Findings on Creep-Fatigue Damage in Pressure Parts of Long-Term Service-Exposed Thermal Power Plants

1985 ◽  
Vol 107 (3) ◽  
pp. 260-270 ◽  
Author(s):  
F. Masuyama ◽  
K. Setoguchi ◽  
H. Haneda ◽  
F. Nanjo
Keyword(s):  
Fatigue Damage ◽  
Power Plants ◽  
Thermal Power ◽  
Field Experiences ◽  
Creep Damage ◽  
Thermal Power Plants ◽  
Damage Analysis ◽  
Creep Fatigue ◽  
Fatigue Damage Analysis

The increase of long-term service exposure to thermal power plants, the tendency toward intermediate and cyclic operation to meet the change in electric power demand and supply situation, and the requirement to develop higher-temperature and higher-pressure plants have led to increasing attention towards the reliability improvement. This paper presents findings from field experiences of cracking or failure and two types of damage analyses—(1) creep-fatigue damage analysis based on the life fraction rule and (2) metallurgical damage analysis—of boiler pressure parts that have been exposed to long-term elevated temperature service. The field experiences are (1) cracking or failure of thick-walled Type 316 stainless steel pressure parts in the main steam line of an ultra-supercritical thermal power plant and (2) dissimilar metal weld joints for boiler tubing. The creep-fatigue damage analysis of these pressure parts showed a reasonable correspondence with the field experience. According to the creep-fatigue damage analysis and the metallurgical damage analysis, most of damage was restrained creep mode phenomenon without deformation. The creep damage was composed of metallurgical damage and mechanical damage such as microvoids and structural defects. One method of simulating field experienced creep damage was proposed and performed. As a result, the process of creep voids being generated and growing into cracks without deformation was successfully observed. Also a review of the current status of nondestructive detecting methods of creep damage suggests that detecting the creep voids metallurgically is more practical at the present time than doing so analyzing the changes in physical properties of the material. It is also suggested that, in the metallurgical approach, detecting the creep voids and cracks by replica method and anlayzing precipitates for evaluation of material deterioration by precipitate extraction method will make it possible to successfully address the problem of plant equipment creep damage evaluation and life prediction.

Design of Lateral Tee for Steam Pipe in Power Plants

2015 ◽  
Author(s):  
Hyeon Su Kim ◽  
Sehwan Jeong ◽  
Dong Ju Lee ◽  
Ha Geun Kim ◽  
Sang Beom Shin
Keyword(s):  
Power Plants ◽  
High Stress ◽  
Local Failure ◽  
Design Criteria ◽  
Plastic Collapse ◽  
Damage Analysis ◽  
Service Temperature ◽  
Creep Fatigue ◽  
Fatigue Damage Analysis ◽  
Steam Pipe

The purpose of this study is to evaluate the design verification of the welded type 45° lateral tee for the steam pipe in power plants. For it, first, the stress analysis was carried out under design condition in accordance with ASME Sec. VIII Div. 2 in order to evaluate the possible occurrence of plastic collapse and local failure. And next, the creep-fatigue damage analysis was performed under the normal operating condition in accordance with ASME Sec. III Subsection NH considering the service temperature of 566°C. From the results, it was found that the welded type 45° lateral tee satisfies the design criteria corresponding to the plastic collapse and the local failure. However, it has a probability of creep rupture during the design life due to the high stress localized in the crotch region. Therefore, a welded type 90° lateral tee was also evaluated with the same analysis procedures to consider the influence of the geometry at the crotch region. Based on the results, the welded type 90° lateral tee satisfies the design criteria of the plastic collapse, local failure and the creep-fatigue strength. This result indicated that an optimal shape design of the crotch region shall be required in order to secure the creep strength of the welded type 45° lateral tee having high service temperature.

Grain Boundary Cracking of Nickel-Based Alloy 625 Under Creep Loadings at Elevated Temperatures

2019 ◽  
Author(s):  
Yan Liang ◽  
Yifan Luo ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Power Plants ◽  
Elevated Temperatures ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Alloy 625 ◽  
Creep Fatigue ◽  
Creep Loading ◽  
Initial Cracks

Abstract Since the operating condition of thermal power plants has become harsher for minimizing the emission of CO2, Ni-based superalloys, such as Alloy 617 and 625, have been used in the plants to replace the conventional ferritic materials. Unfortunately, the increase of coefficient of thermal expansion compared with conventional steels is a concern. In addition, Ni-based superalloys have to suffer creep-fatigue random loading because thermal power plants have to compensate the random output of various renewable energies. It was found that the lifetime of Ni-based superalloys under creep-fatigue loading was much shorter than that under simple fatigue or creep loading. Thus, it has become very important to clarify the crack mechanism and establish the quantitative theory for estimating their lifetime under various loading conditions at elevated temperatures. Thus, the elucidation of the initial damage mechanism of Alloy 625 under various loading is indispensable. Hence, the initial cracking mechanism of Alloy 625 at grain boundaries under creep loading was investigated experimentally. The creep test was applied to small specimens in Argon atmosphere. The change of the micro texture during the creep test was observed by using SEM. It was confirmed that all the initial cracks appeared at certain grain boundaries. The change of the crystallinity was observed by EBSD (Electron Back-Scatter Diffraction) analysis quantitatively. It was found that the local accumulation of dislocations at the cracked grain boundaries caused the initial cracks at those grain boundaries. The initiation of cracks appeared clearly between two grains which had difference of KAM (Kernel Average Misorientation) values larger than 0.2. Therefore, dislocations were accumulated at one side of the grain boundary. By measuring the KAM values near grain boundaries, the appearance of initial cracks can be predicted approximately.

A Method of Fatigue Damage Analysis for Sandwich Panels on Ship

2010 ◽  
Vol 452-453 ◽  
pp. 849-852
Author(s):  
Qi Chao Xue ◽  
Guang Ping Zou
Keyword(s):  
Fatigue Damage ◽  
Sandwich Structure ◽  
Sandwich Panels ◽  
Damage Analysis ◽  
Short Term ◽  
Stress Spectrum ◽  
Fatigue Damage Analysis ◽  
Distribution Of Stress ◽  
The Waves

A method of fatigue damage analysis for sandwich panels on ship is studied in this paper. When ship is navigating on the sea, the waves that ship encounters can be regarded as a stochastic process. And responses of ship movement can also be regarded as a series of stochastic spectrums. By using of finite element method, loads spectrums of inner ship structures in different sea conditions can be obtained. Then short term or long term distribution of stress range can be determined. Residual stiffness modal is used to describe the damage of sandwich panels under fatigue loads. And fatigue damage variable D is defined based on stiffness degration. An integral equation to calculate fatigue damage under loads spectrum is constructed to describe the damage of ship sandwich structure in long term and short term stress spectrum distributions.

Creep-Fatigue Damage Analysis of Solder Joints

2009 ◽  
pp. 1-1-21 ◽  
Author(s):  
SH Ju ◽  
S Kuskowski ◽  
BI Sandor ◽  
ME Plesha
Keyword(s):  
Fatigue Damage ◽  
Solder Joints ◽  
Damage Analysis ◽  
Creep Fatigue ◽  
Fatigue Damage Analysis

Studying the Metal from Drums at Thermal Power Plants after Long-Term Operation Using Subsize Charpy Specimens

2021 ◽  
Vol 68 (8) ◽  
pp. 640-646
Author(s):  
A. G. Rudenko ◽  
V. N. Voyevodin ◽  
S. V. Gozhenko ◽  
P. A. Mischenko
Keyword(s):  
Power Plants ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Term Operation
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