Magnesium(Mg)alloy stents are expected to be the next generation of stents because of good biocompatibility and biodegradability.Compared with cold drawing,dieless drawing with local heating is an effective method for...Magnesium(Mg)alloy stents are expected to be the next generation of stents because of good biocompatibility and biodegradability.Compared with cold drawing,dieless drawing with local heating is an effective method for manufacturing the Mg alloy microtubes since a large reduction in area can be achieved in a single pass.However,the microstructure and properties of dieless drawn tubes have not been clarified,leading to the problems in practical application of dieless drawn tubes.In this study,the microstructure and performance of dieless drawn tubes are clarified.The results show that temperature and speed in the dieless drawing process are two factors in determining the grain size of dieless drawn tubes since decreasing the temperature or increasing the speed promotes the generation of fine-grained microstructure.Twins are also generated during the dieless drawing process,which 1)disintegrates grains leading to refinement and 2)causes Hall-Petch law effect on dieless drawn tubes.Tensile tests show that grain size is the main factor in determining the mechanical properties of dieless drawn tubes,namely,0.2%proof stress 135-180MPa,ultimate tensile strength(UTS)200-250MPa,and elongation 8-12%.In 0.9 wt%NaCl solution,localized corrosion is the key factor in initiating the corrosion of dieless drawn tubes,but refined grains and fewer twins can alleviate local corrosion.These results imply that dieless drawn tubes are promising in the clinical application of Mg alloy stents for cardiovascular disease.展开更多
Stresses and axial loads acting on the mandrel in the copper rifled tube drawing process were analysed,and factors affecting on the axial loads on mandrel were discussed.Results show that the depth of the mandrel drag...Stresses and axial loads acting on the mandrel in the copper rifled tube drawing process were analysed,and factors affecting on the axial loads on mandrel were discussed.Results show that the depth of the mandrel dragged into sizing zone and lubrication have major influence on drawing loads and fin shapes.展开更多
The crystal orientation and outer surface roughening of magnesium alloy tubes were evaluated to clarify the effect of the mandrel on the microstructure and outer surface roughness in die-less mandrel drawing. Locally ...The crystal orientation and outer surface roughening of magnesium alloy tubes were evaluated to clarify the effect of the mandrel on the microstructure and outer surface roughness in die-less mandrel drawing. Locally heated ZM21 tubes with an outer diameter of 6.0 mm and an inner diameter of 3.8 mm were drawn with and without a mandrel. The outer surface roughness and crystal orientation were evaluated in the same measurement area. The results indicated that the outer surface becomes rougher in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. The outer surface roughness developed when there was large difference in the pyramidal slip system Schmid factor. Therefore, the slip deformation of the pyramidal slip system seems to be mainly responsible for the outer surface roughening in the die-less mandrel drawing. Furthermore, the crystal grain with the {2110} crystal plane vertical to the normal direction of outer surface had a larger Schmid factor than the other crystal grains. The large number of crystal grains with the {2110} crystal plane in the die-less mandrel drawing is one of the reasons that the outer surface roughness develops more in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. These results will contribute significantly to the development of fabrication process of the microtube with high surface quality, which prevents rapid corrosion of biomedical applications.展开更多
The effect of revend con ede and length of Plug on nstalnt nd elimination of distortion of internal spi-ral ribs is theoretically analysed. Metheds of the Plug in rifled tubes drawing and a uniform-Pitch Plug with a c...The effect of revend con ede and length of Plug on nstalnt nd elimination of distortion of internal spi-ral ribs is theoretically analysed. Metheds of the Plug in rifled tubes drawing and a uniform-Pitch Plug with a certainreversed cone angle is proposed for drawing rifled tubes.展开更多
In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis meth...In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.展开更多
Teaching and learning-related activities have embraced digital technology especially,with the current global pandemic restrictions pervaded during the last two years.On the other hand,most of the academic and professi...Teaching and learning-related activities have embraced digital technology especially,with the current global pandemic restrictions pervaded during the last two years.On the other hand,most of the academic and professional presentations are conducted using online platforms.But the presenter-audience interaction is hindered to a certain extent in an online case in contrary to face-to-face where real-time writing is beneficial when sketching is involved.The use of digital pens and pads is a solution for such instances,though the cost of acquiring such hardware is high.Economical solutions are essential as affordability is concerned.In this study,a real-time user-friendly,innovative drawing system is developed to address the issues related to the problems confronted with online presentations.This paper presents the development of an algorithm using Hand Landmark Detection,which replaces chalks,markers and regular ballpoint pens used in conventional communication and presentation,with online platforms.The proposed application in this study is acquired by Python and OpenCV libraries.The letters or the sketches drawn in the air were taken straight to the computer screen by this algorithm.The proposed algorithm continuously identifies the Hand Landmark using the images fed by the web camera,and text or drawing patterns are displayed on the screen according to the movements made by Hand Landmark on the image space.The developed user interface is also user-friendly.Hence the communication of letters and sketches were enabled.Although the concept has been developed and tested,with further research the versatility and accuracy of communication can be enhanced.展开更多
Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved...Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved, and the friction between metal and tool was decreased. Corrosion strip layers and photo-elastic coatings methods were adopted in the experiment for measuring residual stress, and the residual stresses in the drawn tube with 3-roll dies are reduced.展开更多
基金JSTP KAKENHI Grant Number 19H02476JKA and its promotion funds from KEIRIN RACE.Peihua Du thanks China Scholarship Council for the award of fellowship and funding(No.201707040058).
