金刚石与磨料磨具工程

2020, 40(2): 1-4.

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Influence of pressure and rotation speed on performance of passive grinding rail

LI Duan, LI Huanfeng, LIU Pengzhan

2020, 40(2): 5-10. doi: 10.13394/j.cnki.jgszz.2020.2.0001

Abstract(156)

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The influence of pressure and speed on some grinding performance of passive rail grinding, namely the force, the temperature, the efficiency and the rail surface roughness, was studied on a test platform simulating passive grinding by replacing normal rail with rail disk. The results show that the increase of grinding speed in the area of 60 to 80 km/h, results in the decrease of grinding force and surface roughness and the increase of grinding temperature and grinding efficiency. It is also found that the increase of grinding pressure, from 120 N to 320 N, leads to higher temperature, larger force, higher efficiency and worse surface quality.

Research on grinding temperature field of rail grinding with compound wheel

YAN Xinlin, XIAO Bo, WU Hengheng, XIAO Bing, ZHANG Yiquan

2020, 40(2): 11-16. doi: 10.13394/j.cnki.jgszz.2020.2.0002

Abstract(237)

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In order to study the temperature field of the composite grinding wheel with brazed diamond insert for rail grinding, a comparative test was carried out on the grinding temperatures of the composite wheel and a resin zirconia corundum wheel for grinding 65Mn steel workpiece under different pressures. Based on the test data, a finite element analysis on the temperature field of the composite wheel for rail grinding was carried out. The results show that with the increase of grinding pressure, the heat production of both wheels increases, while the heat production of composite wheel is relatively smaller. Compared with that of resin grinding wheel at the same condition, the temperature on the surface ground by composite grinding wheel is reduced by nearly 10%.

Mechanism of hydrogen and oxygen etching graphite phase in CVD diamond coatings

JIAN Xiaogang, HUANG Xin, HE Jiacheng, WANG Junpeng

2020, 40(2): 17-21. doi: 10.13394/j.cnki.jgszz.2020.2.0003

Abstract(242)

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In order to study the etching mechanism of hydrogen and oxygen atoms on the graphite phase in CVD diamond coatings, molecular dynamics simulation on the etching process was performed using first-principle molecular simulation calculation method. The adsorption process of either atom on graphite phase and the reaction heat and energy barrier of etching reaction were analyzed. The results show that the adsorption energy of oxygen atoms on the surface of the graphite phase is stronger than that of hydrogen atoms. At the same time, the chemical reactivity of oxygen atoms is stronger than that of hydrogen atoms. It is more easier to form an electron transfer reaction with the surface of the graphite structure. It takes 2 steps to break the C—C bond on the graphite phase surface, while the oxygen atom requires only one step. It means that hydrogen atoms etching the graphite phase have higher reaction energy barrier and require more energy. The oxygen-containing gas source can effectively reduce the deposition temperature of the CVD diamond coating and improve its quality.

Influence of trace elements on color of gem-grade large cultured single crystal diamond

LIU Kun, ZHANG Kun, TIAN Yangyang, ZHANG Jianhua, WANG Tao

2020, 40(2): 22-25. doi: 10.13394/j.cnki.jgszz.2020.2.0004

Abstract(147)

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The influence of different trace elements added on the color of gem-grade large single crystal diamond was studied under a certain pressure and temperature gradient with FeCo40 alloy as catalyst and high-purity graphite as carbon source. The results show that with the increase of Ti doping, the color of large cultured diamond changes from dark yellow to light yellow and then colorless. At the same time, with the doping of trace element B, the color of crystal changes from colorless to light blue, then dark blue.

