Transactions of Nanjing University of Aeronautics & Astronautics
Volume 32,Issue 6,2015 Table of Contents
2015, 32(6):585-590.
Abstract:
Deformation of a simple single piezoelectric actuator is usually quite small. A ringshaped piezoelectric actuator with large piezoelectrically generated displacement was proposed. The thickness of the actuator was 1 mm, and the inner and outer diameters were 4 mm and 40 mm, respectively. The ringshaped actuator was made of BiScO3PbTiO3 (BSPT) ceramic and polarized in radial direction. An electric field was applied to thickness direction and a large shearbending deformation emerged. Then RayleighRitz method and Bessel functions were adopted to analyze the shearbending deformation. Results show that under an electric field of 7.5 kV/cm, the maximum displacement at the inner edge of the actuator reached 5.07 μm, which agreed well with the corresponding experimental results.
Deformation of a simple single piezoelectric actuator is usually quite small. A ringshaped piezoelectric actuator with large piezoelectrically generated displacement was proposed. The thickness of the actuator was 1 mm, and the inner and outer diameters were 4 mm and 40 mm, respectively. The ringshaped actuator was made of BiScO3PbTiO3 (BSPT) ceramic and polarized in radial direction. An electric field was applied to thickness direction and a large shearbending deformation emerged. Then RayleighRitz method and Bessel functions were adopted to analyze the shearbending deformation. Results show that under an electric field of 7.5 kV/cm, the maximum displacement at the inner edge of the actuator reached 5.07 μm, which agreed well with the corresponding experimental results.
2015, 32(6):591-599.
Abstract:
Network topology inference is one of the important applications of network tomography. Traditional network topology inference may impact network normal operation due to its generation of huge data traffic. A unicast network topology inference is proposed to use time to live (TTL) for layering and classify nodes layer by layer based on the similarity of node pairs. Finally,the method infers logical network topology effectively with selfadaptive combination of previous results. Simulation results show that the proposed method holds a high accuracy of topology inference while decreasing network measuring flow, thus improves measurement efficiency.
Network topology inference is one of the important applications of network tomography. Traditional network topology inference may impact network normal operation due to its generation of huge data traffic. A unicast network topology inference is proposed to use time to live (TTL) for layering and classify nodes layer by layer based on the similarity of node pairs. Finally,the method infers logical network topology effectively with selfadaptive combination of previous results. Simulation results show that the proposed method holds a high accuracy of topology inference while decreasing network measuring flow, thus improves measurement efficiency.
2015, 32(6):600-609.
Abstract:
A fault detection method based on incremental locally linear embedding (LLE) is presented to improve fault detecting accuracy for satellites with telemetry data. Since conventional LLE algorithm cannot handle incremental learning, an incremental LLE method is proposed to acquire lowdimensional feature embedded in highdimensional space. Then, telemetry data of Satellite TXI are analyzed. Therefore, fault detection are performed by analyzing feature information extracted from the telemetry data with the statistical indexes T2 and squared prediction error(SPE) and SPE. Simulation results verify the fault detection scheme.
A fault detection method based on incremental locally linear embedding (LLE) is presented to improve fault detecting accuracy for satellites with telemetry data. Since conventional LLE algorithm cannot handle incremental learning, an incremental LLE method is proposed to acquire lowdimensional feature embedded in highdimensional space. Then, telemetry data of Satellite TXI are analyzed. Therefore, fault detection are performed by analyzing feature information extracted from the telemetry data with the statistical indexes T2 and squared prediction error(SPE) and SPE. Simulation results verify the fault detection scheme.
2015, 32(6):610-622.
Abstract:
There exists inletengine match conflict between high and low speeds for a nonadjustable bump inlet. A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area. The FEM model of the bistable surface is established with hinged constraint, and the bistability condition and structural transition process are investigated in detail. Moreover, the effects of loading method, loading position and structural parameters on critical driving force, input energy and structural strain are studied. Finally, the influences of an elastic boundary condition on the structural bistability are discussed. The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snapthrough phenomena during transition which are related to the loading position and structural parameters. Therefore, suitable loading position and structural material could reduce input energy and meet the demand of structural strain.
