Statistical Modeling of Creep Rupture Data

1999 ◽  
Vol 121 (3) ◽  
pp. 264-271 ◽  
Author(s):  
R. B. Davies ◽  
R. Hales ◽  
J. C. Harman ◽  
S. R. Holdsworth
Keyword(s):  
Statistical Modeling ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Confidence Limits ◽  
Creep Rupture Strength ◽  
Statistical Research ◽  
Modeling Framework ◽  
Failure Times ◽  
Rupture Data ◽  
Model Improvement

A flexible statistical modeling framework for the analysis of creep rupture data is proposed, which offers an improvement on traditional methods of deriving creep rupture strength values and confidence limits. The paper reviews a family of models that can be used to represent the trend relationship between failure times about the trend line, and examines the reliability of extrapolations. Areas of statistical research which would lead to model improvement are discussed, such as variance heterogeneity, left censoring and allowance for the cluster (cast) structure of the data.

Evaluation of Long-Term Creep Strength of Welded Joints of ASME Grades 91, 92 and 122 Type Steels

2012 ◽  
Author(s):  
Masatsugu Yaguchi ◽  
Takuaki Matsumura ◽  
Katsuaki Hoshino
Keyword(s):  
Creep Strength ◽  
Welded Joints ◽  
Rupture Strength ◽  
Reduction Factor ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Strength Reduction Factor ◽  
Rupture Data ◽  
Term Creep

Creep rupture data of welded joints of ASME Grades 91, 92 and 122 type steels have been collected and long-term creep rupture strength of the materials has been evaluated. Similar study was conducted by the SHC Committee in 2004 and 2005, therefore, the evaluation of the creep rupture strength was conducted with emphasis on the long-term creep rupture data obtained after the previous study, in addition to discussion of the effects of product form, welding procedure and test temperature etc. on the creep strength. Almost the same results were obtained on the welded joint of Grade 92 as the previous study, however, the master creep life equations for the welded joints of Grades 91 and 122 were lower than the previous results, especially in the case of Grade 122. Furthermore, 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.

Influence of Data Scattering on Estimation of 100,000 hrs Creep Rupture Strength of Alloy 617 at 700 °C by Larson–Miller Method

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Fujio Abe ◽  
M. Tabuchi ◽  
M. Hayakawa
Keyword(s):  
Regression Analysis ◽  
Rupture Strength ◽  
Large Data ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Alloy 617 ◽  
Time To Rupture ◽  
Reciprocal Temperature ◽  
Rupture Data ◽  
C Value

The 100,000 hrs creep rupture strength of Alloy 617 at 700 °C is estimated by Larson–Miller method using the rupture data of longer duration than 500 hrs in the temperature range between 593 and 816 °C, corresponding to 700 ± 100 °C. The maximum time to rupture was 40,126.7 hrs. The rupture data exhibit large scattering, especially at 760 °C. After eliminating the shorter time to rupture data at 760 °C, the regression analysis gives us the Larson–Miller constant C = 12.70 and the 100,000 hrs creep rupture strength of 100 MPa at 700 °C, by Swindeman program. The present regression analysis underestimates the constant C and 100,000 hrs creep rupture strength. The linear extrapolation of log tr versus reciprocal temperature 1/T plots to 1/T = 0 gives us an average C value of Cav = 18.5, which is much larger than the constant C of 12.70 obtained by the Swindeman program. It is concluded that the origin of underestimation of the constant C and corresponding 100,000 hrs creep rupture strength is large data scattering. Using an appropriate constant C of 18.45, the 100,000 hrs creep rupture strength at 700 °C is estimated to be 123 MPa. Using the rupture data including the shorter time to rupture data at 760 °C and using C = 18.45, the 100,000 hrs creep rupture strength at 700 °C is estimated to be 116 MPa.

