Abstract:When the weak interface of composite materials subjected to the transverse tensile, composites with weak interface involve interfacial cracks before the overall damage of the material. The measured transverse tensile strength of the weak interfacial bonding composite is even much smaller than the original tensile strength of the pure matrix. The stress concentration factor (SCF) is defined considering the existence of cracks on interfaces with in-situ strength of the matrix assigned as its original counterpart divided by the SCF. A new method is provided to predict the load level when the interface crack occurs and the strengths of composites under uniaxial tensile.

Abstract:In order to enhance the fast and stable ability of target recognition of high resolution SAR images in a complex battlefield environment. Due to the changing characteristics of size, orientation, rotation, and the severe influence of strong clutter background, that cause serious influence for the ground target recognition. A method of affine 3D object model to two-dimensional plane is proposed, Cosine-Fourier moment and Rayleigh distribution CFAR detection are used to extract the moment and peak features, respectively. The model and analysis of target recognition are done by cascade combination classifier in high dimension and pose change without additional overhead of guidance and control systems. Finally, experimental results prove it accurate and believable.

Abstract:In this paper, the main research is the finite element modeling and strength analysis of the anti-rust bolts with oil reservoir and helical groove, and obtain its bearing capacity by finite element method. In the finite element software, an indirect method is used to build the helical entity, which can obtain the finite element mesh with better quality. The finite element simulation was carried out by using the progressive failure analysis and the maximum stress criterion, then compares its results with the results of the non-progressive failure analysis. Simulates by using the method of reduction calculation in order to consider the influences of bolt’s strength caused by the groove at the same time, and compares reduction calculation results and the original results and analysis. The results of the finite element calculation shows that the results of the progressive failure analysis and the maximum stress criterion are smaller than the results of the non-progressive failure analysis, The results of reduction calculation are similar to the original results.

Abstract:The changing element size or numbers are always introduced in the traditional FEM, which is not suitable for programming and cannot ensure the computational accuracy. Based on the generalized moving least squares (GMLS), an improved global interpolating element-free Galerkin (EFG) method was applied to dynamics of an axially deploying or retracting flexible beam. The element-free transverse vibration equations were built according to the Hamilton principle. The frequency characteristics，free vibration with different axially motion and the forced vibration response of the beam are calculated in numerical examples. By comparing with the reported available results, the feasibility of the EFG method applied for the time-varying parameter systems is verified.

Abstract:Pitting corrosion is a typical damage of aircraft aluminum alloys structure in the service environment which could initiate crack under the fatigue load and shorten the structure fatigue life.In order to fully understand the function mehcanism of the pitting corrosion to the corrsion fatigue life ,the growth behavior of aluminum alloy pitting corrosion should be studied.Based on the electrochemical corrosion mechanism and the microstructure, the size of corrosion pit was chosen as research parameter, the model of aluminum alloy pitting corrosion growth behavior was researched, and the result between model calculating and the LY12CZ pitting corrosion test was comparatively analyzed, which showed that the established model could reasonably reflect the evolution rule of aluminum alloy corrosion pit size parameter.

Abstract:FEM analysis has become an important tool for the design of aircraft. In order to improve the accuracy of FEM simulation, it is necessary to modify and update the FEM models. This paper took a global FEM of some helicopter as subject, based on strain response measured in static test experiment, a variable sensitivity analysis and model updating were performed. Because of the big numbers of measure points of the test and the huge degrees of freedom of the global FEM, and a new dependency arithmetic which was suitable for global model was firstly given. Based on the arithmetic and combined with the results of some test case, partial parameters of the global FEM were updated to attain a better conformance with the test results. At last, a verification with results of other load cases were performed and a conclusion was given that the conformance between test results and simulation results after the global FEM updating in other cases were also promoted as predicted, which proved the feasibility and effectiveness of the dependency arithmetic and the process of global FEM optimization.

Abstract:The testing micro spacecraft detects the Space exploration technology. By studying the trajectory and attitude change, the real-time response and accuracy is compared and analyzed. Disturbance of launching process changes initial operation conditions. The orbital dynamic model and attitude dynamic model considered environmental factors based on Euler equation are developed, and a numerical calculation about operation process is carried out under different initial operation conditions. The results indicate that: various degree of change about the motion situation for spacecraft is taken place when initial operation conditions change; orbital eccentricity and period increases with the increase of initial orbit entry velocity; nonzero launching angle will cause orbit displacement and rotation, pitch launching angle mainly cause the variation of pitch angle, Yaw launching angle mainly effects roll angle and yaw angle, and greater the angle, the greater the range; the attitude changes reduce when the spin angular velocity increases.

