Subjects: Aviation & Aerospace >> Aerospace System Engineering submitted time 2023-12-15 Cooperative journals: 《应用力学学报》
Abstract： The coupling between flight control system(FCS)and helicopters can induce or aggravate the vibrations of the helicopter.For the lack of systemic understanding of the problems at home,much more human resource and time have been wasted to do some troubleshooting from the beginning when the vibration problems caused by coupling between FCS and helicopter appear,thus delaying the model development progress.In this paper,two coupling models between FCS and helicopters are presented from the perspective of helicopter vibrations,according to which two categories are formed and the frequency characteristics are analyzed.The mechanisms as well as the critical factors in the interconnection are summarized.Aiming at two coupling paths,general resolutions are addressed to avoid the vibration problems caused by coupling between FCS and helicopters.Further analyses are made of the critical pathway and the associated frequency range,based on a practical problem of a certain helicopter model,which indicates the severity of the problem caused by coupling between FCS and the helicopters.The results prove the effectiveness of the resolutions presented,and can serve as the reference for dealing with the analogous vibration problems caused by coupling between FCS and helicopters.
Subjects: Aviation & Aerospace >> Aerospace System Engineering submitted time 2023-12-15 Cooperative journals: 《应用力学学报》
Abstract：
Aiming at the fracture fault of helicopter joysticks,the method of combining simulation with experiment is used to reproduce the fault ofhelicopter joysticks components.A vibration fatigue analysis method considering frequency coupling effect is proposed,which provides data support for the optimal design of vibration fatigue resistance of joystick support.The loading direction of the test load and the dangerous position of the structure are determined through dynamic simulation analysis.Through reasonable test planning,the effects of different load levels and different structural characteristics on the vibration fatigue life and failure mode of the system are analyzed.The results show that when considering the frequency coupling effect,the vibration fatigue life of structure is more sensitive to the load magnitude,and there will be an obvious strong resonance region in the time-domain response of structural vibration.The occurrence of the strong resonance region in the crack propagation process has an important impact on the structural failure mode.
Subjects: Aviation & Aerospace >> Aerospace System Engineering submitted time 2023-12-15 Cooperative journals: 《应用力学学报》
Abstract： The structural elasticity of large aircraft will significantly affect the load size and distribution of the airframe.It is important to calculate the load variation caused by structural elasticity accurately for improving the design level of aircraft.In this paper,a modified method of aeroelastic theory for aerodynamic load of wing is presented,which uses the theory of engineering beam to calculate the aerodynamic increment caused by the deformation,then iterates to converge,and improves the lift line theory in NACA-TN3030 report by using the theory of lift surface.The accuracy of the method is proved by wind tunnel test.In flight test,the data of wing deformation and flight parameters are measured,and the elastic correction calculation is carried out respectively with the data of these two aspects as input.The results of the two methods are verified by each other,and the correction results are in good agreement with each other.After load correction,the bending moment of wing root is reduced by about 3%.This method is easy to be popularized in engineering.It is significant to lighten the weight of wing structure.
Subjects: Aviation & Aerospace >> Aerospace System Engineering submitted time 2023-12-15 Cooperative journals: 《应用力学学报》
Abstract：
A rapid analysis method of fatigue life and crack propagation life for repaired butt-joint is proposed based on three-dimensional finite element analysis.Considering the friction and rivet clamping force,the three-dimensional finite element models of different repaired configurations are established.An approximate model is constructed to represent the variation of pin load with the increase of crack length based on the analysis result.A rapid analysis method for calculation of the stress intensity factor for cracks in butt-joint is proposed based on weight function method,from which a predictive method for the crack propagation life is then developed.The fatigue life and crack propagation life of 4 repaired configurations are analyzed,Results shown that the dangerous positions are all located at the first rivet row in skin,and the pin load of different configurations is quite different.In addition,increasing the number of rivet rows and adopting stepped patch can reduce the pin load of the first rivet row.The fatigue life can be significantly enhanced by reducing the pin load of the first rivet row,while the improvement for crack propagation life is less significant.
Subjects: Aviation & Aerospace >> Aerospace System Engineering submitted time 2023-12-15 Cooperative journals: 《应用力学学报》
Abstract：
The near-Earth miniaturized gravitational wave detection formation has a short development period and low cost.Therefore,it is suitable for the verification of key technologies in the early stage of gravitational wave projects and has important engineering application value.Compared with the deep space environment,the inter-satellite distance of the formation of near-Earth gravitational waves tends to fluctuate greatly under the influence of the perturbation force,posing a challenge to the natural stable formation configuration design and accurate initialization.Based on the orbital dynamics and relative motion dynamics under the two-body gravitational field,this paper makes a preliminary design of the equilateral triangle formation configuration.Taking the long-term stability of the configuration as the goal,the natural stable configuration under perturbation conditions is solved with the perturbation analysis theory and the numerical search method of intelligent optimization,which provides a stable configuration design plan for the formation of near-Earth gravitational wave detection.Finally,for the precise initialization of the detection configuration,the global optimal differential correction strategy is explored,and the high-precision construction of the near-Earth gravitational wave detection formation is realized.
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