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排序方式: 共有93条查询结果,搜索用时 15 毫秒
1.
《中国航空学报》2020,33(7):2043-2054
Finite element modeling (FEM), microscopy, X-ray computed tomography (CT) and mechanical property tests were used to study the microstructure, porosity and mechanical properties of an AlSi10Mg alloy produced by selective laser melting (SLM). The simulation of the melt pool and thermal history under different energy densities produced an optimized result with an energy density of 44.5 J·mm−3. The high cooling rate during the SLM process significantly refined the previous α-Al dendrites. The growth direction of the network-like Al-Si eutectic structure at different orientations confirmed the anisotropic nature of the microstructure. Furthermore, the microhardness, tensile testing and fracture analysis results proved that there were no obvious distinctions in the strength between the transverse and longitudinal directions, and that the ductility was anisotropic, possibly due to the shape and distribution of the pores. The pores measured by X-ray CT at different energy densities confirmed that the sphericity of the pores was inversely related to pores volumes. With optimized processing conditions, the porosity of the selective laser melted sample decreased leading to the improved fabricated fuel system component via SLM. 相似文献
2.
非重力阻尼的连续、快速、高精度补偿是实现重力梯度测量卫星精细重力场测量的关键技术之一,直接影响到整星工程任务的成败。针对重力梯度测量卫星在轨飞行期间对电推进系统宽范围连续变推力能力的应用需求,分析了10cm氙离子推力器推力调节响应特性。在此基础上,通过对阳极电流、励磁电流和阳极流率等推力高敏感响应参量的组合调节,开展了推力调节试验研究,验证了10cm氙离子推力器宽范围连续变推力调节能力,获得了1~20mN范围内的推力调节性能及其变化规律。试验结果表明:在采用地面供电、供气设备条件下,10cm氙离子推力器能够在100~597W的功率范围内实现0.98~20.29mN的推力宽范围调节,比冲175~3500s,推力分辨率优于50μN。研究为建立10cm氙离子电推进系统的推力控制数学模型及调节控制算法奠定基础。 相似文献
3.
采用显微硬度和力学性能测试及金相显微镜、扫描电镜、透射电镜、X射线衍射等分析手段,研究了Zn含量对Mg-10Gd-4.8Y-0.6Zr合金挤压以及时效处理后合金组织和力学性能的影响。结果表明,在Mg-10Gd-4.8Y-0.6Zr合金中添加Zn元素,有利于细化合金晶粒,提高挤压态的强度。未添加Zn的合金T5态晶粒尺寸约为25μm,添加1%(质量分数,下同)Zn后,晶粒尺寸约为15μm,Zn含量为3%时,晶粒尺寸约为10μm。当Zn含量为1%时,合金挤压态和时效态的抗拉强度分别为337MPa,397MPa,屈服强度分别为128MPa,148MPa,伸长率分别为10.0%,5.0%,具有较好的综合性能。 相似文献
4.
围绕某型号姿控动力系统减压阀性能测试需求,提出一种基于PC104总线测试架构的设计方案。详细阐述了减压阀性能测试原理、硬件设计方案和软件开发思路,着重介绍了软件开发需求、总体架构、用户程序开发思路和软件设计关键技术等。实际应用表明,该系统操作简单、携带方便,测试精度优于0.2%,控制定时精度优于1 ms,满足减压阀性能测试要求。 相似文献
5.
D. Bisht Shashikiran Ganesh R.K.S. Yadav Alok Durgapal Geeta Rangwal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):571-580
The astrophysical parameters have been estimated for two unstudied open star clusters Teutsch 10 and Teutsch 25 using the Two Micron All Sky Survey () database. Radius is estimated as 4.5 arcmin for both clusters using radial density profiles. We have estimated proper motion values in both RA and DEC directions as and ?mas?yr?1 for Teutsch 10 and and ?mas?yr?1 for Teutsch 25 using 1 catalog. By estimating the stellar membership probabilities, we have identified 30 and 28 most likely members for Teutsch 10 and Teutsch 25 respectively. We have estimated the reddening as ?mag for Teutsch 10 and ?mag for Teutsch 25, while the corresponding distances are and ?kpc. Ages of ?Myr for Teutsch 10 and ?Myr for Teutsch 25 are estimated using the theoretical isochrones of metallicity Z?=?0.019. The mass function slopes are derived as and for Teutsch 10 and Teutsch 25 respectively. Estimated mass function slope for both the clusters are close to the Salpeter value () within the errors. Estimated values of dynamical relaxation time are found to be less than cluster’s age for these objects. This concludes that both objects are dynamically relaxed. The possible reason for relaxation may be due to dynamical evolution or imprint of star formation or both. 相似文献
6.
李金猛 《长沙航空职业技术学院学报》2010,10(3):53-56,79
介绍用于自动控制设备控制板卡的软硬件设计方法,采用混合输入(包括SCH和VHDL)实现该设计,重点阐述应用ISP开发软件采用VHDL语言实现整个软件接收、控制部分,测试表明设计方法合理有效。 相似文献
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9.
Windows下微机与数字化仪信息交换的研究 总被引:1,自引:1,他引:1
本文探讨了美国Borland公司95年最新推出的面向对象编程软件Delphi,实现计算机windows环境下与单片机控制的数字化仪信息交换,并在出口德国的超声浓度计及南昌公安交通地图查询系统上调试成功,对智能化电子仪表,CAD,CAM,计算机控制系统等领域有一定的意义。 相似文献
10.
André Balogh Réjean Grard Sean C. Solomon Rita Schulz Yves Langevin Yasumasa Kasaba Masaki Fujimoto 《Space Science Reviews》2007,132(2-4):611-645
Mercury is a very difficult planet to observe from the Earth, and space missions that target Mercury are essential for a comprehensive
understanding of the planet. At the same time, it is also difficult to orbit because it is deep inside the Sun’s gravitational
well. Only one mission has visited Mercury; that was Mariner 10 in the 1970s. This paper provides a brief history of Mariner
10 and the numerous imaginative but unsuccessful mission proposals since the 1970s for another Mercury mission. In the late
1990s, two missions—MESSENGER and BepiColombo—received the go-ahead; MESSENGER is on its way to its first encounter with Mercury
in January 2008. The history, scientific objectives, mission designs, and payloads of both these missions are described in
detail. 相似文献