Polishing Characteristics Research Articles

Experimental investigation of ultrasonic-vibration polishing of K9 optical glass based on ultrasonic atomization

K9 optical glass has an important position in the field of optical material because of its excellent chemical stability and optical projection. The hard and brittle characteristics of K9 optical glass make conventional processing difficult and time-consuming. A non-conventional hybrid polishing system combining ultrasonic atomization (UA) spraying method and axial ultrasonic vibration was developed for processing K9 optical glass. This system utilizes the high-frequency vibration characteristics of ultrasonic vibration technology: On the one hand, the ultrasonic atomization spraying method is used to generate evenly distributed atomized droplets for polishing, on the other hand, the axial ultrasonic vibration of the polishing tool provides impact kinetic energy for the free abrasive particles. Mechanical polishing (MP), ultrasonic-assisted polishing (UVP), mechanical polishing under ultrasonic atomization spraying (UA-MP) and ultrasonic vibration polishing under ultrasonic atomization spraying (UA-UVP) were carried out on K9 optical glass. The material removal rate (MRR), material removal depth (MRD), surface quality and surface micromorphology of the polished workpieces were also analyzed and compared. The experimental results showed that the best surface was obtained at UA-UVP (AⅠ = 9 μm) with MRR of 0.0994 mm3/min, material removal depth of 26.816 μm, the Ra and Sa values were 0.028 μm and 0.033 μm respectively. Meanwhile, no obvious pits and scratches were observed on the micromorphological surface. Ultrasonic atomization contributes to even material removal from the polished surface and axial ultrasonic vibration of the polishing tool has a significant effect in improving the polishing characteristics, which provides the experimental basis for applying ultrasonic vibration technology in polishing.

Study on the Polishing Characteristics of the Rotating Cylinder-Based Magnetic Gel Abrasive Finishing

Magnetic gel abrasive finishing is a high-precision polishing method that uses magnetic forces to attract and restrain a gel abrasive, composed of aqueous slime gel, steel grits, and silicon carbon (SiC), for polishing workpieces. However, the magnetic adsorption performance of the gel abrasive will drop quickly when polishing non-ferromagnetic material such as stainless-steel or brass. Moreover, centrifugal force will push out the gel abrasive from the machining surface reducing the stability of polishing. Therefore, this paper developed a rotating cylinder-based magnetic finishing setup to allow the gel abrasive and workpieces to tumble and rotate together during the polishing process. To make the gel abrasive produce irregular and complicated movement paths for improving the polishing performance, this study first analyzed and compared the average surface roughness and removed material weight of workpieces using three kinds of motor operating modes; a unidirectional trapezoidal wave mode, a bidirectional sine wave mode, and a bidirectional trapezoidal wave mode. After identifying the best motor operating mode, the study further compared the polishing characteristics using several SiC particle and steel grit sizes. The experimental results showed that the rotating cylinder driven using a bidirectional trapezoidal wave could obtain better results for average surface roughness and removed material weight than the other two operating modes, while use of the larger steel grit size also obtained improved results. However, different silicon carbide particle sizes did not have a significant impact on the polishing characteristics.

Quantitative use-wear analysis of stone tools: Measuring how the intensity of use affects the identification of the worked material.

The identification of the use of stone tools through use-wear analysis was one the major methodological advances in Prehistoric Archaeology during the second half of the 20th century. Studies of use-wear analysis have decisively contributed to a better understanding of the cognitive capacities and the socio-economic organization of Prehistoric societies. Among use-wear traces, microwear polish is the most relevant evidence, as it allows the identification of the worked materials (i.e. wood, antler, hide, bone, stone…). This identification is currently carried out through the qualitative and visual comparison of experimental and archaeological tools. During the last decade, confocal microscopy is allowing the quantitative identification of the worked material through the texture analysis of microwear polish. Previous tests have accounted for the variability of use-wear traces as caused by different types of worked material. However, how the intensity of use, which is widely recognized as an important factor conditioning microwear polish characteristics, affects our capacity to identify the worked materials is poorly understood. This research addresses the dynamic nature of microwear polish through confocal microscopy and texture analysis. This research shows that use-wear polishing is a dynamic process and surface texture evolves continuously during the working time. The evolution fits a logarithmic function, so most texture modification takes place during the first phases of work. The way in which polish texture evolves through time differs from one contact material to the other. We demonstrate that, despite the dynamic nature of use-wear polish, different worked materials can be discriminated. However, some overlapping between used and unused surfaces and between worked materials occurs in the first stages of use. Moreover, polishes of similar characteristics (i.e. bone and antler) can show similar texture at advanced stages of use. These problems in identification can be in good measure overcome by creating dynamic models of polish texture in which not only the worked material but also the time of use is considered.

