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
Generally,a subsoiler is comprised of a shank and a point.The point shape has a significant effect on the draft force of a subsoiler.In this study,the draft force of subsoilers with four different points were compared...Generally,a subsoiler is comprised of a shank and a point.The point shape has a significant effect on the draft force of a subsoiler.In this study,the draft force of subsoilers with four different points were compared under the speed of 0.8 m/s and the depth of 350 mm in the soil bin.Discrete Element Method(DEM)was applied in simulating the working process of the subsoiler.The stiffness of soil particles used in DEM was calibrated by comparing the simulated draft force of a standard arc-shaped subsoiler with the experiment.The calibrated soil particle stiffness was 1.1×104 N/m.The validated model was then used to compare the draft force of subsoilers with four different points under the same condition in the test.Results showed that different points would cause different draft forces.The subsoiler with short chisel point caused the smallest draft force(2885 N)while the point with short face and wings had the largest force(4474 N).The relative errors of the simulated results were less than 4%,which proved that DEM was an effective way for predicting the draft force of subsilers.The velocity field and contact force filed could show the movement of soil around the subsoiler.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the National Science and Technology Supporting Plan of China(2011BAD29B08).
文摘Generally,a subsoiler is comprised of a shank and a point.The point shape has a significant effect on the draft force of a subsoiler.In this study,the draft force of subsoilers with four different points were compared under the speed of 0.8 m/s and the depth of 350 mm in the soil bin.Discrete Element Method(DEM)was applied in simulating the working process of the subsoiler.The stiffness of soil particles used in DEM was calibrated by comparing the simulated draft force of a standard arc-shaped subsoiler with the experiment.The calibrated soil particle stiffness was 1.1×104 N/m.The validated model was then used to compare the draft force of subsoilers with four different points under the same condition in the test.Results showed that different points would cause different draft forces.The subsoiler with short chisel point caused the smallest draft force(2885 N)while the point with short face and wings had the largest force(4474 N).The relative errors of the simulated results were less than 4%,which proved that DEM was an effective way for predicting the draft force of subsilers.The velocity field and contact force filed could show the movement of soil around the subsoiler.
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
