Deep microhole machining is currently a prominent research area within the aerospace field,encompassing blade film cooling and fuel injection control technologies.However,taper defects in metal materials may lead to p...Deep microhole machining is currently a prominent research area within the aerospace field,encompassing blade film cooling and fuel injection control technologies.However,taper defects in metal materials may lead to performance degradation or even structural damage over a component’s lifetime.Trepanning and helical drilling,facilitated by ultrashort pulse lasers,have proven more suitable for achieving high-precision,deep holes in metal materials.Nonetheless,excessive repetition rates can also result in severe thermal damage.Various methods are commonly employed for controlling taper,including parameter optimization,assistance,and secondary modification.Tilted laser beam drilling is widely utilized and has been integrated into relevant machining systems for commercial applications.Typical deep microholes include film cooling holes and injection microholes.Laser drilling is a potential machining method for new materials in the aerospace field.Although laser drilling processing has been studied,numerous related scientific challenges and technical difficulties must be addressed before practical implementation.展开更多
Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fin...Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.展开更多
As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs la...As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining(i.e.defects on edges and tapered sidewalls).The evolution of edge sharpness(edge transition width)and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed.Through decreasing the angle of incidence(AOI)from 0◦to−5◦,the edge transition width could be reduced to below 10µm but at the cost of increased sidewall tapers.Furthermore,by analyzing lateral and vertical ablation behaviors,a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls.The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications.The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions.Both mm-scale diameters and depths were realized with dimensional precisions below 10µm and surface roughness below 1µm.This research establishes a novel strategy to finely control the fs laser machining process,enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.展开更多
基金This work was supported by the Science Center for Gas Turbine Project(Grant No.P2022-A-IV-002-003)the National Natural Science Foundation of China(Grant No.52022078)+1 种基金Shaanxi Provincial Key Research and Development Program(Grant No.2021ZDLGY10-02)the fund of the State Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202203).
文摘Deep microhole machining is currently a prominent research area within the aerospace field,encompassing blade film cooling and fuel injection control technologies.However,taper defects in metal materials may lead to performance degradation or even structural damage over a component’s lifetime.Trepanning and helical drilling,facilitated by ultrashort pulse lasers,have proven more suitable for achieving high-precision,deep holes in metal materials.Nonetheless,excessive repetition rates can also result in severe thermal damage.Various methods are commonly employed for controlling taper,including parameter optimization,assistance,and secondary modification.Tilted laser beam drilling is widely utilized and has been integrated into relevant machining systems for commercial applications.Typical deep microholes include film cooling holes and injection microholes.Laser drilling is a potential machining method for new materials in the aerospace field.Although laser drilling processing has been studied,numerous related scientific challenges and technical difficulties must be addressed before practical implementation.
文摘Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.
基金This study was supported by the National Science Foundation(CMMI 1826392)and the Nebraska Center for Energy Sci-ences Research(NCESR)The research was performed in part in the Nebraska Nanoscale Facility:National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Mater-ials and Nanoscience,which are supported by the National Sci-ence Foundation under Award ECCS:1542182,and the Neb-raska Research Initiative.
文摘As femtosecond(fs)laser machining advances from micro/nanoscale to macroscale,approaches capable of machining macroscale geometries that sustain micro/nanoscale precisions are in great demand.In this research,an fs laser sharp shaping approach was developed to address two key challenges in macroscale machining(i.e.defects on edges and tapered sidewalls).The evolution of edge sharpness(edge transition width)and sidewall tapers were systematically investigated through which the dilemma of simultaneously achieving sharp edges and vertical sidewalls were addressed.Through decreasing the angle of incidence(AOI)from 0◦to−5◦,the edge transition width could be reduced to below 10µm but at the cost of increased sidewall tapers.Furthermore,by analyzing lateral and vertical ablation behaviors,a parameter-compensation strategy was developed by gradually decreasing the scanning diameters along depth and using optimal laser powers to produce non-tapered sidewalls.The fs laser ablation behaviors were precisely controlled and coordinated to optimize the parameter compensations in general manufacturing applications.The AOI control together with the parameter compensation provides a versatile solution to simultaneously achieve vertical sidewalls as well as sharp edges of entrances and exits for geometries of different shapes and dimensions.Both mm-scale diameters and depths were realized with dimensional precisions below 10µm and surface roughness below 1µm.This research establishes a novel strategy to finely control the fs laser machining process,enabling the fs laser applications in macroscale machining with micro/nanoscale precisions.
