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Zhou L.,First Aircraft Institute of AVIC
Proceedings of 2010 Asia-Pacific International Symposium on Aerospace Technology, APISAT 2010 | Year: 2010

Aft body of the transport airplane is upswept in a certain extent because of loading cargo and fuselage attitude during takeoff and landing, and the upsweep of the aft body can make airflow separating and drag increasing. This paper gives the main parameters which affect the aerodjniamics of aft body from the aerodjniamic optimization aspect. At the same time the range of these parameters is determined through theory analysis, wind tunnel tests and calculation results. At last the sensitivity of these parameters is discussed in this paper.

Li B.,Northwestern Polytechnical University | Zhang Y.,First Aircraft Institute of AVIC | Yang Z.,Northwestern Polytechnical University
21st International Congress on Sound and Vibration 2014, ICSV 2014 | Year: 2014

During dynamic similitude model experiments, it is generally difficult to assure the damping ratio of scale model is same with its original structure. This problem results in that the measured dynamic response of scaled model with damping errors cannot be used directly to predict the original structure's response. An updating method of the time history response for dynamic similitude models with dissimilar damping ratios is proposed to solve the problem. It is assumed that the practical and ideal scaled models' damping can be expressed as classical damping model and then the updating equations are deduced from the relationship between the practical and ideal scaled models' vibration equations. These updating equations show that the calculation of the updating value can be transformed as a dynamic response solution of the ideal scale model forced by an equivalent additional exciting force. Considering that the response measurement points in the realistic experiment are usually limited, a model reduced order method is proposed to reconstruct the responses of those non-measured points. The proposed updating method just need to know modal damping ratios, mass and stiffuess matrixes of the original structure and practical scaled model, and these conditions are easy to be satisfied. Finally, this updating method is used to update the dynamic response of a scaled model of fighter's wing beam structure. Updating results show that the after-updated displacement power spectrum density and root mean square values are consistent with practical measured responses, which verifies the feasibility and validity of the proposed updating method.

Wei K.,Northwestern Polytechnical University | Zhu G.,Northwestern Polytechnical University | Tang Y.,Northwestern Polytechnical University | Li X.,First Aircraft Institute of AVIC
Polymer Journal | Year: 2013

Electroactive shape-memory hydro-epoxy/carbon black composites are investigated in this study. The thermomechanical and the shape-memory properties of these composites are characterized using dynamic mechanical analysis and U-type shape-memory tests. These results indicate that the glass transition temperature (T g) of the composites decreases first and then increases slightly as the carbon black content increases. The storage modulus at high temperatures increases as the carbon black content increases. The percolation threshold of the electroactive shape-memory hydro-epoxy composite is lower than that for many other composites. Because of the low percolation threshold, the electroactive shape-memory hydro-epoxy composite exhibits excellent shape-memory property. The sample filled with 1.9 wt% carbon black can recover nearly 100% of its original shape in only a few minutes under an applied voltage of 200 V. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved.

Wei K.,Northwestern Polytechnical University | Zhu G.,Northwestern Polytechnical University | Tang Y.,Northwestern Polytechnical University | Li X.,First Aircraft Institute of AVIC | And 2 more authors.
Composites Part B: Engineering | Year: 2013

Shape-memory polymers (SMPs) have the capacity to return large strains by external stimuli. Among various SMPs, shape-memory epoxy has received considerable attention because of its superior mechanical and thermal properties as well as excellent shape-memory performance. In this study, short glass fibre-reinforced shape-memory hydro-epoxy composites are developed to improve further the mechanical property of shape-memory epoxy resin. The thermomechanical and shape-memory properties of the developed composite materials are investigated by dynamic mechanical analysis, bend test and shape recovery test. The results indicate that the glass modulus and bend strength of the developed composite materials initially increase and then slightly decrease with increasing short glass fibre content. The glass transition temperature of the developed composite materials does not change with increasing short glass fibre. When the short glass fibre content is less than 4.5 wt.%, full recovery can be observed after only several minutes at different temperatures. The shape-memory property of the composite materials is not affected greatly. However, when the short glass fibre content is more than 4.5 wt.%, the material would be destroyed after deformation. © 2013 Elsevier Ltd.

Peng C.,Northwestern Polytechnical University | Wang X.-M.,Northwestern Polytechnical University | Ma T.-L.,Northwestern Polytechnical University | He A.,First Aircraft Institute of AVIC
Kongzhi yu Juece/Control and Decision | Year: 2016

An improved eigenstructure assignment algorithm with output feedback is presented to solve the problem that the general eigenstructure assignment with output feedback can't completely guarantee the stability of the closed-loop system. In this improved algorithm, the quadratic performance index is introduced to convert the problem of the closed-loop stability into a linear quadratic optimal control problem, which ensures the stability of the closed-loop system. Taking into account that the closed-loop system designed by eigenstructure assignment has a poor robustness, the condition for ensuring the system robustness is given to solve the robust problem of the closed-loop system. Finally, simulation results on a flying wing aircraft show the effectiveness of the eigenstructure assignment proposed. © 2016, Editorial Office of Control and Decision. All right reserved.

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