基于分块迭代函数系统的缸套表面织构的分形表征

Fractal Characterization on Surface Texture of Cylinder Liner Based on Partitioned Iterated Function System

表面织构的物理特征是影响活塞组件-缸套系统摩擦学特性和织构减摩效应的关键因素。为了准确有效地描述活塞组件-缸套系统减摩织构的物理特征,提出一种基于曲波变换和分块迭代函数系统(Partitioned iterated function system,PIFS)的减摩织构物理特征的定量表征方法。从活塞组件-缸套系统减摩织构表面的灰度图像出发,运用离散曲波变换方法对减摩织构表面的灰度图像在各个方向上进行多尺度分离。研究与减摩织构物理特征相关的灰度图像信息的分块迭代函数系统分形描述方法,通过计算减摩织构物理特征的分形维数,并与差分盒维数(differential box-counting,DBC)方法计算得到的分形维数进行对比,验证PIFS方法的有效性。结果表明,与差分盒维数方法计算得到的分形维数相比,针对不同网纹织构和不同形状组合、截面尺寸以及深度的凹坑织构,PIFS方法计算得到的分形维数能够更为敏感和有效地反映减摩织构物理特征的变化。

The physical characteristics of the surface texture are the key factors that affect the tribological characteristics of the piston assembly-liner system.In order to accurately describe the physical characteristics of the anti-friction texture on the surface of the piston assembly-cylinder liner system,a machine vision approach for characterizing the anti-friction texture based on the curvelet transform and the partitioned iterated function system(PIFS)is proposed.According to the gray image information of the surface texture of cylinder liner,the curvelet transform is employed to extract the physical features of the multi-scale and anisotropic surface topography image of cylinder liner.A PIFS-based fractal method is studied to describe the physical features of the surface texture,and compared with the fractal dimension calculated by the differential box-counting(DBC)method to verify the effectiveness of PIFS method.The results indicate that the proposed approach can effectively characterize the physical features of surface texture for different cross-hatched lines and dimple textures with different shapes,cross-section sizes and depths.