金刚石与磨料磨具工程

Experimental on the end face grinding stability of thin-walled CFRP circular cell

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0054

Abstract(57)

Abstract:
Objectives:
Aiming at the problem of grinding stability in the processing of CFRP circular cell honeycomb.
(Objectives: Aiming at the problem of grinding stability in the processing of CFRP circular cell honeycomb. )

Methods:
taking a single thin-walled CFRP circular cell as the research object, the end face grinding experiment was carried out by defining the exit angle and interaction angle of grinding considering its structural characteristics. Based on the relationship between interaction angle of grinding and exit angle, the effects of grinding speed, feed rate and grinding depth on grinding stability were further analyzed.
（Methods: taking a single thin-walled CFRP circular cell as the research object, the end face grinding experiment was carried out by defining the exit angle and interaction angle of grinding considering its structural characteristics. Based on the relationship between interaction angle of grinding and exit angle, the effects of grinding speed, feed rate and grinding depth on grinding stability were further analyzed.）

Results:
The results show that the exit angle is the main factor affecting the grinding stability. When the exit angle is from 60° to 90°, the interaction angle of grinding is small and the grinding stability is poor. With the increase of grinding speed, the interaction angle of grinding increases gradually, and the grinding stability increases. With the increase of feed rate, the interaction angle of grinding has no obvious change, and the grinding stability is almost unchanged after decreasing. With the increase of grinding depth, the interaction angle of grinding decreases gradually, and the grinding stability decreases.
（Results: The results show that the exit angle is the main factor affecting the grinding stability. When the exit angle is from 60° to 90°, the interaction angle of grinding is small and the grinding stability is poor. With the increase of grinding speed, the interaction angle of grinding increases gradually, and the grinding stability increases. With the increase of feed rate, the interaction angle of grinding has no obvious change, and the grinding stability is almost unchanged after decreasing. With the increase of grinding depth, the interaction angle of grinding decreases gradually, and the grinding stability decreases.）

Conclusions:
The research results have a guiding significance for the maintenance of stability of the end face grinding of CFRP circular cell honeycomb.
（Conclusions: The research results have a guiding significance for the maintenance of stability of the end face grinding of CFRP circular cell honeycomb.）

Advance on molecular dynamics simulations of precision polishing of SiC

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0070

Abstract(60)

Abstract:
【Background】SiC has high hardness, brittleness, and chemical stability, making it exceptionally difficult to perform ultra-precision processing on its surface. This results in high processing costs, severely limiting the application and development of SiC in high-end devices. Chemical mechanical polishing (CMP) is a key technology for the planarization of SiC substrates. Currently, there is a large amount of research on CMP polishing processes, but the interaction mechanism between abrasives and chemicals in the solvent and the SiC surface is not clear. Molecular dynamics (MD) simulation, based on Newton's motion law and quantum mechanics principles, is a simulation method used to reveal the interaction between microstructure and properties of substances. It is widely used in the study of the removal mechanism of SiC surfaces.
【Content】The article first summarizes the current mainstream chemical mechanical polishing methods and their enhancement methods. Then, it analyzes the commonly used potential functions in MD simulations of SiC precision polishing, and summarizes their application areas in SiC chemical mechanical polishing based on the characteristics of potential functions. Finally, the existing research on MD simulation of SiC chemical mechanical polishing is integrated and analyzed, summarizing the removal behavior of abrasives on the SiC surface and the mechanism of adsorption and oxidation of solutes and solvents in the polishing liquid on the SiC surface, and prospects for future research directions in SiC chemical mechanical polishing.
【Current Status】The results indicate that mature simulation methods have been developed for mechanical behaviors in SiC CMP MD simulations, particularly in simulating abrasive-SiC surface interaction mechanisms and mechanical properties. The Tersoff potential, as the most classical description of the interaction between silicon and carbon atoms, can well describe the mechanical behavior of SiC and is used to study the mechanical properties and structural changes of SiC. The ABOP potential function is suitable for describing the atomic interactions of SiC materials.The Vashishta potential function is mainly used to simulate the deformation of 3C-SiC ionic bonds and covalent bonds. ReaxFF reactive force field, because it can support the formation and fracture of chemical bonds, is often used to study the chemical reactions and adsorption behavior of SiC surfaces. MD simulation of SiC substrate precision polishing is mainly divided into three categories: SiC material properties, abrasive grinding, and SiC surface chemical reactions. At present, most research focuses on the mechanical behavior between abrasives and SiC surfaces, with relatively few studies on chemical reaction mechanisms.
【Prospects】Currently, there are still many unclear issues in the CMP mechanism of SiC materials. Molecular dynamics simulations can be used to study the interaction mechanisms between liquids, oxides, and surfaces in chemical mechanical polishing, such as charge transfer and surface adsorption. In the future, the focus of research will be on using ReaxFF reactive force fields to study the reaction mechanisms of SiC under various conditions through molecular dynamics simulations, building more potential functions to adapt to different polishing conditions, and establishing comprehensive models considering the effects of multiple factors on surface interactions.

Effect of heat treated tungsten interlayer on microcrystalline diamond coatings

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0063

Abstract(36)

Abstract:
Objectives: Microcrystalline diamond coatings have extremely high hardness and excellent wear resistance, but its application field is limited by poor tribological and binding properties. To improve the tribological properties of microcrystalline diamond coatings on cemented carbide substrates, we have chosen tungsten metal as the interlayer material and constructing microscopic texture by heat treatment on the surface of tungsten interlayer.

Methods: We used evaporation method to deposit a tungsten interlayer on the surface of cemented carbide, and heat treated the tungsten interlayer in a reducing atmosphere mixed with argon and hydrogen gas. After heat treatment for 30 minutes at various temperatures (700 / 800 / 900 / 1000 °C), the effects of different heat treatment temperatures on the composition, morphology, and microstructure of the tungsten transition layer were studied using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Diamond coatings were deposited using hot filament chemical vapor deposition (HFCVD) method on substrates without any treatment and tungsten interlayers which were teated by different temperature. The substrate temperature was controlled at 800 ± 50 ℃, and the growth time was 6 hours. Analyze the morphology and quality of diamond coatings using SEM, X-ray diffraction, and laser Raman spectroscopy. Using the reciprocating friction and wear tester, Si₃N₄ ceramic balls were subjected to reciprocating friction with diamond coatings for 120 minutes to evaluate the friction performance of each coating sample.

