Al6061 surface roughness and optical reflectance when machined by single point diamond turning at a low feed rate.

L H Li,C Y Chan,N H Yu,W B Lee

doi:10.1371/journal.pone.0195083

L H Li, C Y Chan + Show 2 more

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https://doi.org/10.1371/journal.pone.0195083

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Journal: PloS one	Publication Date: Apr 2, 2018
Citations: 9	License type: CC BY 4.0

Affiliation: Hong Kong Polytechnic University, Shenzhen Polytechnic

Abstract

Ultra-precision face turning of Al6061 mirrors using single point diamond turning (SPDT) was undertaken to investigate the correlation between the surface roughness and reflectance. By reducing the feed rate, the optimal feed rate when the chip formation became unstable was studied. Most importantly, the impact on the roughness and reflectance was examined when the chip formation ceased to be continuous. It was determined that for a feed rate below 3 mm/min, the surface roughness always improved as the feed rate decreased, at the cost of a reduction of the normalized reflectance. The reduction of reflectance was determined to be the result of the lower material removal rates that led to a discontinuous chip formation.

Highlights

The Al6061 alloy is commonly used in ultra-precision machining because of its good machinability [1,2,3], and this aluminium is the preferred material for mirrors in spaceborne applications [4]
An assessment method was developed using an integrating sphere lumens measurement system to assess the reflectivity of a single point diamond turned surface of Al6061 alloy
It was determined that the reflectance of Al6061 alloy does not always monotonically increase with a decrease in the surface roughness

Summary

Introduction

The Al6061 alloy is commonly used in ultra-precision machining because of its good machinability [1,2,3], and this aluminium is the preferred material for mirrors in spaceborne applications [4]. Previous studies have investigated the reflectance of metal alloy surfaces for different purposes, such as spaceborne applications or non-contact measurements. In these studies, factors such as the wavelength of the incident beam, the surface roughness and the material properties may affect the surface reflectance. Bennett and Porteus (1961) [6] studied the reflectance of an optically polished surface, at normal incidence, with surface roughness. They determined that the reflectance was wavelength-dependent.

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