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Ogawa, Fumio*; Nakayama, Yuta*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*
Transactions of the Indian National Academy of Engineering (Internet), 7(2), p.549 - 564, 2022/06
The strain energy-based life evaluation method of Mod. 9Cr-1Mo steel under non-proportional multiaxial creep-fatigue loading is proposed. Inelastic strain energy densities were calculated as the areas inside the hysteresis loops. The effect of mean-stress has been experimentally considered and the relationship between inelastic strain energy densities and creep-fatigue lives was investigated. It was found from the investigation of hysteresis loops, the decrease in maximum stress leads to prolonged failure life, while stress relaxation during strain holding causes strength reduction. The correction method of inelastic strain energy density was proposed considering the effect of maximum stress in hysteresis loop and minimum stress during strain holding, and strain energy densities for uniaxial and non-proportional multiaxial loading were obtained. Based on these results, the mechanisms governing creep-fatigue lives under non-proportional multiaxial loading have been discussed.
Nakayama, Yuta*; Ogawa, Fumio*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*
ISIJ International, 61(8), p.2299 - 2304, 2021/08
Times Cited Count：5 Percentile：27.67(Metallurgy & Metallurgical Engineering)This study discusses the creep-fatigue strength for Mod.9Cr-1Mo steel at a high temperature under multiaxial loading. A low-cycle fatigue tests in various strain waveforms were performed with a hollow cylindrical specimen. The low cycle fatigue test was conducted under a proportional loading with a fixed axial strain and a non-proportional loading with a 90-degree phase difference between axial and shear strains. The low cycle fatigue tests at different strain rates and the creep-fatigue tests at different holding times were also conducted to discuss the effects of stress relaxation and strain holding on the failure life. In this study, two types of multiaxial creep-fatigue life evaluation methods were proposed: the first method is to calculate the strain range using Manson's universal slope method with considering a non-proportional loading factor and creep damage; the second method is to calculate the fatigue damage by considering the non-proportional loading factor using the linear damage law and to calculate the creep damage from the improved ductility exhaustion law. The accuracy of the evaluation methods is much better than that of the methods used in the evaluation of actual machines such as time fraction rule.
Kanayama, Hideyuki*; Hiyoshi, Noritake*; Ogawa, Fumio*; Kawabata, Mie*; Ito, Takamoto*; Wakai, Takashi
Zairyo, 68(5), p.421 - 428, 2019/05
This study presents creep damage assessment method for Mod. 9Cr-1Mo steel by sampling creep testing with thin plate specimen. Tensile creep rupture tests were performed using three different sizes of specimen under two different test environments to verify the creep testing with the thin plate specimen. Time to rupture of Mod. 9Cr-1Mo steel using three different sizes were almost same. In addition, there was no effect of environment on time to rupture. Pre-damaged thin plate specimens were machined from a bulk specimen's gage section that pre-damage test was performed with. Pre-damage based on life fraction rule were 8%, 16% and 25%. No effect of the process of machining pre-damaged specimen on time to rupture was confirmed by verification tests in same test condition as pre-damage test. Stress acceleration creep rupture tests were performed to estimate creep damage assessment. Creep damage assessment by stress acceleration creep rupture tests was sufficiently accurate estimate. Creep damage assessments by Vickers hardness and lath width were compared with the assessment by stress acceleration creep rupture tests to study applicability of these methods.
Kanayama, Hideyuki; Hiyoshi, Noritake*; Ito, Takamoto*; Ogawa, Fumio*; Wakai, Takashi
Zairyo, 66(2), p.86 - 92, 2017/02
This study presents creep characteristics of Mod. 9Cr-1Mo steel with various sized specimens and environment. Creep tests were performed using three different sizes of specimen and three different type of testing environment. Specimens are a bulk specimen which has 6mm diameter and 30mm gage length, a miniature specimen which has 2mm diameter and 10mm gage length and a thin plate specimen which has 0.76mm thickness, 1.5mm width and 7.62mm gage length. Three different type of testing environment are air, 99.99% Ar gas and vacuum. In the same environmental condition, there was no effect of specimen size on time to rupture. Time to rupture of Mod. 9Cr-1Mo steel in Ar gas was shorter than that in air and vacuum. Oxide thickness is not dominant factor in time to rupture. Fracture mode at specimen surface in Ar gas might be dominant factor in shorter time to rupture. Effect of specimen size and environment on creep strength of Mod. 9Cr-1Mo steel was evaluated on the basis of thinning.
Nishitani, Tomohiro; Nakanishi, Tsutomu*; Yamamoto, Masahiro*; Okumi, Shoji*; Furuta, Fumio*; Miyamoto, Masaharu*; Kuwahara, Makoto*; Yamamoto, Naoto*; Naniwa, Kenichi*; Watanabe, Osamu*; et al.
