Recent new technology developments were presented in the field of industrial bending operations,including flexible stretch forming and 3D rotary stretch forming.Attempts were made to give an overview of different mech...Recent new technology developments were presented in the field of industrial bending operations,including flexible stretch forming and 3D rotary stretch forming.Attempts were made to give an overview of different mechanisms that influence dimensional accuracy,including local cross-sectional deformations such as suck-in and volume conservation effects,along with global deformations such as springback.An analytical model was developed to determine the particular influence of different material,geometry and process parameters on dimensional variability of bent components.The results were discussed in terms of overall process capability(Cp) and associated process windows.The results show that different governing mechanisms prevail in various bending operations,meaning that attention has to be placed on controlling those process parameters that really are important to part quality in each specific case.Several strategies may be defined for reducing variability.One alternative may be to design more robust process and tool technology that reduce the effect of upstream parameters on dimensional variability of the formed part.The results show that optimal tool design and technology may in specific cases improve the dimensional accuracy of a formed part.Based on the findings discussed herein,it is concluded that advances in industrial bending operations require focus on improving the understanding of mechanical mechanisms,including models and parameter development,new technology developments,including process,tool,measurement and control capabilities,and process discipline at the shop floor,combined with a basic philosophy of controlling process parameters rather than part attributes.展开更多
To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die ...To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.展开更多
Objective: To observe the accuracy of femoral preparation and the position of the cementless prosthesis in femoral cavity, and to compare the results between the computer-assisted surgical group (CASPAR) and the conve...Objective: To observe the accuracy of femoral preparation and the position of the cementless prosthesis in femoral cavity, and to compare the results between the computer-assisted surgical group (CASPAR) and the conventional group. Methods: Ten femoral components were implanted either manually or by CASPAR in cadaver femurs. The specimens were cut to 3mm thick slices. Microradiograms of every slice were sent to a computer for analysis with special software (IDL). The gaps and the medullary cavities between component and bone, the direct bone contact area of the implant surface, the gap width and the percentage of gap and bone contact area were measured in every slice. Results: In the proximal implant coated with HA of the CASPAR group, the average percentage of bone contact reached 93.2% (ranging from 87.6% to 99.7%); the average gap percentage was 2.9% (ranging from 0.3% to 7.8%); the maximum gap width was 0.81mm and the average gap width was only 0.20mm. While in the conventional group, the average percentage of bone contact reached 60.1% (ranging from 49.2% to 70.4%); the average gap percentage was 32.8% (ranging from 25.1% to 39.9%); the maximum gap width was 2.97mm and the average gap width was 0.77mm. The average gap around the implant in the CASPAR group was only 9% of that in the manual group; the maximum and average gap widths were only about 26% of those in the manual group. On the other hand, the CASPAR group showed 33% higher bone contact than the manual group. Conclusion: With the use of robotics-assisted system, significant progress can be achieved for femoral preparation in total hip arthroplasty.展开更多
This paper presents the comprehensive results of landing site topographic mapping and rover localization in Chang’e-3 mission.High-precision topographic products of the landing site with extremely high resolutions(up...This paper presents the comprehensive results of landing site topographic mapping and rover localization in Chang’e-3 mission.High-precision topographic products of the landing site with extremely high resolutions(up to 0.05 m)were generated from descent images and registered to CE-2 DOM.Local DEM and DOM with 0.02 m resolution were produced routinely at each waypoint along the rover traverse.The lander location was determined to be(19.51256°W,44.11884°N,-2615.451 m)using a method of DOM matching.In order to reduce error accumulation caused by wheel slippage and IMU drift in dead reckoning,cross-site visual localization and DOM matching localization methods were developed to localize the rover at waypoints;the overall traveled distance from the lander is 114.8 m from cross-site visual localization and 111.2 m from DOM matching localization.The latter is of highest accuracy and has been verified using a LRO NAC image where the rover trajeactory is directly identifiable.During CE-3 mission operations,landing site mapping and rover localization products including DEMs and DOMs,traverse maps,vertical traverse profiles were generated timely to support teleoperation tasks such as obstacle avoidance and rover path planning.展开更多
文摘Recent new technology developments were presented in the field of industrial bending operations,including flexible stretch forming and 3D rotary stretch forming.Attempts were made to give an overview of different mechanisms that influence dimensional accuracy,including local cross-sectional deformations such as suck-in and volume conservation effects,along with global deformations such as springback.An analytical model was developed to determine the particular influence of different material,geometry and process parameters on dimensional variability of bent components.The results were discussed in terms of overall process capability(Cp) and associated process windows.The results show that different governing mechanisms prevail in various bending operations,meaning that attention has to be placed on controlling those process parameters that really are important to part quality in each specific case.Several strategies may be defined for reducing variability.One alternative may be to design more robust process and tool technology that reduce the effect of upstream parameters on dimensional variability of the formed part.The results show that optimal tool design and technology may in specific cases improve the dimensional accuracy of a formed part.Based on the findings discussed herein,it is concluded that advances in industrial bending operations require focus on improving the understanding of mechanical mechanisms,including models and parameter development,new technology developments,including process,tool,measurement and control capabilities,and process discipline at the shop floor,combined with a basic philosophy of controlling process parameters rather than part attributes.
