Experimental analysis of vibration and sound in order to investigate chatter phenomenon in cold strip rolling

Chatter is one of the most destructive types of vibration which usually occurs in cold strip rolling at high speeds. There is a minimum critical speed at which chatter mechanism may activate. Once the chatter has occurred, mill vibration is then become unstable. Its distinct sound is the most important sign for operators in order to identify chatter. As soon as chatter happens, the mill and its huge foundation vibrate with a sound as a mobile phone vibration. In these conditions, the only way to avoid hazardous damages is to reduce the rolling speed immediately. This paper is an application of sound analysis for solving chatter problem in cold strip rolling which is supported by experimental data. The results showed that upper housing and backup roll, compared with other parts, are more sensitive to chatter and more appropriate for installation of chatter detection sensors. Frequency analysis of recorded signals showed that at the time of chatter occurrence, dominant frequency in vibration signals of all parts of the stand and sound signal is equal. This frequency is in the range of third-octave chatter. It was also found that from the beginning of acceleration growth to hearing the chatter sound lasts less than 200 μs. Therefore, in the absence of automatic chatter detection systems, chatter sound is the best strategy for detecting and preventing the chatter.