Application of Manson–Haferd and Larson–Miller Methods in Creep Rupture Property Evaluation of Heat-Resistant Steels

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Jie Zhao ◽  
Dong-Ming Li ◽  
Yuan-Yuan Fang
Keyword(s):  
Rupture Life ◽  
Creep Rupture ◽  
Obvious Effect ◽  
Heat Resistant ◽  
Property Evaluation ◽  
Wide Range ◽  
Rupture Data ◽  
Heat Resistant Steels ◽  
Correlation Accuracy ◽  
Selection Of

The current paper discusses the selection of Manson–Haferd and Larson–Miller constants on correlation results of creep rupture property in several heat-resistant steels. It indicates that the change in Larson–Miller constant CLM has obvious effect on the predicting result of rupture life and the optimal CLM values will depend on materials and the optimal ranges of the values are narrow. However, for Manson–Haferd constants Ta and log ta, they are at least phenomenally not independent variables but show a linear relationship: log ta=27.015−0.0267Ta. It is shown that the values of Manson–Haferd constants (Ta,log ta) can be selected in a wide range with desirable correlation accuracy and a set of Manson–Haferd constant (Ta=450, log ta=15) is recommended to correlate the creep rupture data.

Microstructural evolution and creep-rupture life estimation of high-Cr martensitic heat-resistant steels

2015 ◽  
Vol 106 ◽  
pp. 266-272 ◽  
Author(s):  
Kyu-Ho Lee ◽  
Jin-Yoo Suh ◽  
Sung-Min Hong ◽  
Joo-Youl Huh ◽  
Woo-Sang Jung
Keyword(s):  
Microstructural Evolution ◽  
Rupture Life ◽  
Creep Rupture ◽  
Life Estimation ◽  
Heat Resistant ◽  
Heat Resistant Steels

Methodology of Creep Data Analysis for Advanced High Cr Ferritic Steel

2007 ◽  
Author(s):  
Kouichi Maruyama ◽  
Kyosuke Yoshimi
Keyword(s):  
Data Analysis ◽  
Rupture Life ◽  
Creep Rupture ◽  
Creep Data ◽  
Short Term ◽  
Data Set ◽  
Region Analysis ◽  
Rupture Data ◽  
Term Creep

Long term creep rupture life is usually evaluated from short term data by a time-temperature parameter (TTP) method. The apparent activation energy Q for rupture life of steels sometimes changes from a high value of short term creep to a low value of long term creep. However, the conventional TTP analyses ignore the decrease in Q, resulting in the overestimation of rupture life recognized recently in advanced high Cr ferritic steels. A multi region analysis of creep rupture data is applied to a creep data set of Gr.122 steel; in the analysis a creep rupture data is divided into several data sets so that Q value is unique in each divided data set. The multi region analysis provides the best fit to the data and the lowest value of 105 h creep rupture strength among the three ways of data analysis examined. The conventional single region analysis cannot correctly represent the data points and predicts the highest strength. A half of 0.2% proof stress could not be an appropriate boundary for dividing data to be used in the multi region analysis. In the 2001 Edition of ASME Code an F average concept has been proposed as a substitution for the safety factor of 2/3 for average rupture stress. The allowable stress of Gr.122 steel may decrease significantly when the F average concept and the multi region analysis are adopted.

Time to Initiation of Tertiary Creep Property of Grade 91 Steels

2016 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Kota Sawada
Keyword(s):  
Creep Rate ◽  
Minimum Creep Rate ◽  
Rupture Life ◽  
Creep Rupture ◽  
Tertiary Creep ◽  
Time To Initiation ◽  
Wide Range ◽  
Minimum Stress ◽  
Grade 91

Creep deformation property of Grade 91 steels was analyzed on more than 370 creep curves over a wide range of time to rupture from about 10 hours to beyond 100,000 hours, in order to evaluate time to 1% total strain, time to minimum creep rate and time to initiation of tertiary creep. Time to initiation of tertiary creep was assessed as a 0.2% offset with a slope of minimum creep rate. It is difficult to determine time to minimum creep rate precisely, which is a basis of 0.2% offset, however, it has been confirmed that time to initiation of tertiary creep is not sensitive to the time when the creep rate indicates minimum value. Life ratio of 1% total strain time against creep rupture time increases up to about 60% with increase of temperature and decrease of stress. Life ratio of time to initiation of tertiary creep also tends to increase with decrease in stress. However, change of it is in a range of 50 to 60% of creep rupture life over a wide range of creep rupture life from 10 hours to 100,000 hours, and it is not sensitive to creep test temperature. Over a range of temperatures from 500 to 600°C and up to about 200,000 hours, a temperature and time-dependent stress intensity limit, St is controlled by 67% of minimum stress to rupture. However, a difference between 67% of minimum stress to rupture and 80% of minimum stress to initiation of tertiary creep decreases with increases in temperature and time, and both values approach each other in the long-term beyond about 100,000 hours at 600°C. In the long-term beyond about 10,000 hours at 650°C, St is controlled by 80% of minimum stress to initiation of tertiary. The stable life fraction of time to initiation of tertiary creep establish a reliability of a temperature and time-dependent stress intensity limit value.

