Electrochemical trepanning(ECTr)is an effective electrochemical machining(ECM)technique that can be used to manufacture the integral components of aero-engine compressors.This study focused on the dynamic evolution of...Electrochemical trepanning(ECTr)is an effective electrochemical machining(ECM)technique that can be used to manufacture the integral components of aero-engine compressors.This study focused on the dynamic evolution of ECTr for production of inner blisks(bladed disks)with a special chamfer structure at blade tip.Due to the existence of chamfer,the ECTr process of inner blades is in a non-equilibrium state during the early stages,and the physical field changes in the machining gap are complex,making it difficult to predict the forming process.In this paper,a dynamic evolution model(DEM)of inner blade ECTr with a special chamfer at blade tip structure is proposed,and an ECTr multi-physical fields simulation study was carried out.The evolution of the chamfer at blade tip was analyzed and data related to chamfer were predicted based on the dependence of anode boundary properties with machining time and feed rate.In addition,the dis-tributions of current density,electrolyte flow rate,bubble volume fraction,temperature rise,and electrolyte conductivity in the machining area at different times were obtained by combining them with the multi-physical fields simulation results.Subsequently,a series of ECTr experiments were conducted,in which,as the feed rate increased,the surface quality and machining accuracy of the inner blades were improved.Compared with the simulation results,the error in machining accu-racy of the chamfer profile is controlled within±2%,and the machining accuracy of the blade full profile was controlled within±0.2 mm,indicating that the model proposed in this study was effec-tive in predicting the evolution of inner blades ECTr with chamfer structures at blade tip.展开更多
The sloshing in a tank with a specific geometric shape containing fluid was modeled numerically to reduce its effects by applying a porous medium to the tank wall.The thickness and position of the porous layer and the...The sloshing in a tank with a specific geometric shape containing fluid was modeled numerically to reduce its effects by applying a porous medium to the tank wall.The thickness and position of the porous layer and the geometric shape of the tank were investigated as the main parameters to select an optimal approach to reduce the effects of sloshing.Different fluid tank filling percentages(H_(w)/H_(tot)) were evaluated.Results indicate that performance at H_(w)/H_(tot)=0.33 and two tank modes with and without a porous environment layer have the greatest impact on reducing sloshing.A thickness of 30 cm and placement on the side walls are determined to be the ideal thickness and location of the porous layer.A porous layer with a thickness(t)relative to the tank length at the middle(L_(m)),t L_(m)=0.1 applied to the side walls of the tank effectively reduces the pressure by 65%.This study provided suggestions for the aspect ratio of a chamfered tank designed against sloshing.展开更多
Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge ...Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge has a notable influence on the tool wear. Thus, a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge. The results indicate that, for a PCBN tool with a variable chamfered edge, the rake wear area is far from the cutting edge and slowly extends toward it. A shallow large-area crater wear occurs on the rake face, and the flank wear area has a long triangular shape with a smaller wear area and width, and the cutting edge remains in a good state during the cutting process. In contrast, for a PCBN tool with an invariable chamfered edge, a deep small-area crater appears on the rake face, and the wear area is close to the cutting edge and quickly extends toward it. Thus, it is easy for chips to accumulate in the crater, resulting in large-area and high-speed wear on the flank face. In addition, the tool shows a weak wear resistance. In the initial wear stage, the rake wear mechanism of the two cutting tools is a mixture of abrasive, oxidation, and other types of wear, whereas their flank wear mechanism is dominated by abrasive wear. With an aggravation of the tool wear, the oxidation and diffusion wear mechanism are both increasingly strengthened. The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and diffusion wear, as did the flank wear of the cutter with an invariable chamfered edge. This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.展开更多
