Modeling of a Long-Term Creep Curve of Alloy 617 for a High Temperature Gas-Cooled Reactor

2008 ◽  
Vol 385-387 ◽  
pp. 693-696 ◽  
Author(s):  
Woo Gon Kim ◽  
Song Nan Yin ◽  
Ik Hee Jung ◽  
Yong Wan Kim
Keyword(s):  
Least Square ◽  
Short Term ◽  
Creep Tests ◽  
Least Square Fitting ◽  
Creep Curves ◽  
Term Creep ◽  
Good Agreement ◽  
Short Term Creep ◽  
Stress Dependency

This study aimed to model the long-term creep curves above 105 hours by implementing a nonlinear least square fitting (NLSF) of the Kachanov-Rabotnov (K-R) model. For this purpose, the short-term creep curves obtained from a series of creep tests at 950oC were used. In the NLSF of their full creep curves, the K-R model represented a poor match to the experimental curves, but the modified K-R one revealed a good agreement to them. The Monkman-Grant (M-G) strain represented the behavior of a stress dependency, but the 􀁏 parameter was constant with a stress independency. The 􀁏 value in the modified K-R model was 2.78. Long-term creep curves above 105 hours from short-term creep data were modeled by the modified K-R model.

Long-Term Creep Modeling of Modified 9Cr-1Mo Steel for a Sodium Cooled Fast Reactor

2010 ◽  
Author(s):  
Woo-Gon Kim ◽  
Jae-Young Park ◽  
Sung-Ho Kim ◽  
Chan-Bock Lee
Keyword(s):  
Constant Load ◽  
Primary Creep ◽  
Least Square ◽  
Creep Data ◽  
Creep Tests ◽  
Omega Method ◽  
Creep Curves ◽  
The Individual ◽  
Term Creep

This paper focused on long-term creep modeling for describing total creep curves of up to rupture for modified 9Cr-1Mo steel (G91). Creep data was obtained by a series of constant-load creep tests at 600°C. Three modified constitutive equations of modified power-law method (MPM), modified theta method (MTM) and modified omega method (MOM), described as a sum of a decaying primary creep and an accelerating tertiary creep, were proposed. A nonlinear least square fitting (NLSF) analysis was carried out on the basis of the creep data so that they provide the best fit to experimental data in optimizing parameter constants of the individual equation. Results of the NLSF analysis showed that in the lower stress regions of 160MPa (σ/σys<0.65), the MTM matched well with the experimental creep data compared with the MPM and MOM, but that in the higher stress regions of 160MPa (σ/σy > 0.65), the MPM revealed better agreement than the MTM and MOM. It was found that the MTM was superior in the modeling of long-term creep curves to the MPM and MOM. Long-term creep curves for the G91 steel were numerically modeled and its creep life was predicted by the MTM.

Prediction of Long Term Stress Rupture Data for 2124

2006 ◽  
Vol 519-521 ◽  
pp. 1041-1046 ◽  
Author(s):  
Brian Wilshire ◽  
H. Burt ◽  
N.P. Lavery
Keyword(s):  
Q Methodology ◽  
Fracture Behavior ◽  
Stress Rupture ◽  
Creep Data ◽  
Short Term ◽  
Rupture Data ◽  
Term Creep ◽  
Term Data ◽  
Short Term Creep

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.

Short-Term Creep Data Based Long-Term Creep Life Predictability for Grade 92 Steels and Its Microstructural Basis

2018 ◽  
Vol 25 (3) ◽  
pp. 713-722 ◽  
Author(s):  
Seen Chan Kim ◽  
Jae-Hyeok Shim ◽  
Woo-Sang Jung ◽  
Yoon Suk Choi
Keyword(s):  
Creep Data ◽  
Creep Life ◽  
Short Term ◽  
Term Creep ◽  
Short Term Creep

scholarly journals New Numerical Analysis Method for Creep Lifetime of Gas Turbine Materials by Using the Discrete Cosine Transform

2020 ◽  
Author(s):  
Hideo Hiraguchi
Keyword(s):  
Discrete Cosine Transform ◽  
Creep Curve ◽  
Creep Data ◽  
Short Term ◽  
Cosine Transform ◽  
Discrete Signals ◽  
Creep Region ◽  
Term Creep ◽  
Short Term Creep

Abstract Recently the Discrete Cosine Transform[1], [2], [3] which is a modified Fourier Transform has begun to be used to express coefficients of creep equations using the power law or the exponential law such as Bailey-Norton law[4], [5] and θ Projection[6], [7], [8], [9], [10]. In addition, the Discrete Cosine Transform has begun to be used to express a creep equation itself. We have already found that the Discrete Cosine Transform can express the temperature and stress dependence property of the coefficients of the creep equations at the same time by the two-dimensional Discrete Cosine Transform using 8 × 8 discrete signals[11]. Furthermore, we have already found that the Discrete Cosine Transform can fit measured creep strain values very well from the primary creep region to the tertiary creep region using 8 discrete signals and it can estimate creep strain values between the measured points by interpolation very well[12]. However it has not been known if the Discrete Cosine Transform can predict the long term creep curve by using the short term creep data yet. Therefore, as a next stage, we tried to estimate the long term creep curve from the short term creep data of gas turbine materials by extrapolation using the Discrete Cosine Transform. As a result, we were able to obtain a useful numerical analysis method by utilizing the Discrete Cosine Transform Coefficients and others as a new extrapolation method. It is found that this new numerical method would be able to predict the configuration of 150,000-hour creep curve by using 500-hour to 13,000-hour short term creep data.