Results: The results show that the tungsten interlayer deposited by vapor deposition exhibits an amorphous structure, and the crystallinity of the tungsten interlayer significantly increases after heat treatment. Cracks are generated on the surface of the interlayer, and different sizes of "island - gully" structures are formed. The crystallinity of the tungsten interlayer after heat treatment at 700~800 ℃ is not good, and the surface has larger "islands" and narrower "gully". The structure size of the tungsten interlayer after heat treatment at 900 ℃ is more moderate. The tungsten interlayer after heat treatment at 1000 ℃ has the best crystallinity and the smallest size of "islands". The SEM surface morphology, X-ray diffraction patterns, and Raman spectroscopy show that the diamond grown on the substrate surface without tungsten transition layer has the largest average grain size and uneven grain size distribution. The crystallinity and content of diamond coatings grown on the tungsten interlayer during heat treatment are better, which was reflected in the higher diffraction intensity of diamond peak in the X-ray diffraction spectrum and the narrower full width at half maximum (FWHM) of diamond peak in the Raman spectrum. The grain size of diamond shows a trend of first decreasing and then increasing with the increase of heat treatment temperature, but all are smaller than the sample without tungsten interlayer. The friction and wear results indicate that the diamond coating grown on the tungsten interlayer after 700 ℃ heat treatment has large drop. The diamond coating on the tungsten interlayer after heat treatment at 800~1000 ℃ ensures good bonding performance while improving friction performance in varying degrees. Among them, the diamond coating grown on the tungsten interlayer after 900 ℃ heat treatment has the smoothest wear mark, with an average friction coefficient as low as 0.062, and the corresponding Si₃N₄ friction pair has the smallest wear mark diameter and wear rate.

Conclusions: The tungsten interlayer and its "island - gully" structure after heat treatment can significantly improve the growth and crystal state of diamond, resulting in grain refinement and improved friction properties. The surface of the tungsten interayer treated at 900 ℃ for 30 minutes has a moderately sized "island-gully" structure and the best uniformity. The average grain size of the diamond coating grown on it is about 1.97 μm. The maximum and average friction coefficients are as low as 0.217 and 0.062, and the wear of friction pair is only 19.2% of the sample without tungsten interlayer.

Effect of TiH₂ addition on the grinding performance of Cu₃Sn intermetallic compound diamond wheels

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0261

Abstract(60)

Abstract:
In order to improve the sharpness and shape retention of Cu₃Sn intermetallic compound diamond grinding wheels, Cu₃Sn ball-milling powders, diamond grinding blocks and grinding wheels with different TiH₂ additions were prepared. The effects of TiH₂ addition on the grinding performance of Cu₃Sn intermetallic diamond grinding wheels were investigated by testing and analyzing the micro-morphology, oxygen content, physical phase composition, thermal effect, mechanical properties. The results show that the addition of TiH₂ has the effect of inhibiting the oxygenation of Cu₃Sn ball-milling powder, which is beneficial for the sintering of the powder. When the amount of TiH₂ added is 2.0wt%, the oxygen content decreases from 0.67% to the minimum value of 0.51%. The addition of TiH₂ improves the holding force of the matrix on the diamond, which can improve the flexural strength and hardness; when the amount of TiH₂ added is too much, the flexural strength and hardness will decrease instead. When the amount of TiH₂ is 1.5wt%, the flexural strength reaches the maximum value of 80.74 MPa, and the Rockwell hardness reaches the maximum value of 109.88 HRB when the amount of TiH₂ is 2.0wt%. The addition of TiH₂ can improve the grinding performance of the wheel, and also improve the sharpness and shape retention. When grinding cemented carbide YG8, the fastest feed rate of the grinding wheel increases from 0.02 mm/feed to 0.035 mm/feed. And the grinding ratio reaches a maximum value of 172.03 with addition of 2.0wt% TiH₂, compared with 51.09 of blank sample.

Tribological Performance of Alternating Multilayer Diamond Films on Si3N4 Ceramic Substrates

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0269

Abstract(46)

Abstract:
To avoid failures such as friction and wear of silicon nitride(Si₃N₄), Single-layer diamond films and Multi-layer diamond films were deposited on silicon nitride substrate by HOT FILAMENT CHEMICAL VAPOR DEPOSition. The nucleation, film quality, diamond surface and cross-sectional morphology, and surface roughness of the diamond films were characterized using X-ray Diffraction(XRD), Scanning Electron Microscopy(SEM), Atomic Force Microscopy(AFM), and Raman Spectroscopy(Raman). The friction and wear properties of different structural thin films were studied by the "ball disc" reciprocating friction and wear testing machine. The results show that multi-layer diamond films exhibit better tribological properties than single-layer diamond films. When the number of alternations is 4(the number of multilayer layers is 8), the friction coefficient and wear rate are the lowest, with values of 0.016 and 1.042×10^-7 mm³·N^-1·m^-1; but as the number of layers in the multi-layer structure increases, the interlayer thickness decreases, and the films rupture and peel off during the friction process; the bonding strength between the film and the substrate decreases, the quality of the film decreases, the friction coefficient increases to 0.042, and the wear rate increases to 4.661×10^-7 mm³·N^-1·m^-1, the friction and wear properties of films decreases.

Prediction and Optimization of Robotic Machining Grinding Force based on Neural Network-Genetic Algorithm

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0045

Abstract(51)

Abstract:
Objectives:In this paper, the grinding force signal of industrial robot processing sandstone is studied and analyzed, and the influence of processing parameters on the grinding force signal of different processing directions is explored, the prediction model of grinding force is established by BP neural network, and the optimization of grinding process parameters is carried out based on genetic algorithm with grinding force as constraint condition and material removal rate as objective function, it provides reference for the selection of technological parameters of industrial robot grinding process.Taking KUKA KR60L30HA industrial robot processing sandstone as an example, the grinding force prediction and grinding process parameter optimization were studied based on BP neural network and genetic algorithm.

Methods: Firstly, the orthogonal test method is used to analyze the influence of the processing parameters on the grinding force. Secondly, the grinding force model is trained and predicted based on BP neural network. Finally, the grinding process parameters are optimized by the genetic algorithm.

