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چكيده انگليسي :

AbstractKnowing the identity of self excited vibrations chatter in cold strip rolling lines andstudying the factors that can arise them has consistently been one of the important aimsof rolling technology researchers In this research single stand to five stand models ofchatter with two high and four high structure models have been studied with developingthe models of chatter that had been created by preceding researchers in MATLAB andSIMULINK softwares Perhaps one of the distinguished points of this research incomparison with other similar researcher s is using of numerous models for chatter In most references that have been used in this research it has been stated that identity andarising factors of chatter phenomenon have not been distinguished clearly yet and itrequired further studies In any case as most of the references have classified chatter intothree groups which are torsional third octave mode and fifth octave mode chatter inorder to their occurring frequencies and have stated mechanisms for third octave modechatter which is the most dangerous type of the chatter in present research bysimulating the model matching negative damping and regeneration mechanisms it hasbeen tried to studying these proposal causes of third octave mode chatter In this way theregeneration effect that is occurred in tandem mill rolling lines was studied precisely One of the most important studies is done in this research was the analyzing of vibrationsand gaining the frequency content and the amplitude related to each frequency in eachgroup of vibrations in five stand four high model This study that for each three cases ofstability 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 forsection reduction distributions of strip between consecutive stands and gaining the criticalvelocity for appearance of chatter in each case After plotting the obtaining data thisstudy led to these conclusions that in the cases of equal section reduction and equalvertical force in stands the critical velocity of single stand model is bigger than its valuein two three four and five models A parameter that can state rising or falling state of vibration s amplitudes and their ratingof change in consecutive periods of time is obtained by curve fitting the maximumamplitude of vibrations with an exponential curve in the form of aebt and gaining theparameter b In this project with obtaining this fitting curve by MATLAB software andwith 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 eachother The effect of inter stand distances on critical velocity of chatter in single stand to five stand models of chatter with two and four high structure models and the effect of frictionfactor and the masses of the work rolls on two and four high five stand chatter model isalso studied Increasing the inter stand distance and friction factor and decreasing themass of the work roll cause critical velocity to be increased At the end in the sixth chapter with adding up results suggestions are presented forfuture works

فصيح فر، محمد

پيش بيني چتر باز توليد درقفسه هاي تاندم نورد سرد