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351.
传统应变测量方法在小量程气动力测量方面存在灵敏度不高的问题。针对此现象,从单分量入手,设计以位移测量法为基础的悬臂梁天平。以3台悬臂梁天平为例:1台传统应变天平,2台不同槽深的新型位移天平,分别进行静态校准试验及有限元仿真。将光纤应变计应用于1 mm 槽深位移天平,进行准度计算;将光纤、电阻2种应变计同时粘贴在传统应变天平及2mm槽深位移天平,进行2种应变计及2种测量方法的性能对比。由试验结果可知:试验中1mm槽深位移天平准度为0.02%;2mm槽深位移天平位移法测量灵敏度相比传统测量方法提高3倍;2mm槽深位移天平灵敏度为1mm槽深天平的1.57倍,但准度有所下降。本研究为小量程气动载荷的测量提供新思路。 相似文献
352.
《中国航空学报》2021,34(5):666-683
The original free vortex wake model was used for numerical investigation. Calculation of the aerodynamic characteristics in hover and vertical descent modes in the range of vertical descent speed of 0–30 m/s including the Vortex Ring State (VRS) area was performed. The calculations were carried out under the condition of variable blade pitch angle values providing a fixed time-average thrust value. Visualization data of free vortex wake shapes, flow structures, and velocity fields were obtained and analyzed. The time-dependences of the rotor’s thrust and torque coefficients were obtained and analyzed. The obtained data allows determining the boundaries of the VRS area by various criteria such as rotor thrust and torque pulsations, growth of rotor power consumption relative to the hover, growth of rotor induced velocities relative to the hover, and growth of the required rotor blade pitch angles values. The results of the study are compared with experimental and calculated data of other authors and can significantly supplement the available results of experimental and computational studies in this area. 相似文献
353.
《中国航空学报》2021,34(11):254-266
This study aimed to explore the evolution of flow lines and microstructures of M50-steel bearing ring and the anisotropy of its tensile mechanical properties after Multi-Stage Hot Forging (MSHF) and subsequent spheroidizing annealing (MSHFA). To this end, the present study mainly employed stereo microscopy, Optical Metallurgical Microscopy (OMM), Scanning Electron Microscopy (SEM), and Electron Backscatter Diffraction (EBSD) to characterize and analyze the workpiece at each processing stage of MSHF while performing microhardness measurement and uniaxial tensile experiment to test and analyze the mechanical properties of the workpiece. Macro-structure observation showed that the simulation results of flow lines at each stage were consistent with the experimental results. Microscopic observation showed that, after MSHF, deformation gradually became less significant along the outward radial direction of the bearing ring. After MSHFA, the microstructures of the bearing ring became uniform, whereas primary carbides did not dissolve. The mechanical properties were better in the axial direction (AD) than in the radial (RD) and circumferential directions (CD) after MSHF due to the smaller grain width. After MSHFA, the mechanical properties in the ADs and CDs were better than those in the RDs, which was due to the large cross-sectional area of carbides along the flow-line direction. 相似文献
354.
在分析环件加工过程的运动和受力的基础上,定义了环件的端面平整度和外圆的圆度误差作为环件质量的表征参数。通过仿真,分析了环件轧制过程中芯辊进给速度、驱动辊转速和上锥辊进给速度与环件质量之间的关系。仿真结果为环件轧制工艺参数定义提供了参考。 相似文献
355.
本文论述 STD 总线双机容错系统的设计与实现,该系统为工矿企业提供高可靠性的处理机模块。本系统采用双机容错原理,模块内部包含两个CPU 协同工作,还可用同样的处理机模块作为热备份,当运行模块失效后系统能自动切换到备份模块运行,实现系统的不间断运行。文中最后讨论了系统的软硬件结构及主要实验结果。 相似文献
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359.
针对滑环失效数据较少的特点,构建导电滑环磨损失效模型,结合小子样数据处理法和随机性理论对滑环摩擦副进行可靠性评估研究。首先,考虑滑环摩擦副在热力电多场耦合环境下的特点,应用传热学、赫兹理论、能量守恒定律量化多场耦合对滑环摩擦副的影响,再结合Archard模型理论构建导电滑环摩擦副磨损失效模型。然后,采用小子样数据的虚拟增广法和Boot-strap法对仿真数据进行扩展,根据滑环磨损特征量分布规律分别得到随机失效阈值与固定阈值下的可靠度函数曲线,以某厂制造的导电滑环为例,进行滑环摩擦副可靠性评估,实验结果表明随机失效阈值下的可靠度与实际更接近。研究表明所构建的磨损模型和方法可以有效地对导电滑环进行可靠性评估,避免了传统的必须依赖大量试验数据的方法,解决了缺少滑环试验数据而难以进行可靠性评估的问题,填补了导电滑环可靠性研究的空白。 相似文献
360.
Stephen E. Ekwok Anthony E. Akpan Ebong D. Ebong Ohara E. Eze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(7):2104-2119
High resolution airborne magnetic data acquired between 2005 and 2010 were used to determine depth to shallow and deep magnetic sources in some parts of Southeastern Nigeria. Various depth estimation methods such as standard Euler deconvolution (SED), source parameter imaging (SPI), spectral depth analysis (SDA) and two dimensional (2-D) forward modeling were applied. Results obtained from SED, SPI and models of profiles 1 and 2 indicate that the Abakaliki Anticlinorium (AA) and Ikom-Mamfe Rift (IMR) regions are dominated by short wavelength magnetic anomalies caused by extensive tectonic events. The SED map showed depth to shallow and deep magnetic sources ranging from ~ 16.6 to ~ 338.3 m and ~ 394.3 to ~ 5748.1 m respectively. Likewise, depth estimates from the SPI map varies from ~ 147.1 to ~ 554.2 m (shallow magnetic sources) and ~ 644.2 to ~ 6141.6 m (deep magnetic sources). The result obtained from SDA revealed depths to deep magnetic basement in the range of ~ 769 to ~ 6666 m with an average of ~ 3449 m. Also, it showed that depth to shallow magnetic sources vary between ~ 119 and ~ 434 m with mean of ~ 269 m. The 2-D forward modelling showed maximum depth values of ~ 4700, ~4600 and ~ 6500 m in the models of profiles 1, 2 and 3 within the Anambra Basin (AB), Afikpo Syncline (AS) and Calabar Flank (CF) respectively. Generally, from all the various methods applied the results indicate that AB, AS and CF are dominated by long wavelength anomalies. The 2-D models indicated that the basement framework is undulant. Also, depth estimates involving the various methods used in this study correlate strongly with each other in the AB, AS and CF geological regions. 相似文献