of rapid Crack propagation in terms of the relationship between decompression wave speed and Crack Velocity. The study was performed by using an instrumented S4 test apparatus, the methodology for which is described in Part 1 of this paper. To establish the criteria for the onset of rapid Crack propagation in water-filled plastic pipes, PVC pipes of 440 mm outside diameter having dimensional ratios of 14, 18 and 25 were tested following the procedure described in ISO 13477. From the measurements made on decompression wave speed and Crack Velocity, it was determined that, for rapid Crack propagation to occur in the S4 test, two conditions were required. The decompression wave speed, Cw,S4, needs to be lower than the rapid Crack Velocity, a ˙ . Also, the Crack Velocity must be equal to or above the critical Crack Velocity, a ˙ c r i t . That is, C w , S 4 ≤ a ˙ a ˙ ≥ a ˙ crit It was shown that this critical Crack Velocity is always greater than the theoretical decompression wave speed in water filled pipes. Until now, the criterion for rapid Crack propagation in S4 was understood to only involve the former condition in water pipes. With this and the latter condition proposed, more complete criteria for rapid Crack propagation in water filled plastic pipes using the S4 method is now established.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 1. Experimental methods
    Polymer Testing, 2016
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract In a Small Scale Steady State (S4) test apparatus of ISO 13477, instrumentations were designed and successfully adapted to determine decompression wave speed and Crack Velocity during rapid Crack propagation event in water-filled plastic pipes. The basic design for decompression wave speed measurement involved the use of high-frequency dynamic pressure transmitters, located external to the water-filled pipe and connected to pressure measurement positions inside the pipe, by means of stainless steel tubes. For the Crack Velocity measurements, timing wire system with the required circuitry capable of giving the precise temporal indication of the propagating Crack was designed and employed. In this paper, detailed design of instrumentations adapted to the S4 test apparatus and the assessment techniques used to obtain decompression wave speed and Crack Velocity are described. It was also demonstrated that the methods developed were viable for these measurements which are known to affect the rapid Crack propagation behavior in water-filled plastic pipes.

Shuji Aihara - One of the best experts on this subject based on the ideXlab platform.

  • Crack tip opening angle during unstable ductile Crack propagation of a high pressure gas pipeline
    Engineering Fracture Mechanics, 2018
    Co-Authors: Kazuki Shibanuma, Takahiro Hosoe, Hikaru Yamaguchi, Masatoshi Tsukamoto, Katsuyuki Suzuki, Shuji Aihara
    Abstract:

    Abstract A full gas burst test was conducted to clarify the CTOA history during ductile Crack propagation in a high-pressure pipeline. The measurement results obtained by high-speed camera observation and image processing showed that the CTOA value remains constant during Crack propagation despite the large changes in the Crack Velocity. The numerical results of a series of finite element analyses supported the intrinsic implications of the experimental results. Consequently, the validity of the constant CTOA criterion, which has the potential to improve the accuracy and efficiency of numerical simulations of unstable ductile Crack propagation in a high-pressure pipeline, was verified.

  • calculation of dynamic stress intensity factors for pipes during Crack propagation by dynamic finite element analysis
    2012 9th International Pipeline Conference, 2012
    Co-Authors: Masaki Mitsuya, Hiroyuki Motohashi, Noritake Oguchi, Shuji Aihara
    Abstract:

    A dynamic finite element analysis method was proposed for calculating the dynamic stress intensity factors for pipes during Crack propagation. The proposed method can directly calculate the stress intensity factors without the simplification used in theoretical analyses, and it can consider the effects of the Crack Velocity and gas decompression. It was found that the stress intensity factors of long propagating Cracks in pipes saturated at a certain value in the case of a high Crack Velocity. However, although the stress intensity factors for pipes were in good agreement with those of band plates in the case of a high Crack Velocity, the stress intensity factors for pipes were different from those of band plates in the case of a low Crack Velocity. This result could be explained by the effect of bulging on the stress distribution around a Crack tip. The effect of bulging was more prominent for pipes with smaller diameters. In contrast, the dynamic stress intensity factors for band plates were in good agreement with the theoretical values that consider the dynamic effects and tended to decrease monotonically with increasing Crack Velocity. Additionally, the effects of gas decompression, caused by leakage from opened Cracks, on the stress intensity factors for pipes were investigated. An explanation of Crack deviation, which is observed in actual pipeline fractures, was provided by analyzing the ratio of the longitudinal stress to lateral stress.© 2012 ASME

  • A new model for dynamic Crack propagation and arrest in gas pipelines
    2010 8th International Pipeline Conference Volume 2, 2010
    Co-Authors: Kei Misawa, Yasuhito Imai, Shuji Aihara
    Abstract:

    A new model of unstable ductile Crack propagation and arrest of pressurized gas pipeline is presented. The model couples pipe deformation and fracture with gas decompression. The model also takes account of backfill effect. Pipe deformation and pressure changes are obtained by solving one-dimensional differential equations. Validity of the model was checked by comparing with published full-scale burst test data. The model can predict history of Crack Velocity and arrest Crack length with fairly good accuracy. The model can be applied to wide ranges of gases, pipe grades and pipe sizes because it does not rely on parameter adjustment by experimental data sets but is based on physical assumptions.Copyright © 2010 by ASME

Vipin Vijayan - One of the best experts on this subject based on the ideXlab platform.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 2. Criteria for onset of rapid Crack propagation
    Polymer Testing, 2017
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract The rapid Crack propagation behavior in pressurized plastic pipes was investigated to establish the criteria for onset of rapid Crack propagation in terms of the relationship between decompression wave speed and Crack Velocity. The study was performed by using an instrumented S4 test apparatus, the methodology for which is described in Part 1 of this paper. To establish the criteria for the onset of rapid Crack propagation in water-filled plastic pipes, PVC pipes of 440 mm outside diameter having dimensional ratios of 14, 18 and 25 were tested following the procedure described in ISO 13477. From the measurements made on decompression wave speed and Crack Velocity, it was determined that, for rapid Crack propagation to occur in the S4 test, two conditions were required. The decompression wave speed, Cw,S4, needs to be lower than the rapid Crack Velocity, a ˙ . Also, the Crack Velocity must be equal to or above the critical Crack Velocity, a ˙ c r i t . That is, C w , S 4 ≤ a ˙ a ˙ ≥ a ˙ crit It was shown that this critical Crack Velocity is always greater than the theoretical decompression wave speed in water filled pipes. Until now, the criterion for rapid Crack propagation in S4 was understood to only involve the former condition in water pipes. With this and the latter condition proposed, more complete criteria for rapid Crack propagation in water filled plastic pipes using the S4 method is now established.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 1. Experimental methods
    Polymer Testing, 2016
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract In a Small Scale Steady State (S4) test apparatus of ISO 13477, instrumentations were designed and successfully adapted to determine decompression wave speed and Crack Velocity during rapid Crack propagation event in water-filled plastic pipes. The basic design for decompression wave speed measurement involved the use of high-frequency dynamic pressure transmitters, located external to the water-filled pipe and connected to pressure measurement positions inside the pipe, by means of stainless steel tubes. For the Crack Velocity measurements, timing wire system with the required circuitry capable of giving the precise temporal indication of the propagating Crack was designed and employed. In this paper, detailed design of instrumentations adapted to the S4 test apparatus and the assessment techniques used to obtain decompression wave speed and Crack Velocity are described. It was also demonstrated that the methods developed were viable for these measurements which are known to affect the rapid Crack propagation behavior in water-filled plastic pipes.

