A computer aided measurement system is used to measure the cutting temperature directly in high-speed machining by natural thermocouples and standard thermocouples. In this system the tool/workpiece interface temperat...A computer aided measurement system is used to measure the cutting temperature directly in high-speed machining by natural thermocouples and standard thermocouples. In this system the tool/workpiece interface temperature is measured by the tool/workpiece natural thermocouple, while the temperature distribution on the workpiece surface and that of interior are measured by some standard thermocouples prearranged at proper positions. The system can be used to measure cutting temperature in the machining with the rotary cutting tools, such as vertical drill and end milling cutter. It is practically used for the research on high-speed milling with hardened steel.展开更多
In high-speed cutting, natural thermocouple, artificial thermocouple and infrared radiation temperature measurement are usually adopted for measuring cutting temperature, but these methods have difficulty in measuring...In high-speed cutting, natural thermocouple, artificial thermocouple and infrared radiation temperature measurement are usually adopted for measuring cutting temperature, but these methods have difficulty in measuring transient temperature accurately of cutting area on account of low response speed and limited cutting condition. In this paper, NiCr/NiSi thin-film thermocouples（TFTCs） are fabricated according to temperature characteristic of cutting area in high-speed cutting by means of advanced twinned microwave electro cyclotron resonance（MW-ECR） plasma source enhanced radio frequency（RF） reaction non-balance magnetron sputtering technique, and can be used for transient cutting temperature measurement. The time constants of the TFTCs with different thermo-junction film width are measured at four kinds of sampling frequency by using Ultra-CFR short pulsed laser system that established. One-dimensional unsteady heat conduction model is constructed and the dynamic performance is analyzed theoretically. It can be seen from the analysis results that the NiCr/NiSi TFTCs are suitable for measuring transient temperature which varies quickly, the response speed of TFTCs can be obviously improved by reducing the thickness of thin-film, and the area of thermo-junction has little influence on dynamic response time. The dynamic calibration experiments are made on the constructed dynamic calibration system, and the experimental results confirm that sampling frequency should be larger than 50 kHz in dynamic measurement for stable response time, and the shortest response time is 0.042 ms. Measurement methods and devices of cutting heat and cutting temperature measurement are developed and improved by this research, which provide practical methods and instruments in monitoring cutting heat and cutting temperature for research and production in high-speed machining.展开更多
A study was undertaken to investigate the performan ce of PCBN tool in the finish turning GCr15 bearing steel with different hardness between 30～64 HRC. The natural thermocouple was used to measure the cutting tem p ...A study was undertaken to investigate the performan ce of PCBN tool in the finish turning GCr15 bearing steel with different hardness between 30～64 HRC. The natural thermocouple was used to measure the cutting tem p erature, tool life and cutting temperature were investigated and compared. The m aterial can be heated by this instrument which using low voltage and high elec trical current, while PCBN can’t be heated by electrifying directly, so the ke ntanium layer coating over the PCBN is heated, so the PCBN is heated and its th ermoelectric property is got by this method. [TPP129,+60mm88mm,Y,PZ#] Fig.1 Effect of cutting depth and workpiec hardness on. the cutting temperatureThe objective was to determine the influence of the workpiece hardness on change s in cutting temperature and tool wear characterize. It can be found from Fig.1 that the cutting temperature show an increasing tendency with the improvement of workpiece hardness within the cutting speed scope when the workpiece hardness i s under HRC50. And on the other hand, it is found that the cutting temperature s how the downtrend with the improvement of workpiece hardness when the workpiece hardness is over HRC50. According to experimental results, the critical hard ness when turning hardened GCr15 bearing steel with PCBN tool is about HRC50. Th e wear causes of PCBN tool have been found out through taking photos on the micr o-shape of PCBN poly-laminate initial surface as well as face and flank of wea r tool and analysis on chemical elements. It is discovered that the PCBN tools a re not suitable for cutting the workpiece at nearly critical hardness, because n ear the critical hardness, PCBN wear at the highest speed. For researching the w ear rule of PCBN tool, the tool wear experiments have been carried on by using b earing steel GCr15 at hardness HRC40 and HRC60 with changing cutting speed. The indexes of tool life equations is gained under two kinds of conditions w hich are bigger than 0.6, so the effects of cutting speed on the PCBN tool are m uch less than that of carbide tool and ceramic tool.展开更多
Pure iron is one of the difficult-to-machine materials due to its large chip deformation,adhesion,work-hardening,and built-up edges formation during machining.This leads to a large workpiece deformation and challenge ...Pure iron is one of the difficult-to-machine materials due to its large chip deformation,adhesion,work-hardening,and built-up edges formation during machining.This leads to a large workpiece deformation and challenge to meet the required technical indicators.Therefore,under varying the grain size of pure iron,the influence of cutting speed,feed,and depth of cut on the cutting force,heat generation,and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material.The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent.However,the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.展开更多