In order to analyze the influence of the hole chamfer on the metering performances of a Multi-hole Orifice Flowmeter and optimize the related orifice structure,a multi-hole orifice flowmeter with DN80 and throttle rat...In order to analyze the influence of the hole chamfer on the metering performances of a Multi-hole Orifice Flowmeter and optimize the related orifice structure,a multi-hole orifice flowmeter with DN80 and throttle ratio of 0.45 was considered in the present study.The flow field characteristics were determined in the framework of a CFD technique.The results show that the multi-hole orifice flowmeter with filleting transition around the throttle orifice has higher accuracy in a wide range of the space of parameters,and is more suitable for accurate measurement of fluid in process control.展开更多
Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specim...Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.展开更多
Chamfered mould has gradually become a new technology equipment to eliminate transverse corner crack.However,longitudinal corner crack ratio of chamfered slab was very high.Solidification microstructure was detected i...Chamfered mould has gradually become a new technology equipment to eliminate transverse corner crack.However,longitudinal corner crack ratio of chamfered slab was very high.Solidification microstructure was detected in the area where the longitudinal corner crack occurred.Effect of narrow face shape and taper distribution of mould copper plate on longitudinal corner crack was studied by industrial tests.Water velocity distribution in the narrow copper plate was studied by numerical simulation.On the premise of preventing cooling water from nuclear boiling,improvement measures of mould cooling process and water seam structure were put forward through heat transfer calculation.The results showed that local taper of the meniscus region of mould should be increased to prevent generation of longitudinal corner crack.Chamfering slope length of narrow copper plate should be controlled within 55 mm,and chamfering angle should be controlled at about 30°.Average water velocity should be more than 7.0 m/s.The flat and chamfering regions of narrow copper plate working face should be designed as double taper and funnel structure,respectively.The water seam in the chamfering region should preferentially choose the combined cooling structure with two holes and one slot.In order to prevent the extension of longitudinal corner crack,chamfered narrow face foot roller should be used.展开更多
A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, th...A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, the laws and mechanisms that govern the effect of the chamfered wall on the performance of a Hall thruster are investigated. By applying both experimental measurement and particle-in-cell simulation, it is determined that there is a moderate chamfer angle that can further improve the optimal performance obtained with a straight channel. This is because the chamfering of the wall near the channel exit can enhance ion acceleration and effectively reduce ion recombination on the wall, which is favorable to the promotion of the thrust and efficiency. However, the chamfer angle should not be too large; otherwise, both the density of the propellant gas and the distribution of the plasma potential in the channel are influenced, which is undesirable for efficient propellant utilization and beam concentration. Therefore, it is suggested that the chamfer shape of the channel wall is an important factor that must be carefully considered in the design of Hall thrusters.展开更多
Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness.However,excessive ...Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness.However,excessive heat generation and resulting high cutting temperature eventually cause severe tool wear and poor surface integrity,which simultaneously limits the optimal selection of machining parameters.In the present study,an analytical thermal–mechanical model is proposed for the prediction of the three-dimensional(3-D)temperature field in cylindrical turning with chamfered round insert based on a modified slip-line field approach.First,an innovative discretization method is introduced in a general 3-D coordinate system to provide a comprehensive demonstration of the irregular cutting geometry and heat generation zones.Then,a plasticity-theory-based slip-line field model is developed and employed to determine the intensities and geometries of every elementary heat sources in Primary Deformation Zones(PDZ),Secondary Deformation Zones(SDZ)and Dead Metal Zones(DMZ).At last,a 3-D analytical model is suggested to calculate the temperature increases caused by the entire heat sources and associated images.The maximum cutting temperature region predicted is found existing upon the chip-tool contact area rather than the tool edge.Moreover,the rationalities of cutting parameters employed are analyzed along with theoretical material removal rates and ensuing maximum cutting temperatures.The results indicate that the cutting conditions with large depth of cut and high cutting speed are more desirable than those with high feed rates.The proposed models are respectively verified through a series of 3-D Finite Element(FE)simulations and dry cutting experiments of Inconel 718 with chamfered round insert.Satisfactory agreement has been reached between the predictions and simulations as well as the measurements,which confirms the correctness and effectiveness of the presented analytical model.展开更多
