To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’...To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’along the spiral trajectory,was proposed.From the kinematics analysis,it is found that the machining quality of micro-dimpled structures is highly dependent on the machining trajectory using spiral trajectory tool reciprocating motion.To reveal this causation,simulation modelling and experimental studies were carried out.A simulation model was developed to quantitatively and qualitatively investigate the influence of the trajectory discretization strategies(constant-angle and constant-arc length)and parameters(discrete angle,discrete arc length,and pitch)on surface texture and residual height of micro-dimpled structures.Subsequently,micro-dimpled structures were milled under different trajectory discretization strategies and parameters with spiral trajectory tool reciprocating motion.A comprehensive comparison between the milled results and simulation analysis was made based on geometry accuracy,surface morphology and surface roughness of milled dimples.Meanwhile,the errors and factors affecting the above three aspects were analyzed.The results demonstrate both the feasibility of the established simulation model and the machining capability of this machining way in milling high-quality micro-dimpled structures.Spiral trajectory tool reciprocating motion provides a new machining way for milling micro-dimpled structures and micro-dimpled functional surfaces.And an appropriate machining trajectory can be generated based on the optimized trajectory parameters,thus contributing to the improvement of machining quality and efficiency.展开更多
Atomic-level manufacturing,as the "keystone" of future technology,marks the transformative shift from the micro/nano era based on "classical theory" to the atomic era grounded in "quantum theo...Atomic-level manufacturing,as the "keystone" of future technology,marks the transformative shift from the micro/nano era based on "classical theory" to the atomic era grounded in "quantum theory".It enables the precise control of matter arrangement and composition at the atomic scale,thereby achieving large-scale production of atomically precise and structured products.Electrochemical deposition(ECD),a typical "atom addition" fabrication method for electrochemical atomic and close-to-atomic scale manufacturing(EC-ACSM),enables precise control over material properties at the atomic scale,allowing breakthroughs in revolutionary performance of semiconductors,quantum computing,new materials,nanomedicine,etc.This review explores the fundamentals of EC-ACSM,particularly at the electrode/electrolyte interface,and investigates maskless ECD techniques,highlighting their advantages,limitations,and the role of in situ monitoring and advanced simulations in the process optimization.However,atomic electrochemical deposition faces significant challenges in precise control over atom-ion interactions,electrode-electrolyte interfacial dynamics,and surface defects.In the future,overcoming these obstacles is critical to advancing EC-ACSM and unlocking its full potential in scalability for industrial applications.EC-ACSM can drive the highly customized design of materials and offer strong technological support for the development of future science,ushering in a new atomic era of material innovation and device manufacturing.展开更多
Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topogra...Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topography at micro-and nanoscales. In this research, periodic micro-and nanostructures were patterned on several polymer surfaces by ultra-precision single point diamond turning to investigate the relationships between surface topographies at the micro-and nanoscales and their surface wettability. This research revealed that single-point diamond turning could be used to enhance the wettability of a variety of polymers, including polyvinyl chloride(PVC), polyethylene 1000(PE1000), polypropylene copolymer(PP) and polytetrafluoroethylene(PFTE), which cannot be processed by conventional semiconductor-based manufacturing processes. Materials exhibiting common wettability properties(θ≈ 90°) changed to exhibit "superhydrophobic" behavior(θ > 150°). Compared with the size of the structures, the aspect ratio of the void space between micro-and nanostructures has a strong impact on surface wettability.展开更多
