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电子束焊接TC4整体叶盘结构的变形控制 总被引:1,自引:0,他引:1
基于电子束焊接方法,探讨了TC4钛合金整体叶盘结构电子束焊接过程中的变形控制方法,提出了综合应用焊接工艺优化、刚性固定、真空热处理和电子束局部加热相结合的变形控制方法,有效地控制了焊接变形,实现了电子束焊接整体叶盘结构的制造. 相似文献
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电子束焊接薄板过程中,由于局部加热过快,易产生焊接变形。因此,在电子束焊接的主热源两侧引入基于高频扫描技术的电子束辅助热源,进行焊前预热,以达到减小焊接变形的目的。建立了矩形均匀加热辅助热源模型,采用热弹塑性有限元分析方法对1.5mm厚不锈钢薄板随行辅助预热电子束焊接进行数值模拟,并且进行了试验验证。结果表明,焊后残余应力和变形的模拟结果与试验所得结论一致。电子束焊接随行辅助预热方法不仅可以改变熔池前方材料的应力状态,而且当熔池形成瞬间熔池时,还可以减小前方材料的压应力峰值,有利于减小薄板结构的焊接变形。 相似文献
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近年来焊接技术发展很快,电子束焊、激光焊、等离子束焊等新的加工技木日趋完善,随着计算机的应用,焊接的自动化水平日益提高,这些都有力地促进了航空工业的发展.一、电子束焊电子束焊工艺,是使用被聚焦的电子束作为热源的焊接方法,是50年代由德国蔡斯公司及法国原子能委员会发展起来的.它可以进行活性金属、难熔材料、轻金属、高级合金等多种材料的焊接,特别是开发了局部真空电子束焊及非真空电子束焊接以后,应用范围更加广泛.电子束焊接工艺的优点是焊接变形小,焊透深宽比高,焊速高,还可进行预加工和热处理后元件的焊接,以及极薄和极厚元件的焊接. 相似文献
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对高温合金GH4169/GH907异种材料的电子束焊接进行了研究,探讨了一定厚度范围内的GH4169和GH907电子束焊接的差异和焊接工艺参数,并对焊接缺陷及热处理对焊缝某些性能的影响进行了研究。 相似文献
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为了探讨先进旋涡燃烧室流动传热特性,基于场协同原理,对不同来流速度、来流温度、壁面温度及燃气当量比下燃烧室的速度场、温度场及其场协同角分布进行了数值模拟。结果表明,协同角较小的区域主要分布在后钝体后侧、凹腔内部以及进气通道横向中心截面上。旋涡区可以强化换热。随着来流速度及来流温度的增大,场平均协同角呈递减趋势;随着壁温的提高,场平均协同角增大;当量比小于1.0时,场平均协同角随着当量比的增大而增大,而达到1.0之后变化不明显。对于速度场与温度场,燃烧室中心截面的场协同性能最好,且体平均协同角大于面平均协同角。 相似文献
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Cross field diffusion of energetic particles (cosmic rays) in a two-dimensional static magnetic field turbulence is studied
performing test particle simulations. Qualitatively different diffusion processes are observed depending on the ratio of Larmor
radius (ρ) to the correlation length (λ) of the magnetic field fluctuations. The diffusion is found to be composed of several
regimes with distinct statistical properties, which can be characterized using Levy statistics.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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The Magnetic Field of Mercury 总被引:1,自引:0,他引:1
Brian J. Anderson Mario H. Acuña Haje Korth James A. Slavin Hideharu Uno Catherine L. Johnson Michael E. Purucker Sean C. Solomon Jim M. Raines Thomas H. Zurbuchen George Gloeckler Ralph L. McNutt Jr. 《Space Science Reviews》2010,152(1-4):307-339
The magnetic field strength of Mercury at the planet’s surface is approximately 1% that of Earth’s surface field. This comparatively low field strength presents a number of challenges, both theoretically to understand how it is generated and observationally to distinguish the internal field from that due to the solar wind interaction. Conversely, the small field also means that Mercury offers an important opportunity to advance our understanding both of planetary magnetic field generation and magnetosphere-solar wind interactions. The observations from the Mariner 10 magnetometer in 1974 and 1975, and the MESSENGER Magnetometer and plasma instruments during the probe’s first two flybys of Mercury on 14 January and 6 October 2008, provide the basis for our current knowledge of the internal field. The external field arising from the interaction of the magnetosphere with the solar wind is more prominent near Mercury than for any other magnetized planet in the Solar System, and particular attention is therefore paid to indications in the observations of deficiencies in our understanding of the external field. The second MESSENGER flyby occurred over the opposite hemisphere from the other flybys, and these newest data constrain the tilt of the planetary moment from the planet’s spin axis to be less than 