To date, the selection of the magnetic field line used to match the chamfered inner and outer channel walls in a magnetically shielded Hall thruster has not been quantitatively studied. Hence, an experimental study wa...To date, the selection of the magnetic field line used to match the chamfered inner and outer channel walls in a magnetically shielded Hall thruster has not been quantitatively studied. Hence, an experimental study was conducted on a 1.35 k W magnetically shielded Hall thruster with a xenon propellant. Different magnetic field lines were chosen, and corresponding tangentially matched channel walls were manufactured and utilized. The results demonstrate that high performance and a qualified anti-sputtering effect cannot be achieved simultaneously. When the magnetic field lines that match the chamfered wall have a strength at the channel centerline of less than 12% of the maximum field strength, the channel wall can be adequately protected from ion sputtering. When the magnetic field lines have a strength ratio of 12%–20%, the thruster performance is high. These findings provide the first significant quantitative design reference for the match between the magnetic field line and chamfered channel wall in magnetically shielded Hall thrusters.展开更多
The surface quality of chamfer milling of stainless steel is closed related to the products of 3 C(Computer, Communication and Consumer electronics), where a cutter is a major part to achieve that. Targeting a high-qu...The surface quality of chamfer milling of stainless steel is closed related to the products of 3 C(Computer, Communication and Consumer electronics), where a cutter is a major part to achieve that. Targeting a high-quality cutter,an experimental evaluation is carried out on the influence of grinding texture of cutter flank face on surface quality.The mathematic models of chamfer cutter are established, and they are validated by a numerical simulation. Also the grinding data are generated by the models and tested by a grinding simulation for safety reasons. Then, a set of chamfer cutting tools are machined in a five-axis CNC grinding machine, and consist of five angles between the cutting edge and the grinding texture on the 1 st flank faces, i.e., 0°, 15°, 30°, 45° and 60°. Furthermore, the machined cutting tools are tested in a series of milling experiments of chamfer hole of stainless steel, where cutting forces and surface morphologies are measured and observed. The results show that the best state of both surface quality and cutting force is archived by the tool with 45° grinding texture, which can provide a support for manufacturing of cutting tool used in chamfer milling.展开更多
To improve the flexural properties of Beetle Elytron Plates(BEPs)and clarify the effect of the transition arcs(chamfers)between the skins and the trabeculae,the chamfers were set in BEPs,and then the influence of the ...To improve the flexural properties of Beetle Elytron Plates(BEPs)and clarify the effect of the transition arcs(chamfers)between the skins and the trabeculae,the chamfers were set in BEPs,and then the influence of the chamfer on BEPs'mechanical properties was investigated via experimentation and the Finite Elemnent Method simulation(FEM).The results indicate that the influence of the chamfer on the flexural properties and ductility was most obvious in the Trabecular Beetle Elytron Plates(TBEPs),less obvious in the Honeycomb Plates(HPs)and basically no efiect was observed on End-trabecular Beetle Elytron Plates(EBEPs).The chamfer can improve the mechanical stability of EBEPSs.As the chamfer diameter increased in the BEPs,the length of the residual trabecular root on the skin increased when failure occurred in the TBEPs.The crack position in the honeycomb wallsof the HPs gradually shifted from the skin to the center.The EBEPs continued to exhibit oblique cracks.From the perspective of the force characteristics of these BEPs.combined with numerical simulation,the influence mechanism of the chamfer on their flcxural propertics was investigated.展开更多