Grinding is one of the most widely used material removal methods at the end of many process chains.Grinding force is related to almost all grinding parameters,which has a great influence on material removal rate,dimen...Grinding is one of the most widely used material removal methods at the end of many process chains.Grinding force is related to almost all grinding parameters,which has a great influence on material removal rate,dimensional and shape accuracy,surface and subsurface integrity,thermodynamics,dynamics,wheel durability,and machining system deformation.Considering that grinding force is related to almost all grinding parameters,grinding force can be used to detect grinding wheel wear,energy calculation,chatter suppression,force control and grinding process simulation.Accurate prediction of grinding forces is important for optimizing grinding parameters and the structure of grinding machines and fixtures.Although there are substantial research papers on grinding mechanics,a comprehensive review on the modeling of grinding mechanics is still absent from the literature.To fill this gap,this work reviews and introduces theoretical methods and applications of mechanics in grinding from the aspects of modeling principles,limitations and possible future trendencies.展开更多
The application of mixed powders with different mass fraction on laser additive repairing(LAR)can be an effective way to guarantee the performance and functionality of repaired part in time.A convenient and feasible a...The application of mixed powders with different mass fraction on laser additive repairing(LAR)can be an effective way to guarantee the performance and functionality of repaired part in time.A convenient and feasible approach is presented to repair TA15 forgings by employing Ti6Al4V-xTA15 mixed powders in this paper.The performance compatibility of Ti6Al4V-xTA15 powders from the aspects of microhardness,tensile property,heat capacity,thermal expansion coefficient and corrosion resistance with the TA15 forgings was fully investigated.The primaryαlaths were refined and the volume fraction of the secondaryαphase was increased by increasing the mass fraction of TA15 in the mixed Ti6Al4V-xTA15 powders,leading to varied performances.In conclusion,the mixed Ti6Al4V-70%TA15(x=70%)powders is the most suitable candidate and is recommended as the raw material for LAR of TA15 forgings based on overall consideration of the compatibility calculations of the laser repaired zone with the wrought substrate zone.展开更多
Atomic and close-to-atomic scale manufacturing(ACSM)represents techniques for manufacturing high-end products in various fields,including future-generation computing,communication,energy,and medical devices and materi...Atomic and close-to-atomic scale manufacturing(ACSM)represents techniques for manufacturing high-end products in various fields,including future-generation computing,communication,energy,and medical devices and materials.In this paper,the theoretical boundary between ACSM and classical manufacturing is identified after a thorough discussion of quantum mechanics and their effects on manufacturing.The physical origins of atomic interactions and energy beams-matter interactions are revealed from the point view of quantum mechanics.The mechanisms that dominate several key ACSM processes are introduced,and a current numerical study on these processes is reviewed.A comparison of current ACSM processes is performed in terms of dominant interactions,representative processes,resolution and modelling methods.Future fundamental research is proposed for establishing new approaches for modelling ACSM,material selection or preparation and control of manufacturing tools and environments.This paper is by no means comprehensive but provides a starting point for further systematic investigation of ACSM fundamentals to support and accelerate its industrial scale implementation in the near future.展开更多
Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess free...Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess freeform(i.e.,non-rotational symmetric)surfaces.The toolpath,composed of high density of short linear and circular segments,is generally used in computer numerical control(CNC)systems to machine those products.However,the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration,which will decrease the machining efficiency and product surface finish.Driven by the ever-increasing need for high-speed high-precision machining of those products,many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry,aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods.This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications.The advantages and disadvantages of these approaches are discussed.Possible future research directions are also offered.展开更多
