Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life.This diamond super tool,a...Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life.This diamond super tool,as well as the manufacturing equipment,has been unavailable to Chinese enterprises for a long time due to patents.In this paper,a diamond blade segment with a 3D lattice of diamond grits was additively manufactured using a new type of cold pressing equipment(AME100).The equipment,designed with a rotary working platform and 16 molding stations,can be used to additively manufacture segments with diamond grits arranged in an orderly fashion,layer by layer;under this additive manufacturing process,at least 216000 pcs of diamond green segments with five orderly arranged grit layers can be produced per month.The microstructure of the segment was observed via SEM and the diamond blade fabricated using these segments was compared to other commercial cutting tools.The experimental results showed that the 3D lattice of diamond grits was formed in the green segment.The filling rate of diamond grits in the lattice could be guaranteed to be above 95%;this is much higher than the 90%filling rate of the automatic array system(ARIX).When used to cut stone,the cutting amount of the blade with segments made by AME100 is two times that of ordinary tools,with the same diamond concentration.When used to dry cut reinforced concrete,its cutting speed is 10%faster than that of ARIX.Under wet cutting conditions,its service life is twice that of ARIX.By applying the machine vision online inspection system and a special needle jig with a negative pressure system,this study developed a piece of additive manufacturing equipment for efficiently fabricating blade segments with a 3D lattice of diamond grits.展开更多
The usability of waste steel grits and limestone sand in the construction of concrete pavement was investigated.Four different types of pavement concretes were produced,including coarse limestone concrete not containi...The usability of waste steel grits and limestone sand in the construction of concrete pavement was investigated.Four different types of pavement concretes were produced,including coarse limestone concrete not containing waste steel grit,coarse limestone concrete containing waste steel grit,limestone sand concrete not containing waste steel grit,and limestone sand concrete containing waste steel grit.In this study,water/binder ratio in concrete production was taken as 0.44.In the production of limestone sand concrete containing waste steel grit,limestone sand with a grain diameter of 0.1-1.0 mm was used as aggregate.Waste steel grits with a grain diameter of 0.2-0.7 mm were added to the concrete mixture.Standard water curing and combined curing were applied to concrete samples.After standard water curing and combined curing,compression and bending tests of the same types of cube and beam concrete samples were carried out.As a result of the study,the maximum compressive and bending strengths were found to be 50.21 MPa and 5.07 MPa for limestone sand concrete containing waste steel grit.The study results show that waste steel grits increase the compressive and bending strength of concrete pavement.展开更多
The existing research about ductile grinding of fused silica glass was mainly focused on how to carry out ductile regime material removal for generating very "smoothed" surface and investigate the machining-...The existing research about ductile grinding of fused silica glass was mainly focused on how to carry out ductile regime material removal for generating very "smoothed" surface and investigate the machining-induced damage in the grinding in order to reduce or eliminate the subsurface damage.The brittle/ductile transition behavior of optical glass materials and the wear of diamond wheel are the most important factors for ductile grinding of optical glass.In this paper,the critical brittle/ductile depth,the influence factors on brittle/ductile transition behavior,the wear of diamond grits in diamond grinding of ultra pure fused silica(UPFS) are investigated by means of micro/nano indentation technique,as well as single grit diamond grinding on an ultra-stiff machine tool,Tetraform "C".The single grit grinding processes are in-process monitored using acoustic emission(AE) and force dynamometer simultaneously.The wear of diamond grits,morphology and subsurface integrity of the machined groves are examined with atomic force microscope(AFM) and scanning electron microscope(SEM).The critical brittle/ductile depth of more than 0.5 μm is achieved.When compared to the using roof-like grits,by using pyramidal diamonds leads to higher critical depths of scratch with identical grinding parameters.However,the influence of grit shapes on the critical depth is not significant as supposed.The grinding force increased linearly with depth of cut in the ductile removal regime,but in brittle removal regime,there are large fluctuations instead of forces increase.The SEM photographs of the cross-section profile show that the median cracks dominate the crack patterns beneath the single grooves.Furthermore,The SEM photographs show multi worn patterns of diamond grits,indicating an inhomogeneous wear mechanism of diamond grits in grinding of fused silica with diamond grinding wheels.The proposed research provides the basal technical theory for improving the ultra-precision grinding of UPFS.展开更多