A parametric model of cutting temperature generated in end milling process is developed according to the thermal mechanism of end milling as an intermittent operation, which periodically repeats the cycle of heating u...A parametric model of cutting temperature generated in end milling process is developed according to the thermal mechanism of end milling as an intermittent operation, which periodically repeats the cycle of heating under cutting and cooling under non-cutting. It shows that cutting speed and the tool-workpiece engagement condition are determinative for tool temperature in the operation. The suggested model was investigated by tests of AlTiN coated endmill machining hardened die steel JIS SKD61, where cutting temperature on the flank face of tool was measured with an optical fiber type radiation thermometer. Experimental results show that the tendency of cutting temperature to increase with cutting speed and engagement angle is intensified with the progressing tool wear.展开更多
A thermoelectric curve of GCr15 BN500 is acquired by rapid label way. The study on measuring the cutting temperature with PCBN cutter is done and the calculation formula is achieved. A series of experiments about cut...A thermoelectric curve of GCr15 BN500 is acquired by rapid label way. The study on measuring the cutting temperature with PCBN cutter is done and the calculation formula is achieved. A series of experiments about cutting temperature are made for different hardness tempering bearing steel at the same time. The rule that cutting temperature increases with increasing of the cutting speed, feed, back engagement of the cutting edge is gained. It is known that the cutting temperature is highest under the condition that back engagement of the cutting edge a p≥2.5 mm and the machined material hardness equals to 50HRC.展开更多
According to work tool thermocouple principle,the equipment for measuring hobbing temperature is developed.The changing character of cutting temperature in gear hobbing,the relation between cutting conditions and hob...According to work tool thermocouple principle,the equipment for measuring hobbing temperature is developed.The changing character of cutting temperature in gear hobbing,the relation between cutting conditions and hobbing temperature,and the influence of cutting conditions on hobbing temperature are discussed by means of experiments.All these have provided the reference standards for the equitably selecting cutting conditions and geometrical parameter of hob,prolonging the life of gear hobs,and predicting processes of gear hobbing.展开更多
The ADC12 aluminum alloy is prone to severe tool wear and high cutting heat during high-speed milling because of its high hardness.This study analyzes the highspeed milling process from the perspective of different ch...The ADC12 aluminum alloy is prone to severe tool wear and high cutting heat during high-speed milling because of its high hardness.This study analyzes the highspeed milling process from the perspective of different chip morphologies.The influence of cutting temperature on chip morphology was expounded.A two-dimensional orthogonal cutting model was established for finite element analysis(FEA)of high-speed milling of ADC12 aluminum alloy.A theoretical analysis model of cutting force and cutting temperature was proposed based on metal cutting theory.The variations in chip shape,cutting force,and cutting temperature with cutting speed increasing were analyzed via FEA.The results show that,with the increase in cutting speed,the chip morphology changes from continuous to serrated,and then back to continuous.The serrated chip is weakened and the cutting temperature is lowered when the speed is lower than 600 m·min^(-1)or higher than 1800 m·min^(-1).This study provides a reference for reducing cutting temperature,controlling chip morphology and improving cutting tool life.展开更多
Wear of cutting tools is a big concern for industrial manufacturers, because of their acquisition cost as well as the impact on the production lines when they are unavailable. Law of wear is very important in determin...Wear of cutting tools is a big concern for industrial manufacturers, because of their acquisition cost as well as the impact on the production lines when they are unavailable. Law of wear is very important in determining cutting tools lifespan, but most of the existing models don’t take into account the cutting temperature. In this work, the theoretical and experimental results of a dynamic study of metal machining against cutting temperature of a treated steel of grade S235JR with a high-speed steel tool are provided. This study is based on the analysis of two complementary approaches, an experimental approach with the measurement of the temperature and on the other hand, an approach using modeling. Based on unifactorial and multifactorial tests (speed of cut, feed, and depth of cut), this study allowed the highlighting of the influence of the cutting temperature on the machining time. To achieve this objective, two specific approaches have been selected. The first was to measure the temperature of the cutting tool and the second was to determine the wear law using Rayleigh-Ham dimensional analysis method. This study permitted the determination of a law that integrates the cutting temperature in the calculations of the lifespan of the tools during machining.展开更多
In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite ele...In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA) model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, -10°, 0°, 10°, 20°, and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed) have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM) of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface’s friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.展开更多
