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Liao W.,National University of Defense Technology | Liao W.,Hunan Key Laboratory Of Ultra Precision Machining Technology | Dai Y.,National University of Defense Technology | Dai Y.,Hunan Key Laboratory Of Ultra Precision Machining Technology | And 2 more authors.
Applied Optics | Year: 2014

Morphology evolution at microscopic scales has an inseparable relationship with surface material behaviors, especially during ultrasmooth surface fabrication. In this work, the influence of initially existing local densification on ion nanopatterning of a fused-silica surface is investigated. Our research results indicate that fused-silica surfaces will easily densify permanently under a compressive load, exhibiting an anisotropic surface at the nanoscale. During the subsequent ion-beam sputtering process, the densification-dependent sputtering would influence and even dominate surface morphology evolution, which is identified as being an important evolution mechanism. However, ion-induced relaxation mechanisms will overcome surface roughening in the absence of local densification, and an ultrasmooth surface with root mean square roughness down to 0.06 nm is obtained in our experiment. © 2014 Optical Society of America. Source


Peng W.,National University of Defense Technology | Peng W.,Hunan Key Laboratory Of Ultra Precision Machining Technology | Guan C.,National University of Defense Technology | Guan C.,Hunan Key Laboratory Of Ultra Precision Machining Technology | And 2 more authors.
Optics Express | Year: 2014

Material removal rate has greatly relied on the distribution of shear stress and dynamic pressure on the workpiece surface in hydrodynamic effect polishing (HEP). Fluid dynamic simulation results demonstrate that the higher rotation speed and smaller clearance will cause the larger material removal rate. Molecular dynamic (MD) calculations show the bonding energy of Si-O in the silicon-oxide nanoparticle is stronger than that in the quartz glass, and therefore the atoms can be dragged away from the quartz glass surface by the adsorbed silicon-oxide nanoparticle. The deep subsurface damage cannot be efficiently removed by HEP due to its extremely low removal rate. However, the subsurface damaged layer can be quickly removed by ion beam figuring (IBF), and a thinner layer containing the passivated scratches and pits will be left on the surface. The passivated layer is so thin that can be easily removed by HEP process with a low material rate under the large wheel-workpiece clearance. Combined with the IBF process, the subsurface damage and surface scratches have been efficiently removed after the HEP process. Meanwhile there are not obvious duplicated marks on the processed surface and the surface roughness has been improved to 0.130nm rms, 0.103nm Ra. © 2014 Optical Society of America. Source


Peng W.,National University of Defense Technology | Peng W.,Hunan Key Laboratory Of Ultra Precision Machining Technology | Guan C.,National University of Defense Technology | Guan C.,Hunan Key Laboratory Of Ultra Precision Machining Technology | And 2 more authors.
Optical Engineering | Year: 2014

A material removal mechanism of ceria particles with different sizes in a glass polishing process was investigated in detail. Contrast polishing experiments were carried out using ceria slurries with two kinds of particle sizes and different amounts of hydrogen peroxide (H2O2) added in the slurries. The Ce3+ ions on the surface of the ceria particles were gradually oxidized to Ce4+ with increased H 2O2 concentration. It was found that the material removal rate (MRR) decreased sharply with an increasing concentration of H 2O2. There was no material removal when the concentration reached 2.0% for nanoparticle slurry. Nevertheless, the application of microparticles made the MRR decrease to a constant value when excessive H 2O2 was added. By comparison, we conclude that the material is removed by chemical reaction for ceria nanoparticles, while chemical reaction and mechanical abrasion simultaneously take place for ceria particles with sizes at scale of micrometers in the glass polishing process. It is clearly demonstrated from the experimental results that Ce3+ instead of Ce4+ ions play an important role in chemically reacting with the glass surface. An ultrasmooth surface with root-square-mean roughness of 0.272 nm was obtained after being polished by ceria nanoparticles. © 2014 Society of Photo-Optical Instrumentation Engineers. Source


Tian F.,National University of Defense Technology | Tian F.,Hunan Key Laboratory Of Ultra Precision Machining Technology | Yin Z.,National University of Defense Technology | Yin Z.,Hunan Key Laboratory Of Ultra Precision Machining Technology | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2016

The fabrication of high-quality freeform surfaces is based on ultra-precision diamond turning with fast tool servo (FTS) technology which allows direct machining of the freeform surfaces with sub-micrometric form accuracy and nanometric surface roughness. Surface roughness is an important factor in evaluating the performance of the optical freeform surfaces. This paper presents a theoretical and experimental analysis of surface generation in ultra-precision single-point diamond turning. In this model, we take into consideration the basic machining parameters as well as the relative vibration between the workpiece and the tool in both the cutting and feeding directions. Theoretical model is built to predicting the surface roughness of machined flat surface as well as freeform surfaces. A series of experiments have conducted and the results show good correlation between the theoretical model and the fabricated surfaces. © 2016 Springer-Verlag London Source


Tian F.,National University of Defense Technology | Tian F.,Hunan Key Laboratory Of Ultra Precision Machining Technology | Yin Z.,National University of Defense Technology | Yin Z.,Hunan Key Laboratory Of Ultra Precision Machining Technology | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2016

Single point diamond turning (SPDT) based on tool servo system is one of the significant techniques to fabricating the optical freeform surfaces. The conventional fast tool servo (FTS) actuated by piezoelectric actuator has the problem of short stroke, while the drawback of the slow tool servo (STS) is low frequency response. This paper briefly presents a novel long range fast tool servo (LRFTS) with high frequency response and long stroke. The total stroke can reach up to 30 mm. The LRFTS uses a voice coil motor as the actuating element and air bearings as the guide mechanism. The LRFTS utilizes a linear encoder to measure the displacement of the tool for closed loop control. The servo performance of the LRFTS system’s amplitude and frequency response is analyzed. The physical model of the LRFTS is identified. A series of experiments have been conducted to verify the performance of the designed LRFTS. Micro-lens array fabrication experiments on an aluminum part are conducted using the designed LRFTS. The factors influencing the surface roughness have been analyzed. © 2016 Springer-Verlag London Source

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