• Journal of Welding and Joining
• /
• v.32 no.1
• /
• pp.71-78
• /
• 2014

Although the fatigue design curve of ASME Code has enough margin with respect to alternating stress and cycles, the welding residual stress(WRS) should be included in fatigue analysis. In this paper, WRS distribution in a nozzle with dissimilar metal weldment was obtained by finite element analysis and was added in fatigue analysis. The fatigue analysis was performed by following the ASME Code including thermal and stress analysis applying with postulated 30 transient conditions. The calculated results of a cumulative fatigue usage factors(CUF) were compared for the case of the models with or without WRS effects. The results showed that the CUF at weldment and heat affected zone was affected by the WRS.

• Journal of the Korean Society of Safety
• /
• v.25 no.6
• /
• pp.53-59
• /
• 2010

A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

• Journal of the Korean Society of Safety
• /
• v.21 no.6 s.78
• /
• pp.20-25
• /
• 2006

In the design of class 1 components to apply ASME code section III NB, a fatigue is considered as one of the important failure mechanisms. Fatigue analysis procedure and standard fatigue design curve(S-N curve) is suggested in ASME code, which had to be performed to meet the integrity of components at the design step. As the plant life extension for operating power plants and the long-lived plant design, however, are being progressed, the fact which the existing ASME fatigue design curve can not consider fatigue effects sufficiently comes to the fore. To find the technical solution for these problems, a number of researches and discussion are continued up to now. In this study, the detailed fatigue analyses using the 3 dimensional modeling for the fatigue-weakened components were performed to develop the optimized fatigue analysis procedure and their results are compared with other reference solutions.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.581-584
• /
• 2005

A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The objectives of this paper are to systematize data processing of transition temperature, investigate its effects on fatigue life of DH pipes and optimization for size of DH pipes. A relational database management system as well as reliable fatigue life evaluation procedures is established for Korean DH pipes. Also, since the prototypal evaluation results satisfied both cycle-based and stress-based fatigue criteria. Through the optimum design process, the cross section diminished 18.64% and the CUF diminished 23.35%. So, it can be used as useful information in the future for optimal design, operation and energy saving via setting of efficient condition and stabilization of water temperature.