Long Term Creep Life Prediction of New and Service Exposed P91 Steel

2018 ◽  
Author(s):  
Muneeb Ejaz ◽  
Norhaida Ab Razak ◽  
Andrew Morris ◽  
Scott Lockyer ◽  
Catrin M. Davies
Keyword(s):  
Tensile Strength ◽  
Creep Behaviour ◽  
Equivalent Stress ◽  
Practical Reasons ◽  
Creep Data ◽  
Short Term ◽  
Creep Tests ◽  
High Temperature Components ◽  
Term Creep

P91 steels are widely used in high temperature components for power generation. Creep data is often generated through accelerated short term creep tests, for practical reasons, via increasing stress or temperature though this may alter the creep behaviour. Through normalising the creep test stress by tensile strength the Wilshire models reduce the batch to batch scatter in the creep data and enable the prediction of long term creep data from relatively short term test results. In this work it is shown that the Wilshire models fitted to uniaxial creep rupture data can be used to predict failure in both as cast and service exposed multiaxial tests. This is provided that the equivalent stress is the rupture controlling stress, as is the case for the P91 tests examined, and the tensile strength is measured as part of the test programme.

Predicting Collapse Times for Corrugated Boxes Under Constant Top Load Using Short-Term Creep Tests

2005 ◽  
Vol 33 (4) ◽  
pp. 11932
Author(s):  
DR Petersen ◽  
RE Link ◽  
G Burgess ◽  
SP Singh ◽  
M Srinangyam
Keyword(s):  
Short Term ◽  
Creep Tests ◽  
Term Creep ◽  
Short Term Creep

Basic Study on Creep Properties of Eucalyptus Wood

2014 ◽  
Vol 911 ◽  
pp. 232-237
Author(s):  
Yuan Rong Ma ◽  
Xian Jun Li ◽  
Biao Deng ◽  
Ying She Luo
Keyword(s):  
Model Parameters ◽  
Short Term ◽  
Basic Study ◽  
Burger Model ◽  
Creep Properties ◽  
Eucalyptus Plantation ◽  
Moisture Contents ◽  
Creep Curves ◽  
Term Creep

The study tested the short-term bending creep curves of Eucalyptus Plantation Wood under different loads, moisture contents and temperatures, analyzed the influence of load, moisture content and temperature on creep of Eucalyptus. Guided by the rheological theory, the study adopted the Burger rheological model to do the curve fitting and solved the model parameters. A defect found from Burger model in simulating long-term creep properties of wood was preliminary discussed and remedied. The equivalence of creep test and relaxation one was discussed.

scholarly journals Microstructural Evolution and Short-Term Creep Rupture of the Simulated HAZ in T92 Steel Normalized at Different Temperatures

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1310 ◽  
Author(s):  
Tai-Jung Wu ◽  
Chien-Chun Liao ◽  
Tai-Cheng Chen ◽  
Ren-Kae Shiue ◽  
Leu-Wen Tsay
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Creep Rupture ◽  
Infrared Heating ◽  
Short Term ◽  
Creep Tests ◽  
Steel Tubes ◽  
Austenite Grain ◽  
Term Creep ◽  
Short Term Creep

T92 steel tubes have been widely applied in advanced supercritical boilers to replace Gr.91 tubes. Simulated samples with microstructures similar to those present in the heat-affected zone (HAZ) of a T92 steel weld were subjected to short-term creep tests in the study. T92 steel tubes were normalized at either 1213 K (L) or 1333 K (H) for 1 h, followed by tempering (T) at 1033 K for 2 h. After the normalizing and tempering treatments, the HT samples comprised finer precipitates but in greater numbers along the prior austenite grain boundaries (PAGBs) and martensite lath boundaries, as compared with those of the LT samples. The HAZ microstructures in the T92 steel welds were simulated by using an infrared heating system, which included over-tempering (OT, below AC1) and partial transformation (PT, slightly below AC3) zones. Martensite laths in the OT sample were more likely to be replaced by numerous cellular structures or subgrains together with spherodized carbides mainly located at the lath and austenite grain boundaries. Furthermore, coarser but fewer carbides were found along the refined lath and grain boundaries in the PT samples, in comparison with other samples in each group. Short-term creep tests showed that the PT samples were more likely to fracture than other samples in each group. Moreover, under the same testing conditions, the microstructures of T92 steel were more stable and resistant to degradation than those of T91 steel after welding or loading at elevated temperatures. Such events were responsible for higher creep resistance of the simulated T92 samples than that of the simulated T91 samples under the same creep-rupture conditions.

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