Roller is an important workpiece of automatic spinning machine. Only if the chamferR on the root bottom of roller＇s guide pillar meets processing accuracy requirement can the end face of one roller＇s guide pillar ma...Roller is an important workpiece of automatic spinning machine. Only if the chamferR on the root bottom of roller＇s guide pillar meets processing accuracy requirement can the end face of one roller＇s guide pillar match the correct position of another roller＇s end face on the guide hole. Therefore, the size of chamfer R on the root bottomof the roller＇s guide pillar has an important influence on the operating state of automatic spinning machine. In order to achieve the rapid, automatic and precise measurement of chamfer R on the root bottom of roller, an auto detection system }＇or roller~ s chamfer based on computer vision technology is proposed. Firstly, the principle of measurement based on computer vision technology is introduced. And then the extraction method of charnfer^s characteristic parameters is presented, which uses image processing technique to obtain these characteristic parameters by means of collected images of roller contour, including extraction of region of interest, extraction of subpixel precise edge, segmentation of arc and line, fittingof geometric primitives, etc. Finally, after experimental verification, the measurement error is within ＋ 5 μm and repeated accuracy is 0.1 pm. The results show that this measurement method is applicable to not only the chamfer on the textile workpiece, but also the workpieces of shaft type with various of sizes.展开更多
Y9420 Gear Chamfering Machine is ahigh efficiency machine tool designedby the Chongqing Machine ToolsWorks to meet market demand. The machineemploys the principle of cool extrusion anduses a special chamfering tool wh...Y9420 Gear Chamfering Machine is ahigh efficiency machine tool designedby the Chongqing Machine ToolsWorks to meet market demand. The machineemploys the principle of cool extrusion anduses a special chamfering tool which drivesthe work piece to rotate and achievechamfering. It features no tool tracks and noburr on the ends. Multiple cutters can beused to process cluster gears, and thechamfering can be realized on either oneside of the tooth or on both. It is an idealpiece of equipment for automobiles, machinetools and gears manufacture to chamfer anddeburr disk type gears, spur and helical shaftgears and cluster gears.展开更多
A novel algorithm for localising a robot in a known two-dimensional environment is presented in this paper. An occupancy grid representing the environment is first converted to a distance function that encodes the dis...A novel algorithm for localising a robot in a known two-dimensional environment is presented in this paper. An occupancy grid representing the environment is first converted to a distance function that encodes the distance to the nearest obstacle from any given location. A Chamfer distance based sensor model to associate observations from a laser ranger finder to the map of the environment without the need for ray tracing, data association, or feature extraction is presented. It is shown that the robot can be localised by solving a non-linear optimisation problem formulated to minimise the Chamfer distance with respect to the robot location. The proposed algorithm is able to perform well even when robot odometry is unavailable and requires only a single tuning parameter to operate even in highly dynamic environments. As such, it is superior than the state-of-the-art particle filter based solutions for robot localisation in occupancy grids, provided that an approximate initial location of the robot is available. Experimental results based on simulated and public domain datasets as well as data collected by the authors are used to demonstrate the effectiveness of the proposed algorithm.展开更多
In the multilayer film-substrate system,thermal stress concentration and stress mutations cause film buckling,delamination and cracking,leading to device failure.In this paper,we investigated a multilayer film system ...In the multilayer film-substrate system,thermal stress concentration and stress mutations cause film buckling,delamination and cracking,leading to device failure.In this paper,we investigated a multilayer film system composed of a substrate and three film layers.The thermal stress distribution inside the structure was calculated by the finite element method,revealing significant thermal stress differences between the layers.This is mainly due to the mismatch of the coefficient of thermal expansion between materials.Different materials respond differently to changes in external temperature,leading to compression between layers.There are obvious thermal stress concentration points at the corners of the base layer and the transition layer,which is due to the sudden change of the shape at the geometric section of the structure,resulting in a sudden increase in local stress.To address this issue,we chamfered the substrate and added an intermediate layer between the substrate and the transition layer to assess whether these modifications could reduce or eliminate the thermal stress concentration points and extend the service life of the multilayer structure.The results indicate that chamfering and adding the intermediate layer effectively reduce stress discontinuities and mitigate thermal stress concentration points,thereby improving interlayer bonding strength.展开更多
基金the National Nature Science Foundation of China (52275435)the National Natural Science Foundation of China for Creative Research Groups (51921003)the National Science and Technology Major Project (2017-VII-0004-0097).
