Experimental and Numerical Investigations of the Effects Associated to Complex Loading Combinations

Abstract

The paper presents experimental results concerning evaluation of an influence of cyclic torsion on stress variations during monotonic deformation carried out on the X10CrMoVNb9-1 steel. All strain controlled tests were performed at room temperature using thin-walled tubular specimens. The experimental programme contained selected combinations of monotonic and cyclic loadings, i.e. the torsion-reverse-torsion cycles were superimposed on the monotonic tension. It is shown that such cycles associated with monotonic tension caused essential variations of tensile stress. A significant decrease of the axial stress was visible. A single specimen method for yield surface determination was used to evaluate variations of yield point at different combinations of tension and torsion. The yield surface concept was also used to check permanency of the stress reduction during tension assisted by cyclic torsion. The effects observed during monotonic and cyclic loading combinations were theoretically described using the Maciejewski-Mroz model. It enabled to predict kinematic and isotropic softening or hardening of the material in question. The results exhibited that the model can be used successfully to simulate material behaviour during various combinations of monotonic and cyclic loadings.