Evaluation of Microstructure and Wear Properties of Ti-6Al-4V Alloy Plasma Carbonized at Different Temperatures

Ti-6A1-4V （TC4） alloys were plasma carbonized at different temperatures （900, 950, and 1 000 ℃） for duration of 3 h. Graphite rod was employed as carbon supplier to avoid the hydrogen brittleness which is ubiquitous in traditional gas carbonizing process. Two distinguished structures including a thin compound layer （carbides layer） and a thick layer with the mixed microstructure of TiC and the a-Ti in carburing layer were formed during carburizing. Furthermore, it was found that the microstructure and the properties of TC4 alloy were significantly related to the carbonizing temperature. The specimen plasma carbonized at 950 ~2 obtained maximum value both in the hardness and wear resistance.

Store Environment:Its Importance and Consumers'Expectations on Casual-wear Chain Stores in Honk Kong

This study attempted to examine the importance of storeenvironment in affecting consumers’store choice deci-sion;the relative importance among the three environ-mental factors;and consumers’expectations on store en-vironment for the casual-wear chain stores in HongKong.Julie Baker’s Three-category framework onstore environments namely ambient,design and socialfactors was adopted for investigation.The results indi-cated that the store environment was important in affect-ing consumers’selection of store for shopping.It alsorevealed that social factor was perceived relatively im-portant than ambient and design factors.Nine store ex-pectation dimensions were categorised and the resultdemonstrated that most respondents were concerned onthe social aspect in their expectation of having a satisfy-ing store environment.

Variations in the Atmospheric Electric Field at Tropical Station during 1930-1987

The variations noticed in the atmospheric electric field recorded at Pune (18°32'N, 73°51'E, 559 m ASL), a tropical inland station located in Dcccan Plateau, India, during the period 1930-1987, have been examined in relation to the variations observed in the Angstrom turbidity coefficient (β) and selected meteorological parameters. The monthly and annual mean values of the atmospheric electric field. Angstrom turbidity coefficient (β), rainfall, temperature and relative humidity for the years 1930-1938, 1957-1958, 1964-1965, 1973-1974 and 1987 were considered in the study.The results of the above study indicated gradual increases in the atmospheric electric field over the period of study (1930-1987) which is statistically significant at less than 5%level. The increases noticed during different periods varied from 30 to 109%. The increase noticed during the period (1930-1938) and (1973-1974) was maximum (109%). The Angstrom turbidity coefficient also showed systematic increases during the period of study, which is consistent. The diurnal curve of the atmospheric electric field at the station by and large, showed a double oscillation, which is generally observed in the conlinental environments.

Effect of Silicon Content on Wear Resistance of Al-Si Alloys

The sliding wear behavior of hypoeutectic, eutectic and hypereutectic Al - Si alloys under lubricating condition was investigated. The wear mechanism of three kinds of alloys was discussed and an effective way to improve the wear reslstance of Al - Si alloys was put forward, that is increasing the silicon content.

Microstructural Characteristics and Wear Performance of Plasma Sprayed Al_2O_3-13 wt. % TiO_2 Coating on the Surface of Extrusion Wheel

The conventional Al2O3-13 wt. % TiO2 composite ceramic coatings are fabricated by plasma spraying on the surface of extrusion wheel. The microstrueture, morphology and phase compositions of the substrate and coat- ing are investigated by using X-ray diffractometry （XRD） , scanning electron microsopy （SEM） and energy dis- persive spectroscopy （EDS）. Moreover, the microhardness of the substrate and the coating are investigated using Vickers mierohardness tester, the friction and wear behaviors of the substrate and the coating are investigated by using a block-on-ring tribometer under dry sliding conditions with the load of 245 N. The results show that both γ-Al2O3 and α-Al2O3 phases are observed in the as-sprayed coatings, the mian phase is γ-Al2O3. There are white particulates Al2O3 on its surface. The Al2O3-13 wt. % TiO2 coating possesses higher mierohardness which is about 1018HV and 1.6 times that of the substrate. The wear performance of coating is better than that of the substrate. In a practical application, the life of the extrusion wheel which is plasma sprayed Al2O3-13 wt. % TiO2 coating on the surface is 1.2 times that of the conventional extrusion wheel, and the life is about 330 h.

Comparison between WC-10Co-4Cr and Cr_3C_2-25NiCr coatings sprayed on H13 steel by HVOF

WC?10Co?4Cr and Cr3C2?25NiCr coatings were deposited on H13 steel by high velocity oxy fuel (HVOF) spraying. To enhance the thermal stability of the WC?10Co?4Cr coating, NiCr powders were sprayed between the surface coating and substrate. The microstructures of the surface and cross section, thermal shock and wear resistance of these two coatings were investigated in detail. The carbon diffusion in the two coatings was explained from the view of the thermodynamic. And the adhesive strength of Cr3C2?25NiCr coating (64.40 MPa) is almost the same as that of WC?10Co?4Cr coating (61.69 MPa). The friction tests show that the Cr3C2?25NiCr coating has higher friction coefficient than the WC?10Co?4Cr coating at both 500 and 600 °C. The wear resistance of the Cr3C2?25NiCr coating is better than that of the WC?10Co?4Cr coating.

