Subjects: Materials Science >> Composite Material Subjects: Aviation & Aerospace >> Materials of Aviation & Aerospace submitted time 2024-07-02
Abstract： A generation algorithm of periodic high fidelity representative volume element (RVE) model of unidirectional fiber-reinforced composites (UD-FRP) is introduced. Firstly, based on the random walk algorithm, the fiber is characterized as the Bézier curve, and the tangent direction at each control point is adjusted to follow the multivariable von Mises Fischer function to generate a preliminary soft-core fiber network. Then based on the force-biased algorithm, the corresponding hard-core model is created by adjusting the overlap between fibers to ensure that the fibers in RVE do not twist excessively. In the adjustment process, a three-dimensional near-neighbor list is introduced to significantly improve the algorithm’s speed. Finally, the RVE containing fiber waviness is preliminarily calculated for transverse shear, so as to reveal the research value and application field of this method. The results show that the RVE of the required size and fiber waviness can be generated effectively and quickly by this method, the transverse shear strength of UD-FRP can be affected by the fiber configuration with waviness characteristics. The transverse shear strength of UD-FRP increases with the increase of fiber waviness.
Subjects: Aviation & Aerospace >> Other Disciplines of Aerospace Science and Technology submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： The axial force balance design of the impeller of the fuel centrifugal pump is an important way to improve the product performance,life,reliability and other technical indicators.With the development of aeroengine technology,more stringent requirements are put forward for the axial force balance design of the impeller of the fuel centrifugal pump; The existing design technology,simulation technology and testing technology cannot to accurately guide the axial force balance design of the impeller,resulting in frequent failures such as abnormal wear of the fuel centrifugal pump. This paper analyzes the structural characteristics and working principle of the fuel oil centrifugal pump,and designs a new technology to measure the axial force of the impeller during the working process of the fuel oil centrifugal pump.This technology transfers the axial force carried by the fuel oil centrifugal pump during the working process to the piston of the actuating cylinder,and then uses the closed-loop control principle to control the hydraulic pressure in the two chambers of the actuating cylinder to ensure that the piston position of the actuating cylinder remains unchanged under the axial force of the impeller.The axial force of the impeller can be calculated by the hydraulic pressure of the two chambers of the actuating cylinder and the hydraulic action area. The testing technology studied in this paper solves the problem of testing the axial force of the impeller during the working process of the fuel oil centrifugal pump,can effectively guide the axial force balance design of the impeller of the fuel oil centrifugal pump and optimize the product structure,thus improving the reliability of the product.
Subjects: Aviation & Aerospace >> Basic Disciplines of Aerospace and Technology submitted time 2024-06-17 Cooperative journals: 《应用力学学报》
Abstract： In this paper,an improved reconstruction algorithm that integrates the elliptical trajectory method and the probabilistic imaging method under the Bayesian framework is studied,and the reconstruction algorithm is improved by studying the propagation characteristics of lamb waves on the composite laminate,which solves the problem that the original algorithm is inaccurate in the positioning of hierarchical damage at the edge of the sensor network.In this paper,the finite element analysis under several different layering damage conditions is carried out by taking the curved composite laminate as an example,and the weight coefficient is proposed to provide a reliable solution for the application of the method on the curved composite laminate.The results show that the improved reconstruction algorithm can achieve accurate positioning of layered damage at the edge of the sensor network and layered damage of curved composite plates,and the absolute error of positioning is less than 1 cm.
Subjects: Aviation & Aerospace >> Other Disciplines of Aerospace Science and Technology submitted time 2024-04-19 Cooperative journals: 《应用力学学报》
Abstract： The development of higher performance aspirated hypersonic propulsion has become the most important thing in the development of hypersonic vehicles in the future.The existing scramjet engine based on kerosene fuel is mainly organized in detonation mode.Under the condition of high inflow Mach number(Ma≥8),it is difficult to fully release and utilize fuel energy due to the high-temperature dissociation and chemical non-equilibrium effect of high inflow total temperature zone.In contrast,combustion with inclined detonation structure is closer to constant volume combustion.With the advantages of fast combustion heat release rate and high thermal cycle efficiency,it is an ideal combustion mode which can be applied to high Mach number inspiratory power.Oblique detonation engine can significantly shorten the length of the combustion chamber and reduce the heat release area,which is a promising aspirating power scheme for high Mach number aircraft.Among them,the matching design of each component in the internal flow path of oblique detonation engine,fuel injection-mixing,initiation and residence of oblique detonation wave are the key technologies in the development of oblique detonation engine,and are the research hotspots in hypersonic field at present.However,due to the high speed,high total temperature and total pressure flow conditions and the strong discontinuous and high-speed propagation characteristics of detonation waves in the flow field,the existing experimental and numerical simulation research methods are difficult to carry out detailed research on the combustion flow mechanism,thus limiting the disclosure of relevant control mechanisms and the establishment of high-precision models,making it difficult to develop oblique detonation engine engineering.There are still many places worth exploring in the current research,and this paper summarizes and puts forward relevant suggestions for the next research.
