脉冲电沉积RE-Ni-W-P-SiC复合镀层工艺

研究了RE-Ni-W-P-SiC复合镀层的脉冲电沉积工艺。结果表明：RE-Ni-W-P-SiC镀层的脉冲电沉积速率比直流电沉积大，脉冲镀层的耐蚀性和硬度都优于直流镀层，耐蚀性优于1Crl8Ni9Ti不锈钢；脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的性能都有很大影响。脉冲镀层比直流镀层的结晶更细密，表面更光滑平整。稀土的加入有利于细化晶粒。     

镍磷镀层钢板压焊工艺研究

由于镍磷镀层含磷量特别高,使该镀层钢板点焊质量存在着大量问题。本文作者采用多脉冲凸焊的方法实现了镍磷镀层钢板的焊接,使该工艺在批量试生产中获得实际应用。本文对镍磷镀层钢板凸焊接头的形成机理作了深入分析,并通过能谱试验对点焊接头和凸焊接头质量作了对比,从而分析出多脉冲凸焊工艺能够避免电极与焊件之间的粘结和改善熔核冷脆性等提高接头强度的机理,表明了只有采用凸焊工艺才是解决根本问题唯一可行的方法。     

基于X射线衍射方法研究三价铬镀层的晶体结构

本文通过采用直流和脉冲电镀方法,从BSC12型硫酸盐三价铬溶液中电沉积获得40um厚的镀层,镀层硬度高、耐磨性能等较好,且脉冲电镀法制备的镀铬层组织更加细化。采用X射线衍射仪对镀层的晶体结构进行分析测试,数据证明镀层为纳米级晶体结构,证实功能三价铬镀铬替代六价铬电镀工艺工程化应用可行。     

不同方式电沉积纳米TiN/Ni复合镀层的组织和耐磨损性能

采用直流电沉积、脉冲电沉积和超声-脉冲电沉积三种方式在45钢表面制备了纳米TiN/Ni复合镀层,分析了复合镀层的组织、显微硬度以及镀层中TiN的含量,并对复合镀层的耐磨损性能进行了研究。结果表明:直流电沉积复合镀层的晶粒最粗大,超声-脉冲电沉积复合镀层的晶粒尺寸最细小;直流电沉积复合镀层、脉冲电沉积复合镀层和超声-脉冲电沉积复合镀层的显微硬度以及镀层中TiN的含量依次增大;超声-脉冲电沉积复合镀层具有最佳的耐磨损性能,其磨损量为直流电沉积复合镀层的46%,显微硬度为604.72HV,镀层中TiN的质量分数为2.27%。     

脉冲电镀优化金镀层性能的工艺研究

镀金工艺是许多大高宽比微纳结构实现其功能化的重要技术手段。由于其结构的特殊性,往往需要获得晶粒小、致密均匀的金镀层,才能满足微纳元器件的需求。针对微纳米结构金属化的要求,研究了柠檬酸金钾脉冲电镀工艺,通过正交试验法确定了脉冲电镀过程较优的工艺参数,分析了主要的电镀工艺参数(平均电流密度、占空比和频率)对沉积速率、镀层形貌及金颗粒大小的影响,给出了优化的工艺参数:平均电流密度为1.8A/dm2、占空比为20%、频率为6kHz。试验结果表明,优化工艺参数下的金镀层致密均匀,颗粒度小且色泽好,能够满足微纳米结构金属化的要求。     

脉冲电沉积RE-Ni-W-P-SiC复合镀层的硬度研究

研究了脉冲条件对脉冲电沉积RE-Ni-W-P-SiC复合镀层硬度的影响。结果表明：脉冲频率和占空比的变化对镀层的硬度都有很大的影响；脉冲镀层的硬度都比直流镀层的硬度高；热处理温度小于600℃时，镀层的硬度随温度的升高而升高，加热温度继续升高，镀层硬度呈直线下降；在400℃热处理条件下，随着时间的延长．镀层的硬度增加，当时间达到3h时，镀层硬度最高；镀层中的SiC微粒随着温度的升高和时间的延长向基体金属的扩散越来越多；RE-Ni-W-P-SiC脉冲镀层的硬度高于Ni—W-P-SiC脉冲镀层的硬度。     

