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Chatter Phenomena Prediction in Two-dimensional Milling Process from Chip Formation by Using Finite Element Method

Tavassoli, Meysam | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51788 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Movahhedy, Mohammad Reza
  7. Abstract:
  8. Chattering in cutting process is one of the destructive phenomena in machining, which results in ripple of workpiece surfaces. In this phenomenon, the displacement of the tool tip moves towards instability and the tool vibration continues. Eventually, the tool jumps or breaks out with relatively large shear forces, which leads to a reduction in the rate of production and machining. Since machining processes are very widespread, phenomenological studies of chatter have progressed in the field of modeling and empirical experiments. Research in the field of modeling is mainly intended to examine the dynamics of the tool in two ways: analytic and finite element. In these methods, there are always comparisons between the accuracy of the models with empirical tests. In analytical modeling, the complexity of the model phenomenon requires simplification, while finite element models consider the general nonlinear factors of governing equations in the phenomenon. This research presents a two-dimensional modeling with the consideration of milling complexities for predicting tools vibration in finite element method. The purpose of the present study is to investigate the accuracy of the finite element method in the stability of the milling process with regard to the formation and separation of chips. In order to solve the model Msc.Marc software has been chosen in which thermal effects are not considered. Dynamic characteristics of the tool has caluculated from the modal analysis enter the software. In this report, the constructive factors including the mode coupling phenomenon, and wave regeneration in machined surface has been investigated using the simulation of the chip formation in milling process. The remained effects of the vibration shows a reduction of chip thickness up to 38% in the solution of tool rotation and simulation results predict the frequency of the chatter very close to the natural frequency. In the end, by changing the cutting parameters and their effect on the process stability, the model's accuracy is examined. As predicted, the feed rate value did not have much effect on the stability, and by changing the axial depth and spindle speed, the passage from the stable to unstable region was observed
  9. Keywords:
  10. Chatter ; Chip Formation Mechanism ; Milling ; Finite Element Method ; Chatter Stability

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