快速成形技术(rapid prototyping and manufacturing RP&M),又称快速原型制造技术,它能以最快的速度将设计思想物化为具有一定结构和功能的三维实体,低成本制作产品原型甚至零件,非常适合当代市场竞争的需要。但解决熔融挤压快速成...快速成形技术(rapid prototyping and manufacturing RP&M),又称快速原型制造技术,它能以最快的速度将设计思想物化为具有一定结构和功能的三维实体,低成本制作产品原型甚至零件,非常适合当代市场竞争的需要。但解决熔融挤压快速成型机加工品质缺陷问题是确保产品品质的关键,根据熔融挤压快速成型机加工的模型来分析影响模型品质的因素,同时指出在实际加工中,必须根据模型的复杂程度、模型的结构和技术要求来找到最佳的加工方案。展开更多
通常解决连续管在井下遇卡的方法是大力拉拔,断脱后分段打捞,这样易造成连续管报废,同时施工程序复杂且周期较长。为此,研发了热熔式连续管内切割技术。该技术通过电缆将工具下入连续管内卡点附近,通过电缆传输大于500 m A的电流,触发...通常解决连续管在井下遇卡的方法是大力拉拔,断脱后分段打捞,这样易造成连续管报废,同时施工程序复杂且周期较长。为此,研发了热熔式连续管内切割技术。该技术通过电缆将工具下入连续管内卡点附近,通过电缆传输大于500 m A的电流,触发热能发生器内的电热头电阻,产生的热量引燃高能燃料剂,产生高压和强热使其内粒子热运动加剧,进而使所有原子全部电离,利用熔断性进行作业。现场应用结果表明,热熔式内切割工艺解决了连续管遇卡管柱小管径、强弹性、大韧性和无法旋转等打捞难题;避免了大力拉拔和活动解卡带来的连续管塑性变形和屈曲变形等不可逆转的损伤。热熔式内切割工艺为打捞小直径遇卡管柱拓展了思路和方法。展开更多
The construction of N-fused polycyclic compounds at room temperature via the combination of transition-metal catalyst and photocatalyst has been reported.This novel work has successfully realized LED irradiated C—H a...The construction of N-fused polycyclic compounds at room temperature via the combination of transition-metal catalyst and photocatalyst has been reported.This novel work has successfully realized LED irradiated C—H activation of iodonium ylides.The strategy shows wide substrate scope and ideal functional group tolerance.Our work would be useful for the construction of various heterocyclic compounds.展开更多
Based on analyzing the influences of a slicing scheme on stair-stepping effect, supporting structure, efficiency and deformation, etc. , analytical hierarchical process （AHP） combining with fuzzy synthetic evaluatio...Based on analyzing the influences of a slicing scheme on stair-stepping effect, supporting structure, efficiency and deformation, etc. , analytical hierarchical process （AHP） combining with fuzzy synthetic evaluation is introduced to make decision in slicing schemes for a processing part. The application in determining the slicing scheme for a computer mouse during prototyping shows that the method increases the rationality during decision- making and improves quality and efficiency for the prototyping part.展开更多
Recently,low-cost desktop three-dimensional(3D)printers,employing the fused deposition modeling(FDM)technique,have gained widespread popularity.However,most users cannot test the strength of printed parts,and little i...Recently,low-cost desktop three-dimensional(3D)printers,employing the fused deposition modeling(FDM)technique,have gained widespread popularity.However,most users cannot test the strength of printed parts,and little information is available about the mechanical properties of printed high-impact polystyrene(HIPS)parts using desktop 3D printers.In this study,the user-adjustable parameters of desktop 3D printers,such as crisscross raster orientation,layer thickness,and infill density,were tested.The experimental plans were designed using the Box-Behnken method,and tensile,3-point bending,and compression tests were carried out to determine the mechanical responses of the printed HIPS.The prediction models of the process parameters were regressed to produce the optimal combination of process parameters.The experimental results showcase that the crisscross raster orientation has significant effects on the flexural and compression strengths,but not on the tensile strength.With an increase in the layer thickness,the tensile,flexural,and compression strengths first decreased and then increased,reaching their minimum values at approximately 0.16 mm layer thickness.In addition,they all increased with an increase of infill density.It was demonstrated that when the raster orientation,layer thickness,and infill density were 13.08°/–76.92°,0.09 mm,and 80%,respectively,the comprehensive mechanical properties of the printed HIPS were optimal.Our results can help end-users of desktop 3D printers understand the effects of process parameters on the mechanical properties,and offer practical suggestions for setting proper printing parameters for fabricating HIPS parts.展开更多
