电镀锌钢材表面物理气相沉积Zn-Mg合金镀层的电化学性能(英文)

锌合金镀层由于具有较强的耐腐蚀性能而得到广泛的关注,特别是Zn-Mg合金镀层,其耐腐蚀性能能得到显著提高。采用气相沉积方法制备不同镁含量的Zn-Mg合金镀层,研究Zn-Mg合金镀层中镁含量对其耐腐蚀性能的影响。在3%NaCl溶液中进行浸泡试验、动电位测试和电偶腐蚀试验,研究不同Mg含量镀层的耐腐蚀性能。结果表明,Zn-Mg合金镀层的耐腐蚀性能与Mg含量显著相关,镀层的腐蚀电位随着Mg含量的增加而降低,但是腐蚀电流密度却升高,直至15%Mg含量;在Zn-Mg合金镀层中存在钝化区。     

提高虚拟车削仿真质量的工件建模方法

根据车削加工工件的几何外形和成形特点 ,提出了包含加工误差信息的回转体类工件半剖轮廓多边形建模方法和记录、组织加工误差信息的刀具轨迹法。在虚拟加工中 ,刀具扫描体被简化表示为刀具扫描体轮廓多边形 ,简化了仿真计算。同时还对加工过程仿真和反映加工误差的已加工表面形貌的构建等关键问题进行了研究。该建模方法在VMIS虚拟加工与检测系统中获得了应用     

弹性基体磨具的磨抛轨迹与表面加工质量研究

目的 解决以光学玻璃为代表的硬脆材料加工效率与表面质量难以同时得到保证的共性问题。方法 以弹性基体工具磨削抛光技术为基础,分析弹性接触区域内有效工作磨粒的运动行为。基于Preston方程材料去除模型,研究磨抛过程中磨抛接触区域的接触面积、速度分布、多颗磨粒的运动轨迹。基于运动学模型,探究磨抛过程中磨具的运动学参数、磨粒浓度及排布特征等因素对磨粒磨抛轨迹的影响,采用磨具与工件接触区域磨粒运动轨迹相对面积占比和变异系数表征磨粒运动轨迹分布的均匀性,并建立基于轨迹均匀性的加工表面质量评价方法,优化工艺参数。以石英玻璃为加工对象,以硅橡胶中混入金刚石磨粒为基体,通过正交实验研究不同参数对工件表面质量的影响。结果 仿真结果表明,选取自转速度为300 r/min、进给速度为1 mm/s、磨抛进动角为15°,磨粒浓度及排布采用1 mm磨粒理论间距,此时获得的最大磨粒运动轨迹相对面积占比为96.46%,最小变异系数为0.375。通过实验,得到了选取磨抛工艺参数中的最佳参数组合,自转速度为1 200 r/min,进给速度为1 mm/s,磨抛进动角为15°~20°,磨粒浓度及排布采用磨粒间距1 mm,该组合可将工件的表面粗糙度由1.078 μm降至0.057 μm,材料去除率为3.8×10⁸ μm³/min。结论 磨粒运动轨迹的密集程度与自转速度、磨粒浓度及排布呈正相关,与进给速度呈负相关,在考虑加工成本的前提下,采用高自转速度、高磨粒浓度、低进给速度及15°~20°的进动角可以获得密集且均匀的磨粒运动轨迹,提高了工件的表面质量和材料去除效率。     

有限区间内设备顺序预防性维护策略研究

为了克服等周期维护模型忽略设备可靠性要求,以及长期运行期望维护周期模型忽略设备特定阶段维护需求的缺点,通过引入基于役龄递减因子和故障率递增因子的混合式故障率演化规则,建立了有限区间内基于设备可靠性的顺序预防性维护优化模型,并以威布尔分布为例,利用仿真方法对其进行了优化。仿真结果显示,该模型可使设备的维护周期呈递减之势,反映了设备在某一特定阶段的可靠性需求。     

Study of residual stresses in tailor rolled blanked Al5J32-T4 sheets

Several automotive parts such as door panels have been manufactured by using load-adapted blanks for crash optimization and weight minimization.Recently, Tailor Rolled Blanks (TRB) has been introduced to remove the disadvantages of a welding process which was used in joining panel components.TRB offers better structural design capabilities due to the seamless transitions on the panels with different thicknesses.In spite of the advantages of the process, TRB leaves internal stresses in the panel.This residual stresses lower the formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes.In this research, the residual stresses of TRBed Al5J32-T4 sheets were studied by X-ray stress analysis, and also microstructure was observed along the rolling direction.In addition, heat treatment was done after TRB process in order to compare the residual stresses to that of the TRBed sheets before the heat treatment.     