Effect of pore structure and distribution of porous metal bonded CBN wheel on mechanical properties of abrasive layer matrix

ZHOU Yi, DING Wenfeng, ZHAO Biao

2020, 40(2): 26-31. doi: 10.13394/j.cnki.jgszz.2020.2.0005

Abstract(219)

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In order to solve the problem of strength decline of porous metal bonded CBN wheel under high porosity, spherical urea particles were used to make porous metal bonded wheel abrasive layer matrix with controllable pore diameter, pore shape and pore size. The influence of pore structure factors such as porosity and pore arrangement on the mechanical properties of porous metal bonded abrasive layer matrix was studied under different loading conditions. The results show that the elastic modulus of the matrix with ordered pore arrangement is smaller than that with disordered pore arrangement, and that the yield strength of the matrix decreases with the increase of porosity. Under the same porosity, the matrix with ordered arrangement of pores has higher yield strength under the condition of longitudinal compression and positive arrangement of pores.

Study on properties of heat-resistant resin binder for superhard abrasive tools

YUAN Tianshun, JIAN Yaliu, ZOU Wenjun, PENG Jin, SONG Xudong, LIU Pengzhan

2020, 40(2): 32-35. doi: 10.13394/j.cnki.jgszz.2020.2.0006

Abstract(263)

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A silicone phenolic resin (SPF) was synthesized by transesterification using methyltrimethoxysilane(MTMS) as a modifier. The SPF was determined by FTIR analysis, TGA analysis, mechanical property test and other characterization methods. The results show that MTMS is successfully introduced into the structure of the resin; the resin has excellent heat-resistance, whose temperature at weight loss 10% is 462 ℃, 90 ℃ higher than that of ordinary phenolic resin(PF); the mechanical performance is obviously improved and the grinding ratio of superhard abrasive tools with SPF as resin binder is 51.1% higher than that of superhard abrasive tools with PF as resin binder. Meanwhile, the bending strength and impact strength of superhard abrasive tools with SPF as resin binder are 14.2% and 5.7% higher than that of another one, respectively.

Preparation of edge-hole co-distributed brazed diamond microstructure end-grinding wheel and its grinding performance on alumina ceramics

LIN Zhibing, DU Zhijun, LI Mingcong, WANG Peng, XIE Xiaozhu, ZHANG Fenglin

2020, 40(2): 36-41. doi: 10.13394/j.cnki.jgszz.2020.2.0007

Abstract(475)

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Due to the easy graphitization of diamond during high temperature brazing and the limitation of brazing process, it is still difficult to prepare brazed diamond grinding wheels with finer particle size. In present study, the brazed diamond grinding wheels with different textures, which mainly consisted of edges and holes, were prepared. On coarse diamond grits brazed on the wheels, the textures were micro-machined by pulsed laser. The grinding performance of textured diamond wheels on alumina ceramic was examined. Effect of the textures on grinding forces, surface roughness and wear of diamond girt were compared. It is found that compared with traditional brazed diamond grinding wheels, the micro-edge wheels, which have been curved by lasers, have 37% to 51% lower grinding forces and 18% to 25% smaller roughness. Specially, the wheel with 1∶1 number ratio of edges to holes performs the lowest grinding force and the smallest surface roughness.

Effects of ball milling and dispersant on deagglomeration of vitrified bond powder

LUO Miaodi, DING Yulong, BAO Hua, MIAO Weipeng

2020, 40(2): 42-45. doi: 10.13394/j.cnki.jgszz.2020.2.0008

Abstract(214)

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Effects of ball milling parameters and additive amount of dispersant on the deagglomeration and the mechanical properties of vitrified bond aggregate were studied. Particle-size analyzer, scanning electron microscopy and universal materials testing machine were employed to characterize the particle size, the microstructure and the flexural strength of the vitrified bond powder before and after deagglomeration. The results indicate that the D₅₀ particle size of the vitrified bond powder is refined to 0.186 μm by employing smaller size (5 mm) of the grinding media, 2.5%(mass fraction) dispersant addition and 2 hours milling time. Meanwhile, the dispersion of the particle is good and there is no agglomeration after ball milling. The flexural strength of vitrified bond is 26.2 MPa after sintered at 700 ℃, which is about 45% higher than that of specimens made from raw powder.