Abstract:The projectile which works in a certain speed and altitude throws parachute-bomb system, and swing of parachute-bomb systems influence interception and impact angle and attack effect. Attitude swing of cross parachute-bomb system in balanced wind speed has been studied by test of vertical wind tunnel and unsteady numerical simulation. The constraint method of ‘pulling’ is presented in the test, and the shape and drag coefficient and swing frequency of parachute is obtained by way of the test. On this basis, the reason of parachute swing is further studied by three-dimensional unsteady numerical simulation. The results indicate that the computational drag coefficient and frequency of normal force coefficient (lateral force coefficient) is close to that of the experiment, and the flow around the parachute is unsteady. There are two vortices, whose directions are contrary and intensities vary alternately in the parachute. Moreover, there is the unsteady detached flow upon the parachute. The vortices relate with the unsteady detached flow. Aerodynamic coefficients change periodically. Thus, the attitude of the parachute-bomb system become unstable. The method of wind tunnel test and numerical simulation would be referenced in the design of similar parachute-bomb system. And the conclusion can provide a theoretical basis to optimize the parachute-bomb system.

Abstract:The installation of an appropriate slender-rod on the nose of supersonic aircraft is able to reduce flight noise level. Based on Fluent quasi three-dimensional numerical simulation method in this paper, 24 groups of slender-rod models are simulated and analyzed and compared in influence on the far-field pressure, to compare noise reduction effect of various slender-rod and summarize effective noise reduction model. Furthermore, from the theory of aerodynamics ,this paper explains the solution of numerical simulation ,and revealing inner relation between the slender-rod noise reduction effect and slender-rod shape. Besides, this paper analyze the influence of slender-rod to the sonic boom from the aspects of the far-field pressure maximum and curve shape etc. The results show that single-stage conical slender-rod with 6 meters length and 12.5 degrees half- cone angle has obvious effect in noise reduction; reasonable multistage conical slender-rod significantly reduces the initial overpressure value, and delay the far-field pressure peak ;concave-concave type, concave-cone type, convex-concave type and convex-cone type slender-rods greatly reduce the far-field pressure peak value and improve the shape of pressure curve and have More significant noise reduction effect ; strong expansion wave produced by slender-rod can significantly weaken the nose shock wave in the process of shock wave propagation, thereby weakening the sonic boom.

Abstract:Aiming at the problem of global/local search balance ability of modern heuristic intelligent algorithms, a new hybrid global optimization algorithm MABCPSO is presented, which is based on the combination of the particle swarm optimization (PSO) and artificial bee colony algorithm (ABC). As a hybrid algorithm,the dual population evolution strategy and information sharing mechanism are used to combine the PSO and ABC algorithm organically. On the one hand, by using the development capability and volatility of ABC algorithm,to maintain the diversity of the population, to avoid the population into the local optimal; on the other hand the mining capacity of PSO algorithm is used to search the individuals with higher fitness value, and accelerate the convergence speed. Function test results show that MABCPSO algorithm has better optimal ability compared with PSO and ABC algorithm. The algorithm is applied to the aerodynamic optimization design of airfoil, showing a good/local search balance, and achieves good optimization results.

Abstract:In order to analyze the effects of stiffeners’ cross section shape on the vibration fatigue property of stiffened panels, two kinds of panels were carried out. Firstly, the stiffened panels with L-shaped stiffener and T-shaped stiffener were excited by base motion at the resonance frequency. The effects of different stiffeners’ shape on the frequency and vibration fatigue life of thin-walled structures were studied experimentally. The possible mechanism was analyzed theoretically and the test process was validated by MSC software. Secondly, based on the reasonable FEM simulation, the thin-walled stiffened panels were excited by a sinusoidal distributed load under two boundary conditions (clamped and simply supported) in MSC simulation. The effects of stiffeners with six shapes were discussed on the frequency, stress distribution and vibration fatigue life of thin walled structures. The results showed that the first natural frequency of panel with Z-shaped stiffener is the maximum among all the configurations. And the peak value of the stress occurred at the same position. When the edges of the panel are fully clamped, the damage position occurred at the side of the stiffener and the fatigue life of Z-shaped stiffened panels is the longest. When the edges of the panels are simply clamped, the damage position occurred at the centre region of the panels and the L-shaped stiffened panels had the longest life.

Abstract:Random Uncertainty is the inherent attribute of natural and engineering materials; the heat conduction behavior is one of the most important questions in servicing process of thermal protection system, and the research on the heat conduction problem of random materials can provide theoretical basis for integrative design of material and structure in thermal protection system. A novel statistical multiscale analysis method based on two-scale asymptotic expansions is proposed to predict heat conduction performances of random porous materials. The statistical multiscale formulations and statistical multiscale boundary element algorithm are brought forward. Besides, the validity of the proposed method by comparison with theoretical results was verified. Finally, the effect of microstructures on the macroscopic thermal properties for the porous ceramic materials is investigated. Numerical results prove the accuracy and efficiency of our method for multiscale simulation of heat conduction problem in random porous materials.