This study investigated effects of dietary fibre and grit on growth performance, gastrointestinal tract(GIT) development, serum indexes and grit retention of Sichuan white goslings in China. The experiment was a 3...This study investigated effects of dietary fibre and grit on growth performance, gastrointestinal tract(GIT) development, serum indexes and grit retention of Sichuan white goslings in China. The experiment was a 3×2 factorial design consisting of dietary crude fibre(CF) at 2.0, 4.0 and 6.0% levels by adding grass meal and with or without grit supplementation. A total of 720 1-d-old male goslings were randomly allocated into 36 pens of 20 goslings/pen(n=6 pens/treatment). At 21 d of age, GIT, blood samples and grit in gizzards were collected. Body weight(BW), empty BW(without GIT), average daily gain(ADG) and average daily feed intake(ADFI) were affected by CF levels and the medium(4.0%) had the highest value. Adding grit improved BW, empty BW, ADG and ADFI. CF affected relative weight or length of proventriculus, gizzard and duodenum. Increasing CF levels decreased jejunum villus height and affected caecal crypt depth and villus height to crypt depth ratio. Higher CF levels decreased serum triglyceride. A d ding grit increased relative weight of abdominal fat. Grit addition increased grit weight in gizzard and the ratio of grit in 0.45-1 and 1-2 mm while decreasing the ratio of grit < 0.45 and 2-3 mm. In conclusion, m oderate CF level and grit addition increased performance of goslings without interaction. Dietary CF levels affected the development of upper GIT and serum triglyceride. Grit needed by goslings should be less than 2 mm. Goslings' gizzard would accumulate grit from feed when other grit could not be acquired.展开更多
CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optica...CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optical microscope,scanning electron microscope and X-ray diffraction equipment were utilized to study the effects of heating temperature on the microstructure of the joining interface.The compressive strength of the brazed composite grits was also measured.The experimental results show that the atoms of Ti,Al,B and N have preferentially penetrated towards the joining interface of composite grits and filler alloy.The compounds of Ti-nitride,Ti-borides and Ti3AlN were formed in the reaction layer.Degradation effect was not made on the compressive strength of the CBN-AlN composite grits when the brazing process was carried out in the temperature range of 890-920 ℃.展开更多
Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals,W,Mo,Ti,and Cr,were considered. The numerical results show that compressive s...Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals,W,Mo,Ti,and Cr,were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp corner; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.展开更多
The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. ...The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. The interacting scratch process for optical glass BK7 with the grit interval distance as the variable was simulated by the ABAQUS software of finite element simulation based on the energy fracture theory. Double grits interacting scratch test for optical glass BK7 was carried out on the DMG ULTRASONIC 70-5 linear, by which the reliability of finite element simulation was verified. The surface morphology of the workpiece was analyzed by scanning electron microscopy(SEM), which showed that the width of groove increased obviously with the increase of scratch depth and the grit interval distance. Results of the width of groove were consistent with the simulation results. The subsurface damage layer was analyzed by the method of HF acid etching, which showed that there was an area of cracks intersecting. The scratching force was measured by the threedimensional dynamometer of KISTLER, which showed that the second scratching force increased with the increase of scratching depth and the grit interval distance. The force in the second scratch was smaller than that in the first time, which was consistent with the Griffith fracture theory.展开更多
Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using ?nite element analysis, with a consideration of the nonuniform temperature dis...Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using ?nite element analysis, with a consideration of the nonuniform temperature distribution in the induction brazing model. The in?uences of induction brazing parameters on the residual stresses of polycrystalline CBN abrasive grits have been analyzed, including the embedding depth, grit side length, etc. Results obtained show that the tensile stress with a 40% embedding depth is 292 MPa, which is the minimum on the bonding interface compared with other embedding depths. Meanwhile, the maximum tensile stress is 575 MPa, with an increase of 59% compared with that of a grit side length of 50 mm. Finally, the simulation results of the brazing residual stress of polycrystalline CBN abrasive grits have been con?rmed valid based on the residual stress measurement of the brazed monocrystalline CBN grit.展开更多
基金Supported by Scientific Research Funds of Guangdong Province of China(Grant No.2017B090922008)the Scientific Project of Chaozhou of China(Grant No.2018ZD10).
