二元复合结构聚合物涂层的减阻机理研究

对二元复合结构聚合物涂层阻力特性与形貌特征参数之间的关系进行了实验研究,并采用计算流体力学方法对形貌效应作用下形貌壁面的阻力特性进行了数值模拟,在此基础上讨论了聚合物涂层的减阻机理。结果表明,一阶形貌特征长度以及二阶形貌分布密度对聚合物涂层的减阻性能有显著影响;在来流条件下,聚合物涂层在二元复合结构表面形貌效应作用下,近壁面流场出现涡结构和流动分离现象,导致相应区域内的流场发生漩涡空化,促使二阶凹坑内驻留的微气泡生长形成气膜,在固/液界面间构建出气相结构,以气/液剪切代替固/液剪切实现界面效应减阻,有效降低了形貌壁面的摩擦阻力。     

微米结构聚合物涂层的制备及减阻性能研究

采用高压空气喷涂工艺,制备了一种聚合物涂层。利用白光干涉表面形貌仪对涂层表面形貌进行了表征,结果表明该涂层表面具有微米级凹坑结构。根据表面元素分析的结果,说明了涂层表面形貌形成的机理。通过小型高速水洞的测试,验证了该涂层的减阻效果。并以微漩涡理论解释了减阻机理。     

Winkler地基上黏弹性输流管的参数共振稳定性

本文研究了黏弹性输流管在Winkler地基上的横向振动。管道的黏弹性材料用Kelvin本构关系描述,在两端铰支边界条件下,对系统的控制方程应用直接多尺度法建立相应的可解性条件,得到了系统次谐波共振和组合共振的稳定性边界条件,考察了系统的各种参数如阻尼、脉动流速、质量比、弹性地基对稳定性边界条件的影响。     

矩形管道内磁性液体涂层流动状态的实验研究

论述了磁性液体粘性减阻技术的原理.在矩形管道实验装置中,研究了水流过磁性液体涂层时磁性液体流动状态的变化以及磁性液体的减阻性能.初步得出在外部磁场的作用下,由于磁性液体内部存在回流,致使其在被传输流体流过时能够稳定存在于管道内壁的结论;并通过实验得出只有当管道内部涂层厚度适当时,磁性液体才有减阻效果的结论.     

聚氨酯-丙烯酸酯柔性壁的减阻性能

采用种子乳液聚合法和物理共混交联法制备了以水为溶剂的聚氨酯-聚丙烯酸乙酯(PU/PEA)乳液和聚氨酯-聚丙烯酸丁酯(PU/PBA)乳液柔性壁。该乳液不仅环保,而且强度高,弹性好,粘接性优良。小型水洞平板阻力测试结果表明,PU/PEA复合乳液有一定的减阻作用,水流速度高时减阻率也高,流速为3.0 m/s时达到8.8,PU/PEA(40/60)复合乳液涂层在0.5~3 m/s的速度范围内平均减阻率达到5%;粒子图像速度测试给出了在相同雷诺数下柔性壁与铝板的平均摩擦阻力系数的比较以及计算得到的减阻率。结果表明,PBA/PU和P(BA-EA)/PU的减阻效果差不多,平均约5.3%,而PBA/PU-MMA低速减阻,高速不减阻。PU/PBA混合乳液涂层在0.5 m/s和1 m/s的流速下减阻率分别为7%和4%。     

大面积微结构辊对板热压印装置研发及工艺优化

目的 研发一种模块化辊筒对平板类型的微结构热压加工装置,研究不同模具结构下的辊压工艺参数对光学聚合物微结构成形的影响,研究大尺寸的PMMA样品的翘曲规律。方法 使用一种基于线接触的扫描连续辊压工艺,分别使用线槽模具、不锈钢网孔模具进行辊压实验,根据实验结果确定最佳工艺参数范围。结果 在辊筒温度为150～180℃、平板温度为25℃、辊压压力为200～500 N和辊压速度为1 mm/s的工艺条件下,甲基丙烯酸甲酯平板（PMMA）微槽阵列的线槽宽复制度最高可达90%,微圆柱结构在40 mm×40 mm PMMA衬底的覆盖率高达95%。结论 优化辊压工艺参数后,可以实现聚合物的大面积槽阵列和圆孔微透镜的稳定连续辊压成形。针对大面积光学聚合物翘曲的问题,进行了双面热辊压实验,发现二次成形后微透镜样品的最大高度偏差小于0.16 mm,翘曲现象得到了有效抑制。     