Abstract:Turbine blade is the core component and vulnerable part of the gas turbine. It works in a very poor environment, and bears huge alternating stress under high temperature condition. Therefore, turbine blade is the most frequently failure component in the gas turbine and the main failure mode is fatigue failure due to crack propagation. According to the start working condition of a gas turbine, the load spectrum is worked out. The dangerous location of blade failure is determined by transient thermal elastic-plastic finite element analysis (FEA), and the solid model of cracked blade for FEA is established. According to the J integral strength criterion and the results of transient thermal elastic-plastic FEA, the non-probabilistic reliability of the cracked blade is analyzed, so a new method or way is provided for the reliability analysis of imperfect structures.

Abstract:In order to make the angles of aircraft aileron deflection can be controlled more accurately, an improved spatial four-bar (RSSR) mechanism is applied to the end of the transmission mechanism of the light aircraft aileron control system. The mathematical model of the mechanism is established by the method of direction cosine matrix, and the displacement formula of the mechanism is derived. In order to make an optimization design of RSSR mechanism, the parametric model of the mechanism is established in the software of ADAMS by estimating the initial value of the mechanism parameters, the objective function, the constraint function and the deriving function are determined, the sensitivity of each design point to the objective function was studied, the optimal design of the design variables with high sensitivity is carried out by the generalized reduced gradient algorithm. The results show that the aileron deflection angle has great influence by the relative position of each point of the RSSR mechanism, the relative error of the deflection angle of the aileron upward and downward are reduced from the initial 2.35% and 5% to 0.1005% and 0.1033% respectively, which demonstrated the optimization design for the mechanism meet the requirements of precision exactly. For the purpose of verifying the feasibility of the mechanism, the three-dimensional modeling for the mechanism is established in the software of CATIA, and used in a prototype of a 5-seat composite material light aircraft finally.

Abstract:A cross-sectional shape generating method for the compact and offset bend double-S-inlet design of subsonic stealthy UAV is proposed according to curvature regulation. The inlet design procedure can quickly accomplish the surface composition of Double-S-inlet with complex conformal intake shape and complex bending style. Utilizing that method, six ducts are created and multi-parameters which include centerline curvature, area ratio and middle-cross-sectional shape are analyzed to studied the effects on duct perforce. Results indicate that the reverses at the top region of the second S part and the total pressure distortion arose by secondary flow should be considered carefully in the Serpentine inlet design procedure. Results also indicate that there are more complex flow structure in the Serpentine inlet compared to that in the S-duct inlet, and that the conventional design approach used in the S-duct inlet is still effective in the double-S-inlet design procedure.

Abstract:The numerical simulation has been carried out to investigate the cold flow and hot flow characteristics for composite structure of cantilever ramp injector and cavity in the supersonic combustion. The structure without cavity and different positions of cantilever ramp injector/cavity combination has been comparative analyzed. It is noted that the combination distance is h=30mm while the total pressure loss is large, but it has a stronger effect of mixed fuel mix and combustion efficiency greater, flow characteristics is the best.

Abstract:The ideal discontinuities existing on the surface of weapons and equipment have important effect on the objects’ electromagnetic scattering characteristics. According to the theory of electric field superposition, and based on the actual discontinuities and carrier, a novel computational approach for the electromagnetic scattering extraction of ideal discontinuities is proposed. And combining this novel approach with darkroom test and MLFMA(Multilevel Fast Multipole Algorithm), the electromagnetic scattering characteristics of ideal single-column, multi-column gap and step discontinuities are studied, and the correctness and efficiency of the new extraction approach are verified. The novel computational results show that this approach is not only simple and efficient, but also possesses consistent computation accuracy with MLFMA, which could fast extract the electromagnetic scattering characteristics of ideal single and multiple columns discontinuities. Besides, the ideal discontinuities have significant effects outside the specular scattering region, especially for the effects of step discontinuities, and ideal multi-column scattering also has strong coupling, performed as more scattering peaks, which are the effects of superposition of each ideal column electromagnetic discontinuities.

Abstract:Effect of the flow field structure on the performance of the engine. It is important to structure parameter design of engines that set up perforated distribution plate to adjust the flow field. Use CFD to simulate flow field, and total pressure uniformity, Oxygen valve rate of flow uniformity and stress condition of valve spool. Result can provide reference for the design and optimization of assembly line.