Re-Evaluation of Long-Term Creep Strength of Base Metal of ASME Grade 91 Type Steel

2016 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Masatsugu Yaguchi
Keyword(s):  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Creep Data ◽  
High Chromium ◽  
Rupture Data ◽  
Assessment Committee ◽  
Grade 91 ◽  
Term Creep

Creep rupture strength of ASME Grades 91, 92, 122 and 23 type steels were evaluated by the SHC committee in 2004 and 2005, and the Assessment Committee on Creep Data of High Chromium Steels in 2010. According to the evaluation of creep rupture strength, allowable stress of the steels was revised and weld strength reduction factor (WSRF) was established. In 2015, the creep rupture data of those steels was collected from materials producers, power plant manufacturers and institutes in Japan and a review of long-term creep rupture strength of the steels was conducted by the Assessment Committee on Creep Data of High Chromium Steels in reference to the previous evaluation. It has been confirmed with the latest dataset that re-evaluation of long-term creep rupture strength is not required for Grades 92, 122 and 23 type steels. On the other hand, lower creep rupture strength compared with the previous evaluation was recognized on the new creep rupture data of Grade 91 steels, therefore, re-evaluation of creep rupture strength was conducted on Grade 91 steels. Creep rupture strength was assessed 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. According to the evaluation of long-term creep strength of the steels, allowable tensile stress was reviewed and proposed revision was concluded.

Evaluation of Long-Term Creep Strength of ASME Grades 91, 92, and 122 Type Steels

2012 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Yukio Takahashi
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Rupture Strength ◽  
Nickel Content ◽  
Creep Rupture ◽  
Tube Steel ◽  
Creep Rupture Strength ◽  
Rupture Data ◽  
Term Creep

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.

Evaluation of Stress Rupture Factors for Grade 91 Weldments

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Kazuhiro Kimura ◽  
Masatsugu Yaguchi
Keyword(s):  
Base Metal ◽  
Rupture Strength ◽  
Stress Rupture ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Premature Failure ◽  
Rupture Data ◽  
Grade 91 ◽  
Grade 91 Steel

Abstract Stress rupture factors and weld strength reduction factors for Grade 91 steel weldments in the codes and literatures have been reviewed. Stress rupture factors for weld metals proposed for code case N-47 in the mid 1980's was defined as a ratio of average rupture strength of the deposited filler metal to the average rupture strength of the base metal. Remarkable drop in creep rupture strength of weldments is significant issue of Grade 91, especially in the low-stress and long-term regime. A premature failure of Grade 91 steel weldments in the long-term, however, is caused by type IV failure which takes place in the fine grain heat affected zone (FG-HAZ), rather than fracture in the deposited weld metal. The stress rupture factor of the Grade 91 steel, therefore, was based on the creep rupture strength of cross weld test specimens. Creep rupture data of Grade 91 steel weldments reported in the publication of ASME STP-PT-077 were integrated with the creep rupture data collected in Japan and used for this study. Time- and temperature-dependent stress rupture factors for Grade 91 steel have been evaluated based on the consolidated database as a ratio of average creep rupture strength of cross weld test specimen to the average creep rupture strength of base metal.

Assessment of Long-Term Creep Rupture Strength of T91 Steel by Multiregion Rupture Data Analysis

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
K. Maruyama ◽  
J. Nakamura ◽  
K. Yoshimi
Keyword(s):  
Rupture Strength ◽  
Creep Rupture ◽  
Data Selection ◽  
Creep Rupture Strength ◽  
Rupture Data ◽  
Data Points ◽  
Service Conditions ◽  
Term Creep ◽  
Term Data

Creep rupture strength of creep strength enhanced ferritic steels is often overestimated, and its evaluated value has been reduced repeatedly. In this paper, the cause of the overestimation is discussed, and the creep rupture strength of T91 steel is assessed with its updated creep rupture data. Effects of residual Ni concentration on the creep rupture strength and necessity of F factor in T91 steel are also discussed. Decrease in activation energy Q for rupture life in long-term creep is the cause of the overestimation, since conventional time–temperature parameter (TTP) methods cannot deal with the change in Q. Due to the decrease in Q, long-term creep rupture strength evaluated decreases as longer-term data points are added or shorter-term data points are discarded in the conventional TTP analysis. The long-term region with small values of activation energy and stress exponent is named region L2 in this paper. Region L2 appears in all the heats of T91 steel and plate products of Gr.91 steel. Since service conditions of the T91 steel are usually in region L2, the creep rupture strength under the service conditions should be evaluated from the rupture data in region L2 only. The 5 × 105 hrs rupture strength at 550 °C decreases from 129 MPa (evaluated from the whole data of T91 steel) to 79 MPa (evaluated from the data in region L2 only) with increasing cut-off time for data selection. The 105 hrs rupture strength at 600 °C also decreases from 87 MPa (whole data) to 70 MPa (region L2 only) despite sufficient number of long-term data points at 600 °C. Careful consideration on the data selection is necessary in evaluation of creep rupture strength of the T91 steel. A multiregion rupture data analysis (MRA) is helpful to select data points belonging to region L2.

