English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

JASINEVICIUS, R.G. "Influence of Phase Transtion on Ductility Limits Observed in Ultraprecision Diamond Turning of Single Crystal Silicon". São Carlos, 1998, 166p. Tese de Doutorado Escola de Engenharia de São Carlos, Universidade de São Paulo. In recent years, considerable progress has been made on the study of the machinability of ft·agile materiais such as semiconductors crystals, optical glasses, ceramics, etc., because of the demand for faster fabrication processes of complex surface shapes for optoelectronic applications. The ductility presented by single crystal silicon during machining has been explained by fracture mechanics theories. Recently, some new theories have been presented in order to give another justify to this ductility. It was proposed that semiconductors single crystal ductility is likely the end result of a pressure/stress induced phase transformation during cutting. In this work, the difference between ductile and brittle mode single-point diamond turning on the surface of machined silicon samples were investigated using Raman scattering. In the ductile mode conditions of machining, there are always an amorphization of the surface samples, denounced by the activation of the broad Raman optical band at 470 cm· . This amorphous phase can be considered resulted from the phase transiton which silicon might have suffered. Contrary to the findings, in the brittle mode conditions, only the sharp optical phonon peak at 521.6 em -I is present in Raman spectra. Based on the observation that certain cutting parameters such as cutting depth and criticai chip thickness, e.g., the point where ductile-tobrittle transition occurs, somehow presents values in the same range (100-200 nm) that the amorphous phase layer depth extension after mechanical deformation. (p.e., indentation, scratching, polishing, nanogrinding and single point diamo"nd turning~ observed in the literature, it is propposed that the ductile regime has not a definite range o f values for the criticai parameters but instead, it is dependent o f the 'extension of the p]lase tran~ermed layer induced by pressure/stress generated by the tool tip/edgejm.eractioh .w~th workpiece during machining. Finally, it is sh'own that observati.On oftopopt'!,PhY and morphology of chip and the surface generated through SEM and AFM ~ti. ..offer very significant explanation of the materHtl remova! mecllflJlÍSJlJ.S in actioo .dJ.uing the current machining cut and diamond tool state. Key WI)J'{lu. ~~p Ppint Diamond turning, Phase transition, Ductile regime, Mp~~lf·~~)j~~ Diamond tool, Cutting mechanism.

Influência da transição de fase sobre os limites de ductilidade observados no torneamento de ultraprecisão do silício monocristalino