There exists inletengine match conflict between high and low speeds for a nonadjustable bump inlet. A scheme of using a bistable bump surface at the throat region of the inlet is proposed to adjust the throat area. The FEM model of the bistable surface is established with hinged constraint, and the bistability condition and structural transition process are investigated in detail. Moreover, the effects of loading method, loading position and structural parameters on critical driving force, input energy and structural strain are studied. Finally, the influences of an elastic boundary condition on the structural bistability are discussed. The results show that the bistability of the adjustable bump surface requires a certain boundary constraint and geometric parameter combination,and that there are local and overall snapthrough phenomena during transition which are related to the loading position and structural parameters. Therefore, suitable loading position and structural material could reduce input energy and meet the demand of structural strain.
2015, 32(6):623-630.
Abstract:
The effect of tipblade cutting on the performance of a large scale axial fan was investigated using computational fluid dynamics (CFD) methods. Experiments verified the numerical simulations. The original fan was compared with the one with tipcutting in terms of dimensionless characteristic and aerodynamic performance in tip region under the conditions of the maximum efficiency point and nearstall point. The results showed that double leakage flow occurred in tip clearance at maximum efficiency point and spillage of leakage flow from leading edge occurred in tipblade region at nearstall point for the both two fans; and that tipcutting with 6% of blade height could reduce the intensity of tipleakage vortex and increase flow capacity in tip blade region, and hold the stall margin almost the same as the original fan. The maximum efficiency of the fan with tipcutting was improved by 1%, and the ability of total pressure rising was obviously greater than the original fan.
The effect of tipblade cutting on the performance of a large scale axial fan was investigated using computational fluid dynamics (CFD) methods. Experiments verified the numerical simulations. The original fan was compared with the one with tipcutting in terms of dimensionless characteristic and aerodynamic performance in tip region under the conditions of the maximum efficiency point and nearstall point. The results showed that double leakage flow occurred in tip clearance at maximum efficiency point and spillage of leakage flow from leading edge occurred in tipblade region at nearstall point for the both two fans; and that tipcutting with 6% of blade height could reduce the intensity of tipleakage vortex and increase flow capacity in tip blade region, and hold the stall margin almost the same as the original fan. The maximum efficiency of the fan with tipcutting was improved by 1%, and the ability of total pressure rising was obviously greater than the original fan.
2015, 32(6):631-638.
Abstract:
Prepreg stickiness is the adhesion between prepregs or between a prepreg and a mold in layup process. It is critical for automated fiber placement, because the stickiness should be small for smooth transport, as well as large enough on the laying surface for a good placement performance. To ensure prepreg stickiness always being in the optimum laying window, placement temperature should be changed according to the laying speed. In our work, the relationship between laying speed and emissive power of heating lamp was studied. The heat transfer process between heating lamp and laying surface was analyzed and the control equation of dynamic temperature was derived. Finally, the infrared heating system was built and its effectiveness was verified based on placement experiment.
Prepreg stickiness is the adhesion between prepregs or between a prepreg and a mold in layup process. It is critical for automated fiber placement, because the stickiness should be small for smooth transport, as well as large enough on the laying surface for a good placement performance. To ensure prepreg stickiness always being in the optimum laying window, placement temperature should be changed according to the laying speed. In our work, the relationship between laying speed and emissive power of heating lamp was studied. The heat transfer process between heating lamp and laying surface was analyzed and the control equation of dynamic temperature was derived. Finally, the infrared heating system was built and its effectiveness was verified based on placement experiment.
2015, 32(6):639-645.