Polishing performance and mechanism of a water-based nanosuspension using diamond particles and GO nanosheets as additives

Single-crystal silicon carbide (SiC) is as a promising optoelectronic material for applications in solar cells, power converters and transistors. However, its high hardness combined with low fracture toughness has rendered significant challenges for high-efficiency and low-damage polishing. In this work, a novel polishing process was developed for single crystal SiC by using a water-based nanosuspension that used graphene oxide (GO) nanosheets and diamond particles as additives. The polishing characteristics of the diamond/GO hybrid nanosuspensions were investigated, using commercially available diamond suspensions as benchmarks. The hybrid nanosuspensions resulted in a superior polishing performance, as both surface quality and efficiency were substantially improved, owing to the synergistic effect of the oxidation and lubrication generated by GO nanosheets and the mechanical abrasion of diamond particles.

Effect of Interaction between Polishing Powder Particles and a Treated Material on the Polishing Characteristics of Optical Surfaces

Effect of Interaction between Polishing Powder Particles and a Treated Material on the Polishing Characteristics of Optical Surfaces

Gas-liquid-solid swirling flow polishing and bubble collapse impact characteristics

The mechanism of three-phase abrasive flow polishing method is first analyzed and then volume of fluid (VOF) method is introduced into three-phase abrasive flow modeling, combined with piecewise linear interface construction (PLIC) method to realize the tracking and calculation of bubble interface in the constrained flow channel. It shows the jet effect produced by bubble collapse can effectively enhance the velocity and turbulent kinetic energy of local fluid; bubbles collapse under the action of turbulent vortex, which in turn induce fluid to generate turbulence, which is an action-reaction process; the directional randomness of the turbulent vortex can avoid the directional strips induced by particles polishing in the same direction. The particle image velocimetry (PIV) measurement was used to observe the bubble collapse near the wall and the three-phase swirling flow field for validating the model and polishing experiments show that the target surface roughness can be down to 2.59 nm.

Highly efficient smoothing of Inconel 718 via electrochemical-based isotropic etching polishing

For the highly efficient and versatile polishing of metals, isotropic etching polishing (IEP), which is based on the merging of isotropic etching holes, has been developed. In this study, the feasibility and mechanism of isotropic etching polishing of nickel-based superalloy Inconel 718 (IN718) and the polishing characteristics have been studied. The potentiodynamic experiments revealed similar trends of the cathodic, passive, second passivation, and transpassive regions in all the electrolytes, while the corrosion susceptibility of IN718 successively decreased with the increasing H2SO4 concentration in the electrolyte. The etching anisotropy of the IN718 precipitated with different phases can be experimentally transmuted to isotropic etching by modulating the electrolyte concentration and keeping electrolyte temperature equal or above the room temperature. Because of the positive correlation of the etching current with isotropic holes density and diameter, etching at higher currents is promoted for the rapid and proficient polishing. The surface evolution mechanism during IEP has been confirmed. The surface roughness initially increased due to the formation of etching holes, then decreased abruptly owing to the rapid merging of etching holes and finally achieved a smooth surface. The wet grounded surface of IN718 with a roughness of Sa 62.7 nm has been transformed into a mirror-like smooth surface with a roughness of Sa 0.86 nm within 300 s of IEP at optimized conditions and a high MRR of 2.73 mm3/min has been achieved.

Study on Polishing Method Using Magnetic Levitation Tool in Superconductive-Assisted Machining

Superconductive-assisted machining (SUAM) is a polishing method that employs a magnetic levitation tool, which is based on a superconductive phenomenon called the pinning effect. Since the tool magnetically levitates, the issue of tool interference is eliminated. In this study, in order to set up the polishing conditions of the magnetic levitation tool, we evaluated the relation between the flux density distribution relative to the tool position and the holding force acting on the magnetic levitation tool to maintain its initial position, set by field cooling by the superconducting bulk. For the holding force, we measured the attractive, repulsive, restoring, and driving forces. We found that the greater the holding force, the smaller the initial distance between the superconducting bulk and the magnetic levitation tool. The attractive force was found to peak when the levitated tool was displaced 6 mm from an initial position of 9 mm from the bulk, and it became only the self-weight of the magnetic levitation tool at displacements of 30 mm and above, where the pinning effect broke down. We then evaluated the polishing characteristics for SUS304 and A1100P at a tool displacement that results in the maximum attractive force. In the polishing experiment, we employed a water-based diamond slurry because the temperature of the workpiece was close to room temperature. We found that it was possible to polish SUS304 and A1100P while avoiding the effects of magnetization due to the polishing pressure or induced currents that accompany the rotation of the metal plate. The arithmetic average roughness, Ra, of A1100P was relatively high due to the effect of scratches, while that of SUS304 improved from 92 nm before polishing to 55 nm after polishing when polished with grains with a diameter of 1 μm.

