Regular elemental powders were used in warm flow compaction instead of the expensive micron-sized powders to fabricate cross-shaped parts. Debinding behaviors,sintering properties and shape consistency of the sintered...Regular elemental powders were used in warm flow compaction instead of the expensive micron-sized powders to fabricate cross-shaped parts. Debinding behaviors,sintering properties and shape consistency of the sintered parts were studied. Binder removal was accomplished by heating green compacts at intermediate temperatures with optimal heating rates until the debinding temperature was reached. Results show that by controlling debinding process,complex parts with good shape consistence can be obtained by warm compaction of binder-treated powder. Fine and shiny surface was obtained and no surface defect can be observed for sintered parts debinded at 2 ℃/min,while defect can be observed in sintered parts debinded at 4 ℃/min.展开更多
CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidificati...CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidification simulation and investment casting process. It broke the bottle neck of making metal die. Solid model of complex parts were produced by UGII or other software, then translated into STL(Stereolithography) file, after RP process of SLS(Selective Laser Sintering), wax pattern used in investment casting can be acquired without metal die in short time. These can reduce period and cost greatly of complex superalloy parts development of engine. The key processes of CA investment casting were discussed. The accuracy of model translation should match that of RP system. Choice of RP material, surface polishing, sintering parameter plays important role in RP process. Other processes, like solidification simulating and optimization of gate system were introduced. The conclusion was that complex parts can be produced by CA investment casting with lots of advantages. The accuracy of castings can reach CT5～7,and the smoothness can get Ra3～13 mm. These parts of engines worked well.展开更多
The complex derivative D^α±jβ, with α, β ∈ R＋ is a generalization of the concept of integer derivative, where α = 1,β = 0. Fractional-order electric elements and circuits are becoming more and more attrac...The complex derivative D^α±jβ, with α, β ∈ R＋ is a generalization of the concept of integer derivative, where α = 1,β = 0. Fractional-order electric elements and circuits are becoming more and more attractive. In this paper, the complexorder electric elements concept is proposed for the first time, and the complex-order elements are modeled and analyzed.Some interesting phenomena are found that the real part of the order affects the phase of output signal, and the imaginary part affects the amplitude for both the complex-order capacitor and complex-order memristor. More interesting is that the complex-order capacitor can do well at the time of fitting electrochemistry impedance spectra. The complex-order memristor is also analyzed. The area inside the hysteresis loops increases with the increasing of the imaginary part of the order and decreases with the increasing of the real part. Some complex case of complex-order memristors hysteresis loops are analyzed at last, whose loop has touching points beyond the origin of the coordinate system.展开更多
Due to the advantages of large workspace,low cost and the integrated vision/force sensing,robotic milling has become an important way for machining of complex parts.In recent years,many scholars have studied the probl...Due to the advantages of large workspace,low cost and the integrated vision/force sensing,robotic milling has become an important way for machining of complex parts.In recent years,many scholars have studied the problems existing in the applications of robotic milling,and lots of results have been made in the dynamics,pose planning,deformation control etc.,which provides theoretical guidance for high precision and high efficiency of robotic milling.From the perspective of complex parts robotic milling,this paper focuses on machining process planning and control techniques including the analysis of the robot-workspace,robot trajectory planning,vibration monitoring and control,deformation monitoring and compensation.As well as the principles of these technologies such as robot stiffness characteristics,dynamic characteristics,chatter mechanisms,and deformation mechanisms.The methods and characteristics related to the theory and technology of robotic milling of complex parts are summarized systematically.The latest research progress and achievements in the relevant fields are reviewed.It is hoped that the challenges,strategies and development related to robotic milling could be clarified through the carding work in this paper,so as to promote the application of related theories and technologies in high efficiency and precision intelligent milling with robot for complex parts.展开更多
基金Projects(50574041, 50325516) supported by the National Natural Science Foundation of Chinaprojects(2006Z1-D6081, 06105411) supported by Guangdong Science and Technologyproject (NCET-05-0739) supported by NCET
文摘Regular elemental powders were used in warm flow compaction instead of the expensive micron-sized powders to fabricate cross-shaped parts. Debinding behaviors,sintering properties and shape consistency of the sintered parts were studied. Binder removal was accomplished by heating green compacts at intermediate temperatures with optimal heating rates until the debinding temperature was reached. Results show that by controlling debinding process,complex parts with good shape consistence can be obtained by warm compaction of binder-treated powder. Fine and shiny surface was obtained and no surface defect can be observed for sintered parts debinded at 2 ℃/min,while defect can be observed in sintered parts debinded at 4 ℃/min.
文摘CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidification simulation and investment casting process. It broke the bottle neck of making metal die. Solid model of complex parts were produced by UGII or other software, then translated into STL(Stereolithography) file, after RP process of SLS(Selective Laser Sintering), wax pattern used in investment casting can be acquired without metal die in short time. These can reduce period and cost greatly of complex superalloy parts development of engine. The key processes of CA investment casting were discussed. The accuracy of model translation should match that of RP system. Choice of RP material, surface polishing, sintering parameter plays important role in RP process. Other processes, like solidification simulating and optimization of gate system were introduced. The conclusion was that complex parts can be produced by CA investment casting with lots of advantages. The accuracy of castings can reach CT5～7,and the smoothness can get Ra3～13 mm. These parts of engines worked well.
文摘The complex derivative D^α±jβ, with α, β ∈ R＋ is a generalization of the concept of integer derivative, where α = 1,β = 0. Fractional-order electric elements and circuits are becoming more and more attractive. In this paper, the complexorder electric elements concept is proposed for the first time, and the complex-order elements are modeled and analyzed.Some interesting phenomena are found that the real part of the order affects the phase of output signal, and the imaginary part affects the amplitude for both the complex-order capacitor and complex-order memristor. More interesting is that the complex-order capacitor can do well at the time of fitting electrochemistry impedance spectra. The complex-order memristor is also analyzed. The area inside the hysteresis loops increases with the increasing of the imaginary part of the order and decreases with the increasing of the real part. Some complex case of complex-order memristors hysteresis loops are analyzed at last, whose loop has touching points beyond the origin of the coordinate system.
基金supported by National Science Fund for Distinguished Young Scholars of China(No.51625502)Innovative Group Project of National Natural Science Foundation of China(No.51721092)Innovative Group Project of Hubei Province of China(No.2017CFA003)。
文摘Due to the advantages of large workspace,low cost and the integrated vision/force sensing,robotic milling has become an important way for machining of complex parts.In recent years,many scholars have studied the problems existing in the applications of robotic milling,and lots of results have been made in the dynamics,pose planning,deformation control etc.,which provides theoretical guidance for high precision and high efficiency of robotic milling.From the perspective of complex parts robotic milling,this paper focuses on machining process planning and control techniques including the analysis of the robot-workspace,robot trajectory planning,vibration monitoring and control,deformation monitoring and compensation.As well as the principles of these technologies such as robot stiffness characteristics,dynamic characteristics,chatter mechanisms,and deformation mechanisms.The methods and characteristics related to the theory and technology of robotic milling of complex parts are summarized systematically.The latest research progress and achievements in the relevant fields are reviewed.It is hoped that the challenges,strategies and development related to robotic milling could be clarified through the carding work in this paper,so as to promote the application of related theories and technologies in high efficiency and precision intelligent milling with robot for complex parts.
