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  • 2019 Volume 36 Issue 6
    Published: 27 December 2019
      
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  • Thermal buckling analysis of composite laminated Tmoshenko beam founded in the new modified couple stress theory
    2019, 36(6): 1-8.
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    Based on the new modified couple stress theory, the thermal stability model of micro-scale laminated Tmoshenko beam under mechanical load and thermal load is proposed for the first time. The model only needs to introduce a material scale parameter. According to the principle of virtual work, the governing equations and boundary conditions of the model can be derived. In this paper, the simply supported beam is taken as an example, and the Navier method was used to analyze the thermal stability of the model and calculated the analytical solution. The results show that the model can obviously capture the scale effect. The larger the value of the material scale parameter, the higher the temperature at the critical load of buckling; as the critical temperature increases, the value of the critical mechanical load increases continuously, thereby reflecting the effect of temperature on the critical load of buckling; When the scale parameter is used, the model can be degraded to the macroscopic classical model; when the value of the critical temperature is increased, the value of the buckling critical load under the thermal load is also increased, resulting in a more obvious scale effect.
  • The Modal Analysis of an APU Turbine Rotor Blade
    2019, 36(6): 9-13.
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    SolidWorks was used to simplify the modeling of APU two-stage turbine. The simulation calculation of temperature field and flow field of blade was carried by using CFX software. Thermal analysis was done using Steady State Thermal module by importing the output of temperature field and flow field. The centrifugal force was applied to a turbine blade using Statistic Structure module, and the Heat-fluid-solid?coupling analysis was performed. The first 6 order natural frequencies and modes of APU turbine rotor blades were obtained through the modal analysis of pre-stressed blades. The response surface method was used to optimize the parameterized blade, and a better blade configuration was obtained by taking the maximum equivalent stress, displacement and the maximum displacement of the first and second order modal deformation as the optimization objective.
  • Research on the Influence of Velocity on Flow Flied Structure at Low Reynolds number
    2019, 36(6): 14-21.
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    At low Reynolds number, different wind tunnel test results had great differences for the same Reynolds number conditions. In this paper, we studied the influence of velocity to flow field structure for the same Reynolds number. First, the numerical simulation of low Reynolds number SD7037 airfoil was carried out to prove the accuracy of this method. Second, at Re =300000, and the factors such as turbulence intensity and so on are unchanged, the change of the pressure on airfoil and flow flied structure was analyzed at the 10km, 15km and 20km three altitude calculation conditions. The results showed that with the increasing of altitude and the flow velocity, the separation point moved forward gradually, it also resulted in the increasing of lift coefficient as well as the drag coefficient, the decreasing of L/D. The result also underlined that the movement of the flow separation point because of the changing of the velocity was the main factor affecting the aerodynamic characteristics for the same Reynolds number. And it provided a reference for the low Reynolds number wind tunnel experiment and numerical simulation
  • Troubleshooting analysis of pin wear of second -pivot oil separator of aero-engine
    2019, 36(6): 22-26.
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    The paper introduces the troubleshooting and analysis process of pin wear of second -pivot oil separator. The design unit conducted a review on design, manufacture technique and process and comparative tests based on fault tree. The anodizing in the production process of the oil separator would make its size out of tolerance. The pin is subjected to a large shear stress during the assembly process, which exceeds its yield strength and causes pin breakage. The paper gives the comprehensive analysis opinions for the cause of failure. Improving the size inspection of the pin surface and manufacture controlling could be used to avoid the malfunction.
  • Microstructure and mechanical properties of ER308L wire fabricated by micro-plasma arc additive manufacturing
    2019, 36(6): 27-32.
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    Abstract：Micro-plasma arc additive manufacturing has the point of high forming accuracy and efficiency. Micro-plasma arc was adopted as heat source, different forming paths were taken to carry out wire and arc additive manufacturing by using ER308l wire. In this study, profile, microstructure and mechanical properties of the 308L components after WAAM were investigated. The results show that the Z-type forming path component’s quality is better than the unidirectional forming path’s. The contrast and analysis of the microstructure and mechanical properties show that the Z-type forming path component has a higher tensile strength, hardness value and percentage of elongation than unidirectional forming path component. The Z-type forming path and one-type forming path components’ microstructure are both composed of austenite and ferrite, but the Z-type forming path’s microstructure has higher grain size, and it abviously appear a crossed microstructure.
  • Research on Electromagnetic Necking of Aluminum Alloy tubes Based on field shaper
    2019, 36(6): 33-38.
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    Abstract：Based on the theory of electromagnetic necking, the relationship between the voltage and the maximum diameter displacement of the 3003 aluminum alloy was studied. The loose coupling method was used to simulate the diameter displacement of aluminum alloy tube. The effects of discharge voltage, number of spiral grooves on the field shaper and the taper of the field shaper on the maximum diameter displacement of the tube were studied .The results shows that with the increase of the discharge voltage, the energy storage of the capacitor increases, and the maximum diameter displacement of the tube also increases; the number of spiral grooves is related to the discharge inductance, and further affects the magnetic pressure and discharge period, the proper selection of the number of spiral grooves of the field shaper can maximize the radial displacement of the tube; the taper has a greater influence on the eddy current loss. The larger the taper of the field shaper, the larger the eddy current loss, and the smaller the radial displacement of the tube. The necking test was carried out on the aluminum alloy tube, and the actual forming effect was in good agreement with the simulation results.
