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Masaaki Igarashi - One of the best experts on this subject based on the ideXlab platform.
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cr concentration dependence of overestimation of long term Creep life in strength enhanced high cr ferritic steels
International Journal of Pressure Vessels and Piping, 2010Co-Authors: Kouichi Maruyama, Kyosuke Yoshimi, Mitsuru Yoshizawa, Ghassemi H Armaki, R P Chen, Masaaki IgarashiAbstract:Abstract Creep Rupture Data and microstructural degradation during aging of high Cr ferritic boiler steels with enhanced Creep strength have been studied with special attention to prediction of long term Creep Rupture life. Tempered lath martensite structure in the high Cr ferritic steels remains unchanged during short term aging, whereas static recovery of the lath martensite structure proceeds when diffusion distance during aging becomes sufficiently long as is the case in long term Creep. The static recovery brings about premature failure in long term Creep and decreases in apparent activation energy for Creep life. The decrease in activation energy is responsible for overestimation of Rupture life reported in strength enhanced high Cr ferritic steels. The boundary from a short term region with high activation energy QH to a long term region with low activation energy QL moves towards longer time with decreasing Cr concentration. The difference in activation energy (QH − QL) primarily determines the extent of overestimation of Rupture life predicted from short term Data. In general, the extent of overestimation is less serious at 9%Cr as compared to 12%Cr.
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prevention of the overestimation of long term Creep Rupture life by multiregion analysis in strength enhanced high cr ferritic steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Hassan Ghassemi Armaki, Kouichi Maruyama, Mitsuru Yoshizawa, Masaaki IgarashiAbstract:Abstract Long-term Creep Rupture life is often evaluated from short-term Data by a time–temperature parameter (TTP) method. However the conventional TTP methods sometimes fail in understanding Creep Rupture behavior of strength enhanced high Cr ferritic steels and overestimate Creep Rupture life in long-term Creep. In the present paper, Creep Rupture Data of seven kinds of heat resistant steels with different W and Cr concentrations have been analyzed. The conventional TTP method like Orr–Sherby–Dorn analysis evaluates long-term Creep Rupture life assuming a unique value of activation energy for all the Creep Rupture Data. This analysis is called single region analysis in this paper. The single region analysis can represent well the Creep Rupture Data of steels containing less than 8% Cr. The Creep Rupture analyses of steels containing more than 8% Cr exhibit that apparent activation energy changes from a high value in short-term Creep region to a low value in long-term Creep region. In each case a Creep Data was divided into several Data sets, and then the conventional single region analysis was applied to each divided Data set. This analysis is referred to as multiregion analysis. The multiregion analysis describes very well all the Data points, whereas regression curves of the single region analysis deviate from the Data points, resulting in overestimation of long-term Rupture life. The difference between the two activation energies of short-term and long-term Creep increases with increasing Cr concentration. Therefore, the overestimation due to singles region analysis is expected to be more serious at higher Cr concentration.
Kouichi Maruyama - One of the best experts on this subject based on the ideXlab platform.
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ultrahigh temperature tensile Creep of tic reinforced mo si b based alloy
Scientific Reports, 2018Co-Authors: Shiho Yamamoto Kamata, Daiki Kanekon, Nobuaki Sekido, Kouichi Maruyama, G Eggeler, Kyosuke YoshimiAbstract:In this study, the ultrahigh-temperature tensile Creep behaviour of a TiC-reinforced Mo-Si-B-based alloy was investigated in the temperature range of 1400–1600 °C at constant true stress. The tests were performed in a stress range of 100–300 MPa for 400 h under vacuum, and Creep Rupture Data were rationalized with Larson-Miller and Monkman-Grant plots. Interestingly, the MoSiBTiC alloy displayed excellent Creep strength with relatively reasonable Creep parameters in the ultrahigh-temperature range: a Rupture time of ~400 h at 1400 °C under 137 MPa with a stress exponent (n) of 3 and an apparent activation energy of Creep (Qapp) of 550 kJ/mol. The increasing Rupture strains with decreasing stresses (up to 70%) and moderate strain-rate oscillations in the Creep curves suggest that two mechanisms contribute to the Creep: phase boundary sliding between the hard T2 and (Ti,Mo)C phases and the Moss phase, and dynamic recovery and recrystallization in Moss, observed with orientation imaging scanning electron microscopy. The results presented here represent the first full analysis of Creep for the MoSiBTiC alloy in an ultrahigh-temperature range. They indicate that the high-temperature mechanical properties of this material under vacuum are promising.
