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A Study of the Effects of Ultrasonic Vibration on the Stability of Orthogonal Cutting Process Against Chatter

Yazdian, Mohammad | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40613 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Akbari, Javad; Movahhedy, Mohammad Reza
  7. Abstract:
  8. Machining chatter is unstable and destructive vibrations that leads to damages to the surface of workpiece and reduces the tool life. These damages have significant effects on surface quality and material removal rate. Many studies have been done on chatter modeling and control in various machining processes. On the other hand, recently, ultrasonic vibrations have been used in many manufacturing processes including cutting to enhance the quality of products. Therefore, it is important to investigate the effect of ultrasonic vibrations on the stability of cutting process. Although a number of advantages such as improved surface roughness of workpiece and reduced machining forces have been reported for ultrasonic cutting; and thus, it may imply that these two characteristics can probably decrease the chatter occurrence but these cases have been usually reported for those machining processes in stable conditions. Consequently, the investigation of probable positive and negative effects of ultrasonic vibrations on the stability of machining processes requires more studies. In this study, the effect of ultrasonic vibrations on occurrence or suppression of regenerative chatter vibrations has been investigated. Considering the changing direction of frictional force between tool and chip and also the tool separations from tool and workpiece, a mathematical model for ultrasonic vibration cutting is developed. The dynamic model of a machine tool structure extracted by experimental modal test. By combining these two models, simulations for different cutting conditions are carried out to study the stability of ultrasonic vibration cutting. The theoretical results indicate that the uni-directional ultrasonic vibrations have no significant effect on the stability of cutting process. However, simulations of elliptical ultrasonic vibration cutting show that the elliptical ultrasonic vibrations may have the ability to reduce the chatter and stabilize the process. Experimental tests have been carried out by designing and manufacturing ultrasonic vibration cutting system. The experimental tests were only done for one directional ultrasonic vibrations. The experimental test results show that, for the determined ultrasonic vibration amplitudes and frequency, the one directional ultrasonic vibrations have no significant effect on the stability but it observed that these vibration can reduce the cutting forces.
  9. Keywords:
  10. Ultrasonic-Vibration ; Vibration ; Elliptical Vibrations ; Machining Stability ; Force Model

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