钢板轧后冷却过程温度场仿真

建立钢板的温度场模型是钢板轧后冷却过程控制与优化的基础.为此,简述了钢板轧后冷却过程模型研究的情况,基于有限元方法建立了钢板轧后冷却过程的温度场模型,并进行了仿真研究.在ANSYS软件环境下,通过对工件几何、单元类型、材料属性与边界条件等定义,对钢板轧后冷却过程瞬态温度场模型进行了仿真求解,得到了钢板的温降曲线及瞬态温度场分布,所模拟出的温度场对合理制定冷却制度和冷却工艺具有实际指导意义.     

超大长径比双螺杆挤出机制备聚丙烯腈初生纤维

采用自主研发的超大长径比(136)双螺杆挤出机实现了PAN初生纤维的纺丝制备,研究了PAN粉料质量分数(16%、20%、24%)、双螺杆挤出机机筒温度(50、60、70℃)、循环挤出次数(0、1、2)对PAN初生纤维力学性能及表面形貌的影响。结果表明,PAN初生纤维的拉伸强度随质量分数、机筒温度和循环挤出次数的增加而增大;PAN初生纤维的断裂伸长率随质量分数和循环挤出次数的增加而减小,随机筒温度的升高而增大;随着循环挤出次数增加,纤维表面越来越规整,缺陷逐渐减少。研究结果为利用超大长径比双螺杆挤出机制备出性能更好的PAN初生纤维奠定了基础。     

摹于CCD的高精度细丝直径在线检测技术研究

在现代工业生产中,人们通过在线检测的方法对细丝进行实时监测与控制,提高产品合格率以及效率,为人们带来方便,非接触式智能化仪器将逐步取代传统上的机械测量仪器。本文阐述了CCD成像法测量装置的基本原理,分析了光学系统各部分的形式,并采用远心光路成像,从而保证成像质量和测量精度。之后用阈值法提取被测工件的边缘信息,同时还给出了CCD成像法测量直径系统的MATLAB处理后的灰度图。     

如何缩短大直径长拉刀的长度

文章讨论了缩短大直径拉刀长度的一般规律，以及根据各种拉刀的特点，缩短其长度的特殊措施。指出了当轮切式拉刀允许有较大的齿升量时，应尽量选取最大的Sz／t值和最大的容屑槽深；在齿升量不是主要约束条件时，可减小齿距来缩短拉刀的总长度。     

大尺寸直径非接触光电检测系统研究

提出了一种基于激光位移测头的大尺寸直径光电测量系统，可用于直径达φ52200mm的大尺寸工件的非接触测量。文章详细论述了测量系统结构、工作原理及同轴度测量方法，并对影响测量精度的主要误差来源进行了分析，结果表明测量精度达0．02mm。     

圆轴直径的自动视觉精密检测

介绍一种圆轴直径的自动视觉精密检测方法。首先通过对圆轴图像边缘像素进行线性拟合,把圆轴两条边缘定位到亚像素精度;然后运用细化技术,求得圆轴的中轴骨架;最后通过从中轴线上的一点引出垂线求得交于两条边缘交点的方法计算直径并与标准值比较。实验表明,本系统精度高,稳定性强,速度快。     

基于线径反馈的模糊PID控制在拉丝机械上的应用

介绍在拉丝机上采用激光CCD实时测径,讨论并设计基于线径、速度反馈的采用模糊PID控制方法的双闭环拉丝控制系统.     

Investigation of Pt Catalysts Supported on Multi-Walled Carbon Nanotubes with Various Diameters and Lengths

Platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) with various diameters and lengths were studied by using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) and Chronoamperometry. The results indicated that the MWCNTs with smaller diameter generated more amorphous carbon after a sonochemical oxidation treatment. Compared with the long MWCNTs, the short MWCNTs had more open ends, resulting in high-Pt dispersion and electrocatalytic activity towards methanol oxidation. Pt nanoparticles supported on short MWCNTs with a diameter of 30–50 nm exhibited the best Pt dispersion and highest methanol oxidation activity among the catalysts studied. The high activities of the catalysts based on short MWCNTs were due to both the intrinsic high activity of the ends of MWCNTs and a good Pt distribution.     

偏心异径管流量计特性的试验研究

在模拟现场条件下通过试验研究了偏心异径管流量计的特性，给出了试验曲线，为流量测量与监测提供了一种新方法，具有工程实用价值。     

A numerical study of the effects of cutter runout on milling process geometry based on true tooth trajectory

Cutter runout is a common phenomenon affecting the cutting performances in milling operations. To date, most of the milling process models considering cutter runout were established based on the circular tooth path approximation, which brought errors into the runout estimation. In this paper, a new approach is presented for modelling the milling process geometry with cutter runout based on the true tooth trajectory of cutter in milling. The mathematical relationship between the trajectories generated by successive cutter teeth with runout is analysed. The milling process geometrical parameters, including the instantaneous undeformed chip thickness, the entry and exit angles of a cutting tooth, and the ideal peripheral machined workpiece surface roughness, are modelled according to the true tooth trajectories. Numerical method is used to solve the derived transcendental equations. A simulation study of the effects of cutter runout on milling process geometry is conducted using the models. It was found that the change of cutter radius for a tooth relative to its preceding one is the most important factor in evaluating the effects of cutter runout.