Tom Marti - One of the best experts on this subject based on the ideXlab platform.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 2. Criteria for onset of rapid Crack propagation
    Polymer Testing, 2017
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract The rapid Crack propagation behavior in pressurized plastic pipes was investigated to establish the criteria for onset of rapid Crack propagation in terms of the relationship between decompression wave speed and Crack Velocity. The study was performed by using an instrumented S4 test apparatus, the methodology for which is described in Part 1 of this paper. To establish the criteria for the onset of rapid Crack propagation in water-filled plastic pipes, PVC pipes of 440 mm outside diameter having dimensional ratios of 14, 18 and 25 were tested following the procedure described in ISO 13477. From the measurements made on decompression wave speed and Crack Velocity, it was determined that, for rapid Crack propagation to occur in the S4 test, two conditions were required. The decompression wave speed, Cw,S4, needs to be lower than the rapid Crack Velocity, a ˙ . Also, the Crack Velocity must be equal to or above the critical Crack Velocity, a ˙ c r i t . That is, C w , S 4 ≤ a ˙ a ˙ ≥ a ˙ crit It was shown that this critical Crack Velocity is always greater than the theoretical decompression wave speed in water filled pipes. Until now, the criterion for rapid Crack propagation in S4 was understood to only involve the former condition in water pipes. With this and the latter condition proposed, more complete criteria for rapid Crack propagation in water filled plastic pipes using the S4 method is now established.

  • Decompression wave speed and Crack Velocity measurements during S4 test in water pressurized plastic pipes: Part 1. Experimental methods
    Polymer Testing, 2016
    Co-Authors: Vipin Vijayan, Tom Marti, Sunwoong Choi
    Abstract:

    Abstract In a Small Scale Steady State (S4) test apparatus of ISO 13477, instrumentations were designed and successfully adapted to determine decompression wave speed and Crack Velocity during rapid Crack propagation event in water-filled plastic pipes. The basic design for decompression wave speed measurement involved the use of high-frequency dynamic pressure transmitters, located external to the water-filled pipe and connected to pressure measurement positions inside the pipe, by means of stainless steel tubes. For the Crack Velocity measurements, timing wire system with the required circuitry capable of giving the precise temporal indication of the propagating Crack was designed and employed. In this paper, detailed design of instrumentations adapted to the S4 test apparatus and the assessment techniques used to obtain decompression wave speed and Crack Velocity are described. It was also demonstrated that the methods developed were viable for these measurements which are known to affect the rapid Crack propagation behavior in water-filled plastic pipes.

Ryouta Higuchi - One of the best experts on this subject based on the ideXlab platform.

  • fracture propagation and arrest in high pressure gas transmission pipeline by ultra high strength line pipes
    2008 7th International Pipeline Conference Volume 3, 2008
    Co-Authors: Hiroyuki Makino, Izumi Takeuchi, Ryouta Higuchi
    Abstract:

    The fracture arrest of high pressure gas pipelines is one of the keen subjects for application of high strength line pipes. To examine the arrestability of high strength line pipes against Crack propagation, several full scale fracture propagation tests have been conducted. The fracture propagation tests of X100 or X120 under high pressure revealed that the existing models of arrest energy prediction failed to predict the arrest energies. By careful investigations of the test results, it is found that the failure in prediction is mainly due to the uncertainty of Crack Velocity curve prediction. On the other hand, accuracy of predicted gas decompression curve is relatively high even in the case of high pressure condition. Experimentally, the arrest energies have been determined by full-scale fracture propagation tests with increasing toughness arrangement. Different from actual pipeline, extremely low toughness pipe has been employed in Crack initiation pipe with intention of getting steady state propagation. However, arrestability of pipe might be underestimated in the increasing toughness arrangement test as the initial Crack Velocity increases. Together with recalibrated Crack Velocity curve, Sumitomo model (HLP method with Sumitomo’s Crack Velocity curve) predicts that even toughness arrangement, which is the case of real pipelines, could arrest the propagating shear fracture in high pressure gas pipelines by X100.Copyright © 2008 by ASME