In order to study the low energy impact resistance of re-entrant star-shaped(RES)and re-entrant circular star-shaped(RECS)honeycomb sandwich panels with negative Poisson ratio,a finite element model of honeycomb sandwich panels with composite laminates and ABS honeycomb is established by using commercial software ANSYS/LS-DYNA.Impact response of the composite sandwich panels with RES honeycomb and RECS honeycomb is analyzed numerically at low impact energies of 10 J,15 J,30 J.In this paper,the impactor displacement versus time curves、contact force versus time curves and energy absorption ratio of sandwich panels under different impact conditions are analyzed and compared.The simulation results show that under the same impact conditions,the damage depth of RECS honeycomb sandwich panels is greater than that of RES hon-eycomb sandwich panels,and the difference is more obvious when under in-plane impact.In addition,the impactor has a lower rebound speed after impacting RECS honeycomb sandwich panels,that is,the RECS honeycomb sandwich panel has a higher energy absorption ratio.According to the above results,it is concluded that RES honeycomb sandwich panel has better low en-ergy impact resistance than RECS honeycomb sandwich panel,but the latter has better energy absorption performance.
When air-breathing aircraft is flying over a wide area,the upflow of the combustor central axis will change greatly,and the flow field parameters will fluctuate along the axis. Therefore,it is necessary to carry out a study on the influence of axis flow field parameter fluctuation on combustion chamber performance,so as to provide relevant theoretical support for the com-bustion chamber of air-breathing aircraft in wide-area flight design. Based on the N-S gas-phase control model,combined with combustion model,turbulence model,burning rate model and mass transfer model,a numerical simulation model of flow com-bustion in solid fuel scramjet combustor is established. Through this model,the influence of the upflow field parameter fluctua-tion of the central axis on the combustor performance is carried out. The results show that for a optimized combustor configura-tion,different inlet air flow rates will cause the Mach number of the combustor to oscillate along the flow direction. The greater the oscillation amplitude,the greater the total pressure loss. Too high or too low inlet air flow rate will both result in Mach num-ber oscillation in the combustor. However,selecting a suitable inlet air flow rate can significantly reduce the Mach number os-cillation of combustor flow. Therefore,for different combustor configurations,appropriate inlet air flow should be designed to reduce the Mach number oscillation of the flow field in the combustor,reducing the flow loss and improving the working per-formance of the combustor.
As a measuring element in wind tunnel test, it is important to ensure the measurement accuracy of strain balance.However, in the continuous wind tunnel, due to the long running time of the wind tunnel and the continuous transformation of Mach number, the temperature distribution of the balance body will be uneven, resulting in temperature gradient.This temperature gradient has an obvious influence on the measurement accuracy of the axial force of the balance.In order to explore the influence of temperature gradient on the axial force and strain output of the balance in the continuous wind tunnel, three temperature loading conditions were summarized according to the actual working conditions, and the thermal-solid coupling analysis of the 80A balance was carried out by ANSYS Workbench.The results show that the higher the temperature of the base point of the temperature gradient is, the faster the temperature input is, the more uneven the temperature distribution of the balance is, and the larger the temperature gradient is, the larger the axial force and strain output is. Considering the heat conduction of the back support rod, the temperature distribution of the balance body is relatively uniform, the temperature gradient is small, and the output of axial force and strain is small.
Projectile conical motion causes significant control disturbances in the guidance system. In order to compensate for this error,a new conical error compensation algorithm has been analyzed to improve the accuracy and real-time performance of the bullet attitude control system in a high-dynamic motion environment. Combining the quaternion four-level Runge-Kutta method and the triad equivalent rotation vector method,an improved triad quaternion attitude algorithm based on modified Ro-driguez parameters for angle increment output is utilized. Derive the corresponding differential equation expressions to establish the mathematical model for solving the attitude using the improved triad quaternion algorithm. Simulation results demonstrate that compared to traditional conical error compensation algorithms,improved algorithms can more effectively compensate for conical errors,with an average accuracy improvement of approximately 17. 32％,reduce computational load in high-dynamic environment and improve real-time performance by approximately 22. 54％.
针对实测爆炸冲击波信号中存在大量噪声信号以及自适应白噪声完整集合经验模态分解(CEEMDAN)方法在降噪过程中容易出现信号失真的问题,提出了一种基于CEEMDAN方法和高斯混合模型(GMM)的爆炸冲击波降噪算法.该算法首先将原始爆炸冲击波数据通过CEEMDAN方法分解得到若干个本征模态分量IMF,并利用GMM聚类算法将IMF分量分为多个类别.通过计算不同IMF分量的方差贡献率校核聚类结果,剔除高频噪声类别的IMF分量.对受噪声干扰的IMF分量,采用小波阈值方法进行滤波去除噪声.最后,将滤波后的IMF分量与未受噪声干扰的IMF分量一起重构,并获得降噪后的爆炸冲击波信号.实验结果表明:CEEMDAN-GMM与小波阈值算法信噪比值RSNR和均方根误差值MRMSE分别比CEEMDAN方法和CEEMDAN-小波阈值算法提高了 10.19 dB和 2.99 dB,降低了 0.42×10-4和0.14×10-4.
