ASME code and ratcheting in piping components. Final technical report
The main objective of this research is to develop an analysis program which can accurately simulate ratcheting in piping components subjected to seismic or other cyclic loads. Ratcheting is defined as the accumulation of deformation in structures and materials with cycles. This phenomenon has been demonstrated to cause failure to piping components (known as ratcheting-fatigue failure) and is yet to be understood clearly. The design and analysis methods in the ASME Boiler and Pressure Vessel Code for ratcheting of piping components are not well accepted by the practicing engineering community. This research project attempts to understand the ratcheting-fatigue failure mechanisms and improve analysis methods for ratcheting predictions. In the first step a state-of-the-art testing facility is developed for quasi-static cyclic and seismic testing of straight and elbow piping components. A systematic testing program to study ratcheting is developed. Some tests have already been performed an d the rest will be completed by summer'99. Significant progress has been made in the area of constitutive modeling. A number of sophisticated constitutive models have been evaluated in terms of their simulations for a broad class of ratcheting responses. From the knowledge gained from this evaluation study two improved models are developed. These models are demonstrated to have promise in simulating ratcheting responses in piping components. Hence, implementation of these improved models in widely used finite element programs, ANSYS and/or ABAQUS, is in progress. Upon achieving improved finite element programs for simulation of ratcheting, the ASME Code provisions for ratcheting of piping components will be reviewed and more rational methods will be suggested. Also, simplified analysis methods will be developed for operability studies of piping components and systems. Some of the future works will be performed under the auspices of the Center for Nuclear Power Plant Structures, Equipment and Piping. Proposals for future funding also will be submitted to different organizations and industries to speed up the progress of the research.
- Research Organization:
- North Carolina State Univ., Raleigh, NC (US)
- Sponsoring Organization:
- USDOE Assistant Secretary for Nuclear Energy, Washington, DC (US)
- DOE Contract Number:
- FG03-97NE21746
- OSTI ID:
- 355004
- Report Number(s):
- DOE/NE/21746-T1; ON: DE99003366; TRN: US0300703
- Resource Relation:
- Other Information: Supercedes report DE99003366; PBD: 14 May 1999; PBD: 14 May 1999
- Country of Publication:
- United States
- Language:
- English
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