共查询到20条相似文献,搜索用时 93 毫秒
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采用将有限声束分解为一系列平面波的方法,对有限声束在液体-固体板-液体结构中的声反射问题进行了分析和计算。当有限声束以平面波反射系数相位为180°时的入射角入射时,在固体板表面反射的声束沿板表面存在显著的移动和展宽现象。本文的有关结果,对进一步研究有限声束在板状结构表面的声反射具有积极意义。 相似文献
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复杂结构的声辐射解耦及其声辐射效率分析 总被引:5,自引:0,他引:5
提出一种用边界元方法与声辐射理论求解复杂结构的声辐射模态与声辐射效率的理论方法。先将结构的声辐射功率表示为一个正定的厄米特二次型,运用广义特征值分解求解了复杂结构的声辐射模态,然后利用声辐射模态关于阻抗矩阵与均方速度耦合矩阵的正交性,求解了复杂结构的声辐射效率,最后用具有解析解的脉动球与辐射立方体验证了该方法的有效性。 相似文献
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基于代数网络和混沌参数的碰摩声发射源定位方法研究 总被引:1,自引:0,他引:1
针对时差定位法受不同模式波速度差异及波形传播畸变等因素影响的问题,将神经网络技术应用到声发射源定位中.为了克服传统BP算法训练时间长和精度不够高的缺点,提出代数神经网络概念,在网络训练阶段引入代数算法.将复杂的非线性优化问题转化为简单的代数方程组求解问题,直接获得最优点,大大缩短了网络的学习时间.同时作为定位特征研究分析了转子碰摩声发射信号的非线性动力学特性,提出了关联维数、最大Lyapunov指数和Kolmogoroy熵等声发射源的非线性动力学新特征,并将其作为神经网络的输入定位特征.实验结果表明,利用这些声发射源的非线性动力学特征和神经网络结合能较好地解决了碰摩声发射源定位问题,为转子碰摩故障诊断提供依据,具有良好的应用前景和进一步研究的价值. 相似文献
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《Materials Science and Engineering: A》2003,339(1-2):241-244
Cryogenic treatment has been claimed to improve wear resistance of certain steels and has been implemented in cutting tools, autos, barrels etc. Although it has been confirmed that cryogenic treatment can improve the service life of tools, the underling mechanism remains unclear. In this paper, we studied the microstructure changes of M2 tool steel before and after cryogenic treatment. We found that cryogenic treatment can facilitate the formation of carbon clustering and increase the carbide density in the subsequent heat treatment, thus improving the wear resistance of steels. 相似文献
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In the present investigation the Al–5.5Mg–0.02Ti alloy produced by twin roll casting (TRC) process (varying rolling speed, i.e., 3, 4, and 5 rpm) has been subjected to heat treatment for microstructure modification. Grain coarsening at the center of the strip has been observed during heat treatment process. Homogeneous microstructure of the alloys has been achieved by heat treatment process, and it has been found that the time to achieve homogeneous structure depends on the rolling speed. Transmission electron microscope (TEM) studies revealed that undesired Mg rich phase (Mg5Al8) has been successfully eliminated by heat treatment process. Fine and equi-axed grains in the alloys obtained by heat treatment process shows high strength and elongation. 相似文献
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铝及铝合金表面处理研究进展 总被引:4,自引:2,他引:2
铝合金耐磨性差、特殊条件下耐蚀性差的缺点限制了它的进一步利用,对铝合金进行表面处理长期以来一直是扩大铝合金使用范围地行之有效的方法.文章综述了铝合金的各种表面处理方法,比较了它们的优缺点,指出表面氧化是铝合金表面处理的主流,复合处理、纳米化处理将是今后铝合金表面处理的主要研究方向. 相似文献
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《Materials Science & Technology》2013,29(6):607-614
AbstractAn investigation into the partial recrystallisation that occurs during solution treatment of hot rolled thick aluminum alloy 7050 plate has been performed for three alloy variants with different zirconium concentrations. Electron backscattered diffraction has been used to study the grain and subgrain structure in the as rolled condition and after solution treatment. Localised recrystallisation in the grain boundary regions during solution treatment has been largely attributed to the stimulating effect of large intermetallic particles on the boundaries, combined with the low number density of pinning dispersoids close to the grain edges. A model that predicts the dispersoid distribution across a grain has been applied to predict the fraction of recrystallisation after solution treatment. It has been demonstrated that the recrystallised fractions predicted by the model show good agreement with those measured experimentally. Example calculations are presented showing the predicted effect of the zirconium level, homogenisation conditions, and subgrain size on the recrystallised fraction. 相似文献
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Processing of materials at cryogenic temperature has improved the properties of materials such as hardness, toughness, wear resistance, tensile strength, dimensional stability, corrosion resistance, etc. However, the extent of improvement in the properties of materials subjected to cryogenic treatment as claimed in the literature is diverse and sometimes contradictory to each other. Contradictions have also been reported regarding its various aspects like tempering prior and postcryogenic treatment, tempering temperature, aging before cryogenic treatment and cryogenic parameters like soaking temperature, soaking time, and cooling rate. There is need of investigating the cryogenic treatment in relation to pre and postheat treatment conditions. In this study, an attempt has been made to review the various research articles published in the literature on the subject matter extensively. Cryogenic processing of cutting tools and workpiece material has also emerged as a potential technique for improving the performance of cutting tools during metal cutting as well as for improving the machinability and weldability of workpiece materials. The implications of cryogenic treatment in the perspective of manufacturing have been revealed clearly through review of related studies. The various findings reported in the literature have been highlighted systematically and futuristic directions have been proposed to encourage research work in the area of cryogenic treatment. 相似文献
