无氧铜超精加工表面微观形貌的分形维数表征

单点金刚石超精密加工能够获得纳米级的低粗糙度表面。进一步的实验表明,采用该工艺进行退火态无氧铜切削,已加工表面在刀痕基础上还会出现清晰的晶界浮凸现象。传统的粗糙度概念无法有效表征与区分含有晶界浮凸信息的超精加工表面微观形貌。引入分形维数概念,采用该理论中尺码法对无氧铜超精加工表面的微观形貌进行分形维数计算;为降低切削刀痕信号干扰、突出晶界浮凸信息,设计表面信号带阻滤波方法。计算结果表明,超精加工后的表面分形维数包含了加工刀痕与晶界浮凸信息,由于两者尺度相近,传统的粗糙度测量无法区分其差异;采用带阻滤波与尺码法耦合方式,能够有效识别晶界浮凸特点,定量地反映微观尺度下超精加工表面的形貌特征信息。

Fractal Dimension Characterization on Surface Microtopography of Ultra-precision Machined Oxygen-free Copper

Nano-scale surface of low roughness can be obtained in single point diamond ultra-precision machining.Further ex-periments show that clear embossed grain boundary will appear on the machined surface filled with tool marks when annealed oxygen-free copper cut by single point diamond ultra-precision machining.Ultra-precision machined surface′s microtopography with em-bossed grain boundary can not be effectively characterized and distinguished with traditional concept of roughness.In this work,the concept of fractal dimension was introduced and yard stick method was used to calculate fractal dimension of surface microtopography of ultra-precision machined oxygen-free copper.In order to reduce interference of tool marks signal and extrude information of em-bossed grain boundary,band-stop filter method was designed.The results showed that the surface fractal dimension and embossed grain boundary could be obtained on the surface after ultra-precision machining,but due to the similar size scale,the difference could not be distinguished by traditional roughness measurement.By coupling band-stop filtering and yard stick method,the feature of em-bossed grain boundary could be effectively identified,and which could reflect the microscopic,characteristic information of ultra-pre-cision machined surface′s topography quantitatively.