Reliability Design for Allowable Stress of Creep Rupture Strength of 4Cr25Ni35 Steel

2012 ◽  
Vol 476-478 ◽  
pp. 2552-2555
Author(s):  
Ji Bin Pei ◽  
Yun Feng Zhao ◽  
Shao Ping Yu ◽  
Jie Zhao
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Parameter Method ◽  
Allowable Stress ◽  
Creep Rupture Strength ◽  
Reliability Design ◽  
Z Parameter ◽  
Rupture Data

Creep rupture data plays vital role in life prediction and safety assessment of high temperature components. In order to describe the scattering of the data, a statistical analysis of creep rupture data for 4Cr25Ni35 steel was performed by Z-parameter method. With the application of Z-parameter, reliability design for allowable stress of creep rupture strength was carried out according to design life. It is found that Manson-Haferd method appears better correlation results with experimental data. Statistical analysis shows that the scattering of Z-parameter for 4Cr25Ni35 steel is supported by normal distribution. Compared with safety factor method, the method based on Z-parameter can perform reliability design for allowable stress of creep rupture strength by considering the dispersibility of the rupture data. Reliability design based on Z-parameter is more agree with experimental data.

Reliability Design for Creep Rupture Strength of 2.25Cr-1Mo Steel

2011 ◽  
Vol 675-677 ◽  
pp. 507-510
Author(s):  
Ji Bin Pei ◽  
Yun Feng Zhao ◽  
Dong Ming Li ◽  
Jie Zhao ◽  
Lai Wang
Keyword(s):  
Rupture Strength ◽  
Creep Rupture ◽  
Parameter Method ◽  
Allowable Stress ◽  
Creep Rupture Strength ◽  
Reliability Design ◽  
Design Life ◽  
Real Distribution ◽  
Z Parameter ◽  
Rupture Data

A statistical analysis of creep rupture data for 2.25Cr-1Mo steel was performed. The scattering of creep rupture data was represented by Z-parameter method based on Manson-Haferd method. With the application of Z-parameter, reliability design for allowable stress of creep rupture strength was carried out according to design life. The higher the value of confidence level, the lower the allowable stress. In comparison with safety factor method and minimum rupture strength method, it can be seen that reliability design based on Z-parameter is more agree with experimental data than other methods. Reliability design provides more precise results by considering the real distribution of creep rupture property and provides more flexible choice for design due to the need of safety and economy.

Influence of Oxidation on Estimation of Long-Term Creep Rupture Strength of 2.25Cr–1Mo Steel by Larson–Miller Method

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Fujio Abe
Keyword(s):  
Materials Science ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Creep Life ◽  
Creep Tests ◽  
Initial Strength ◽  
Rupture Data ◽  
Term Creep

Abstract The influence of oxidation on the estimation of long-term creep rupture strength is investigated for 2.25% chromium (Cr)–1% molybdenum (Mo) steel specified as JIS STBA 24, JIS SCMV 4 NT, and ASTM A542/A542M by the Larson–Miller method using creep rupture data in the National Institute for Materials Science (NIMS) Creep Data Sheets at 450–650 °C for up to 313,000 h. The creep rupture data exhibit a change in slope of the stress versus time to rupture curves due to oxidation in air during 600 °C creep tests at 15,000–40,000 h and 650 °C tests at 2000–3500 h for different size specimens, which indicates degradation in creep life by the oxidation. The estimated 100,000 h creep rupture strength using regression analysis is increased by the elimination of long-term data degraded by the oxidation. Several metallurgical factors, such as the initial strength represented by the 0.2% proof stress at the creep test temperature and the concentration of aluminum (Al) impurity, also affect the creep life of the tested steel.

KUBOTA ALLOY KHR35C

Alloy Digest ◽  
1999 ◽  
Vol 48 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Temperature Performance

Abstract Kubota alloy KHR35C is similar to HP alloy with the addition of niobium to increase its creep-rupture strength. Typical applications include components and assemblies for severe carburizing environments, such as ethylene pyrolysis coils. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as casting and joining. Filing Code: SS-753. Producer or source: Kubota Metal Corporation.

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