金刚石与磨料磨具工程

2020, 40(3): 1-4.

Abstract(387)

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Experimental and simulation investigation into residual stress for rail grinding with abrasive belt

WANG Wenxi, LI Jianyong, WU Yuan, FAN Wengang

2020, 40(3): 5-12. doi: 10.13394/j.cnki.jgszz.2020.3.0001

Abstract(297)

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To intuitively understand the residual stress state on the rail surface after belt grinding, the influences of grinding parameters on residual stress were investigated on a test bench. Portable residual stress instrument was used to acquire the residual stress along the central line on the ground rail surface. The residual stress along the grinding direction was tensile, the value ranges from 100 MPa to 300 MPa, while the one along the radial direction was compressive, the value ranges from 0 to -250 MPa. To investigate the mechanisms of the influencing factors during the forming process of residual stress, a 3D finite element model (FEM) of single-grain scratching based on thermo-mechanical coupling method was developed. Effects of contact surface friction, cutting depth and cutting speed on residual stress distribution in rail sub-layer were revealed, respectively, The mechanism was also analyzed. Finally, according to the experiment and simulation results, it is suggested that the grinding unit at the end of the grinding train should adopt open grinding. The abrasive belt requires small particle and strong self-sharpening. The grinding process should be suggested using low grinding pressure and low grinding speed with water for cooling and lubrication.

Mechanism model of belt grinding considering single abrasive action

QI Junde, CHEN Bing

2020, 40(3): 13-20. doi: 10.13394/j.cnki.jgszz.2020.3.0002

Abstract(407)

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To solve the problem of quantitative material removal in the grinding process, based on the theories and methods of elastic-plastic deformation, Hertz contact and probability statistics, the material removal mechanism model of belt grinding was constructed from the perspective of micro single abrasive. Firstly, the material removal mechanism of a single abrasive at different deformation stages of workpiece during grinding was analyzed, the grinding process was simplified according to the experimental calculation results, and the calculation method of force on a single abrasive particle was given. On this basis, based on the distribution function of the number of abrasive particles and the blade heights, the equilibrium equation of micro abrasive particles and macro grinding pressure was established by using the theory of probability and statistics, which was used to obtain the cutting depth distribution function of the particles. Combined with the material removal volume of a single abrasive particle, the total material removal model was constructed by integral operation. Finally, the maximum material removal depth was obtained through the TC4 alloy grinding experiment on the robotic grinding platform. The results show that the maximum material removal depth increases with the increase of grinding pressure and belt linear velocity, and decreases with the increase of belt feeding speed. The maximum relative error is 17.66% and the average relative error is 10.55% between the theoretical predicted value and the experimental value, which verifies the validity of the model.

Experimental study on grinding propeller with diamond belt

ZHANG Bingchang, LI Zhong

2020, 40(3): 21-24. doi: 10.13394/j.cnki.jgszz.2020.3.0003

Abstract(316)

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To study the machining of marine propeller, a method of grinding the propeller with electroplated diamond belt was proposed, and the process factors, which had effects on surface roughness of the propeller, were analyzed by experiments. The effects of grinding pressure, belt linear velocity, and grinding feed speed on surface roughness were studied through a single factor experiment, and the optimal combination of the parameters was obtained, namely grinding pressure 15 N, belt linear velocity 30 m/s, and grinding feed speed 20 mm/s. It is also found that both zirconium corundum abrasive belt and diamond abrasive belt have basically the same rules for the surface roughness of the propeller under various process parameters, while the diamond abrasive belt has a better life than the zirconium corundum belt does under the same grinding parameters, with an increase of 125%.

Research on deformation behavior of NC belt grinding of aero-engine blisk and its test

LIU Xiumei, XIAO Guijian, LIU Zhiwu, LEI Haifeng, WU Xiaofeng, ZHOU Feng, HAN Jingyu, YANG Xiaosan, SONG Kangkang

2020, 40(3): 25-32. doi: 10.13394/j.cnki.jgszz.2020.3.0004

Abstract(372)

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There are obvious textures on milled integrated blisk of aero-engine which has complicated structure to machine so that the roughness and the profile accuracy could not meet the design requirements. In addition, the surface quality and the profile accuracy of manual polished blisk would not satisfy the process requirements as well. To solve these problems, the deformation behavior of numerical control (NC) belt grinding on integrated blisk is investigated and related tests are implemented. A new open NC belt grinding method is proposed and the the full profile grinding process of integrated blisk NC belt grinding is analyzed, the deformation mechanism of which is explained. Based on ANSYS-relied simulation analysis of grinding deformation, a grinding pressure control system with pressure feedback is proposed to control the deformation. The grinding tests of NC belt grinding on integrated blisk are carried out on test equipment. Results indicate that the integrated blisk, after NC belt grinding, has surface roughness less than 0.4 μm and profile accuracy better than 0.05 mm. In conclusion, the developed method could fit the blade shape well, which is to enhance the grinding efficiency and meet the design requirements by replacing manual polishing with NC belt grinding.