In order to study the hot melt extrusion process in fused deposition modeling(FDM),this study mainly explores the effects of printing temperature,heated block length,feeding speed on the exit morphology and mechanical...In order to study the hot melt extrusion process in fused deposition modeling(FDM),this study mainly explores the effects of printing temperature,heated block length,feeding speed on the exit morphology and mechanical properties of FDM printed Polylactic acid(PLA)samples.High-speed camera is used to capture the exit morphology of molten PLA just extruded to the nozzle.According to exit morphology,the outlet states of extruded molten material can be divided into four categories,namely,bubbled state,coherent state,expanding state,and unstable state.Tensile test results show that printing temperature,heated block length and printing speed have significant influence on tensile properties and fracture mode of FDM printed samples.When the heated block length is 15 mm and 30 mm,there is a ductile-brittle transition in fracture mode with the increase of printing speed.The printing process window under different heated block lengths and printing temperatures has been figured out and the distribution of printing process window under different printing speeds has been discussed.There is a maximum printing process window under the heated block length of 30 mm.This finding provides a frame work for performance prediction of FDM printed parts and theoretical guidance for expanding the scope of printing process window.展开更多
Residual processing defects during the contact processing processes greatly reduce the anti-ultraviolet(UV)laser damage performance of fused silica optics,which significantly limited development of high-energy laser s...Residual processing defects during the contact processing processes greatly reduce the anti-ultraviolet(UV)laser damage performance of fused silica optics,which significantly limited development of high-energy laser systems.In this study,we demonstrate the manufacturing of fused silica optics with a high damage threshold using a CO_(2)laser process chain.Based on theoretical and experimental studies,the proposed uniform layer-by-layer laser ablation technique can be used to characterize the subsurface mechanical damage in three-dimensional full aperture.Longitudinal ablation resolutions ranging from nanometers to micrometers can be realized;the minimum longitudinal resolution is<5 nm.This technique can also be used as a crack-free grinding tool to completely remove subsurface mechanical damage,and as a cleaning tool to effectively clean surface/subsurface contamination.Through effective control of defects in the entire chain,the laser-induced damage thresholds of samples fabricated by the CO_(2)laser process chain were 41%(0%probability)and 65.7%(100%probability)higher than those of samples fabricated using the conventional process chain.This laser-based defect characterization and removal process provides a new tool to guide optimization of the conventional finishing process and represents a new direction for fabrication of highly damage-resistant fused silica optics for high-energy laser applications.展开更多
文摘快速成形技术(rapid prototyping and manufacturing RP&M),又称快速原型制造技术,它能以最快的速度将设计思想物化为具有一定结构和功能的三维实体,低成本制作产品原型甚至零件,非常适合当代市场竞争的需要。但解决熔融挤压快速成型机加工品质缺陷问题是确保产品品质的关键,根据熔融挤压快速成型机加工的模型来分析影响模型品质的因素,同时指出在实际加工中,必须根据模型的复杂程度、模型的结构和技术要求来找到最佳的加工方案。
文摘通常解决连续管在井下遇卡的方法是大力拉拔,断脱后分段打捞,这样易造成连续管报废,同时施工程序复杂且周期较长。为此,研发了热熔式连续管内切割技术。该技术通过电缆将工具下入连续管内卡点附近,通过电缆传输大于500 m A的电流,触发热能发生器内的电热头电阻,产生的热量引燃高能燃料剂,产生高压和强热使其内粒子热运动加剧,进而使所有原子全部电离,利用熔断性进行作业。现场应用结果表明,热熔式内切割工艺解决了连续管遇卡管柱小管径、强弹性、大韧性和无法旋转等打捞难题;避免了大力拉拔和活动解卡带来的连续管塑性变形和屈曲变形等不可逆转的损伤。热熔式内切割工艺为打捞小直径遇卡管柱拓展了思路和方法。
基金the support from Sichuan Science and Technology Program(No.2020YJ0221).
文摘The construction of N-fused polycyclic compounds at room temperature via the combination of transition-metal catalyst and photocatalyst has been reported.This novel work has successfully realized LED irradiated C—H activation of iodonium ylides.The strategy shows wide substrate scope and ideal functional group tolerance.Our work would be useful for the construction of various heterocyclic compounds.