辊式涂布两辊间隙施涂过程的数值计算分析

目的系统地计算涂层厚度与两辊间隙、涂布辊速度以及胶黏剂的流体稠度和流动指数等影响因子的关系。方法在分析该复杂流动机理的基础上,利用CFD软件对具有非牛顿流体特性胶黏剂的两辊间隙施涂过程进行二维数值模拟。结果在五辊无溶剂涂布工程中,两辊间隙增大,最终涂布厚度也明显增大;增大涂布辊转速,涂布厚度也将减小;胶黏剂的流体稠度越大,最终传递到基材上的涂层厚度减小。结论两辊间隙的大小对涂层厚度的影响最大,胶黏剂的流体稠度、流动指数也对涂层厚度有较大的影响。     

3种低表面能减阻涂层的性能分析

为了得到船舶或水下航行器外层涂覆低表面能减阻涂层,分别在马口铁和碳钢基材上制备了氟硅涂层、聚氨酯弹性涂层、纳米涂层。依据相关标准测试了3种涂层的干燥时间、厚度、冲击强度、附着力以及打磨前后水接触角,并通过外观、光泽度、接触角等方式来分析和评价涂层的耐人工海水浸泡、耐湿热交变性能。最后,在回转体模型上,通过高速水洞试验测试了3种低表面能涂层的减阻性能。结果表明:在水流速度为2.0~10.0 m/s时,3种低表面能涂层皆具备良好的减阻效果,其中以聚氨酯弹性涂层的减阻效果为最佳,平均减阻率为-4.24%。     

基坑开挖爆破作用邻近压力燃气管道动力响应特性研究

确保复杂城市环境基坑爆破开挖工程中邻近压力燃气管道的安全性是关键性问题。依托武汉地铁8号线二期竖井基坑爆破开挖工程,利用现场监测数据建立ANSYS/LS-DYNA三维有限元数值计算模型,分析计算了不同运行压力条件下埋地燃气管道的动力响应特性。研究结果表明:实际工况下管道截面峰值合振速为0.453 cm/s,单元峰值von-Mises应力4.95 MPa,压力燃气管道处于安全运行状态;管道截面峰值合振速大于其正上方地表振速,且两者存在线性关系,由此建立管道爆破振动速度的预测模型;管道截面峰值合振速、峰值von-Mises应力均位于迎爆侧,且随管道内压的增加而增加,内压为零时为最佳运行状态,由此建立了管道峰值von-Mises应力与内压、爆破参数的数学计算模型,为实际爆破工程的安全作业提供指导。     

管材参数对输液管流固耦合振动的影响

采用特征线法对一蓄水池-管道-阀门(RPV)系统的流固耦合振动响应进行了数值计算,研究了管道结构阻尼、管材泊松比以及管道壁厚管道材料对系统振动响应的影响。结果表明：随着管道结构阻尼的增大,管壁本身的振动受到抑制;当管道结构阻尼大于某一临界值时,系统的振动能量主要集中在液体里,造成液体压力能的升高;随着泊松比的增大或管道壁厚的增大,液体的压能增大,管壁的轴向振动强度降低。     

蒙脱土/聚丙烯酰胺复合涂层导水纤维的制备及性能

用钠基蒙脱土/聚丙烯酰胺及有机蒙脱土/聚丙烯酰胺两种复合涂层材料,对天然纤维进行涂层化处理,制备了两种蒙脱土/聚丙烯酰胺复合涂层导水纤维.用快速水分测定法研究了导水纤维在不同温度和土壤湿度时的动态导水规律.利用扫描电镜观察了涂层纤维的表面形貌及涂层材料在不同水势下的微观形貌.采用X射线衍射仪及比表面积与孔径分布测定仪对普通蒙脱土与有机蒙脱土的物理结构进行表征.实验表明涂层导水纤维具有基于土壤温度及湿度的自调节机制,以便保证植物生长的合理土壤湿度.对蒙脱土进行有机化处理后,其层间距及孔径增大,有利于水分的传导.     