This paper reports the performance enhancement benefits in diamond turning of the silicon wafer by incorporation of the surface defect machining(SDM)method.The hybrid micromachining methods usually require additional ...This paper reports the performance enhancement benefits in diamond turning of the silicon wafer by incorporation of the surface defect machining(SDM)method.The hybrid micromachining methods usually require additional hardware to leverage the added advantage of hybrid technologies such as laser heating,cryogenic cooling,electric pulse or ultrasonic elliptical vibration.The SDM method tested in this paper does not require any such additional baggage and is easy to implement in a sequential micro-machining mode.This paper made use of Raman spectroscopy data,average surface roughness data and imaging data of the cutting chips of silicon for drawing a comparison between conventional single-point diamond turning(SPDT)and SDM while incorporating surface defects in the(i)circumferential and(ii)radial directions.Complementary 3D finite element analysis(FEA)was performed to analyse the cutting forces and the evolution of residual stress on the machined wafer.It was found that the surface defects generated in the circumferential direction with an interspacing of 1 mm revealed the lowest average surface roughness(Ra)of 3.2 nm as opposed to 8 nm Ra obtained through conventional SPDT using the same cutting parameters.The observation of the Raman spectroscopy performed on the cutting chips showed remnants of phase transformation during the micromachining process in all cases.FEA was used to extract quantifiable information about the residual stress as well as the sub-surface integrity and it was discovered that the grooves made in the circumferential direction gave the best machining performance.The information being reported here is expected to provide an avalanche of opportunities in the SPDT area for low-cost machining solution for a range of other nominal hard,brittle materials such as SiC,ZnSe and GaAs as well as hard steels.展开更多
Purpose Whilst modifications in thermoregulatory responses and plasma volume during heat acclimation(HA)are well researched,much less is known regarding hemoglobin mass.The aim of this study was to investigate the hem...Purpose Whilst modifications in thermoregulatory responses and plasma volume during heat acclimation(HA)are well researched,much less is known regarding hemoglobin mass.The aim of this study was to investigate the hematological adaptations associated with a long-term,progressive,work-matched controlled heart rate HA protocol.Methods Ten males(VO_(2peak):4.50±0.50 L/min)completed two three-week training interventions consisting of HA(36℃ and 59%RH)and exercise in temperate conditions(TEMP:18℃ and 60%RH)in a counter-balanced crossover design.Weekly training included 5 consecutive laboratory-based sessions(i.e.4 controlled heart rate training and 1 repeated sprint training)and 2 days off.Results Hemoglobin mass decreased from day 4 of training in HA(-22[-37,-8]g,P<0.001)but not TEMP(+2[-12,+17]g,P=0.743),returning to baseline at the end of HA(-7[-22,+7]g,P=0.333).As compared to day 1,several other adaptations were present from day 5 onward in HA including a decrease in heart rate at rest(-4[-8,-0]beats/min,P=0.040)and at a given work rate(-6[-10,-1]beats/min,P=0.012),an increase in whole-body sweat rate(+0.3[+0.1,+0.5]L/h,P=0.015),and an increase in power output(+18[+8,+28]W,P<0.001);while there was no changes in TEMP(P≥0.143).Plasma volume increased in both HA(+168[+23,+314]mL)and TEMP(+166[+20,+311]mL)by the 11th day of training(P≤0.027).Conclusion While training in both hot or temperate conditions led to plasma volume increases,training in the heat lead to specific physiological adaptations,including a transient decrease in hemoglobin mass that was rapidly reversed within a few days of HA.展开更多
Purpose The aim of this study was to confirm the impact of heat acclimation on aerobic performance in hot conditions and elucidate the transfer of heat adaptations to cool and hypoxic environments.Methods Ten males(VO...Purpose The aim of this study was to confirm the impact of heat acclimation on aerobic performance in hot conditions and elucidate the transfer of heat adaptations to cool and hypoxic environments.Methods Ten males(VO_(2peak):4.50±0.50 L/min)completed two three-week interventions consisting of heat acclimation(HA:36℃ and 59%RH)and temperate training(TEMP:18℃ and 60%RH)in a counter-balanced crossover design.Train-ing weeks consisted of four work-matched controlled heart rate sessions interspersed with one intermittent sprint session,and two rest days.Before and after the interventionsVO_(2peak) and 20-min time trial performance were evaluated in COOL(18℃),HOT(35℃)and hypoxic(HYP:18℃ andFiO_(2):15.4%)conditions.Results Following HA,VO_(2peak) increased significantly in HOT(0.24 L/min[0.01,0.47],P=0.040)but not COOL(P=0.431)or HYP(P=0.411),whereas TEMP had no influence onVO_(2peak)(P≥0.424).Mean time trial power output increased sig-nificantly in HOT(20 W[11,28],P<0.001)and COOL(12 W[4,21],P=0.004),but not HYP(7 W[-1,16],P=0.075)after HA,whereas TEMP had no influence on mean power output(P≥0.110).Rectal(-0.13℃[-0.23,-0.03],P=0.009)and skin(-0.7℃[-1.2,-0.3],P<0.001)temperature were lower during the time trial in HOT after HA,whereas mean heart rate did not differ(P=0.339).Conclusions HA improved aerobic performance in HOT in conjunction with lower thermal strain and enhanced cardiovas-cular stability(similar heart rate for higher workload),whereas the mechanistic pathways improving performance in COOL and HYP remain unclear.展开更多
