Experimental Study on Mechanical Response of Q235 Steel Under Cyclic Stress Loading

The cyclic softening/hardening, ratcheting effect, and Bauschinger effect usually occur in the body structure of large mechanical equipment under cyclic loading. This manuscript focuses on Q235 steel commonly used in the welded frame of large mechanical equipment. The experiments were carried out with mean stress varying from −60 to 60 MPa and stress amplitude varying from 300 to 340 MPa, respectively, and the mechanical responses were analyzed comprehensively. The experimental results show that Q235 steel exhibits cyclic softening characteristics at positive mean stress and cyclic hardening characteristics at negative mean stress. The larger the stress amplitude or the absolute value of the mean stress, the greater the absolute value of ratcheting strain. At the same stress amplitude, when the absolute value of the mean stress is equal, the Bauschinger coefficient is almost equal. Based on the experimental results, the evolution formula of ratcheting strain is established by a phenomenological method.