Influence of Pre-strain on Very-Low-Cycle Stress–Strain Response and Springback Behavior

The influence of pre-strain on the very-low-cycle loading behavior as occurring, for example during roller leveling of sheet metals, is not yet fully understood. A key factor in this context is the stiffness of the material and its changes upon processing. To study the general mechanical property changes during low-cycle loading with small amplitudes for a wide variety of metals, sheet samples of mild steel DC01, pure copper CU-DHP and α-titanium are subjected to low-cycle tension–compression tests. The general influences of pre-strain and the applied strain amplitude are investigated regarding material hardening and changes in the elastic properties. It is shown that all tested materials feature changes in the Bauschinger behavior during cycling. The apparent elastic modulus of the materials decreases with increasing accumulated plastic strain, and the evolution depends on the strain amplitude and the pre-strain. For all three materials, changes in technical springback are present and depend on the loading history.