Results:The conclusions are as follows: (1) The influence of grinding process parameters on the grinding component and grinding force is increasing with the increase of radial cutting depth a_e, axial cutting depth a_p and feed speed v_w. With the increase of spindle speed n, the grinding force decreases. (2) The model established based on BP neural network has good prediction accuracy and stability, which meets the prediction requirements. (3)The optimized grinding process parameters obtained by genetic algorithm are radial tangential depth a_e=2.01mm, axial tangential depth a_p=2.59mm, spindle speed n=9910.37r/min and feed speed v_w=3116.06mm/min, and the material removal rate is R_MMR=16221.90mm³ / min.

Conclusions:(1) the influence of grinding parameters on grinding components and grinding resultant force is different in the order of feed velocity vw, radial cutting depth AE and axial cutting depth AP. The grinding force increases with the increase of AE, AP and VW, and decreases with the increase of spindle speed N. (2) BP neural network is trained and forecasted with orthogonal experiment data. The neural network model has good precision and stability, and meets the requirement of prediction. (3) with the reciprocal of material removal rate RMMR as the objective optimization function, the process parameters were obtained as radial cutting depth AE = 2.17 mm, axial cutting depth AP = 1.54 mm, spindle speed n = 9909.52 r/min, feed speed VW = 3395.25 mm/min, the material removal rate rmmr = 11346.25 mm3/min.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0252

Abstract(67)

Abstract:
Titanium plating on the surface of diamond powder can improve its wettability to the bonding agent, and the preparation process of titanium plated metal layer is of great significance to the industrial application of diamond powder. The effects of different titanium powder particle sizes (60 mesh coarse powder and 325 mesh fine powder) and raw material ratios on the process of vacuum and protective atmosphere titanium plating on the surface of diamond powders were compared. The chemical composition of the titanium coated diamond powder surface was characterized by XRD as diamond, Ti and TiC transition layer, and the morphology of the titanium coated diamond powder and the distribution of surface elements were analyzed by SEM, which showed that Ti coating on the surface of diamond particles could be achieved with different ratios and Ti powder particle sizes. The Raman spectra of fine Ti-coated diamond contain characteristic peaks of diamond and Ti, while the Raman spectra of coarse Ti-coated diamond and Ti-coated diamond synthesized in vacuum atmosphere are affected by the ratio of raw materials. The UV-visible absorption spectra showed that the Ti-coated diamond had obvious absorption peaks in the wavelength region of 228-234 nm and 328-350 nm, respectively. The weight loss rates of vacuum synthesized titanium-coated diamond and fine-grained Ti-coated diamond were lower than those of coarse-grained Ti-coated diamond. Combined with the results of Raman spectroscopy, ultraviolet absorption spectroscopy and thermal analysis, the performance of fine Ti coated diamonds under argon atmosphere protection is better than that of coarse Ti powder coated diamonds and vacuum atmosphere coated diamonds.

Characterization of flow field for chemical-mechanical polishing of silicon carbide under ultrasonic action

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0273

Abstract(50)

Abstract:
To overcome the challenges of low polishing efficiency and poor surface quality in silicon carbide polishing, researchers have employed an ultrasonic-assisted chemical mechanical polishing (CMP) process. This study focuses on investigating the impact of ultrasonic assistance on the flow field during the polishing process. The goal is to achieve smooth and damage-free polishing of silicon carbide surfaces. This study involves analyzing the properties of the polishing flow field under ultrasonic vibration. Fluid dynamics equations and energy conservation principles are utilized to understand these characteristics. Additionally, finite element analysis is employed to investigate the key factors that influence polishing efficiency in the flow field, including ultrasonic frequencies, amplitudes, and film thicknesses. The results show that ultrasonic vibration has a significant promoting effect on the polishing flow field, guiding the flow field to produce significant lateral shearing flow to enhance the overall polishing efficiency. The effects of ultrasonic action on the flow field vary with different film thicknesses. Analysis of simulation results indicates that as the film thickness decreases from 50μm to 30μm, the maximum velocity of the flow field increases from 84.28m/s to 105.68m/s, and the maximum pressure increases from 199.2MPa to 581.9MPa. It is evident that a smaller film thickness is more conducive to improving the polishing efficiency.

Parameter calibration of a discrete element simulation model for dry lightweight heterogeneous media

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0016

Abstract(21)

Abstract:
In order to realize the discrete element simulation of dry light shaped particle medium in the process of rolling grinding, in this paper, walnut shell particle medium was taken as the research object, the multi-dimensional method is used to divide the light medium with different shapes , and different types of shaped particle media were constructed , the discrete element simulation parameters are calibrated by the combination of physical experiment and simulation. First of all, the intrinsic parameters (density, elastic modulus and shear modulus) of walnut shell particle medium were measured by physical tests. The static friction coefficient、rolling friction coefficient and collision recovery coefficient between walnut shell particle medium and acrylic are 0.422、0.175 and 0.246, respectively, and the collision recovery coefficient between walnut shell particle medium is 0.340. Secondly, the range of static friction and rolling friction coefficients between granular media is determined based on EDEM embedded GEMM database, and the two-factor five-level rotational orthogonal combination simulation test was carried out, The second-order regression equation of accumulation Angle and friction coefficient was established, aiming at physical accumulation Angle 44.64°, the regression equation was optimized and solved, and the best combination was obtained: The coefficient of static friction between granular media is 0.829、the rolling friction coefficient is 0.191. Finally, by setting the different lifting speed of the baffle, the verification experiment of stacking Angle is carried out. The results show that the comprehensive relative error is less than 4%.It is shown that the parameter combination can be used as a discrete element simulation model parameter in the process of rolling grinding with walnut shell particle medium.

Study on the performance of brazed micronized diamond grinding head

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0025

Abstract(36)

Abstract:
In order to solve the problems of serious damage of micronized diamond during brazing and poor bonding between brazing material and substrate. A suitable brazing method was used to braze micronized diamond (325/400#) on a steel substrate. The bonding interface was analyzed and a grinding head was prepared to process the alumina ceramic plate. It was found that the micronized diamond abrasive grains were less damaged. The products at the interface between the steel substrate and the brazing material are γ-phase solid solution formed by Fe and Cr and Ni-Fe replacement solid solution formed by Fe and Ni. The presence of solid solution ensures a strong bond between the brazing material and the substrate. The prepared brazed micronized diamond grinding heads have a high service life when processing ceramic plates.