文摘Electrochemical trepanning(ECTr)is an effective electrochemical machining(ECM)technique that can be used to manufacture the integral components of aero-engine compressors.This study focused on the dynamic evolution of ECTr for production of inner blisks(bladed disks)with a special chamfer structure at blade tip.Due to the existence of chamfer,the ECTr process of inner blades is in a non-equilibrium state during the early stages,and the physical field changes in the machining gap are complex,making it difficult to predict the forming process.In this paper,a dynamic evolution model(DEM)of inner blade ECTr with a special chamfer at blade tip structure is proposed,and an ECTr multi-physical fields simulation study was carried out.The evolution of the chamfer at blade tip was analyzed and data related to chamfer were predicted based on the dependence of anode boundary properties with machining time and feed rate.In addition,the dis-tributions of current density,electrolyte flow rate,bubble volume fraction,temperature rise,and electrolyte conductivity in the machining area at different times were obtained by combining them with the multi-physical fields simulation results.Subsequently,a series of ECTr experiments were conducted,in which,as the feed rate increased,the surface quality and machining accuracy of the inner blades were improved.Compared with the simulation results,the error in machining accu-racy of the chamfer profile is controlled within±2%,and the machining accuracy of the blade full profile was controlled within±0.2 mm,indicating that the model proposed in this study was effec-tive in predicting the evolution of inner blades ECTr with chamfer structures at blade tip.
文摘The sloshing in a tank with a specific geometric shape containing fluid was modeled numerically to reduce its effects by applying a porous medium to the tank wall.The thickness and position of the porous layer and the geometric shape of the tank were investigated as the main parameters to select an optimal approach to reduce the effects of sloshing.Different fluid tank filling percentages(H_(w)/H_(tot)) were evaluated.Results indicate that performance at H_(w)/H_(tot)=0.33 and two tank modes with and without a porous environment layer have the greatest impact on reducing sloshing.A thickness of 30 cm and placement on the side walls are determined to be the ideal thickness and location of the porous layer.A porous layer with a thickness(t)relative to the tank length at the middle(L_(m)),t L_(m)=0.1 applied to the side walls of the tank effectively reduces the pressure by 65%.This study provided suggestions for the aspect ratio of a chamfered tank designed against sloshing.
基金Supported by National Natural Science Foundation of China(Grant No.51475125)Heilongjiang Provincial Natural Science Foundation of China(Grant No.E2016047)
文摘Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge has a notable influence on the tool wear. Thus, a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge. The results indicate that, for a PCBN tool with a variable chamfered edge, the rake wear area is far from the cutting edge and slowly extends toward it. A shallow large-area crater wear occurs on the rake face, and the flank wear area has a long triangular shape with a smaller wear area and width, and the cutting edge remains in a good state during the cutting process. In contrast, for a PCBN tool with an invariable chamfered edge, a deep small-area crater appears on the rake face, and the wear area is close to the cutting edge and quickly extends toward it. Thus, it is easy for chips to accumulate in the crater, resulting in large-area and high-speed wear on the flank face. In addition, the tool shows a weak wear resistance. In the initial wear stage, the rake wear mechanism of the two cutting tools is a mixture of abrasive, oxidation, and other types of wear, whereas their flank wear mechanism is dominated by abrasive wear. With an aggravation of the tool wear, the oxidation and diffusion wear mechanism are both increasingly strengthened. The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and diffusion wear, as did the flank wear of the cutter with an invariable chamfered edge. This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.
基金supports of Hebei province high-tech industry multiplier project(No.16211702D)Chengde science and technology&development project(No.20152013).
文摘In order to analyze the influence of the hole chamfer on the metering performances of a Multi-hole Orifice Flowmeter and optimize the related orifice structure,a multi-hole orifice flowmeter with DN80 and throttle ratio of 0.45 was considered in the present study.The flow field characteristics were determined in the framework of a CFD technique.The results show that the multi-hole orifice flowmeter with filleting transition around the throttle orifice has higher accuracy in a wide range of the space of parameters,and is more suitable for accurate measurement of fluid in process control.