In this paper,molecular dynamic(MD)simulation was adopted to study the ductile response of single-crystal GaAs during single-point diamond turning(SPDT).The variations of cutting temperature,coordination number,and cu...In this paper,molecular dynamic(MD)simulation was adopted to study the ductile response of single-crystal GaAs during single-point diamond turning(SPDT).The variations of cutting temperature,coordination number,and cutting forces were revealed through MD simulations.SPDT experiment was also carried out to qualitatively validate MD simulation model from the aspects of normal cutting force.The simulation results show that the fundamental reason for ductile response of GaAs during SPDT is phase transition from a perfect zinc blende structure(GaAs-I)to a rock-salt structure(GaAs-II)under high pressure.Finally,a strong anisotropic machinability of GaAs was also found through MD simulations.展开更多
Adhesion is a common phenomenon in nanomachining which affects processing accuracy and repeatability.As material removal approaches the atomic or close-to-atomic scale,quantum mechanics becomes the dominant principle ...Adhesion is a common phenomenon in nanomachining which affects processing accuracy and repeatability.As material removal approaches the atomic or close-to-atomic scale,quantum mechanics becomes the dominant principle behind the atomic-level interaction.However,atomic-scale effects cannot be properly described by empirical potential function-based molecular dynamics simulations.This study uses a first-principles method to reveal the atomic-scale adhesion between a diamond tip and a copper slab during initial-stage nanoindentation.Using a simplified tip and slab model,adhesion energy,electronic distribution,and density of states are analyzed based on quantum chemistry calculation.Results show that atomic adhesion is primarily due to the covalent bonding interaction between C and Cu atoms,which can induce structural changes to the diamond tip and copper slab.The effects of tip position and angles on adhesion are further studied through a series of simulations.The results show that adhesion between the tip and slab is sensitive to the lattice structure and a variant in angstroms is enough to cause different adhesion and structural changes.The actual determinants of adhesion can only be the atomic and electronic structures at the tip-slab interface.Bond rotation and breakage are observed during simulation and their effects on adhesion are further discussed.To conclude,the first-principles method is important for the analysis of an atomic-scale interaction system,even if only as an aid to describing adhesion at atomic and electronic scales.展开更多
基金co-supported the National Natural Science Foundation of China(No.52235010)the Heilongjiang Postdoctoral Fund(No.LBH-Z22136)the New Era Longjiang Excellent Master and Doctoral Dissertation Fund(No.LJYXL2022-057).
文摘To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’along the spiral trajectory,was proposed.From the kinematics analysis,it is found that the machining quality of micro-dimpled structures is highly dependent on the machining trajectory using spiral trajectory tool reciprocating motion.To reveal this causation,simulation modelling and experimental studies were carried out.A simulation model was developed to quantitatively and qualitatively investigate the influence of the trajectory discretization strategies(constant-angle and constant-arc length)and parameters(discrete angle,discrete arc length,and pitch)on surface texture and residual height of micro-dimpled structures.Subsequently,micro-dimpled structures were milled under different trajectory discretization strategies and parameters with spiral trajectory tool reciprocating motion.A comprehensive comparison between the milled results and simulation analysis was made based on geometry accuracy,surface morphology and surface roughness of milled dimples.Meanwhile,the errors and factors affecting the above three aspects were analyzed.The results demonstrate both the feasibility of the established simulation model and the machining capability of this machining way in milling high-quality micro-dimpled structures.Spiral trajectory tool reciprocating motion provides a new machining way for milling micro-dimpled structures and micro-dimpled functional surfaces.And an appropriate machining trajectory can be generated based on the optimized trajectory parameters,thus contributing to the improvement of machining quality and efficiency.
