Rolling Mill Self-Vibration Diagnosis And Structure Dynamic Modification

Rolling mill chatter, a form of vibration, is a chronic problem in steel and aluminum rolling mills. It limits production, reduces product quality and increases maintenance cost. It is a common problem in hot strip mills especially when processing hard metals in obtaining thin and high-quality strips in a fast speed. However, as the strips move in a high speed with high pressing load, the mills start to vibrate with very high amplitude and, as in self-excited vibration, make patterns on the strips and the surfaces of rolls. Mill chatter goes with intense noise and deteriorates equipment condition. A consequent accident would result in tremendous loss and add extra cost to mill process.In the past, a large number of investigations have been carried out on rolling mill chatter around the world. Many researchers have attempted to explain these vibrations in both cold and hot strip mills. However, the mechanism of chatter vibration is still not fully understood, especially in hot strip mills, for reason of complexity in electromechanical system coupled with the rolling process. Due to the complex nature, the rolling mill charter problem is often termed as "ghost vibration" by many researchers.This thesis provides a systematic study on the chatter vibration of rolling mills. An approach for chatter vibration control based on the modification of structural dynamics of the feedback path is presented. It has been successfully applied to fifths finishing stand of hot rolling mill in TISCO. The research presented in this thesis consists of five parts. (1). Investigation of the basic chatter characteristics and chattermechanism based on field vibration test and vibration signal analysisof the rolling mill process. (2). Close-loop system identification and stability analysis of rolling mill...