Vibration characteristic analysis of twenty-high rolling mill with local defect on roll surface based on the time-varying contact stiffness

• Propose an edge contact model to evaluate the time-varying contact stiffness with local defect in roll.
• Effect of local defect on dynamics of a Sendzimir twenty-high roll mill is studied.
• The root mean square and the envelope spectrum are analyzed with different local defect sizes in roll.
• The power spectral entropy is used to indicate the propagation of roll local defect.

The local defect on the roll surface of twenty-high rolling mill is not only the main factor affecting the quality of steel strip but also generating abnormal vibration in rolling process. Local defects are usually very difficult to identify in the rolling process in real time, which is one of the existing difficult problems. The edge contact model is proposed to analyze the time-varying contact stiffness in the presence of roll marks based on the line-contact elastic contact. A Sendzimir twenty-high roll mill dynamic model is established to analyze the vibration characteristics by incorporating the proposed edge contact model. Agreement between the simulated results and the experiment results validates the effectiveness of the established model. Different sizes defects on the surface of the working roll are taken into consideration in analyzing the vibration characteristics. The results reveal the relationship between vibration characteristics and the roll marks, which provides a theoretical support for the identification of the roll marks defect.