Knowing the identity of self-excited vibrations (chatter) in cold strip rolling lines and studying the factors that can arise them, has consistently been one of the important aims of rolling technology researchers. In this research, single-stand to five-stand models of chatter with two-high and four-high structure models have been studied with developing the models of chatter that had been created by preceding researchers in MATLAB and SIMULINK softwares. Perhaps one of the distinguished points of this research in comparison with other similar researcher’s, is using of numerous models for chatter. One of the most important studies is done in this research, was the analyzing of vibrations and gaining the frequency content and the amplitude related to each frequency in each group of vibrations in five-stand four-high model. This study that for each three cases of stability conditions (stable, critical and chatter) was performed by means of FFT analysis, led to findings and conclusions about inter-stand relationships in each case. One another studies done in this research, performed by considering four cases for section reduction distributions of strip between consecutive stands and gaining the critical velocity for appearance of chatter in each case. After plotting the obtaining data, this study led to these conclusions that in the cases of equal section reduction and equal vertical force in stands, the critical velocity of single stand model is bigger than its value in two, three, four and five models. A parameter that can state rising or falling state of vibration’s amplitudes and their rating of change in consecutive periods of time, is obtained by curve fitting the maximum amplitude of vibrations with an exponential curveand gaining the parameter ‘b’. In this project with obtaining this fitting curve by MATLAB software and with using the parameter ‘a’ that is the ratio of the reduction of the i-th stand to its (i+1)-th value, along with the critical velocity versus ‘a’ are plotted and compared with each other. The effect of inter-stand distances on critical velocity of chatter and the effect of friction factor and the masses of the work rolls, on two and four-high five-stand chatter model is also studied. Increasing the inter-stand distance and friction factor and decreasing the mass of the work roll cause critical velocity to be increased. At the end, in the sixth chapter with adding up results, suggestions are presented for future works.