Effect of matrix surface temperature field on deposition of nano-diamond films based on ANSYS simulation

DENG Fuming, WANG Shuang, GUO Zhenhai, HAO Cen, ZHAO Xin, XIE Yajuan, XU Chenyang

2020, 40(3): 33-39. doi: 10.13394/j.cnki.jgszz.2020.3.0005

Abstract(289)

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In order to obtain high-quality nano-diamond film, ANSYS software is used to simulate the temperature field on the matrix surface. The effects of hot wire number, hot wire distance and distance between the hot wire and the matrix on the temperature field of the matrix surface are simulated and further verified by experiments. The results show that the influences of the hot wire number and the hot wire distance on the temperature field of the matrix surface are not significant, so that just take the appropriate values in the practical application. When the distance between the hot wire and the matrix is less than 5 mm, the temperature field of the matrix surface is uneven and undulating. When the distance between the hot wire and the matrix is greater than 5 mm, the average temperature on the matrix surface decreases with the increase of the distance between the hot wire and the matrix, while the undulating temperature field on the matrix surface disappears and the distribution of the temperature field tends to be uniform. When the distance between the hot wire and the matrix is 7 mm, the temperature field on the matrix surface is the most uniform, and the deposited nano-diamond film has the highest purity, the lowest internal stress and the best quality.

Simulation and optimization of temperature field of diamond coated tools deposited by HFCVD method based on heat dissipation at tool bottom

QIAN Yizheng, ZHANG Tao, WANG Shu, CHEN Dakui, HUANG Guodong

2020, 40(3): 40-45. doi: 10.13394/j.cnki.jgszz.2020.3.0006

Abstract(411)

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In the process of preparing diamond coated tools by a hot filament chemical vapor deposition (HFCVD) method, substrate temperature has an important effect on the uniformity of diamond coating distribution. FLUENT module in ANSYS software is used to analyze a three-dimensional batch tool model of HFCVD by GAMBIT software. In simulation, three heat transfer approaches, namely conduction, convection and radiation, are considered. The simulated investigation analyzes and optimizes the effect of the heat dissipation mode at the bottom of tools on the distribution uniformity of substrate temperature. According to the results, compared with the traditional copper or graphite holder, the ceramic holder with a low thermal conductivity have the lowest the average temperature difference between tools and holder, about 37.82 ℃, which is 45 ℃ lower than the temperature difference between tools and Cu holder. The ceramic holder will be more conducive to the preparation of uniform thickness and quality of CVD diamond coated tools.

Study on defects of diamond/aluminum composites prepared by selective laser melting

SU Zhenhua, LIU Gang, DAI Bing, CAO Kangli, ZHU Jiaqi

2020, 40(3): 46-51. doi: 10.13394/j.cnki.jgszz.2020.3.0007

Abstract(491)

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Diamond reinforced aluminum matrix composites have been successfully fabricated by selective laser melting (selective laser melting, SLM). The fracture and the diamond particles were observed and analyzed in the forming process. The main defects of the composite are the thermal damage of diamond and a large number of holes. The analysis shows that the thermal damage of diamond is mainly caused by the graphitization of diamond which is generated by the direct irradiation of laser. The TiC coating on the surface of diamond could not protect diamond from laser damage. The holes among diamond particles are mainly due to the poor wettability between diamond and matrix during SLM process in an extremely short period, which can not melt easily. So that, a large number of holes are formed.