Abstract:
The precise microscopic feature of carboncarbon(C/C) composites is essential for an accurate prediction of their mechanical behavior. After fabrication, actual microscopic feature differs from simple ideal spatial model. Microcomputedtomography(CT) scan can well describe internal microstructures of composites. Therefore, a reconstructed model is developed based on mircoCT, by a series of prodcedures including extracting components, generating new binary images and establishing a finite element (FE) model. Compared with the model designed by reconstructed commercial software MIMICS, the presented reconstructed FE model is superior in terms of high mesh quality and controllable mesh quantity. The precision of the model is verified by experiment.
The precise microscopic feature of carboncarbon(C/C) composites is essential for an accurate prediction of their mechanical behavior. After fabrication, actual microscopic feature differs from simple ideal spatial model. Microcomputedtomography(CT) scan can well describe internal microstructures of composites. Therefore, a reconstructed model is developed based on mircoCT, by a series of prodcedures including extracting components, generating new binary images and establishing a finite element (FE) model. Compared with the model designed by reconstructed commercial software MIMICS, the presented reconstructed FE model is superior in terms of high mesh quality and controllable mesh quantity. The precision of the model is verified by experiment.
8 Prediction of Compressive and Shear Moduli of Xcor Sandwich Structures for Aeronautic Engineering
2015, 32(6):646-653.
Abstract:
The socalled ″Xcor sandwich structure″ is a highly promising novel material as an alternative to honeycomb used in aircraft. Although much work has been conducted on the performance of the Xcor sandwich structure, the gap is still hardly bridged between experimental results and theoretical analyses. Therefore, a method has been innovated to establish semiempirical formula for the prediction of compressive and shear moduli of Xcor sandwich structure composites, by combining theoretical analyses and experimental data. In addition, a prediction software was first developed based on the proposed method, of which the accuracy was verified through confirmatory experiments. This software can offer a direct reference or guide for engineers in structural designing.
The socalled ″Xcor sandwich structure″ is a highly promising novel material as an alternative to honeycomb used in aircraft. Although much work has been conducted on the performance of the Xcor sandwich structure, the gap is still hardly bridged between experimental results and theoretical analyses. Therefore, a method has been innovated to establish semiempirical formula for the prediction of compressive and shear moduli of Xcor sandwich structure composites, by combining theoretical analyses and experimental data. In addition, a prediction software was first developed based on the proposed method, of which the accuracy was verified through confirmatory experiments. This software can offer a direct reference or guide for engineers in structural designing.
2015, 32(6):654-664.
Abstract:
In order to improve safety, economy efficiency and design automation degree of air route in terminal airspace, Threedimensional(3D) planning of routes network is investigated. A waypoint probability search method is proposed to optimize individual flight path. Through updating horizontal pheromones by negative feedback factors, an antcolony algorithm of path searching in 3D terminal airspace is implemented. The principle of optimization sequence of arrival and departure routes is analyzed. Each route is optimized successively, and the overall optimization of the whole route network is finally achieved. A case study shows that it takes about 63 s to optimize 8 arrival and departure routes, and the operation efficiency can be significantly improved with desirable safety and economy.
In order to improve safety, economy efficiency and design automation degree of air route in terminal airspace, Threedimensional(3D) planning of routes network is investigated. A waypoint probability search method is proposed to optimize individual flight path. Through updating horizontal pheromones by negative feedback factors, an antcolony algorithm of path searching in 3D terminal airspace is implemented. The principle of optimization sequence of arrival and departure routes is analyzed. Each route is optimized successively, and the overall optimization of the whole route network is finally achieved. A case study shows that it takes about 63 s to optimize 8 arrival and departure routes, and the operation efficiency can be significantly improved with desirable safety and economy.
2015, 32(6):665-673.
