scholarly journals The Investigation of the Fracture Behavior of a Chinese 9% Cr Steel Welded Joint under Creep-Fatigue Interactive Loading

2021 ◽  
Vol 11 (21) ◽  
pp. 9983
Author(s):  
Yuebing Li ◽  
Yuxuan Song ◽  
Pan Liu ◽  
Ting Jin
Keyword(s):  
Fracture Behavior ◽  
Welded Joint ◽  
Inelastic Strain ◽  
Cyclic Softening ◽  
Fracture Mechanisms ◽  
P92 Steel ◽  
Holding Period ◽  
Creep Fatigue ◽  
Softening Stage

To understand the premature-fracture mechanisms of long-term service damage of an advanced alloy’s (Chinese P92 steel) welded joint, the creep-fatigue (CF) experiments with holding times of 30, 120, 300, 600 and 900 s were individually performed at 923 K. The cyclic softening, inelastic-strain amplitudes and stress-relaxation behaviors were compared between welded and base-metal (BM) specimens. From the results, the failure stage of the welded specimens occupies 45% of the lifetime fraction, while it only takes up 20% of the lifetime fraction in BM specimens with short holding times (30 and 120 s). Furthermore, only two softening stages were observed for both kinds of CF specimens with long holding times. The absence of a third softening stage in longer-held specimens indicates that the processes of macroscopic-crack initiation, propagation and rupture were accelerated. Based on the observation of the fracture surfaces, the fracture mechanism shifted from fatigue-dominated damage to creep-fatigue interaction when the holding period was increased.

scholarly journals Creep-fatigue fracture behavior of dissimilar metal electron beam welded joint.

1987 ◽  
Vol 36 (410) ◽  
pp. 1239-1245
Author(s):  
Masakazu OKAZAKI ◽  
Yoshiharu MUTOH ◽  
Toshio YADA ◽  
Masao YAMAGUCHI
Keyword(s):  
Electron Beam ◽  
Fatigue Fracture ◽  
Fracture Behavior ◽  
Welded Joint ◽  
Dissimilar Metal ◽  
Creep Fatigue ◽  
Fatigue Fracture Behavior ◽  
Metal Electron

scholarly journals Nanoindentation Characterization of Creep-fatigue Interaction on Local Creep Behavior of P92 Steel Welded Joint

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Yuxuan Song ◽  
Yi Ma ◽  
Zhouxin Pan ◽  
Yuebing Li ◽  
Taihua Zhang ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Creep Strength ◽  
Nuclear Power ◽  
Power Plants ◽  
Welded Joint ◽  
Secondary Creep ◽  
P92 Steel ◽  
Start Up ◽  
Creep Fatigue

AbstractIn modern fossil and nuclear power plants, the components are subjected to creep, fatigue, and creep-fatigue (CF) due to frequent start-up and shut-down operations at high temperatures. The CF interaction on the in-service P92 steel welded joint was investigated by strain-controlled CF tests with different dwell times of 30, 120, 300, 600 and 900 s at 650 °C. Based on the observations of the fracture surface by scanning electron microscope (SEM), the characteristic microstructure of fatigue-induced damage was found for the CF specimens with short dwell times (30 and 120 s). The hardness, elastic modulus and creep deformation near the fracture edges of four typical CF specimens with 30, 120, 600 and 900 s dwell times were measured by nanoindentation. Compared to specimens with post-weld heat treatment (PWHT), lower hardness and creep strength were found for all CF specimens. In addition, significant reductions in hardness, elastic modulus, and creep strength were measured near the fracture edges for the CF specimens with short dwell times compared to the PWHT specimens. Compared to PWHT specimens (0.007), the increased strain rate sensitivities (SRS) of 0.010 to 0.17 were estimated from secondary creep. The increased values of SRS indicate that the room temperature creeps behavior is strongly affected by the decrease in dislocation density after the CF tests.

