Transactions of Nanjing University of Aeronautics & Astronautics
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2020, 37(3):353-359.
DOI: 10.16356/j.1005-1120.2020.03.001
Abstract:
The aramid fiber-reinforced composites (AFRC) can increase the durability of corresponding applications such as aerospace, automobile and other large structural parts, due to the improvement in hardness, heat build-up, wear properties and green environmental protection. However, because of its complex multiphase structure and unique heterogeneity and anisotropy, the poor compression fatigue resistance and the incident surface fibrillation are inevitable. To improve the assembly precision of AFRC, mechanical processing is necessary to meet the dimensional accuracy. This paper focuses on the influence of contour milling parameters on delamination defects during milling of AFRC laminates. A series of milling experiments are conducted and two different kinds of delamination defects including tearing delamination and uncut-off delamination are investigated. A computing method and model based on brittle fracture for the two different types of delamination are established. The results can be used for explaining the mechanism and regularity of delamination defects. The control strategy of delamination defects and evaluation method of finished surface integrity are further discussed. The results are meaningful to optimize cutting parameters, and provide a clear understanding of surface defects control.
The aramid fiber-reinforced composites (AFRC) can increase the durability of corresponding applications such as aerospace, automobile and other large structural parts, due to the improvement in hardness, heat build-up, wear properties and green environmental protection. However, because of its complex multiphase structure and unique heterogeneity and anisotropy, the poor compression fatigue resistance and the incident surface fibrillation are inevitable. To improve the assembly precision of AFRC, mechanical processing is necessary to meet the dimensional accuracy. This paper focuses on the influence of contour milling parameters on delamination defects during milling of AFRC laminates. A series of milling experiments are conducted and two different kinds of delamination defects including tearing delamination and uncut-off delamination are investigated. A computing method and model based on brittle fracture for the two different types of delamination are established. The results can be used for explaining the mechanism and regularity of delamination defects. The control strategy of delamination defects and evaluation method of finished surface integrity are further discussed. The results are meaningful to optimize cutting parameters, and provide a clear understanding of surface defects control.
2014, 31(1):1-15.
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A lattice Boltzmann flux solver (LBFS) is presented for simulation of fluid flows. Like the conventional computational fluid dynamics (CFD) solvers, the new solver also applies the finite volume method to discretize the governing differential equations, but the numerical flux at the cell interface is not evaluated by the smooth function approximation or Riemann solvers. Instead, it is evaluated from local solution of lattice Boltzmann equation (LBE) at cell interface. Two versions of LBFS are presented in this paper. One is to locally apply one dimensional compressible lattice Boltzmann (LB) model along the normal direction to the cell interface for simulation of compressible inviscid flows with shock waves. The other is to locally apply multi dimensional LB model at cell interface for simulation of incompressible viscous and inviscid flows. The present solver removes the drawbacks of conventional lattice Boltzmann method (LBM) such as limitation to uniform mesh, tie-up of mesh spacing and time interval, limitation to viscous flows. Numerical examples show that the present solver can be well applied to simulate fluid flows with non-uniform mesh and curved boundary.
A lattice Boltzmann flux solver (LBFS) is presented for simulation of fluid flows. Like the conventional computational fluid dynamics (CFD) solvers, the new solver also applies the finite volume method to discretize the governing differential equations, but the numerical flux at the cell interface is not evaluated by the smooth function approximation or Riemann solvers. Instead, it is evaluated from local solution of lattice Boltzmann equation (LBE) at cell interface. Two versions of LBFS are presented in this paper. One is to locally apply one dimensional compressible lattice Boltzmann (LB) model along the normal direction to the cell interface for simulation of compressible inviscid flows with shock waves. The other is to locally apply multi dimensional LB model at cell interface for simulation of incompressible viscous and inviscid flows. The present solver removes the drawbacks of conventional lattice Boltzmann method (LBM) such as limitation to uniform mesh, tie-up of mesh spacing and time interval, limitation to viscous flows. Numerical examples show that the present solver can be well applied to simulate fluid flows with non-uniform mesh and curved boundary.
2010(4).
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A new orbit transfer method is presented by combining the genetic algorit h m (GA) with the refined Qlaw method. Considering the energy consumptio n , the relative thrust efficiency is introduced as a threshold deciding whether t o thrust or coast. GA is used to achieve the global timeoptimal orbit trans f er. The trajectory optimization problem is transformed into the constraint para met er optimization problem, thus the nonlinear twopoint boundary value problem is avoided. The refined Qlaw method integrated with the fuzzy logic control is adopte d for t he end course, the vibration is avoided and the high precision is achieved. The numerical simulation of satellite orbit transfer is implemented. Result s show that the new method can achieve the timeoptimal orbit transfer and t he low energy consumption, thus improving the transfer precision.
