粗糙纹理表面数字化模拟

粗糙表面的数字模拟是工件接触性能研究的前提与基础,而现有的粗糙表面模拟方法缺乏对表面纹理的考虑,为此提出了一种粗糙纹理表面数字化模拟方法.该方法通过数字化滤波模拟生成设定自相关函数的粗糙表面,同时模拟生成设定纹理参数的纹理表面,对粗糙表面和纹理表面进行归一化处理后,通过对纹理表面添加比例因子,将两表面进行合成处理,得到...     

球头铣刀加工表面纹理预测与分析

为了预测球头铣刀加工表面纹理特征,针对球头铣刀几何特点,建立表面形貌仿真模型,对影响表面纹理的主要因素进行了分析,并通过仿真和试验研究了每齿进给量fz、行距p、恒定相位差Δθ的不同组合对切削加工表面纹理分布与方向的影响规律。结果表明:不同的加工参数组合下表面纹理形式有所不同,加工参数相同时相位差的变化导致表面纹理分布与方向发生改变,试验结果与仿真结果具有很好的一致性。研究结果为预测表面纹理提供了依据。     

表面检测中微小缺陷的识别

在表面缺陷检测中,针对光照不均或有纹理的产品上微小缺陷难于识别的问题,提出了一种新的视觉识别方法.该方法首先计算产品表面图像中每行和每列的灰度标准差,然后根据标准差的相对变化量判别缺陷,并确定缺陷的坐标.实验结果表明,该方法能准确识别和定位产品表面的微小缺陷.     

基于分数布朗运动的工件表面图像分析及其在刀具状态检测中的应用

介绍了刀具磨损状态的检测方法和分数布朗运动(FBM)的基本理论。应用分数布朗运动场模型对切削工件的表面图像进行纹理分析,提取纹理特征后,根据分形维数D和图像上对数功率谱的拟合曲线的平均斜率k来判断刀具的磨损状态。与实验得到的结果相比较,该方法的结果令人满意。     

激光表面纹理加工对Ti6Al4V空蚀性能的影响

采用激光表面改性的方法对Ti6Al4V合金进行纹理加工。采用表面粗糙度测试仪、接触角测量仪和X射线衍射仪对激光纹理加工试样的表面特性进行表征,采用磁致伸缩超声振动仪对试样的抗空蚀特性进行测试,采用光学显微镜和扫描电子显微镜对试样空蚀前、后的表面形貌进行观测。结果表明:经激光表面纹理加工,试样的硬度由337HV提高到550HV,水接触角增大10°;激光纹理加工试样的抗空蚀特性有所改善,特别是对于具有较小间距网格形状的表面纹理试样,其表面空蚀面积的比例小于抛光试样的1/10;激光纹理加工试样的抗空蚀特性的改善与硬度梯度效应、缓冲空泡运动和限域作用等效应相关。     

接触表面性质对圆柱滚子轴承混合润滑的影响

目的为了提高圆柱滚子轴承的润滑性能,研究滚子与外圈表面纹理及硬弹比对圆柱滚子轴承混合润滑的影响。方法基于平均流量模型、非牛顿效应、热效应和粗糙峰的弹塑性变形,建立了圆柱滚子轴承有限长线接触热混合润滑模型。研究了表面纹理及硬弹比对膜厚、膜厚比、载荷比、平均摩擦系数及最高温度的影响。结果随着表面纹理参数的增大,油膜厚度逐渐减小,粗糙峰接触压力、平均摩擦系数和载荷比逐渐增,最高温度先减小后增大,最小膜厚先增大后减小。但表面纹理参数小于1/3时,对最小膜厚的影响非常小。表面硬度引起的完全塑性变形、弹塑性和塑性变形、完全弹塑性变形对润滑状态的影响不同。在硬弹比处于0.01～0.03时,粗糙峰同时发生弹塑性和塑性变形,油膜厚度、最小膜厚、载荷比、平均摩擦系数、粗糙峰接触压力及最高温度不随表面硬度而变化。当硬弹比小于0.01时,粗糙峰产生完全塑性变形;当硬弹比大于0.03时,粗糙峰发生完全弹塑性变形。这两种情况的载荷比、平均摩擦系数、粗糙峰接触压力及最高温度均随着表面硬弹比的增大而增大。在不同工况下,表面硬度与表面纹理参数对圆柱滚子轴承润滑状态的影响存在差异。在表面纹理参数小于1/3时,表面硬度的影响占主导地位;在表面纹理参数大于1.0时,表面纹理参数的影响占据主导地位。结论表面纹理参数等于1.0时,润滑状态最好;硬弹比处于0.01～0.03时,综合润滑性能最好。在不同条件下,表面纹理参数与表面硬度对润滑影响的程度不同。因此,圆柱滚子轴承混合润滑中,存在最佳的表面纹理参数和表面硬弹比。     

