The use of the Fractal Dimension in Characterizing Paper Formation

摘要

Recent work (1) has demonstrated the limitation of the formation index in describing the quality of paper formation. The normalised formation index (NFI) gives a quantitative evaluation of the formation based on the mean and standard deviation of the basis weight. Although useful as a method of detecting the intensity and extent of basis weight defects within paper, the formation index does not give any indication of the spatial distribution of the defects. The mass variation in paper does have a spatial component, and the fractal dimension has been used to characterize this variation. It has been demonstrated that paper formation appears to have similar fractal characteristics to simple numerical simulation models, and that the fractal dimension can be used to differentiate between sheets with similar formation indices but different spatial basis weight distributions. In this paper, the fractal dimension has been used to characterize the spatial distribution of basis weight for a range of paper sheets prepared on the University of Melbourne (UoM) former as well as for some commercial office papers. The role of the sample area for investigation has been examined, as has the role of thresholding and image processing of the basis weight data.