基金Supported by the Science and Technology Support Key Project of Jiangsu Province (DE2008365)~~
文摘Based on analyzing the influences of a slicing scheme on stair-stepping effect, supporting structure, efficiency and deformation, etc. , analytical hierarchical process （AHP） combining with fuzzy synthetic evaluation is introduced to make decision in slicing schemes for a processing part. The application in determining the slicing scheme for a computer mouse during prototyping shows that the method increases the rationality during decision- making and improves quality and efficiency for the prototyping part.
基金supported by the National Natural Science Foundation of China(Grant No.51975097)the National Key Research and Development Project(Grant No.2020YFA0713702).
文摘Recently,low-cost desktop three-dimensional(3D)printers,employing the fused deposition modeling(FDM)technique,have gained widespread popularity.However,most users cannot test the strength of printed parts,and little information is available about the mechanical properties of printed high-impact polystyrene(HIPS)parts using desktop 3D printers.In this study,the user-adjustable parameters of desktop 3D printers,such as crisscross raster orientation,layer thickness,and infill density,were tested.The experimental plans were designed using the Box-Behnken method,and tensile,3-point bending,and compression tests were carried out to determine the mechanical responses of the printed HIPS.The prediction models of the process parameters were regressed to produce the optimal combination of process parameters.The experimental results showcase that the crisscross raster orientation has significant effects on the flexural and compression strengths,but not on the tensile strength.With an increase in the layer thickness,the tensile,flexural,and compression strengths first decreased and then increased,reaching their minimum values at approximately 0.16 mm layer thickness.In addition,they all increased with an increase of infill density.It was demonstrated that when the raster orientation,layer thickness,and infill density were 13.08°/–76.92°,0.09 mm,and 80%,respectively,the comprehensive mechanical properties of the printed HIPS were optimal.Our results can help end-users of desktop 3D printers understand the effects of process parameters on the mechanical properties,and offer practical suggestions for setting proper printing parameters for fabricating HIPS parts.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11502269 and 11672304)plan of Beijing Municipal Commission of Science and Technology(Grant No.Z181100003818015).
文摘In order to study the hot melt extrusion process in fused deposition modeling(FDM),this study mainly explores the effects of printing temperature,heated block length,feeding speed on the exit morphology and mechanical properties of FDM printed Polylactic acid(PLA)samples.High-speed camera is used to capture the exit morphology of molten PLA just extruded to the nozzle.According to exit morphology,the outlet states of extruded molten material can be divided into four categories,namely,bubbled state,coherent state,expanding state,and unstable state.Tensile test results show that printing temperature,heated block length and printing speed have significant influence on tensile properties and fracture mode of FDM printed samples.When the heated block length is 15 mm and 30 mm,there is a ductile-brittle transition in fracture mode with the increase of printing speed.The printing process window under different heated block lengths and printing temperatures has been figured out and the distribution of printing process window under different printing speeds has been discussed.There is a maximum printing process window under the heated block length of 30 mm.This finding provides a frame work for performance prediction of FDM printed parts and theoretical guidance for expanding the scope of printing process window.
基金supported by the National Key Research and Development Project(2022YFB3403400)Shanghai Sailing Program(20YF1454800)+2 种基金National Natural Science Youth Foundation of China(62205352)Natural Science Foundation of Shanghai(21ZR1472000)Key Projects of the Joint Fund for Astronomy of the National Natural Science Funding of China(U1831211),and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.
文摘Residual processing defects during the contact processing processes greatly reduce the anti-ultraviolet(UV)laser damage performance of fused silica optics,which significantly limited development of high-energy laser systems.In this study,we demonstrate the manufacturing of fused silica optics with a high damage threshold using a CO_(2)laser process chain.Based on theoretical and experimental studies,the proposed uniform layer-by-layer laser ablation technique can be used to characterize the subsurface mechanical damage in three-dimensional full aperture.Longitudinal ablation resolutions ranging from nanometers to micrometers can be realized;the minimum longitudinal resolution is<5 nm.This technique can also be used as a crack-free grinding tool to completely remove subsurface mechanical damage,and as a cleaning tool to effectively clean surface/subsurface contamination.Through effective control of defects in the entire chain,the laser-induced damage thresholds of samples fabricated by the CO_(2)laser process chain were 41%(0%probability)and 65.7%(100%probability)higher than those of samples fabricated using the conventional process chain.This laser-based defect characterization and removal process provides a new tool to guide optimization of the conventional finishing process and represents a new direction for fabrication of highly damage-resistant fused silica optics for high-energy laser applications.