Subjects: Materials Science >> Composite Material Subjects: Mechanics >> Solid Mechanics Subjects: Aviation & Aerospace >> Manufacture Technology of Aerocraft submitted time 2024-04-09
Abstract： The mechanical properties of unidirectional fiber-reinforced plastic (UD-FRP) are affected by internal micro-defects, such as random fiber arrangement, fiber misalignment, and micro#2;voids. This study aims to investigate how these multiple micro-defects interact with each other and how they affect the strength and failure mechanisms of UD-FRP through computational micromechanics. The failure behavior was simulated by the finite element analysis of a representative volume element; both matrix and interface failure were considered for the different loadings and their combinations. It was found that these micro-defects significantly weakened the compressive strength of UD-FRP along the longitudinal direction. Especially the fiber misalignment magnified the effect of fiber arrangement, while the micro-voids reduced the effect. Besides, the fiber arrangement and micro-voids significantly weakened the tensile and compressive strength of UD-FRP along the transverse direction. Moreover, transverse and longitudinal shear strengths are significantly affected by micro-voids, but only longitudinal shear is affected by fiber arrangement, and this effect is also weakened by micro-voids. Finally, the damage envelope under the combined longitudinal compression and transverse loads was obtained and compared with the Tsai-Wu failure criterion. The results showed that the Tsai-Wu criteria can provide an effective estimation for the failure locus under this biaxial loading condition.
Peer Review Status:
Awaiting Review
Subjects: Aviation & Aerospace >> Basic Disciplines of Aerospace and Technology submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
Amphibious aircraft has some unique advantages in the field of aviation fire protection.However,when amphibious aircraft glides at high speed on the water surface to scoop water and fly to fight fire in the air,the moving liquid flow inside the body will bring the unsteady water impact effect.For the fluid-structure coupling characteristics of aircraft,previous studies have mainly focused on the interaction of the external flow field with rigid aircraft,and little attention has been paid to the effect of the internal flow field on the structural deformation and stress distribution.According to the mission mode of the amphibious aircraft in this paper,the coupling simulation of smoothed particle hydrodynamics and finite element method is adopted,the structural finite element modeling and internal flow field modeling of the main affected fields are established respectively,and the fluid-structure coupling method is used to solve the dynamic stress distribution of the structure in the process of high-speed water scooping and fire fighting in air.Results show that during the high-speed water scooping process of the aircraft,the structure is continuously excited by the water impact,the stress of each part of the structure is constantly changing,and there is great oscillation amplitude of the stress in some regions.The maximum transient stress of bulkhead at the typical moment reaches 0.38σb,and the maximum oscillation amplitude of stress is 0.42σmax.And when the aircraft drops water in the air by gravity,the water impact excitation on the structure is relatively weak,the maximum transient incremental stress of the end frame is 0.15σb,the maximum amplitude is 0.22σMax,so the incremental stress level of the structure is not high and the fluctuation range is not large.
Subjects: Aviation & Aerospace >> Basic Disciplines of Aerospace and Technology submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract：
The continuous gust aeroelastic response is generally analyzed and solved using random theory in engineering.By integrating the frequency response functions of the airplane with the power spectral density of excitation,the root mean square value of each degree of freedom can be obtained.The method is based on the linear solution in the frequency domain,and the nonlinear response analysis cannot be directly carried out.Therefore,based on the matched filter theory,a simplified calculation method for continuous gust response considering structure nonlinearity is described in this paper.By introducing a gust filter,which is connected in series to the aeroelastic dynamic system of the whole plane,a time-domain analysis model of continuous gust is obtained.Based on the root mean square value of the selected degrees of freedom,the matched filter theory is used to calculate a set of the “time correlated response for the other degree of freedom.On this basis,for the nonlinear structure model,by adjusting the impulse strength amplitude,the maximum response is found as the nonlinear result,and finally a nonlinear continuous gust response calculation method suitable for engineering and structural nonlinearity is established.The simulated results showed that the method established in this paper can be used to obtain the “time-correlated” response of each degree of freedom,and can also be used for structural nonlinear response calculation.
Subjects: Aviation & Aerospace >> Basic Disciplines of Aerospace and Technology submitted time 2024-02-07 Cooperative journals: 《应用力学学报》
Abstract： Vibration and thermal environments have been key factors that influence the safety of aircraft structure.The combined effect of these two factors causes fatigue damage to the aircraft structure more easily.This paper studies different structure types,including stiffened panel and honeycomb.Vibration properties,fatigue life,and damage location of titanium alloy panels with different thicknesses,bar spacings,and connection types are studied by the methods of analysis and experiment.For stiffened panel,damage occurs at fillet or corner plate.Honeycomb panel gets no damage in eight hours of experiment.Panels’ thicknesses,bar spacings,and connection types have a small effect on their vibration fatigue life.
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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