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The influence of magnetic treatment parameters on the rheological properties of oils has been investigated. It has been noted
that the strongest effect on these properties is produced by the regime of magnetic treatment — steady-state or flowing, the
volume rate of oil flow, and the induction value of the magnetoactivator magnetic field. The optimal regimes of magnetic treatment
have been determined. It has been shown that treatment of oil with a magnetic field promotes a decrease in the solidification
temperature and the amount of asphalt-resin deposits.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 102–109, January–February, 2006. 相似文献
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Electrocoagulation of methylene blue and eosin yellowish using mild steel electrodes 总被引:3,自引:0,他引:3
The paper presents the study of electrocoagulation (EC) of aqueous dye solutions of two different industrial dyes in a batch stirred cell. Experiments were carried out with 200 mg/l individual concentration of methylene blue (MB) and eosin yellowish (EY) in presence of NaCl as electrolyte. Effect of operating time and current density on the decolorization of dye solutions, reduction of chemical oxygen demand (COD) and variation in conductivity, pH during treatment has been studied. Small difference between color diminution and COD reduction has been found with the progress of treatment. First-order rate equation for dye removal has been developed from the experimental results. Sludge formation during EC and problems associated with this solid waste generation and disposal has been assessed. Energy consumption in KWh/m(3) with reduction of COD (kg) during treatment has been reported. Electric power consumption of 1.5 KWh reduces 0.21 and 0.11 kg COD from 0.24 and 0.14 kg of initial COD for MB and EY, respectively, starting from 200 mg/l dye concentration. 相似文献
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This paper reports the effect of post weld heat treatment on fatigue behaviour of electron beam welded AA2219 aluminium alloy. An attempt has been made to enhance the fatigue strength of the electron beam welded joints through post weld heat treatment methods such as solution treatment, artificial aging, solution treatment and artificial aging. Electron beam welding machine with 100 kV capacity has been used to fabricate the square butt joints. Servo hydraulic controlled fatigue testing machine with a capacity of 100 kN has been used to evaluate the fatigue life of the welded joints. Of the three post weld heat treated joints, the solution treated and aged joints are enduring higher number of cycles under the action of cyclic loads. 相似文献
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P. He Z. M. Chen W. G. Chen G. L. Kuang Z. Y. Chen P. C. Huang 《Journal of Superconductivity and Novel Magnetism》2012,25(6):1805-1810
The design and fabrication of the model coil for the 40 T hybrid superconducting outsert has been completed at High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL). ??Wind-and-React?? method is adopted to ease subsequent handling and assembly and to protect the brittle material. The model coil which is made of Nb3Sn CICC will undergo a high temperature diffusion reaction according to the optimum heat treatment schedule for the Nb3Sn/RRP? superconducting strand. The facility specialized in the heat treatment of Nb3Sn superconducting coils has been established in CHMFL, and several kinds of monitoring instruments are equipped to monitor impurities in the argon gas during heat treatment. At present, the heat treatment of the model coil has been finished and the performance test results of the model coil meet our requirements. This paper mainly presents the introduction of the heat treatment facility, details of heat treatment process for the model coil, and some simulations of the states during heat treatment. 相似文献
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研究了热处理工艺对50.6at%Ni-Ti合金丝材弯曲疲劳性能的影响。结果表明:该丝材经过固溶和时效后具有不同的弯曲疲劳寿命,其中固溶处理温度为1023K并且时效温度673K时,具有最高寿命;抗拉强度随热处理工艺的改变呈同样变化趋势。 相似文献