Holocene grinding stones at Madjedbebe reveal the processing of starchy plant taxa and animal tissue

The functional study of ground stone artefacts and the analysis of charred plant remains together demonstrate that plant foods played a significant role in the diets of Aboriginal Australians through all occupation phases at the Pleistocene-aged archaeological site of Madjedbebe. Here we report studies of three sandstone grinding stones from the Holocene levels of the site, one associated with a radiocarbon age of 690 cal. BP, and the others with an age of 8320 cal. BP. The functional analyses involved technological studies combined with brightfield microscopy, starch grain analysis, biochemical testing and gas chromatography-mass spectrometry (GC–MS). All three tools had usewear consistent with plant processing, with two having abrasive smoothing and polish characteristics typical of seed-grinding. Significant quantities of starch were recovered from each artefact and demonstrate the early Holocene processing of waterlily (Nymphaea violacea) and possibly kapok bush root (Cochlospermum fraseri), cheeky yam (Amorphopallus galbra) and long yam (Dioscorea transversa). In addition to starchy plant foods, one of the tools was used for processing animal tissue, as indicated by biochemical testing and GC–MS analysis, inferring a multi-functional use.

Numerical and experimental study on the ultrasonic-assisted soft abrasive flow polishing characteristics

To resolve the low-polishing efficiency problem caused by the turbulent layer separation in soft abrasive flow (SAF) processing, an ultrasonic-assisted SAF (UA-SAF) method is proposed based on the vibration effect. The coupled computational fluid dynamics (CFD)-discrete element method (DEM) modeling method (CFD-DEM) and the dynamic mesh are used to represent the UA-SAF flow and the periodic moving boundary caused by ultrasonic vibration, while the particle-wall erosion is calculated by the Archard model. Through tracking the abrasive particle motion in the simulation, the particle-wall collision states and the particle cutting effect are revealed, which mainly includes the particle plowing and the particle impact erosion. It has been found from the simulation that the fluid turbulent motion and the fluid dynamic pressure which are the power source for the particles to obtain the anisotropic cutting kinetic energy can be strengthened obviously by the ultrasonic vibrating, which results in the increase of the probability of particle impacting the target surface, and then the particle-wall wear rate and the wear area can be improved. A set of comparative experiments, including the rough and precision polishing procedures, are then conducted to evaluate the polishing performance by using the SAF and UA-SAF, respectively. The variations of the surface roughness and the workpiece mass are obtained, and the surface morphologies are observed. The experimental results prove that the ultrasonic vibration can effectively improve the abrasive flow polishing efficiency and precision without producing cavitation erosion.

Investigation on Feasibility of Polishing Concave Surfaces Using Magnetic Compound Fluid Slurry

Concave surfaces are widely used in the shells of smart devices, such as smartphones, watches, or molds. The quality of the concave surface is important in enhancing the value of these products. In order to improve the surface quality, the polishing process is crucial for removing defects on the concave surface and for smoothing the surface after machining or grinding. Magnetic assisted polishing is a promising method that can be used to meet the high standard of surface quality required. In this work, as a promising smart material in nano-precision polishing, magnetic compound fluid (MCF) slurry was used for the first time to polish a concave surface with a magnet that is magnetized in the radial direction. A simulation of the magnetic field distribution was performed in advance to clarify the polishing characteristics in theory. Subsequently, a polishing experiment was conducted to investigate the feasibility of this polishing method. Finally, the results demonstrated that both a curved surface and a flat surface could be polished successfully. Furthermore, the nano-precision PV value (the distance from the peak to the valley in the surface profile) and the surface roughness Ra were obtained for both areas, and this method was demonstrated to be capable of polishing concave surfaces and worthy of further research.

Predicting Polish transport industry equilibrium characteristics as an inverse problem: An Entropy Econometrics Model

Abstract The business environment dynamics is governed by a high degree of uncertainty and risk; consequently, in a majority of cases investors face serious difficulties when making business decisions. Additionally, when detailed statistical information relating to industry is missing, any decisions may become a matter of highly risky conjectures. The present article proposes a simultaneous equation model based on the entropy econometrics estimator for recovering some key industrial subsector long-term equilibrium characteristics in the situation where only sparse, insufficient statistical information is available (e.g. only aggregated data on the whole industry). The model is applied to the transportation equipment manufacturing industry in Poland, which is composed of eight sub-sectors. As a result of the above procedure, an observation has been made that all firms from different sub-sectors have to increase their steady-state concentration ratios, while the highest concentration corresponds to the lowest increase in profitability. The model outputs conform to the market tendency in this sector and should lead to further applications of the NCEE methodology in business activity on a worldwide scale.

