Melt‐spinning process of a tetrafluoroethylene– hexafluoropropylene copolymer

An industrial melt‐spinning process of tetrafluoroethylene– hexafluoropropylene copolymer (FEP) using an extruder was studied. The novel “spinneret,” having both a large‐diameter spinning nozzle and a high‐temperature vessel, was used to solve the problem of filament breakage on the spinning line caused by high melting viscosity of FEP. The extruder, with its long feed zone, was newly designed to function with a geared pump. The strength of fibers increased with drawing of as‐spun fiber. FEP fibers up to six denier were continuously produced through long‐run production. According to this new process, FEP fibers can be supplied for textile or industrial application. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2366–2371, 2002     

脉冲放电高能转化制备纳米粉体

综合介绍了脉冲电流通过细金属丝放电(pulsed wire discharge,PWD)制备纳米粉体的方法.讨论了影响纳米粉体,特别是晶粒尺寸的因素,以防止形成亚微米颗粒.因为达到电压峰值的丝的沉积能相当于丝的汽化能,因此,能夠计算出沉积能.随着所施加的能量增加,气体压力降低,介质气体的热扩散率增大,晶粒尺寸变小.在惰性气氛中,采用PWD工艺,由金属蒸气急冷可制备金属粉体.如果介质气体变为氧气或者氨气,就能制备氧化物、氮化物纳米粒子.要制备双金属合金、双氧化物或氮化物纳米粒子就必需采用双金属丝和不同的介质气体.采用PWD工艺,在有机气体或烟气中,能制备电磁屏蔽和导电浆料和其它用途的钝化纳米粒子.采用丝输送器而实现大量生产纳米粉体的PWD工艺一个实例证明了PWD工艺生产纳米粉体的可行性.     

Crystal lattice deformation and the mesophase in poly(ethylene terephthalate) uniaxially drawn by solid-state coextrusion

The development of crystalline and mesophase structure on drawing of poly(ethylene terephthalate) (PET) has been studied. The uniaxial drawing has been done by solid-state coextrusion from 50 to 90°C. The unit-cell parameters of stress-induced crystallites in extrudates have been determined as a function of extrusion draw ratio (EDR) up to 4.4 and at an extrusion temperature (ET) above T_g, at 70 and 90°C. The higher the EDR, the longer the c-axis chain direction, the shorter the a and b axes and the smaller the unit-cell volume. In comparison with the conventional lattice parameters obtained by Bunn and Fisher, the highest elongation of the c axis is near 10%. These features imply that the lattice of stress-induced crystallites is far from the closest packing. Coextrudates made below the T_g of PET differ markedly from those made above T_g. Wide-angle X-ray diffraction (WAXD) patterns of PET extruded at 50°C (below T_g) even at high draw ratio exhibit small and/or imperfect crystallites. They appear much as a mesophase. The distance between macromolecular chains ranges from 3.2 to 5.4 Å. The shortest value in the mesophase approaches the interplanar crystal distance of 3.4 Å for the (100) crystal face, on which the benzene rings lie. The crystalline peak separation of the PET, WAXD curve has been evaluated to obtain absolute crystallinities and the content of mesophase and amorphous phase.     

矩阵法计算流水施工工期

简要分析了代数法、图上法在计算流水施工工期时存在的不足,提出了用矩阵法计算流水施工工期的方法．设计并分析了计算用表,说明了计算步骤,并用实例进行了验证．     

重钢预应力SWRH82B盘条的生产分析

介绍采用150 mm×150 mm连铸坯、高速线材轧机生产Φ12.5 mm规格预应力82B盘条的试生产情况,对试生产中出现的问题进行分析,并提出了改进意见.     

Effects of welding wire composition and welding process on the weld metal toughness of submerged arc welded pipeline steel

The effects of alloying elements in welding wires and submerged arc welding process on the microstructures and low-temperature impact toughness of weld metals have been investigated.The results indicate that the optimal contents of alloying elements in welding wires can improve the low-temperature impact toughness of weld metals because the proentectoid ferrite and bainite formations can be suppressed,and the fraction of acicular ferrite increases.However,the contents of alloying elements need to vary along with the welding heat input.With the increase in welding heat input,the contents of alloying elements in welding wires need to be increased accordingly.The microstructures mainly consisting of acicular ferrite can be obtained in weld metals after four-wire submerged arc welding using the wires with a low carbon content and appropriate contents of Mn,Mo,Ti-B,Cu,Ni,and RE,resulting in the high low-temperature impact toughness of weld metals.     

工程制图中第三角画法的教学研究

由于经济全球化的影响,我国同国外的工程技术交流日趋频繁,工程图作为重要的工程语言发挥了举足轻重的作用。为了使学生在第一角画法的基础上更好地掌握第三角画法,培养出能够适应国际上使用两种投影制进行图纸交流的技术人才,文章结合企业需求和高校教学特点,重点介绍了第三角画法,并介绍了在教学中采用对比的教学方法,以便更好地掌握两种投影制。     

梳棉机针布齿条的协同设计

针布的设计直接影响到梳棉机的生产质量和产量。分布式同步协同设计可以为梳棉机各配件的模块化设计提供最大限度的设计空间。利用逆向工程技术获取已有产品的CAD数据模型,在此基础上做梳棉机针布的协同设计。采用基于标识码的XML增量数据传输,较大地减少了数据传输量,保证数据的实时传输和模型的同步显示,最终实现了梳棉机针布同步协同...     

海洋废弃平台桩基拆除绳锯机控制系统研发

海洋废弃平台拆除过程中需要切断桩基,水下绳锯机是一种安全环保的桩基切割工具．介绍了绳锯机的工作原理,提出了控制系统的总体结构,设计了控制系统的硬件和软件,实验表明此控制系统能够使绳锯机安全、稳定的工作．     

螺线管式磁感应钢丝绳断丝检测系统设计

针对现有钢丝绳损伤检测采用人工检查或定期换绳的方法,存在效率低、成本浪费严重及安全性差等问题,设计了螺线管式磁感应钢丝绳断丝检测系统。系统检测原理:当钢丝绳出现断丝时,磁导率会相应降低,磁阻变大,电感量减小,从而导致线圈磁场不平衡并产生感应电动势,根据该感应电动势的大小可判断出钢丝绳断丝的状况。试验结果表明,该系统克服了传统电磁检测技术不能精确检测钢丝绳内部出现断丝的缺陷,检测精度可达95%以上。