  • Design of Aircraft Brake Controller Based on Simulink
    2019, 36(6): 39-45.
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    Abstract:In order to achieve the fast and stable braking of the aircraft, this paper analyzes the force of the aircraft sliding brake process, and establishes the model of the aircraft brake controller with Matlab/Simulink as the simulation platform, and selects the slip rate as the controlled parameter, combined with the fuzzy control and PID control algorithm for simulation and design of aircraft brake controller. In this paper, the aircraft brake controller controls the brakes by calculating the real-time slip rate of the aircraft through the speed of the wheel and the aircraft, and keeping the real-time slip rate as close as possible to the optimal slip ratio to obtain the maximum coupling coefficient. Good braking torque, which in turn enables efficient and safe braking of the aircraft. The simulation results of Matlab/Simulink show that the fuzzy and PID control algorithm has a fast braking response and strong robustness, which improves the control effect of the aircraft brake controller.
  • Summary of the gate assignment problem in civil airports
    2019, 36(6): 46-60.
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    Gates are important operating facilities and resources in civil airports. It is a core task in the airport operation management to select and reasonable gates for incoming and outgoing flights. Firstly, this paper summarizes the constraints and main optimization objectives that need to be considered in the gate assignment problem, and then summarizes the research methods of the problem from the aspects of mathematical programming, intelligent optimization and system simulation. Finally, future development trends of the gate assignment problem and the key issues that need to be further studied are analyzed.
  • Current situation and existing problems of civil UAV market in China
    2019, 36(6): 61-69.
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    The contradiction between the rapid development of China's UAV industry and the constraints is increasingly apparent. Based on the analysis of the current situation of China's civil UAV market, the market demand and related data of China's civil UAV market from 2011 to 2017 are selected, and the market demand model of China's civil UAV market is constructed. The demand and growth rate of China's civil UAV market in the next few years are predicted. It is concluded that the overall demand of China's civil UAV will show a growth trend, but the growth rate will gradually stabilize. Conclusion: Based on the analysis of the present situation of UAV market, the problems that restrict the development of civil UAV market in China are found, and some policy suggestions are put forward to solve these problems.
  • Research on Performance Evaluation System and Application of Sustainable Supply Chain in Electronic Products Industry
    2019, 36(6): 70-79.
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    With continuous deepening of supply chain management concept in enterprise, sustainable supply chain management plays one increasing important role in enterprise especially at electronic product industry. Therefore, establish systematic supply chain performance evaluation system, seek for better methods to represent supply chain status and promote sustainable supply chain performance of supply chain enterprises are worth of further study. Firstly, according to the characteristics of electronic product industry, a large number of documents are combined with balanced scorecard method to initially construct the index system. And curve fitting sensitivity analysis is carried out for each index to determine the final evaluation index system of electronic product industry. Enterprise performance can be evaluated comprehensively and specifically from 5 aspects by evaluation index system. Then electronic product industry sustainable supply chain evaluation model is formed by fuzzy comprehensive evaluation. Lastly, evaluate and analyze electronic product enterprise performance by analysis of samples. The results show the effectiveness and practicability of evaluation model and improve the evaluation system of sustainable supply chain to some extent.
  • Research progress in flame retardant modification of polyurethane foam
    2019, 36(6): 80-90.
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    Abstract:Polyurethane foam occupies a large proportion of all polyurethane synthetic materials. Because the surface and interior of the foam are pore like structures, and have the advantages of relatively small density, high specific strength, wear resistance and thermal insulation, they can be widely used in various fields such as daily life and industrial production. However, polyurethane foam is an organic polymer material, its oxygen index is relatively low (about 18%), so it is combustible in air, which limits its application. If the flame retardancy of polyurethane can be changed in some ways, the application range of polyurethane can be further expanded. In this paper, the research progress of flame retardancy of polyurethane foam is described from adding flame retardants, reactive flame retardants, nano flame retardants and biological based flame retardants. This paper first introduces these kinds of flame retardants and their mechanism of action. Secondly, the research progress of polyurethane foam flame retardant modification at home and abroad is comprehensively discussed. Finally, the development prospect of polyurethane foam in flame retardancy is prospected.
  • Study on lightweight structure of small optical satellite imitating jellyfish
    2019, 36(6): 91-96.
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    Aiming at realizing the lightweight satellite structure, the bionic design method was used to simulate the shape of the sea and moon jellyfish to design the configuration of the optical satellite and optimize the structure. Through changing the transmission path, the structure performance was fully utilized. Firstly, a mathematical model was extracted from the morphology of the jellyfish, and the stiffness change of the curve under the action of dynamic load was deduced by the formula. Then, the satelite structure was designed according to the mathematical model. Finally, the sensitivily of the fundamental frequency to the thickness of each part of the shell was analyzed by the sensitivity analysis method. The shell thickness was iterated with the transverse first order frequency not less than 35Hz as the optimization objective. The results show that the optimal thickness of the shell is 0.1mm, and the mass of mainbearing structure of the satellite accounts for 4.9% of the mass of the whole satellite. Therefore, the similar jellyfish configuration can provide reference for similar optical satellite design.