Removal Mode Research Articles

Photocatalytic heterostructures-based BiFeO3 embedded liquid natural rubber (LNR) for highly removal of cationic dye under direct sunlight

Abstract In this study, the composite consists of bismuth ferrite (BiFeO3) photocatalyst embedded into macroporous liquid natural rubber (LNR) matrices was fabricated to assess the removal efficiency of methylene blue (MB) dye under direct sunlight. The structural properties and morphology of LNR-BiFeO3 composite were thoroughly characterised using spectroscopic and microscopic methods. X-Ray diffractogram of the composite demonstrated successful inclusion of BiFeO3 into the LNR network. During solar-driven photocatalytic activity of LNR-BiFeO3, the effects of selected operating parameters on removal efficiency, such as catalyst dose, irradiation time, initial dye concentration, and solution pH, were determined. At optimum catalyst dose (0.15 g BiFeO3) and irradiation time (3 h), degradation of 10 ppm MB was remarkably efficient as 98.9 + 0.09 % have been successfully discarded from the system. The composite had managed to degrade up to 75 ppm MB with degradation efficiency exceeding 89.0 %. In order to investigate the mechanism of MB removal using LNR-BiFeO3, monitoring of removal mode, kinetics and scavenger study were carried out. The outcomes revealed that MB removal did fit well with Langmuir-Hinshelwood kinetic model, in which BiFeO3 (Ebg = 1.76 eV) is responsible for photodegradation process using OH―, O2― and h+ with assistance of adsorption by the composite. The composite could be reused for five cycles without any post-treatment or separation step, and most importantly, no significant loss noted in its activity. This eco-friendly and economical approach will render new opportunities for this advanced photocatalyst as great potential in environmental remediation for wastewater treatment.

Effects of Depth of Cutting on Damage Interferences during Double Scratching on Single Crystal SiC

In this work, the damage interference during scratching of single crystal silicon carbide (SiC) by two cone-shaped diamond grits was experimentally investigated and numerically analyzed by coupling the finite element method (FEM) and smoothed particle hydrodynamics (SPH), to reveal the interference mechanisms during the micron-scale removal of SiC at variable Z-axis spacing along the depth of cutting (DOC) direction. The simulation results were well verified by the scratching experiments. The damage interference mechanism of SiC during double scratching at micron-scale was found to be closely related to the material removal modes, and can be basically divided into three stages at different DOCs: combined interference of plastic and brittle removal in the case of less than 5 µm, interference of cracks propagation when DOC was increased to 5 µm, and weakened interference stage during the fracture of SiC in the case of greater than 5 µm. Hence, DOC was found to play a determinant role in the damage interference of scratched SiC by influencing the material removal mode. When SiC was removed in a combined brittle-plastic mode, the damage interference occurred mainly along the DOC direction; when SiC was removed in a brittle manner, the interference was mainly along the width of cutting; and more importantly, once the fragment of SiC was initiated, the interference was weakened and the effect on the actual material removal depth also reduces. Results obtained in this work are believed to have essential implications for the optimization of SiC wafer planarization process that is becoming increasingly important for the fabrication of modern electronic devices.

English

Coffee cherries were processed traditionally by the wet method that uses large quantities of water and eco-friendly methods that utilizes less water and operate mechanically to remove mucilage. The study is aimed at determining the effects of traditional and newly developed coffee processing methods on fatty acid profiles and biochemical components of two coffee cultivars. A complete randomized design was used for the study. Fresh coffee cherries for two cultivars commonly grown in Kenya, Ruiru 11 and SL 28, were processed using three different processing methods. The methods varied on the mode of mucilage removal and pulping techniques. The parchment obtained from the three processes, wet pulper, hand pulper and eco-pulper methods, were sundried and subjected to chemical analysis. Fatty acids profiles were analyzed by the use of a gas chromatography method and biochemical content; caffeine, trigonelline and chlorogenic acid were determined by HPLC analysis. The processing methods showed significant variations in the fatty acids concentrations but did not significantly affect the levels of biochemical compounds. The concentration of fatty acids ranges from 1.16 to 16.88%, with linoleic acid being dominant. The trigonelline level ranges from 1.24 to 1.36%, caffeine ranges from 1.36 to 1.45% and chlorogenic acid from 5.34 to 5.46% in the samples from the different processing methods.   Key words: Processing methods, coffee cultivars, fatty acids, biochemical compounds.