The mathematical model on the temperature of the waved-edge is constructedaccording to Jaeger's theory of moving solid and based on the used temperature model of the flatinsert. It is possible to forecast the mill...The mathematical model on the temperature of the waved-edge is constructedaccording to Jaeger's theory of moving solid and based on the used temperature model of the flatinsert. It is possible to forecast the milling temperature through programming. The comparableexperiments have been done between the two new three-dimension groove inserts (waved-edge insert,great edge insert) and flat fake insert. The theoretic forecast is in good agreement with theexperimental result. According to the cutting conditions, the boundary condition of finite elementanalysis on cutting temperature field is established, and the three-dimensional temperature fieldsof inserts with grooves are analyzed by FEM, so as to offer a reference basis for the design andoptimization of insert grooves.展开更多
The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularl...The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6Al-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth（KT） and average flank wear width（VB） firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50% and 55%,respectively.Under the given conditions,the optimum hydrogen content is 0.26%.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.展开更多
Ti2AlNb intermetallic alloy is a newly developed high-temperature resistant structural material due to its excellent material and mechanical properties,which also make it to be one of the most difficult-to-cut materia...Ti2AlNb intermetallic alloy is a newly developed high-temperature resistant structural material due to its excellent material and mechanical properties,which also make it to be one of the most difficult-to-cut materials.In order to study the machinability of Ti2AlNb alloy,a series of turning experiments of Ti2AlNb alloy with varying cutting speed and feed rate using coated carbide tools are carried out.The results associated with cutting forces,cutting temperature and tool wear are presented and discussed.Moreover,the cutting performance of Ti2AlNb alloy is evaluated in comparison with that of most commonly used Ti6Al4 Vand Inconel 718 alloys in terms of the cutting forces and cutting temperature.The comparison results show that there is a correlation between the machinability and the mechanical properties of work material properties.Additionally,considering material removal rate and tool life,the optimized machining parameters for cutting Ti2AlNb alloys using coated carbide tools are recommended.展开更多
Carbon fiber reinforced silicon carbide matrix(Cf/SiC)composites have the most potential application for high-temperature components of aerospace high-end equipment.However,high cutting temperature,rapid tool wear and...Carbon fiber reinforced silicon carbide matrix(Cf/SiC)composites have the most potential application for high-temperature components of aerospace high-end equipment.However,high cutting temperature,rapid tool wear and severe surface damages are the main problems in dry cutting Cf/SiC composites process.The feasibility study on cryogenic milling of Cf/SiC composites using liquid nitrogen as coolant is investigated.Influences of milling parameters and coolant on temperature,cutting force,surface quality and tool wear are investigated,which is compared with dry cutting.Experimental results reveal that the cutting temperature in cryogenic milling of Cf/SiC composites is reduced by about 40%—60%compared with dry cutting.The milling force increases gradually with the increase of spindle speed,feed rate,depth and width of milling in cryogenic milling process.In addition,the machined surface quality in cryogenic milling is superior to that in dry cutting process.Fiber fracture,matrix damage and fiber matrix debonding are main material removal mechanisms.Flank face wear is the main wear form of the polycrystalline diamond(PCD)end mills.The tool life is prolonged in the cryogenic milling process because the reduced temperature inhibits the softening of Co binder and phase transition of diamond in the PCD end mills.展开更多
The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain s...The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain sizes and geometries, and carbide tools with and without coatings were used in the experiments. Milling forces, milling temperatures, tool lifetimes, tool wear, and machined surface integrities were investigated. The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool, while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiA1N-eoated tool. A cutting force of 300 N per millimeter of the cutting edge （300 N/mm） was measured. This caused excessive tool chipping. The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool, while that of the TiA1N-coated tool was 12% lower than that of the uncoated carbide tool. The cutting temperatures produced when using water-based cooling and minimal quantity lubrication （MQL） were reduced by 100 ~C and 200 ~C, compared with those recorded with dry cutting, respectively. In general, the PCD tool lifetimes were 2--3 times longer than the carbide tool lifetimes. The roughness Ra of the machined surface was less than 0.6μm, and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached. The PCD tool with a 0.8 mm tool nose radius, 0% rake angle, 10% flank angle, and grain size of （30＋2） μm exhibited the best cutting performance. For this specific tool, a lifetime of 16 rain can be expected.展开更多
A finite element model was established for analyzing the geometric errors in turning operations and a two-step analyzing process was proposed. In the first analyzing step, the cutting force and the cutting heat for th...A finite element model was established for analyzing the geometric errors in turning operations and a two-step analyzing process was proposed. In the first analyzing step, the cutting force and the cutting heat for the cutting conditions were obtained using the AdvantEdge. Also, the deformation of a workpiece was estimated in the second step using the ANSYS. The deformation was analyzed for a 150 mm-long workpiece at three different measuring points, such as 10, 70 and 130 mm from a reference point, and the amounts of the deformation were compared through experiments. /n the results of the comparison and analysis, the values obtained from these comparison and analysis represent similar tendencies. Also, it is verified that their geometric errors increase with the increase in temperature. In addition, regarding the factors that affect the deformation of a workpiecc, it can be seen that the geometric error in the lathe is about 15%, the error caused by the cutting force is about 10%, and the deformation caused by the heat is about 75%.展开更多