空气自然对流式质子交换膜燃料电池的三维建模和实验分析

在空气自然对流式燃料电池内部,速度、温度、组分浓度及电流分布特性有着极强的耦合作用.氧气质量传输限制引起的浓度过电位是这种燃料电池的主要性能损失.从自然对流、传热传质的角度,建立了三维数学模型.利用三维流体动力学软件和用户建立的子程序,对自然对流下Navier-Stokes 方程,能量方程,电化学动力学方程以及组分、水的传输方程进行了数值求解.通过分析数值计算的结果,结合自然对流的特性,设计了实验系统.对温度分布和电池性能进行了测试.对空气湿度对电池性能的影响进行了分析.数值计算结果与实验结果很好地吻合.模型的建立,对于认识空气自然对流式质子交换膜燃料电池内部的耦合传输现象有极大的意义,可以作为质子交换膜燃料电池的计算机辅助优化设计工具.     

香港地区应用干式风机盘管系统节能和室内空气品质分析

冷板辐射加置换通风空词系统在保证室内环境的前提下比常规全空气空调系统节能,但在天气湿热的香港地区应用会出现冷板凝露现象,且采用置换通风方式,风量有限从而影响热舒适性.本文将干式风机盘管系统与独立除湿通风系统组合应用于香港地区办公楼,干式风机盘管系统处理室内显热负荷,独立除湿通风系统承担室内湿负荷和室外全热负荷.采用EnergyPlus软件模拟分析了该空调系统在香港地区某办公楼中的使用性能,结果表明该系统能很好地控制室内温、湿度,特别是湿度,与常规全空气空调系统相比,全年节能达10.3%.     

Computational study on influence of RF shielding box on inductance of coil

Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network, RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding box. In this work, we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave simulation. Simulation results shows that the coil inductance decreases from -6.0% to -11.9% compared with its ideal inductance depending on coil positions within the RF shielding box. Both inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil inductance. We expect that these results would be useful for those who design RF matching networks.     

Effects of honing treatment on AIP-TiN and TiAlN coated end-mill for high speed machining

The objective of this work is to compare the tool performance of TiN and TiAlN coated carbides end-mills deposited by an arc ion plating (AIP) method, using honing treatment to polish the cutting edge surface sleekly. The curve of surface roughness versus honing time showed a rapid improvement initially and thereafter became steady, manifesting a saturation effect. The optimal honing time related to surface roughness was determined to be approximately 20 s. As the surface roughness increased, the critical loads reduced. At an average surface roughness (Ra) of 0.028 μm, the highest critical loads of TiN and TiAlN coating layers were 98 and 114 N, respectively. Tool performances of uncoated and coated tools were conducted under high speed machining (HSM) of AISI D2 cold-worked die steel (62 HRC). Consequently, the TiAlN coated end-mill using honing treatment showed excellent tool life under HSM conditions.     

TOXICITY, MUTAGENICITY AND TERATOGENICITY OF BREVIANAMIDE, VIOMELLEIN AND XANTHOMEGNIN; SECONDARY METABOLITES OF PENICILLIUM VIRIDICATUM

The three major secondary metabolites of Penicillium viridicatum, brevianamide, xanthomegnin, and viomellein were tested for mutagenicity by the Salmonella/microsome test and for toxicity and teratogenicity by the chick embryo test. None were mutagenic. Viomellein was mildly toxic and teratogenic, xanthomegnin was the most toxic and was not a teratogen, and brevianamide was not toxic yet was the most teratogenic.