Adjustment of Hardness of (CrFeMn)x(NiyAl)1−x, (y = 1,3 and x = 0.6,0.72,0.80) High Entropy Alloys by Deliberate Control of Intermetallic Phase Formation: Microstructural Evolution, Hardness and Dry-Sliding Wear Response

In this work, the softening of the hard, NiAl containing, Cr–Fe–Mn–Al–Ni high entropy alloy system by the introduction of Ni3Al, an intrinsically ductile intermetallic compound, is reported. The alloys were prepared by vacuum arc melting and their phase formation prediction models were verified in terms of the actual presented microstructural features. X-ray analysis revealed the presence of NiAl and Ni3Al intermetallic compounds in each HEA system group. The microstructure of all six examined alloys in their as-cast condition consisted of two phases (NiAl-rich B2 and FeCr-rich A2) featuring various eutectic morphologies, while spinodal decomposition was evident in every case. The NiAl–Cr pseudo-binary phase diagram was used for the explanation of the solidification sequence in each alloy. In terms of mechanical properties, HRC hardness measurements showed that higher amounts of Ni3Al can lower the alloys’ hardness up to half its initial value. Finally, dry-sliding wear testing revealed an oxidation-delamination mode of material removal in both HEAs group, while the Ni3Al containing alloys also exhibited parts of abrasive wear mode. Hardness vs composition diagram. It can be seen that by adjusting the type and the extent of the intermetallic phase being formed (a—NiAl, b—Ni3Al), the hardness can be controllably modified within a range of 21 to 58 HRC. The related wear rates are also included

Strain Rate Effect on the Ductile Brittle Transition in Grinding Hot Pressed SiC Ceramics

Surface and subsurface damage are still persistent technical challenges for the abrasive machining hot pressed-silicon carbide (HP-SiC) ceramics. Therefore, an investigation of the material behavior and critical depth of ductile to brittle transition (DBT) is essential for improving high precision and quality grinding HP-SiC ceramics. In this paper, single-grit grinding experiments with different scratch speed were conducted to study strain rate effect on the critical depth of DBT. The nanoindentations were performed to test the hardness and Young’s modulus changes of DBT position under different scratch speeds. The material removal mechanism and phase changes underneath the scratch groove were investigated using Raman tests. Based on the specific energies consumed in ductile and brittle modes of machining, a theoretical model of the critical depth of DBT was developed. The experimental results suggest that high scratch speeds generate high nanohardness, high Young‘s modulus and high critical depth of DBT of HP-SiC ceramics. The measured critical depth of DBT shows a good agreement with the predicted value calculated by the developed model. The subsurface damage depth reduced with high strain rate. Furthermore, the Raman results revealed that dislocations and amorphous transformation dominated the ductile removal mechanism of HP-SiC grinding. The fracture chips and subsurface damage depth was determined by the lateral crack and median crack, respectively. This paper’s results provide a fundamental understanding of the effect of grinding speed on the material removal mode of HP-SiC ceramics.

