Types of mid-frequency vibrations appearing during the rolling mill operation

The paper presents the numerical analysis of vibrations with moderate frequencies excited during the milling process taking into account the transportation motion of the strip and its inertial properties. The model dynamics are described by the set of nonlinear equations which describe, respectively, the transverse and the vertical motion of the working rolls, under the assumption that n = 4 half-waves are formed along the strip section joining two neighboring rolling stands. It has been demonstrated that the following vibration types can take place, depending on the strip velocity: • the so-called 2T-periodic vibrations, which are a combination of self-excited and parametric vibrations; • vibrations which are qualified as “partly ordered” chaos, taking place at the boundary of the vibration initiation region; • classical chaos, considered as an indication of loss of stability; • 4T-periodic oscillations; • unstable vibrations.