基金the support from the National Natural Science Foundation of China (Grant Nos. 52405447 and 52275299)the National Key Research and Development Program of China (Grant No. 2021YFB1716200)the Key Research and Development Program of Jiangxi Province in China (Grant No. 20232BBE50011)。
文摘Atomic-level manufacturing,as the "keystone" of future technology,marks the transformative shift from the micro/nano era based on "classical theory" to the atomic era grounded in "quantum theory".It enables the precise control of matter arrangement and composition at the atomic scale,thereby achieving large-scale production of atomically precise and structured products.Electrochemical deposition(ECD),a typical "atom addition" fabrication method for electrochemical atomic and close-to-atomic scale manufacturing(EC-ACSM),enables precise control over material properties at the atomic scale,allowing breakthroughs in revolutionary performance of semiconductors,quantum computing,new materials,nanomedicine,etc.This review explores the fundamentals of EC-ACSM,particularly at the electrode/electrolyte interface,and investigates maskless ECD techniques,highlighting their advantages,limitations,and the role of in situ monitoring and advanced simulations in the process optimization.However,atomic electrochemical deposition faces significant challenges in precise control over atom-ion interactions,electrode-electrolyte interfacial dynamics,and surface defects.In the future,overcoming these obstacles is critical to advancing EC-ACSM and unlocking its full potential in scalability for industrial applications.EC-ACSM can drive the highly customized design of materials and offer strong technological support for the development of future science,ushering in a new atomic era of material innovation and device manufacturing.
基金The National Natural Science of China(General Program)(51575083)Major Research Projects of the National Natural Science Foundation of China(91323302)+1 种基金Science Fund for Creative Research Groups(51621064)the EPSRC(EP/K018345/1)and Royal Society-NSFC International Exchange Programme(IE141422)。
基金financial support from Heriot-Watt University (Edinburgh)the Engineering and Physical Sciences Research Council (EP/K018345/1) for this study
文摘Studies on surface wettability have received tremendous interest due to their potential applications in research and industrial processes. One of the strategies to tune surface wettability is modifying surface topography at micro-and nanoscales. In this research, periodic micro-and nanostructures were patterned on several polymer surfaces by ultra-precision single point diamond turning to investigate the relationships between surface topographies at the micro-and nanoscales and their surface wettability. This research revealed that single-point diamond turning could be used to enhance the wettability of a variety of polymers, including polyvinyl chloride(PVC), polyethylene 1000(PE1000), polypropylene copolymer(PP) and polytetrafluoroethylene(PFTE), which cannot be processed by conventional semiconductor-based manufacturing processes. Materials exhibiting common wettability properties(θ≈ 90°) changed to exhibit "superhydrophobic" behavior(θ > 150°). Compared with the size of the structures, the aspect ratio of the void space between micro-and nanostructures has a strong impact on surface wettability.
基金co-supported by the Enterprise Innovation and Development Joint Program of the National Natural Science Foundation of China (No. U20B2032)National Natural Science Foundation of China (No. 51875135)
文摘Grinding is one of the most widely used material removal methods at the end of many process chains.Grinding force is related to almost all grinding parameters,which has a great influence on material removal rate,dimensional and shape accuracy,surface and subsurface integrity,thermodynamics,dynamics,wheel durability,and machining system deformation.Considering that grinding force is related to almost all grinding parameters,grinding force can be used to detect grinding wheel wear,energy calculation,chatter suppression,force control and grinding process simulation.Accurate prediction of grinding forces is important for optimizing grinding parameters and the structure of grinding machines and fixtures.Although there are substantial research papers on grinding mechanics,a comprehensive review on the modeling of grinding mechanics is still absent from the literature.To fill this gap,this work reviews and introduces theoretical methods and applications of mechanics in grinding from the aspects of modeling principles,limitations and possible future trendencies.