占空比及脉冲频率对镀镍层质量影响实验研究

目前单层CBN砂轮成为超高速窄深槽加工的首选,针对目前电镀法制备CBN工具存在的镀层与基体结合强度差、镀层质量难以控制等的问题,对45#钢基体试件进行了电镀镍实验。运用脉冲电镀方法,制备了单金属镍层。研究了脉冲电源占空比对镀层孔隙率的影响及电源脉冲频率对镀层表层质量的影响,获得最优组合条件下的电镀镀层结构及形貌。实验结果表明:当脉冲电源占空比为20%、脉冲频率为0.5k Hz时,获得的镀层具有较低的孔隙率、晶粒细致的结构及形貌。     

镍的周期换向脉冲电沉积实验研究

以不锈钢为基底,分别调节反向脉冲工作时间和正反电流比进行了系列化的电沉积镍涂层的工艺研究,发现随着反向脉冲工作时间的减小和正反电流比的增大,镀层表面的粗糙度减小、晶粒变细。     

脉冲参数对Cu-Sn-PTFE镀层组织结构和性能的影响

用脉冲电沉积的方法,在焦磷酸盐电解液中制备Cu Sn PTFE复合镀层,研究电流密度、脉冲频率、占空比等对镀层组织结构、成分、硬度及摩擦学性能的影响。结果表明,随电流密度和脉冲占空比的减小,复合镀层表面变得细腻,硬度逐渐增加;而随着脉冲频率的增大,镀层的摩擦因数有下降的趋势;复合镀层中的氟元素含量越高,镀层硬度越低,而镀层中的PTFE颗粒在摩擦过程中使得镀层具有优异的自润滑性能。在电流密度为25 A/dm2、频率3 000 Hz、占空比60%的脉冲参数组合下,复合镀层的组织均匀,PTFE含量高,摩擦学性能也最优异。     

脉冲参数对Cu-Sn-PTFE镀层结构和摩擦学性能的影响

采用脉冲电沉积的方法,在焦磷酸盐电解液中制备Cu-Sn-PTFE复合镀层,研究电流密度、脉冲频率、占空比等对镀层组织结构、成分、硬度及摩擦学性能的影响。结果表明,随电流密度和脉冲占空比的减小,复合镀层表面变得细腻,硬度逐渐增加;而随着脉冲频率的增大,镀层的摩擦因数有下降的趋势;复合镀层中的氟元素含量越高,镀层硬度越低,而镀层中的PTFE颗粒在摩擦过程中使得镀层具有优异的自润滑性能。在电流密度为2.5 A/dm~2、频率3 000 Hz、占空比60%的脉冲参数组合下,复合镀层的组织均匀,PTFE含量高,摩擦学性能也最优异。     

环卫保洁清扫自行车卧式滚刷清扫原理

针对环卫保洁清扫自行车,对卧式滚刷的清扫原理进行了分析,导出了必要条件。     

Structural similitudes for the dynamic response of plates and assemblies of plates

A structural similitude is proposed for the analysis of the dynamic response of plates or assemblies of plates. The similitude is defined by invoking the energy distribution approach which allows the representation of all the fundamental parameters. Then, the similitude laws are defined by looking for equalities in the structural responses. Two test cases are herein discussed: the first involves a single plate response and the second is related to an assembly of two plates. Only the bending waves are taken into account. If the original damping values are kept, a complete similitude is defined in both the cases which allows to enlarge or reduce independently the plate surfaces and the thickness. An approximate similitude is defined if the damping is modified: in this case only a mean response can be predicted in similitude.     

Device for the control and measurement of brush forces to an accuracy of a few grams-force while monitoring brush resistance and brush wear at currents up to 500 A or more

A brush holder is described which permits the electrical performance of a brush to be tested under currents of up to at least 500 A and speeds of up to at least 70 m s^?1 and under brush forces that can be applied and maintained within close limits. Simultaneously, the brush wear can be monitored continuously.     

