On the Characteristics and Mechanism of Rolling Instability and Chatter

Abstract

A nonlinear model describing the dynamical interaction between work rolls and metal sheets and the initiation of fifth octave rolling chatter is presented. The model, which comprises a work roll sub-model and a metal sheet roll-bite sub-model, enables the instability of strip rolling to be qualitatively and quantitatively studied as a function of rollstack stiffness, rolling speed, inter-stand tension, roll-bite entry and exit thickness, and the sheet force resulted from the interactive action of the work roll with the plastic deformation of the rolled strip. It is concluded that, even though the governing dynamics is highly nonlinear, rolling chatter instability is none other than mode excitation or beating, and thus linear. Analyzed results correspond well with what have been observed in physical rolling mills. Specifically, the natural frequency predicted for a 4-H rolling stand fits the fifth octave chatter at 550∼650 Hz and there is a critical rolling speed (2.54 m/sec for the material and sheet configurations considered in the paper) beyond which rolling instability will occur. This research establishes the fundamental knowledge base required for the understanding of chatter characteristics and mechanism, and thus provides the essential bases for effective control of rolling instability and chatter-free roll mill design.

Numerical and experimental analysis of the dynamic effects in compact cluster mills for cold rolling

“…These models include the static and dynamic components of the rolling force. Elastic contact among rolls was introduced according to Lin et al (2003) and conformingly to the theory of contact mechanics applied to the numerical methods by Wriggers (2006). The mechanical behaviour of rollers was studied and modelled according to Harris (2000) and to some preliminary experiences performed by SKF and documented in SKF (A).…”

“…Sometimes dynamic instability and chatter phenomenon occur. Chatter typologies have been classified by Lin et al (2003), while a comprehensive review of models was proposed by Yun et al (1998). Chatter is self-excited and arises in rolling operation as a consequence of the interaction between the structural dynamics of the mill stand and the dynamics of the rolling operation itself.…”

Mathematical Modelling of the High Frequency Vibrations During Cold Rolling Process

“…However, they may bring about the appearance of visible, lateral, alternately bright and dark strips on the surface of rolled metal plates with a constant λ scale amounting to about 30 [mm] specific for a certain type of rolling mills and process parameters. Roughness created this way may fluctuate between 3-30 µm [13][14][15][16][17][18][19][20]. Metal plates of this sort are perceived to be products of poor quality mainly due to the fact that the a.m. strips may show through the anti-corrosion and ornamental coatings.…”

“…They manifest long exposure time and fall into two intervals depending on vibration frequency mainly 125-256 HZ and 700-1000 HZ [6,7,9,[14][15][16][17][18][19][20][21][22].…”

Development of a Mathematical Model for the Prediction of Vibration in a Cold Rolling Mill Including the Driving System

“…Lin et al 4) presented an analytical model describing the dynamical interaction between work rolls and metal sheets and the initiation of a fifth-octave rolling chatter. The instability of rolling was studied as a function of rolling parameters using a work roll submodel and a metal sheet roll-bite submodel.…”