Highly efficient polishing of polycrystalline diamond via atmosphere inductively coupled plasma

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0281

Abstract(71)

Abstract:
As a typical difficult-to-machine material, sophisticated and time-consuming polishing methods are often required to smooth polycrystalline diamond. Herein, a non-contact processing method based on atmosphere inductively coupled plasma was used to successfully polish polycrystalline diamond with extremely high efficiency. During the polishing process, oxygen was added into the pure argon plasma to act as reaction gas, generating highly active oxygen radicals which would differentially etch polycrystalline diamond at different position, and finally a smooth surface of polycrystalline diamond could be obtained. Along with the radiation process of oxygen-containing plasma, the tips of grains were removed quickly and the height difference of grains decreased dramatically at the same time. Meanwhile, the Sa roughness of polycrystalline diamond could be reduced from 10.1 μm to 93.7 nm in only 30 min and the material removal rate reached up to 34.4 μm/min, much higher than conventional mechanical/chemical mechanical polishing methods. Further analysis of the composition of polycrystalline diamond indicated that no amorphous carbon or new stress were introduced into the diamond and there was also no change in the crystal plane orientation of grains for polycrystalline diamond. Therefore, this highly efficient plasma polishing method can be well used as a pre-polishing method to rapidly reduce the surface roughness of polycrystalline diamond, and combined with other precision polishing methods, significantly improving the overall polishing efficiency of polycrystalline diamond.

A Study on the Numerical Simulation of Rock Breaking by PDC Wear Teeth Cutting

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0258

Abstract(104)

Abstract:
The existing literature on numerical simulation of cutters rarely considers the effect of wear height on cutter temperature and cutting load. However, the force and thermal wear of PDC cutters deteriorate after wear, leading to rapid failure. In order to discuss this problem, based on elastoplastic mechanics and rock mechanics, the Drucker-Prager criterion was used as the rock constitutive model to establish a three-dimensional dynamic rotational simulation model of the worn teeth. The numerical simulation method was used to analyze the stress state and temperature rise amplitude of the worn teeth under the conditions of different wear heights, cutting depths and front angles. The results show that, compared with unworn teeth, the cutting load of worn teeth increases with the increase of wear height, and the maximum is reached when the wear height of the cutting teeth (diameter 13.4 mm, total height 8 mm) is 1.5 mm. The more serious the wear of the cutting teeth, the greater the force required to enter the same depth; The cutting load will increase with the increase of the front Angle. Therefore, the higher the wear height and the higher the front Angle, the higher the failure risk of the cutter. With the increase of cutter wear height, the temperature rise of cutter significantly increases, which can be increased by 54%-103% under simulated conditions.

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0019

Abstract(74)

Abstract:
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Experimental Study on Grinding Silicon Carbide with Small Diameter Diamond Grinding Wheel

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0030

Abstract(89)

Abstract:
【Objective】To achieve high-quality and low-damage grinding of silicon carbide ceramics. 【Method】 Small diameter diamond was used to conduct grinding experiments on silicon carbide ceramics. Based on the actual morphology characteristics of the grinding wheel and current grinding theory, a model for the maximum undeformed chip thickness of the abrasive particles and a model for the depth of subsurface damage were established. The influence trend of grinding cutting thickness on grinding quality, grinding force, and subsurface damage was analyzed to verify the accuracy of the model. Finally, combined with finite element simulation, the influence of the maximum undeformed chip thickness of abrasive particles on the surface forming mechanism of silicon carbide ceramics during grinding is further revealed. 【Result】 Considering full contact between the grinding wheel and the material surface, when the grinding wheel has a linear speed of 5.23m/s, a feed rate of 10mm/min, and a grinding depth of 20 μ When m is reached, the surface roughness of the workpiece reaches its minimum, which is 0.3865 μ m. And at this time, the sub surface damage depth of the grinding force workpiece also reaches the lowest, only 4.959 μ M; When the grinding wheel has a linear speed of 3.41m/s, a feed rate of 40mm/min, and a grinding depth of 30 μ At m, the maximum grinding force is 9.35N, and the residual height of the surface groove reaches the minimum, only 4.85 μ m. The surface roughness and sub surface damage of the workpiece reach their maximum, with Ra=0.7641, respectively μ M and 7.453 μ M. Comparing the calculated sub surface damage depth of the LI model with experimental values, the maximum error is 16.04%, and the error of other results is less than 15%. 【Conclusion】 The maximum residual height of surface grooves is not only related to grinding force, but also to the number of abrasive particles involved in grinding. It decreases continuously with the increase of grinding wheel feed rate, linear speed, and grinding depth; The surface roughness and sub surface damage are mainly related to the grinding thickness and grinding force, and their changing trends are the same. They increase with the increase of the grinding wheel feed rate and grinding depth, and decrease with the increase of the grinding wheel linear speed. In order to obtain good surface quality after processing, it is necessary to increase the grinding wheel linear speed, reduce the feed rate and grinding depth. The grinding thickness model and LI sub surface damage model are basically correct and have the same trend as the experimental data. Under the selected grinding process parameters in the experiment, the actual grinding thickness of the abrasive particles is within the range of [-31.86%, 13.95%] of the critical chip thickness of silicon carbide ceramics, indicating that the material removal method falls between plastic removal and brittle removal. This proves that controlling the maximum undeformed chip thickness of the abrasive particles can remove the plastic domain of the experimental material and reduce the subsurface damage caused by grinding.

Study on the influence of orderly arrangement on grinding force in diamond roller dressing process

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0004

Abstract(146)

Abstract:
The diamond roller plays a crucial role in the formation and dressing of grinding wheels, with its abrasive wear being a significant factor that affects both the roller's lifespan and the quality of dressing. Effective arrangement of abrasive particles can help reduce this wear. However, current research primarily focuses on studying the impact of abrasive layout on single-layer grinding wheels, which limits its applicability to abrasive accumulation grinding wheels. This paper investigates how the arrangement of abrasive grains influences the process of dressing a grinding wheel. By employing finite element simulation and experimental verification during the forming and dressing processes using three types of roller arrangements (dislocation, array, and phyllotactic pattern), we evaluate their effects on grinding force as our main indicator. Our findings reveal that during the wheel dressing process, regular particle arrangement significantly impacts grinding force; specifically, array arrangement results in higher forces compared to dislocation arrangement while phyllotactic pattern yields lower forces. Furthermore, when compared to dislocation and array arrangements, phyllotactic pattern arrangement effectively reduces abrasion on the roller surface while enhancing both dressing performance and service life.

