Experimental research on micro hole drilling of polycrystalline Nd:YAG

Polycrystalline Nd:YAG materials have wide applications in solid-state lasers. In this study, micro hole drilling experiments were performed on polycrystalline Nd:YAG using a polycrystalline diamond micro drill. The hole diameter, edge chipping, and hole wall surface quality were examined in detail. The results showed that the hole diameter was slightly larger than tool diameter. A diameter error of less than 5.5% was achieved. The edge chipping at the entry hole was formed by the encircled petal shape exfoliations, which were produced by the indentation and rotation movement in the drilling entry stage. Edge chipping at the exit hole was generated by an entire piece of exfoliation, which was produced by a circle of microcracks around the tool tip propagating to the bottom surface in the drilling exit stage. The edge chipping width at the entry hole was smaller than that at the exit hole. Based on different material removal modes, the hole surface morphology was classified into three types: ductile removal, coexisting ductile and brittle removal, and brittle removal. The hole surface quality mainly depended on the proportion of the brittle fracture to ductile removal surface.     

Dry forming of aluminum alloys – Wear mechanisms and influencing factors

Tribological contacts in sheet metal forming are accompanied by several wear phenomena. One of which is the transfer of material from the softer sheet material to the harder tool surface, namely adhesive wear. Forming of aluminum alloys makes high demands on forming processes. Aluminum alloys show a strong tendency of adhesion on common tool materials. Adhesions on tools reduce the surface quality, the dimensional accuracy of the parts and the process stability. In order to avoid adhesive wear during forming, nowadays a high amount of lubricant is applied to the aluminum sheets. Though economically and ecologically attractive, dry forming processes with aluminum sheets seem not to be possible. In order to develop advantageous tribological systems a comprehensive understanding of the acting mechanisms is necessary. This paper discusses the influence of the alloy composition and the influence of oxide layers on the adhesive wear in aluminum forming.     

Structured estimation of tire forces and the ground slope using SM observers

In agricultural context, the principal cause of serious accidents for all-terrain vehicles(ATVs) is rollover. The most important parameters related to this risk is the ground slope. In this paper, we propose a structured observer to estimate the system states and the longitudinal tire forces using only wheel angular velocities measurement. The robust estimation is based on a second order sliding mode observer. This estimation is then used to build up a ground slope estimation. The algorithm is composed by two cascaded estimators. This structured estimation is then applied to the model of an agricultural vehicle G7(GregoireTM) integrated in the driving simulation environment SCANeRTM-Studio.     

低温自反应淬熄法制备微纳米钡铁氧体空心复相陶瓷微珠吸波剂

以Fe(NO3)3-Ba(NO3)2-CO(NH2)2-酚醛树脂-硅烷偶联剂KH550为反应体系,采用低温自反应淬熄法结合热处理工艺,制备了微/纳米钡铁氧体空心复相陶瓷微珠。通过扫描电子显微镜、X射线衍射仪、透射电子显微镜、热分析及高速摄影技术测定了热处理前后微纳米钡铁氧体空心复相陶瓷微珠的形貌、结构及组成,并研究了其形成机理。结果表明:热处理前空心复相陶瓷微珠粒径为0.59至27.1μm,主要为非晶态;热处理后复相陶瓷微珠由六角晶型的Ba3Fe32O51、BaFe12O19和Ba5Fe14O26组成,且表现出片晶与固溶体相互交叉的现象。特殊的试验条件使得团聚粉粒子在火焰场中飞行过程中在受热蓄能阶段、热释放阶段、后燃烧阶段与快速凝固阶段都具有不同的反应机理,从而使得尺寸细化,具有较微米级微珠不同的本征参数。     

微电解—水解酸化-硝化反硝化工艺处理假发生产废水

采用微电解—水解酸化-硝化反硝化工艺处理假发生产废水,微电解去除废水中的色度和其他污染物,并提高废水的可生化性,以利于后续生化处理;水解酸化提高后续处理的容积负荷,提高去除效率,对进水中有机氮的氨化作用明显,硝化反硝化可将水解产生的NH3-N全部转化。运行结果表明,进水COD为1 100 mg/L、氨氮为120 mg/L的情况下,该工艺降解COD及脱氮效果良好;处理工艺保证系统出水COD〈40 mg/L,氨氮〈5 mg/L,达到了《污水综合排放标准》一级标准。     

关于微型化学实验在化学教学中的应用探究

化学微型实验,顾名思义：“实验药品微量化,实验仪器微型化”。根据微型实验的特点和要求,可以将一些普通的化学实验改造为微型实验,运用微型化的仪器进行化学实验。一方面,降低了实验成本,减少了环境的污染,体现了绿色经济的理念。另一方面,提高了学习者学习化学实验的兴趣,促进了新的教学模式的发展,体现了科学创新的理念。     

无机填料对聚合物复合材料摩擦学性能的影响

参阅大量英语文献的基础上,简述了纳米无机粒子填料对聚合物及聚合物复合材料摩擦磨损性能的影响。主要包括微米/纳米无机粒子尺寸、含量及无机粒子与其它材料的协同作用对聚合物基复合材料摩擦磨损性能的影响,对科研工作者深入探索和研究聚合物复合材料的摩擦学性能有一定的参考价值。     

滚轮装置在U形管式换热器中的应用

U形管式换热器的管束经常需要抽出和装入,为便于管束的抽出和装入,应在管束支撑板上装设滑道,在国内的设计中则大都采用板条滑道,很少采用滚轮装置这种形式。结合热交换器的结构特点,设计和制造了适合管束质量比较大,管束长度较长的U形管换热器用的滚轮装置,并结合实例加以阐述滚轮装置设计制造和支撑导轨的安装要求。     

特种车辆履带连接件微纳米渗锌工艺

将微纳米渗锌工艺应用到特种车辆履带连接件中,可以显著提高履带连接件的耐磨损、耐腐蚀性能和镀层均匀性,避免零部件发生"锈死"的现象,且微纳米渗锌生产过程中没有三废排放,绿色环保。具有很高的工程价值,经济效益、环境效益显著。