Bartkowiak Tomasz, Berglund Johan, Brown Christopher A
Institute of Mechanical Technology, Poznan University of Technology, 60-965 Poznań, Poland.
Department of Manufacturing, RISE Research Institutes of Sweden, SE-43153 Mölndal, Sweden.
Materials (Basel). 2020 Jul 7;13(13):3028. doi: 10.3390/ma13133028.
Anisotropy can influence surface function and can be an indication of processing. These influences and indications include friction, wetting, and microwear. This article studies two methods for multiscale quantification and visualization of anisotropy. One uses multiscale curvature tensor analysis and shows anisotropy in horizontal coordinates i.e., topocentric. The other uses multiple bandpass filters (also known as sliding bandpass filters) applied prior to calculating anisotropy parameters, texture aspect ratios (Str) and texture directions (Std), showing anisotropy in horizontal directions only. Topographies were studied on two milled steel surfaces, one convex with an evident large scale, cylindrical form anisotropy, the other nominally flat with smaller scale anisotropies; a µEDMed surface, an example of an isotropic surface; and an additively manufactured surface with pillar-like features. Curvature tensors contain the two principal curvatures, i.e., maximum and minimum curvatures, which are orthogonal, and their directions, at each location. Principal directions are plotted for each calculated location on each surface, at each scale considered. Histograms in horizontal coordinates show altitude and azimuth angles of principal curvatures, elucidating dominant texture directions at each scale. Str and Std do not show vertical components, i.e., altitudes, of anisotropy. Changes of anisotropy with scale categorically failed to be detected by traditional characterization methods used conventionally. These multiscale methods show clearly in several representations that anisotropy changes with scale on actual surface measurements with markedly different anisotropies.
各向异性会影响表面功能，并且可以作为加工过程的一种指示。这些影响和指示包括摩擦、润湿性和微磨损。本文研究了两种用于多尺度量化和可视化各向异性的方法。一种方法使用多尺度曲率张量分析，并在水平坐标（即地形中心坐标）中显示各向异性。另一种方法在计算各向异性参数、纹理长宽比（Str）和纹理方向（Std）之前，使用多个带通滤波器（也称为滑动带通滤波器），仅在水平方向上显示各向异性。研究了两种铣削钢表面的形貌，一种是凸面，具有明显的大尺度圆柱形状各向异性，另一种名义上是平面，具有较小尺度的各向异性；一个微电火花加工表面，作为各向同性表面的一个例子；以及一个具有柱状特征的增材制造表面。曲率张量包含两个主曲率，即最大曲率和最小曲率，它们在每个位置都是正交的，以及它们的方向。在每个考虑的尺度上，为每个表面上的每个计算位置绘制主方向。水平坐标中的直方图显示了主曲率的高度和方位角，阐明了每个尺度上的主导纹理方向。Str和Std不显示各向异性的垂直分量，即高度。传统上使用的传统表征方法完全无法检测到各向异性随尺度的变化。这些多尺度方法在几种表示中清楚地表明，在具有明显不同各向异性的实际表面测量中，各向异性随尺度而变化。