, Available online , doi: 10.13394/j.cnki.jgszz.2024.0013

Abstract(132)

Abstract:
The grinding process of hardened mold steel can result in variations in grinding forces due to changes in machining depth, leading to unstable machining conditions. Therefore, utilizing single-point grinding with large-grain diamond, based on the analysis of the surface morphology characteristics of the machining surface, the dynamic properties and stability of the grinding process are investigated. The aim is to explore the mechanism of the effect of process parameters on machining efficiency and surface quality, with the goal of achieving high-efficiency and high-quality grinding. Firstly, the single-point diamond grinding system is dynamically modeled, and then the grinding vibration signals are measured using an accelerometer for modal analysis of the working system. The natural frequency and damping ratio of the machining system are solved. Next, based on the characterization data of surface waviness and roughness, a digital clustering analysis is performed to correlate the feed depth and wheel speed with the stable machining state. This is matched with the stability lobes diagram of grinding to fit the stiffness of the machining system and the coefficient of grinding force. Thus, a real-time controllable grinding process stability is established by controlling the feed depth and wheel speed. Finally, the grinding experiments on mold steel are conducted to validate and analyze the machining efficiency and quality. The results demonstrate that the modal analysis of the grinding process, along with the clustering matching of the surface morphology characteristics, can effectively map the machining process parameters within the stable domain of the grinding process. Within the stable domain of grinding, using a higher material removal rate can reduce the average surface waviness from 1.203 μm to 0.635 μm, and the average surface roughness from 0.267 μm to 0.143 μm. Moreover, under the same material removal amount, the average surface roughness of stable domain grinding can be reduced by 74% compared to unstable domain grinding. Therefore, by adjusting the feed depth and wheel speed in real-time based on the characterized stable domain of grinding during the machining process, it is possible to simultaneously improve the machining quality and efficiency.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0272

Abstract(175)

Abstract:
As a crucial area of aircraft engine blades, the precision of the blade edge directly affects the aerodynamic performance of the blades. Reducing the surface roughness and improving the contour of the blade edge are crucial for enhancing the engine's service life. Therefore, this study designed and developed resin-bonded diamond polishing wheels, investigating the polishing process of blade edges based on a robotic platform. Orthogonal experimental design was employed to explore the impact of four main process parameters (spindle speed, feed rate, processing pressure, abrasive particle size) on the surface roughness and contour of the blade edge. The experiments determined the optimal combination of process parameters: spindle speed at 800 r/min, feed rate at 6 mm/min, processing pressure at 4 N, and abrasive particle size ranged between 10 to 14 μm. With this parameter combination, the polishing effect on the workpiece was significantly improved. The surface morphology was enhanced, the surface roughness of the blade edge decreased from the initial 1.165 μm to 0.243 μm, and the contour reduced from the initial 0.048 mm to 0.016 mm, meeting the usage requirements.

Preparation and propertiesof intermetallic-bonded diamond grindingwheel for thinning silicon carbide wafers

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0250

Abstract(266)

Abstract:
Compared with silicon based materials, silicon carbide has become an ideal substrate material for chip manufacturing due to its good thermal conductivity, breakdown electric field strength, and high bandgap width. However, the Mohs hardness of silicon carbide wafers is as high as 9.5. Realizing the grinding process of silicon carbide single crystal wafers, reducing grinding costs, and improving the processing quality of silicon carbide wafers has become an urgent problem to be solved in the semiconductor industry. This article uses Cu₃Sn and Cu₆Sn₅ intermetallic compounds as bond to prepare rough and fine grinding diamond wheels for silicon carbide wafers. The experimental research results show that this diamond grinding wheel is suitable for grinding SiC single crystal wafers, the wear ratio of the prepared 2000# diamond rough grinding wheel for grinding 6-inch silicon carbide wafers is 1: 5, the surface roughness of the silicon carbide wafer is 11nm; The wear ratio of the 12000# diamond fine grinding wheel is 1: 0.6, the surface roughness is 2.076 nm, and the TTV is less than 3 µm. The grinding performance is good and can meet the needs of industrial production.

Numerical simulation investigations into the effect of machining parameters on the cutting process for ZrO2 ceramics

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0188

Abstract(194)

Abstract:
The three-dimensional cutting process of ZrO₂ ceramics was simulated using the finite element simulation method. By studying the chip removal mechanism, dynamic changes and distribution of stress, and changes in cutting force of workpiece materials, it was found that with the increase of machining depth, the stress on the workpiece gradually increases, and the stress layer on the tool surface also gradually expands and increases towards the front and back cutting surfaces. In addition, the cutting force will gradually increase. The stress and cutting force fluctuate with the increase of cutting speed, but there is no obvious change on the whole. The radius of edge circle will affect the formation of crack at the initial stage of cutting, With the increase of the radius of the cutting edge, the crack length at the front of the cutting tool will become shorter, but the effect of cutting force is not obvious. When cutting with negative rake angle of cutting tool, it will not cause cracks in the ceramics and obtain better machining quality. The maximum cutting force increases rapidly when the tool rake angle is 0°. With the increase of tool rake angle, the change of cutting force is not obvious.

Simulation study of cutting fluid flow field in kerf of fine diameter diamond wire saw

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0235

Abstract(439)

Abstract:
Diamond wire saw is widely used in the field of chip processing of hard and brittle materials such as monocrystalline silicon and sapphire. With the large size of the chip and the fine line of the sawing wire, the kerf is more and more "deep and narrow" in the sawing process, and the cutting fluid plays a full role in the sawing process, which has a great impact on the quality of the slice. Based on the numerical simulation of computational fluid dynamics, the cutting fluid flow field in the kerf of diamond wire saw was analyzed and studied by establishing the CFD kerf model. The simulation analysis found that: in the small size kerf, with the increase of wire speed to more than 25m/s, the cutting fluid can more fully enter the kerf, after the sawing wire and the workpiece contact area and non-contact area filled with liquid, the fluid pressure in the contact area is about 0.179MPa, the fluid pressure in the non-contact area is about 0.159MPa; The reduction of the viscosity and surface tension of the cutting fluid in a certain range is conducive to ensuring the relative saturation and stability of the cutting fluid in the kerf, and the pressure distribution of the cutting fluid in the kerf is more stable.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0267

Abstract(196)

