Evaluation of Chaboche hardening model on the ratcheting behavior of carbon steel piping branch under seismic loading

In this study, the strain ratcheting behavior of piping branch under dynamic bending moments are evaluated. The Chaboche nonlinear kinematic hardening model is used to predict the plastic behavior of the piping branchs. The constant parameters of the hardening model and stress-strain data have been obtained from several stabilized cycles of specimens that are subjected to simulated seismic bending cycles. Both the FE and experimental results showed that the maximum strain ratcheting occurred on the flanks in the piping branch hoop stress direction just above the junction. The ratchetting strain rate increases with increase of the dynamic moment levels. The FE results show that initial rate of ratcheting is large and then it decreases with the increasing of loading cycles. The finite element results are compared with those obtained from experimental set-up. The FE hoop strain ratchetting data by using chaboche nonlinear kinematic hardening model comparing with the AF kinematic hardening model to be near that found experimentally values. With increase of the ratio diameter/thickness in branch pipes is observed that the onset of ratcheting occurred in the low moment leves. Keywords: Carbon Steel, Hardening Model, Piping Branch, Ratcheting.