Measurement and modelling of Bauschinger effect for low-level plastic strains on AISI 4140 steel

This paper presents a new model for reproducing the elasto-plastic behavior of metals characterized by the presence of Bauschinger effect, taking as reference the case of autofrettaged cylinders. The paper is composed of an experimental part and of a numerical part. The experimental part consists of a set of tension-compression tests performed on AISI 4140 investigating the level of plastic strains typical of autofrettage: experiment arrangement, load cycles, measurement procedure and relevant results are presented. In the numerical part a multiaxial elasto-plastic model, derived from a combination of non-linear Kinematic hardening and non-linear Isotropic softening, is formulated and the key points for implementing it in a commercial Finite Element code are discussed. Then a fitting procedure for model parameters is proposed for reproducing the results obtained in experimental part. In the end the model has been implemented in ANSYS software and an example of application is presented for the case of an autofrettaged cylinder.