Abstract:
The NVH problem of electric vehicles requires a revolution in gear precision machining technology. Abrasive flow machining is one of the effective methods for polishing complex surfaces such as gears, and fixture design is a crucial part of the abrasive flow machining process. In the process of optimizing the design of abrasive flow fixtures, the selection of physical models contradicts the accuracy of simulation results and the computational expense of simulation. Different viscosity media were selected, and simulation experiments were conducted using different viscosity models and flow models. The fluid pressure distribution, velocity vector, wall shear, and streamline distribution cloud maps reflecting machining uniformity were analyzed to explore the steady-state simulation results of abrasive flow in the slit model. It was found that the distribution trend of simulation results from different physical models has strong similarity, which can achieve consistency in the processing area streamline in the simulation results, proving the feasibility of replacing complex physical models with simple physical models for fixture optimization simulation. By applying simulation results and using the simplest Newtonian fluid - water as the medium, and utilizing the streamline distribution in the machining area, the design optimization of the gear shaft abrasive flow fixture was carried out, achieving the removal of gear “ghost frequencies” after abrasive flow machining.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0164

Abstract(658)

Abstract:
In this paper, A variety of non-stoichiometric (Ti, Nb)C_x PCD tool binders were prepared by mechanical alloying (MA) of TiC and transition metal Nb. The phase composition of the sintered composite was detected by X-ray diffractometer (XRD), and the composite was treated and analyzed by jade software. The fracture morphology of the composites was observed by scanning electron microscope (SEM), and the hardness and fracture toughness of the composites were measured by Vickers hardness tester. The results show that in the range of 1300 ℃ to 1700 ℃, the higher the sintering temperature, the higher the degree of solid solution of TiC and Nb. Under the same sintering temperature, the hardness of (Ti, Nb)C_x composite gradually increases with the increase of metal Nb proportion. Under the same metal Nb proportion, the higher the temperature, the higher the degree of solid solution of Nb and TiC. Among them, the mechanical properties of composite material (Ti, Nb) C_0.5 are the best, and the best hardness of (Ti, Nb) C_0.5 composite material is 23.0 GPa and the fracture toughness is 7.20 MPa·m^1/2 at 1600 ℃.

Research Status of Thermal Damage Inhibition Technology for Diamond

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0166

Abstract(361)

Abstract:
The thermal damage of the diamond during the preparation process of diamond tools mainly included diamond graphitization, diamond breakage and cracking, and chemical erosion of diamonds. In response to the thermal damage of the diamond, this article introduced the current suppression technologies for diamond thermal damage from three aspects: surface coating of diamonds, adjustment of matrix material properties, and optimization of forming technology. The article also provided prospects for future research directions to provide reference and guidance for the preparation of high-performance diamond tools.

Simulation and experimentalanalysis of composite chamfering of superhard cutting toolsbased on edge grinding technology

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0223

Abstract(209)

Abstract:
In order to improve the phenomenon of chip accumulation during the processing of arc edge chamfered PCD turning tools, reduce tool wear during processing, and improve their processing performance, a secondary chamfering treatment is carried out on the basis of arc edge chamfered turning tools to form a composite chamfering structure. In CATIA software, based on the actual process of grinding PCD chamfered cutting tools using the grinding machine CORBENR RG9, a three-dimensional model of the cylindrical back face composite chamfered turning tool is established. Then, the Deform V11.0 software is used for 3D cutting simulation analysis of the PCD composite chamfered turning tool.And based on the simulation analysis results, a comparative analysis was conducted on the cutting experiments of PCD composite chamfer turning tool and PCD first-order chamfer turning tool.The results show that when the cutting depth is smaller than the first order chamfer width, the second order chamfer width should be greater than the cutting depth; When the cutting depth is close to the first order chamfer width, the second order chamfer width should be smaller than the cutting depth. When the cutting depth is small and does not exceed the second order chamfer area, choose a larger second order chamfer angle; When the cutting depth is large, choose a smaller second order chamfer angle.At the same cutting depth, the cutting temperature of PCD composite chamfer turning tool is lower than that of PCD first-order chamfer turning tool. When the cutting depth is 0.14mm, as the cutting time increases, the surface roughness of the parts processed with PCD composite chamfered turning tools is smaller than that of PCD first order chamfered turning tools; Comparing the tool wear morphology after 30 minutes of processing, it was found that the PCD composite chamfered turning tool had less wear.

Study on Physicochemical Properties and Removal Mechanism of SiC Ceramics Processed by Femtosecond Laser

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0088

Abstract(318)

Abstract:
Ultrafast laser processing of hard and brittle materials can effectively suppress processing damage and obtain a balance of processing quality and efficiency. In this paper, a femtosecond laser was used to process silicon carbide ceramics at different energy densities and pulse numbers to investigate the effects of laser parameters on surface morphological features, chemical components and microporous quality, and to analyze the evolution of surface microstructure and material removal processes. The results show that the boiling and melting zones are formed on the surface of silicon carbide ceramics by single-pulse processing, and the threshold energies for the formation of characteristic zones are calculated to be 3.779 J/cm² and 0.86 J/cm², respectively; the removal process of silicon carbide ceramics is the result of photothermal and photochemical effects successively, and the mechanism of action in the central region with higher temperature is the evaporation of the material, while the low temperature region is the thermal decomposition of the material The microporous diameter and ablation depth increase with the increase of energy density and number of pulses. This study further improves the mechanism of femtosecond laser processing of silicon carbide ceramics from the perspective of material physiochemical property changes, and provides a theoretical reference for efficient and precise processing applications of silicon carbide ceramic parts.

Simulation and experimental study on micro-cutting silicon carbide crystal with single grain diamond

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0158

Abstract(369)

Abstract:
In order to improve the brittle fracture and edge breakage of silicon carbide crystal in the micro-cutting process, a finite element simulation model of micro-cutting silicon carbide workpiece with diamond conical abrasive grain was established, and the selection range of micro-cutting depth and speed is determined through the pre-simulation model. Then the orthogonal experiment method is used to analyze the primary and secondary factors on the cutting force. Subsequently, the influence of single micro-cutting parameter on cutting effect is studied. Finally, with the help of Hertzian contact stress, the cutting force and quality of cutting edge were analyzed by scratching the silicon carbide crystal with a diamond tip. The maximum cutting depth is determined to be 1.5 μm by pre-simulation model. The cutting depth B is a significant factor affecting the main cutting force, cutting speed C and conical angle of diamond grain A are non-significant factors, and the optimal scheme of cutting parameters is B₁C₁A₂ (cutting depth 0.5 μm, cutting speed 76 m/s, conical angle of diamond grain 60°). It can improve the cutting stability by controlling the cutting depth, and appropriately improve the cutting speed can improve the cutting efficiency and ensure the cutting quality. The depth of pressing into the workpiece of diamond tip affects the friction coefficient, friction force and cutting force, and the 3D profiles of cutting edges are relatively clear, straight and clean.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0046

