Nd：YAG激光毛化方法在金属薄板冷轧生产中的应用

用Ｎｄ；ＹＡＧ激光毛化冷轧工作辊，即可以精确改变轧辊的表面形貌，获得设定粗糙度，又可以通过快速熔凝使辊面得到强韧化。在金属薄板的冷轧和平整生产中采用激光毛化工作辊，其使用效果明显优于目前常用的喷丸毛化轧辊，其使用寿命也明显延长。     

轧辊表面激光毛化技术及装备

针对轧辊表面激光毛化的特点,探讨了轧辊表面激光毛化技术及装备的发展现状及趋势,分析了轧辊表面激光毛化脉冲装置的原理、结构和特点,指出了轧辊表面激光毛化技术及装备的难点技术及可能的解决方法。     

光纤激光无序毛化

为了提高轧辊表面强度,减小应力集中,延长轧辊寿命,利用光纤激光毛化设备对轧辊表面进行无序毛化。研究了激光功率、轧辊转速、激光头平移速度以及脉冲频率对无序毛化点分布的影响,提出了四种无序毛化的方法,即:速度调试法、频率调试法、外部调试法和综合调试法。实验结果表明,四种方法都可以实现无序毛化,其中综合调试法无序化程度更大,毛化质量最佳。研究结果已应用于实际生产。     

轧辊表面球冠状微凸形貌的激光加工

随着汽车工业的飞速发展,对冷轧薄板表面质量特别是表面微观形貌提出了更加严格的要求。本文针对从摩擦学角度优化设计的轧辊表面球冠状微凸新形貌,依据脉冲激光参数特性及快速熔凝理论,提出了脉冲激光毛化处理的新机制。试验中,采用500W脉冲Nd:YAG固体激光器对轧辊表面进行毛化处理,通过对激光毛化新机制的分析和研究,很好的选取和匹配了激光加工工艺过程和脉冲激光参数,最终成功获得了预先设计的形貌及尺寸。并进一步对其表面硬度状况进行了测量和分析。研究表明,辊面形貌和粗糙度能够得到精确的控制;微凸的激光毛化新形貌具有高于材料基体的表面硬度。此外还对脉冲激光参数对轧辊主要形貌参数的影响规律作了进一步的分析和研究。     

光纤激光轧辊毛化工艺参数研究

针对CO₂激光器和YAG激光器的种种不足,采用光纤激光毛化柔性工作站,对轧辊表面进行了不同尺寸和分布的毛化点彤貌加工。分析了光纤激光功率、脉冲频率、脉冲宽度、扫描速度、离焦量等工艺参数对毛化点形貌的影响。结果表明:通过合理匹配毛化工艺参数,能够得到精确可控的轧辊毛化形貌和满足生产要求的粗糙度,也可以实现相对无序的毛化点排列。     

版辊激光加工的方法和设备

介绍一种版辊激光加工的方法和设备。该设备可应用于冶金，印刷，皮革，纺织，装饰等领域中版辊的制作，也可用于进行激光毛化。     

圆锥轧辊激光毛化加工研究

在圆锥轧辊轧制带钢时,为了增强轧辊与带钢之间的摩擦力,采用对轧辊表面进行激光毛化的方法,对圆锥轧辊的激光毛化加工过程进行了分析研究,给出加工系统的硬件组成,介绍了加工系统的控制原理。由于在圆锥轧辊表面进行激光毛化属于变径加工,为了保证每个加工圆周处毛化点之间的点距不变,推导出每个加工圆周处圆周直径、总脉冲个数和分频系数等的计算公式,同时给出相应算法,解决了每个加工圆周处最后1个毛化点与第1个毛化点之间间距总是大于点距的问题。结果表明,在圆锥轧辊表面进行激光毛化,不仅增强了轧辊与带钢之间的摩擦力,同时还延长了轧辊的使用寿命。     

光纤激光毛化机器人系统

光纤激光作为第三代激光技术的代表,具有其他激光器无可比拟的技术优越性和广阔的应用发展空间,将可能会逐步取代全球大部分高功率CO₂激光器和绝大部分YAG激光器。本文利用光纤激光器的优点,集成开发了了第五代全新的光纤激光机器人毛化系统,系统以光纤激光器为载体,协同机器人及其它设备来完成轧辊毛化作业。光纤激光毛化柔性工作站与传统的CO₂激光毛化设备相比取得了多项重大突破,如系统采用普通机床代替昂贵的磨床实现毛化功能,是一项开创性的工作,意味着节约大量的设备投资费用,并大幅度提高生产效率;系统对轧辊旋转时的轴向跳动容忍度大,毛化速度可以大幅度的提高;光纤激光毛化技术可实现毛化点形貌的任意设计以及毛化点的有序、无序排列;毛化成本大幅度降低,没有三废,是一种绿色制造技术。     

