減肉を有する炭素鋼配管の繰返し変形特性評価

-内圧負荷の影響-

抄録

Fitness-For-Service (FFS) assessment is a quantitative engineering approach that is used to determine the equipment with a flaw or damage is fit to continue operation. It can be used to make run-repair-replace decisions to help determine if pressured equipment containing flaw can continue to operate safety for some desired future period.
This paper provides a FFS assessment method on carbon steel pipe which contained a LTA (Local Thin Area) against seismic load and internal pressure load by FEM (Finite Element Method) analysis. Abaqus Ver. 6. 14, which provides the combined isotropic⁄kinematic hardening model, is used to simulate the LTA contained carbon steel pipe against seismic load and internal pressure load. Material parameters in the hardening model are identified by a symmetric strain cycle experiment based on ASTM E606. Isotropic hardening component is introduced by specifying the equivalent stress defining the size of the yield surface, as a tabular function of the equivalent plastic strain. Kinematic hardening component is obtained from the stabilized cycle of a specimen that is subjected to symmetric stain cycles.
The authors calculated up to 100 cycles on carbon steel pipe which contained a Local Thin Area against seismic load and internal pressure at room temperature. The results comparison between FEM analysis and experiment shows that delta-strain for one cycle and number of cycles to failure is predicted accurately. Safety margin of ratcheting assessment also was discussed in this paper.