金刚石与磨料磨具工程

Analytic hierarchy process and fuzzy evaluation of automatic separation scheme for diamond synthetic blocks

YUAN Feng, ZHANG Yanhui, LI Shuaiyuan

2019, 39(6): 1-6. doi: 10.13394/j.cnki.jgszz.2019.6.0001

Abstract(325)

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Abstract:
In order to design and develop an automatic separation equipment for diamond synthesis blocks, an evaluation criterion system for automated separation schemes was established and three schemes for automatic separation of diamond synthesis blocks were proposed and analyzed by analytic hierarchy process (AHP). The weight of each criterion was determined and so was the score of each scheme under a single criterion. Then the separation scheme was selected according to the hierarchical ranking conclusion. The selected scheme was evaluated by using fuzzy evaluation, which was to assess the scheme based on the evaluation criterion system using a single factor fuzzy comprehensive judgment method, to get a overall ranking. The results show that the accuracy of the system could be proven by experiments and that the scheme determined by AHP satisfied the requirements of the synthesis company.

Diamond raw detection system based on machine vision

SHI Guangfeng, WANG Xue, WANG Shukun, GUO Fengjie, YU Dawei

2019, 39(6): 7-12. doi: 10.13394/j.cnki.jgszz.2019.6.0002

Abstract(329)

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In order to reduce the detection cost and avoid human error, a diamond rough detection system based on machine vision is developed. The information of size, shape and color of diamond is detected by image processing, and a three-dimensional model of diamond raw stone which can be displayed from a free perspective is generated. The results show that the system is easy to operate in shape and color detection, the scale accuracy of size detection is 0.5 μm and the measurement accuracy of graphic is in the micron level, which can reduce the detection cost and human error.

Judgment of powder mixing uniformity basedon principal component analysis and similarity with variable weight

LIU Peng, TIAN Jianyan, GAO Wei, GAO Yunsong, WANG Guohua, YANG Shengqiang

2019, 39(6): 13-19. doi: 10.13394/j.cnki.jgszz.2019.6.0003

Abstract(265)

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Abstract:
To judge the mixing uniformity of powder materials during the preparation of sintered abrasive blocks, a detection method of powder uniformity based on the similarity of multiple powder imagesis proposed. Firstly, a deviceis designed to collect powder samples online, the image of which is collected by digital microscope. Then, the statistical features of gray distribution based on gray histogram are extracted as the feature parameters of the collected images. Principal component analysis (PCA) is used to reduce the dimension of image features and to construct image feature matrix. Finally the variable weight similarity of each powder image tothe sample density center in each set of images is calculated. The smallest one taken as the similarity with an appropriate thresholdis set to judge the powder whether to mix evenly. The experimental results show that the proposed method can accurately judge the mixing endpoint and determine the optimal mixing time. It is suitable for judging the mixing uniformity of powder materials in the sintered abrasive blocks. It is helpful to improve production efficiency and grinding block quality andincrease economic benefit.

Semantic segmentation of diamond image using dilated convolutional neural network

PAN Bingsuo, PAN Wenchao, LIU Ziyu

2019, 39(6): 20-24. doi: 10.13394/j.cnki.jgszz.2019.6.0004

Abstract(342)

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Abstract:
For precise segmentation of diamond images, a semantic segmentation model was constructed based on dilated convolutional neural network. A small-scale data set of diamond images was established. The hyper parameters of the model, including batch size, number of filters and dilation coefficient, were optimized. The segmentation results obtained with dilated convolutional network were compared with those acquired by thresholding method and adaptive thresholding method. The results show that batch size, number of filters and dilation coefficient have important effects on the segmentation ability of the constructed model. It is also found that dilated convolutional network can achieve a recall value of 0.966 at the level of 0.965 precision, which is much higher than those of traditional methods. Especially, it is able to classify effectively the bright spots in diamond images.