Effects of wheel speed on surface/subsurface damage characteristics in grinding of glass-ceramics

Glass-ceramic is widely used in optics and other areas because of its good physical and mechanical properties. However, the accompanying hard and difficult to machine characteristic brings great challenges to the commonly used grinding in industry. Previous researches on the removal mechanism of glass-ceramic are basically traditional low-speed scratch and low-speed grinding, ignoring the effect of the wheel speed on surface/subsurface damage. In this study, the effects of the wheel speed on the surface morphology, surface roughness, and subsurface damage of Zerodur glass-ceramics were studied at different wheel speeds based on a multi-step grinding process. Experimental and analytical results showed that increasing wheel speed can restrain the occurrence and development of brittle fractures due to the effects of strain rate and grinding temperature, resulting in fewer and smaller micro-pits and micro-cracks, and thus more signs of plastic flow are observed. In addition, the effects of wheel speed on surface roughness under the semi-finishing grinding stage are not as clearly defined as on that under the rough and finishing grinding stages. The smeared layers on the ground surface, which are related to the compound effects of the grinding temperature and semi-finishing grinding conditions, are recognized as the major contributor to the contradictory surface roughness results. Furthermore, the effect of wheel speed can prevent crack from nucleating and propagating, and then leads to a smaller depth of subsurface damage. Accordingly, there is a general trend toward subsurface damage depth with the increase of undeformed chip thickness, regardless of the grinding conditions. In a word, higher wheel speeds are easier to achieve ductile removal mode and conversely, the glass-ceramic is more prone to a brittle removal mode. The research is expected to provide guidance for grinding-induced damage control and the engineering application in high precision optical parts of glass-ceramic.

ОПРЕДЕЛЕНИЕ МАССЫ ГРУЗОЗАХВАТНОГО СРЕЗАЮЩЕГО МЕХАНИЗМА ДЛЯ АЭРОСТАТНОЙ СИСТЕМЫ ТРЕЛЕВКИ

The article presents the results of practical and theoretical studies in the field of application of balloon-cable systems capable of operating in the mode of vertical removal of a tree from a forest canopy and its subsequent transportation to a loading point. The relevance of this technological direction lies in the impossibility of traditional forestry equipment to carry out the process of harvesting and transporting wood without violating environmental requirements. It is noted that clear environmental effect can be achieved using air wood harvesting and transportation means, in particular when using balloon systems. A brief description of the operation of the load-gripping cutting mechanism used for the vertical skidding system using balloon-cable systems is given. It is indicated that the main parameters of these mechanisms that affect their effective operation are the mass of the mechanism and the speed of its lowering to the tree crown. The method of calculating the optimal mass of load-gripping cutting mechanism is given depending on the type of wood being processed and the speed of lowering. Brief recommendations for calculating mass and speed of movement with the possible use of an ascending load-gripping cutting mechanism are given

Effect of scratch direction on densification and crack initiation of optical glass BK7

It is known from nano-indentation studies that optical glass material undergoes a certain densification deformation during ductile scratching. In this study, nano-scratch experiments were conducted under different scratch directions (face-forward and edge-forward of the same indenter) and normal loads to explore the differences in densification of material in ductile removal mode. Furthermore, inherent differences in densification deformation were utilized to explore the effect of scratch direction on the crack resistance (CR) or ductile-to-brittle transition (DBT) of material under brittle removal mode. Based on quantitative evaluation of densification deformation induced by indentation and scratching, a high-temperature annealing procedure was employed to determine the changes of the scratch groove geometry and volume before and after the release of the scratch-induced densification deformation under different scratch directions (edge-forward and face-forward). The geometric parameters of scratch grooves under edge-forward and face-forward directions showed similar changes after annealing. It is found that in ductile removal mode, the densification ratio to the total scratching volume in edge-forward scratching is greater than that in face-forward scratching. It is likely that the greater densification deformation of edge-forward scratching led to stronger crack resistance and smaller tensile residual stress. Therefore, lateral cracks are more likely to initiate and propagate under face-forward scratching under brittle removal mode, which is consistent with the experimental results.

