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Leak-before-break (LBB) behavior was evaluated for two series of API 5L X65 line pipes and three series of X80 line pipes with various levels of Charpy V-notch (CVN) absorbed energy. Full-scale hydrostatic burst tests were conducted for the line pipes with an axial through-wall (TW) notch to determine LBB criteria, that is, the relationship between the axial TW notch length and hoop stress for LBB. The determined LBB criteria were verified by full-scale partial gas burst tests for line pipes with an axial part-through-wall (PTW) notch and were then compared to the estimation using the CVN energy-based equation that Kiefner et al. have proposed. The present study demonstrated that the estimation using the CVN-based equation was in good agreement with the experimental results for the pipes with a relatively low CVN energy of less than 130 J. On the contrary, the equation was not applicable to the pipes with a relatively high CVN energy of more than 130 J. The results of instrumented Charpy tests clarified that the load versus load-point displacement curves for Charpy specimens from the high CVN energy pipes were different from those from the low CVN energy pipes. Therefore, the applicability of the CVN-based equation was dependent on the load versus load-point displacement curve for a Charpy specimen.

A method of predicting the leak/rupture criteria for API 5L X80 and X100 line pipes was evaluated based on the results of hydrostatic full-scale tests for X60, X65, X80, and X100 line pipes with an axially through-wall (TW) notch. The TW notch test results defined the leak/rupture criteria, that is, the relationship between the initial notch lengths and the maximum hoop stresses during the TW notch tests. The defined leak/rupture criteria were then compared to the prediction of the Charpy V-notch (CVN) absorbed energy-based equation, which has been proposed by Kiefner, Maxey et al. This comparison revealed that the CVN-based equation was not applicable to the pipes having both a CVN energy greater than 120 or 130 J and flow stress greater than the level of X65. In order to predict the leak/rupture criteria for these line pipes, the static absorbed energy for ductile cracking, (Cvs)i, was introduced as representing the fracture toughness of a pipe material. The (Cvs)i value was determined from the microscopic observation of the cut and polished Charpy V-notch specimens after static three-point bending tests. The CVN energy in the original CVN-based equation was replaced by an equivalent CVN energy, (Cv)eq, which was defined as follows: (Cv)eq=4.5(Cvs)i. The leak/rupture criteria for the X80 and X100 line pipes with higher CVN energies were reasonably predicted by the modified equation using the (Cvs)i value.

Capacitance properties of activated Ketjenblack as an electrode active-material for an electric double layer capacitor 白石壮志 a) , * ，川口 忍 a) ，島袋 出 a) ，畠山義清 a) Soshi Shiraishi a), * , Shinobu Kawaguchi a) , Izuru Shimabukuro a) and Yoshikiyo Hatakeyama a) Ketjenblack (KB), which is a mesoporous carbon black, can be used as electrode active material for an electric double layer capacitor (EDLC). This paper addresses the capacitance properties of the activated KB with a high specific surface area as the electrode active material. The mesopore volume in KB was decreased by KOH-activation, while the micropores were developed to increase the specific surface area. As a result, the KOH-activated KB showed a higher volumetric capacitance as an EDLC electrode compared with the pristine KB. Additionally, it was also shown that the nitrogen-doping of the KOH-activated KB by nitrogen-monoxide produces a better volumetric capacitance and an ability to tolerate high voltages compared to the pristine KB electrode.

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