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cr concentration dependence of overestimation of long term Creep life in strength enhanced high cr ferritic steels
International Journal of Pressure Vessels and Piping, 2010Co-Authors: Kouichi Maruyama, Kyosuke Yoshimi, Mitsuru Yoshizawa, Ghassemi H Armaki, R P Chen, Masaaki IgarashiAbstract:Abstract Creep Rupture Data and microstructural degradation during aging of high Cr ferritic boiler steels with enhanced Creep strength have been studied with special attention to prediction of long term Creep Rupture life. Tempered lath martensite structure in the high Cr ferritic steels remains unchanged during short term aging, whereas static recovery of the lath martensite structure proceeds when diffusion distance during aging becomes sufficiently long as is the case in long term Creep. The static recovery brings about premature failure in long term Creep and decreases in apparent activation energy for Creep life. The decrease in activation energy is responsible for overestimation of Rupture life reported in strength enhanced high Cr ferritic steels. The boundary from a short term region with high activation energy QH to a long term region with low activation energy QL moves towards longer time with decreasing Cr concentration. The difference in activation energy (QH − QL) primarily determines the extent of overestimation of Rupture life predicted from short term Data. In general, the extent of overestimation is less serious at 9%Cr as compared to 12%Cr.
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prevention of the overestimation of long term Creep Rupture life by multiregion analysis in strength enhanced high cr ferritic steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Hassan Ghassemi Armaki, Kouichi Maruyama, Mitsuru Yoshizawa, Masaaki IgarashiAbstract:Abstract Long-term Creep Rupture life is often evaluated from short-term Data by a time–temperature parameter (TTP) method. However the conventional TTP methods sometimes fail in understanding Creep Rupture behavior of strength enhanced high Cr ferritic steels and overestimate Creep Rupture life in long-term Creep. In the present paper, Creep Rupture Data of seven kinds of heat resistant steels with different W and Cr concentrations have been analyzed. The conventional TTP method like Orr–Sherby–Dorn analysis evaluates long-term Creep Rupture life assuming a unique value of activation energy for all the Creep Rupture Data. This analysis is called single region analysis in this paper. The single region analysis can represent well the Creep Rupture Data of steels containing less than 8% Cr. The Creep Rupture analyses of steels containing more than 8% Cr exhibit that apparent activation energy changes from a high value in short-term Creep region to a low value in long-term Creep region. In each case a Creep Data was divided into several Data sets, and then the conventional single region analysis was applied to each divided Data set. This analysis is referred to as multiregion analysis. The multiregion analysis describes very well all the Data points, whereas regression curves of the single region analysis deviate from the Data points, resulting in overestimation of long-term Rupture life. The difference between the two activation energies of short-term and long-term Creep increases with increasing Cr concentration. Therefore, the overestimation due to singles region analysis is expected to be more serious at higher Cr concentration.
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multiregion analysis of Creep Rupture Data of 316 stainless steel
International Journal of Pressure Vessels and Piping, 2007Co-Authors: Kouichi Maruyama, Hassan Ghassemi Armaki, Kyosuke YoshimiAbstract:Abstract A Creep Rupture Data set of 316 stainless steel containing 319 Data points at nine heats was subjected to a conventional single-region analysis and a multiregion analysis. In the former, the conventional Larson–Miller analysis was applied to the whole Data set. In the latter, a Data set of a single heat is divided into several Data sets, so that the Orr–Sherby–Dorn (OSD) constant Q takes a unique value in each Data set, and the conventional OSD analysis was applied to each divided Data set. A region with a low value of Q appears in long-term Creep of eight heats. Predicted values of the 10 5 h Creep Rupture stress of three heats were lower than the 99% confidence limit evaluated by the single-region analysis, suggesting that the single-region analysis is error prone. The multiregion analysis is necessary for the correct evaluation of the long-term Creep properties of 316 stainless steel.