Journal of Applied Physics, 97(9), p.094907_1 - 094907_6, 2005/05
Times Cited Count：68 Percentile：87.74(Physics, Applied)no abstracts in English
Ito, Akinori; Akabori, Mitsuo; Takano, Masahide; Ogawa, Toru; Numata, Masami; Itonaga, Fumio
Journal of Nuclear Science and Technology, 39(Suppl.3), p.737 - 740, 2002/11
no abstracts in English
Inagaki, Yaohiro*; Idemitsu, Kazuya*; Arima, Tatsumi*; Maeda, Toshikatsu; Ogawa, Hiromichi; Itonaga, Fumio
Materials Research Society Symposium Proceedings, Vol.713, p.589 - 596, 2002/00
A large number of studies on HLW glass corrosion have shown that the glass reacts with water to form more stable mineral phases (alteration phases) during the long-term geological disposal. The phase formation is essential to evaluate the radionuclide release from the glass during the long-term disposal. The purpose of this study is to evaluate, experimentally, the mineral phase formation from HLW glass and the associated cesium release. Static corrosion tests were performed on powdered R7T7 glass in alkalline solutions at elevated temperatures to accelerate the reaction, and mineral phases formed were analyzed by XRD. The results showed that analcime (zeolite) is formed as the dominant phase coexisting with SiO
(am), and beidellite(smectite) or gibbsite coexists dependiting on the conditions. The solution analysis indicated that most of the cesium is retained in the phases of beidellite and analcime by sorption.
Ogawa, Fumio*; Imagawa, Yuya; Hashidate, Ryuta; Wakai, Takashi; Hiyoshi, Noritake*; Ito, Takamoto*
no journal, ,
Multiaxial creep-fatigue tests in tension and torsion were performed on Mod.9Cr-1Mo steel at 550
C. Specificity was observed with respect to strain rate and retention time dependence, indicating that creep-fatigue life is governed by the maximum stress and the degree of stress relaxation. The hysteresis energy was calculated and the lifetime was organized considering the effect of non-proportional loading. Specifically, the mechanism of hysteresis onset was examined, and the energy formulation was made considering the hardening index and relaxation stress. Although the life evaluation has been organized with coefficients of 2.9 and 2.2, this study was conducted with the goal of first organizing the life evaluation with a coefficient of 2.
Okamoto, Masayuki*; Nakayama, Yuta*; Ogawa, Fumio*; Hashidate, Ryuta; Hiyoshi, Noritake*; Wakai, Takashi; Ito, Takamoto*
no journal, ,
no abstracts in English
Kanayama, Hideyuki; Hiyoshi, Noritake*; Ogawa, Fumio*; Ito, Takamoto*; Wakai, Takashi
no journal, ,
no abstracts in English
Ogawa, Fumio*; Imagawa, Yuya; Hashidate, Ryuta; Hiyoshi, Noritake*; Ito, Takamoto*
no journal, ,
In recent years, the demand for environmental protection has led to a trend toward shorter startup and shutdown intervals in thermal power plants. In fast breeder reactors (FBRs), more stringent operating environments (temperature and sodium environment) are also being considered. Modified 9Cr-1Mo steel is used in thermal power plants and fast breeder reactors because of its excellent mechanical properties at high temperatures. In actual machines, Modified 9Cr-1Mo steel is used in a creep-fatigue type with complex stress conditions, which may cause more damage than the uniaxial condition, so it is necessary to measure the multiaxial creep-fatigue life and establish a life evaluation method. In this study, axial and torsional multiaxial creep-fatigue tests were conducted in 550C air to accumulate property data and to evaluate the life. The results will be described later, but the strain rate and retention time dependence showed peculiarities different from those in the past. Next, the strain energy corresponding to the hysteresis loop area between stress and strain was calculated to evaluate the life, and the same energy was theorized to compare the actual and theoretical life. Specifically, a new life evaluation method based on strain energy was studied, which can evaluate the peculiar strain rate, retention time dependence, and multiaxial state observed in the proportional loading test.
Ogawa, Fumio*; Nakayama, Yuta*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*
no journal, ,
The strain energy-based life evaluation method of Mod. 9Cr-1Mo steel under nonproportional multiaxial creep-fatigue loading is proposed. Inelastic strain energy densities were calculated as the areas inside the hysteresis loops. The effect of mean stress has been experimentally considered and the relationship between inelastic strain energy densities and creep-fatigue lives was investigated. It was found from the investigation of hysteresis loops, the decrease in maximum stress leads to prolonged failure life, while stress relaxation during strain holding causes strength reduction. The correction method of inelastic strain energy density was proposed considering the effect of maximum stress in hysteresis loop and minimum stress during strain holding. Furthermore, this result is investigated by overlooking hysteresis data and the mechanisms governing creep-fatigue lives under nonproportional multiaxial loading have been discussed.