Al-Si镀层热成形零件表面颜色差异性研究

目的研究加热温度、加热时间等工艺参数对Al-Si镀层材料在热成形过程中存在的表面颜色差异、镀层厚度和扩散层厚度的影响规律,及影响零件表面颜色差异的主要原因。方法在不同加热时间及加热温度条件下,对厚度为1.0 mm的新日铁Al-Si镀层材料进行热冲压试验,测量热成形零件的镀层厚度和扩散层厚度,并对典型不同颜色零件表面进行SEM及EDS分析研究。结果 Al-Si镀层热成形零件表面颜色与加热温度和加热时间存在较好的对应关系,同时镀层厚度及扩散层厚度随着加热时间的增加及加热温度的提高而增大,Al-Si镀层热成形零件表面的颜色与镀层中不同铁氧化物的混合比例存在较好的对应一致性。结论Al-Si镀层热成形零件表面颜色的状态可以间接反应镀层厚度及扩散层厚度。     

Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure

In this work an all-optical hot-wire flowmeter based on a silver coated fiber combining a long period grating and a fiber Bragg grating (FBG) structure is proposed. Light from a pump laser at 1480 nm propagating down the fiber is coupled by the long period grating into the fiber cladding and is absorbed by the silver coating deposited on the fiber surface over the Bragg grating structure. This absorption acts like a hot wire raising the fiber temperature locally, which is effectively detected by the FBG resonance shift. The temperature increase depends on the flow speed of the surrounding air, which has the effect of cooling the fiber. It is demonstrated that the Bragg wavelength shift can be related to the flow speed. A flow speed resolution of 0.08 m/s is achieved using this new configuration.     

可交联磷酰胆碱聚合物改性聚甲基戊烯中空纤维膜

通过自由基聚合反应制备了可交联磷酰胆碱聚合物(Poly(MPC-co-LMA-co-TSMA), PMLT)。将该聚合物溶液涂覆在聚甲基戊烯中空纤维膜(PMPHFM)表面,经交联处理后可形成稳定的PMLT聚合物涂层,得到改性复合材料PMLT/PMPHFM。溶胀度测试表明PMLT聚合物膜具有良好的亲水性能,且溶胀度随着2-甲基丙烯酰氧基乙基磷酰胆碱(MPC)含量和温度的升高而增大。ATR-FTIR和XPS分析表明PMLT/PMPHFM表面的PMLT聚合物涂层含有磷酰胆碱基团。SEM和荧光测试结果显示PMLT/PMPHFM表面包覆有均匀的聚合物涂层,且该涂层能够抵抗乙醇溶液和十二烷基硫酸钠溶液的溶解。血小板黏附和全血接触测试表明,相比空白PMPHFM,PMLT聚合物涂层能够显著减少PMPHFM表面的血小板黏附,降低血液凝结风险。研究结果表明:可交联磷酰胆碱聚合物PMLT具有良好的亲水性能,能够均匀涂覆在PMPHFM的表面,得到具有良好血液相容性的复合材料PMLT/PMPHFM。      

非均匀成核法制备硅酸铝-硅灰石复合粉体材料

以硅灰石为原料,硫酸铝和硅酸钠为包覆剂,采用非均匀成核法制备一种硅酸铝-硅灰石复合粉体材料,研究搅拌速度、反应温度、反应时间、硫酸铝溶液浓度和滴加速度等工艺条件对复合粉体制备的影响。结果表明,控制机械搅拌速度为300~400 r/min,反应温度为80℃,反应时间为30 min,硫酸铝溶液浓度为0.1 mol/L,滴加速率为1~2 mL/min,可以实现硅酸铝以非均匀成核形式沉积在硅灰石表面,包覆硅酸铝后硅灰石白度提高,粒度增大,比表面积提高200%以上。     

The friction drag of a turbulent flow reduced on the surface with a molecular film of foleox polymer

We have experimentally studied the possibility of reducing the friction drag of a flow over a metal surface by applying a fluorine-containing polymer (foleox) onto the surface. It is shown that the foleox coating significantly decreases the friction drag of a turbulent flow.     

