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

2014 ◽  
Vol 268 ◽  
pp. 139-150 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Thermal Stress ◽  
Crack Growth ◽  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Fluid Temperature

Development of High Cycle Thermal Fatigue Evaluation Method Based on Time Interval of Peak-to-Peak of Fluid Temperature

2010 ◽  
Author(s):  
Nobuyuki Kimura ◽  
Jun Kobayashi ◽  
Hideki Kamide
Keyword(s):  
Thermal Stress ◽  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Evaluation Method ◽  
Frequency Characteristics ◽  
Time Interval ◽  
Fluid Temperature ◽  
Cycle Number ◽  
The Core ◽  
High Cycle Thermal Fatigue

Hot and cold fluids are mixed at the core outlet of sodium cooled fast reactors. The temperature fluctuation causes high cycle thermal fatigue in structural components. The temperature fluctuation at the core outlet region does not have always a sinusoidal waveform but a sharp edged waveform. The temperature shows intermittent and sudden decrease and recovery like a spike form. It is necessary to take into account the spiky waveform of temperature fluctuation for the construction of an evaluation method of the high cycle thermal fatigue. The conventional method uses the amplitude and cycle number of waves without reference to the frequency of temperature fluctuation. In this study, the time interval of each wave based on the rainflow method was applied to consider frequency characteristics against the conversion from fluid temperature to thermal stress in structure. The thermal stress obtained from the new method was compared to the results of FEM analysis. It was found that the consideration of frequency characteristics of waves could evaluate the fatigue damage in structure. Furthermore, the frequency characteristics of waves in this method were expressed as the unified curve independent of the velocity. Hereby the new evaluation method could evaluate the thermal fatigue in the reactor.

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

2015 ◽  
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.

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

2007 ◽  
Vol 2007 (0) ◽  
pp. 262-263
Author(s):  
Satoshi OKAJIMA ◽  
Kei HONDA ◽  
Shinsuke SAKAI ◽  
Satoshi IZUMI ◽  
Kunio OISHI ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Random Fluctuation ◽  
Fluid Temperature

Spectra Thermal Fatigue Tests Under Frequency Controlled Fluid Temperature Variation: Development of Test Equipment and Preliminary Tests

2004 ◽  
Author(s):  
Naoto Kasahara ◽  
Shinichi Hasebe ◽  
Sumio Kobaysashi ◽  
Masanori Ando ◽  
Nobuchika Kawasaki ◽  
...  
Keyword(s):  
Temperature Variation ◽  
Thermal Fatigue ◽  
Temperature Fluctuation ◽  
Evaluation Method ◽  
Mechanical Valve ◽  
Test Equipment ◽  
Frequency Effect ◽  
Measured Temperature ◽  
Fluid Temperature ◽  
Constant Flow Rate

High cycle thermal fatigue induced by fluid temperature fluctuation is one of the important issues in nuclear plants. JNC has proposed a fatigue evaluation method paying attention to temperature attenuation related with frequency of fluctuation. In order to clarify the frequency effect of fluid temperature fluctuation on the crack initiation and propagation, a sodium temperature controlled thermal fatigue test equipment (SPECTRA) was developed. This equipment is capable of preciously controlling sodium temperature variation under various frequencies with a constant flow rate. This performance was achieved by the control of electromagnetic pumps without mechanical valve operations. Specimens are long straight pipes where temperature fluctuation ranges gradually reduce from upstream to downstream. As preliminary tests, temperature measurement and fatigue experiments were conducted. Measured temperature was preciously controlled under various frequencies. Cracks were observed in upstream area of a specimen. From above results, capability of frequency controlled test by SPECTRA facility was confirmed.

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