EVALUATION OF THE INTERNAL HYDROGEN-INDUCED THRESHOLD STRESS INTENSITY FACTOR IN 2.25CR-1MO STEELS DETERMINED BY THE OFFSET POTENTIAL DROP METHOD
Shinji Konosu, Takehiro Inoue and Yoshiaki Murakami
Proceedings of the ASME 2017 2017 ASME Pressure Vessels & Piping Division Conference
PVP2017/ 65505, 1-13
Threshold for Hydrogen-Induced Fracture in 2.25Cr-1Mo Steel Used for Long-Term Service
Hiroki Nakanishi, Wataru Fujiki, Hiroaki Ohtani and Shinji Konosu
Proceedings of the ASME 2016 Pressrure Vessels & Piping Division Conference PVP2016, July 17-21, 2016, Vancouver Canada
Tearing Resistance Properties of Cr-Mo Steels with Internal Hydrogen Determined by the Potential Drop Method
SHINJI KONOSU, HIDENORI SHIMAZU, and RYOHEI FUKUDA
METALLURGICAL AND MATERIALS TRANSACTIONS A
The tearing resistance, dJ/da, of conventional 2.25Cr-1Mo steels and a V-bearing steel(2.25Cr-1Mo-0.3V steel) with internal hydrogen was measured using the effective offset potential drop method. Internal hydrogen refers to test specimens that are precharged (thermally charged)prior to testing. In general, Cr-Mo steels, used widely in the refining and petrochemical industries, are susceptible to temper embrittlement. However, very few studies have dealt with the effects of hydrogen and temper embrittlement on the tearing resistance. Test specimens were prepared by subjecting them to normalizing, tempering, and post-weld heat treatments that simulated actual conditions. Some specimens were embrittled by step cooling. Hydrogen substantially reduced dJ/da for all samples except for that for the V-bearing steel, and temper embrittlement caused additional adverse effects on dJ/da for samples with internal hydrogen for which the temper embrittlement parameter, i.e., the J-factor, was large.
VALIDITY OF PROCEDURE FOR PLASTIC COLLAPSE ASSESSMENT OF A LOCAL THIN AREA NEAR VESSEL AND NOZZLE INTERSECTIONS SUBJECTED TO INTERNAL PRESSURE AND EXTERNAL LOADINGS
Kenji Oyamada, Shinji Konosu, Tetsuji Miyashita and Takashi Ohno
Proceedings of the ASME 2015 Pressure Vessels & Piping Conference PVP2015
There are numerous cases in which a volumetric flaw such as a local thin area (LTA) is found in pressure equipment such as vessels, piping, tanks, and so on. Sometimes it is found near vessel and nozzle intersection. A fitness for service (FFS) rule of such cases was desired, because plastic collapse assessment of LTA near vessel and nozzle intersection usually needed to conduct by numerical analysis such as FEA. Recently, an FFS assessment rule of plastic collapse assessment of LTA near vessel (run-pipe) and nozzle (branch pipe) intersection subjected to internal pressure and external loadings has been developed and proposed by one of authors of this paper. In this paper, the proposed plastic collapse assessment rule was verified with results of experiments and FEA for cylindrical vessels with an LTA near vessel and nozzle intersections subjected to internal pressure and external loadings.
Procedure for Plastic Collapse Assessment of a Local Thin Area near Vessel and Nozzle Intersections Subjected to Internal Pressure and External Loadings
Shinji Konosu, Kenta Ogasawara and Kenji Oyamada
Proceedings of the ASME 2015 Pressure Vessels & Piping Division Conference PVP2015
This paper develops a procedure for plastic collapse assessment of vessel (run pipe) - nozzle (branch pipe) intersections with an arbitrarily positioned local thin area (LTA) under different loading conditions, namely internal pressure, external moment on a nozzle applied along various directions with respect to the vessel main axis, and pure bending moment on a vessel. Although simplified procedures for plastic collapse assessment based on the p-M (internal pressure ratio and external bending moment ratio) diagram method have been previously proposed for straight cylindrical vessels and pipe bends with an LTA, very few studies have dealt with the determination of plastic collapse load for an LTA in the critical region of intersecting vessels subjected to internal pressure and external moment loading. This is likely due to the complexity of the stresses caused by the applied loads in the critical region, which arises from geometric discontinuities. In this paper, simple and empirical formulae for predicting conservative plastic collapse loads for an LTA in the critical region of the intersecting vessels are proposed based on the analytical results of stresses at defect-free vesselnozzle intersections by using linear finite element analysis (FEA). Localized elastic stress retardation factors are taken into account in the evaluation by the results of a non-linear FEA. Consequently, a p-M diagram method is developed for application to vessel-nozzle intersections with an LTA.
Procedure for Predicting Multiple Noaligned Fatigue Crack Life
Internationa Conference on Fracture and Strength, ICFS2010
Overview of on-going FFS rules in Japan for general industrial facilities(Invited lecture)
Eueopean Fitbess-for-Service Network, 8th Meeting
The American Society of Mechanical Engineers (ASME)