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991.
基于无扩口组合导管连接强度试验详细介绍了用于该试验的夹具设计过程。该夹具解决了以往连接强度试验时,万能试验机夹头对试验管壁所产生的径向挤压作用力的问题,避免了对试验管件的径向挤压所造成的变形损坏,并通过开展无扩口导管组件连接强度试验,证明该种夹具具有高效、经济、简单、实用的特点,可以推广应用于各类液压导管的连接强度试验。 相似文献
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空气耦合式超声波无损检测技术具有完全非接触、无损伤的特点,可用于传统超声检测手段难以适应的场合。本文介绍了空气耦合式超声检测技术的发展历程和主要难点,总结了该技术近几年的实际应用情况,分析了该技术的局限性。 相似文献
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Traditional coning algorithms are based on the first-order coning correction reference model. Usually they reduce the algorithm error of coning axis (z) by increasing the sample numbers in one iteration interval. But the increase of sample numbers requires the faster output rates of sensors. Therefore, the algorithms are often lim- ited in practical use. Moreover, the noncommutivity error of rotation usually exists on all three axes and the in- crease of sample numbers has little positive effect on reducing the algorithm errors of orthogonal axes (x, y). Considering the errors of orthogonal axes cannot be neglected in the high-precision applications, a coning algorithm with an additional second-order coning correction term is developed to further improve the performance of coning algorithm. Compared with the traditional algorithms, the new second-order coning algorithm can effectively reduce the algorithm error without increasing the sample numbers. Theoretical analyses validate that in a coning environ- ment with low frequency, the new algorithm has the better performance than the traditional time-series and fre- quency-series coning algorithms, while in a maneuver environment the new algorithm has the same order accuracy as the traditional time-series and frequency-series algorithms. Finally, the practical feasibility of the new coning al- gorithm is demonstrated by digital simulations and practical turntable tests 相似文献
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A monitoring and comparison experiment with two types of sensors on a turbojet engine is carried out. Compared with a probe-typed sensor, which is designed successfully before, signals are collected to verify the va- lidity and better feasibility of the circular sensor. According to the signals monitored over 131 h, the typical signals of 125--129 phases are analyzed. The results show that the unusual exhaust particles are carbon depositions from fuel spray nozzle. Therefore, with the electrostatic sensor, early warning can be provided for initial fault condition, as well as real-time reference for the condition-based maintenance. 相似文献
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The surface performances of directly fluorinated high density polyethylene (HDPE) are studied with Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM) and contact angle (CA) system. The SEM images show that there is a three-layer structure called the reaction, virgin and boundary layer structure. The depth of fluorinated layer is 5.75 ~m with 1 h fluorination time and 7.86 b~m with 2 h. The depths are 5.46 /~m and 5.07 /~m when fluorine density is 2G and 1~/0, respectively. CA indicates that the HDPE surface property becomes more hydrophobic with the increasing water contact angle from 78.5~ to 104.5~. Oleophobic and hydrophobic features of HDPE are identified by comparison of mass change experiments. It is shown that the in- crement rate of fluorinated HDPE is much lower than that of un-fluorinated HDPE filled in neither distilled water nor jet fuel. 相似文献
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金佳林高超张正科 《南京航空航天大学学报》2017,49(S1):1-5
以开孔壁翼型风洞为研究对象,构建简化的仿真模型,模拟开风洞孔壁附近及小孔内的流动,研究开孔壁对风洞试验的影响。研究了开孔壁流动的主要特征参数并建立多孔板模型,为进一步建立数值风洞模型及研究洞壁干扰提供参考。通过简化的孔壁模型,研究了开闭比等特征参数对风洞流场和翼型绕流的影响。构建了二维简化孔壁模型和多孔介质孔壁模型,并验证了以多孔板模型模拟孔壁风洞流场的可行性。本文建立了一种研究跨声速孔壁风洞的孔壁效应的数值方法,为跨声速孔壁风洞流场的模拟研究提供参考,为进一步构建可靠的风洞孔壁数值模拟数学模型提供一种研究思路。 相似文献