粗糙表面的分形表征

最近的研究表明，随机粗糙表面是自仿射的多尺度的，因而表面轮廓的高度分布方差，叙率和曲率的方差不再是唯一的。本文基于分形几何理论提出了一种新的粗糙表面表征方法。使用Ｗｅｉｅｒｓｔｒａｓｓ－Ｍａｎｄｅｌｂｒｏｔ函数得到粗糙表面的分形参数－－“固有”参数，而这些参数可以提供任何长度尺度的粗糙度结构信息。     

车削粗糙表面法向接触刚度仿真研究

为准确获取车削粗糙表面法向接触刚度,运用有限元方法开展接触仿真研究.基于车削运动学原理,实现车削表面微观形貌点云数据的获取.运用逆向建模方法实现特征曲面与三维模型的构建.采用ABAQUS有限元仿真软件对三维模型进行接触分析,得到法向接触刚度有限元仿真结果.为验证该文方法的准确性,引入KE模型的理论解析结果进行对比.对比...     

聚烯烃消光膜表面粗糙花纹研究

在固定加工条件和聚丙烯(PP)牌号不变情况下吹塑制备不同配比的聚乙烯/聚丙烯(PE/PP)共混薄膜,使用光学显微镜(OM)和原子力显微镜(AFM)观察膜的表面粗糙花纹和粗糙形态并得到表面粗糙度Ra和峰密度D;由此比较共混体系和单组分体系薄膜的表面粗糙花纹及消光效果,研究PE树脂的熔体指数、支化、共聚组分及PE用量对共混薄膜表面粗糙花纹的影响,并确定聚烯烃薄膜消光性能与表面粗糙花纹的关系。     

粗糙表面可见光散射特性的实验研究

为了获得目标材料表面的散射参数,设计了一种测量粗糙表面散射特性的实验装置,并对几种材料进行了测量.激光器发出的激光经样品反射散射后,被探测器接收,转动转台,完成在入射平面的测量.利用Matlab对实验数据曲线拟合,给出了材料表面散射特性的数学表达式.实验结果表明,散射特性与表面粗糙度和入射角相关.当以中大角度照射时,粗糙表面不再严格遵守朗伯余弦定律,出现非镜向峰值现象,且峰值随着入射角的增大而增大.     

粗糙表面的双相干谱分析

双谱分析是近年发展的一种随机信号的现代分析方法，它保留了信号的相位信息，可以定量描述信号之间的非线性相位耦合；同时具有很强的消噪能力，可以很好地反映信号的非对称特征．正常的加工条件下，表面轮廓符合高斯型分布，因此其双谱为零．但实际加工中，许多表面表现为非高斯型，其双谱不为零，此时可以用双谱分析定量地描述表面轮廓特征的非对称性．然而，用双谱表示灵敏度高、幅值大、不够直观，为了有效地反映表面轮廓的双谱特征，本文采用了双谱的归一化形式——双相干谱分析．最后还通过对几种典型试件的实验，证明了其有效性，并得出了一些有益的结论．     

基于散斑强度相关函数的表面粗糙度测量方法

激光经过被测表面反射和散射后,通过自由空间传播至观察面上形成散斑图像,其统计分布依赖于被测表面的微观形貌。分析此散斑图像的二阶统计特性,导出了强度变化的相关函数和表面粗糙度参数之间的关系。以表面粗糙平均值Ra分别为0.1靘, 0.2靘, 0.4靘和0.8靘的平磨标准金属样块形成的散斑图像为例,根据强度变化相关函数的离散化定义,计算得到该相关函数值。结果表明,表面越粗糙,散斑越分散,强度变化的相关函数波动越大。因此,该参数可以反映不同的粗糙面,用其作为表征表面粗糙度的特征参数,扩大了测量范围。该方法实验系统简单,对于实际测量环境要求不高,对震动不是非常敏感,适于在线测量。     

规则微观结构粗糙表面浸润性研究

制作了4组具有不同规则微观结构、粗糙度为1.2～2.0的粗糙表面,并测量了各个粗糙表面的表观接触角。而后将各组粗糙表面的接触角测量值与Wenzel模型预测值和Cassie模型预测值进行比较,分析了影响各个粗糙表面浸润特性的因素。发现孔状微观结构的粗糙表面与柱状微观结构的粗糙表面的浸润性有很大区别,不同的微观结构导致液体侵入微结构内部程度的不同是引起此区别的主要原因,进而针对这两种不同微观结构的粗糙表面提出了新的预测值计算公式。     