A thermodynamic model of hydrogen induced silicon surface layer splitting with the help of an oxidized silicon wafer bonded is proposed.Wafer splitting is the result of lateral growth of hydrogen blisters in the enti...A thermodynamic model of hydrogen induced silicon surface layer splitting with the help of an oxidized silicon wafer bonded is proposed.Wafer splitting is the result of lateral growth of hydrogen blisters in the entire implanted hydrogen region during annealing.The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion.The hydrogen blister radius was studied as the function of annealing time,annealing temperature and implantation dose.The critical radius was obtained according to the Griffith energy condition.The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters.展开更多
The heat generated and accumulated on the machined surface of an Inconel 718 workpiece causes thermal damage during the cutting process.Surface-active media with high thermal conductivity coated on the workpiece to be...The heat generated and accumulated on the machined surface of an Inconel 718 workpiece causes thermal damage during the cutting process.Surface-active media with high thermal conductivity coated on the workpiece to be machined may have the potential to reduce the generation of cutting heat.In this study,a theoretical model for predicting the instantaneous machined surface temperature field is proposed for surface-active thermal conductive medium(SACM)-assisted cutting based on the finite element and Fourier heat transfer theories.Orthogonal cutting experiments were performed to verify the results predicted using the proposed surface-temperature field model.Three SACMs with various thermal conductivities were used to coat Inconel 718 surface to be machined.Thermocouples embedded into the workpiece were used to measure the cutting temperature at different points on the machined workpiece surface during the cutting process.The experimental results were in agreement with the predicted temperatures,and the maximum error between the experimental results and predicted temperatures was approximately 9.5%.The cutting temperature on the machined surface decreased with an increase in the thermal conductivity of the SACM.The graphene SACM with high thermal conductivity can effectively reduce the temperature from 542℃ to 402℃,which corresponds to a reduction of approximately 26%.The temperature reduction due to SACM decreases with an increase in the distance between the temperature prediction point and machined workpiece surface.In conclusion,the cutting temperatures on the machined workpiece surface can be reduced by coating with SACM.展开更多
Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruct...Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruction.Therefore,a meshless three-dimensional milling simulation model was established for TC4 titanium alloy using the smooth particle hydrodynamics(SPH)method.Firstly,the established SPH model was analyzed by the LS-DYNA software,and the stress distribution,temperature field,and cutting force during milling were studied under specific conditions.Subsequently,the cutting force was simulated under different cutting parameters and the effects of these parameters on the cutting force were determined.Finally,based on a series of cutting force experiments,the accuracy of the simulation model was verified.This study proves the feasibility of SPH method in the simulation of titanium alloy milling process and provides novel methods for investigating the processing mechanism and optimizing the processing technology of titanium alloys.展开更多
The analytical model of residual stress in orthogonal cutting proposed by Jiann is an important tool for residual stress prediction in orthogonal cutting. In application of the model, a problem of low precision of the...The analytical model of residual stress in orthogonal cutting proposed by Jiann is an important tool for residual stress prediction in orthogonal cutting. In application of the model, a problem of low precision of the surface residual stress prediction is found. By theoretical analysis, several shortages of Jiann＇s model are picked out, including： inappropriate boundary conditions, unreason- able calculation method of thermal stress, ignorance of stress constraint and cyclic loading algorithm. These shortages may directly lead to the low precision of the surface residual stress prediction. To eliminate these shortages and make the prediction more accurate, an improved model is proposed. In this model, a new contact boundary condition between tool and workpiece is used to make it in accord with the real cutting process; an improved calculation method of thermal stress is adopted; a stress constraint is added according to the volume- constancy of plastic deformation; and the accumulative effect of the stresses during cyclic loading is considered. At last, an experiment for measuring residual stress in cutting AISI 1045 steel is conducted. Also, Jiann＇s model and the improved model are simulated under the same conditions with cutting experiment. The comparisons show that the surface residual stresses predicted by the improved model is closer to the experimental results than the results predicted by Jiann＇s model.展开更多
文摘A computer aided measurement system is used to measure the cutting temperature directly in high-speed machining by natural thermocouples and standard thermocouples. In this system the tool/workpiece interface temperature is measured by the tool/workpiece natural thermocouple, while the temperature distribution on the workpiece surface and that of interior are measured by some standard thermocouples prearranged at proper positions. The system can be used to measure cutting temperature in the machining with the rotary cutting tools, such as vertical drill and end milling cutter. It is practically used for the research on high-speed milling with hardened steel.