5°. Considered as a dipole field, the moment is in the range 240 to 270 nT-R M 3 , where R M is Mercury’s radius. Multipole solutions for the planetary field yield a smaller dipole term, 180 to 220 nT-R M 3 , and higher-order terms that together yield an equatorial surface field from 250 to 290 nT. From the spatial distribution of the fit residuals, the equatorial data are seen to reflect a weaker northward field and a strongly radial field, neither of which can be explained by a centered-dipole matched to the field measured near the pole by Mariner 10. This disparity is a major factor controlling the higher-order terms in the multipole solutions. The residuals are not largest close to the planet, and when considered in magnetospheric coordinates the residuals indicate the presence of a cross-tail current extending to within 0.5R M altitude on the nightside. A near-tail current with a density of 0.1 μA/m2 could account for the low field intensities recorded near the equator. In addition, the MESSENGER flybys include the first plasma observations from Mercury and demonstrate that solar wind plasma is present at low altitudes, below 500 km. Although we can be confident in the dipole-only moment estimates, the data in hand remain subject to ambiguities for distinguishing internal from external contributions. The anticipated observations from orbit at Mercury, first from MESSENGER beginning in March 2011 and later from the dual-spacecraft BepiColombo mission, will be essential to elucidate the higher-order structure in the magnetic field of Mercury that will reveal the telltale signatures of the physics responsible for its generation. 相似文献
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Variations of the geomagnetic field over past millennia can be determined from archeomagnetic data and paleomagnetic sediment records. The resolution and validity of any field reconstruction depends on the reliability of such indirect measurements of past field values. Considerable effort is invested to ensure that the magnetic minerals carrying the ancient magnetization are good, if not ideal, recorders of the magnetic field. This is achieved by performing a wide array of rock magnetic and microscopy investigations, many of which are outlined here. In addition to data quality, the spatial and temporal distributions of archeomagnetic and sediment records play a significant role in the accuracy of past field reconstruction. Global field reconstructions enable studies of dynamic processes in Earth’s core. They rely on data compilations which ideally include information about the quality of a measurement and provide a useful archive for selecting data with the best characteristics. There is, however, a trade off between the total number of reliable data and the geographic or temporal coverage. In this review we describe the various types of paleomagnetic recorders, and the kind of measurements that are performed to gather reliable geomagnetic field information. We show which modeling strategies are most suitable, and the main features of the field that can be derived from the resulting models. Finally, we discuss prospects for progress in this kind of research. 相似文献
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《航空材料学报》2015,(5)
采用数值模拟的方法对一种低压双层雾化器(Double Layer Atomizer)气流场和雾化过程进行了研究,分析了上层雾化器对气流循环区域以及金属液流雾化的影响。结果表明:上层雾化器的引入能有效抑制气流循环区域的不良影响,有利于金属液流的稳定流动;考虑到上层雾化器压力的增大会引起气流循环区域压力的增大以及流量的增加,选择0.15MPa/0.68MPa~0.2MPa/0.68MPa的压力条件较为有利;该双层雾化器液流破碎过程存在一定的类似于紧密耦合式雾化器(Close-Coupled Atomizer)的膜状破碎方式,破碎液滴在空间飞行发散范围和其粒径大小有关。 相似文献