A Study on Work Hardening in the Laser-Assisted Machining of Si3N4 Ceramics under Different Material Removal Modes

In order to understand the work hardening phenomenon and mechanism of laser-assisted machining (LAM) of Si3N4 ceramics, the work hardening degree of LAM Si3N4 under different material removal modes was studied. Two sets of single-factor experiments were performed in which the laser power and the cutting depth were changed respectively. The results show that work hardening is the result of the combination of heat and cutting deformation during cutting. The work hardening degree decreases with the increase of material softening degree. When the material is removed plastically, the work hardening degree is 110–115%.

Effects of metal quantity and quality to the removal of zinc and copper by two common green microalgae (Chlorophyceae) species

SUMMARYAppearance of metals as pollutants in the environment is an increasing global problem. Microalgae as subjects of biological remediation methods may provide a cost‐effective and environmentally friendly alternative to the removal of metals during wastewater treatment. Despite the high number of data in the topic, there is still little information on how the type and the concentration of the metal affect the process of removal. In this study, correlations among the algal species, quality and quantity of metals and characteristics of metal removal mechanism were investigated at lower metal concentrations (0.2–5.0 mg L−1) during zinc and copper removal of the green algae Desmodesmus communis and Monoraphidium pusillum. Analyses of the results proved that there is a statistically significant interaction (P < 0.05) between algal species and quality and concentration of the metals, that is, they have a significant effect on the mode and extent of removal. Both metals were mainly extracellularly bound, but at concentrations of 0.2–1.4 mg L−1, intracellular proportion could exceed the extracellular adsorption. Although there were differences between the two algae, generally copper appeared in a higher intracellular proportion than zinc in the whole studied concentration range. Overall, the quality and initial concentration of the metal is decisive for the way of removal, the knowledge of which is useful for planning post treatment retention times or post treatment processes of the used biomass during wastewater treatment.

Robustness of dispersal network structure to patch loss

Network theories have been largely applied to the investigation of spatial ecology, and there is a new trend to use them to explore the responses of complex dispersal networks to patch loss. Combining both network and metapopulation approaches, we used a spatially explicit patch model to compare the robustness of networks with different heterogeneities to both random and selective patch removal. We found that species in more heterogeneous networks can persist at higher extinction-to-colonization ratios. In addition, dispersal networks with higher heterogeneity display stronger robustness to random patch loss, suggesting that previous models based on lattice- or randomly-structured networks might underestimate species extinction thresholds. However, such strong tolerance to random patch removal comes at a high cost in that these networks are extremely vulnerable to selective removal of the most connected patches (so-called keystone patches), as this removal mode directly leads to a rapid decline in the total number of links among patches. We further explored the mechanism underlying these outcomes via network analysis, and found a strong positive correlation between overall metapopulation size and the largest cluster size. Concerning ecological conservation and management, our findings suggest that future efforts should focus on considering species dispersal networks by identifying and preserving the keystone patches, and as such, optimizing the connectivity between existing habitat patches should be an effective strategy to rescue the endangered species.

Elucidating the stability of ligand-protected Au nanoclusters under electrochemical reduction of CO2

Ligand-protected gold nanoclusters are a novel class of particles that have attracted great interest in the field of catalysis due to their atomically-precise structure, high surface-to-volume ratio, and unique electronic properties. In particular, the anionic thiolate-protected Au25 nanocluster (NC), [Au25(SR)18]1−, with partially lost ligands, has been demonstrated to act as an active catalyst for the electrochemical reduction of CO2. However, the stability of this and other thiolate-protected NCs after partial ligand removal remains elusive. Using density functional theory (DFT) calculations and the recently developed thermodynamic stability model, we investigate the stability of [Au25(SR)18]1−, [Au18(SR)14]0, [Au23(SR)16]1−, and [Au28(SR)20]0 with ligand loss. Additionally, we examine the stability of the partially protected NCs upon adsorption of CO2 reduction reaction intermediates (i.e. H, CO, and COOH) on the different active sites generated after ligand removal. Our results reveal that the partially protected Au25 NC shows the highest stability compared to the other partially protected NCs in the presence of electrochemical reduction intermediates. We find that the presence of the COOH intermediate on the generated active sites stabilizes the Au25 NC almost as well as the removed ligands. Moreover, time-dependent DFT calculations and UV–Vis/Raman experiments suggest that the most probable ligand removal mode under electrochemical conditions is the one that generates S active sites, in agreement with the DFT ligand removal thermodynamic analysis. Importantly, this study demonstrates the robustness of the Au25 NC and offers a novel way to address stability of ligand protected NCs during electrocatalytic reaction conditions.