仿古地板表面自动加工专用机床的设计

分析仿古地板表面纹理加工工艺特点,设计一种仿古地板表面纹理自动加工专用机床。该专用机床采用模块化组合设计,由进料机构、出料机构和单模组加工单元组成。单模组加工单元由机架、传送装置、压紧装置、浮料装置、台板装置和切削系统组成,其中切削系统采用一轴多刀的结构。通过控制系统控制刀轴升降和刮铣刀在刀轴上有规律、无相关性地摆动,从而在木地板表面上加工出仿古纹理的效果。该机床结构紧凑,生产效率高,可降低企业的劳动力成本,增加企业的产能。     

基于计算机视觉表面粗糙度的自动测量方法

提出了一种基于计算机视觉的机械加工表面粗糙度非接触测量的新方法,采用A102fCCD数字摄像头作为图像传感器,利用数字图像处理技术对机械加工表面粗糙度进行测量.分析了图像处理过程,根据处理后的图像推导出所对应的表面粗糙度.实验证明,该算法能正确识别不同的机械加工表面,并具有较高的精度.     

表面纹理和表面膜对Ti6Al4V合金空蚀特性的影响

为研究表面纹理和表面膜对材料抗空蚀特性的影响,采用激光表面改性的方法对Ti6Al4V合金进行纹理加工,在纹理加工试样上采用自组装技术制备自组装分子膜。采用接触角测量表征试样的表面特性,通过对试样的抗空蚀特性进行测试和对试样空蚀前后的表面形貌进行观测,分析试样的空蚀发生机制。结果表明,Ti6Al4V试样上激光加工表面纹理可显著提高其抗空蚀能力,纹理加工试样上制备自组装分子膜,由于具有疏水特性可以进一步改善试样的抗空蚀能力;网格纹理试样的抗空蚀能力由于表面硬度高、硬度梯度大及突起高硬度点分布均匀而强于直线纹理试样;沉积薄膜纹理试样的抗空蚀能力随着间距的增大而增大,未沉积薄膜试样的抗空蚀能力随着间距的增大而减小。     

医用钛植入体激光微纹理生物性能研究进展

医用钛合金具有强度高、弹性模量低、疲劳性能好、密度最接近人骨等优点,被广泛应用于临床医学牙科和骨移植等领域。目前较常用的医用钛合金表面加工方法包括机械加工、酸蚀、喷砂、等离子喷涂和激光加工等。通过对比分析,激光加工表现出明显优势,与化学或传统物理加工方法相比,采用激光加工医用钛植入体表面具有高效、清洁、准确、柔性等优势。应用各类脉冲激光器,可以在植入体表面加工特定的表面纹理和纹理组合,改善植入体的生物相容性。归纳了植入体表面纹理对植入环境的影响,表面纹理形状、粗糙度和润湿性等表面特性直接影响细胞组织的黏附、生长和增殖,对细胞生长具有接触导向作用。通过调控激光通量、脉冲频率、扫描速度和脉冲宽度等激光参量可对表面纹理的规则性、准确性、尺寸、氧化程度等特征产生不同影响,进而影响医用钛植入体的表面微观形貌、粗糙度、硬度和润湿性,使其在生物环境中获得更好的服役性能。通过激光加工获得的理想医用钛植入体表面可有效避免植入体表面细菌的滋生,降低发病率,提高植入成功率。经激光加工后,医用钛植入体表面会出现不同程度的裂纹,导致在服役过程中植入体表面产生的摩擦碎屑对植入体环境造成不良影响。通过综述以上各方面的研究进展可知,随着超短脉冲激光技术的发展和新型医用植入体材料β钛合金制备技术与工艺的完善,经激光加工后植入体将获得更理想的表面特性和服役性能。     

