Search

The primary structure formation criterion based on the particle packing theory was applied to the gradation design of fine-grained porous asphalt mixture, optimized the content of the range of the primary structure further within the grade range required by specification in order to enhance the skeleton strength of and improve the high-temperature performance of fine-grained porous asphalt mixture, laboratory tests and theoretical analysis research methods were combined to verify the applicability of this criterion to enhance the aggregate strength by the skeleton penetration test, and determined the influence of the skeleton strength of aggregates on the high-temperature performance by the modified uniaxial compression creep test. The research results show that applying the primary structure formation criterion to the gradation design can improve the skeleton strength and the high-temperature performance of fine-grained porous asphalt mixture, and there is a obvious correlation between the two aspects, the larger the skeleton strength, the better the high-temperature performance. [ABSTRACT FROM AUTHOR]

The acoustic liner of the nacelle of an aeroengine is the most important noise reduction device of the engine. In order to establish an accurate impedance model related to the structure and acoustic performance of the acoustic liner, it is necessary to analyze the acoustic impedance eduction technology of the liner. Two liner impedance eduction techniques, in-situ impedance eduction method and straightforward method, were compared and analyzed. Same flow tube acoustic test platform, liners with controllable deviation, and repeatability test of impedance measurement were used to ensure the subjectivity of the comparison. Two aforementioned impedance eduction methods were used to obtain the acoustic impedance of both single-degree-of-freedom acoustic liner and double-freedom liner. It indicated that the measurement results from the two impedance eduction methods were well matched with each other in frequency of both mid-range and high-range, and there were significant differences in the low-frequency ranges. Compared with the straightforward method, the in-situ method was more applicable for a wider range of frequency, and it could also identify the local acoustic impedance characteristics of the acoustic liner. In-situ method was less limited for the size of acoustic liners, however, the breaking of the liner structure was inevitable for such method, which means such method was more suitable for traditional liners. The straightforward method could measure the overall impedance characteristics of the acoustic liner. It could also obtain accurate impedance results in both middle and high frequency range without breaking liner structures, and therefore it could be used in a wider range of plate-type sound-absorbing materials. [ABSTRACT FROM AUTHOR]

In order to study the aerodynamic noise of UAV (unmanned aerial vehicle)propeller at ground takeoff conditions, a propeller aerodynamic noise test platform was developed. The propeller aerodynamic noise test was carried out in a semi anechoic room, and the aerodynamic performance and far-field noise characteristics were obtained. The variation of aerodynamic parameters such as tension and torque and the directivity of far-field noise with propeller speed and blade angle were analyzed. The results show that the aerodynamic parameters such as tension and torque increase with the increase of rotating speed and blade angle. The region with largest far-field nosie varies with the propeller speed and blade angle. The test platform and test scheme could be used as a means to valuate the effect of propeller aerodynamic noise design. [ABSTRACT FROM AUTHOR]

In order to obtain the fatigue life of aeroengine turbine rotor blades, orthogonal load decoupling combined loading was realized by electromagnetic induction heating and high-low cycle composite load coordinated loading control method. The coupling responses of rotor blades under high temperature environment, low cycle centrifugal load and high cycle vibration load were studied, and the above technology were verified based on turbine blade simulation test pieces. The results show that the test technology is feasible and correct. It can be seen that this technology can realize multi field coupling complex load strength test loading of aeroengine structural components. [ABSTRACT FROM AUTHOR]