Machining high-performance engineering materials,faces challenges including low machining efficiency,poor workpiece surface integrity,and rapid tool wear,which restrict high quality and efficient machining.Ultra-high-...Machining high-performance engineering materials,faces challenges including low machining efficiency,poor workpiece surface integrity,and rapid tool wear,which restrict high quality and efficient machining.Ultra-high-speed machining(UHSM)has been expected to address these issues.However,the material removal mechanisms involved in UHSM remain unclear and need further exploration.This paper reviews the criteria for evaluating the ductile and brittle behaviors of high-performance materials subjected to machining,as well as the developmental history of the material’s ductile-brittle transition induced by machining,proposing the concept of relativization of ductile-brittle property.Additionally,it further summarizes three typical material removal mechanisms:ductile-mode removal based on shear stress,brittle-mode removal based on tensile stress,and extrusion removal based on compressive stress,clarifying the universality of the brittle-mode removal.On this basis,this paper focuses on the discussion of the material removal mechanisms in UHSM,including high strain-rate-induced material embrittlement,UHSM-induced skin effect of damage,and the thermal effect in UHSM.Furthermore,it provides a detailed description of the typical characteristics of chip morphology in the ductile-brittle transition region(DBTR)under the high strain rate condition and,for the first time,elucidates the material removal mechanisms in the DBTR from a microstructural dislocation perspective,enriching the basic theory of UHSM.In the discussion section,it standardizes the definition for the UHSM,and explores the dislocation movement at high strain rates and the crack propagation in the UHSM.Finally,based on the current status of the UHSM technology,it summarizes the relevant research hotspots.For the first time,this paper brings up the brittle-mode removal mechanism under ultra-high-speed conditions,which is helpful to promote the UHSM for industrial applications.展开更多
The Ti6Al4V parts produced by the existing selective laser melting(SLM)are mainly confronted with poor surface finish and inevitable interior defects,which substantially deteriorates the mechanical properties and perf...The Ti6Al4V parts produced by the existing selective laser melting(SLM)are mainly confronted with poor surface finish and inevitable interior defects,which substantially deteriorates the mechanical properties and performances of the parts.In this regard,ultrasonically-assisted machining(UAM)technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force.However,most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions,whereas few of them on the impact of ultrasonic vibration along the vertical direction.In this study,the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling(UAVM)of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining(CM)method.The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style.The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter.Moreover,the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter.As feed rate increased,surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation,while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter.Therefore,the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM.In general,the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.展开更多
Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may ca...Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the workpiece.In this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel.The relationship between grinding speed,SQ and subsurface damage(SSD)was well studied.With increasing grinding speed,surface roughness decreased,and SQ was greatly improved.Meanwhile,the microhardness of the grinding surface declined as the grinding speed increased.The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding speeds.It was attributed to the mechanical-thermal synergistic effect in the grinding process.The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy.The conclusion in the work may also provide insight into processing other hard-to-machining materials.展开更多
基金supported by the Shenzhen Science and Technology Innovation Commission(KQTD20190929172505711,JSGG20210420091802007,GJHZ20210705141807023,JSGG20220831110605009,and JCYJ20210324115413036)the Guangdong Basic and Applied Basic Research Foundation(2021B1515120009)the Department of Guangdong Science and Technology(2019JC01Z031).
文摘Machining high-performance engineering materials,faces challenges including low machining efficiency,poor workpiece surface integrity,and rapid tool wear,which restrict high quality and efficient machining.Ultra-high-speed machining(UHSM)has been expected to address these issues.However,the material removal mechanisms involved in UHSM remain unclear and need further exploration.This paper reviews the criteria for evaluating the ductile and brittle behaviors of high-performance materials subjected to machining,as well as the developmental history of the material’s ductile-brittle transition induced by machining,proposing the concept of relativization of ductile-brittle property.Additionally,it further summarizes three typical material removal mechanisms:ductile-mode removal based on shear stress,brittle-mode removal based on tensile stress,and extrusion removal based on compressive stress,clarifying the universality of the brittle-mode removal.On this basis,this paper focuses on the discussion of the material removal mechanisms in UHSM,including high strain-rate-induced material embrittlement,UHSM-induced skin effect of damage,and the thermal effect in UHSM.Furthermore,it provides a detailed description of the typical characteristics of chip morphology in the ductile-brittle transition region(DBTR)under the high strain rate condition and,for the first time,elucidates the material removal mechanisms in the DBTR from a microstructural dislocation perspective,enriching the basic theory of UHSM.In the discussion section,it standardizes the definition for the UHSM,and explores the dislocation movement at high strain rates and the crack propagation in the UHSM.Finally,based on the current status of the UHSM technology,it summarizes the relevant research hotspots.For the first time,this paper brings up the brittle-mode removal mechanism under ultra-high-speed conditions,which is helpful to promote the UHSM for industrial applications.
基金Supported by Shenzhen Municipal Science and Technology Innovation Commission of China(Grant Nos.Y01336107,GJHZ20180411143506667,JCYJ20170817111811303).
文摘The Ti6Al4V parts produced by the existing selective laser melting(SLM)are mainly confronted with poor surface finish and inevitable interior defects,which substantially deteriorates the mechanical properties and performances of the parts.In this regard,ultrasonically-assisted machining(UAM)technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force.However,most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions,whereas few of them on the impact of ultrasonic vibration along the vertical direction.In this study,the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling(UAVM)of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining(CM)method.The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style.The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter.Moreover,the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter.As feed rate increased,surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation,while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter.Therefore,the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM.In general,the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.
基金Supported by Shenzhen Municipal Science and Technology Innovation Commission of China(Grant Nos.KQTD20190929172505711,JSGG20210420091802007,GJHZ20210705141807023).
文摘Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical performance.However,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the workpiece.In this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding wheel.The relationship between grinding speed,SQ and subsurface damage(SSD)was well studied.With increasing grinding speed,surface roughness decreased,and SQ was greatly improved.Meanwhile,the microhardness of the grinding surface declined as the grinding speed increased.The SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding speeds.It was attributed to the mechanical-thermal synergistic effect in the grinding process.The results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 alloy.The conclusion in the work may also provide insight into processing other hard-to-machining materials.
