356 Simplified Evaluation Guideline for Thermal Fatigue Damage Due To Random Fluctuation of Fluid Temperature

In nuclear reactors, piping components are susceptible to thermal fatigue damage. This is due to the fluid temperature change along these pipelines that can generate repeated thermal loads. One of these loads is thermal stratification. Thermal stratification generates an oscillating stratified layer, which induce cyclic thermal stresses leading to fatigue damage. To evaluate thermal fatigue by thermal stratification, a frequency response function for straight pipes was developed. However, this function cannot evaluate elbow pipes under thermal stratification. Here, thermal stress generates due to bending moment that is generated by the horizontal portion unlike straight pipes. Furthermore, the elbow pipe can give rise to stress intensifications which can affect the peak stress values within the elbow. To understand the stress generation mechanism, Finite element analyses were performed. The study focused on the effect the frequency of the fluid oscillation on the stress generation mechanism. Based on the clarified mechanism, the frequency response function was improved to correspond to the thermal stratification at elbow pipes. Applicability of this function was validated through agreement with finite element simulation.

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Assessment of thermal fatigue damage caused by local fluid temperature fluctuation (part II: crack growth under thermal stress)

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2013.12.042 ◽

2014 ◽

Vol 268 ◽

pp. 139-150 ◽

Cited By ~ 4

Author(s):

Masayuki Kamaya

Keyword(s):

Thermal Stress ◽

Crack Growth ◽

Fatigue Damage ◽

Thermal Fatigue ◽

Temperature Fluctuation ◽

Fluid Temperature

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3D Characterization of Thermal Fatigue Damage in Monofilament Reinforced Copper for Heat Sink Applications in Fusion Reactor Systems

Practical Metallography ◽

10.3139/147.110139 ◽

2012 ◽

Vol 49 (5) ◽

pp. 278-289

Author(s):

M. Schöbel ◽

H.P. Degischer ◽

A. Brendel ◽

B. Harrer ◽

M. Di Michiel

Keyword(s):

Fatigue Damage ◽

Thermal Fatigue ◽

Heat Sink ◽

Fusion Reactor

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Cumulative Thermal Fatigue Damage for Aluminum Alloy under Variable Stresses

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/454/1/012145 ◽

2018 ◽

Vol 454 ◽

pp. 012145

Author(s):

Mohammed J. Kadhim ◽

Hamza M. Kamal

Keyword(s):

Aluminum Alloy ◽

Fatigue Damage ◽

Thermal Fatigue ◽

Variable Stresses

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Thermal fatigue damage evaluation of a PWR NPP steam generator injection nozzle model subjected to thermal stratification phenomenon

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2010.12.003 ◽

2011 ◽

Vol 241 (3) ◽

pp. 672-680 ◽

Cited By ~ 4

Author(s):

Luiz Leite da Silva ◽

Tanius Rodrigues Mansur ◽

Carlos Alberto Cimini Junior

Keyword(s):

Fatigue Damage ◽

Steam Generator ◽

Thermal Fatigue ◽

Thermal Stratification ◽

Damage Evaluation ◽

Injection Nozzle

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Fatigue Crack Initiation and Growth Observation for 316 Stainless Steel Subjected to Equi-Biaxial Cyclic Loading

Volume 3: Design and Analysis ◽

10.1115/pvp2015-45814 ◽

2015 ◽

Cited By ~ 1

Author(s):

Satoshi Iida ◽

Shigeki Abe ◽

Takao Nakamura ◽

Masayuki Kamaya

Keyword(s):

Fatigue Crack ◽

Crack Growth ◽

Fatigue Damage ◽

Equivalent Stress ◽

Fatigue Crack Initiation ◽

Biaxial Stress ◽

Fluid Temperature ◽

Plant Design ◽

Cracking Behavior ◽

Thermal Transients

Fatigue accumulation is one of the ageing phenomena considered in the plant design and maintenance. The degree of fatigue damage is evaluated by cumulative usage factor using design fatigue curve, which is determined from results of uniaxial fatigue tests. The stress caused by thermal transients is generally equibiaxial, not uniaxial. Fluid temperature fluctuation due to changes in plant conditions, such as plant start-up and shutdown, is the primary cause of fatigue damage. For accurate fatigue damage evaluation, it is important to be conducted under equi-biaxial condition. In this study, pressurized disc fatigue test was conducted in order to simulate the cyclic equi-biaxial stress. In order to clarify how the crack initiates and grows under the equi-biaxial stress condition. Cracking behavior was examined by replica observation method. The crack growth rates were identified by the change in the crack length. It was shown that the fatigue crack growth rate under equi-biaxial stress was faster than that under uniaxial stress for the same equivalent stress intensify factor. It was concluded that the reduction in the fatigue life under equi-biaxial stress was brought about by the accelerated crack growth.

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