Construction of evaluation indices of abrasive blocks based on AHP-PCA

YANG Xue, GAO Wei, TIAN Jianyan, GAO Yunsong, YANG Shengqiang, LI Wenhui

2020, 40(2): 46-52. doi: 10.13394/j.cnki.jgszz.2020.2.0009

Abstract(195)

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The abrasive block is one of the key factors affecting the quality and efficiency of barrel finishing process. The scientific evaluation index is an important premise for the rational evaluation of the abrasive blocks. Therefore, the construction of evaluation indices of the abrasive blocks based on the analytic hierarchy process (AHP) and principal component analysis (PCA) is proposed. Firstly, combining the actual cases of barrel finishing process and the preparation process of the abrasive blocks, the initial evaluation index is obtained by analyzing the selection principles of evaluation index. Secondly, the AHP and PCA are combined to screen the evaluation indexes and then build the final evaluation indices. Finally, according to the initial and final evaluation indices, the abrasive blocks are evaluated and the evaluation results are compared. The results show that the selection of evaluation indexes is reasonable and the evaluation index can be used to evaluate the abrasive blocks reasonably, so as to reduce the workload of collecting evaluation indices data and improve the evaluation efficiency of the abrasive blocks.

Finite element simulation of and experimental study on three-dimensional drilling of large diameter carbon fiber composites

ZHANG Xun, CHEN Yan, XU Jiuhua, YANG Haojun, CHEN Yijia

2020, 40(2): 53-60. doi: 10.13394/j.cnki.jgszz.2020.2.0010

Abstract(235)

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Aiming at some problems in manufacturing the aircraft CR929, namely difficulty to predict exit delamination defect and high cost of hole load prediction test, a three-dimensional finite element drilling simulation and experimental research of carbon fiber reinforced plastics (CFRP) were carried out. Firstly, the macro-mechanical constitutive model of CFRP was established by Fortran language based on user-defined subroutine interface of ABAQUS software. Then a three-dimensional finite element model of large aperture drilling CFRP was established. By comparing the model in experiment, the correctness of the finite element model is verified under the same parameters. Finally, the finite element model was used to predict the axial force, torque and exit delamination of the hole at different processing parameters. The results show that the three-dimensional finite element simulation model of composite drilling based on three-dimensional solid element modeling can reliably predict the axial force and torque. The shape of exit delamination can be predicted by embedding cohesive elements at the exit of CFRP. Under the same parameters, the maximum relative error of simulation prediction for axial force, torque and exit delamination is 15.0%, 19.0% and 12.4%, respectively.

Analysis on machine tool energy consumption based on ultra-fine cemented carbide grinding process

ZHAN Youji, TIAN Xiao, XU Yongchao, JIA Minzhong

2020, 40(2): 61-66. doi: 10.13394/j.cnki.jgszz.2020.2.0011

Abstract(152)

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For the grinding of ultra-fine cemented carbide, the machine tool energy consumption was investigated through the power at various operating states and grinding parameters. The influence of grinding parameters on grinding energy consumption was characterized by grinding specific energy e_s and grinding effective energy efficiency η. The results show that the idle power accounts for 92% of the total grinding power of the grinding machine. The e_s increases slightly with the increase of wheel linear velocity v_s, and decreases with the increase of the grinding depth a_p and the workpiece feeding speed v_w. The v_w has the greatest influence on e_s, followed by a_p and v_s. Moreover, the η increases with the increase of a_p, v_s and v_w, respectively. The a_p has the greatest influence on η, followed by v_s and v_w. In order to reduce the grinding energy consumption during processing, the idle time should be minimized. Meanwhile, under the premise of ensuring machining quality, a larger a_p and v_w should be adopted during grinding the ultra-fine cemented carbide.