Diamond coated drawing die prepared by direct current arc plasma jet method

CUI Yuming, LI Guohua, JIANG Long

2019, 39(6): 25-29. doi: 10.13394/j.cnki.jgszz.2019.6.0005

Abstract(542)

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Abstract:
Wire drawing process is developing towards precision, high speed, low consumption and high production efficiency. Diamond coated drawing die is one of the most popular products. On the basis of summarizing the drawing die method of diamond coating prepared by direct current arc plasma jet technology, the coating quality is tested by Rockwell hardness tester, surface roughness profilometer, Raman spectrometer and optical microscope. The results show that the purity and the thickness uniformity of diamond coatings are both good. There are no serious cracks or film shedding at the edge of indented area under 1 470 N load. The average surface roughness R_a is 18 nm.

Study on wear resistance of Ti₃SiC₂ composite materials

YUAN Dongfang, ZOU Qin, LI Yanguo, WANG Mingzhi

2019, 39(6): 30-38. doi: 10.13394/j.cnki.jgszz.2019.6.0006

Abstract(301)

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Ti₃SiC₂ is a special ceramic material with hexagonal crystal structure. It has excellent properties of both metal and ceramic, such as high temperature strength, oxidation resistance and processability. It is widely used in wear-resistant lubricating materials. In this paper, the excellent properties and wide applications of Ti₃SiC₂ composites with metal, SiC, diamond, TiC or Al₂O₃ are reviewed, as well as their research directions.

Experimental study on sintering of diamond particles with multiple cutting edges

CHEN Qiang, YANG Xuefeng, HUA Bobo, ZHANG Zheng, WANG Heng

2019, 39(6): 39-42. doi: 10.13394/j.cnki.jgszz.2019.6.0007

Abstract(379)

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Abstract:
In order to improve the sharpness and machining efficiency of diamond tools and prolong the service life, the surface of diamond particles was processed by low-temperature sintering. The multi-edged diamond particles with different sintering processes were observed and quantitatively analyzed by SEM and mass loss rate. The results show that the best sintering process for the multi-blade treatment of diamond particle is as follows: sintering temperature of 750 ℃, 480 min, oxygenation pumped twice during the sintering process, each time 10 kPa, ventilation 2 min with interval of 2 h. Under this condition, multi-edged diamond particles are processed, and the surface of multi-edged diamond particles with moderate size and uniform pit distribution can be obtained. The grinding experiment on silicon carbide wafer shows that the material removal rate of multi-blade diamond particle is about 1.1 times higher than that of conventional diamond particles. The roughness R_a of the wafer after grinding is about 24% of that of conventional diamond particle, which significantly improves the grinding and polishing efficiency and precision of silicon carbide wafer.

Influence of brazing time on performance of row saw

YU Qi, LI Zhen, YU Xinquan, BAO Li, MA Jia, PAN Jianjun, LONG Weimin

2019, 39(6): 43-47. doi: 10.13394/j.cnki.jgszz.2019.6.0008

Abstract(301)

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Abstract:
CT643 brazfing filler was used to conduct welding experiments on row saw through high frequency brazing. The effect of brazing time on the performance of row saw was studied. The shear strength and morphology of the brazed joint were tested by universal capability testing machine and electron microscope. The brazing area of the solder beside the steel matrix was measured by body microscope. The microstructure and hardness of the heat affected zone were compared and analyzed by metallographic microscope and Rockwell hardness tester. The results show that with the increase of brazing time, the shear strength of joints decreases gradually, and the grain size at the heat affected zone grows to form tempered troostite. In addition, the brazing area of steel matrix decreases, and the area of heat affected zone increases with decreased hardness. When the brazing time was 1.8 s, the CT643 solder infiltrates into the steel matrix for about 90 μm, while the steel matrix diffuses to the solder interface to form bamboo shoot-like protrusions with a height of about 10 μm.

Effect of ZrSiO₄on properties and structures of low temperature vitrified bond

TIAN Jiugen, HOU Yonggai

2019, 39(6): 48-52. doi: 10.13394/j.cnki.jgszz.2019.6.0009

Abstract(315)

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Different contents of ZrSiO₄ additives were added to Al₂O₃-B₂O₃-SiO₂ low temperature vitrified bond. The effect of ZrSiO₄ content on the structures and properties of low temperature ceramic bond was studied by differential scanning calorimeter, X-ray diffractometer and scanning electron microscope (SEM).The results show that with the increase of ZrSiO₄ content, the refractoriness of the ceramic bond does not increase significantly, and its coefficient of thermal expansion decreases within a certain range. When the mass fraction of ZrSiO₄ is 4%, the structure of the vitrified bond is compact with uniform distribution and the comprehensive performance of the vitrified bond is the best, which is flexural strength of 57.37 MPa and microhardness of 855.59 MPa.