Chemical factors in carbon brush wear

Chemical factors involved in the wear of carbon brushes on metal slip rings are discussed. Under conditions of elevated temperature operation in an oxidizing atmosphere, a correlation is found between the oxidation characteristics and the wear rates of carbon brushes. It is demonstrated that temperatures in the oxidation range can readily be generated by current converging through high resistance constrictions in the contact zone. Copper and other metals present in the slip ring can act as catalysts for the oxidation, the metal oxide particles migrating into the interior of the brush and causing enhanced gasification rates and increased porosity. Treatment of the brush with oxidation inhibitors, such as phosphorus oxychloride, and surface alloying of the ring with non-catalytic materials, such as zinc, can reduce the wear rate at elevated temperatures under favorable conditions. Graphite surfaces are also attacked by reactive gaseous species such as atomic nitrogen and oxygen, ozone and nitrogen oxides which may form near the brush surface during arcing.     

On the calibration of surface plates

Calibration of large surface plates could be performed using different measuring systems. In this investigation an autocollimator system, a laser system and a coordinate measuring machine have been investigated. A comparison among these methods of calibration has been carried out. An Elcomat 3000 autocollimator of resolution 0.05 arcsecond, an Agilent 5529A laser interferometer system of resolution 0.05 arcsecond and a Prismo/Zeiss Computerized Numerically Controlled Coordinate Measuring Machine (CNC–CMM) respectively are used. Large reflecting mirror, angular retro reflector and sensitive probe are used with autocollimator, laser systems and CNC–CMM respectively to identify heights at each position on the tested surface plate. Repeated results from the different methods are carried out and presented in the paper. Uncertainties associated with the measurement results of each method have been estimated using the GUM procedures and given in the paper. The paper discusses the difficults and ease as well as accuracies associated with each method.     

Improving the vibrational damping of plates

The apparatus and method for comparative vibrational-damping tests are described for steel and basalt-composite plates and plates with a special coating.     

Unsteady flow between rectangular plates and between circular plates

An analysis is presented of the unsteady flow of a viscous incompressible fluid between two parallel infinitely long rectangular plates and between two parallel circular plates. The lower plate is fixed and the upper plate moves towards the lower plate. Full Navier-Stokes equations are used to obtain the pressure distribution as a function of the film thickness h(t) and the velocity $\text{h}\text{?}\text{(t)}$ of the upper plate. The inertia is taken into account and, for a given load on the upper plate, the sinkage relation between h and t is determined for various values of the Reynolds number. The departure from the classical inertialess solution is exhibited for various values of the two dimensionless parameters involved, one characterizing the load and the other gravity.     

Cold plasma brush generated at atmospheric pressure

A cold plasma brush is generated at atmospheric pressure with low power consumption in the level of several watts (as low as 4 W) up to tens of watts (up to 45 W). The plasma can be ignited and sustained in both continuous and pulsed modes with different plasma gases such as argon or helium, but argon was selected as a primary gas for use in this work. The brush-shaped plasma is formed and extended outside of the discharge chamber with typical dimension of 10-15 mm in width and less than 1.0 mm in thickness, which are adjustable by changing the discharge chamber design and operating conditions. The brush-shaped plasma provides some unique features and distinct nonequilibrium plasma characteristics. Temperature measurements using a thermocouple thermometer showed that the gas phase temperatures of the plasma brush are close to room temperature (as low as 42 degrees C) when running with a relatively high gas flow rate of about 3500 ml/min. For an argon plasma brush, the operating voltage from less than 500 V to about 2500 V was tested, with an argon gas flow rate varied from less than 1000 to 3500 ml/min. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical applications including battery-powered operation and use in large-scale applications. Several polymer film samples were tested for surface treatment with the newly developed device, and successful changes of the wettability property from hydrophobic to hydrophilic were achieved within a few seconds.     

眼科同视机中海丁格刷装置的质量控制

为了提高同视机在医学上的应用及其治疗价值,就要保证同视机主要部件的质量。同视机的治疗主要是和海丁格刷部件有关。叙述了海丁格刷的在眼科中应用及治疗原理,针对海丁格(Haidinger)刷装置的主要部件偏光片的特性、质量控制和钴蓝玻璃滤光片的质量控制作了一些分析,把握好它的质量可以保证和改善同视机的治疗和检查的准确性,从而提高治疗效果。