Abstract(236)

Abstract:

Effect of Lapping Pressure on Surface quality of polycrystalline diamond （Shandong Institute of Scientific and Technical Information, Jinan , 250101,China ,SUN Guodong）

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0036

Abstract(302)

Abstract:
The diamond layer of polycrystalline diamond (PCD) composite was grinded by a diamond flat grinding disc at high speed. The change of the removal rate of polycrystalline diamond material and the surface quality (surface roughness, surface morphology) of the specimen were analyzed by changing the pressure during grinding. The results show that the increase of grinding pressure will improve the material removal rate of polycrystalline diamond, reduce the surface roughness, increase the surface smooth area, and reduce the pits and gap cracks.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0129

Abstract(170)

Abstract:
In order to reduce the difficulty of cuttings migration in horizontal wells, the problem of bit bagging. Improve the drilling efficiency and service life of PDC drill bit in the process of shale horizontal well drilling. The numerical simulation method and the low Reynolds number k-ԑ turbulence model are used to establish the bottom hole flow field model. The hydraulic structure of the PDC (polycrystalline diamond compact) bit is analyzed under the conditions of different drilling fluid displacement, PDC bit rotation speed and cuttings particle size. The results show that: with the increase of displacement, cuttings efficiency increases gradually. However, in the rotating condition, the mismatch between the drilling fluid displacement and the drill bit speed reduces the drilling fluid scour and cuttings migration efficiency. Appropriate displacement and rotational speed can effectively improve the cuttings migration efficiency and reduce the accumulation of cuttings at the bottom of the well. Under a certain bit rotation speed and drilling fluid displacement, the particle size of cuttings is directly proportional to the cuttings migration efficiency. The research results can provide reference for optimizing the design of PDC bit and drilling construction parameters.

Prediction of grinding surface roughness of Al2O3-based insulating coating on bearing surface considering the change of grinding wheel surface morphology

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0118

Abstract(217)

Abstract:
To improve the prediction accuracy of grinding surface roughness of Al2O3-based ceramic insulating coating on bearing surface, a BP neural network prediction model was established which was consistent with the actual machining process. A method for measuring grinding wheel surface and quantifying abrasive particle characteristic parameters was proposed based on the principle of spectral confocal. A neural network prediction model for workpiece surface roughness was established, which took characteristic parameter K of grinding wheel surface, grinding wheel speed ω, workpiece feed speed υ, cutting depth ρ and normal grinding force F as input parameters. The model could directly reflect the time-varying state of grinding wheel surface. Finally, the prediction performance of the network was verified by the known grinding samples and the four groups of unknown test samples after grinding wheel passivation. For the known samples, the roughness predicted by BP network is consistent with the actual roughness, and the network output error is less than ±0.04μm. Further using the network for the grinding wheel after passivation to predict the unknown grinding test samples, the accuracy of the network prediction decreases, and the maximum error percentage is less than 20%. The neural network, which includes the characteristic parameters of abrasive particles on grinding wheel surface, can be used to predict the workpiece roughness of Al2O3-based ceramic insulation coating on bearing surface under the transient state of abrasive wear of grinding wheel, and the network has a certain generalization ability for unknown samples.

Analysis and optimization of traveling wave of large diamond core drill bit

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0137

Abstract(213)

Abstract:
For the vibration and noise issues that occur during drilling of large diamond core drill bits, modal analysis was conducted using Ansys Workbench finite element software on core drill bits without openings, openings, interlayers, and installation of positioning wheels. Furthermore, the resonance margin/δ of core drill bits was calculated using traveling wave vibration theory to analyze the effect of avoiding traveling wave resonance. Study the influence of openings and interlayers on traveling wave vibration. The results show that when the drilling speed is 186.72 r/min, the δ of the no opening core drill bit is 0, and a backward traveling wave resonance occurs. In the area where there is a large deformation of the inherent mode of traveling wave resonance in the no opening core drill bit, the δ of opening 8 sets of circular holes (3 in each group) and 8 S-shaped holes in the core drill bit is 4.97%, which avoids traveling wave resonance effectively; The δ of the opening and sandwich core drill bit is 5.72%, which has the best effect of avoiding traveling wave resonance. In order to improve the accuracy of machining holes, positioning wheels are installed around the core drill bit, and the impact of the number of positioning wheels on traveling wave vibration is analyzed. Among them, the δ of installing 6 and 12 positioning wheel core drill bits is 4.27% and 4.47%, respectively, to avoid traveling wave resonance. Comparing the δ of 2 to 12 positioning wheel core drill bits and considering installation convenience, the optimal number of positioning wheels for installation is finally determined to be 6.

Preparation of diamond coated floating core and its application in copper pipe production

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0138

Abstract(196)

Abstract:

On-linediscrimination of diamond roller profile state

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0148

Abstract(271)

Abstract:
Diamond roller profile grinding is one of the key technologies for manufacturing diamond rollers. Currently, diamond grinding wheels are commonly used for precision profile grinding of diamond rollers. The surface contour Pv value of the diamond roller is an important indicator for assessing the profile grinding process. In current machining inspections, workers often need to stop the machine, remove the roller, and place it on a contour gauge for measurement, which significantly increases the time and cost of roller production. Therefore, this paper proposes an online detection method based on wavelet packet coefficients and random forest for the vibration signals generated during the longitudinal grinding and trimming process of diamond rollers on a five-axis machining center. The accuracy of the proposed method in state recognition is 92%, indicating its practical application value.

(a)10%, (b) 20% , (c) 30% , (d)40%.

