High-energy pulsed laser radiation may be the most feasible means to mitigate the threat of collision of a space station or other valuable space assets with orbital debris in the size range of 1–10 cm. Under laser ir...High-energy pulsed laser radiation may be the most feasible means to mitigate the threat of collision of a space station or other valuable space assets with orbital debris in the size range of 1–10 cm. Under laser irradiation, part of the debris material is ablated and provides an impulse to the debris particle. Proper direction of the impulse vector either deflects the object trajectory or forces the debris on a trajectory through the upper atmosphere, where it burns up. Most research concentrates on ground-based laser systems but pays little attention to space-based laser systems.There are drawbacks of a ground-based laser system in cleaning space debris. Therefore the placement of a laser system in space is proposed and investigated. Under assumed conditions,the elimination process of space debris is analyzed. Several factors such as laser repetition frequency, relative movement between the laser and debris, and inclination of debris particles which may exercise influence to the elimination effects are discussed. A project of a space-based laser system is proposed according to the numerical results of a computer study. The proposed laser system can eliminate debris of 1–10 cm and succeed in protecting a space station.展开更多
Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large ...Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large spot size,easily leading to high processing costs and overheating of bulk materials.In this paper,a new approach of selective laser ablation assisted milling(SLA-Mill)process for nickel-based superalloys was proposed,in which low power laser with small spot size was used to selectively ablate the uncut surface in front of the cutting tool,resulting in plentiful surface defects emerging.Such defects would significantly weaken the mechanical strength of difficult-to-cut materials,which was different from the thermal“softening”principle of conventional LAM.Thus,the laser ablation effect with low power and small spot size was first studied.The relationship between process parameters(e.g.,laser power,cutting speed and cutting depth)and process characteristics of SLA-Mill(e.g.,chip morphology,tool wear and surface integrity)was systematically discussed.Moreover,the chip formation mechanism in the SLA-Mill process was indepth analyzed.Results show that the SLA-Mill process is an effective approach for enhancing the machinability of nickel-based superalloys.The resultant cutting force has a reduction of about 30%at laser power of 60 W,cutting speed of 90 m/min,and cutting depth of 0.1 mm.Furthermore,the chip formation,tool wear,and surface integrity have improved significantly.In general,this paper provides a new route for the application of LAM technology.展开更多
基金supported by the National Natural Science Foundation of China(No:11102234)Provincial Level Project of China
文摘High-energy pulsed laser radiation may be the most feasible means to mitigate the threat of collision of a space station or other valuable space assets with orbital debris in the size range of 1–10 cm. Under laser irradiation, part of the debris material is ablated and provides an impulse to the debris particle. Proper direction of the impulse vector either deflects the object trajectory or forces the debris on a trajectory through the upper atmosphere, where it burns up. Most research concentrates on ground-based laser systems but pays little attention to space-based laser systems.There are drawbacks of a ground-based laser system in cleaning space debris. Therefore the placement of a laser system in space is proposed and investigated. Under assumed conditions,the elimination process of space debris is analyzed. Several factors such as laser repetition frequency, relative movement between the laser and debris, and inclination of debris particles which may exercise influence to the elimination effects are discussed. A project of a space-based laser system is proposed according to the numerical results of a computer study. The proposed laser system can eliminate debris of 1–10 cm and succeed in protecting a space station.
基金This paper was funded by the National Natural Science Foundation of China(Grant Nos.51375174 and 52075187)the Natural Science Foundation of Guangdong Province(Grant No.2017A030313260)the Fundamental Research Funds for the Central University(Grant No.2017ZD024).
文摘Laser-assisted machining(LAM),as one of the most efficient ways,has been employed to improve the machinability of nickel-based superalloys.However,the conventional LAM process usually used high power laser with large spot size,easily leading to high processing costs and overheating of bulk materials.In this paper,a new approach of selective laser ablation assisted milling(SLA-Mill)process for nickel-based superalloys was proposed,in which low power laser with small spot size was used to selectively ablate the uncut surface in front of the cutting tool,resulting in plentiful surface defects emerging.Such defects would significantly weaken the mechanical strength of difficult-to-cut materials,which was different from the thermal“softening”principle of conventional LAM.Thus,the laser ablation effect with low power and small spot size was first studied.The relationship between process parameters(e.g.,laser power,cutting speed and cutting depth)and process characteristics of SLA-Mill(e.g.,chip morphology,tool wear and surface integrity)was systematically discussed.Moreover,the chip formation mechanism in the SLA-Mill process was indepth analyzed.Results show that the SLA-Mill process is an effective approach for enhancing the machinability of nickel-based superalloys.The resultant cutting force has a reduction of about 30%at laser power of 60 W,cutting speed of 90 m/min,and cutting depth of 0.1 mm.Furthermore,the chip formation,tool wear,and surface integrity have improved significantly.In general,this paper provides a new route for the application of LAM technology.