A review on polishing technology of large area free-standing CVD diamond films

ZHANG Pingwei, TONG Tingting, LI Yifeng

2019, 39(6): 53-61. doi: Code10.13394/j.cnki.jgszz.2019.6.0010

Abstract(333)

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Study on fabrication and tribological properties of TiB₂-based cutting tools

FAN Xiaowen, WANG Guozhen, LU Fengxiang

2019, 39(6): 62-68. doi: 10.13394/j.cnki.jgszz.2019.6.0011

Abstract(278)

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Three groups of TiB₂-based cutting tools with different compositions were prepared by hot pressing sintering. The microstructure, mechanical properties and tribological properties of B73H18N0, B49H18N24 and B41H18C32 samples were compared and analyzed. The results show that no new phase is formed in B49H18N24 and B41H18C32 samples which have TiN and TiC added. The hardness, bending strength and fracture toughness of three TiB₂-based cutting tools samples are respectively B73H18N0 > B41H18C32 > B49H18N24, B73H18N0 > B41H18C32 > B49H18N24 and B41H18C32 > B49H18N24 > B73H18N0. Under the same sliding speed or load, the wear rate of three TiB₂-based cutting tools against TA2 titanium alloy increases with the increase of load or sliding speed, and the wear rate of B41H18C32 sample is the lowest, indicating that B41H18C32 sample has relatively better wear resistance when grinding TA2 titanium alloy. The wear mechanisms of three TiB₂-based cutting tool specimens during dry friction and wear are abrasive wear, adhesive wear and oxidation wear, and mainly adhesive wear.

Study on grinding behavior of laser-structured grinding in silicon nitride ceramic

LI Si, XIONG Xuefeng, WEN Dongdong

2019, 39(6): 69-74. doi: 10.13394/j.cnki.jgszz.2019.6.0012

Abstract(310)

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Four patterns with the same surface area were etched by laser irradiation on the surface of Si₃N₄ ceramics to improve the machining precision. The surfaces with etched patterns were then ground by using diamond grinding wheels, and the effect of pattern form on grinding effect was studied, as well as the effects of wheel speed and infeed speed on grinding force. The results indicate that laser irradiation could produce grooves on Si₃N₄ surface, where the grinding fluid are easy to enter, and that it also reduces the strength of surface Si₃N₄ and then the grinding force decreases up to 63%. Meanwhile, the wheel wear is alleviated. The influence laws of wheel speed and infeed speed on grinding force are the same with those when grinding normal Si₃N₄.

Study on surface quality of zirconia ceramics used for bearing ground by diamond grinding wheel

LI Songhua, HAN Guangtian, SUN Jian, CHEN Wenzheng, WANG Kechong

2019, 39(6): 75-81. doi: 10.13394/j.cnki.jgszz.2019.6.0013

Abstract(433)

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To obtain a high quality surface in the grinding of zirconia ceramics, single factor experiments were used to study the effects of grinding depth, grinding wheel linear speed and workpiece feed speed on the surface quality of zirconia ceramics in precision grinding and its material removal mechanism. The surface morphology of the ground samples was observed by ultra field depth three-dimensional microscope and scanning electron microscope. Orthogonal experimental carried out to optimize the grinding parameters and verify them. Results show that the grinding surface roughness increases with the increase of grinding depth and workpiece feed speed. The grinding surface roughness first decreases and then increases with the increase of grinding wheel linear speed. The optimal combination is grinding depth of 5 μm, grinding wheel linear speed of 40 m/s and workpiece feed speed of 1 000 mm/min. Under the optimum grinding conditions, the average roughness of surface R_a is 0.388 9 μm, 0.417 0 μm and 0.403 7 μm in the three groups of zirconia ceramics grinding experiments.

