Monitoring of the diamond turning of brittle materials

Author(s)

Helder Augustus Treviso da Silva

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2003-11-06

Examining board members

Jaime Gilberto Duduch; Renato Goulart Jasinevicius; Paulo Sérgio Pizani; Arthur Jose Vieira Porto; Juan Carlos Campos Rubio

• Advisor: Jaime Gilberto Duduch

Abstract

The diamond turning of brittle materials has risen in the last few years as a technique for the fabrication of high precision components in complex forms. Researches have shown that both surface finish and low subsurface damage are affected directly by the material removal mechanism (ductile, ductile/brittle and brittle together with brittle-to-ductile) transition. Therefore the phenomena envolved in the material removal modes may lend themselves as information to sensors for the monitoring of the process and precision/control of quality and surface integrity. Among the various sensors used in the monitoring of the turning process, the Acoustic Emission (AE) occupies an outstanding position. AE is sensitive enough to ductile/brittle removal modes, showing difficulties in the ductile mode due to its low removal rates. The use of AE as a monitoring technique for the diamond turning of brittle materials is proposed. For better understanding of the process signal, processing techniques and analysis of AE, such as a raw signal, frequency spectrum and RMS signal are used in association with SEM, AFM, micro Raman spectroscopy and indentation for the characterization of the surface obtained by different material removal modes. It has been shown that it is possible to identify dominant amplitudes and frequencies related to a determined type of removal using an appropriate analysis of the signal. Thus, better distinction of different removal levels from ductile, ductile/brittle and brittle can be accomplished (AU)