Mn含量对2519铝合金的组织与力学性能的影响

通过显微硬度测试、拉伸测试、透射电镜及扫描电镜观察分析等手段研究了Mn含量对2519铝合金组织与力学性能的影响.研究结果表明,当Mn含量小于0.29wt%,合金的强度随Mn含量的增加逐渐增大;当Mn含量大于0.29wt%后,合金强度随Mn含量的增加却有所降低;随Mn含量的增加,合金170 ℃时效硬化速度逐渐加快,峰值时效时间提前,但合金的延伸率随Mn含量的增加而逐渐降低;当Mn含量大于0.29wt%,合金的时效硬化效果随Mn含量的增加而有所降低.综合考虑合金的强度和塑性,2519铝合金中的Mn含量以0.29wt%为宜.     

EB-PVD热障涂层对IC10合金高温持久性能的影响

采用电弧离子镀技术在IC10合金基体上制备NiCrAlYSi粘结层,采用电子束物理气相沉积(EB-PVD)技术在粘结层上制备YSZ陶瓷面层,研究TBCs涂层对IC10合金高温持久性能的影响.结果表明,IC10合金沉积TBCs涂层后,980℃高温持久寿命高于IC10合金,持久塑性略高于基体合金,IC10合金沉积TBCs涂层后,对高温持久性能无不良影响,满足使用要求.     

含孔平面编织混杂铺层层合板压缩性能

对含孔平面编织混杂铺层复合材料层合板的压缩性能进行试验研究,考察铺层比例和铺层顺序对其压缩破坏和压缩强度的影响, 然后利用点应力判据和平均应力判据进行层合板剩余压缩强度的估算.结果表明0°铺层比例的增加,提高了层合板的剩余压缩强度;(±45) 编织铺层比例在20%～25%之间有助于提高层合板的剩余压缩强度;点应力判据和平均应力判据适用于这种混杂铺层层合板的剩余压缩强度的估算.     

电阻型容性频率选择表面吸收体吸波性能研究

提出一种由Salisbury屏衍生而成的新型雷达吸波材料--电阻型容性频率选择表面(FSS)吸收体.采用有限元软件对吸波性能进行研究.研究表明,FSS单元方阻R,参数p和a以及介质层厚度h对FSS吸收体吸波性能均有较大影响.通过大量计算发现,FSS单元方阻在100～200Ω/□之间,p取0.05时具有较好的吸波性能.发现重要的"2h规则".指出在介质层厚度较大的情况下很难充分发挥FSS的作用,一般要求介质层厚度不大于5mm.通过实验对数值计算结果进行验证,结果表明两者基本吻合.另外,数值计算以及实验结果均表明,通过合理的参数选取,与Salisbury屏吸收体相比而言,FSS吸收体可在厚度较小的情况下实现低频吸收,并且具有较好的带宽特性.     

混合线性/非线性状态空间模型的边缘Rao-Blackwellized粒子滤波法(英文)

本文提出了边缘 Rao-Blackwellized 粒子滤波器(marginal Rao-Blackwellized particle filter, MRBPF)算法,算法融合了 Rao-Blackwellized 粒子滤波器(Rao-Blackwellized particle filter , RBPF)算法和边缘粒子滤波器(marginal particle filter, MPF)算法。算法中状态被分为线形和非线性两部分,分别用 MPF 和卡尔曼滤波器(Kalman Filter)进行估计。地形辅助导航(terrain aided navigation, TAN)的仿真结果表明,与 RBPF 相比,提出算法的非线性状态估计的误差均方根(root mean square error, RMSE)和误差方差分别降低了约 29%和 96%,独立粒子数提高了约80%,获得了更好的收敛结果。分析表明,现有RBPF是MRBPF的一个特例。     

Magnetic and Optical Properties of the TiO2-Co-TiO2 Composite Films Grown by Magnetron Sputtering

The TiO2-Co-TiO2 sandwich films were successfully grown on glass and silicon substrata making alternate use of radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and properties of these films were identified with X-ray diffraction (XRD), Raman spectra and X-ray photoemission spectra (XPS). It is shown that the sandwich film consists of two anatase TiO2 films with an embedded Co nano-film. The fact that, when the Co nano-film thickens, varied red shifts appear in optical absorption spectra may well be explained by the quantum confinement and tunnel effects. As for magnetic properties, the saturation magnetization, remnant magnetic induction and coercivity vary with the thickness of the Co nano-films. Moreover, the Co nano-film has a critical thickness of about 8.6 nm, which makes the coercivity of the composite film reach the maximum of about 1413 Oe.     

Effects of RRA Treatments on Microstructures and Properties of a New High-strength Aluminum-Lithium Alloy-2A97

A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments (RRA). Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and tensile tests were used to investigate the effects of RRA treatment on the microstructures and properties. DSC test reveals the reversion temperature range of the strengthening δ' (Al3Li)phase. The results show that the microstructure consists of δ' (Al3Li) phase, T1 (Al2CuLi) phase and θ"/θ'(Al2Cu) phase for 2A97 alloy treated by a triple-aging ora retrogression and re-aging treatment in the following order: (1) at 165 ℃×30 min, (2) at 220 ℃ or 240 ℃×15 min, (3) at 165 ℃×24 h. The plastic deformation, incorporated into the treatment after secondary high temperature aging, promotes the T1 precipitation during final re-aging. The tensile properties of the alloy treated by the retrogression and re-aging treatment reach the peak level of alloy single-aged at 165 ℃ in T6 temper.     

真空成型碳纤维/环氧树脂基复合材料性能研究

对固化温度、保温平台及隔离材料对真空成型碳纤维/环氧树脂基复合材料(CCF300/BA9913)的孔隙率和力学性能的影响进行了研究.结果 表明,在较高的固化温度(125℃保温2h)条件下,CCF300/BA9913固化后力学性能和耐湿热性能更加优异.同时在树脂最低黏度所处温度附近(85℃),增加0.5h的保温平台,有利...     

Tensile properties of a composite–metal single-lap hybrid bonded/bolted joint

Hybrid bonded/bolted (HBB) joint has been widely used in engineering practice because it can overcome the potential weakness of pure bonded and pure bolted joints. However, studies on HBB joint are still at the initial stage. In this paper, tensile properties of a composite–metal single-lap HBB joint was investigated experimentally. And a detailed finite element model (FEM) was established to simulate the tensile behavior of the joint. The model was verified by the experimental results. Then the damage propagation and load transfer mechanism were explored based on the FEM. The results show that the HBB joint can provide multi-load transmission paths and resist damage propagation in the adhesive. The HBB joint has higher strength and energy absorption capacity than the pure bonded joint. And the HBB joint has greater initial damage load and tensile stiffness than pure bolted joint. Adhesive fillets can obviously improve the tensile performances of the HBB joint. Lateral stiffness of the joint boundary and testing machine show obvious effects on tensile performances of single-lap hybrid joints.     

月球表面土壤温度仿真分析

文章尝试对月表一定深度的土壤的温度变化状况进行模拟分析。首先简要介绍了月壤热物性的探测结果,针对月球表面具有一定深度的土壤层建立了土壤温度变化的一维数学控制方程,探讨了数值求解的方法,并根据月壤探测样本的文献对热物性参数进行了归纳。最后对5个着陆区进行了月壤温度计算和结果分析,以协助深空探测工作的开展。