激光毛化技术将大显神威

中科院力学所产学研激光手化技术推广中心，为上海宝钢研制的“ＹＡＧ激光毛化冷轧辊工业试验装各，”前不久顺利通过宝钢技术部主持的验收。宝钢是我国特大型钢铁企业，该激光毛化冷轧辊工业试验成功，标志着用高新技术武装国有大型企业初见成效，激光毛化技术将大显神威。据杨明江研究员介绍，他们从１９９６年开始为研制宝钢的ＹＡＧ激光毛化冷轧辊工业试验装备，分两个阶段进行：第一阶段，进行了分体毛化装备试验，取得了大型轧辊毛化的重要经验；第二阶段，研制整体式激光毛化装备。从１９９８年底起激光毛化冷轧辊上机试轧，到验收时…     

轧辊表面光纤激光毛化工艺研究

利用光纤激光柔性工作站对轧辊表面进行毛化,研究了激光射出头姿态、侧吹角对毛化点形貌、毛化后轧辊表面粗糙度的影响,分析了其影响规律,总结出了最佳毛化工艺.结果表明,12点位置和3点位置在特定侧吹角度时,毛化点分布相对独立,凸台金属分布集中,无点与点搭接现象,毛化点形貌满足要求.12点位置和9点位置各侧吹角度下的毛化表面粗糙度均满足要求.综合对毛花点形貌及毛化后轧辊表面粗糙度要求,12点位置的毛化效果优于3点位置.研究结果已应用于实际生产.     

纽扣式雷电分流条对雷达天线罩的传输影响分析

传统的金属雷电分流条难以满足高频雷达天线罩的电磁波传输要求,而纽扣式分流条可以兼顾防雷和电磁波传输。通过仿真和试验对比分析雷电分流条的电磁波传输特性,使分流条电磁波传输性能研究模型化。分析纽扣式分流条的电磁波传输机理,同时研究金属片形状、金属片间距和天线频率对雷达罩电磁波传输性能的影响。结果表明:金属分流条对雷达罩的电磁波传输性能影响严重,合理设计的纽扣式分流条可以有效传输电磁波;纽扣式分流条的金属片形状对电磁波传输影响明显,金属片横向越宽,对电磁波传输影响越大,圆形结构电磁波传输性能最差,窄菱形结构电磁波传输性能最好;纽扣式分流条的金属片间距对雷达罩的电磁波传输影响不大,主要影响其击穿电压;同一形式的纽扣式分流条,天线频率越高,电磁波传输性越差。     

Transmission-Line Properties of Parallel Strips Separated by a Dielectric Sheet

A transmission line is made of a symmetrical pair of strip conductors, or a single strip and a ground plane, on opposite faces of a sheet of dielectric material. There is computed, to a close approximation, the relations among the dielectric constant of the sheet, the effective dielectric constant of the sheet and the empty space, the shape ratio, and the wave resistance, for the entire range of possible values. These relations are summarized in a graphical chart covering the range of practical interest. The computation is based on conformal mapping of the dielectric boundary on coordinates such that its effect can be most closely evaluated by simple principles. All relations are approximated in terms of ordinary functions (exponential and hyperbolic). Of particular interest is the effective filling fraction of the dielectric material, which depends mainly on the shape ratio and only slightly on the dielectric constant. Explicit formulas are given for analysis or synthesis.     

Comments on "Upper Bound Calculations on Capacitance of Microstrip Line using Variational Method and Spectral Domain Approach"

The author read with interest the above paper in whkh an analytical approach based on the Fourier transformation and variational techniques have been employed; the surface potentiaf V(x) of the dielectric sheet in order to find the upper bound of the microstrip line capacitance C has been used. Thus this approach complements that of Yamashita et al, who calculated the lower bound C/sup L) dealing with the charge density Q(x) on the surface of the conductor strip; consequently, the margins of error in the variational calculation can be estimated.     

