In nuclear power plants, a lot of failure cases by high cycle thermal fatigue have been reported, which is induced by temperature fluctuation of the coolant. To ensure the safety of the nuclear power plants, the thermal fatigue failure should be prevented adequately. Thus The Japan Society of Mechanical Engineers (JSME) published the high cycle thermal fatigue evaluation guideline. In the guideline, it is proposed that the structural integrity can be judged by the location of thermal stratification, which...
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Study on the mechanism of stress generation of straight pipe and elbow pipe which has thermal stratification

Thermal fatigue failure and vibration fatigue failure occur frequently in spite of well known. Because they are complicated multi-physics phenomena. Furthermore, there are many influence factors in both of loadings and strength. For design, conservative evaluation methods were applied to both loadings and strength. However, best estimation with uncertainty evaluation are suitable for trouble shootings and risk analyses. To satisfy above requirements, authors propose a total evaluation of loadings and s...
英字タイトル:
Total evaluation of loadings and strength for fatigue damage prediction

In recent years, reports have increased about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the reasons of the cases is a turbulent mixing at a Tee -junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers published the guideline which is an evaluation method of high cycle thermal fatigue damage at nuclear pipes. ...
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Comparison of Evaluation Results of Piping Thermal Fatigue EvaluationMethod based on Equivalent Stress Amplitude

Nuclear piping has various kinds of thermal fatigue failure modes. Main causes of thermal loads are structural responses to fluid temperature changes during plant operation. These phenomena have complex mechanisms and so many patterns, that their problems still occur even though well-known issues. To prevent thermal fatigue due to above thermal loads, the JSME guideline is adopted. Both thermal load and fatigue failure mechanism have been investigated and summarized into the knowledgebase. Based on abo...
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Development of thermal fatigue evaluation methods of piping systems

Abstract Effect of loading history on the high cycle fatigue crack propagation behavior was experimentally studied in SUS 316 stainless steel, paying a special attention to an interaction between low-cycle thermo-mechanical fatigue loading and high cycle fatigue one in the fatigue crack propagation rates. The experimental results clearly demonstrat ed that the interaction was significant. It was shown that the stress ratio which was built-up under an influence of previous loading history made a major contr...
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Fatigue Crack Threshold Depending on Loading History.