Characterization and Performance of AlTiN,AlTiCrN, TiN/TiAlN PVD Coated Carbide Tools While Turning SS 304

This study presents the physical, mechanical properties and dry turning performance of AlTiN, AlTiCrN, and TiN/TiAlN coatings produced on K-grade tungsten carbide insert by advanced physical vapor deposition technique. Scanning electron microscopy, microhardness tester, and scratch tester were used to examine surface morphology, coating thickness, microstructure, microhardness, and adhesion of coating. The performance in terms of cutting force and temperature of AlTiN, AlTiCrN, and TiN/TiAlN coated inserts was evaluated while dry turning of SS 304 steel. SS 304 is considered as “difficult-to-cut” material due to its exotic properties. The experiments were conducted at cutting speed of 140, 200, 260, and 320 m/min. Feed and depth of cut were kept constant and their values were 0.20 mm/rev and 1 mm, respectively. Experimental observations depicts that AlTiCrN coated insert demonstrated better performance because of its good adhesion and high oxidation resistance followed by TiN/TiAlN coated insert. TiN/TiAlN coated insert exhibited higher cutting temperature than AlTiCrN and AlTiN coated inserts. The findings of the study should also provide economic machining solution in case of dry turning of SS 304 stainless steel.     

Development of diamond coated tool and its performance in machining Al-11% Si alloy

An attempt has been made to deposit CVD diamond coating on conventional carbide tool using hot filament CVD process. ISO grade K10 turning inserts with SPGN 120308 geometry were used to deposit diamond coating. This diamond coating well covering the rake surface, cutting edges and flank surfaces could be successfully deposited. The coatings were characterized by SEM, XRD and Raman spectroscopy for coating quality, morphology etc. Performance of diamond coated tool relative to that of uncoated carbide tool was evaluated in turning Al-11% Si alloy under dry environment. The diamond coated tool outperformed the uncoated carbide tool which severely suffered from sizeable built-up edge formation leading not only to escalation of cutting forces but also poorer surface finish. In contrast, the diamond coated tool, owing to chemical inertness of diamond coating towards the work material, did not show any trace of edge built-up even in dry environment and could maintain low level of cutting forces and remarkably improved surface finish. It has been further revealed that success of the diamond coated tool depends primarily on adhesion of the diamond coating with the carbide substrate and this is strongly influenced by the pre-treatment of the carbide substrate surface before coating.     

反应条件对SiO_2包覆片状铝粉表面形貌的影响

以硅酸钠(Na2SiO3.9H2O)和片状铝粉为原料,在缓冲溶液中制备SiO2包覆片状铝粉,研究不同pH值、温度、包覆量等对铝粉表面SiO2包覆层形貌的影响;用场发射扫描电镜表征包覆层的形貌,并测定粉体中SiO2的含量。结果表明:溶液pH、温度对包覆层的形貌有较大影响;在反应温度为85℃、pH=9.5的条件下,铝粉表面形成致密、表面平滑的SiO2包覆层。     

The synthesis and characterization of polymer coated iron oxide microspheres

For biomedical applications drug carrying polymers are coated around magnetic iron oxide particles to form microspheres. In the present study, the iron oxide powder was ball milled. Microspheres were then synthesized by solvent evaporation, resulting in iron oxide particles encapsulated in a polymer and drug coating. Various parameters, such as the duration of milling and agitation speed as well as the polymer concentration were varied. A milling time of 72 h was found to yield a small size and narrow size distribution of particles; the average particle size was about 600 nm. Measurements of the change in grain size and the magnetic properties of the powder with milling time were performed. It was determined that the size of the microspheres was not sensitive to the initial particle size, but it could be decreased by variation of agitation speed or polymer concentration. The agitation speed and polymer concentration of 400 rpm and 0.04 g poly(l-lactic acid) in 8 g dicholoromethane, respectively, was found to yield small, spherical microspheres with a narrow size distribution. The surface morphology and magnetic properties of the microspheres was also analyzed.