Cerium oxide (CeO2-x) nanoparticles with high Ce3+ proportion synthesized by pulsed plasma in liquid

Cerium oxide (CeO2-x) nanoparticles were synthesized using a simple one-step method known as the pulsed plasma in liquid (PPL). XRD analysis showed the production of pure cubic cerium oxide (Fm 3‾ m). HRTEM and XANES analysis confirmed the monophase cubic CeO2-x, and exclude the presence of the hexagonal Ce2O3 and/or mix phase of CeO2/Ce2O3 in the particle layers. HRTEM analysis showed that most particles were about 3 nm in diameter. XPS analysis showed that the cerium oxide nanoparticles synthesized by the PPL method had a higher Ce3+ proportion (42.2%) than some commercial powders, and also higher than the previous reported nanoparticles. The present cerium oxide nanoparticles showed high visible light-induced photocatalytic activity in the degradation of methyl orange (MO) and better polishing characteristics of quartz glass, compared to commercial samples. These results may attribute to the high Ce3+-ion content and/or the small particle size.

Advances in polishing of optical freeform surfaces: A review

Abstract Ultra-precision polishing is one of the main machining processes for components with high surface finish requirements, such as optical molds. Typical optical mold materials include mold steel, silicon carbide and tungsten carbide, which have many excellent properties like strong corrosion resistance, low thermal expansion coefficient, strong oxidation resistance, low density, and high hardness. To ensure that the replicated parts meet high precision form and finish specifications, the molds made in hard and brittle materials must be machined to obtain a high-quality part surface. Therefore, polishing has evolved into ultra-precision polishing, which has a critical impact on the mold service life as well as the precision optical component quality. This paper presents the basic concepts and classification of ultra-precision polishing, introduces typical polishing processes, discusses polishing mechanisms and characteristics, and finally indicates the directions for future development of ultra-precision polishing processes.

Sample preparation and microscopical investigation techniques for metal and ceramics containing graphite and graphene-like layered particles.

Scanning electron microscopy (SEM) techniques are widely used in microstructural investigations of materials since it can provide surface morphology, topography, and chemical information. However, it is important to use correct imaging and sample preparation techniques to reveal the microstructures of materials composed of components with different polishing characteristics such as grey cast iron, graphene platelets (GPLs)-added SiAlON composite, SiC and B4 C ceramics containing graphite or graphene-like layered particles. In this study, all microstructural details of gray cast iron were successfully revealed by using argon ion beam milling as an alternative to the standard sample preparation method for cast irons, that is, mechanical polishing followed by chemical etching. The in-lens secondary electron (I-L-SE) image was clearly displayed on the surface details of the graphites that could not be revealed by backscattered electron (BSE) and Everhart-Thornley secondary electron (E-T SE) images. Mechanical polishing leads to pull-out of GPLs from SiAlON surface, whereas argon ion beam milling preserved the GPLs and resulted in smooth surface. Grain and grain boundaries of polycrystalline SiC and B4 C were easily revealed by using I-L SE image in the SEM after only mechanical polishing without any etching process. While the BSE and E-T SE images did not clearly show the residual graphites in the microstructure, their distribution in the B4 C matrix was fully revealed in the I-L SE image.

Effect of the components of Magnetic Compound Fluid (MCF) slurry on polishing characteristics in aspheric-surface finishing with the doughnut-shaped MCF tool

For the aspheric optical surface finished with a doughnut-shaped MCF (magnetic compound fluid) polishing tool, the performance of the polishing tool depends mainly on the properties of the MCF slurry. Therefore, understanding the effect of each MCF slurry component on the polishing characteristics is crucial to developing novel polishing techniques. In this paper, the polishing principle was depicted and the corresponding polishing jig was constructed with a six-degree-of-freedom manipulator. The conical surfaces, which were considered as special aspheric surfaces, were experimentally polished under proper polishing conditions to examine the effects of the carbonyl iron particles (CIPs) concentration and the sizes of the abrasive particles (APs) on the polishing ability to remove material/tool marks and improve work surface qualities. Theoretical analyses were also performed to gain a more comprehensive understanding of the behaviors of CIPs and APs in the magnetic field. The results were shown as follows: (1) The CIPs concentration affected positively the magnetization of the MCF slurry, leading to better performance in the removal rate of material/tool marks when a higher CIPs concentration of was applied. The best surface quality was attained with a CIPs concentration of 45 wt%. (2) Larger APs were beneficial for obtaining higher removal rates of material/tool marks. The APs with 1 μm in diameter were preferred for achieving a better surface quality. (3) Ferric clusters were formed along the magnetic line of force and their orientations changed periodically to stir the APs with the magnet revolution. (4) The Aps, at a given working gap, can squeeze the work-surface. The squeezing action was much more intense when larger APs and the MCF slurry with a higher magnetization were employed. (5) The material removal model suggested that the material was removed due to the APs and the relative motion between the work-surface and APs.