粗糙表面对金属化学腐蚀的影响

对粗糙表面加速金属化学腐蚀的现象进行了热力学分析，结果表明，金属粗糙表面所产生的表面效应致使化学腐蚀反应的吉布斯函数，平衡常数发生改变，金属化学腐蚀速度加快。     

超光滑表面粗糙度测量的研究

本文讨论了对积分散射测量的超光滑表面均方粗糙度进行修正的问题，得出结论：可以直接依赖于散射理论从积分散射测量确定表面粗糙度值。     

利用光散射测表面粗糙度的方法

在这篇文章中概括了大量以前所做的利用光散射测量金属表面粗糙度的试验。也确定了几种测量不同表面粗糙度参数和函数的方法，同时也给出了每种方法的近似范围。利用直接标准，计算光清表面粗糙度，范围从0＜α／λ＜0．05，其中σ是粗糙度均方值，凡是光波长，在这种方法中散射的角分布与粗糙度的功率谱密度密切相关。在此基础上表面目相关函数可以通过范围在0＜α／λ＜0．14之间的角分布付里叶变换计算出。在0＜α／λ＜0．3范围内，光线是可分辨和测量的，对于这种情况给出了镜面反射的方法。对于这些方法和较粗糙的表面，发散宽度的均…     

Light Scattering by Composite Rough Surfaces

Abstract

Light scattering from a dielectric surface with composite roughness is considered, where the surface irregularities are modelled as a superposition of two roughness types of different length scales. Geometrical optics and the Rayleigh-Rice expansion, respectively, are employed in describing the scattering from the two roughness structures. Contrary to previous work, we concentrate on bistatic cross-sections, which are calculated analytically for scattering in the plane of incidence, and resulting plots for various parameter values are shown, especially for small-scale correlation lengths of the order of the wavelength of the incident light. The main effects of the small-scale roughness are an overall decrease of the coherent reflectance and a depolarization of the scattered light, which in the plane of incidence is not present for scattering from a surface with a single scale of roughness. It is, however, concluded that scattering at the surface and volume scattering have to be taken into account in order to explain the experimentally found degrees of depolarization.     

Large-Angle in-Plane Light Scattering from Rough Surfaces: Comment

A recent paper by Karabacak et al. [Appl. Opt. 39, 4658 (2000)], which discussed the scattering from rough surfaces in directions out of the plane of incidence, exhibited an error in the derivation of a polarization factor. An asymmetry in the scattering function for directions out of the plane of incidence and for circularly polarized incident light is predicted by the correct derivation of this factor and can be observed in their data.     

Radiometry of Rough Surfaces

This paper discusses the radiometric properties of perfectly conductive, slightly rough random surfaces. The Kirchhoff approximation, so far used in this kind of study, is analysed. In particular, its inability to construct models of lambertian rough surfaces is pointed out. The small perturbation method, recently put forward, allows the scope and limitations of this approximation to be established. This method also yields exact expressions for the radiant intensity, for either polarized or unpolarized incident radiation and allows the construction of surfaces which produce a lambertian distribution of intensity.     

Mueller-matrix Ellipsometry on Electroformed Rough Surfaces

Abstract

Automated Mueller-matrix ellipsometry was used to investigate the optical properties of electroformed standard rough surfaces as a function of r.m.s. surface roughness heights and angle of incidence. The r.m.s. roughness of the specimens examined varied from 50 to 12 500 nm. Six different surface finishes and 22 different specimens were examined and Mueller matrices were obtained at angles of incidence that varied from 30 to 80°. Measurements were conducted at a wavelength of 633 nm with the use of a division-of-amplitude photopolarimeter capable of simultaneously measuring all four Stokes parameters of arbitrarily polarized light. Values of ψ and Δ, the ellipsometric parameters, were derived from the measured Mueller matrices. The results demonstrate firstly the monotonic variations in the derived values of Δ with surface roughness for fixed angles of incidence, which include a ‘resonance’ effect for specimens with r.m.s. roughness heights close to the wavelength of light, secondly a systematic variation of ψ with the angle of incidence for different specimen roughness values and a reversal in these trends beyond the pseudo-Brewster angle, thirdly a monotonic variation in Δ values with the angle of incidence for different roughness values, fourthly relatively large variations in ψ values for roughness values close to the wavelength of light and fifthly relatively little change in ψ and Δ values for roughness values that greatly exceeded the wavelength of light.     