Seasonal variations of sulfur aerosols at Zhongshan Station, East Antarctica

Observations of atmospheric methane-sulfonic acid（MSA） and non-sea-salt sulfate（nss-SO4^2-） from December 2010 to November 2011 at Zhongshan Station are presented in this paper. MSA and nss-SO4^2- average concentrations were 24.2 ± 37.9 ng·m^-3（0.5-158.3 ng·m^-3） and 53.0 ± 82.6 ng·m^-3（not detected [n.d.]） - 395.4 ng·m^-3）, respectively. Strong seasonal variations of MSA and nss-SO4^2-, with maxima in austral summer and minima in winter, were examined. The high concentrations of sulfur compounds in December may be attributed the dimethyl sulfide（DMS） emissions from the marginal ice zone, when open water near the sampling site was important in impacting the sulfur species of January and February at Zhongshan Station. In austral winter, there was almost no phytoplanktonic activity in offshore waters, and atmospheric sulfur compounds likely had long-range transport sources.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

磨损间隙和机组转速对发电机推力轴承油槽密封泄露的影响

随着投产时间的推移,水电站轴承油槽盖密封被逐渐磨损,动静配合间隙增大,油雾逸出现象严重。为了探究磨损间隙和机组转速对油槽密封处油雾泄露的影响,建立了发电机推力轴承油槽密封几何模型,应用SSTκ-ω湍流模型,对不同间隙(0.2~2.0 mm)、不同转速(100~500 r/min)下油雾的泄露情况进行稳态数值模拟计算。结果表明,建立泄漏量、间隙值及转速三者之间的函数关系表达式,可发现间隙值对油雾泄漏量的影响比转速高;间隙增加后,密封齿的节流作用减弱,密封进口压力降低,加剧了油槽盖顶部的油雾泄露;进、出口处的流速随间隙值的增加而增大,当间隙值由0.2 mm增加至2.0 mm时,进口速度由20 m/s增加到113 m/s,出口速度由76 m/s增加到144 m/s,泄漏量由0.0344 kg/s增加到0.0538 kg/s。该研究可为水电站轴承油槽密封结构的优化、电站运行策略的制定及密封性能的判断提供一定的理论基础。

吉牛水电站冲击式水轮机水斗沙水流动特性及泥沙磨损研究

冲击式水轮机由于水头高,其高速射流引起的水轮机水斗泥沙磨损非常严重。为探究冲击式水轮机在高速水流下泥沙颗粒对水斗的磨损,基于CFD技术对吉牛水电站冲击式水轮机全流域进行液气固三相流动数值计算和水斗泥沙磨损预估,获得转轮水斗的内部流动特性和泥沙磨损情况。结果表明:水斗根部的出水边、水斗工作面靠近根部处以及切口和分水刃磨损严重,分水刃及切口的磨损大于水斗工作面的磨损,分水刃到出水边的磨损率总体上先上升后下降;水斗磨损的计算结果与实测结果较为一致,计算结果仅比实测结果偏大6%左右,说明泥沙磨损预估方法有效可行。本文的研究结果为冲击式水轮机泥沙磨损预估和电站运行维护提供了技术方法和依据。

移动交互系统突破常规操作监护模式研究

应用无线定位、视频分析等技术,建立适应水电站"无人值班,少人值守"模式下作业人员移动交互系统.基于该系统探索研究运行值班期间非计划工作的远程监护方法,运用移动交互系统远程监护操作有效解决非计划性操作、事故处理、试验配合等工作期间因人员配置不足造成的无监护操作问题,突破了电力安全工作规程常规监护操作方法的传统思维,为大型水电站"无人值班,少人值守"工作探索了新途径.

溢洪道高速过流面抗冲磨混凝土平整度控制关键技术

老挝南欧江七级水电站溢洪道工程具有水头高、建筑物体积大、泄流量大、流速高等特点,对泄槽过流面抗冲耐磨混凝土平整度提出极高要求。因混凝土裂缝、不平整、结构单薄、地质条件差等原因诱发,在高速水流冲刷下遭到毁坏,为了减少高速水流对过流面混凝土表面的冲击,防止造成负压和剧烈的水流脉动、出现空化和气蚀,避免导致结构的破坏,保证工程施工质量和结构的整体性,在施工过程中采用合理的施工工艺规范施工。检测结果表明溢洪道过流面平整度控制优良,可以确保混凝土质量满足结构安全要求及其使用功能。

