Abstract: Surface property of material has a great impact on the interfacial adhesion of particle and surface.Rough surfaces were used for studying scale feature of above two indicators.It could conclude from the above study of scale feature of fractal indicators that there existed two regions when fractal indicators change with scale, which were named unstable fractal region and stable region.In the process of analysing the two-dimensional surface contour, we transfered the finding of critical point into solving the quantitative relationship of sampling length and angle α.By the quantitative relationship, angle α could be made 0 to obtain the critical sampling length.As long as the sample length is greater than the critical length, stable fractal region could be obtained, and then the stable fractal dimension could be calculated, which would not affected by the resolution of instrument.In this case the fractal dimension can reflect the inherent property of rough surface, which can be used as an accurate characterization of surface roughness.Through the analysis of cleaning mechanism of solid dirt, we find that surface roughness has a great impact on interfacial adhesion.The results show that adhesion force changes with surface roughness, Ra<0.4627μm, adhesion force decreases with the increase of surface roughness; 1.3461μm< Ra <2.9755μm, adhesion force increases gradually; Ra>3μm, adhesion force remains the same.Adhesion force also changes with fractal indicator, it changes the opposite trend with surface roughness.

Key words: surface, fractals, fouling, interface, adhesion

摘要： 设备材料的表面粗糙程度对污垢颗粒界面黏附力的影响较大。本文以设备材料粗糙表面为研究对象,考察了传统指标和分形指标的尺度独立性,发现分形指标随尺度的变化分为不稳定分形区和稳定分形区。通过对二维表面轮廓线的分析,将区域分隔临界点的求取转化为取样长度和夹角α值的定量关系求解,通过实验得出其定量关系,找出稳定分形区。采用原子力显微镜测颗粒在不同粗糙表面的黏附力,结合固体污垢清除机理分析,发现表面的粗糙程度对界面黏附力的影响较大。研究表明Ra<0.4627μm时,随着表面粗糙度增加,黏附力减小;1.3461μm< Ra <2.9755μm时,黏附力逐渐增大;Ra>3μm时,黏附力保持稳定。黏附力随着分形指标的变化而变化,其变化趋势与传统指标正好相反。随着分形维数的增大,黏附力先是保持稳定,后逐渐增大,随着加工工艺的改变,表面粗糙程度有个剧烈的变化,分维值锐减,后逐渐增大。

关键词: 表面, 结垢, 分形, 界面, 黏附