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Li Y.,Japan Atomic Energy Agency | Hasegawa K.,Japan Atomic Energy Agency | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

Piping lines in nuclear power plants may experience multiaxial loads including tensile force, bending and torsion moments during operation. There is a lack of guidance for failure evaluation under the multi-axial loads including torsion moment. ASME B&PV Code Section XI Working Group is currently developing fully plastic failure evaluation procedures for pressurized piping items containing local wall thinning subjected to multi-axial loads. A failure estimation method for locally wall thinned pipes subjected to multi-axial loads including torsion moment has been proposed through numerical analyses. In this study, in order to investigate the failure behavior of the pipes with local wall thinning subjected to multi-axial loads including the torsion, failure experiments were performed on 20 mm diameter carbon steel pipes with a local wall thinning. Based on the experimental results, the proposed failure estimation method is confirmed to be applicable to pipes with local wall thinning. Copyright © 2015 by ASME. Source


Li Y.,Japan Atomic Energy Agency | Hasegawa K.,Japan Atomic Energy Agency | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015

When a crack is detected in a piping line during in-service inspections, failure estimation method provided in ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. The failure estimation method in the current codes accounts for the bending moment and axial force due to pressure. The torsion moment is not considered. Recently, analytical investigations have been carried out by several authors on the limit load of cracked pipes considering multi-axial loads including torsion and two failure estimation methods for multi-axial loads including torsion moment with different ranges of values have been proposed. In this study, to investigate the failure behavior of cracked pipes subjected to multi-axial loads including the torsion moment and to provide experimental support for the failure estimation methods, failure experiments were performed on 20 mm diameter stainless steel pipes with a circumferential surface crack or a through-wall crack under combined axial force and bending and torsion moments. Based on the experimental results, the proposed failure estimation methods were confirmed to be applicable to cracked pipes subjected to multi-axial loads. Copyright © 2015 by ASME. Source


Li Y.,Japan Nuclear Energy Safety Organization | Hasegawa K.,Japan Nuclear Energy Safety Organization | Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co.
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2013

When a crack is detected in a stainless steel pipe during in-service inspections, the failure estimation method given in codes such as the ASME Boiler and Pressure Vessel Code Section XI or JSME Rules on Fitness-for-Service for Nuclear Power Plants can be applied to evaluate the structural integrity of the cracked pipe. In the current codes, the failure estimation method includes the bending moment and tensile force due to pressure. The torsion moment is assumed to be relatively small and is not considered. Recently, analytical investigations considering multiaxial loads including torsion were conducted in several previous studies by examining the limit load for pipes with a circumferential crack. A failure estimation method for the combined bending moment, torsion moment, and internal pressure was proposed. In this study, the failure behavior of pipes with a circumferential crack subjected to multiaxial loads including the torsion is investigated to provide experimental support for the failure estimation method. Experiments were carried out on small size stainless steel cylinders containing a circumferential surface or through-wall crack, subjected to the combined tensile load and torsion moment. Based on the experimental results, the proposed failure estimation method was confirmed to be applicable to cracked pipes subjected to combined tensile and torsion loads. Copyright © 2013 by ASME. Source


Miura N.,Japan Central Research Institute of Electric Power Industry | Hoshino K.,Electrical Power Engineering Systems Co. | Li Y.,Japan Nuclear Energy Safety Organization | Hasegawa K.,Japan Nuclear Energy Safety Organization
Journal of Pressure Vessel Technology, Transactions of the ASME | Year: 2014

When a crack-like-flaw is detected in piping during in-service inspection, the limit load criterion given in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the structural integrity of the piping. However, in-service piping is generally subjected to combined tensile, bending, and torsional loading, and a methodology to evaluate the limit moment for torsion has not yet been established because of inadequate experimental validation. In this study, fracture tests were conducted for circumferentially cracked cylinders subjected to torsional moment. The experimental maximum moments were compared with the limit moments, which were evaluated on the basis of the net-section-collapse criterion for torsional moment. The maximum moments can be conservatively predicted by the net-section-collapse criterion. Copyright © 2014 by ASME. Source


Seki S.,Japan Central Research Institute of Electric Power Industry | Ohno Y.,Japan Central Research Institute of Electric Power Industry | Ohno Y.,Electrical Power Engineering Systems Co. | Mita Y.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
ECS Electrochemistry Letters | Year: 2012

Relationships between the lithium salt concentration in a low-volatility solvent (room-temperature ionic liquid) and lithium secondary battery performance characteristics were investigated by using [LMOpositive electrode |DMPIm-TFSA+LiTFSA binary electrolyte | lithiummetal negative electrode] cells. Charge/discharge cycle and rate performance characteristics and various changes in resistance (lithium salt concentration and cycle number dependences) were examined, and the necessity of a suitable lithium salt concentration (0.32-0.64 mol kg?1) for good capacity retention and rate capability was concluded. © 2012 The Electrochemical Society. Source

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