计及电池动态损耗的电动汽车有序充放电策略优化

目前电动汽车通过电动汽车入网(V2G)技术向电网放电时,计算电池总损耗模型过于简单,无法准确反映电池的损耗。为此,基于电池放电特性曲线,文中利用电池放电动态容量衰减模型,得出在不同剩余电量下释放相同电量对电池损耗有较大差异的结论。在以配电网变压器容量为约束的前提下,建立了计及电池损耗的有序用电用户充放电费用最小模型及相应的充放电策略;并采用优先顺序法将多时段优化问题转化为各时段最优问题,实现该模型的求解。仿真算例结果表明该方法不仅可以有效保障放电用户利益,同时能够提高充电站利润及无序用电用户充电成功率。

渔子溪电站水轮机转轮叶片泥沙磨损研究

渔子溪系山区河流,泥沙含量大,渔子溪电站水轮机转轮的泥沙磨损严重。本文通过数值计算和试验分析的方法,对渔子溪电站的水轮机进行沙水流动的数值模拟和水轮机转轮叶片的泥沙磨损试验,得到水轮机转轮的泥沙磨损情况,预估出转轮的磨损寿命,并提出抗泥沙磨损的措施。研究结果对优化渔子溪电站水轮机运行策略提供了重要依据,用以指导电站运行管理人员有针对性地回避发生严重磨损的运行工况,以此达到保证机组安全运行、减轻转轮磨损、延长转轮使用寿命、最大程度减少电量损失的目的,同时也对其他多泥沙河流水轮机抗磨研究和运行具有重要的指导意义。

考虑损耗成本的电池储能电站建模及优化调度

为提高风电并网效益,减少弃风,在电网中接入电池储能电站(battery energy storage power station,BESPS)。首先,建立了考虑损耗成本的BESPS调度特性模型,该损耗成本由BESPS投资成本与调度区间内的充放电循环次数估算;然后,在考虑风电可信容量的基础上构建了BESPS调度模型。某些情况下,系统很难全额消纳风电,因此,调度模型具有运行成本最小与风电接纳最大2个不同维度的优化目标。为求解此问题,基于隶属度函数将2个子优化目标模糊化,构建了基于最大满意度的单目标优化模型,并采用GAMS软件提供的CPLEX求解器对其进行求解。基于我国东北某实际省级电网的仿真实验说明:BESPS接入可显著提升系统风电接纳能力,且基于最大满意度的优化调度可给出更为合理的结果。

水泵的泥沙磨蚀及防治措施

在对我国典型多泥沙河流泵站进行大量调查研究的基础上,结合室内部分实验资料,比较系统地分析、论述了泥沙对水泵的磨蚀破坏、性能影响,并从不同的角度提出了减缓对策。

基于视频的轨道交通车站乘客口罩佩戴检测及测温技术

当前新冠肺炎防控期间,针对轨道交通车站等封闭场合的乘客是否佩戴口罩和非接触式体温测量等迫切需求,介绍基于视频的乘客口罩佩戴检测及非接触测温技术原理与发展现状,以及适用于轨道交通应用场景的可行方案,为助力打赢疫情防控阻击战提供技术支撑。

循环球式转向器磨损试验助力泵站的设计与实现

作为现代汽车转向的主动安全控制元件,转向器可靠性至关重要。循环球式转向器磨损试验参数主要有高温、变量、中压、转速、负载,需要实时监测与控制输入轴的扭矩与转角、输出轴载荷,显示或绘制载荷-角度曲线、扭矩-角度曲线和油压-角度曲线。为了正常进行循环球式转向器磨损试验,采用液压高温与变量技术和自动化集成技术,设计并实现了智能化循环球转向器磨损试验助力泵站。调试与运行表明:该助力泵站能满足循环球式转向器磨损试验标准规定功能,性能稳定,价格适宜。

黑河水电站水轮机主轴密封的优化改造

西安水务集团黑河水电站采用水压端面式主轴密封,在电站运行初期和密封检修后首次运行均出现橡胶圈烧损等现象;在汛期又出现顶盖水压过大,机组漏水加剧。电站频繁进行密封件的检修和更换。该文针对电站的负荷变化和密封体的结构展开分析,提出泵板联合密封和抗磨环表面开槽的设计方案。并在3号机组进行了改造实践,并取得了良好的改造效果。

HZS型搅拌站泵衬板的优化设计

对高铬耐磨铸铁衬板在HZS搅拌站砼泵上使用易出现开裂的情况进行了分析,发现这种成分的砼泵衬板其开裂的主要原因在于铸件冲击韧度值较低,硬度略高,硬质颗粒和基体组织之间没有取得较好的配合。因而采用对铸件进行二次热处理的方式,来略微降低硬度值,大幅上调冲击韧度值,以获得有较好耐磨性和更高抗冲击能力的衬板材料,大大提高了衬板材料的使用寿命。