文摘Diamond tools with orderly arrangements of diamond grits have drawn considerable attention in the machining field owing to their outstanding advantages of high sharpness and long service life.This diamond super tool,as well as the manufacturing equipment,has been unavailable to Chinese enterprises for a long time due to patents.In this paper,a diamond blade segment with a 3D lattice of diamond grits was additively manufactured using a new type of cold pressing equipment(AME100).The equipment,designed with a rotary working platform and 16 molding stations,can be used to additively manufacture segments with diamond grits arranged in an orderly fashion,layer by layer;under this additive manufacturing process,at least 216000 pcs of diamond green segments with five orderly arranged grit layers can be produced per month.The microstructure of the segment was observed via SEM and the diamond blade fabricated using these segments was compared to other commercial cutting tools.The experimental results showed that the 3D lattice of diamond grits was formed in the green segment.The filling rate of diamond grits in the lattice could be guaranteed to be above 95%;this is much higher than the 90%filling rate of the automatic array system(ARIX).When used to cut stone,the cutting amount of the blade with segments made by AME100 is two times that of ordinary tools,with the same diamond concentration.When used to dry cut reinforced concrete,its cutting speed is 10%faster than that of ARIX.Under wet cutting conditions,its service life is twice that of ARIX.By applying the machine vision online inspection system and a special needle jig with a negative pressure system,this study developed a piece of additive manufacturing equipment for efficiently fabricating blade segments with a 3D lattice of diamond grits.
文摘The usability of waste steel grits and limestone sand in the construction of concrete pavement was investigated.Four different types of pavement concretes were produced,including coarse limestone concrete not containing waste steel grit,coarse limestone concrete containing waste steel grit,limestone sand concrete not containing waste steel grit,and limestone sand concrete containing waste steel grit.In this study,water/binder ratio in concrete production was taken as 0.44.In the production of limestone sand concrete containing waste steel grit,limestone sand with a grain diameter of 0.1-1.0 mm was used as aggregate.Waste steel grits with a grain diameter of 0.2-0.7 mm were added to the concrete mixture.Standard water curing and combined curing were applied to concrete samples.After standard water curing and combined curing,compression and bending tests of the same types of cube and beam concrete samples were carried out.As a result of the study,the maximum compressive and bending strengths were found to be 50.21 MPa and 5.07 MPa for limestone sand concrete containing waste steel grit.The study results show that waste steel grits increase the compressive and bending strength of concrete pavement.
基金supported by National Key Science and Technology Projects of China (Grant No. 2009ZX04001-101, Grant No. 2009ZX01001-151)New Century Excellent Talents in University,China (GrantNo. NCET-07-0246)National Natural Science Foundation of China(Grant No. 50675051)
文摘The existing research about ductile grinding of fused silica glass was mainly focused on how to carry out ductile regime material removal for generating very "smoothed" surface and investigate the machining-induced damage in the grinding in order to reduce or eliminate the subsurface damage.The brittle/ductile transition behavior of optical glass materials and the wear of diamond wheel are the most important factors for ductile grinding of optical glass.In this paper,the critical brittle/ductile depth,the influence factors on brittle/ductile transition behavior,the wear of diamond grits in diamond grinding of ultra pure fused silica(UPFS) are investigated by means of micro/nano indentation technique,as well as single grit diamond grinding on an ultra-stiff machine tool,Tetraform "C".The single grit grinding processes are in-process monitored using acoustic emission(AE) and force dynamometer simultaneously.The wear of diamond grits,morphology and subsurface integrity of the machined groves are examined with atomic force microscope(AFM) and scanning electron microscope(SEM).The critical brittle/ductile depth of more than 0.5 μm is achieved.When compared to the using roof-like grits,by using pyramidal diamonds leads to higher critical depths of scratch with identical grinding parameters.However,the influence of grit shapes on the critical depth is not significant as supposed.The grinding force increased linearly with depth of cut in the ductile removal regime,but in brittle removal regime,there are large fluctuations instead of forces increase.The SEM photographs of the cross-section profile show that the median cracks dominate the crack patterns beneath the single grooves.Furthermore,The SEM photographs show multi worn patterns of diamond grits,indicating an inhomogeneous wear mechanism of diamond grits in grinding of fused silica with diamond grinding wheels.The proposed research provides the basal technical theory for improving the ultra-precision grinding of UPFS.