Yukio Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Masaaki Tabuchi Evaluation of Creep Strength Reduction Factors for Welded Joints of Modified 9Cr-1Mo Steel
2020Co-Authors: Yukio TakahashiAbstract:Creep strength of welded joint for high Cr ferritic heat resisting steels decreases due to Type-IV failure in heat-affected zone (HAZ) during long-term use at high temperatures. In order to review the allowable Creep strength of these steels, Creep Rupture Data of base metals and welded joints have been collected, and long-term Creep strength has been evaluated in the SHC (strength of high-chromium steel) committee in Japan. In the present paper, the Creep Rupture Data of 370 points for welded joint specimens of modified 9Cr-1Mo steel (ASME Grade 91 steel) offered from seven Japanese companies and institutes were analyzed. These Data clearly indicated that the Creep strength of welded joints was lower than that of base metal due to Type-IV failure in HAZ at high temperatures. From the activities of this committee, it was concluded that the weld strength reduction factor (WSRF) should be taken into consideration for the design and residual life assessment of boiler components in fossil power plants. The committee recommended the WSRF for 100,000 h Creep of Gr.91 steel as 0.85 at 575 C, 0.75 at 600 C, 0.74 at 625 C, and 0.70 at 650 C. The master curve for residual life assessment of Gr.91 steel welds using Larson-Miller parameter was also proposed
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Evaluation of Creep strength reduction factors for welded joints of Grade 122 steel
2020Co-Authors: Yukio Takahashi, Masaaki TabuchiAbstract:ABSTRACT HCM12A (ASME Grade 122) is used for boiler components in thermal power plants because of its high Creep strength. However, type IV Creep damage formed in heat affected zone brings about considerable decrease in Creep strength of the weldment and a failure of large diameter piping in a thermal power plant due to this damage took place recently. In order to update the design method and develop life estimation method for this kind of piping system with axial weld, Creep Rupture Data of base metal and welded joints has been collected and analyzed in the SHC (Strength of HighChromium Steel) committee in Japan since 2004. In the present paper, the Creep Rupture Data of over 400 points for welded joint specimens of HCM12A offered from six Japanese organizations were analyzed. These Data clearly indicated that the long-term Creep strength of welded joints becomes weaker than that of base metal at above 600C due to Type IV fracture in fine grain heat-affected zone. After discussing the effects of product form, welding procedure and specimen sampling etc. on the Creep strength, the master Creep life equation for the welded joints was developed. So-called region decomposition technique was adopted to fit the Data both in high and low stress regimes with a reasonable accuracy. The Creep strength reduction factor obtained from 100,000 hours Creep strength of welded joints and base metal was given as a function of temperature
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evaluation of long term Creep strength of asme grades 91 92 and 122 type steels
ASME 2012 Pressure Vessels and Piping Conference, 2012Co-Authors: Kazuhiro Kimura, Yukio TakahashiAbstract:Creep Rupture Data of ASME Grades 91, 92 and 122 type steels have been collected and long-term Creep Rupture strength of the steels has been evaluated. Similar study was conducted by the SHC committee in 2004 and 2005, therefore, the evaluation of long-term Creep Rupture strength was conducted with emphasis on the long-term Creep Rupture Data obtained after the previous study. Creep Rupture strength was analyzed by means of region splitting analysis method in consideration of 50% of 0.2% offset yield strength, in the same way as the previous study. Almost the same results were obtained on base metal of Grade 92 as the previous study, however, evaluated 100,000 hours Creep Rupture strength of base metal of Grades 91 and 122 were lower than the previous results. For Grades 91 and 122 type steels, moreover, Creep Rupture strength of the plate steel were lower than those of pipe and forging steels. Tendency to decrease with increase in nickel content was observed on long-term Creep Rupture strength of tube steel of Grade 91 at 600°C. According to the evaluation of long-term Creep strength of the steels, allowable tensile stress was reviewed and proposed revision was concluded.Copyright © 2012 by ASME
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long term Creep strength and strength reduction factor for welded joints of asme grades 91 92 and 122 type steels
International Journal of Microstructure and Materials Properties, 2011Co-Authors: Kazuhiro Kimura, Masaaki Tabuchi, Yukio Takahashi, Kazuo Yoshida, Koichi YagiAbstract:Creep Rupture Data of base metal and welded joints of several Creep strength enhanced ferritic (CSEF) steels was collected and long-term Creep strength of those steels was evaluated by the SHC committee in Japan. The previous allowable tensile stress of those steels regulated in METI Thermal Power Standard Code was reviewed and weld strength reduction factor was investigated. The master Creep life equations for not only base metal, but also welded joints were developed. According to the evaluated Creep Rupture strength, allowable tensile stress of ASME Grade 122 type steels was revised in December 2005 and those of ASME Grade 91 and 92 type steels was revised in August 2007. The Creep strength reduction factor obtained from 100,000 hours Creep Rupture strength of welded joints and base metal was given as a function of temperature.