Switchable Adhesion of Micropillar Adhesive on Rough Surfaces

Switchable structured adhesion on rough surfaces is highly desired for a wide range of applications. Combing the advantages of gecko seta and creeper root, a switchable fibrillar adhesive composed of polyurethane (PU) as the backing layer and graphene/shape memory polymer (GSMP) as the pillar array is developed. The photothermal effect of graphene (under UV irradiation) changes GSMP micropillars into the viscoelastic state, allowing easy and intimate contact on surfaces with a wide range of roughness. By controlling the phase state of GSMP via UV irradiation during detachment, the GSMP micropillar array can be switched between the robust‐adhesion state (UV off) and low‐adhesion state (UV on). The state of GSMP micropillars determines the adhesion force capacity and the stress distribution at the detaching interface, and therefore the adhesion performance. The PU‐GSMP adhesive achieves large adhesion strength (278 kPa), high switching ratio (29), and fast switching (10 s) at the same time. The results suggest a design principle for bioinspired structured adhesives, especially for reversible adhesion on surfaces with a wide range of roughness.     

随机结构粗糙表面的湿润性研究

依据荷叶表面具有的不规则自相似微纳双重结构,引入分形几何学构造类似荷叶的随机分形结构,建立相应的Cassie、Wenzel模型接触角方程,分析随机分形结构的分形维数和结构参数对其润湿性的影响。结果表明:分形结构表面的分形维数越大,结构越致密,接触角越大;分形结构中微/纳尺度参数之比越大,接触角也越大。然而,随机结构即使分形维数趋于最大的3.0,Wenzel模型表观接触角也不能达到超疏水的150°,Cassie模型最大表现接触角大于150°;更适合用于制备超疏水表面。     

Spectral Radiative Properties of Two-Dimensional Rough Surfaces

Spectral radiative properties of two-dimensional rough surfaces are important for both academic research and practical applications. Besides material properties, surface structures have impact on the spectral radiative properties of rough surfaces. Based on the finite difference time domain algorithm, this paper studies the spectral energy propagation process on a two-dimensional rough surface and analyzes the effect of different factors such as the surface structure, angle, and polarization state of the incident wave on the spectral radiative properties of the two-dimensional rough surface. To quantitatively investigate the spatial distribution of energy reflected from the rough surface, the concept of the bidirectional reflectance distribution function is introduced. Correlation analysis between the reflectance and different impact factors is conducted to evaluate the influence degree. Comparison between the theoretical and experimental data is given to elucidate the accuracy of the computational code. This study is beneficial to optimizing the surface structures of optoelectronic devices such as solar cells.     

Transport in Mesoscopic 3He Films on Rough Surfaces

Measurements of the flow of thick ³He films over a highly polished silver surface, using a high precision torsional oscillator, have found unexpectedly long momentum relaxation times (Casey et al., Phys. Rev. Lett. 92, 255301, 2004). This results in a decoupling of the normal state helium film from the oscillator motion at low temperatures. In the ballistic regime the relaxation rate varies linearly with temperature. This result is explained by a theory in which the effect of surface roughness is incorporated into the transport equation as a disorder potential (Meyerovich and Stepaniants, J. Phys., Condens. Matter 12, 5575, 2000). This potential is fully characterised experimentally by AFM measurements of the surface roughness power spectrum, which we find to have a stretched exponential form. Incorporating the measured spectrum into the theory allows a direct comparison with the observed relaxation rate, with good agreement. The anomalous temperature dependence of the relaxation rate is accounted for by interference between bulk inelastic scattering and this weak surface elastic scattering. Decorating the substrate with scattering centres restores film-substrate coupling at the measurement frequency of 2.5 kHz. These results on the nature of quasiparticle scattering at rough surfaces may have implications in the understanding of the effects of confinement on superfluid ³He.