基金This study was funded by the National Natural Science Foundation of China(Nos.51878354&51308301)the Natural Science Foundation of Jiangsu Province(Nos.BK20181402&BK20130978)+2 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX20_0885)Six talent peak high-level projects of Jiangsu Province(No.JZ-029)Qinglan Project of Jiangsu Higher Education Institutions.
文摘Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.
文摘Chamfered mould has gradually become a new technology equipment to eliminate transverse corner crack.However,longitudinal corner crack ratio of chamfered slab was very high.Solidification microstructure was detected in the area where the longitudinal corner crack occurred.Effect of narrow face shape and taper distribution of mould copper plate on longitudinal corner crack was studied by industrial tests.Water velocity distribution in the narrow copper plate was studied by numerical simulation.On the premise of preventing cooling water from nuclear boiling,improvement measures of mould cooling process and water seam structure were put forward through heat transfer calculation.The results showed that local taper of the meniscus region of mould should be increased to prevent generation of longitudinal corner crack.Chamfering slope length of narrow copper plate should be controlled within 55 mm,and chamfering angle should be controlled at about 30°.Average water velocity should be more than 7.0 m/s.The flat and chamfering regions of narrow copper plate working face should be designed as double taper and funnel structure,respectively.The water seam in the chamfering region should preferentially choose the combined cooling structure with two holes and one slot.In order to prevent the extension of longitudinal corner crack,chamfered narrow face foot roller should be used.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51507040,51777045 and 51736003)the Fundamental Research Funds for the Central Universities,China(Grant No.HIT.NSRIF.2015079)the Research Program,China(Grant No.JSZL2016203C006)
文摘A discharge channel with a chamfered wall not only has application in the design of modern Hall thrusters, but also exists where the channel wall is eroded, and so is a common status for these units. In this paper, the laws and mechanisms that govern the effect of the chamfered wall on the performance of a Hall thruster are investigated. By applying both experimental measurement and particle-in-cell simulation, it is determined that there is a moderate chamfer angle that can further improve the optimal performance obtained with a straight channel. This is because the chamfering of the wall near the channel exit can enhance ion acceleration and effectively reduce ion recombination on the wall, which is favorable to the promotion of the thrust and efficiency. However, the chamfer angle should not be too large; otherwise, both the density of the propellant gas and the distribution of the plasma potential in the channel are influenced, which is undesirable for efficient propellant utilization and beam concentration. Therefore, it is suggested that the chamfer shape of the channel wall is an important factor that must be carefully considered in the design of Hall thrusters.
基金partially supported by the National Natural Science Foundation of China(No.51705385)the National Defense Pre-Research Foundation of China(No.61400020108)the Excellent Dissertation Cultivation Funds of Wuhan University of Technology of China(No.2018-YS-034)。
文摘Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness.However,excessive heat generation and resulting high cutting temperature eventually cause severe tool wear and poor surface integrity,which simultaneously limits the optimal selection of machining parameters.In the present study,an analytical thermal–mechanical model is proposed for the prediction of the three-dimensional(3-D)temperature field in cylindrical turning with chamfered round insert based on a modified slip-line field approach.First,an innovative discretization method is introduced in a general 3-D coordinate system to provide a comprehensive demonstration of the irregular cutting geometry and heat generation zones.Then,a plasticity-theory-based slip-line field model is developed and employed to determine the intensities and geometries of every elementary heat sources in Primary Deformation Zones(PDZ),Secondary Deformation Zones(SDZ)and Dead Metal Zones(DMZ).At last,a 3-D analytical model is suggested to calculate the temperature increases caused by the entire heat sources and associated images.The maximum cutting temperature region predicted is found existing upon the chip-tool contact area rather than the tool edge.Moreover,the rationalities of cutting parameters employed are analyzed along with theoretical material removal rates and ensuing maximum cutting temperatures.The results indicate that the cutting conditions with large depth of cut and high cutting speed are more desirable than those with high feed rates.The proposed models are respectively verified through a series of 3-D Finite Element(FE)simulations and dry cutting experiments of Inconel 718 with chamfered round insert.Satisfactory agreement has been reached between the predictions and simulations as well as the measurements,which confirms the correctness and effectiveness of the presented analytical model.