Creep-Fatigue Life Determination of Grade 91 Steel Using a Strain-Range Separation Method

2009 ◽  
Author(s):  
Wolfgang Hoffelner
Keyword(s):  
Stress Rupture ◽  
Strain Range ◽  
Inelastic Strain ◽  
Fatigue Curve ◽  
Cyclic Softening ◽  
Least Square ◽  
Creep Failure ◽  
Creep Fatigue ◽  
Grade 91 ◽  
Grade 91 Steel

The method of strain range partitioning developed by Manson offers a possibility for treatment of creep-fatigue interactions. It partitions the strain-range of a complex hysteresis loop into four elementary strain range types. Although the method has its merits it is difficult to apply because of lacking experimental data and difficult loop reconstructions. The paper describes an approach which separates the inelastic strain range only into a fatigue portion and a creep portion following both a power law Coffin-Manson relationship. Coefficients and exponents were determined by a simple least square fitting procedure from a set of literature data. The plastic part agreed very well with the experimentally determined fatigue curve. The creep part could, however, only be understood using fatigue-modified stress rupture data accounting for cyclic softening. With this approach it was possible to determine number of cycles to creep failure as a function of the pure creep strain range. This procedure was applied to a set of literature data of grade 91 steel which covered a temperature range of 500°C, 550°C, 600°C with stress controlled and strain controlled hold-times. Life-times were predicted in a range corresponding with the scatter of pure fatigue or creep curves, which means that a very good agreement was obtained. The paper will give a thorough description of the procedure and demonstrate its applicability to design codes.

High Temperature Creep-Fatigue Design and Service Experience

2008 ◽  
Vol 1125 ◽  
Author(s):  
A-A. F. Tavassoli ◽  
B. Fournier ◽  
M. Sauzay
Keyword(s):  
High Temperature ◽  
Austenitic Stainless Steels ◽  
Oxide Dispersion Strengthened ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Oxide Dispersion ◽  
Martensitic Steels ◽  
Fatigue Design ◽  
Creep Fatigue

ABSTRACTGeneration IV fission and future fusion reactors envisage development of more efficient high temperature concepts where materials performances under creep-fatigue hold the key to success. This paper presents extended experimental results obtained from creep, fatigue and creep-fatigue tests on the main structural materials retained for these concepts, namely: stainless steel type 316L(N), the conventional Modified 9Cr-1Mo martensitic steel and its low activation derivatives such as Eurofer steel, and their more advanced grades strengthened by oxide dispersion. It shows that the existing recommendations made in design codes adequately cover individual damage due to creep or fatigue but often fall short under combined creep-fatigue interaction. This is partly due to the difficulties of reproducing service conditions in laboratory. In this paper, results from tests performed on components removed from reactor, after long service, are used to refine code recommendations.Using the above combined assessment, it is concluded that there is good confidence in predicting creep-fatigue damage for austenitic stainless steels. For the martensitic steels the effects of cyclic softening and microstructure coarsening throughout the fatigue life need more consideration in creep-fatigue recommendation. In the long-term development of ferritic/martensitic oxide dispersion strengthened grades with stable microstructure and no cyclic softening, appears promising provided problems associated with their fabrication and embrittlement are resolved.

Progress in Developing Constitutive Equations for Inelastic Design Analysis

1983 ◽  
Vol 105 (3) ◽  
pp. 273-276 ◽  
Author(s):  
C. E. Pugh
Keyword(s):  
Constitutive Equations ◽  
Inelastic Strain ◽  
Short Term ◽  
Inelastic Material ◽  
Fast Breeder Reactors ◽  
Breeder Reactors ◽  
Term Creep ◽  
Inelastic Design ◽  
Creep Deformations

A summary is given of the constitutive equations that have been developed for use in design assessments of elevated temperature components of liquid metal fast breeder reactors. The discussion addresses representations of short-term (plastic) and long-term (creep) inelastic material responses. Attention is given to improved representations of the interactions between plastic and creep deformations. Most of the discussion is in terms of constitutive equations that make use of the concept of separating the total strain into elastic, plastic, and creep portions. Additionally, some discussion is given of progress being made toward establishing design equations based on unified measures of inelastic strain that do not distinguish different strain portions.

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.

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