Uniaxial and biaxial ratcheting behavior of pressurized AISI 316L pipe under cyclic loading: Experiment and simulation

Abstract

Ratcheting defined as the progressive accumulation of plastic strain occurring during cyclic loading in the presence of the mean stress is one of the most prevalent failure modes in engineering structures. Experimental studies were conducted to characterize the uniaxial and biaxial ratcheting responses of an AISI 316L pipe. Experimental results show that an obvious cyclic hardening occurs in the AISI 316L pipe under uniaxial strain loading. Uniaxial ratcheting rate obtained from the axial cyclic experiment reaches a quasi-steady rate after a certain number of loading cycles. Moreover, using a designed four-point bending experimental setup, different axial stress amplitudes in the presence of the constant hoop stress were considered to characterize the biaxial ratcheting response of the material. The ratcheting strain and ratcheting strain rate in the hoop direction increase with increasing axial stress amplitudes under the constant hoop stress. To simulate the uniaxial and biaxial ratcheting behavior of the AISI 316L pipe, the Chaboche nonlinear kinematic hardening model was used. Using the Particle Swarm Optimization (PSO) technique, parameters of the Chaboche model were identified efficiently from the monotonic response of a cold-worked sample. The elastic limit of the material was measured using a very careful quasi-static cyclic compression experiment. The procedure to calibrate the material parameters for the Chaboche model and finite element simulation results were validated well with experimental data for the AISI 316L pipe. It is shown that the Chaboche model with the suitably-calibrated parameters from the experimental study can be applied to rigorously predict the ratcheting behavior of the AISI 316L pipe under cyclic uniaxial and biaxial loading conditions.