Effect of volume ratio between Cu-Sn-Ti alloy and vitrified binder on microstructures and mechanical properties of diamond segments

ZHAO Pengcheng, YAN Xinlin, XIAO Bing, MENG Xianglong, LIU Bingheng

2020, 40(3): 52-56. doi: 10.13394/j.cnki.jgszz.2020.3.0008

Abstract(520)

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To improve the holding strength of bond to the diamond grits, a Cu-Sn-Ti alloy was introduced as an additive into the SiO₂-Al₂O₃-B₂O₃-Li₂O vitrified bond, which was then made into segments with diamonds. Some properties of the segments, namely microstructure, shrinkage, phase composition and mechanical properties, were characterized to determine the sintering temperature and the effect of volume ratio of Cu-Sn-Ti alloy in the vitrified bond on the segment performances was studied by SEM and XRD analysis. The results show that TiC phase is formed between the diamond and the cermet bond, which improves the holding strength of the bond to the diamond and then the bending strength of the segments. When the volume ratio of binder to Cu-Sn-Ti alloy is 1∶1, there forms a dense glass network in the segments sintered at 950 ℃, with shrinkage of 3% and maximum bending strength of 64.4 MPa.

Optimization of blade length control based on least squares support vector regression

CUI Qing′an, DUAN Huanjiao, ZHANG Di, QIAO Shuai, DONG Feng

2020, 40(3): 57-61. doi: 10.13394/j.cnki.jgszz.2020.3.0009

Abstract(302)

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The length of the dicing blade affects its performance, while the blade exposure is the key process to control the dicing blade’s length. In the continuous production, the dicing blade’s exposure fluctuates due to the corrosion of multiple blades at one time. To solve this problem, the extreme differences of the sub-set dicing blade’s length were taken as response, with solution temperature, solution concentration and workpiece rotation speed as influence factors. An orthogonal experimental design method was selected to get the test points and then a sample set. Then the least square support vector regression method was used to build a model. Finally, a particle swarm optimization algorithm was used to optimize the model and obtain the optimized process parameters. The experimental results show that this method is effective to reduce the dicing blade’s exposure fluctuation.The difference between the experimental results and the modeling results is only 2.1 μm.

Influence of pre-alloyed powder content on microstructure and properties of iron-based matrix

SUN Weiyun, KANG Jie, DING Ziyang, LI Lianrong, JIAO Can, LIU Shengxin

2020, 40(3): 62-66. doi: 10.13394/j.cnki.jgszz.2020.3.0010

Abstract(271)

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The effects of adding CuZnSn pre-alloyed powder, mass fractions of which were 2%, 6%, 10% and 14%, respectively, on some performances of the iron-based matrix of the diamond ceramic edging wheel were studied, namely the hot-pressed sintering structures, the phase compositions and the mechanical properties. The results show that the iron-based matrix without pre-alloyed powder mainly consists of three kinds of structures: gray-white, light gray and dark gray. The main phases are γ-Fe, (Cu, Sn), (γ-Fe, Ni) solid solution and Fe₄Cu₃、Cu₄₁Sn₁₁ and Ni₄Sn intermetallic compounds. When the matrix with pre-alloyed powder added are sintered at the same conditions, the gray-white structure area decreases with increasing light gray structure area and stable dark gray structure area. In addition to the above phases, Cu_0.61Zn_0.39 and CuZn₂ are also found. With the increase of CuZnSn pre-alloyed powder content, the density, the hardness and the bending strength of iron-based matrix increase first and then decrease, while the wear amount decreases first and then increases. When the mass fraction of CuZnSn pre-alloyed powder is 6%, the maximum values are 99.8%, 104.4 HRB, 947.2 MPa and the minimum value is 0.272 5 g, respectively. Adding appropriate amount of CuZnSn pre-alloyed powder can increase the liquid content of the iron-based matrix, which improves the fluidity of the powder and then the properties of the matrix. However, excessive CuZnSn pre-alloy powder would reduce the comprehensive properties of the matrix.

Design and application of novel hybrid drill bit for hard formation with strong abrasivity

YU Jinping, ZOU Deyong, LIU Xiaoao

2020, 40(3): 67-71. doi: 10.13394/j.cnki.jgszz.2020.3.0011

Abstract(313)

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To improve the rock breaking efficiency and the service life of polycrystalline diamond compact (PDC) bit in the hard formation with strong abrasivity, two novel PDC-impregnated diamond insert hybrid bits, which are composed of PDC cutters and impregnated diamond insert as cutting units, are designed and tested in the quartzite formation of a fault block in central Hebei Province. Field tests show that the rate of penetration (ROP) of 1^# novel bit is increased by 52.30% and that the bit footage is increased by 97.30% compared with the average value of roller bits used in the same well section.It is also found that the ROP of 2^# novel drill bit is increased by 30.85% and 32.30% and the bit footage is increased by 70.50% and 47.40% compared with the average value of roller bit and M1375D PDC bit. In conclusion, PDC-impregnated diamond insert hybrid drill bit greatly improves the drilling efficiency of hard formation with strong abrasivity and reduces the drilling cost.

