In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process i...In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.展开更多
Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect.Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large...Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect.Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large aircraft structural parts.The manufacturing of 7075 aluminum alloy structural parts by laser engineered net shaping technology has become an important development direction in the future aerospace field.Electrochemical corrosion resistance of aluminum alloys is of vital importance to improve reliability and life-span of lightweight components.A comparative study on microstructure and anti-corrosion performance of Al7075 alloy prepared by laser additive manufacturing and forging technology was conducted.There are hole defects in LENS-fabricated Al7075 alloy with uniformly distributedηphase.No defects are observed in Al7075 forgings.The large S phase particles and small ellipsoidalηphase particles are found in Al matrix.The corrosion mechanisms were revealed according to the analysis of polarization curves and corrosion morphology.It was found that compared with that prepared by forgings,the additive manufactured samples have lower corrosion tendency and higher corrosion rate.Corrosion occurred preferentially at the hole defects.The incomplete passivation film at the defects leads to the formation of a local cell composed of the internal Al,corrosion solution and the surrounding passive film,which further aggravates the corrosion.展开更多
The present work explored effects of laser surface melting on microstructure and surface topography evolution in AZ31B magnesium alloy.Thermokinetic effects experienced by the material during laser surface melting wer...The present work explored effects of laser surface melting on microstructure and surface topography evolution in AZ31B magnesium alloy.Thermokinetic effects experienced by the material during laser surface melting were simulated using a multiphysics finite element model.Microstructure and phase evolution were examined using scanning electron microscopy,X-ray diffraction,and electron back scatter diffraction.Surface topography was evaluated using white light interferometry.The interaction of surface melted samples with simulated body fluid was monitored by contact angle measurements and immersion studies up to 7 days.Laser surface melting led to formation of a refined microstructure with predominantly basal crystallographic texture.Concurrently,the amount ofβphase(Mg_(17)Al_(12))increased with an increase in the laser fluence.βphase preferentially decorated the cell boundaries.In terms of topography,the surface became progressively rougher with an increase in laser fluence.As a result,upon immersion in simulated body fluid,the laser surface melted samples showed an improved wettability,corrosion resistance,and precipitation of mineral having composition closer to the hydroxyapatite bone mineral compared to the untreated sample.展开更多
Metal superhydrophobic surfaces with anisotropic wettability and adhesion have become more and more important due to their promising applications. Herein, we report a new fabrication strategy through a combination of ...Metal superhydrophobic surfaces with anisotropic wettability and adhesion have become more and more important due to their promising applications. Herein, we report a new fabrication strategy through a combination of pulsed laser ablation and low-temperature annealing post-processing. An inclined cone structure array is made on stainless steel surfaces, and then 120 °C low-temperature annealing is applied. Such surface displays excellent mechanical durability and anisotropic superhydrophobicity. It is demonstrated experimentally that the contact angle of water droplets on the surface is different along the parallel(167° ±2°) and perpendicular directions(157° ±2°) of the inclined cone structure. The sliding behaviors of water droplets and mechanical durability of the inclined cone structures are studied. These surfaces obtained in a short time with environmentally friendly fabrication can be applied in industries for water harvesting, droplet manipulation, and pipeline transportation.展开更多
An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, clo...An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.展开更多
Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabil...Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabilities.However,achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions,given their polychromatic bandwidth.This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior.We developed a comprehensive approach to directly design and govern these laser pulses.This method elucidates the role jointly played by the pulse's spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics.It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses.By tailoring the prescribed phase gradient,we demonstrate the creation of,to our knowledge,novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries.The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail.For instance,the intensity peak can be configured as a THz rotating light spot or shaped as a curve,enabling simultaneous substrate illumination at rates of tens of THz,far exceeding the MHz rates typically used in laser material processing.Additionally,the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam.Together,these advancements unveil advantageous capabilities that have been sought after for many years,especially in ultrafast optics and light-matter interaction research.展开更多