Reliability Assessment of Creep Rupture Life for Gr.91 Steel by an Interference Model

2011 ◽  
Author(s):  
Woo-Gon Kim ◽  
Jae-Young Park ◽  
Song-Nan Yin ◽  
Dae-Whan Kim ◽  
Ji-Yeon Park ◽  
...  
Keyword(s):  
Normal Distribution ◽  
Rupture Life ◽  
Reliability Assessment ◽  
Creep Rupture ◽  
Interference Model ◽  
Service Temperature ◽  
Z Parameter ◽  
Rupture Data ◽  
Fluctuation Amplitude ◽  
Higher Temperature

This paper focuses on reliability assessment of creep rupture life under the service conditions at high temperatures and stresses for Gr. 91 steel which is considered as one of the prime structural materials for next-generation nuclear reactors. An interference model based on Z parameter, which is considered for the fluctuations of both service temperature and stress besides the scattering of rupture data, was analyzed and used to assess the reliability on creep rupture life of Gr. 91 steel. The scattering distribution of the creep rupture data of the Gr. 91 steel was investigated by using the Z parameter. It appeared that the Z parameter of creep rupture data for Gr.91 steel exhibited normal distribution. Using the normal distribution, a Monte-Carlo simulation (MCS) was carried out to generate a number of random variables for Zs and Zcr, and the reliability of the creep rupture life under the fluctuations of service temperature and stress conditions was estimated by using the interference model. It showed that the value of reliability decreased with increasing service time. Higher temperature caused the trend of faster deterioration. The value of reliability decreased rapidly at higher temperature fluctuation amplitude, and the reliability decreased as the scattering of the creep rupture data became serious.

Small Punch Testing and Its Modeling for the Evaluation of Mechanical Properties of Heat-Resistant Steels

2009 ◽  
Author(s):  
Petr Dyma´cˇek ◽  
Karel Milicˇka
Keyword(s):  
Material Properties ◽  
Power Plants ◽  
Residual Life ◽  
Tensile Tests ◽  
Constant Load ◽  
Material Behavior ◽  
Small Punch ◽  
Heat Resistant ◽  
Wide Range ◽  
Heat Resistant Steels

Small punch tests on miniaturized thin discs (SPT) can be considered as one of the promising methods predominantly for an assessment of the residual life of parts in service of power plants and thermal facilities. These tests can be used for determining a number of material properties. Two variations of the test seem to have a good potential for use in wide range of temperatures. The CF test (constant force) is a test in which the puncher penetrates under constant load and the time dependence of the deflection is measured. This test is similar to a conventional creep test. The CDR test (with constant deflection rate conditions), in which the puncher penetrates through the disc at a given constant rate of deflection (i.e., central deflection measured in a direction perpendicular to the disc) and the necessary force is measured. This mode of the tests can serve similarly as conventional tensile tests for determining of the static material properties, the estimation of fracture toughness and transitions in material behavior. The article summarizes the capabilities of the small punch technique and presents results from testing of two heat resistant steels, i.e., CSN 15313 and P91 used in the Czech power industry. Experimental results are compared with finite element modeling.

Creep Rupture Properties of Welded Joints of Heat Resistant Steels

2007 ◽  
pp. 1044-1048 ◽  
Author(s):  
Masayoshi Yamazaki ◽  
Takashi Watanabe ◽  
Hiromichi Hongo ◽  
Masaaki Tabuchi
Keyword(s):  
Welded Joints ◽  
Creep Rupture ◽  
Heat Resistant ◽  
Heat Resistant Steels ◽  
Rupture Properties

Guidelines to the Assessment of Creep Rupture Reliability for 316SS Using the Larson-Miller Time-Temperature Parameter Model

2017 ◽  
Author(s):  
Christopher Ramirez ◽  
Mohammad Shafinul Haque ◽  
Calvin Maurice Stewart
Keyword(s):  
Thermomechanical Processing ◽  
Rupture Life ◽  
Creep Rupture ◽  
Statistical Uncertainty ◽  
Rupture Data ◽  
Temperature Parameter ◽  
Long Life ◽  
Lower Temperature ◽  
Term Creep

It is common practice to perform accelerated creep testing (ACT) using time-temperature parameter (TTP) models. The TTP models are calibrated to creep-rupture data at high temperature and/or stress and extrapolate to lower temperature and/or stress where data is not available. The long-term creep rupture behavior (at low temperature and stress) is often not available due to the quantity, duration, and cost of testing. A limited scope of creep-rupture data is often analyzed using the TTP models. When conducting long-term extrapolation, statistical uncertainty becomes an issue. The ability of the TTP models to accurately predict creep-rupture at long life is often limited and the inherent material properties can dramatically influence creep-rupture life. Unfortunately, there is no consensus on the statistic for assessing the quality of TTP extrapolation. This study demonstrates methodology to assessing the uncertainty in creep rupture predictions for 316SS using the Larson Miller parameter. Over 2,000 creep-rupture data points are collected and digitized from the NIMS, ASM, MAPTIS, and ORNL databases; metadata such as the material’s form, thermomechanical processing, and chemical composition are recorded. Statistical uncertainty is measured using the “Z parameter”, which describes the deviation of creep-rupture data to a TTP model. The ability of the TTP models to extrapolate to long life is analyzed via exclusion of data. This is accomplished by: excluding 50% of the data, and by excluding the longest 10% of the data. It is shown that culling data in any way produces more conservative creep rupture predictions. The spread of the dataset will also affect the width of the reliability bands.

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