A new orbit transfer method is presented by combining the genetic algorit h m (GA) with the refined Qlaw method. Considering the energy consumptio n , the relative thrust efficiency is introduced as a threshold deciding whether t o thrust or coast. GA is used to achieve the global timeoptimal orbit trans f er. The trajectory optimization problem is transformed into the constraint para met er optimization problem, thus the nonlinear twopoint boundary value problem is avoided. The refined Qlaw method integrated with the fuzzy logic control is adopte d for t he end course, the vibration is avoided and the high precision is achieved. The numerical simulation of satellite orbit transfer is implemented. Result s show that the new method can achieve the timeoptimal orbit transfer and t he low energy consumption, thus improving the transfer precision.
2011, 28(2):152-156.
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2015, 32(1):1-8.
DOI: 10.16356/j.1005-1120.2015.01.001
Abstract:
To date unmanned aerial system (UAS) technologies have attracted more and more attention from countries in the world. Unmanned aerial vehicles (UAVs) play an important role in reconnaissance, surveillance, and target tracking within military and civil fields. Here one briefly introduces the development of UAVs, and reviews its various subsystems including autopilot, ground station, mission planning and management subsystem, navigation system and so on. Furthermore, an overview is provided for advanced design methods of UAVs control system, including the linear feedback control, adaptive and nonlinear control, and intelligent control techniques. Finally, the future of UAVs flight control techniques is forecasted.
To date unmanned aerial system (UAS) technologies have attracted more and more attention from countries in the world. Unmanned aerial vehicles (UAVs) play an important role in reconnaissance, surveillance, and target tracking within military and civil fields. Here one briefly introduces the development of UAVs, and reviews its various subsystems including autopilot, ground station, mission planning and management subsystem, navigation system and so on. Furthermore, an overview is provided for advanced design methods of UAVs control system, including the linear feedback control, adaptive and nonlinear control, and intelligent control techniques. Finally, the future of UAVs flight control techniques is forecasted.
2010(4).
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The effect of inhaled nanoTiO2 on lung histology and serum biochemic al indexes is evaluated in healthy and adult Kunming mice (eight in each group) after exposure to TiO2 aerosols (1 500 mg／m3) in a sealed chamber. Ano ther e ight mice are exposed to indoor air to be served as a control group. Lung tissue and blood are collected after euthanizing the animals. The results show that la c tate dehydrogenase (LDH) activity increases in all experimental groups. Alanine aminotransferase(ALT) activity and blood urea nitrogen (BUN) levels are increase d in the group exposed to TiO2 aerosols for 28 d, and creatinine(Cr) level s are increased in 14 d and 28 d samples (P<005). No obvious changes are observed in other serum indexes. Lungs of mice exposed to 28 d exposure show significant but moderate increase in pulmonary inflammatio n, and many TiO2 particles are found in the interstitium of pulmonary alve oli.
The effect of inhaled nanoTiO2 on lung histology and serum biochemic al indexes is evaluated in healthy and adult Kunming mice (eight in each group) after exposure to TiO2 aerosols (1 500 mg／m3) in a sealed chamber. Ano ther e ight mice are exposed to indoor air to be served as a control group. Lung tissue and blood are collected after euthanizing the animals. The results show that la c tate dehydrogenase (LDH) activity increases in all experimental groups. Alanine aminotransferase(ALT) activity and blood urea nitrogen (BUN) levels are increase d in the group exposed to TiO2 aerosols for 28 d, and creatinine(Cr) level s are increased in 14 d and 28 d samples (P<005). No obvious changes are observed in other serum indexes. Lungs of mice exposed to 28 d exposure show significant but moderate increase in pulmonary inflammatio n, and many TiO2 particles are found in the interstitium of pulmonary alve oli.
2010(4).
Abstract:
Buildup panels for the commercial aircraft fuselage subjected to the axial com pression load are studied by both experimental and theoretical methods. An integ ral panel is designed with the same overall size and weight as the buildup str ucture, and finite element models (FEMs) of these two panels are established. Ex perimental results of buildup panels agree well with the FEM results with the nonliearity and the large deformation, so FEMs are validated. FEM calculation results of these two panels indicate that the failure mode of the i ntegral panel is different from that of the buildup panel, and the failure loa d increases by 184％ up to postbuckling. Furthermore, the integral structure is optimized by using the multiisland genetic algorithm and the sequential quadratic progr amming. Compared with the initial design, the optimal weight is reduced by 87 ％ and the strength is unchanged.
