Ratcheting assessment of low yield point steel BLY160: Experimental analysis and constitutive modelling

Abstract In this study, the ratcheting behaviour of low-yield-point steel BLY160 is evaluated via experimental investigation and constitutive modelling. A set of uniaxial asymmetrical cyclic loading tests in the strain- and stress-controlled modes is conducted to analyse the ratcheting response and stress relaxation, respectively. The effect of cyclic hardening and dependence on loading path are discussed to characterize the ratcheting behaviour. BLY160 steel is observed to exhibit a multi-stage evolution of ratcheting response with a significant cyclic hardening effect. However, the traditional Chaboche model calibrated according to the symmetric cyclic straining tests is observed to overestimate the cyclic hardening when predicting ratcheting, and might lead to an elastic shakedown under asymmetric cyclic stressing simulation. To overcome this disadvantage, a modified model based on the combined hardening rule is proposed; which introduces a new internal variable to distinguish the strain hardening under different loading paths. Hence, the interaction between the cyclic hardening and ratcheting behaviour can be accurately described. The accuracy of the modified model is validated by the close agreement between the simulation results and the experimental responses. The results verify that the proposed model is capable of simulating cyclical hardening, ratcheting, and stress relaxation behaviours for the test cases.