基金financially supported by the China Agriculture Research System (CARS-43-14)the Special Fund for Agro-scientific Research in the Public Interest, China (201303143)
文摘This study investigated effects of dietary fibre and grit on growth performance, gastrointestinal tract(GIT) development, serum indexes and grit retention of Sichuan white goslings in China. The experiment was a 3×2 factorial design consisting of dietary crude fibre(CF) at 2.0, 4.0 and 6.0% levels by adding grass meal and with or without grit supplementation. A total of 720 1-d-old male goslings were randomly allocated into 36 pens of 20 goslings/pen(n=6 pens/treatment). At 21 d of age, GIT, blood samples and grit in gizzards were collected. Body weight(BW), empty BW(without GIT), average daily gain(ADG) and average daily feed intake(ADFI) were affected by CF levels and the medium(4.0%) had the highest value. Adding grit improved BW, empty BW, ADG and ADFI. CF affected relative weight or length of proventriculus, gizzard and duodenum. Increasing CF levels decreased jejunum villus height and affected caecal crypt depth and villus height to crypt depth ratio. Higher CF levels decreased serum triglyceride. A d ding grit increased relative weight of abdominal fat. Grit addition increased grit weight in gizzard and the ratio of grit in 0.45-1 and 1-2 mm while decreasing the ratio of grit < 0.45 and 2-3 mm. In conclusion, m oderate CF level and grit addition increased performance of goslings without interaction. Dietary CF levels affected the development of upper GIT and serum triglyceride. Grit needed by goslings should be less than 2 mm. Goslings' gizzard would accumulate grit from feed when other grit could not be acquired.
基金Funded by the National Basic Research Program of China (No.2009CB724403)the National Natural Science Foundation of China (No.51005116)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0837)the NUAA Research Funding (No. 2010236)
文摘CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optical microscope,scanning electron microscope and X-ray diffraction equipment were utilized to study the effects of heating temperature on the microstructure of the joining interface.The compressive strength of the brazed composite grits was also measured.The experimental results show that the atoms of Ti,Al,B and N have preferentially penetrated towards the joining interface of composite grits and filler alloy.The compounds of Ti-nitride,Ti-borides and Ti3AlN were formed in the reaction layer.Degradation effect was not made on the compressive strength of the CBN-AlN composite grits when the brazing process was carried out in the temperature range of 890-920 ℃.
基金the National Natural Science Foundation of China (No.50323008)
文摘Residual stresses of coated diamond grits were analyzed by a finite element unit cell model. Diamond grits coated with four types of metals,W,Mo,Ti,and Cr,were considered. The numerical results show that compressive stress occurs in the diamond particles and tensile stress occurs in the metal matrix; compressive stress is concentrated in the diamond sharp corner; interface stresses decrease by more than 1000 MPa with a metal interlayer; plastic deformation of the matrix begins near the sharp corner of diamond grits and extends toward the peripheral zone. Stress concentration dramatically decreases due to plastic deformation of the matrix. The deposition of transition metals on a diamond surface can dramatically promote the adhesion between diamond grits and the metal bond.
基金Funded by the National Key Research and Development Program of China(No.2016YFB1102204)the Major State Basic Research Development Program of China(973 Program)(No.2011CB013202)the National Natural Science Foundation of China(No.51175126)
文摘The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. The interacting scratch process for optical glass BK7 with the grit interval distance as the variable was simulated by the ABAQUS software of finite element simulation based on the energy fracture theory. Double grits interacting scratch test for optical glass BK7 was carried out on the DMG ULTRASONIC 70-5 linear, by which the reliability of finite element simulation was verified. The surface morphology of the workpiece was analyzed by scanning electron microscopy(SEM), which showed that the width of groove increased obviously with the increase of scratch depth and the grit interval distance. Results of the width of groove were consistent with the simulation results. The subsurface damage layer was analyzed by the method of HF acid etching, which showed that there was an area of cracks intersecting. The scratching force was measured by the threedimensional dynamometer of KISTLER, which showed that the second scratching force increased with the increase of scratching depth and the grit interval distance. The force in the second scratch was smaller than that in the first time, which was consistent with the Griffith fracture theory.
基金supported by the National Natural Science Foundation of China(No.51775275)the Fundamental Research Funds for the Central Universities(No.NE2014103 and No.NZ2016107)
文摘Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using ?nite element analysis, with a consideration of the nonuniform temperature distribution in the induction brazing model. The in?uences of induction brazing parameters on the residual stresses of polycrystalline CBN abrasive grits have been analyzed, including the embedding depth, grit side length, etc. Results obtained show that the tensile stress with a 40% embedding depth is 292 MPa, which is the minimum on the bonding interface compared with other embedding depths. Meanwhile, the maximum tensile stress is 575 MPa, with an increase of 59% compared with that of a grit side length of 50 mm. Finally, the simulation results of the brazing residual stress of polycrystalline CBN abrasive grits have been con?rmed valid based on the residual stress measurement of the brazed monocrystalline CBN grit.
