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排序方式: 共有448条查询结果,搜索用时 15 毫秒
1.
介绍TC4(Ti-6Al-4V)钛合金螺栓孔无衬套冷胀孔干涉配合综合强化的研究结果。实验证明,在给定的条件下,冷胀孔强化的TC4板状空孔试件的疲劳寿命增益系数(LIF)为13,干涉配合螺栓连接的LIF=3,而E-l强化件的疲劳寿命比单纯干涉配合又有成倍提高。电镜断口分析表明TC4合金强化件的疲劳裂纹的形成和扩展与LY12CZ及30CrMnSiA相似,它们不表现为典型的角裂纹,即沿板平面和厚向扩展速率有明显差异。对于TC4合金,在改善疲劳品质上,带衬套冷胀孔强化比无衬套冷胀孔强化好得多。 相似文献
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异型孔空心叶片壁厚检测的试验研究 总被引:2,自引:0,他引:2
发动机叶片的结构型式和制造误差,直接影响发动机的性能和使用寿命。运用超声波法和电涡流法,对两种不同材料和形式的试件进行了试验。电涡流法受到探头直径和试件几何尺寸的影响,测量误差大,超声波法由于存在测量盲区,测量厚度的下限受到限制。但测量值与实际值相关,若对探头加以改进,用于异型孔空心叶片壁厚检测是可行的。 相似文献
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N. Kylafis D. Giannios D. Psaltis 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2810-2812
We propose a jet model for the low/hard state of galactic black-hole X-ray sources which explains the energy spectra from radio to X-rays and a number of timing properties in the X-ray domain such as the time lag spectra, the hardening of the power density spectra and the narrowing of the autocorrelation function with increasing photon energy. The model assumes that (i) there is a magnetic field along the axis of the jet, (ii) the electron density in the jet drops inversely proportional to distance, (iii) the jet is “hotter” near its center than at its periphery, and (iv) the electrons in the jet follow a power-law distribution function. We have performed Monte Carlo simulations of Compton upscattering of soft photons from the accretion disk and have found power-law high-energy spectra with photon-number index in the range 1.5–2 and cutoff at a few hundred keV, power-law time lags versus Fourier frequency with index 0.8, and an increase of the rms amplitude of variability and a narrowing of the autocorrelation function with increasing photon energy as they have been observed in Cygnus X-1. The spectrum at long wavelengths (radio, infrared, optical) is modeled to come from synchrotron radiation of the energetic electrons in the jet. We find flat to inverted radio spectra that extend from the radio up to about the optical band. For magnetic field strengths of the order 105–106 G at the base of the jet, the calculated spectra agree well in slope and flux with the observations. 相似文献
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《中国航空学报》2016,(2):560-570
Single-crystal superalloys are typical advanced materials used for manufacturing aeroengine turbine blades. Their unique characteristics of high hardness and strength make them exceedingly difficult to machine. However, a key structure of a turbine blade, the film-cooling hole,needs to be machined in a single-crystal superalloy; such machining is challenging, especially considering the increasing levels of machining efficiency and quality demanded by the aeroengine industry. Tube electrode high-speed electrochemical discharge drilling(TSECDD), a hybrid technique of high-speed electrical discharge drilling and electrochemical machining, provides high machining efficiency and accuracy, as well as eliminating the recast layer. In this study, TSECDD is used to machine a film-cooling hole in a nickel-based single-crystal superalloy(DD6). The Taguchi methods of experiment are used to optimise the machining parameters. Experimental results show that TSECDD can effectively drill the film-cooling hole; the optimum parameters that give the best performance are as follows: pulse duration: 12 ls, pulse interval: 30 ls, peak current:6 A, and salt solution conductivity: 3 m S/cm. Finally, a hole is machined by TSECDD, and the results are compared with those obtained by electrical discharge machining. TSECDD is found to be promising for improving the surface quality and eliminating the recast layer. 相似文献
6.
基于瞬态液晶测量技术的收缩-扩张形孔 总被引:2,自引:2,他引:2
采用一种进行全表面测量的瞬态液晶测量技术测量了新型气膜孔(收缩-扩张形孔)的气膜冷却特性,研究了动量比对冷却效率和换热系数的影响,并与传统的圆柱形孔气膜冷却特性进行了对比,结果表明:收缩-扩张形孔中心线附近区域的冷却效率相对较低,而两孔之间区域的冷却效率相对较高,与圆形孔分布规律相反;在上游区域,两孔中间区域的换热系数比相对孔中心线附近区域较高,而在下游区域,两孔中间区域的换热系数比相对孔中心线附近又较低,与圆形孔相比也有较大不同。相对于圆柱形孔,收缩缝形孔的平均换热系数比在上游较高,在下游较低;收缩-扩张形孔喷出气膜对下游壁面区域的有效覆盖率远大于圆柱形孔,其展向平均冷却效率明显高于圆柱形孔;收缩-扩张形孔在动量比为2时的平均冷却效率最高。 相似文献
7.
Li Guangchao Zhu Huiren Fan Huiming Department of Aeroengines Northwestern Polytechnical University Xi’an China 《中国航空学报》2008,21(5):385-392
Discharge coefficients of 3-in-1 hole of three inclination angles and three spacing between holes are presented which described the discharge behavior of a row of holes. The inlet and outlet of the 3-in-1 hole both have a 15° lateral expansion. The flow conditions considered are mainstream turbulence intensities and density ratios of secondary flow to mainstream. The momentum flux ratios varied in the range from 1 to 4. The comparison is made of the discharge coefficients of three shaped holes to find an optimal hole with low flow loss. The results show that the discharge coefficients of 3-in- 1 hole are highest in three shaped holes and therefore this article is focused on the measurements of discharge coefficients of 3-in-1 hole for various geometries and aerodynamic parameters. The measured results of 3-in-1 hole indicate that turbulence intensities, density ratios and momentum flux ratios have weak influence on discharge coefficients for inclination angle of 20°. The high turbulence intensity yields the small discharge coefficients for inclination angle of 45° and 90°. The increased both momentum flux ratios and density ratios lead to the increased discharge coefficients for inclination angle of 45° and 90°. The increased inclination angle causes the rapidly increased discharge coefficients. There is a weak dependence of discharge coefficients on hole pitches. 相似文献
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针对燃气轮机转子的非连续性结构间存在的接触特性,根据微凸体理论引入接触刚度和接触热阻的等效模型,建立了某型燃气轮机非连续性转子的动力学模型,分析了接触参数对转子稳、瞬态动力学特性的影响,研究了螺栓松动引起的转子热变形及其对转子快速启动过程中振动特性的影响.结果表明:预紧力、接触面的表面粗糙度和螺栓个数对转子临界转速有一定的影响,螺栓松动导致转子在启动过程中瞬态热变形最大达到7μm,过1阶临界转速时引起的转子最大响应幅值增大约30μm.在非连续性转子系统的热致振动特性分析当中,不应忽视接触参数、接触刚度和接触热阻的影响. 相似文献