基金supported by National Natural Science Foundation of China(Grant No.50775210)Liaoning Provincial Natural Science Foundation of China(Grant No.20062143)Liaoning Provincial Universities Science and Technology Program of China(Grant No.05L023)
文摘In high-speed cutting, natural thermocouple, artificial thermocouple and infrared radiation temperature measurement are usually adopted for measuring cutting temperature, but these methods have difficulty in measuring transient temperature accurately of cutting area on account of low response speed and limited cutting condition. In this paper, NiCr/NiSi thin-film thermocouples（TFTCs） are fabricated according to temperature characteristic of cutting area in high-speed cutting by means of advanced twinned microwave electro cyclotron resonance（MW-ECR） plasma source enhanced radio frequency（RF） reaction non-balance magnetron sputtering technique, and can be used for transient cutting temperature measurement. The time constants of the TFTCs with different thermo-junction film width are measured at four kinds of sampling frequency by using Ultra-CFR short pulsed laser system that established. One-dimensional unsteady heat conduction model is constructed and the dynamic performance is analyzed theoretically. It can be seen from the analysis results that the NiCr/NiSi TFTCs are suitable for measuring transient temperature which varies quickly, the response speed of TFTCs can be obviously improved by reducing the thickness of thin-film, and the area of thermo-junction has little influence on dynamic response time. The dynamic calibration experiments are made on the constructed dynamic calibration system, and the experimental results confirm that sampling frequency should be larger than 50 kHz in dynamic measurement for stable response time, and the shortest response time is 0.042 ms. Measurement methods and devices of cutting heat and cutting temperature measurement are developed and improved by this research, which provide practical methods and instruments in monitoring cutting heat and cutting temperature for research and production in high-speed machining.
文摘A study was undertaken to investigate the performan ce of PCBN tool in the finish turning GCr15 bearing steel with different hardness between 30～64 HRC. The natural thermocouple was used to measure the cutting tem p erature, tool life and cutting temperature were investigated and compared. The m aterial can be heated by this instrument which using low voltage and high elec trical current, while PCBN can’t be heated by electrifying directly, so the ke ntanium layer coating over the PCBN is heated, so the PCBN is heated and its th ermoelectric property is got by this method. [TPP129,+60mm88mm,Y,PZ#] Fig.1 Effect of cutting depth and workpiec hardness on. the cutting temperatureThe objective was to determine the influence of the workpiece hardness on change s in cutting temperature and tool wear characterize. It can be found from Fig.1 that the cutting temperature show an increasing tendency with the improvement of workpiece hardness within the cutting speed scope when the workpiece hardness i s under HRC50. And on the other hand, it is found that the cutting temperature s how the downtrend with the improvement of workpiece hardness when the workpiece hardness is over HRC50. According to experimental results, the critical hard ness when turning hardened GCr15 bearing steel with PCBN tool is about HRC50. Th e wear causes of PCBN tool have been found out through taking photos on the micr o-shape of PCBN poly-laminate initial surface as well as face and flank of wea r tool and analysis on chemical elements. It is discovered that the PCBN tools a re not suitable for cutting the workpiece at nearly critical hardness, because n ear the critical hardness, PCBN wear at the highest speed. For researching the w ear rule of PCBN tool, the tool wear experiments have been carried on by using b earing steel GCr15 at hardness HRC40 and HRC60 with changing cutting speed. The indexes of tool life equations is gained under two kinds of conditions w hich are bigger than 0.6, so the effects of cutting speed on the PCBN tool are m uch less than that of carbide tool and ceramic tool.