Preparation of nanotwinned cBN cutting edge by combining mechanical lapping and ion beam polishing

Nanotwinned cubic boron nitride (nt-cBN) is a promising tool material for ultra-precision cutting of ferrous metals. However, high hardness and excellent thermal stability make it difficult to obtain sharp cutting edge by using conventional methods. In this study, the factors influencing the material removal modes and edge sharpness in mechanical lapping process have been investigated, and a novel method combining mechanical lapping and ion beam polishing is proposed for achieving the sharp nt-cBN cutting edge. The results show that the material removal in mechanical lapping is mainly contributed by the transgranular ductile failure at the nanometer scale. Besides, high material hardness with a low Poisson's ratio and small impact force on the cutting edge are beneficial for obtaining sharp cutting edge. Therefore, the ion beam polishing process is adopted to sharpen the mechanically lapped cutting edge. By using a steel baffle plate with straight profile and eliminating the clearance between the baffle plate and rake/flank face with resin filler, the edge radius is observed to decrease from micrometre scale to about 60 nm. The proposed method represents a promising strategy for the preparation of ultra-sharp cutting edge with low cost and high accuracy.

A feeding-directional cutting force model for end surface grinding of CFRP composites using rotary ultrasonic machining with elliptical ultrasonic vibration

End surface grinding of carbon fiber reinforced plastic (CFRP) composites using RUM with elliptical ultrasonic vibration has been proven to be effective in improving surface quality and simultaneously decreasing cutting forces. The cutting force is considered as one of the key output variables to evaluate the machining performance of the cutting process. Investigating cutting force and its modeling development provides great help to understand the effects of input variables and material removal mechanisms of RUM end surface grinding of CFRPs with elliptical ultrasonic vibration. However, there is no investigation on modeling cutting force for this process. This investigation will, for the first time, present a mechanistic feeding-directional cutting force model for such a process. This model is developed based on the material removal mode of brittle fracture. The approaches of the modeling development start from the analysis of one single abrasive grain, including the material removal volume, the effective cutting time, the average indentation depth, and the impact grain force in one ultrasonic vibration cycle. The designed pilot experiments are performed to verify this mechanistic model. The trends of predicted cutting forces are consistent well with those of experimental results. In addition, it can be also applied for predicting the effects of input variables (including depth of cut, feedrate, tool rotation speed, ultrasonic amplitude, abrasive size, and abrasive concentration) on feeding-directional cutting forces.

Material removal behaviour in axial ultrasonic assisted scratching of Zerodur and ULE with a Vickers indenter