基金Project(2019-00899-1-1)supported by the Ministry of Industry and Information Technology of ChinaProject(2021JM-060)supported by the Natural Science Foundation of Shaanxi Province,ChinaProject(3102019QD0409)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The application of mixed powders with different mass fraction on laser additive repairing(LAR)can be an effective way to guarantee the performance and functionality of repaired part in time.A convenient and feasible approach is presented to repair TA15 forgings by employing Ti6Al4V-xTA15 mixed powders in this paper.The performance compatibility of Ti6Al4V-xTA15 powders from the aspects of microhardness,tensile property,heat capacity,thermal expansion coefficient and corrosion resistance with the TA15 forgings was fully investigated.The primaryαlaths were refined and the volume fraction of the secondaryαphase was increased by increasing the mass fraction of TA15 in the mixed Ti6Al4V-xTA15 powders,leading to varied performances.In conclusion,the mixed Ti6Al4V-70%TA15(x=70%)powders is the most suitable candidate and is recommended as the raw material for LAR of TA15 forgings based on overall consideration of the compatibility calculations of the laser repaired zone with the wrought substrate zone.
基金EPSRC(EP/K018345/1,EP/T024844/1,EP/V055208/1)the National Natural Science Foundation of China(NSFC No.52035009)the Royal Society-NSFC international exchange programme(IECNSFC181474)to provide financial support to this research。
文摘Atomic and close-to-atomic scale manufacturing(ACSM)represents techniques for manufacturing high-end products in various fields,including future-generation computing,communication,energy,and medical devices and materials.In this paper,the theoretical boundary between ACSM and classical manufacturing is identified after a thorough discussion of quantum mechanics and their effects on manufacturing.The physical origins of atomic interactions and energy beams-matter interactions are revealed from the point view of quantum mechanics.The mechanisms that dominate several key ACSM processes are introduced,and a current numerical study on these processes is reviewed.A comparison of current ACSM processes is performed in terms of dominant interactions,representative processes,resolution and modelling methods.Future fundamental research is proposed for establishing new approaches for modelling ACSM,material selection or preparation and control of manufacturing tools and environments.This paper is by no means comprehensive but provides a starting point for further systematic investigation of ACSM fundamentals to support and accelerate its industrial scale implementation in the near future.
基金the support from the UK Engineering and Physical Sciences Research Council (EPSRC) under the program (No. EP/K018345/1)the International Cooperation Program of China (No. 2015DFA70630)
文摘Driven by the ever increasing demand in function integration,more and more next generation high value-added products,such as head-up displays,solar concentrators and intra-ocular-lens,etc.,are designed to possess freeform(i.e.,non-rotational symmetric)surfaces.The toolpath,composed of high density of short linear and circular segments,is generally used in computer numerical control(CNC)systems to machine those products.However,the discontinuity between toolpath segments leads to high-frequency fluctuation of feedrate and acceleration,which will decrease the machining efficiency and product surface finish.Driven by the ever-increasing need for high-speed high-precision machining of those products,many novel toolpath interpolation and smoothing approaches have been proposed in both academia and industry,aiming to alleviate the issues caused by the conventional toolpath representation and interpolation methods.This paper provides a comprehensive review of the state-of-the-art toolpath interpolation and smoothing approaches with systematic classifications.The advantages and disadvantages of these approaches are discussed.Possible future research directions are also offered.