基金National Defense Foundation Pre-Research Science Challenge Project(Grant No.JCKY2016212A506-0107)Development Funds of China Academy of Engineering Physics(Grant No.2015B0203029).
文摘Pure iron is one of the difficult-to-machine materials due to its large chip deformation,adhesion,work-hardening,and built-up edges formation during machining.This leads to a large workpiece deformation and challenge to meet the required technical indicators.Therefore,under varying the grain size of pure iron,the influence of cutting speed,feed,and depth of cut on the cutting force,heat generation,and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material.The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent.However,the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.
文摘A parametric model of cutting temperature generated in end milling process is developed according to the thermal mechanism of end milling as an intermittent operation, which periodically repeats the cycle of heating under cutting and cooling under non-cutting. It shows that cutting speed and the tool-workpiece engagement condition are determinative for tool temperature in the operation. The suggested model was investigated by tests of AlTiN coated endmill machining hardened die steel JIS SKD61, where cutting temperature on the flank face of tool was measured with an optical fiber type radiation thermometer. Experimental results show that the tendency of cutting temperature to increase with cutting speed and engagement angle is intensified with the progressing tool wear.
文摘A thermoelectric curve of GCr15 BN500 is acquired by rapid label way. The study on measuring the cutting temperature with PCBN cutter is done and the calculation formula is achieved. A series of experiments about cutting temperature are made for different hardness tempering bearing steel at the same time. The rule that cutting temperature increases with increasing of the cutting speed, feed, back engagement of the cutting edge is gained. It is known that the cutting temperature is highest under the condition that back engagement of the cutting edge a p≥2.5 mm and the machined material hardness equals to 50HRC.
文摘According to work tool thermocouple principle,the equipment for measuring hobbing temperature is developed.The changing character of cutting temperature in gear hobbing,the relation between cutting conditions and hobbing temperature,and the influence of cutting conditions on hobbing temperature are discussed by means of experiments.All these have provided the reference standards for the equitably selecting cutting conditions and geometrical parameter of hob,prolonging the life of gear hobs,and predicting processes of gear hobbing.
基金the National Natural Science Foundation of China(No.51975123)Fuzhou Science and Technology Plan Project(No.2019G42)。
文摘The ADC12 aluminum alloy is prone to severe tool wear and high cutting heat during high-speed milling because of its high hardness.This study analyzes the highspeed milling process from the perspective of different chip morphologies.The influence of cutting temperature on chip morphology was expounded.A two-dimensional orthogonal cutting model was established for finite element analysis(FEA)of high-speed milling of ADC12 aluminum alloy.A theoretical analysis model of cutting force and cutting temperature was proposed based on metal cutting theory.The variations in chip shape,cutting force,and cutting temperature with cutting speed increasing were analyzed via FEA.The results show that,with the increase in cutting speed,the chip morphology changes from continuous to serrated,and then back to continuous.The serrated chip is weakened and the cutting temperature is lowered when the speed is lower than 600 m·min^(-1)or higher than 1800 m·min^(-1).This study provides a reference for reducing cutting temperature,controlling chip morphology and improving cutting tool life.
文摘Wear of cutting tools is a big concern for industrial manufacturers, because of their acquisition cost as well as the impact on the production lines when they are unavailable. Law of wear is very important in determining cutting tools lifespan, but most of the existing models don’t take into account the cutting temperature. In this work, the theoretical and experimental results of a dynamic study of metal machining against cutting temperature of a treated steel of grade S235JR with a high-speed steel tool are provided. This study is based on the analysis of two complementary approaches, an experimental approach with the measurement of the temperature and on the other hand, an approach using modeling. Based on unifactorial and multifactorial tests (speed of cut, feed, and depth of cut), this study allowed the highlighting of the influence of the cutting temperature on the machining time. To achieve this objective, two specific approaches have been selected. The first was to measure the temperature of the cutting tool and the second was to determine the wear law using Rayleigh-Ham dimensional analysis method. This study permitted the determination of a law that integrates the cutting temperature in the calculations of the lifespan of the tools during machining.
文摘In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA) model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, -10°, 0°, 10°, 20°, and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed) have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM) of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface’s friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.
基金National Natural Science Foundation of China(No.50075021)
文摘The mathematical model on the temperature of the waved-edge is constructedaccording to Jaeger's theory of moving solid and based on the used temperature model of the flatinsert. It is possible to forecast the milling temperature through programming. The comparableexperiments have been done between the two new three-dimension groove inserts (waved-edge insert,great edge insert) and flat fake insert. The theoretic forecast is in good agreement with theexperimental result. According to the cutting conditions, the boundary condition of finite elementanalysis on cutting temperature field is established, and the three-dimensional temperature fieldsof inserts with grooves are analyzed by FEM, so as to offer a reference basis for the design andoptimization of insert grooves.