Late in-stent thrombus and restenosis still represent two major challenges in stents’design.Surface treatment of stent is attracting attention due to the increasing importance of stenting intervention for coronary ar...Late in-stent thrombus and restenosis still represent two major challenges in stents’design.Surface treatment of stent is attracting attention due to the increasing importance of stenting intervention for coronary artery diseases.Several surface engineering techniques have been utilised to improve the biological response in vivo on a wide range of biomedical devices.As a tailorable,precise,and ultra-fast process,laser surface engineering offers the potential to treat stent materials and fabricate various 3D textures,including grooves,pillars,nanowires,porous and freeform structures,while also modifying surface chemistry through nitridation,oxidation and coatings.Laser-based processes can reduce the biodegradable materials’degradation rate,offering many advantages to improve stents’performance,such as increased endothelialisation rate,prohibition of SMC proliferation,reduced platelet adhesion and controlled corrosion and degradation.Nowadays,adequate research has been conducted on laser surface texturing and surface chemistry modification.Laser texturing on commercial stents has been also investigated and a promotion of performance of laser-textured stents has been proved.In this critical review,the influence of surface texture and surface chemistry on stents performance is firstly reviewed to understand the surface characteristics of stents required to facilitate cellular response.This is followed by the explicit illustration of laser surface engineering of stents and/or related materials.Laser induced periodic surface structure(LIPSS)on stent materials is then explored,and finally the application of laser surface modification techniques on latest generation of stent devices is highlighted to provide future trends and research direction on laser surface engineering of stents.展开更多
9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held...9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),展开更多
This paper reports the continuous wave （CW） and Q-switched operation of a diode pumped KGd （WO4）： Nd （Nd：KGW） slab laser with a comer pumped geometry at the wavelength of 1067 nm. With an optical conversion ef...This paper reports the continuous wave （CW） and Q-switched operation of a diode pumped KGd （WO4）： Nd （Nd：KGW） slab laser with a comer pumped geometry at the wavelength of 1067 nm. With an optical conversion efficiency of 38% and 34%, average powers of 23 and 20 W in CW and Q-switched modes were achieved respec- tively. The maximum pulse energy of 27 mJ was observed with a repetition rate of 840 Hz.展开更多
基金This work was financially supported by the National Key R&D Program of China(Grant No.2017YFB1103900)National Natural Science Foundation of China(Grant No.11972084)+1 种基金National Science and Technology Major Project(2017-VI-0003-0073)Beijing National Science Foundation(1192014).
文摘In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.
基金Project(2016YFB1100101)supported by the National Key Research and Development Program of China。
文摘Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect.Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large aircraft structural parts.The manufacturing of 7075 aluminum alloy structural parts by laser engineered net shaping technology has become an important development direction in the future aerospace field.Electrochemical corrosion resistance of aluminum alloys is of vital importance to improve reliability and life-span of lightweight components.A comparative study on microstructure and anti-corrosion performance of Al7075 alloy prepared by laser additive manufacturing and forging technology was conducted.There are hole defects in LENS-fabricated Al7075 alloy with uniformly distributedηphase.No defects are observed in Al7075 forgings.The large S phase particles and small ellipsoidalηphase particles are found in Al matrix.The corrosion mechanisms were revealed according to the analysis of polarization curves and corrosion morphology.It was found that compared with that prepared by forgings,the additive manufactured samples have lower corrosion tendency and higher corrosion rate.Corrosion occurred preferentially at the hole defects.The incomplete passivation film at the defects leads to the formation of a local cell composed of the internal Al,corrosion solution and the surrounding passive film,which further aggravates the corrosion.
文摘The present work explored effects of laser surface melting on microstructure and surface topography evolution in AZ31B magnesium alloy.Thermokinetic effects experienced by the material during laser surface melting were simulated using a multiphysics finite element model.Microstructure and phase evolution were examined using scanning electron microscopy,X-ray diffraction,and electron back scatter diffraction.Surface topography was evaluated using white light interferometry.The interaction of surface melted samples with simulated body fluid was monitored by contact angle measurements and immersion studies up to 7 days.Laser surface melting led to formation of a refined microstructure with predominantly basal crystallographic texture.Concurrently,the amount ofβphase(Mg_(17)Al_(12))increased with an increase in the laser fluence.βphase preferentially decorated the cell boundaries.In terms of topography,the surface became progressively rougher with an increase in laser fluence.As a result,upon immersion in simulated body fluid,the laser surface melted samples showed an improved wettability,corrosion resistance,and precipitation of mineral having composition closer to the hydroxyapatite bone mineral compared to the untreated sample.
