Characterization of dynamic instability in metal sheet rolling /
The present status of thin sheet rolling and processing in industry is that progress made regarding rolling chatter analyses is incomplete and thus not satisfactory. Effective solutions making economical sense are still being sought. The dynamic characteristics of rolling chatter being not well un...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=764789781&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The present status of thin sheet rolling and processing in industry is that progress made regarding rolling chatter analyses is incomplete and thus not satisfactory. Effective solutions making economical sense are still being sought. The dynamic characteristics of rolling chatter being not well understood, a new analytical model for the configuration of a four-high rolling mill stand is proposed in this dissertation. Using the model, the dominant sources of stiffness in the fifth octave and the third octave models are identified. The fifth octave chatter model comprises two sub-models, namely, a work roll sub-model and a sheet deformation roll-bite sub-model. The assumptions made for the derivation of the model are that the work rolls are isotropic linear elastic, that there is no gap or separation between the work roll and the backup roll at all times, and that the deformation of the metal sheet roll-bite is ideally homogeneous and elastic-plastic. In addition, only the vertical interactions of the work roll and the roll-bite are considered. The nonlinear characteristics of this dynamic system are contributed from the contact area of the work roll and the backup roll. Analyses show that the natural frequency of the nonlinear analytical model matches the fifth octave rolling chatter, and the dominant parameters of the dynamic instability are characterized. The sheet force resulted from the elastic-plastic deformation of the roll-bit is established to be the dominant factor affecting the dynamic response of the work roll. Although the developed rolling system is highly nonlinear, however, the induced instability and chatter in response to various types of sheet force excitations are either modal excitation or resonance-like beating, both of which are characteristically linear. It is demonstrated that the relative insensitivity of the model's stiffness to the exertion of sheet forces attributes exclusively to this linearity. The effects of inter-stand tensions, rolling speeds, friction between the work roll and the metal sheet roll-bite, and the thickness of the metal sheet on rolling chatter are discussed in the analysis of the dynamics of the rolling model. This research establishes the fundamental knowledge base required for the understanding of the characteristics and mechanism of the third and the fifth octave rolling chatters, and thus provides the essential basis for effective control of rolling instability and chatter-free roll mill design. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xi, 96 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 93-95). |