基金financial support provided by CSIR,India through the project grant MLP0056the financial support provided by the UKRI via Grants Nos.EP/L016567/1,EP/S013652/1,EP/S036180/1,EP/T001100/1 and EP/T024607/1+2 种基金Royal Academy of Engineering via Grants Nos.IAPP18-19\295,TSP1332 and EXPP2021\1\277,EURAMET EMPIR A185(2018)H2020 EU Cost Actions(CA15102,CA18125,CA18224 and CA16235)Newton Fellowship award from the Royal Society(NIF\R1\191571)。
文摘This paper reports the performance enhancement benefits in diamond turning of the silicon wafer by incorporation of the surface defect machining(SDM)method.The hybrid micromachining methods usually require additional hardware to leverage the added advantage of hybrid technologies such as laser heating,cryogenic cooling,electric pulse or ultrasonic elliptical vibration.The SDM method tested in this paper does not require any such additional baggage and is easy to implement in a sequential micro-machining mode.This paper made use of Raman spectroscopy data,average surface roughness data and imaging data of the cutting chips of silicon for drawing a comparison between conventional single-point diamond turning(SPDT)and SDM while incorporating surface defects in the(i)circumferential and(ii)radial directions.Complementary 3D finite element analysis(FEA)was performed to analyse the cutting forces and the evolution of residual stress on the machined wafer.It was found that the surface defects generated in the circumferential direction with an interspacing of 1 mm revealed the lowest average surface roughness(Ra)of 3.2 nm as opposed to 8 nm Ra obtained through conventional SPDT using the same cutting parameters.The observation of the Raman spectroscopy performed on the cutting chips showed remnants of phase transformation during the micromachining process in all cases.FEA was used to extract quantifiable information about the residual stress as well as the sub-surface integrity and it was discovered that the grooves made in the circumferential direction gave the best machining performance.The information being reported here is expected to provide an avalanche of opportunities in the SPDT area for low-cost machining solution for a range of other nominal hard,brittle materials such as SiC,ZnSe and GaAs as well as hard steels.
文摘Purpose Whilst modifications in thermoregulatory responses and plasma volume during heat acclimation(HA)are well researched,much less is known regarding hemoglobin mass.The aim of this study was to investigate the hematological adaptations associated with a long-term,progressive,work-matched controlled heart rate HA protocol.Methods Ten males(VO_(2peak):4.50±0.50 L/min)completed two three-week training interventions consisting of HA(36℃ and 59%RH)and exercise in temperate conditions(TEMP:18℃ and 60%RH)in a counter-balanced crossover design.Weekly training included 5 consecutive laboratory-based sessions(i.e.4 controlled heart rate training and 1 repeated sprint training)and 2 days off.Results Hemoglobin mass decreased from day 4 of training in HA(-22[-37,-8]g,P<0.001)but not TEMP(+2[-12,+17]g,P=0.743),returning to baseline at the end of HA(-7[-22,+7]g,P=0.333).As compared to day 1,several other adaptations were present from day 5 onward in HA including a decrease in heart rate at rest(-4[-8,-0]beats/min,P=0.040)and at a given work rate(-6[-10,-1]beats/min,P=0.012),an increase in whole-body sweat rate(+0.3[+0.1,+0.5]L/h,P=0.015),and an increase in power output(+18[+8,+28]W,P<0.001);while there was no changes in TEMP(P≥0.143).Plasma volume increased in both HA(+168[+23,+314]mL)and TEMP(+166[+20,+311]mL)by the 11th day of training(P≤0.027).Conclusion While training in both hot or temperate conditions led to plasma volume increases,training in the heat lead to specific physiological adaptations,including a transient decrease in hemoglobin mass that was rapidly reversed within a few days of HA.