两种张紧辊负荷平衡控制原理及差异分析

文章通过张紧辊负荷平衡控制的两种不同思路,阐述了两种控制方式的原理,并就两者的特点和区别进行了说明,借助例子阐明了实际应用中的注意事项。负荷平衡控制方式一的基本思路是在保证辊子不打滑情况下提供所需张力,各马达间负荷比例随前后张力的不同并不能始终保持相同或相近。负荷平衡控制方式二的基本思路是借鉴马达串联运行控制,设定一个主马达,其它马达的负荷按照主马达的负载百分比进行控制,从而实现各马达功率输出比例的一致。这种方式控制原理简单直观,每台马达都发挥出其最大功率。     

TM scattering by an impedance sheet extension of a paraboliccylinder

An integral equation and method of moments (MM) solution are presented for the two-dimensional (2-D) problem of transverse magnetic (TM) scattering by an impedance-sheet extension of a perfectly conducting parabolic cylinder. An integral equation is formulated for a dielectric cylinder of general cross section in the presence of a perfectly conducting parabolic cylinder. It is then shown that the solution for a general dielectric cylinder considerably simplifies for the special case of TM scattering by a thin multilayered dielectric strip that can be represented as an impedance sheet. The solution is termed an MM/Green's function solution, where the unknowns in the integral equation are the electric surface currents flowing in the impedance sheet; the presence of the parabolic cylinder is accounted for by including its Green's function in the kernel of the integral equation. The MM solution is briefly reviewed, and expressions for the elements in the matrix equation and the scattered fields are given. Sample numerical results are provided     

Upper Bound Calculations on Capacitance of Microstrip Line Using Variational Method and Spectral Domain Approach

In this paper, the authors have employed an analytical approach based on the Fourier transformation and variational techniques in terms of the surface potential of the dielecric sheet to find the upper bounds of the microstrip line capacitance. It is hoped that our work will complement that of Yamashita et al., who calculated the lower bounds dealing with the charge density on the surface of the conductor strip, in estimating the margins of error in calculation.     

TE characterization of resistive strip gratings on a dielectricslab using a single edge-mode expansion

Closed-form expressions are derived for the TE scattering by a narrow resistive strip array in the presence of a dielectric slab. This is accomplished by introducing a single edge-mode expansion to represent the strip current density followed by a Galerkin's solution of the pertinent integral equation. The accuracy of the derived approximate expressions are examined by comparison with a moment method solution and several curves are shown, illustrating how the different array parameters affect the reflectivity and transmissivity of the array. Particular attention is given to the free-standing resistive strip array where an equivalent uniform resistive sheet is constructed for simulating the original periodic structure. The reactance of this equivalent sheet is compared with published expressions pertinent to the metallic strip array     

On the edge reflections of high-frequency surface currents inducedon a cylindrical strip

High-frequency surface currents induced on a surface with edges can be interpreted as being composed of components attributable to the reflections and edge or surface diffractions of the incident field as well as to the edge reflections of these components themselves. The explicit expressions of the former components can be obtained from a set of properly formulated canonical problems if the surface consists of a cylindrically or spherically curved sheet. These types of canonical problems are not suitable for the derivation of the edge-reflected components, a fact that should be considered in dealing with currents induced on sheets of finite extent. A conjecture is made about the edge-reflected currents induced on a cylindrically curved sheet, and some of its consequences are shown. The normal and oblique incidence cases are considered separately     

Impedance boundary conditions for finite planar and curved frequency selective surfaces

We consider the time-harmonic electromagnetic scattering problem from a finite planar or curved, infinitesimally thin, frequency selective surface (FSS), the periodic unit cells of which are constituted, exclusively, by electric conductors and free-space. In order to avoid the meshing of these cells, the problem is solved by employing an integral equation formulation in conjunction with approximate impedance boundary conditions (IBC) prescribed on the sheet that models the FSS. The impedance in the IBC is derived from the exact reflection coefficient calculated, for the fundamental Floquet mode, on the infinite planar FSS illuminated by a plane-wave at a given incidence. When the FSS is curved, and/or the direction of the incident wave is unknown, higher order IBCs are proposed that are valid in a large angular range and can be implemented in a standard method of moments formulation. Also, a simple technique is presented that allows to reproduce the radiating Floquet modes in the scattered field even though those are not accounted for in these IBCs. Their numerical efficiencies are evaluated for a curved strip grating translationally invariant along one direction. Finally, we present an alternative approach where the impedance is approximated by its truncated Fourier series, that considerably enhances the accuracy of the results at the cost, however, of a denser mesh of the sheet.     

Backscattering from resistive strips

Strips made of a resistive sheet material have lower backscattering cross sections than the corresponding perfectly conducting strips, and this is true in particular when the illumination is edge-on with the electric vector parallel to the edge. Attention is focused on this case. Using the moment method applied to an appropriate integral equation, data are obtained for the surface field and backscattered far field of a resistive strip for a variety of strip widthswand uniform resistancesR. The front- and rear-edge contributions to the far field are then extracted. It is shown that for strips whose width is greater than about a half-wavelength the former is the same as for a half-plane having the same resistance, whereas the latter is proportional to the square of the current at that point on the half-plane corresponding to the rear edge of the strip. The implications of these results on the selection of a strip resistance for low backscattering are discussed.