电磁搅拌法连铸半固态铝合主其凝固组织分析

采用电磁搅拌连续铸造装置,制备具有触变性非合晶组织的兰固态铝合金圆棒。棒料内部组织形貌为具有类圆形轮廓的初生相晶粒浸润在细共晶体中,与传统的凝固枝晶组织有显著差异。对兰固态非枝晶组织的演化机理进行了探讨,结果表明处于交变电磁场中的金属液体,可视为导电介质流,它与磁场交互作用,在导电介质充中产生彻体力。半固态非枝晶组织是在晶体正常的形核和长大过程中,受彻体力强烈的混合抑制作用而形成的。     

等温处理对半固态ZA27组织演变的影响

采用加入微量元素锆对ＺＡ２７合金进行变质处理,并加热到液－固相区不同温度,采用不同时间进行等温处理,以观察所获得的ＺＡ２７合金半固态组织的演变规律。结果表明,经过变质处理后的合金在液－固相区不同温度保温时,具有以下的组织演变规律,树枝晶,碎块状,颗粒状,球状,晶粒长大。     

铝合金半固态触变压铸试验研究

通过对普通液态压铸机的改进和相关工艺参数的调整,使用Al—6Si-2Mg合金进行了半固态触变压铸试验研究．得到了冲型完好、组织均匀的水泵盖零件。     

激光淬火处理后半高速钢的组织及性能

采用横流CO₂激光器对半高速钢5Cr5MoSiV表面进行了激光淬火试验,并对淬硬层组织及性能做了研究。结果表明,半高速钢激光淬火层主要分为4个区域：完全淬火区,不完全淬火区,过渡区和基体。完全淬火区的显微组织为马氏体+残留奥氏体+少量碳化物。淬硬层显微硬度比基体显微硬度提高了1.5倍。激光功率与扫描速率的改变对淬火后的表面硬度影响较小,但功率或扫描速率的改变会对淬硬层深度产生明显影响。     

Hydrogel–silver nanoparticle composites: A new generation of antimicrobials

Design of consistant and eco‐friendly methods for the synthesis of silver nanoparticles (AgNPs) is a significant forward direction in the field of application of antibacterial bionanotechnology. One among the available options is hydrogel templates, which are highly useful to achieve this goal. This investigation involves the development of poly(acrylamide)/poly(vinyl alcohol) hydrogel–silver nanocomposites (HSNCs) to achieve AgNPs of ～2–3 nm size in gel networks. The nanocomposite synthesis process is quite convenient, direct, and very fast, and the obtained hydrogel AgNP composites can be used for antibacterial and wound dressing applications. All the nanocomposite aqueous solutions have shown absorption peaks at 420 nm in UV–visible absorption spectrum corresponding to the Plasmon absorbance of AgNPs. X‐ray diffraction spectrum of the HSNC exhibited 2θ values matching with silver nanocrystals. Transmission electron microscopy images of nanocomposites represent discrete AgNPs throughout the gel networks in the range of 2–3 nm. The developed nanocomposites were evaluated for antibacterial application on E. coli. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mg和半固态加工对A356合金显微组织和抗蠕变性能的影响

研究Mg和半固态加工对A356合金蠕变性能的影响。结果表明：位错攀移控制的蠕变是占主导地位的蠕变机制,它不会受到半固态加工以及进一步添加 Mg 的影响。Mg 提高合金的抗蠕变性能主要是由于在枝晶间区域形成大量汉字型的 Mg2Si。半固态加工的样品表现出比铸造样品更好的抗蠕变性能,这是由于 Mg 在α(Al)相中显著溶解所致堆垛层错能的减少而导致的。     

Rheological properties of poly(ethylene glycol)/poly(N‐isopropylacrylamide‐co‐2‐acrylamido‐2‐methylpropanesulphonic acid) semi‐interpenetrating networks

For the increasing demands of multifunctional materials in applications such as drug delivery system, a pH‐ and temperature‐responsive polyelectrolyte copolymer gel system was studied using rheometry. Rheological properties, determined by plate–plate rheometry in oscillatory shear, of hydrogels formed by free radical initiated copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) in the presence of methylene bisacrylamide (MBAA) as crosslinker are compared with the properties of semi‐interpenetrating network (SIPN) polyelectrolyte gels made by incorporation of poly(ethylene glycol) with molar mass 6000 g mol^?1 (PEG6000). Based on our systematic studies for this PEG/SIPN system, the effects of initiator and crosslinker concentration, relative proportions of comonomer units in the main chains, PEG6000 content and temperature on viscoelastic properties, unusual high storage moduli at small strain for the SIPN were discussed. The SIPN gel with characteristics of PEG molecules as well as pH and temperature responsiveness from AMPS and NIPA units has potential application in drug delivery system design. Ice‐like rheological behavior of the PEG/AMPS‐NIPA SIPN gels at low temperature was first time reported and water remains homogeneous without phase separation in PEG/AMPS‐NIPA SIPN hydrogels at low temperature may be considered as an ideal candidate for water storage material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

基于弹流理论的深槽密封机制分析

使用半光滑牛顿法建立深槽密封弹流模型,模型将雷诺方程、空化方程、力平衡方程及变形方程同时纳入牛顿迭代系统,使用Fischer-Burmeister函数实现对润滑液膜空化区域的识别,通过一重循环迭代寻索到空化区域并得到端面膜厚及压力场分布,算法效率显著提升。通过该弹流模型对深槽密封作用机制进行研究,并对比分析U型槽、矩形槽、圆弧槽3种型槽对密封性能的影响。结果表明:深槽密封端面周向较小的动力楔使得端面以非接触状态运行;核主泵三级密封的密封特性接近,圆弧槽在仅考虑压力变形条件下动压效应微弱,且稳定运行时其最小膜厚远小于U型槽及矩形槽。     

点接触混合润滑的数值求解方法

基于半系统法的统一Reynolds方程,对点接触混合润滑进行数值模拟。在流体润滑区,采用Reynolds方程求解流体压力,在固体接触区采用简化Reynolds方程求解压力。弹性变形使用离散卷积-快速傅里叶变换(DC-FFT)计算。为了加快迭代收敛速度,在数值求解过程中使用渐进网格加密(Progressive Mesh Densification,PMD)算法。数值模拟结果表明,该模型可以快速地求解光滑和粗糙表面条件下的各种润滑情况,包括全膜、混合和边界润滑;随着卷吸速度的增加,润滑状态从边界到混合再到全膜润滑是个光滑过渡的过程。     

履带车辆半主动悬挂二自由度计算机仿真实验

基于磁流变(MRF)减振器的履带车辆半主动悬挂系统，其阻尼力根据环境可控可调，从而能够完成对履带车辆振动的有效抑制。选用履带车辆二自由度1／2的车体模型，分别针对被动悬挂和半主动悬挂，建立了相应的数学模型。加上瞬时最优控制算法后，得出了悬挂系统的最优控制力。采用控制系统的分析和仿真软件Matlab中的Simulink工具箱进行了被动及半主动仿真实验。