Research on dressing quantification and grinding performance of brazed grinding head

SUN Liang, CHEN Yan, LIANG Yuhong, HE Yi, GUO Nan

2020, 40(3): 72-79. doi: 10.13394/j.cnki.jgszz.2020.3.0012

Abstract(291)

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Based on the concept of effective abrasive grain number and the calculation method of surface roughness, two indexes, namely effective dressing rate N_r and dressing dispersion degree H, were proposed to evaluate the grinding performance and surface topography of the grinding head. The variation of N_r and H during the dressing process were analyzed. The relationship between both indexes and the surface roughness and the grinding force of carbon fiber reinforced plastics(CFRP) after grinding was also established. The experimental results show that N_r can effectively characterize the dressing state of the abrasive particles on the grinding head and reflect the passivation degree of the grinding head. H can effectively characterize the contour of the abrasive grain, and predict the quality of CFRP surface. When H is 18~25 μm, the grinding head surface roughness is the best. The grinding head force has smaller growth amplitude, and the grinding head has better performance.

Influence of micro-texture of strip groove on cutting performance of PCBN tool

ZHU Nan

2020, 40(3): 80-85. doi: 10.13394/j.cnki.jgszz.2020.3.0013

Abstract(390)

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As a new method of tool structure design, micro-texture has a certain impact on the performance of cutting tool. The strip-groove micro-texture is designed and prepared on the rake face of cutting tool. Combining with the finite element simulation technology, the influence of the strip-groove micro-texture on the cutting force and the machined surface quality is theoretically analyzed. Then, the cutting experiment is designed to verify the finite element simulation results. The results show that finite element simulation and cutting test have similar conclusion. Compared with the non-textured tool, the strip-groove micro-texture can reduce the cutting force, which has the most awesome influence on the main cutting force, and weak influence on feed force. The strip-groove micro-texture makes the surface stress, plastic strain and roughness of the workpiece smaller than those of the non-texture tool. The machined surface quality of workpiece is improved.

Effect of abrasive size and matrix hardness on fixed abrasive polishing of YAG crystal

MING Shun, LI Jun, ZHANG Yuchi, QIU Yang, ZHU Yongwei, ZUO Dunwen

2020, 40(3): 86-90. doi: 10.13394/j.cnki.jgszz.2020.3.0014

Abstract(475)

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Yttrium aluminum garnet (YAG) is a kind of hard-brittle and difficult-to-machine material with wide application. Its polishing process is complicated and inefficient. Fixed abrasive polishing technology has the advantages of excellent planarization ability, high selectivity for workpiece surface morphology, and high abrasive utilization. The effect of matrix hardness and diamond particle size of fixed abrasive pad on material removal rate and surface quality was investigated in fixed abrasive polishing of YAG crystal. The results show that when the hardness of the matrix is moderate to Ⅱ and the diamond abrasive size is 3 to 5 μm, the effect of fixed abrasive polishing of YAG crystal is the best. Under these conditions, material removal rate is 255 nm/min and surface roughness S_a is 1.79 nm in fixed abrasive polishing of YAG crystal.

Study on mechanism of waviness in cross grinding large diameter aspherical mirror

XI Jianpu, LIU Tongshi, LI Yadong, LI Bin, ZHAO Zexiang

2020, 40(3): 91-97. doi: 10.13394/j.cnki.jgszz.2020.3.0015

Abstract(260)

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The influence of the eccentric vibration amplitude of spindle and the grinding parameters on the surface waviness is investigated according to the cross-grinding method for large-diameter aspheric mirrors, and a three dimensional (3D) model of the mechanism of grinding surface waviness is established. The relationship between grinding surface 3D waviness and machining process parameters is analyzed by simulation experiments, and the optimal range of grinding process parameters is proposed for the specific spindle. The grinding experiment results show that the relationship between the established 3D waviness model and grinding process parameters is reasonable. The wheel speed of 1600 to 1 800 r/min , the X axis feed velocity of 1 to 3 mm/r and the workpiece speed of 20 r/min are optimal technological parameters.

2020 Vol. 40, No. 3

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