Compared to conventional grinding, axial ultrasonic vibration-assisted peripheral grinding (AUPG) has advantages in terms of the improved grinding quality, higher efficiency, as well as lowered brittle damages. However, the present studies on material removal mechanism of AUPG are still not sufficient which thereafter limit its application potential. This paper aims to investigate the material removal mechanism of Zerodur and ULE through scratching by using a Vickers indenter under two conditions, with (ultrasonic vibration-assisted scratching (UVS)) and without (conventional scratching (CS)) axial ultrasonic vibration-assisted scratching while the other scratching parameters are identical. The indenter's kinematic characteristic, scratched morphology, scratched groove dimensions and critical depth of cut are compared in between UVS and CS. The experimental results indicate that the dynamic contact length between indenter and workpiece for UVS is remarkable longer than that for CS, which is helpful to promote the crack interference and hence to increase the proportion of ductile material removal mode, resulting in the diminishment of brittle fracture size in UVS. The propagation direction of median cracks in CS are relatively consistent, while in UVS the periodic varied contact zone and contact force in between the indenter and workpiece could promote the cracks propagating in different orientations, and then to improve the material removals rate in UVS. Moreover, both the critical brittle-ductile transition depth of cut and critical brittle depth of cut in UVS are bigger than that in CS, meaning the material removed in UVS with a bigger ductile ratio leading to a decreased brittle damage depth. In addition, the different material removal behaviours between Zerodur and ULE are also investigated. This fundamental work lays a theoretical foundation for the technological development and broad application of hard/brittle material oriented AUPG, as well as poses a meaningful guidance for the ultrasonic vibration assisted grinding on low-expansion optical glasses.

Analytical prediction of subsurface microcrack damage depth in diamond wire sawing silicon crystal

Subsurface microcrack damage depth (SSD) in silicon wafer processed by diamond wire sawing has a great influence on the subsequent processing process and fracture strength of silicon wafer. Based on the indentation fracture mechanics, a new numerical model for predicting the SSD of silicon wafer on the basis of half-penny crack system is proposed in this paper. In this model, effect of the random distribution characteristics of size, position and tip half angle of abrasives and different material removal modes to the contour of workpiece cutting groove are all considered. Median cracks and radial cracks are regarded that propagating into one body, that is half-penny crack system. Validity of this model is verified by comparing with experimental results in the literature. From this model, the relationship between SSD and feed rate, wire speed, size of abrasives and density of abrasives on the surface of saw wire is analyzed, the critical speed ratio of feed rate to wire speed that can achieve pure ductile processing is discussed as well. The results show that using the maximum extended length of half-penny crack system as the SSD of silicon wafer is more reasonable than using the maximum extended length of median cracks as the SSD of silicon wafer. As wire speed increases, feed rate decreases, or density of abrasives on the surface of saw wire increases, the SSD will decrease. Keeping other parameters of saw wire unchanged, the size of abrasives has no significant effect on the change of SSD. Keeping the ratio of feed rate to wire speed unchanged, the SSD varies within a small range. When the speed ratio is in the range of 10.43–16, the slice surface tends to be formed by pure ductile removal of material. The results can be used to guide the optimization of diamond wire sawing process.

A mechanistic cutting force model based on ductile and brittle fracture material removal modes for edge surface grinding of CFRP composites using rotary ultrasonic machining

Rotary ultrasonic machining (RUM) has been proven to be an effective method for surface grinding of carbon fiber reinforced plastic (CFRP) composites. Cutting force is considered as the main criterion to evaluate the performance of RUM surface grinding process. The cutting force modeling is essential to better understand such a process. All reported cutting force models for RUM of CFRP are developed based on brittle fracture material removal mode (brittle mode). However, it is recently found that both ductile material removal mode (ductile mode) and brittle mode exist in RUM of CFRP. Among surface grinding processes, edge surface grinding is the mandatory and primary process to remove an amount of composite material from the workpiece edge to achieve the desired workpiece with high precision. In edge surface grinding process, cutting forces in both feeding direction and in depth-of-cut direction (being perpendicular to feeding direction) play important roles in material removal. In addition, the understandings of material removal mechanisms will greatly benefit the modeling development of cutting forces and improve the RUM process. In this study, a mechanistic model based on both ductile mode and brittle mode is developed to predict cutting forces in both feeding and depth-of-cut directions for RUM edge surface grinding of CFRP composites. A series of experiments are conducted to verify this mechanistic model. The model prediction agrees well with the experimental results under different groups of input variables.

Numerical and Experimental Analysis of Material Removal and Surface Defect Mechanism in Scratch Tests of High Volume Fraction SiCp/Al Composites.

