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| Author(s): |
Giuliana Sardi Venter
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD) |
| Defense date: | 2019-01-29 |
| Examining board members: |
Maíra Martins da Silva;
Armando Italo Sette Antonialli;
Reginaldo Teixeira Coelho;
Anselmo Eduardo Diniz;
Robson Pederiva
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| Advisor: | Maíra Martins da Silva |
| Abstract | |
Chatter is a vibration that occurs during machining operations due to the complex interaction between the machined part, chip and cutting tool during cutting. Strategies for chatter modeling, monitoring, and reduction are constantly under investigation, as chatter impairs industry productivity and the quality of machined parts. This research presents a methodology to reduce the vibration caused by chatter by improving the stability limit in turning processes using piezoelectric layers embedded in the tool holder. This improvement is based on the fact that the structural damping has a proportional relation with the stability limit. Thus, the instability that occurs during chatter operations can be significantly reduced by increasing the structural damping of the system, either actively or passively. In the active control methodology studied, the piezoelectric layers were connected to a velocity feedback control scheme. In the passive control methodology, the piezoelectric layers were connected to an inductive-resistive shunt circuit. Due to the inherent complexity of the cutting process, chatter is a phenomenon that can be governed by nonlinearities present in the process. Thus, an analysis of the system\'s nonlinear response under the action of different control methods is necessary in order to understand how the dynamic response of the system will be affected. The efficacy of both strategies was evaluated through numerical and experimental analysis, in which the system responses were studied through phase diagrams and numerical and experimental spectra. Frequency response functions of the tool holder and their respective experimental lobule diagrams were also analyzed in order to study the increase in the stability limit provided by the control methods. It can be concluded that both strategies may be good alternatives for the reduction of chatter, and vibration in general, in the processes, since numerical and experimental results have effectively shown an increase in structural damping and a decrease in vibration. However, the proposed active strategy is more robust than the passive one, since it does not require the fine tuning of the control parameters. In addition, it was possible to obtain in an experimental setup a considerably greater increase of the structural damping using the active control method. Due to the technological limits, such as electrical tension limits and operational amplifiers, it was only possible to reduce the chatter vibration with the use of both control methods, therefore not being possible to suppress the vibration experimentally, contrary to what was observed in numerical results. (AU) | |
| FAPESP's process: | 14/23108-4 - Active control for chatter reduction in turning process using multilayer piezoelectric devices |
| Grantee: | Giuliana Sardi Venter |
| Support Opportunities: | Scholarships in Brazil - Doctorate |