To investigate the cyclic hardening and softening behavior of SN490B steel, constant axial strain amplitude cyclic loading tests were conducted using round bar specimens with strain amplitudes ranging from 0.25% to 13.5% for fully reversed loading. The following results were obtained. When the strain amplitude is smaller than 0.50%, cyclic softening behavior is observed, and when the strain amplitude is larger than this, cyclic hardening behavior is observed. Cyclic hardening and softening behavior can be explained by the expansion and contraction of the elastic range. The expansion and contraction of the elastic range depends on the strain amplitude.