文摘Magnesium(Mg)alloy stents are expected to be the next generation of stents because of good biocompatibility and biodegradability.Compared with cold drawing,dieless drawing with local heating is an effective method for manufacturing the Mg alloy microtubes since a large reduction in area can be achieved in a single pass.However,the microstructure and properties of dieless drawn tubes have not been clarified,leading to the problems in practical application of dieless drawn tubes.In this study,the microstructure and performance of dieless drawn tubes are clarified.The results show that temperature and speed in the dieless drawing process are two factors in determining the grain size of dieless drawn tubes since decreasing the temperature or increasing the speed promotes the generation of fine-grained microstructure.Twins are also generated during the dieless drawing process,which 1)disintegrates grains leading to refinement and 2)causes Hall-Petch law effect on dieless drawn tubes.Tensile tests show that grain size is the main factor in determining the mechanical properties of dieless drawn tubes,namely,0.2%proof stress 135-180MPa,ultimate tensile strength(UTS)200-250MPa,and elongation 8-12%.In 0.9 wt%NaCl solution,localized corrosion is the key factor in initiating the corrosion of dieless drawn tubes,but refined grains and fewer twins can alleviate local corrosion.These results imply that dieless drawn tubes are promising in the clinical application of Mg alloy stents for cardiovascular disease.
文摘Stresses and axial loads acting on the mandrel in the copper rifled tube drawing process were analysed,and factors affecting on the axial loads on mandrel were discussed.Results show that the depth of the mandrel dragged into sizing zone and lubrication have major influence on drawing loads and fin shapes.
基金supported by JSPS KAKENHI Grant Nos. 19H02476 and 20KK0321the Amada Foundation Grant No. AF-2021035-C2a project researcher under financial support from the Institute of Industrial Science of the University of Tokyo。
文摘The crystal orientation and outer surface roughening of magnesium alloy tubes were evaluated to clarify the effect of the mandrel on the microstructure and outer surface roughness in die-less mandrel drawing. Locally heated ZM21 tubes with an outer diameter of 6.0 mm and an inner diameter of 3.8 mm were drawn with and without a mandrel. The outer surface roughness and crystal orientation were evaluated in the same measurement area. The results indicated that the outer surface becomes rougher in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. The outer surface roughness developed when there was large difference in the pyramidal slip system Schmid factor. Therefore, the slip deformation of the pyramidal slip system seems to be mainly responsible for the outer surface roughening in the die-less mandrel drawing. Furthermore, the crystal grain with the {2110} crystal plane vertical to the normal direction of outer surface had a larger Schmid factor than the other crystal grains. The large number of crystal grains with the {2110} crystal plane in the die-less mandrel drawing is one of the reasons that the outer surface roughness develops more in the die-less mandrel drawing than in die-less drawing for a given outer circumferential strain. These results will contribute significantly to the development of fabrication process of the microtube with high surface quality, which prevents rapid corrosion of biomedical applications.
文摘The effect of revend con ede and length of Plug on nstalnt nd elimination of distortion of internal spi-ral ribs is theoretically analysed. Metheds of the Plug in rifled tubes drawing and a uniform-Pitch Plug with a certainreversed cone angle is proposed for drawing rifled tubes.
基金Project (50975235) supported by the National Natural Science Foundation of ChinaProject (B08040) supported by the 111 Project
文摘In order to study the effects of the process parameters on springback and section deformation, a sensitivity analysis model was established based on the combination use of the multi-parameter sensitivity analysis method and the springback/section deformation prediction finite element model, and by using this model the sensitivities of the springback and the section deformation to process parameters were analyzed and compared. The results show that the most sensitive process conditions for springback angle are the boost speed and the pressure of pressure die, and the most sensitive process condition for section deformation is the number of cores. When the clamp force, the boost speed and the pressure of pressure die are utilized to control section deformation, the effect of these process parameters on springback should be considered. When the process parameters are mainly used to control springback, the effect of these process parameters on the section deformation should be always considered.
文摘Teaching and learning-related activities have embraced digital technology especially,with the current global pandemic restrictions pervaded during the last two years.On the other hand,most of the academic and professional presentations are conducted using online platforms.But the presenter-audience interaction is hindered to a certain extent in an online case in contrary to face-to-face where real-time writing is beneficial when sketching is involved.The use of digital pens and pads is a solution for such instances,though the cost of acquiring such hardware is high.Economical solutions are essential as affordability is concerned.In this study,a real-time user-friendly,innovative drawing system is developed to address the issues related to the problems confronted with online presentations.This paper presents the development of an algorithm using Hand Landmark Detection,which replaces chalks,markers and regular ballpoint pens used in conventional communication and presentation,with online platforms.The proposed application in this study is acquired by Python and OpenCV libraries.The letters or the sketches drawn in the air were taken straight to the computer screen by this algorithm.The proposed algorithm continuously identifies the Hand Landmark using the images fed by the web camera,and text or drawing patterns are displayed on the screen according to the movements made by Hand Landmark on the image space.The developed user interface is also user-friendly.Hence the communication of letters and sketches were enabled.Although the concept has been developed and tested,with further research the versatility and accuracy of communication can be enhanced.
文摘Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved, and the friction between metal and tool was decreased. Corrosion strip layers and photo-elastic coatings methods were adopted in the experiment for measuring residual stress, and the residual stresses in the drawn tube with 3-roll dies are reduced.