Study on grinding process of corundum abrasive microscopic samples

XING Bo, ZHAO Jinzhui, CHEN Xuewei, LI Bingwen, FENG Keming, WANG Xiaoguang

2019, 39(6): 82-87. doi: 10.13394/j.cnki.jgszz.2019.6.0014

Abstract(272)

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The sample preparation methods of four corundum abrasives, namely zircon corundum (ZA), microcrystalline corundum (SG), brown corundum (A) and black corundum (BA), were studied. The samples were prepared by direct grinding with ultra-fine resin diamond wheel and manual polishing. The surface roughness, microhardness and surface morphology were compared and analyzed. The quality and efficiency of two kinds of sample preparation methods were studied, and the process parameters of direct grinding of four kinds of corundum abrasive samples were optimized. The results show that the surface roughness R_a,R_z and microhardness of corundum abrasives by direct grinding are basically the same as those by manual grinding, while the efficiency of the former is at least double times higher than that of the latter; ZA, SG and A can meet the microhardness test requirements by directly selecting the coarse grinding and fine grinding processes, while BA abrasives require two additional spark-our grinding processes to meet the microhardness test requirements on the basis of coarse grinding and fine grinding processes.

Optimization of cutting parameters in crankshaft inner milling based on finite element simulation

GUO Zhihao, XIE Lijing, XIE Zhiyong, LIANG Guoxiang

2019, 39(6): 88-91. doi: 10.13394/j.cnki.jgszz.2019.6.0015

Abstract(331)

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Crankshaft inner milling technology is widely used in crankshaft rough machining because of its advantages in machining quality and efficiency. However, the selection of internal milling parameters is lack of corresponding standards and methods. In this paper, through the finite element simulation, a finite element model of crankshaft inner milling is established. The simulation of crankshaft deformation is implemented by using the milling force obtained from the inner milling simulation so as to predict the cylindricity error of crankshaft journal. It is revealed that the cylindricity error of crankshaft journal decreases with the increase of cutter speed, and the rate decreases gradually.

Study on SPL of multi-blade block cutter based on statistical energy method

ZHAO Jiaqi, HUANG Bo, ZHANG Jinsheng, JU Junwei, HAN Yaqun

2019, 39(6): 92-98. doi: 10.13394/j.cnki.jgszz.2019.6.0016

Abstract(277)

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Combined diamond circular saw blade was easy to produce vibration and radiate noise when processing hard and brittle materials. Based on the statistical energy analysis (SEA), a granite sawing model was established. Considering the conditions of modal density, internal loss factor, constraint, excitation and radiation area in the practical engineering of the system, the noise radiation level of the combined diamond circular saw blade was estimated quantitatively in the frequency domain, and compared with the field measurement results.The results show that the sound pressure level of the nine-piece combined diamond circular saw blade with outer diameter of 460 to 1584 mm and thickness of 4.0 mm is 88.3 to 102.3 dB in the high frequency range, and the peak range is 4000 Hz in the high frequency range. And the sound pressure level of the high-frequency range of 1 to 5 combined diamond circular saw blades is 79.5 to 99.2 dB, and the sound pressure level increases with the number of combined sheets, but the overall increasing amplitude decreases with the increase of the number of slices. However, the high-frequency sound pressure level range of the combined diamond circular saw blade with thickness of 3.5 to 5.5mm is 86.1 to 104.7 dB, and the sound pressure level increases with the thickness of the composite sheet, and the sound pressure level at the peak of 4000 Hz has a difference of 5.7 dB. The experimental results are in good agreement with those of the model, which proves that the statistical energy analysis model can be used to calculate the sound pressure level of high frequency noise of saw blades.

Development of boron and its synergistic doped diamond blocks

WANG Zhiwei, ZOU Qin, LI Yanguo, YIN Yuhang, CHEN Hongguang, WANG Mingzhi

2019, 39(6): 99-106. doi: 10.13394/j.cnki.jgszz.2019.6.0017

Abstract(608)

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The semiconductor properties of diamond can be obtained by adding impurity elements like boron. Diamond semiconductor materials with excellent properties can be prepared by high temperature and pressure method. This paper introduces the research development of boron and its co-doped diamond block materials. It summarizes the influence of doping on the morphology, structure and properties of diamond. The factors that affect the quality of doped diamond under high temperature and pressure are clarified. In the end, this paper looks forward to the application prospect of boron and its co-doped diamond block materials.

2019 Vol. 39, No. 6

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