Buildup panels for the commercial aircraft fuselage subjected to the axial com pression load are studied by both experimental and theoretical methods. An integ ral panel is designed with the same overall size and weight as the buildup str ucture, and finite element models (FEMs) of these two panels are established. Ex perimental results of buildup panels agree well with the FEM results with the nonliearity and the large deformation, so FEMs are validated. FEM calculation results of these two panels indicate that the failure mode of the i ntegral panel is different from that of the buildup panel, and the failure loa d increases by 184％ up to postbuckling. Furthermore, the integral structure is optimized by using the multiisland genetic algorithm and the sequential quadratic progr amming. Compared with the initial design, the optimal weight is reduced by 87 ％ and the strength is unchanged.
2011, 28(2):192-198.
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2010(4).
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To solve aircraft arrival sequencing and scheduling problems, and imp rove the typical predatory search algorithm(PSA), an innovative PSA is developed . The new PSA uses variable constraints of local search and global search to avo id falling into local optimal solutions and the degeneration of solutions. To te st t he performance of new PSA, a case study with ten arriving flights and two runway s is performed. Test results show that the new PSA performs much better than typ ical PSA and genetic algorithm(GA) in the aspects of the rate of gaining optimal solutions and the computational time.
To solve aircraft arrival sequencing and scheduling problems, and imp rove the typical predatory search algorithm(PSA), an innovative PSA is developed . The new PSA uses variable constraints of local search and global search to avo id falling into local optimal solutions and the degeneration of solutions. To te st t he performance of new PSA, a case study with ten arriving flights and two runway s is performed. Test results show that the new PSA performs much better than typ ical PSA and genetic algorithm(GA) in the aspects of the rate of gaining optimal solutions and the computational time.
2010(4).
Abstract:
The network on chip (NoC) is used as a solution for the communication p roblems in a complex system on chip (SoC) design. To further enhance performance s, the NoC architectures, a high level modeling and an evaluat ion method based on OPNET are proposed to analyze their performances on differ ent injectio n rates and traffic patterns. Simulation results for general NoC in terms of the average latency and the throughput are analyzed and used as a guideline to make appropriate choices for a given application. Finally, a MPEG4 decoder is mapped on different NoC architectures. Results prove the effectiveness of the evalua tion method.
The network on chip (NoC) is used as a solution for the communication p roblems in a complex system on chip (SoC) design. To further enhance performance s, the NoC architectures, a high level modeling and an evaluat ion method based on OPNET are proposed to analyze their performances on differ ent injectio n rates and traffic patterns. Simulation results for general NoC in terms of the average latency and the throughput are analyzed and used as a guideline to make appropriate choices for a given application. Finally, a MPEG4 decoder is mapped on different NoC architectures. Results prove the effectiveness of the evalua tion method.
2011, 28(2):169-175.
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2011, 28(2):163-168.
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2011, 28(3):240-245.
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2011, 28(1):1-11.
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2011, 28(3):294-299.
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2011, 28(1):12-22.
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2010(4).
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A claylike conductive material comprising polyaniline (PANI)acetylen e black particles is fabricated as a hole conductor for dye sensitiz ed solar cell (DSSC). The results show that the introduction of acetylene black into the polymer electrolyte improves the photovoltaic behavior of solidstate DSSC, owing to the increase of the hole mobility of PANI electroly t e, the improvement of the wetting quality of the composite electrolyte, and the reinforcement of interface contact between electrode and the electrolyte. Final ly, the overall energy conversion efficiency of DSSC with PANI50％(in weight) a cetylene black electrolyte is 48％ of that of liquid DSSC. Therefore, the PANI a cetylene black composition is a credible alternative to hole conductor in ap plication of solid DSSC.
A claylike conductive material comprising polyaniline (PANI)acetylen e black particles is fabricated as a hole conductor for dye sensitiz ed solar cell (DSSC). The results show that the introduction of acetylene black into the polymer electrolyte improves the photovoltaic behavior of solidstate DSSC, owing to the increase of the hole mobility of PANI electroly t e, the improvement of the wetting quality of the composite electrolyte, and the reinforcement of interface contact between electrode and the electrolyte. Final ly, the overall energy conversion efficiency of DSSC with PANI50％(in weight) a cetylene black electrolyte is 48％ of that of liquid DSSC. Therefore, the PANI a cetylene black composition is a credible alternative to hole conductor in ap plication of solid DSSC.
2011, 28(3):276-281.
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2013, 30(3):221-226.
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2013, 30(3):270-275.
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