Experimental study on low cycle fatigue behavior of TWIP steel under cyclic shear loading condition

This study investigated the low-cycle fatigue (LCF) behavior of Twinning induced plasticity (TWIP) steel based on the twin bridge shear specimen and cyclic shear loading condition. The cyclic shear experiments were conducted with different strain amplitudes, and we compared their softening and hardening behaviors, cyclic stressstrain curves, and fatigue life. Through studying the crack morphology and the damage mechanism of shear specimens the role of cyclic shear stress on the damage evolution of TWIP under cyclic shear conditions was shown. The results indicate that the cyclic hardening and softening capacities of TWIP steel are highly affected by the strain amplitude. With increasing the load amplitude, the hardening rate increases, and its fatigue life is negatively correlated with the strain amplitude. Meanwhile, the hardening rate is positively correlated with the strain amplitude, and the softening rate is negatively correlated. The magnitude of strain amplitude affects the ratio of cyclic softening and cyclic hardening periods. Through analyzing the obtained microstructure characteristics, it is found that there is a high density of dislocations around the crack zone which causes the final failure of TWIP.