基金Project(A19C2a0019) supported by the Advanced Remanufacturing and Technology Centre (ARTC) under its RIE2020 Advanced Manufacturing and Engineering (AME) IAF PP,Singapore。
文摘Metal superhydrophobic surfaces with anisotropic wettability and adhesion have become more and more important due to their promising applications. Herein, we report a new fabrication strategy through a combination of pulsed laser ablation and low-temperature annealing post-processing. An inclined cone structure array is made on stainless steel surfaces, and then 120 °C low-temperature annealing is applied. Such surface displays excellent mechanical durability and anisotropic superhydrophobicity. It is demonstrated experimentally that the contact angle of water droplets on the surface is different along the parallel(167° ±2°) and perpendicular directions(157° ±2°) of the inclined cone structure. The sliding behaviors of water droplets and mechanical durability of the inclined cone structures are studied. These surfaces obtained in a short time with environmentally friendly fabrication can be applied in industries for water harvesting, droplet manipulation, and pipeline transportation.
基金Project(51274250)supported by the National Natural Science Foundation of ChinaProject(2012BAK09B02-05)supported by the National Key Technology R&D Program during the 12th Five-year Plan of China
文摘An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.
基金Ministerio de Ciencia,Innovación y Universidades(PID2021-125483NB-I00,PGC2018-095595-B-I00)。
文摘Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications.Controlling their spatiotemporal behavior,tailored to specific applications,can unlock new experimental capabilities.However,achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions,given their polychromatic bandwidth.This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior.We developed a comprehensive approach to directly design and govern these laser pulses.This method elucidates the role jointly played by the pulse's spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics.It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses.By tailoring the prescribed phase gradient,we demonstrate the creation of,to our knowledge,novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries.The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail.For instance,the intensity peak can be configured as a THz rotating light spot or shaped as a curve,enabling simultaneous substrate illumination at rates of tens of THz,far exceeding the MHz rates typically used in laser material processing.Additionally,the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam.Together,these advancements unveil advantageous capabilities that have been sought after for many years,especially in ultrafast optics and light-matter interaction research.
文摘Late in-stent thrombus and restenosis still represent two major challenges in stents’design.Surface treatment of stent is attracting attention due to the increasing importance of stenting intervention for coronary artery diseases.Several surface engineering techniques have been utilised to improve the biological response in vivo on a wide range of biomedical devices.As a tailorable,precise,and ultra-fast process,laser surface engineering offers the potential to treat stent materials and fabricate various 3D textures,including grooves,pillars,nanowires,porous and freeform structures,while also modifying surface chemistry through nitridation,oxidation and coatings.Laser-based processes can reduce the biodegradable materials’degradation rate,offering many advantages to improve stents’performance,such as increased endothelialisation rate,prohibition of SMC proliferation,reduced platelet adhesion and controlled corrosion and degradation.Nowadays,adequate research has been conducted on laser surface texturing and surface chemistry modification.Laser texturing on commercial stents has been also investigated and a promotion of performance of laser-textured stents has been proved.In this critical review,the influence of surface texture and surface chemistry on stents performance is firstly reviewed to understand the surface characteristics of stents required to facilitate cellular response.This is followed by the explicit illustration of laser surface engineering of stents and/or related materials.Laser induced periodic surface structure(LIPSS)on stent materials is then explored,and finally the application of laser surface modification techniques on latest generation of stent devices is highlighted to provide future trends and research direction on laser surface engineering of stents.
文摘9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),
文摘This paper reports the continuous wave （CW） and Q-switched operation of a diode pumped KGd （WO4）： Nd （Nd：KGW） slab laser with a comer pumped geometry at the wavelength of 1067 nm. With an optical conversion efficiency of 38% and 34%, average powers of 23 and 20 W in CW and Q-switched modes were achieved respec- tively. The maximum pulse energy of 27 mJ was observed with a repetition rate of 840 Hz.