基金funded by National Natural Science Foundation of China (Nos. 52076054 and 51736003)Civil Aerospace Technology Pre-research Project (No. D03015)Defense Industrial Technology Development Program (No. JCKY2019603B005)。
文摘To date, the selection of the magnetic field line used to match the chamfered inner and outer channel walls in a magnetically shielded Hall thruster has not been quantitatively studied. Hence, an experimental study was conducted on a 1.35 k W magnetically shielded Hall thruster with a xenon propellant. Different magnetic field lines were chosen, and corresponding tangentially matched channel walls were manufactured and utilized. The results demonstrate that high performance and a qualified anti-sputtering effect cannot be achieved simultaneously. When the magnetic field lines that match the chamfered wall have a strength at the channel centerline of less than 12% of the maximum field strength, the channel wall can be adequately protected from ion sputtering. When the magnetic field lines have a strength ratio of 12%–20%, the thruster performance is high. These findings provide the first significant quantitative design reference for the match between the magnetic field line and chamfered channel wall in magnetically shielded Hall thrusters.
基金Supported by Heilongjiang Provincial Natural Science Foundation of China(Grant No.QC2016070)
文摘The surface quality of chamfer milling of stainless steel is closed related to the products of 3 C(Computer, Communication and Consumer electronics), where a cutter is a major part to achieve that. Targeting a high-quality cutter,an experimental evaluation is carried out on the influence of grinding texture of cutter flank face on surface quality.The mathematic models of chamfer cutter are established, and they are validated by a numerical simulation. Also the grinding data are generated by the models and tested by a grinding simulation for safety reasons. Then, a set of chamfer cutting tools are machined in a five-axis CNC grinding machine, and consist of five angles between the cutting edge and the grinding texture on the 1 st flank faces, i.e., 0°, 15°, 30°, 45° and 60°. Furthermore, the machined cutting tools are tested in a series of milling experiments of chamfer hole of stainless steel, where cutting forces and surface morphologies are measured and observed. The results show that the best state of both surface quality and cutting force is archived by the tool with 45° grinding texture, which can provide a support for manufacturing of cutting tool used in chamfer milling.
基金funded by the National Key R&D Program of China(Grant No.2017YFC0703700).
文摘To improve the flexural properties of Beetle Elytron Plates(BEPs)and clarify the effect of the transition arcs(chamfers)between the skins and the trabeculae,the chamfers were set in BEPs,and then the influence of the chamfer on BEPs'mechanical properties was investigated via experimentation and the Finite Elemnent Method simulation(FEM).The results indicate that the influence of the chamfer on the flexural properties and ductility was most obvious in the Trabecular Beetle Elytron Plates(TBEPs),less obvious in the Honeycomb Plates(HPs)and basically no efiect was observed on End-trabecular Beetle Elytron Plates(EBEPs).The chamfer can improve the mechanical stability of EBEPSs.As the chamfer diameter increased in the BEPs,the length of the residual trabecular root on the skin increased when failure occurred in the TBEPs.The crack position in the honeycomb wallsof the HPs gradually shifted from the skin to the center.The EBEPs continued to exhibit oblique cracks.From the perspective of the force characteristics of these BEPs.combined with numerical simulation,the influence mechanism of the chamfer on their flcxural propertics was investigated.