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long term Creep Rupture behavior of smoothed and notched bar specimens of low carbon nitrogen controlled 316 stainless steel 316fr and their evaluation
Nuclear Engineering and Design, 2008Co-Authors: Yukio Takahashi, Hiroshi Shibamoto, Kazuhiko InoueAbstract:Abstract Low-carbon, nitrogen-controlled 316 stainless steel is regarded as a principal candidate for a main structural material of future fast breeder reactor plants in Japan. To grasp Creep deformation and Rupture behavior of this steel whose modeling is indispensable in the design of high-temperature components, a number of uniaxial tensile Creep tests have been conducted for four products of this steel at 550 °C and higher temperatures. Long-term Creep Rupture Data up to about 94,000 h were obtained and used to examine the applicability of Rupture and deformation estimation methods developed earlier. In addition, two tests were conducted using round-bar specimens with circumferential notches to make investigation of the effect of stress multiaxiality on Creep damage.
Takahiko Sagawa - One of the best experts on this subject based on the ideXlab platform.
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temperature dependence of off axis tensile Creep Rupture behavior of a unidirectional carbon epoxy laminate
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract:Abstract Stress-time-temperature extrapolation of off-axis Creep Rupture Data on a T800H/2500 unidirectional carbon/epoxy laminate is studied. Off-axis tensile Creep Rupture tests are performed on plain coupon specimens with five kinds of fiber orientations θ = 0, 10, 30, 45 and 90° at each of the test temperatures of 60, 80 and 130 °C, respectively, within the time range up to 10 h. Creep Rupture of unidirectional specimens takes place predominantly along the fibers in a brittle manner, regardless of the fiber orientation and test temperature. Straight lines can be fitted well to the log–log plots of Creep stress level against the time to Rupture over the restricted range of time for all fiber orientations, regardless of the test temperature. Those fitted straight lines for different fiber orientations at each test temperature are almost parallel to each other, and they are approximately extrapolated to the stress levels nearly equal to the off-axis tensile strengths at the test temperature. The fiber orientation dependence of the off-axis Creep Rupture Data obtained at each test temperature can approximately be removed by normalizing the Creep stress levels with the help of the off-axis tensile strengths, which allows identification of a single fiber-orientation-independent master Creep Rupture curve for each test temperature. The effect of temperature on Creep strength is reflected by the change in slope of the normalized master Creep Rupture curve. For predicting the off-axis Creep Rupture lives at different stress levels and temperatures, two kinds of new and efficient engineering methods are developed. One method is based on a formula derived from a modified damage mechanics model for Creep Rupture. The other one is formulated on the basis of a grand master Creep Rupture curve built by means of a non-dimensional effective stress and the Larson–Miller parameter. The proposed damage mechanics and grand master curve approaches are validated in respect of accuracy of prediction of the off-axis Creep Rupture lives of the unidirectional carbon/epoxy composite at different stress levels over a range of temperatures.
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off axis tensile Creep Rupture behavior of a unidirectional cfrp laminate at high temperatures
Transactions of the Japan Society of Mechanical Engineers. A, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract:Creep Rupture behavior of a unidirectional carbon/epoxy T800H/Epoxy Laminate under constant off-axis loading conditions at different temperatures of 60, 100 and 130°C is examined. Tensile Creep Rupture tests are performed on plain coupon specimens with different fiber orientations θ=0, 10, 30, 45 and 90°. Creep Rupture of specimens takes place predominantly along reinforcing fibers is a brittle manner, regardless of the fiber orientation. The log-log plots of the Creep Rupture Data can approximately be described using straight lines with negative slopes over the range of Rupture time up to 10h, regardless of the fiber orientation. Then, two kinds of simple phenomenological models are developed for predicting the time-to-failure of unidirectional composites. Validities of those models are evaluated by comparing with experimental results. It is demonstrated that the proposed models succeed in adequately predicting the Creep Rupture lives of the unidirectional composite at different temperatures.
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off axis tensile Creep Rupture of unidirectional cfrp laminates at elevated temperature
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: Masamichi Kawai, Y Masuko, Takahiko SagawaAbstract:Abstract Off-axis tensile Creep fracture behavior of unidirectional carbon/epoxy T800H/Epoxy laminates is studied at 100 °C under constant load conditions. Off-axis Creep Rupture Data on plain coupon specimens are obtained within the time range up to 10 h for four kinds of off-axis fiber orientations. The log–log plots of the Creep stress against the Rupture time can approximately be described by straight lines with negative slopes over the range of Creep life for all the fiber orientations. The static tensile strengths extrapolated from those straight lines almost agree with the experimental results for respective fiber orientations. The Creep Rupture Data normalized with respect to the static strength approximately falls on a single Creep Rupture curve. These observations suggest that the fiber orientation dependence of Creep Rupture strength is similar to that of static tensile strength. The Creep fracture occurs along reinforcing fibers in a brittle manner without accompanying the appreciable secondary and tertiary Creep stages, regardless of the fiber orientations, and thus the off-axis Creep deformation prior to fracture is characterized by the primary Creep stage for all the fiber orientations. Then, a phenomenological model for the Creep deformation and Rupture behaviors of the unidirectional composite is developed, with a view to making preliminary predictions of Creep life from a limited amount of Data. It is demonstrated that the proposed model can moderately describe the observed features of the Creep deformation and Creep Rupture behaviors under off-axis loading conditions.