超疏水表面抑制结霜研究进展

超疏水表面以其超高的表观接触角和很小的滚动角在工业中获得广泛的应用。综述了近期国内外超疏水表面在抑霜方面的研究新进展,归纳了超疏水表面的冷凝、结冰和落霜过程的过程特点和疏水性对结霜过程的影响。超疏水表面能显著延迟冷凝发生和开始结霜的时间,降低霜层的厚度。与普通表面相比,超疏水表面的霜层结构更为蓬松脆弱,可在外力作用下轻松去除,表现出较好的抑霜性能。由于部分超疏水表面在冷凝阶段丧失疏水性从而丧失抑霜性能,大大地限制了超疏水表面在抑制结霜方面的潜力。纳米结构超疏水表面较好地解决了上述问题,一部分纳米表面由于冷凝液滴的弹跳现象而表现出极佳的抑霜性能。最后,对超疏水表面研究的发展进行了展望。     

Design and development of nanofinishing process for 3D surfaces using ball end MR finishing tool

A new precision finishing process for nanofinishing of 3D surfaces using ball end MR finishing tool is developed. The newly developed finishing process is used to finish ferromagnetic as well as nonmagnetic materials of 3D shapes using specially prepared magnetorheological polishing (MRP) fluid. The existing MR finishing devices and methods are likely to incapable of finish 3D intricate surfaces such as grooves in workpiece or complex in-depth profiles in the mold due to restriction on relative movement of finishing medium and workpiece. In this newly developed finishing device, the ball end MR finishing tool is used for finishing different kinds of 3D surfaces, as there is no limitation on relative movement of finishing medium and workpiece. It can finish the work surfaces similarly as the machining of 3D surfaces by CNC ball end milling cutter and open a new era of its applications in future. The developed process may have its potential applications in aerospace, automotive and molds manufacturing industries. A computer controlled experimental setup is designed and manufactured to study the process characteristics and performance. The magnetostatic simulations were done on ferromagnetic as well as nonferromagnetic materials of 3D surfaces to observe the ball end shape of magnetic field at the tip of the MR finishing tool. The experiments were performed on flat EN31 and groove surface of copper workpieces in the developed MR finishing setup to study the effect of finishing time on final surface roughness.     

Laser solidification of conductive composites on a fabric surface

Selective laser solidification of conductive composites on rough fabric surfaces for electric circuit boards was carried out. This process has been used for flat, smooth, heat resistant surfaces, such as glass or silicon. However, there are currently numerous applications of printed or fabricated conductive lines for circuit boards on flexible and rough surfaces, and many of them have not been investigated for selective laser solidification. In our study, conductive paste containing nanoparticles that become a conductive layer when solidified was applied to a fabric substrate, and a laser beam was irradiated on the surface to fabricate a conductive line. Conductive lines with low electrical resistance were successfully achieved on the fabric surface. An experimental study and theoretical analysis of solidifying pastes with conductive nanoparticles is presented, and its process characteristics are discussed.     

Sink electrical discharge machining of hydrophobic surfaces

The phenomenon of hydrophobicity observed in such surfaces as lotus leaves is typically manifest by hierarchical structures on low-energy surfaces. Sustained interest in fabricating hydrophobic surfaces has resulted in a myriad of processes, which are but limited by their largely referring to soft materials and/or involving multiple process steps. The present work explored the application of electrical discharge machining (EDM) for the single-step manufacture of durable, metallic hydrophobic surfaces. Simple sink EDM in a hydrocarbon dielectric, with no special process kinematic or tooling requirements, is demonstrated to rapidly generate surfaces that are intrinsically water repellent, with contact angles approaching 150°.     

再谈斜轧轧辊与轧件线接触的几何条件——斜轧扩径机和斜轧减径机的几何模型(下)

在研究斜轧过程的4个基本数学方程的基础上,进一步讨论了两个回转曲面线接触的几何条件,以及由此条件推导的已知其中一个曲面求解另一个回转曲面的数学方程;再运用所获得的数学方程,讨论了斜轧扩径机和斜轧减径机的几何模型,探讨实现斜轧减径过程的可能性。     

再谈斜轧轧辊与轧件线接触的几何条件(上)——斜轧扩径机和斜轧减径机的几何模型

在研究斜轧过程的4个基本数学方程的基础上,进一步讨论了两个回转曲面线接触的几何条件,以及由此条件推导的已知其中一个曲面求解另一个回转曲面的数学方程;再运用所获得的数学方程,讨论了斜轧扩径机和斜轧减径机的几何模型,探讨实现斜轧减径过程的可能性.     