基金National Science and Technology Major Project of China(No.2016ZX04003001)High-tech Ship Research Project(1st phase of Low-speed Marine Engine Engineering)
文摘Roller is an important workpiece of automatic spinning machine. Only if the chamferR on the root bottom of roller＇s guide pillar meets processing accuracy requirement can the end face of one roller＇s guide pillar match the correct position of another roller＇s end face on the guide hole. Therefore, the size of chamfer R on the root bottomof the roller＇s guide pillar has an important influence on the operating state of automatic spinning machine. In order to achieve the rapid, automatic and precise measurement of chamfer R on the root bottom of roller, an auto detection system }＇or roller~ s chamfer based on computer vision technology is proposed. Firstly, the principle of measurement based on computer vision technology is introduced. And then the extraction method of charnfer^s characteristic parameters is presented, which uses image processing technique to obtain these characteristic parameters by means of collected images of roller contour, including extraction of region of interest, extraction of subpixel precise edge, segmentation of arc and line, fittingof geometric primitives, etc. Finally, after experimental verification, the measurement error is within ＋ 5 μm and repeated accuracy is 0.1 pm. The results show that this measurement method is applicable to not only the chamfer on the textile workpiece, but also the workpieces of shaft type with various of sizes.
文摘Y9420 Gear Chamfering Machine is ahigh efficiency machine tool designedby the Chongqing Machine ToolsWorks to meet market demand. The machineemploys the principle of cool extrusion anduses a special chamfering tool which drivesthe work piece to rotate and achievechamfering. It features no tool tracks and noburr on the ends. Multiple cutters can beused to process cluster gears, and thechamfering can be realized on either oneside of the tooth or on both. It is an idealpiece of equipment for automobiles, machinetools and gears manufacture to chamfer anddeburr disk type gears, spur and helical shaftgears and cluster gears.
文摘A novel algorithm for localising a robot in a known two-dimensional environment is presented in this paper. An occupancy grid representing the environment is first converted to a distance function that encodes the distance to the nearest obstacle from any given location. A Chamfer distance based sensor model to associate observations from a laser ranger finder to the map of the environment without the need for ray tracing, data association, or feature extraction is presented. It is shown that the robot can be localised by solving a non-linear optimisation problem formulated to minimise the Chamfer distance with respect to the robot location. The proposed algorithm is able to perform well even when robot odometry is unavailable and requires only a single tuning parameter to operate even in highly dynamic environments. As such, it is superior than the state-of-the-art particle filter based solutions for robot localisation in occupancy grids, provided that an approximate initial location of the robot is available. Experimental results based on simulated and public domain datasets as well as data collected by the authors are used to demonstrate the effectiveness of the proposed algorithm.
基金the support of the National Natural Science Foundation of China(Grant Nos.51606158,11604311 and 12074151)the Guangxi Science and Technology Base and Talent Special Project(Grant No.AD21075009)+2 种基金the Sichuan Science and Technology Program(Grant No.2021JDRC0022)the Open Fund of the Key Laboratory for Metallurgical Equipment and Control Technology of Ministry of Education in Wuhan University of Science and Technology,People's Republic of China(Grant Nos.MECOF2022B01 and MECOF2023B04)the Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology(Grant No.DH202321)。
文摘In the multilayer film-substrate system,thermal stress concentration and stress mutations cause film buckling,delamination and cracking,leading to device failure.In this paper,we investigated a multilayer film system composed of a substrate and three film layers.The thermal stress distribution inside the structure was calculated by the finite element method,revealing significant thermal stress differences between the layers.This is mainly due to the mismatch of the coefficient of thermal expansion between materials.Different materials respond differently to changes in external temperature,leading to compression between layers.There are obvious thermal stress concentration points at the corners of the base layer and the transition layer,which is due to the sudden change of the shape at the geometric section of the structure,resulting in a sudden increase in local stress.To address this issue,we chamfered the substrate and added an intermediate layer between the substrate and the transition layer to assess whether these modifications could reduce or eliminate the thermal stress concentration points and extend the service life of the multilayer structure.The results indicate that chamfering and adding the intermediate layer effectively reduce stress discontinuities and mitigate thermal stress concentration points,thereby improving interlayer bonding strength.