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0170

Abstract(184)

Abstract:

Study on Mechanical Properties and Rock Breaking Effect of Ridge-Shaped Cutters

, Available online , doi: 10.13394/j.cnki.jgszz.2023.0172

Abstract(243)

Abstract:
Based on the formation characteristics, the targeted selection of shaped cutters can reduce the probability of PDC cutters failure and increase the rate of penetration (ROP) and footage. In order to comprehensively compare the mechanical properties and rock-breaking effect of ridge-shaped PDC cutters, three kinds of ridge-shaped PDC cutters (165-axe, 135-axe, and triple-edged) were firstly studied for wear resistance and impact resistance, and then granite was selected to conduct single-cutter cutting experiments at three depths of cut (DOC), and simulated drilling experiments of full-size bits under different weight of bit, and compared with round cutter. The results show that: ① The wear resistance of ridge-shaped PDC cutter is better than that of round cutter. ② The impact resistance of 165-axe and three-edged cutter is better than that of round cutter, and 135-axe has poorer impact resistance due to the lack of support at the point of impact. ③ At the same DOC, the tangential force and normal force of ridge cutter are lower than that of round cutter, and the smaller the angle of the ridge is, the smaller the cutting force is. ④ The 135 axe shape has the fastest ROP and is suitable for high WOB, the triple-edged cutter have a faster ROP in the low drilling pressure range (less than 20 kN) and a slower ROP in the high drilling pressure range (more than 20 kN) compared to the 165-axe. The rounded cutter have the slowest ROP and are suitable for lower WOB. The experimental results show that when the ridge angle changes, the support material at the impact point also changes, which affects its impact resistance, and at the same time, the change of the ridge angle will change the stress concentration inside the rock in front of it, which will change the effect of rock breaking. The results of this paper can provide a reference for the optimal design of ridge cutter design, bit cutter placement and drilling parameter selection.

Effect of pad and slurry on fixed abrasive polishing of gallium oxide crystal

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0043

Abstract(690)

Abstract:
Gallium oxide crystal is the most representative fourth generation semiconductor material with the advantages of high band gap, high voltage resistance and short absorption cutoff edge, and has broad application prospects. Gallium oxide crystal is prone to micro-cracks, scratches and other surface defects in the polishing process, which is difficult to achieve high-quality surface processing and cannot meet the requirements of the corresponding devices. Moreover, the existing polishing process of gallium oxide crystal is complex and inefficient. Fixed abrasive polishing technology has the advantages of controllable abrasive distribution and depth of cut, and high utilization rate of abrasive grain. Fixed abrasive polishing was used, and the effect of pad and slurry on material removal rate and surface quality were explored in fixed abrasive polishing of gallium oxide crystal. The results show that when the hardness of the polishing pad is moderate II, the abrasive concentration is 100%, and the slurry additive is oxalic acid, material removal rate is 68 nm/min, and the surface roughness Sa value is 3.17 nm in fixed abrasive polishing gallium oxide crystal. Fixed abrasive polishing technology can achieve efficient and high-quality polishing of gallium oxide crystal

Development of CAM system for automatic compound dressing of superabrasive grinding wheels

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0061

Abstract(410)

Abstract:
In the field of superabrasive wheel dressing, multi-process composite dressing has obvious advantages, but there is no research related to the automation system of grinding wheel composite dressing. In order to make the integration of multiple processes in the composite dressing method more systematic and improve the dressing efficiency of shaped grinding wheels, this paper develops a CAM system by self-developed laser-mechanical composite dressing equipment, which can, according to different grinding wheel section shapes, automatically plan the dressing trajectory under multiple processes and dressing strategies, calculate the dressing toolpath with planar three-axis linkage, automatically generate the machining code, and at the same time design a visualisation interface to simulate the machining process. The results of dressing experiments on 150# diamond bronze bonded grinding wheels show that the system can generate machining programs for laser roughing, semi-finishing and mechanical finishing without collision and overcutting of the machine tool, and significantly improve the programming efficiency of the compound dressing method. And the dressing wheel profile error is within 9.1 µm and circular runout error is 6.1 µm.

Study on the Mechanism and Process Magnetorheological Variable Gap Dynamic Pressure Planarization Finishing

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0004

Abstract(542)

Abstract:
In order to improve the polishing efficiency of magnetorheological polishing and realize the high-efficiency, high-quality and ultra smooth planarization of photoelectric wafer, a magnetorheological variable gap dynamic pressure planarization method is proposed. In this paper, the changes of material removal rate and surface roughness of sapphire wafer surface polishing with processing time under different variable gap conditions are studied, and the dynamic pressure flattening mechanism of magnetorheological variable gap is deeply analyzed. The results show that the dynamic change of polishing pressure and the extrusion strengthening effect of MR fluid can be produced by applying axial low-frequency extrusion vibration to MR polishing fluid, and the polishing efficiency and polishing effect can be significantly improved. After 120 min of magnetorheological variable gap dynamic pressure flattening, the surface roughness of sapphire wafer decreased from Ra 7 nm to Ra 0.306 nm, and the material removal rate was 5.519 nm / min. Compared with constant gap magnetorheological polishing, the surface roughness decreased by 49% and the material removal rate increased by 55.1%; By changing the moving speed of variable clearance, the flow field characteristics can be controlled. Choosing the appropriate workpiece pressing speed and workpiece lifting speed is conducive to improve the polishing efficiency and surface quality.

Effect of Fe₃O₄ Characteristics on Properties of Solid-phase Fenton Reaction Lapping Pellets for Single-Crystal SiC

, Available online , doi: 10.13394/j.cnki.jgszz.2022-0008

Abstract(480)

Abstract:
To improve the lapping quality and processing efficiency of single-crystal SiC, solid-state Fenton reaction lapping pellets were prepared. Effects of particle size and concentration of Fe₃O₄solid-phase catalyst on the physical properties (hardness, flexural strength, porosity), catalytic performance, and lapping performance of single-crystal SiC were studied. The results showed that with the increase of Fe₃O₄ particle size, the hardness, flexural strength, porosity, and catalytic performance of the lapping pellets all decreased, the material removal rate (MRR) decreased from 43.12 nm/min to 36.82 nm/min, and the surface roughness (Ra) increased from 1.06 nm to 3.72 nm. As the Fe₃O₄ concentration increased, the hardness and flexural strength of the lapping pellets decreased, and the porosity and catalytic performance increased. Although the material removal rate decreased, the surface roughness (Ra) decreased firstly and then increased. The MRR decreased from 40.14 nm/min to 33.51 nm/min, the surface roughness (Ra) was 3.25 nm, 1.75 nm and 1.88 nm. In this experiment, when the Fe₃O₄ particle size and the concentration was 0.5 µm and 29 wt.%, the processing effect was the best, the MRR and the surface roughness (Ra) was 43.13 nm/min and 1.06 nm.

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