基金Project(51375042)supported by the National Natural Science Foundation of ChinaProject supported by Beijing Laboratory of Modern Transport Metal Materials and Processing Technology,China
文摘To reduce the difficulty of material filling into the top region of tooth in hot precision forging of gears using the alternative die designs, relief-cavity designs in different sizes were performed on the top of die tooth. The influences of the conventional process and relief-cavity designs on corner filling, workpiece stress, die stress, forming load and material utilization were examined. Finite element simulation for tooth forming, die stress and forming load using the four designs was performed. The material utilization was further considered, and the optimal design was determined. The tooth form and forming load in forging trials ensured the validity of FE simulation. Tooth accuracy was inspected by video measuring machine(VMM), which shows the hot forged accuracy achieves the level of rough machining of gear teeth. The effects of friction on mode of metal flow and strain distribution were also discussed.
文摘Objective: To observe the accuracy of femoral preparation and the position of the cementless prosthesis in femoral cavity, and to compare the results between the computer-assisted surgical group (CASPAR) and the conventional group. Methods: Ten femoral components were implanted either manually or by CASPAR in cadaver femurs. The specimens were cut to 3mm thick slices. Microradiograms of every slice were sent to a computer for analysis with special software (IDL). The gaps and the medullary cavities between component and bone, the direct bone contact area of the implant surface, the gap width and the percentage of gap and bone contact area were measured in every slice. Results: In the proximal implant coated with HA of the CASPAR group, the average percentage of bone contact reached 93.2% (ranging from 87.6% to 99.7%); the average gap percentage was 2.9% (ranging from 0.3% to 7.8%); the maximum gap width was 0.81mm and the average gap width was only 0.20mm. While in the conventional group, the average percentage of bone contact reached 60.1% (ranging from 49.2% to 70.4%); the average gap percentage was 32.8% (ranging from 25.1% to 39.9%); the maximum gap width was 2.97mm and the average gap width was 0.77mm. The average gap around the implant in the CASPAR group was only 9% of that in the manual group; the maximum and average gap widths were only about 26% of those in the manual group. On the other hand, the CASPAR group showed 33% higher bone contact than the manual group. Conclusion: With the use of robotics-assisted system, significant progress can be achieved for femoral preparation in total hip arthroplasty.
基金supported by the National Natural Science Foundation of China(Grant Nos.41201480,41171355 and 41301528)the Key Research Program of the Chinese Academy of Sciences(Grant No.KGZD-EW-603)
文摘This paper presents the comprehensive results of landing site topographic mapping and rover localization in Chang’e-3 mission.High-precision topographic products of the landing site with extremely high resolutions(up to 0.05 m)were generated from descent images and registered to CE-2 DOM.Local DEM and DOM with 0.02 m resolution were produced routinely at each waypoint along the rover traverse.The lander location was determined to be(19.51256°W,44.11884°N,-2615.451 m)using a method of DOM matching.In order to reduce error accumulation caused by wheel slippage and IMU drift in dead reckoning,cross-site visual localization and DOM matching localization methods were developed to localize the rover at waypoints;the overall traveled distance from the lander is 114.8 m from cross-site visual localization and 111.2 m from DOM matching localization.The latter is of highest accuracy and has been verified using a LRO NAC image where the rover trajeactory is directly identifiable.During CE-3 mission operations,landing site mapping and rover localization products including DEMs and DOMs,traverse maps,vertical traverse profiles were generated timely to support teleoperation tasks such as obstacle avoidance and rover path planning.
