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Prediction of Machining Chatter Based on 2 Dimensional FE Dynamic Modeling of Chip Formation

Haj Mohammadi, Mohammad Saleh | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42770 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Movahhedi, Mohammad Reza
  7. Abstract:
  8. In machining processes, chip formation is one of the most important methods to obtain the final shape of a work-piece. Improving the machining processes leads to the increase in the material removal rate (MRR) and reduction of high economical costs. Vibration is an undesirable phenomenon in machining processes because it results in reduction of material removal rate (MRR), poor surface finish and increased tool wear. Among various types of vibration, self-excited vibration or chatter is the most important one. It is obvious from previous investigations that for prediction of machine tools vibration, many simplifications were assumed while the linear and non-linear effects are not considered simultaneously. Using finite element method (FEM) with incorporating all the linear and nonlinear factors in metal removal process can aid to the chatter prediction in practical conditions and selection of the stable cutting factors. These effects include cutting conditions, chip formation mechanism, tool geometry, friction and thermal effects between tool and work-piece and system dynamic behavior. In this paper, dynamical and thermo-dynamical analysis of one and two dimensional orthogonal machining processes is accomplished through MARC-FEM software. Unlike the previous works, the effects of regenerative chatter and mode coupling (as sources of self excited vibrations) are considered in this model. In addition, the effects of linear and nonlinear factors of friction and plastic deformation are included simultaneously. Thereafter, the process stability is analyzed and compared for the systems with/without thermal effects (through stability lobes diagram). According to the results obtained for the tool tip vibration in alongside with stability lobes diagram, appropriate parameters of the cutting process are presented (which lead to the stable conditions). Results show that decreasing the width of cut and tool rake angle; increasing the cutting velocity and thermal effects lead to the more stable conditions. It is observed that the regenerative chatter is more dominant on the system behavior than the mode coupling. Finally, simulation results are verified by experimental work.

  9. Keywords:
  10. Finite Element Method ; Stability Boundary ; Two Dimensional Model ; Machining Chatter ; Machining Process ; Temperature Effect

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