This paper addresses a comprehensive and further insight into the sensitivity of material removal and the surface defect formation mechanism to scratch depth during single-grit scratch tests of 50 vol% SiCp/Al composites. The three-dimensional (3D) finite element model with more realistic 3D micro-structure, particle-matrix interfacial behaviors, particle-particle contact behaviors, particle-matrix contact behaviors and a Johnson-Holmquist-Beissel (JHB) model of SiC was developed. The scratch simulation conducted at scratch velocity 10 mm/min and loading rate 40 N/min revealed that the scratch depth plays a crucial role in material removal and the surface forming process. Brittle fracturing of SiC particles and surface defects become more deteriorative under a large scratch depth ranging from 0.0385 to 0.0764 μm. The above phenomenon can be attributed to the influence of scratch depth on SiC particles’ transport; the increase in the amount of SiC particle transport resulting from an increase of scratch depth raises the occurrence of particle-particle collision which provides hard support and shock for the scratched particles; therefore, brittle fracturing gradually becomes the major removal mode of SiC particles as the scratch depth increases. On the deteriorative surface, various defects are observed; i.e., lateral cracks, interfacial debonding, cavies filled with residually broken particles, etc. The von Mises stress distribution shows that SiC particles bear vast majority of load, and thus present greater stress than the surrounding Al matrix. For example: their ratio of 3 to 30 under the scratch depth of 0.011 mm. Namely, SiC particles impede stress diffusion within the Al matrix. Finally, the SEM images of the scratched surface obtained from the single-grit scratch experiments verify the numerical analysis’s results.

Modeling and experimental investigation on grinding force for advanced ceramics with different removal modes

Advanced ceramics have unique physical and mechanical properties. While its high hardness and low fracture toughness makes the surface quality difficult to guarantee, which seriously affect the performance and reliability of ceramic parts. As the main factor affecting the surface quality of advanced ceramics, grinding force needs effective prediction to facilitate the reasonable control. The removal mode of advanced ceramics, which may directly affect the grinding force, is usually regarded as plastic removal and brittle removal. In the grinding process, the removal modes are mainly related to the depth at which the abrasive cutting into the parts. Since the difference in the abrasive size is bound to cause the randomness of the cutting depth of the abrasive, it will have an effect on the removal modes and abrasive number involved in different removal modes, which in turn will result in a change in the grinding force. Consequently, critical cutting depth of ductile removal for brittle material is adopted to determine the critical size of the maximum abrasive for brittle-ductile removal of ceramic materials. Further, considering the difference of grinding wheel size, the number of abrasives both in brittle removal and plastic removal is discussed with probabilistic method. On this basis, grinding force model of a single abrasive is considered to set up the grinding force prediction model for advanced ceramic with different removal mode. Finally, the prediction model of advanced ceramic grinding force is verified by grinding force experiment.

Effect to the Surface Composition in Ultrasonic Vibration-Assisted Grinding of BK7 Optical Glass

Because of the changes in cutting conditions and ultrasonic vibration status, the proportion of multiple material removal modes are of uncertainty and complexity in ultrasonic vibration-assisted grinding of optical glass. Knowledge of the effect of machined surface composition is the basis for better understanding the influence mechanisms of surface roughness, and also is the key to control the surface composition and surface quality. In the present work, 32 sets of experiments of ultrasonic vibration-assisted grinding of BK7 optical glass were carried out, the machined surface morphologies were observed, and the influence law of machining parameters on the proportion of different material removal was investigated. Based on the above research, the effect of surface composition was briefly summarized. The results indicated that the increasing of spindle rotation speed, the decreasing of feed rate and grinding depth can improve the proportion of ductile removal. The introduction of ultrasonic vibration can highly restrain the powdering removal, and increase the proportion of ductile removal. Grinding depth has a dominant positive effect on the surface roughness, whereas the spindle rotation speed and ultrasonic amplitude both have negative effect, which was caused by the reduction of brittle fracture removal.