Fused silica contamination layer removal using magnetic field‐assisted finishing

AbstractFused silica optics used in lasing systems requires a high laser‐induced damage resistance. Processes typically used to polish fused silica lenses induce subsurface and surface damage that collect ceria abrasive, creating a layer of contamination. The contamination can be a precursor to laser damage during use. A preliminary study showed the feasibility of magnetic field‐assisted finishing (MAF) for polishing fused silica and suggested possible beneficial effects of the MAF‐polished surface on the laser‐induced damage threshold (LIDT). This paper proposes a method to examine the fundamental polishing characteristics of MAF for fused silica. Using the proposed method, this paper explores the material removal characteristics of the MAF process and improves the understanding of the MAF polishing mechanism. The 45% improvement of LIDT shows the efficacy of MAF for removing the contamination layer of fused silica surfaces with minimal changes in the surface roughness.

Study of polishing characteristics of glass substrate by suede pad:

Study of polishing characteristics of glass substrate by suede pad:

Degradation Prediction Model for Friction of Road Pavements with Natural Aggregates and Steel Slags

Steel production wastes (steel slags) are used more often in asphalt concrete pavements as a valuable replacement for natural aggregates, which are becoming increasingly rare. In this paper authors investigate the polishing characteristics of aggregates, and in particular of steel slags, used in bituminous road surfacing, are a major factor in determining the resistance to skidding. The main purpose of the study is the identification of a suitable degradation model, based on friction indicators, in the laboratory, as well as the comparison of in-situ pavement skid resistance with the cumulative number of passing vehicles over the years. The model predicts the expected resistance to skidding of the road surface based on the knowledge of the polished stone value (PSV) of the aggregates and the expected traffic on the road. In this study, several types of aggregates were compared: steel slag, limestone, limestone and slag mixture, diabase, Criggion stone and basalt. Using a standard PSV test, it was found that the aggregates did not reach the lower value of skid resistance (equilibrium value). The analysis of the British Portable Number (BPN) data versus polishing time allowed to empirically derive a regression model for each investigated aggregate. Hence, it appears possible to define both an investigatory level and threshold level to predict the actual residual life of the pavement from the examination of skid resistance.

Seronegative hepatitis C virus infection in Polish blood donors-Virological characteristics of index donations and follow-up observations.

Nucleic acid testing (NAT) was implemented in Poland in 1999 for screening of plasma for fractionation and for all blood donors in 2002. To analyze seronegative NAT‐positive samples representing hepatitis C virus (HCV) window‐period (WP) in the years 2000 to 2016 and to determine infection outcome. We analyzed results of 17 502 739 donations screened in minipools (6‐48) or individually. Index samples underwent viral load (VL) quantification, genotyping and Ag, and anti‐HCV re‐testing using chemiluminescence (CMIA), electrochemiluminescence (ECLIA), and fourth‐generation enzyme‐linked immunosorbent assay (IV EIA) assays. HCV‐seronegative infections were identified in 126 donations (7.2/mln donations; 95% confidential intervals, 6.0‐8.6). Frequency of NAT yields was decreasing over time. Of the initial 126 seronegative index cases 106 were retested: 32.1% were reactive in IV EIA, 11.3% in ECLIA, and 1.9% in CMIA. The lowest VL correlated with absent anti‐HCV and HCV Ag, while VL was highest when the antigen was detectable and then it decreased when anti‐HCV appeared at a level detectable by sensitive third generation tests while retesting. The proportion of genotype 1 was 38.9% in samples positive only for HCV RNA and 71.4% in samples that were anti‐HCV reactive in re‐testing. In parallel, genotype 3 frequency was 50% in the former group and 21% in the latter. NAT is an effective measure to limit HCV transmission by transfusion and IV EIA seems to have higher clinical sensitivity than ECLIA. Samples representing likely successive phases of early HCV infection were characterized by different genotype distribution probably due to very early elimination of genotype 3.