基金supported by National Natural Science Foundation of China (Grant No. 50775115)
文摘The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6Al-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth（KT） and average flank wear width（VB） firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50% and 55%,respectively.Under the given conditions,the optimum hydrogen content is 0.26%.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.
基金supported by the National Natural Science Foundation of China(No.51475233)
文摘Ti2AlNb intermetallic alloy is a newly developed high-temperature resistant structural material due to its excellent material and mechanical properties,which also make it to be one of the most difficult-to-cut materials.In order to study the machinability of Ti2AlNb alloy,a series of turning experiments of Ti2AlNb alloy with varying cutting speed and feed rate using coated carbide tools are carried out.The results associated with cutting forces,cutting temperature and tool wear are presented and discussed.Moreover,the cutting performance of Ti2AlNb alloy is evaluated in comparison with that of most commonly used Ti6Al4 Vand Inconel 718 alloys in terms of the cutting forces and cutting temperature.The comparison results show that there is a correlation between the machinability and the mechanical properties of work material properties.Additionally,considering material removal rate and tool life,the optimized machining parameters for cutting Ti2AlNb alloys using coated carbide tools are recommended.
基金the National Natural Science Foundation of China(Nos.51705249,51875285)the China Postdoctoral Science Foundation(No.2019M661823)+1 种基金the Aeronautical Science Foundation of China(No.2017ZE52047)the Defense Industrial Technology Development Program(No.JCKY2018605C018)。
文摘Carbon fiber reinforced silicon carbide matrix(Cf/SiC)composites have the most potential application for high-temperature components of aerospace high-end equipment.However,high cutting temperature,rapid tool wear and severe surface damages are the main problems in dry cutting Cf/SiC composites process.The feasibility study on cryogenic milling of Cf/SiC composites using liquid nitrogen as coolant is investigated.Influences of milling parameters and coolant on temperature,cutting force,surface quality and tool wear are investigated,which is compared with dry cutting.Experimental results reveal that the cutting temperature in cryogenic milling of Cf/SiC composites is reduced by about 40%—60%compared with dry cutting.The milling force increases gradually with the increase of spindle speed,feed rate,depth and width of milling in cryogenic milling process.In addition,the machined surface quality in cryogenic milling is superior to that in dry cutting process.Fiber fracture,matrix damage and fiber matrix debonding are main material removal mechanisms.Flank face wear is the main wear form of the polycrystalline diamond(PCD)end mills.The tool life is prolonged in the cryogenic milling process because the reduced temperature inhibits the softening of Co binder and phase transition of diamond in the PCD end mills.
基金supported by the National Natural Science Foundation of China(No.51275227)the Funding of Jiangsu Innovation Program for Graduate Education(No.CXLX11_0175)the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST201326)
文摘The milling machinabilities of titanium matrix composites were comprehensively evaluated to provide a theoretical basis for cutting parameter determination. Polycrystalline diamond （PCD） tools with different grain sizes and geometries, and carbide tools with and without coatings were used in the experiments. Milling forces, milling temperatures, tool lifetimes, tool wear, and machined surface integrities were investigated. The PCD tool required a primary cutting force 15 % smaller than that of the carbide tool, while the uncoated carbide tool required a primary cutting force 10% higher than that of the TiA1N-eoated tool. A cutting force of 300 N per millimeter of the cutting edge （300 N/mm） was measured. This caused excessive tool chipping. The cutting temperature of the PCD tool was 20%-30% lower than that of the carbide tool, while that of the TiA1N-coated tool was 12% lower than that of the uncoated carbide tool. The cutting temperatures produced when using water-based cooling and minimal quantity lubrication （MQL） were reduced by 100 ~C and 200 ~C, compared with those recorded with dry cutting, respectively. In general, the PCD tool lifetimes were 2--3 times longer than the carbide tool lifetimes. The roughness Ra of the machined surface was less than 0.6μm, and the depth of the machined surface hardened layer was in the range of 0.15-0.25 mm for all of the PCD tools before a flank wear land of 0.2 mm was reached. The PCD tool with a 0.8 mm tool nose radius, 0% rake angle, 10% flank angle, and grain size of （30＋2） μm exhibited the best cutting performance. For this specific tool, a lifetime of 16 rain can be expected.