文摘Purpose The aim of this study was to confirm the impact of heat acclimation on aerobic performance in hot conditions and elucidate the transfer of heat adaptations to cool and hypoxic environments.Methods Ten males(VO_(2peak):4.50±0.50 L/min)completed two three-week interventions consisting of heat acclimation(HA:36℃ and 59%RH)and temperate training(TEMP:18℃ and 60%RH)in a counter-balanced crossover design.Train-ing weeks consisted of four work-matched controlled heart rate sessions interspersed with one intermittent sprint session,and two rest days.Before and after the interventionsVO_(2peak) and 20-min time trial performance were evaluated in COOL(18℃),HOT(35℃)and hypoxic(HYP:18℃ andFiO_(2):15.4%)conditions.Results Following HA,VO_(2peak) increased significantly in HOT(0.24 L/min[0.01,0.47],P=0.040)but not COOL(P=0.431)or HYP(P=0.411),whereas TEMP had no influence onVO_(2peak)(P≥0.424).Mean time trial power output increased sig-nificantly in HOT(20 W[11,28],P<0.001)and COOL(12 W[4,21],P=0.004),but not HYP(7 W[-1,16],P=0.075)after HA,whereas TEMP had no influence on mean power output(P≥0.110).Rectal(-0.13℃[-0.23,-0.03],P=0.009)and skin(-0.7℃[-1.2,-0.3],P<0.001)temperature were lower during the time trial in HOT after HA,whereas mean heart rate did not differ(P=0.339).Conclusions HA improved aerobic performance in HOT in conjunction with lower thermal strain and enhanced cardiovas-cular stability(similar heart rate for higher workload),whereas the mechanistic pathways improving performance in COOL and HYP remain unclear.
基金The authors would like to thank EPSRC(EP/K018345/1 and EP/T024844/1)the Royal Society-NSFC international exchange programme(IEC\NSFC\181474)for providing financial support for this researchThe authors also acknowledge the use of the EPSRC(EP/K000586/1)funded ARCHIE-WeSt High-Performance Computer at the University of Strathclyde for the MD simulation study.
文摘In this paper,molecular dynamic(MD)simulation was adopted to study the ductile response of single-crystal GaAs during single-point diamond turning(SPDT).The variations of cutting temperature,coordination number,and cutting forces were revealed through MD simulations.SPDT experiment was also carried out to qualitatively validate MD simulation model from the aspects of normal cutting force.The simulation results show that the fundamental reason for ductile response of GaAs during SPDT is phase transition from a perfect zinc blende structure(GaAs-I)to a rock-salt structure(GaAs-II)under high pressure.Finally,a strong anisotropic machinability of GaAs was also found through MD simulations.
基金EPSRC(EP/K018345/1,EPT0248441.EP/V055208/1)the Royal Society-NSFC international exchange programme(IECINSFCU181474)Science and Technology Based for Equipment Design and Manufacruring for Introduction Talents of Diseipline to Universities 2.0 of the 111 pro-ject(Project No.BP0719002)。
文摘Adhesion is a common phenomenon in nanomachining which affects processing accuracy and repeatability.As material removal approaches the atomic or close-to-atomic scale,quantum mechanics becomes the dominant principle behind the atomic-level interaction.However,atomic-scale effects cannot be properly described by empirical potential function-based molecular dynamics simulations.This study uses a first-principles method to reveal the atomic-scale adhesion between a diamond tip and a copper slab during initial-stage nanoindentation.Using a simplified tip and slab model,adhesion energy,electronic distribution,and density of states are analyzed based on quantum chemistry calculation.Results show that atomic adhesion is primarily due to the covalent bonding interaction between C and Cu atoms,which can induce structural changes to the diamond tip and copper slab.The effects of tip position and angles on adhesion are further studied through a series of simulations.The results show that adhesion between the tip and slab is sensitive to the lattice structure and a variant in angstroms is enough to cause different adhesion and structural changes.The actual determinants of adhesion can only be the atomic and electronic structures at the tip-slab interface.Bond rotation and breakage are observed during simulation and their effects on adhesion are further discussed.To conclude,the first-principles method is important for the analysis of an atomic-scale interaction system,even if only as an aid to describing adhesion at atomic and electronic scales.