Contents

The attempts of researchers to obtain accurate and high-quality surfaces have led to the invention of new methods of finishing. Magnetic abrasive finishing (MAF) is a relatively new type in which magnetic field is used to control the abrasive tools. Surfaces of moulds, for instance, are among those which require very high-surface smoothness. Usually, this type of part has freeform surfaces. In this study, the effect of magnetic abrasive process parameters on finishing freeform surfaces of aluminium parts has been examined. This method was achieved through a combination of the magnetic abrasive process and computer numerical control. The use of a simple hemisphere to be joined on the flat area of the magnet as well as spark machining for forming a sphere at the end of a magnet were performed during experimentation. Gap, rotational speed of the machining head, amount of abrasive powder and feed rate were among the parameters that were tested in experiments. The design of experiments is based on the response surface methodology. Significant parameters and the regression equations governing the process were also determined. The impact of intensity of the magnetic field was obtained using MAXWELL finite element software. In the MAF process, magnetic abrasives play the role of cutting tools. However, the magnetic abrasives are not easily available as these are produced by special techniques such as sintering method, adhesive based, plasma based or gel based. This study presents the basic polishing characteristics of the magnetic abrasives produced by the mechanical alloying process. After the mechanical alloying process fine magnetic abrasives are obtained, in which the abrasive particles adhere to the base metal matrix without any bonding material. In this study, investigation was performed only on the convex area of workpiece. Optimum parameters are gap size of 0.5?mm, feed rate of 10?mm?min^?1 rotational speed of 2100?rev?min^?1 and powder amount of 1.75?g. To help understand the effectiveness of the MAF process, scanning electron microscopy and atomic force microscopy of the machined surfaces have been carried out.     

铝及其合金微弧氧化技术的研究与进展

微弧氧化是一种在Al、Mg、Ti等有色金属及其合金材料表面原位产生陶瓷层的表面强化技术。利用该技术可以在这些有色金属表面生成耐磨、耐蚀以及电绝缘性能优异的陶瓷层。本文介绍了铝及其合金微弧氧化的基本原理、工艺特点、微弧氧化陶瓷层的结构和性能特点，并展望了微弧氧化技术的应用前景和发展趋势。     

DEVELOPMENT OF FRASTA SIMULATION SOFTWARE

Fracture-surface topography analysis （FRASTA） was successfully used to simulate the process of crack and calculate parameters of crack such as the crack opening angle （COA） and crack-tip opening angle （CTOA）. But because the amount of calculation is large, errors are often made during the course of calculation. FRASTA simulation software, namely fracture surface analyst （FSA ） is developed and a series of center-cracked tension （CCT） and double edge notched （DEN） specimens of different materials with different sizes are tested, their fracture surfaces are scanned by non-contact 319 scanning system and the elevation data of the fracture surfaces is recorded. FSA used the recorded elevation data of fracture surfaces to simulate the process of crack based on the principle of FRASTA. Results show that FSA can accurately simulate the process and calculate the parameters of crack.     

Nucleation and Growth of Zinc Electrodeposited onto Electropolished and Mechanically Polished Steel Surfaces

Nucleation and growth of zinc electrodeposition in acid sulphate bath on electropolished and mechanically polished low carbon steel surfaces was investigated. On both surfaces thin η-zine crystals were stacked on each other, although their orientation was different. Potentiostatic current-time plots and cyclic voltammetry were used to study the nucleation process. The results indicated that at pH 2 the nucleation process on both surfaces um instantaneous, and that the growth process was charge transfer controlled. The growth rate on the electropolished surface was higher than the mechanically polished surface under the same electrochemical conditions. Increasing temperature did not affect the nucleation mode; it only increased the growth rate. Increasing the pH from 2 to 4 caused deviation from instantaneous nucleation, so that on the mechanically polished surface the nucleation mode was fully progressive. The reason for this behavior was attributed to the number density of active nucleation sites on the steel surface. Cyclic voltammetry also confirmed the hydroxide layer formation model.