Abstract:
To improve stiffness and workspace of tripod machine tools, a device called tripod machine tool was proposed with five degrees of freedom. First, the structure and pose description of the tripod machine tool were introduced, and then its backward and forward kinematics models were analyzed. To identify parameters of the tripod machine tool, a parameter identification method based on an errorsensitive analysis was presented.Then geometrical structural identification model was deduced by establishing the pose relative error model at two different points of the tripod machine tool. The method employed a sensitivity matrix by using a difference operator to explain pose changes of the tripod machine tool with respect to its main geometrical structural parameters. Finally, the position error of a tripod machine tool was reduced from 1.74 mm to 0.44 mm. Therefore, the proposed identification method was verified to be effectiv e and feasible.
To improve stiffness and workspace of tripod machine tools, a device called tripod machine tool was proposed with five degrees of freedom. First, the structure and pose description of the tripod machine tool were introduced, and then its backward and forward kinematics models were analyzed. To identify parameters of the tripod machine tool, a parameter identification method based on an errorsensitive analysis was presented.Then geometrical structural identification model was deduced by establishing the pose relative error model at two different points of the tripod machine tool. The method employed a sensitivity matrix by using a difference operator to explain pose changes of the tripod machine tool with respect to its main geometrical structural parameters. Finally, the position error of a tripod machine tool was reduced from 1.74 mm to 0.44 mm. Therefore, the proposed identification method was verified to be effectiv e and feasible.
2015, 32(6):674-680.
Abstract:
Boron doped diamond (BDD) performs well in electrochemical oxidatio n for organic pollutants thanks to its wide electrochemical window and superior chemical stability. We presented a method to obtain welladherent largescale BDD/Nb electrode by the modified hot filament chemical vapor deposition system (HFCVD). SiC particles were sand blasted to enhance the adhesion of BDD coating. The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides. The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition. The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope (SEM) techniques. Scratch test was used to investigate the adhesion of BDD films. The electrochemical performances were measured by cyclic voltammetry test. The BDD electrode at the B/C ratio of 2 000×１０－６ held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced th e adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.
Boron doped diamond (BDD) performs well in electrochemical oxidatio n for organic pollutants thanks to its wide electrochemical window and superior chemical stability. We presented a method to obtain welladherent largescale BDD/Nb electrode by the modified hot filament chemical vapor deposition system (HFCVD). SiC particles were sand blasted to enhance the adhesion of BDD coating. The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides. The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition. The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope (SEM) techniques. Scratch test was used to investigate the adhesion of BDD films. The electrochemical performances were measured by cyclic voltammetry test. The BDD electrode at the B/C ratio of 2 000×１０－６ held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced th e adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.
2015, 32(6):681-686.
Abstract:
When shaped charge penetrats into concrete, crater diameter must meet certain requirements. By using theories of shaped jet formation and crater diameter growth during jet penetrating concrete, we revealed the thresholds of the velocity and diameter of jet head, and therefore obtained the related structure parameters of top liner, so that shaped charge structure was developed. We built a 60 mm copper liner and a 142 mm Tialloy liner which followed the rules of 0.6 cal and 0.7 cal incrater diameter. respectively. Xray experiment and penetration test results showed that the parameters of jet head were consistent with the results of theoretical analysis. The incrater diameter of 60 mm shaped charge reached 36 mm, and the 142 mm one reached 100 mm. They both met the design requirements.
When shaped charge penetrats into concrete, crater diameter must meet certain requirements. By using theories of shaped jet formation and crater diameter growth during jet penetrating concrete, we revealed the thresholds of the velocity and diameter of jet head, and therefore obtained the related structure parameters of top liner, so that shaped charge structure was developed. We built a 60 mm copper liner and a 142 mm Tialloy liner which followed the rules of 0.6 cal and 0.7 cal incrater diameter. respectively. Xray experiment and penetration test results showed that the parameters of jet head were consistent with the results of theoretical analysis. The incrater diameter of 60 mm shaped charge reached 36 mm, and the 142 mm one reached 100 mm. They both met the design requirements.
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