The effect of the initial plastic deformation on the damping properties of low-carbon steel is experimentally studied, which corresponds to a change in the deformation diagram. The deformation diagram also refers to hysteresis loops that expand after the initial plastic deformation, called “plastic execution” in the work. When constructing hysteresis loops and recording damped oscillations, the amplitude values of loading cycles not exceeding 200 MPa are considered. Rods of rectangular box-shaped cross-section were used as samples. A description of static and dynamic laboratory installations that implement a pure bending scheme of the sample is given. Measurements are made by load cells with the fixation of counts in the computer memory with a frequency of 100 Hz. Cyclic symmetrical loads with a frequency of 2,62 Hz occur during oscillations in the sample. During the tests, the effect of a strong increase in hysteresis loops after the initial plastic deformation was reported to the sample was detected and quantitatively explored. The parameters of the loops are obtained depending on the value of the amplitude stress. The recorded graphs of decreasing amplitudes over time (up to 1000 periods) are in good agreement with the hysteresis loops obtained during static tests. The initial plastic deformation was also cyclic with deformation amplitudes 17% higher than the yield strength of the material. The effect of restoring the plastic deformation obtained by the sample after oscillations with stress amplitudes of 200 MPa was found. The oscillations cause the plastic deformation to be restored by more than 40%.