基金Project(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE),Korea
文摘A finite element model was established for analyzing the geometric errors in turning operations and a two-step analyzing process was proposed. In the first analyzing step, the cutting force and the cutting heat for the cutting conditions were obtained using the AdvantEdge. Also, the deformation of a workpiece was estimated in the second step using the ANSYS. The deformation was analyzed for a 150 mm-long workpiece at three different measuring points, such as 10, 70 and 130 mm from a reference point, and the amounts of the deformation were compared through experiments. /n the results of the comparison and analysis, the values obtained from these comparison and analysis represent similar tendencies. Also, it is verified that their geometric errors increase with the increase in temperature. In addition, regarding the factors that affect the deformation of a workpiecc, it can be seen that the geometric error in the lathe is about 15%, the error caused by the cutting force is about 10%, and the deformation caused by the heat is about 75%.
文摘A thermodynamic model of hydrogen induced silicon surface layer splitting with the help of an oxidized silicon wafer bonded is proposed.Wafer splitting is the result of lateral growth of hydrogen blisters in the entire implanted hydrogen region during annealing.The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion.The hydrogen blister radius was studied as the function of annealing time,annealing temperature and implantation dose.The critical radius was obtained according to the Griffith energy condition.The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters.
基金the financial support from the National Key Research and Development Program of China(Grant No.2019YFB2005401)supported by grants from the National Natural Science Foundation of China(Grant No.91860207)Taishan Scholar Foundation.
文摘The heat generated and accumulated on the machined surface of an Inconel 718 workpiece causes thermal damage during the cutting process.Surface-active media with high thermal conductivity coated on the workpiece to be machined may have the potential to reduce the generation of cutting heat.In this study,a theoretical model for predicting the instantaneous machined surface temperature field is proposed for surface-active thermal conductive medium(SACM)-assisted cutting based on the finite element and Fourier heat transfer theories.Orthogonal cutting experiments were performed to verify the results predicted using the proposed surface-temperature field model.Three SACMs with various thermal conductivities were used to coat Inconel 718 surface to be machined.Thermocouples embedded into the workpiece were used to measure the cutting temperature at different points on the machined workpiece surface during the cutting process.The experimental results were in agreement with the predicted temperatures,and the maximum error between the experimental results and predicted temperatures was approximately 9.5%.The cutting temperature on the machined surface decreased with an increase in the thermal conductivity of the SACM.The graphene SACM with high thermal conductivity can effectively reduce the temperature from 542℃ to 402℃,which corresponds to a reduction of approximately 26%.The temperature reduction due to SACM decreases with an increase in the distance between the temperature prediction point and machined workpiece surface.In conclusion,the cutting temperatures on the machined workpiece surface can be reduced by coating with SACM.
文摘Milling is one of the main methods for processing titanium alloy.At present,the complex process of milling is usually simulated by finite element method,which often has problems in mesh distortion and mesh reconstruction.Therefore,a meshless three-dimensional milling simulation model was established for TC4 titanium alloy using the smooth particle hydrodynamics(SPH)method.Firstly,the established SPH model was analyzed by the LS-DYNA software,and the stress distribution,temperature field,and cutting force during milling were studied under specific conditions.Subsequently,the cutting force was simulated under different cutting parameters and the effects of these parameters on the cutting force were determined.Finally,based on a series of cutting force experiments,the accuracy of the simulation model was verified.This study proves the feasibility of SPH method in the simulation of titanium alloy milling process and provides novel methods for investigating the processing mechanism and optimizing the processing technology of titanium alloys.
文摘The analytical model of residual stress in orthogonal cutting proposed by Jiann is an important tool for residual stress prediction in orthogonal cutting. In application of the model, a problem of low precision of the surface residual stress prediction is found. By theoretical analysis, several shortages of Jiann＇s model are picked out, including： inappropriate boundary conditions, unreason- able calculation method of thermal stress, ignorance of stress constraint and cyclic loading algorithm. These shortages may directly lead to the low precision of the surface residual stress prediction. To eliminate these shortages and make the prediction more accurate, an improved model is proposed. In this model, a new contact boundary condition between tool and workpiece is used to make it in accord with the real cutting process; an improved calculation method of thermal stress is adopted; a stress constraint is added according to the volume- constancy of plastic deformation; and the accumulative effect of the stresses during cyclic loading is considered. At last, an experiment for measuring residual stress in cutting AISI 1045 steel is conducted. Also, Jiann＇s model and the improved model are simulated under the same conditions with cutting experiment. The comparisons show that the surface residual stresses predicted by the improved model is closer to the experimental results than the results predicted by Jiann＇s model.