Study on surface quality in ultrasonic vibration grinding of SiC ceramics with small diameter grinding wheel

XU Luxin, LI Hua, CAI Xiaotong, ZHOU Peixiang, CHEN Yiwen, WU Jiafu

2020, 40(2): 67-77. doi: 10.13394/j.cnki.jgszz.2020.2.0012

Abstract(253)

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The SiC ceramic parts were machined by ultrasonic vibration grinding and common grinding with small diameter grinding wheel. The effects of grinding wheel linear speed, workpiece feed speed, grinding depth and ultrasonic amplitude on ground surface quality were studied. The results show that compared with the conventional grinding, the grinding tracks of ultrasonic vibration grinding are overlapped with each other, with more uniform surface morphology of workpiece and better surface quality. Because of the scratch crossing of the abrasive grains in ultrasonic vibration, the abrasive grains will produce empty cutting, thus reducing the grinding force and making the grinding process more stable. The surface roughness and the grinding force of ultrasonic vibration grinding decrease with the increase of grinding wheel linear speed and ultrasonic amplitude and the decrease of workpiece feed speed and grinding depth. When the linear speed of grinding wheel and the feed speed of workpiece are low, the effect of ultrasonic vibration grinding is more obvious.

Effect of abrasive size and shape on surface microstructure of titanium alloy cut by abrasive water jet

CHEN Xianjun, ZHOU Wen, XU Maoqin

2020, 40(2): 78-83. doi: 10.13394/j.cnki.jgszz.2020.2.0013

Abstract(169)

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Abrasive grains, with different sizes and shapes, were used to cut titanium alloy on a cutting platform to study the effect of impingement jet on the micro-morphologies of alloy surface. The surface quality of the alloy was characterized by using an ultra-depth-of-field microscope. The results show that the larger the abrasive particle size, the longer the scratches formed, which is that the micro-scratch length caused by 80-mesh abrasive particles is about 5 times longer than that of 160-mesh abrasive particles. It is also found that the scratches formed by spherical abrasive particles have less accumulation, whose surface linear roughness is less than 9.5 μm, and that the linearity roughness of the surface scratched by edged grains is between 9.5 μm and 13.0 μm, with lip-like or scaly metal accumulations. Scratches formed by impact of cylindrical abrasive particles have sharp edges and corners with surface roughness more than 13.0 μm.

Experimental study on grinding damage control of optical materials

YANG Yingpo, JI Yongman

2020, 40(2): 84-88. doi: 10.13394/j.cnki.jgszz.2020.2.0014

Abstract(156)

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Based on the different grinding process parameters of K9 glass, the law of the change of the depth of grinding damage layer with the process parameters is determined, and the crack propagation law is studied through the dynamic detection of the depth of grinding damage layer of the workpiece. The results show that the crack damage in grinding process is a dynamic propagation process. Under the fixed process parameters, the crack propagates steadily so that the depth of the damaged layer remains constant. When the grinding process parameters with less damage are used, the crack growth speed is less than the material removal speed, and hence the depth of damage layer is gradually reduced. The removal speed of damage layer is gradually slowed down until a balance between the growth speed and the removal speed. At the same time, in order to remove the damage layer of one process, the material removal amount of the next process should be 2 to 3 times of the damage layer depth of the previous process.

Finite element simulation of sawing force for impact-resistant diamond saw blades——Take circular saw blades with new semi-circular sink tooth shape as an example

HU Huan, ZHANG Yuncai, LI Chunlin, ZHAO Lei

2020, 40(2): 89-93. doi: 10.13394/j.cnki.jgszz.2020.2.0015

Abstract(261)

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The finite element analysis model of the cutting force of the impact resistant diamond saw blade was established. The numerical simulation and comparative study of the cutting force of the diamond circular saw blade were carried out on the two kinds of tooth structures, with the conventional U-shaped sink and the new semi-circular sinktooth shape. The simulation results show that under the same load, the deformation and stress of the saw blades with new semi-circular sinktooth shape are significantly improved compared with that of the traditional U-shaped sink. The deformation of the saw blade is reduced by 11.56%, the first and third principal stresses are reduced by 24.04% and 34.19% respectively. Therefore, it has good performance of bearing large load and impact resistance.

2020 Vol. 40, No. 2

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