Experimental Study on Uniaxial Strain Cyclic Behavior of GS-20Mn5

Due to the common discontinuity of the structure and non-uniform load, local high stress phenomenon tends to appear in the mechanical structure under repeated loading, and even local small plastic deformation may occur. In this case, the cyclic elastic–plastic mechanical properties of the structural steel are the key elements for the reasonable and accurate assessment of structural safety. In order to study the cyclic mechanical properties of GS-20Mn5, which is a commonly used steel in load-bearing mechanical equipment, corresponding strain cyclic loading tests were performed. The cyclic elastoplastic deformation characteristics under strain-controlled cyclic loading with different strain ratios (R = −1,0.5) are studied, and the cyclic hardening/softening and mean stress relaxation features are revealed. The results show that the cyclic hardening/softening features are affected by the strain amplitude and cycles. This test material tends to show cyclic hardening at higher strain amplitudes. The cyclic stress–strain curve is obtained by the incremental step test, and the corresponding yield strength is about 4.8% larger than that under uniaxial tension. When R = 0.5, the test material exhibits obvious mean stress relaxation. When the strain amplitude is 0.16%, 0.30%, and 0.40%, the mean stress decreases and then stabilizes at about 25 MPa, −3 MPa, and −6 MPa, respectively. For the mechanical equipment made of GS-20Mn5 with local small plastic deformation under cyclic loading, the obtained cyclic mechanical performance of GS-20Mn5 can provide a reference for the analysis and evaluation of the structural safety.