Kyosuke Yoshimi - One of the best experts on this subject based on the ideXlab platform.
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ultrahigh temperature tensile Creep of tic reinforced mo si b based alloy
Scientific Reports, 2018Co-Authors: Shiho Yamamoto Kamata, Daiki Kanekon, Nobuaki Sekido, Kouichi Maruyama, G Eggeler, Kyosuke YoshimiAbstract:In this study, the ultrahigh-temperature tensile Creep behaviour of a TiC-reinforced Mo-Si-B-based alloy was investigated in the temperature range of 1400–1600 °C at constant true stress. The tests were performed in a stress range of 100–300 MPa for 400 h under vacuum, and Creep Rupture Data were rationalized with Larson-Miller and Monkman-Grant plots. Interestingly, the MoSiBTiC alloy displayed excellent Creep strength with relatively reasonable Creep parameters in the ultrahigh-temperature range: a Rupture time of ~400 h at 1400 °C under 137 MPa with a stress exponent (n) of 3 and an apparent activation energy of Creep (Qapp) of 550 kJ/mol. The increasing Rupture strains with decreasing stresses (up to 70%) and moderate strain-rate oscillations in the Creep curves suggest that two mechanisms contribute to the Creep: phase boundary sliding between the hard T2 and (Ti,Mo)C phases and the Moss phase, and dynamic recovery and recrystallization in Moss, observed with orientation imaging scanning electron microscopy. The results presented here represent the first full analysis of Creep for the MoSiBTiC alloy in an ultrahigh-temperature range. They indicate that the high-temperature mechanical properties of this material under vacuum are promising.
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cr concentration dependence of overestimation of long term Creep life in strength enhanced high cr ferritic steels
International Journal of Pressure Vessels and Piping, 2010Co-Authors: Kouichi Maruyama, Kyosuke Yoshimi, Mitsuru Yoshizawa, Ghassemi H Armaki, R P Chen, Masaaki IgarashiAbstract:Abstract Creep Rupture Data and microstructural degradation during aging of high Cr ferritic boiler steels with enhanced Creep strength have been studied with special attention to prediction of long term Creep Rupture life. Tempered lath martensite structure in the high Cr ferritic steels remains unchanged during short term aging, whereas static recovery of the lath martensite structure proceeds when diffusion distance during aging becomes sufficiently long as is the case in long term Creep. The static recovery brings about premature failure in long term Creep and decreases in apparent activation energy for Creep life. The decrease in activation energy is responsible for overestimation of Rupture life reported in strength enhanced high Cr ferritic steels. The boundary from a short term region with high activation energy QH to a long term region with low activation energy QL moves towards longer time with decreasing Cr concentration. The difference in activation energy (QH − QL) primarily determines the extent of overestimation of Rupture life predicted from short term Data. In general, the extent of overestimation is less serious at 9%Cr as compared to 12%Cr.
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multiregion analysis of Creep Rupture Data of 316 stainless steel
International Journal of Pressure Vessels and Piping, 2007Co-Authors: Kouichi Maruyama, Hassan Ghassemi Armaki, Kyosuke YoshimiAbstract:Abstract A Creep Rupture Data set of 316 stainless steel containing 319 Data points at nine heats was subjected to a conventional single-region analysis and a multiregion analysis. In the former, the conventional Larson–Miller analysis was applied to the whole Data set. In the latter, a Data set of a single heat is divided into several Data sets, so that the Orr–Sherby–Dorn (OSD) constant Q takes a unique value in each Data set, and the conventional OSD analysis was applied to each divided Data set. A region with a low value of Q appears in long-term Creep of eight heats. Predicted values of the 10 5 h Creep Rupture stress of three heats were lower than the 99% confidence limit evaluated by the single-region analysis, suggesting that the single-region analysis is error prone. The multiregion analysis is necessary for the correct evaluation of the long-term Creep properties of 316 stainless steel.