High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effect...High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques.This study proposes a novel cutting-based process,namely elliptical vibration chiseling(EV-chiseling),for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio.Unlike conventional cutting,EV-chiseling superimposes a microscale EV on a backward-moving tool.The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation.Thanks to the tool’s backward movement,the chip is left on the material surface to form a microstructure rather than falling off.Since one microstructure is generated in one vibration cycle,the process can be highly efficient using ultrafast(>1 kHz)tool vibration.A finite element analysis model is established to explore the process mechanics of EV-chiseling.Next,a mechanistic model of the microstructured surface generation is developed to describe the microstructures’aspect ratio dependency on the process parameters.Then,surface texturing tests are performed on copper to verify the efficacy of EV-chiseling.Uniformed micro ribs with a spacing of 1–10μm and an aspect ratio of 2–5 have been successfully textured on copper.Compared with the conventional EV-cutting that uses a forward-moving tool,EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times.The experimental results also verify the accuracy of the developed surface generation model of microstructures.Finally,the effects of elliptical trajectory,depth of cut,tool shape,and tool edge radius on the surface generation of micro ribs have been discussed.展开更多
To solve the difficulty in ditching for the deep fertilization in tea gardens caused by the high quantity of tea branches and stubbles,a new ditching device combined with a kind of rotary tillage and chisel shovel was...To solve the difficulty in ditching for the deep fertilization in tea gardens caused by the high quantity of tea branches and stubbles,a new ditching device combined with a kind of rotary tillage and chisel shovel was designed.The combined ditching device worked by the following steps:Firstly,the stubble,such as fallen leaves and weeds between the rows,was cleaned up and thrown away by the rotary tillage.Then,the chisel-shaped fertilizing shovel forcefully dug into the soil,realizing the deep fertilization groove.The parameters of the rotary tillage and stubble-throwing device and the chisel-shaped fertilizing shovel were optimized by single factor test and quadratic regression orthogonal rotation test,respectively.The optimization results showed that when the number of stubble-throwing blades of the rotary tillage and stubble-throwing device was five,and the blade installation inclination angle was 16°,the stubble removal rate was the highest at the high speed of the cutter(300 r/min),which was 91.64%.When the entry angle of the chisel-shaped fertilizing shovel was 30°,the entry clearance angle was 8°,and the operating speed was 0.7 m/s,the stability coefficient of the groove depth was 94.9%,which was the optimal parameter of the chisel-shaped fertilizing shovel.The field experiment showed that the average width of the ditching was 224 mm(between 202-248 mm),the average depth of the groove was 194.9 mm(between 173-218 mm),and the stability coefficient of the groove depth could reach 92.78%,realizing stable lateral deep fertilization in the tea garden.展开更多
According to some archaeological discoveries, people began to use gold to make ornaments during the Shang Dynasty, more than 3,000 years ago. This partfcular piece of chiseled gold ornament was unearthed in 1957 from ...According to some archaeological discoveries, people began to use gold to make ornaments during the Shang Dynasty, more than 3,000 years ago. This partfcular piece of chiseled gold ornament was unearthed in 1957 from the Ming Dynasty tomb of Wang Gui at You’anmen, Beijing. Wang Gui was a head of the Imperial Bodyguard in the Ming Dynasty. His eldest daughter was an imperial concubine of the Emperor Cheng Hua. Consequently, his family held a prominent position at the time. The gold ornament, 50.5 centimeters in length and 295 grams in weight, is composed of two parts. The upper part is shaped like lotus leaves, with fine double lines as the vein. To indicate auspiciousness, a pair of mandarin ducks with lotus flowers in their months sit on either side of the thick leaves. Seven long gold chains measuring 21 centimeters in length link展开更多
基金support for this research provided by the National Natural Science Foundation of China(Grant No.52105458)Beijing Natural Science Foundation(Grant No.3222009)+1 种基金Huaneng Group Science and Technology Research Project(No:HNKJ22-H105)China Postdoctoral Science Foundation(Grant No.2022M711807)。
文摘High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications,such as high-performance heat transfer enhancement and surface plasmon devices.However,the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques.This study proposes a novel cutting-based process,namely elliptical vibration chiseling(EV-chiseling),for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio.Unlike conventional cutting,EV-chiseling superimposes a microscale EV on a backward-moving tool.The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation.Thanks to the tool’s backward movement,the chip is left on the material surface to form a microstructure rather than falling off.Since one microstructure is generated in one vibration cycle,the process can be highly efficient using ultrafast(>1 kHz)tool vibration.A finite element analysis model is established to explore the process mechanics of EV-chiseling.Next,a mechanistic model of the microstructured surface generation is developed to describe the microstructures’aspect ratio dependency on the process parameters.Then,surface texturing tests are performed on copper to verify the efficacy of EV-chiseling.Uniformed micro ribs with a spacing of 1–10μm and an aspect ratio of 2–5 have been successfully textured on copper.Compared with the conventional EV-cutting that uses a forward-moving tool,EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times.The experimental results also verify the accuracy of the developed surface generation model of microstructures.Finally,the effects of elliptical trajectory,depth of cut,tool shape,and tool edge radius on the surface generation of micro ribs have been discussed.
基金supported by the National Natural Science Foundation of China(Grant No.52175233).
文摘To solve the difficulty in ditching for the deep fertilization in tea gardens caused by the high quantity of tea branches and stubbles,a new ditching device combined with a kind of rotary tillage and chisel shovel was designed.The combined ditching device worked by the following steps:Firstly,the stubble,such as fallen leaves and weeds between the rows,was cleaned up and thrown away by the rotary tillage.Then,the chisel-shaped fertilizing shovel forcefully dug into the soil,realizing the deep fertilization groove.The parameters of the rotary tillage and stubble-throwing device and the chisel-shaped fertilizing shovel were optimized by single factor test and quadratic regression orthogonal rotation test,respectively.The optimization results showed that when the number of stubble-throwing blades of the rotary tillage and stubble-throwing device was five,and the blade installation inclination angle was 16°,the stubble removal rate was the highest at the high speed of the cutter(300 r/min),which was 91.64%.When the entry angle of the chisel-shaped fertilizing shovel was 30°,the entry clearance angle was 8°,and the operating speed was 0.7 m/s,the stability coefficient of the groove depth was 94.9%,which was the optimal parameter of the chisel-shaped fertilizing shovel.The field experiment showed that the average width of the ditching was 224 mm(between 202-248 mm),the average depth of the groove was 194.9 mm(between 173-218 mm),and the stability coefficient of the groove depth could reach 92.78%,realizing stable lateral deep fertilization in the tea garden.
文摘According to some archaeological discoveries, people began to use gold to make ornaments during the Shang Dynasty, more than 3,000 years ago. This partfcular piece of chiseled gold ornament was unearthed in 1957 from the Ming Dynasty tomb of Wang Gui at You’anmen, Beijing. Wang Gui was a head of the Imperial Bodyguard in the Ming Dynasty. His eldest daughter was an imperial concubine of the Emperor Cheng Hua. Consequently, his family held a prominent position at the time. The gold ornament, 50.5 centimeters in length and 295 grams in weight, is composed of two parts. The upper part is shaped like lotus leaves, with fine double lines as the vein. To indicate auspiciousness, a pair of mandarin ducks with lotus flowers in their months sit on either side of the thick leaves. Seven long gold chains measuring 21 centimeters in length link
